JP3633103B2 - Four-wheel drive vehicle - Google Patents

Description

[0001]
The present invention relates to a four-wheel drive vehicle in which a rotational driving force of a main prime mover is transmitted to front wheels and rear wheels, and more particularly to a four-wheel drive vehicle in which drive force is transmitted by a fluid pressure transmission mechanism.
[0002]
[Prior art]
As this type of four-wheel drive vehicle, conventionally, as described in, for example, Japanese Patent Application Laid-Open No. 63-176734 and Japanese Patent Application Laid-Open No. 1-223030, a hydraulic pressure corresponding to the rotation speed is rotated. A first hydraulic pump constituted by, for example, a vane pump, a second hydraulic pump similarly constituted by a vane pump that rotates in conjunction with the rear wheel and generates hydraulic pressure according to the rotational speed, and the first and second 2. Description of the Related Art There has been proposed an oil passage having a configuration including an oil passage that communicates one discharge port and the other suction port of a hydraulic pump.
[0003]
[Problems to be solved by the invention]
However, since the conventional four-wheel drive vehicle uses a hydraulic power transmission device, the propeller shaft can be omitted to reduce the weight, secure a vehicle interior space, and reduce noise and vibration. However, when the vehicle is traveling at high speed, both the front and rear wheels rotate at a high speed, which increases the discharge flow rate of the hydraulic pump. This increases the piping resistance, which increases the drag resistance of the system and increases the pressure loss. Unsolved problem that oil temperature rises in the system and suction of hydraulic oil cannot catch up at the suction port of the second hydraulic pump, and cavitation is likely to occur due to abnormally low pressure. There is. Here, in order to reduce the piping resistance when the flow rate is increased, the diameter of the piping may be increased. However, there are limits to this in consideration of space and cost.
[0004]
In order to suppress such deterioration in fuel consumption during high speed driving, it is conceivable to make the second hydraulic pump have a variable capacity so that the flow rate reaches a peak at a certain vehicle speed or higher. In the conventional example, the vane pump is used as the second hydraulic pump. Since the suction port and the discharge port are reversed depending on the rotation direction of the swing shaft, one of the pair of flow paths communicating between the first hydraulic pump and the second hydraulic pump is, for example, When moving forward, it becomes the high pressure side, when moving backward, it becomes the low pressure side when moving forward, and when moving backward, it becomes the high pressure side, and the low pressure side and the high pressure side are reversed depending on the traveling direction of the vehicle. When the discharge amount is detected by differential pressure, it is necessary to provide differential pressure detection means on both of the pair of flow paths, and it is necessary to select them according to the traveling direction of the vehicle. During no-load operation where the rotational speeds of the cylinders are substantially equal and not transmitting the driving force, the differential pressure detection means provided on the high pressure side becomes resistant to the suction of the hydraulic pump, causing a new problem that cavitation is likely to occur. And become.
[0005]
In order to solve this new problem, the present applicant has applied a swash plate type variable displacement motor as a fluid pressure motor of the fluid pressure driving means on the driven shaft side, as previously described in Japanese Patent Application No. 6-262639. The swash plate of this swash plate type variable displacement motor is pivotally supported so that the inclination angle of each swash plate can swing in the stroke direction of each piston around a predetermined swing shaft, and the set position of the swing shaft is A stopper that can be set to be offset from the rotation axis of the cylinder block in a direction where the facing distance between the cylinder block and the swash plate is small, and that can contact the swash plate when the inclination angle of the swash plate reaches a predetermined maximum inclination angle. With this configuration, there is no need to electronically control the swash plate according to the vehicle speed, and the inclination angle of the swash plate is automatically adjusted with a simple structure, and the structure of the hydraulic motor is simplified and downsized. And improve reliability It has proposed a four-wheel drive vehicle that can be.
[0006]
However, even in this prior art, unless the capacities of the fluid pressure pump on the drive shaft side and the fluid pressure motor on the driven shaft side are set with high accuracy, the transmission torque characteristics to the driven shaft side with respect to the difference in the rotational speed between the front and rear sides There is a new problem in that variations occur and an optimal four-wheel drive state cannot be obtained, causing the driver to feel uncomfortable.
[0007]
Therefore, when manufacturing the fluid pressure pump on the drive shaft side and the fluid pressure motor on the driven shaft side, it is conceivable to set the capacities of the pump and motor with high precision. As a result, pumps and motors will rise.
[0008]
Even if the capacities of the fluid pressure pump on the drive shaft side and the fluid pressure motor on the driven shaft side are set with high accuracy, if a different-diameter tire is mounted on one of the drive wheel and the driven wheel, the transmission torque against the difference in the front and rear rotational speed The characteristics will change, and the driver will feel uncomfortable.
[0009]
Accordingly, the present invention has been made paying attention to the problems of the conventional example described above, and is a four-wheel vehicle capable of avoiding variations in the transmission torque characteristics to the driven shaft side with respect to the front-rear rotational speed difference with a simple device configuration. It aims to provide a driving car.
[0010]
[Means for Solving the Problems]
To achieve the above object, a four-wheel drive vehicle according to claim 1 includes a drive axle driven by a main prime mover, a fluid pressure pump that rotates in conjunction with the drive axle and discharges a working fluid, and a driven A fluid pressure motor that rotates in conjunction with an axle; a first channel that communicates a discharge port of the fluid pressure pump and a suction port of the fluid pressure motor; a suction port of the fluid pressure pump and the fluid pressure motor; In a four-wheel drive vehicle having a second flow path communicating with the discharge port, a pressure detection means for detecting a fluid pressure in the first flow path, and a travel state detection for detecting a travel state of the vehicle And a motor capacity control processing means for changing and controlling the capacity of the fluid pressure motor, the motor capacity control processing means being applied to the drive axle and the driven axle based on a travel state detection value of the travel state detection means. If there is no rotational speed difference The control process as well as the start, when the pressure detection value of the pressure detecting means is a predetermined value or more, theOnce, the capacity of the fluid pressure motor is suddenly increased so that the capacity value exceeds the optimum capacity, and then the capacity value is gradually decreased to reach the optimum capacity.When the pressure detection value of the pressure detecting means is less than a predetermined value, the fluid pressure motor is changed so that the capacity is reduced to an optimum capacity.I am doing so.
[0012]
Also,The invention according to claim 2 is the four-wheel drive vehicle according to claim 1,The traveling state detecting means is constituted by a vehicle speed detecting means for detecting a vehicle speed, and the motor capacity control means is configured to detect the fluid pressure motor when the vehicle speed detection value of the vehicle speed detecting means is traveling in a predetermined low speed state. The capacity control of was started.
[0013]
Also,Claim 3The invention ofClaim 2In the four-wheel drive vehicle, the running state detecting means includes a steering angle detecting means for detecting a steering angle, and the motor capacity control means is configured such that when the detected value of the steering angle of the steering angle detecting means is zero, The capacity control of the fluid pressure motor was started.
[0014]
further,Claim 4The invention ofClaim 3In the four-wheel drive vehicle, the traveling state detection means includes an accelerator depression detection means for detecting whether or not the accelerator pedal is depressed, and the motor capacity control means depresses the accelerator pedal by the accelerator depression detection means. When it is determined that there is no, the capacity control of the fluid pressure motor is started.
[0015]
【The invention's effect】
According to the four-wheel drive vehicle of the first aspect, the motor capacity control processing means starts the control process when there is no rotational speed difference between the driving axle and the driven axle based on the running state detection value of the running state detection means. In addition, when the pressure detection value of the pressure detection means for detecting the pressure in the first flow path is equal to or greater than a predetermined value, the capacity of the fluid pressure motor is increased, and the pressure detection value of the pressure detection means is When the fluid pressure motor is less than the predetermined value, the capacity of the fluid pressure motor is reduced and changed to the optimum capacity, so even if the currently installed fluid pressure motor is not set with high accuracy, The motor capacity control processing means controls the change to the optimum motor capacity. As a result, the variation in the drive torque characteristic toward the driven wheel with respect to the difference in rotational speed between the front and rear wheels of the vehicle is reliably prevented, and the optimum four-wheel drive traveling can be provided.
[0016]
Further, according to the present invention, even if the capacity of the fluid pressure pump is not set with high accuracy, the motor capacity control process can obtain the optimum characteristic of the driving torque to the rear wheel side with respect to the difference in the rotational speed of the front and rear wheels. Therefore, it is not necessary to set the capacity of the fluid pressure pump and the fluid pressure motor with high accuracy in the manufacturing stage, and the fluid pressure pump and the fluid pressure motor can be manufactured at low cost.
[0017]
In the present invention, since the start time of the motor capacity control process is determined based on the pressure detection value of the pressure detection means that detects the pressure in the first flow path, the device configuration is simplified. be able to.
[0018]
Further, when a tire of a different diameter is mounted on one of the driving wheel or the driven wheel, the capacity of one of the fluid pressure pump and the fluid pressure motor changes. By performing the motor capacity control process, the rotation of the front and rear wheels is changed. Because the characteristic of the driving torque to the rear wheel side against the number difference is always corrected to the optimum value,normalFour-wheel drive traveling can be obtained.
[0019]
Furthermore, in the present invention,When the pressure detection value of the pressure detection means is equal to or greater than a predetermined value, the motor capacity control processing means temporarily increases the capacity of the fluid pressure motor so that the capacity value exceeds the optimum capacity. Since the capacity value is gradually decreased so as to reach the optimum capacity, the optimum capacity can be set in a short time, and the stability of the motor capacity control can be improved.
[0020]
Also,Claim 2The invention ofClaim 1The motor capacity control means can control the capacity of the fluid pressure motor when the vehicle speed detection value of the vehicle speed detection means is traveling in a predetermined low speed state. Since it starts, the fluid pressure motor can be set to the optimum capacity in the initial stage of vehicle travel.
[0021]
Also,Claim 3The invention ofClaim 2The motor capacity control means confirms that the detected value of the steering angle of the steering angle detection means is zero, that is, confirms that the vehicle is traveling straight ahead. Since the capacity control of the fluid pressure motor is started from the above, a motor capacity control process in a state where a rotational speed difference occurs between the front and rear wheels when the vehicle turns and the discharge flow rate of one of the fluid pressure pump and the fluid pressure motor is increased. Can be avoided, and the motor capacity control process can be performed with higher accuracy.
[0022]
further,Claim 4The invention ofClaim 3Since the motor capacity control means starts the capacity control of the fluid pressure motor when it is determined that the accelerator pedal is not depressed by the accelerator depression detection means, It is possible to avoid the motor capacity control process in a state where the discharge flow rate of the fluid pressure pump is increased, and the motor capacity control process can be performed with higher accuracy.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic configuration diagram showing a first embodiment when the present invention is applied to a four-wheel drive vehicle based on a front wheel drive vehicle. In the figure, reference numeral 1 denotes an engine as a main prime mover. The rotational driving force of the engine 1 is input to a front wheel side differential 3 via a transmission 2, and a drive axle is provided on the output side of the differential 3. A front wheel 5 is connected via a front axle 4.
[0024]
In the front wheel side differential device 3, a ring gear 3 b formed in a differential gear case 3 a meshes with a gear 2 a connected to the output side of the transmission 2 and is driven to rotate. A pair of pinion shafts 3c formed in the differential gear case 3a is attached with pinions 3d. The pair of side gears 3e are engaged with the pinions 3d, and the front axle 4 is connected to the side gears 3e.
[0025]
Further, a second ring gear 3f is formed in the differential gear case 3a in parallel with the ring gear 3b. The second ring gear 3f is connected to a rotary shaft 6a of a suction throttle type piston pump 6 as a fluid pressure pump constituting a driving side fluid pressure driving means via a gear 3g meshing with the second ring gear 3f.
[0026]
The suction port 6b of the suction throttle type piston pump 6 is connected to a strainer 7a disposed in the reservoir tank 7, and through a low-pressure pipe 8L serving as a second flow path, an electromagnetic direction switching for forward / reverse switching. It is connected to the tank port T of the valve 9. The discharge port 6c of the suction throttle piston pump 6 is connected to the pump port P of the electromagnetic direction switching valve 9 for forward / reverse switching through a high-pressure pipe 8H serving as a first flow path.
[0027]
Further, a pressure switch 20 as a pressure detecting means is inserted in the high pressure pipe 8H connected to the discharge port 6c of the suction throttle type piston pump 6. When the pressure of the high pressure pipe 8H exceeds a predetermined reference pressure Ps, the pressure switch 20 is an input interface circuit 130a of the controller 130 described later.₁ON signal SP_ONIs output.
[0028]
On the other hand, in the electromagnetic directional control valve 9 for forward / reverse switching described above, the input / output port A is connected to an inflow port 10a of a free swash plate type variable capacity motor 10 as a fluid pressure motor, which will be described later, and the input / output port B is free-slanted. It is connected to the outflow port 10 b of the plate type variable capacity motor 10. The pump port P is connected to the input / output port A and the tank port T is connected to the input / output port B at the normal position where the solenoid 9a is in a non-energized state, and the pump port P is connected at the offset position where the solenoid 9a is in an energized state. The tank port T and the input / output port A are communicated with the input / output port B, respectively.
[0029]
That is, in the normal position, the high pressure oil in the high pressure pipe 8H is communicated with the inflow port 10a of the swash plate type variable displacement motor 10 and the low pressure pipe 8L is communicated with the outflow port 10b to rotate the rotary shaft 10c in the rotational direction during forward travel. Conversely, at the offset position, the high pressure oil in the high pressure pipe 8H is communicated with the outflow port 10a (inflow port at the time of forward movement) and the low pressure pipe 8L is communicated with the inflow port 10b (outflow port at the time of forward movement). Is driven to rotate in the direction of rotation during reverse travel.
[0030]
The electromagnetic directional switching valve 9 is built in the swash plate type variable displacement motor 10, and the output ports A and B are connected to the inflow / outflow ports 10a and 10b of the variable displacement motor 10 without any piping.
[0031]
In addition, the energization of the solenoid 9a of the electromagnetic direction switching valve 9 is connected to the DC power supply 9c via the shift position detection switch 9b which is turned on only when the solenoid 9a is selected to reverse by a shift lever (not shown). As a result, the vehicle is controlled to be in a non-energized state during forward travel, and to an energized state during reverse travel.
[0032]
Further, a relief valve 11 for determining an upper limit of the discharge pressure of the piston pump 6 as a torque limiting means is interposed between the suction port 6b and the discharge port 6c of the suction throttle type piston pump 6. The high-pressure pipe 8H and the low-pressure pipe 8L between the piston pump 6 and the electromagnetic switching valve 9 are communicated with each other by a communication pipe 12, and the low-pressure pipe 8L side to the high-pressure pipe 8H side with respect to the communication pipe 12 is connected. A check valve 13 that allows the flow of the fluid is interposed, and a fixed orifice 15 is arranged in parallel with the check valve 13 with respect to the second communication pipe 14 arranged in parallel with the communication pipe 12. Is connected.
[0033]
As shown in FIGS. 2 and 3, the free swash plate type variable displacement motor 10 has a rotary shaft 10 c rotatably supported on the pump housing 100. A cylindrical cylinder block 101 is serrated and fitted coaxially at a position in the housing 100 of the rotating shaft 10c. In the cylinder block 101, an odd number, for example, seven pistons 102 are arranged at equal intervals along the rotation direction of the cylinder block 101. Each piston 102 is supported by a cylinder block 101 so as to be slidable in a direction parallel to its axial direction.
[0034]
A swash plate 103 is disposed at a position facing the right end surface of the cylinder block 101 in the housing 100. The swash plate 103 includes a disc portion 103 a and a protruding portion 103 b that protrudes upward from the upper end thereof, and an inclination angle of the swash plate 103 is freely swingable about a predetermined swing shaft 104. The swinging shaft 104 is disposed so as to be offset by a predetermined amount ε in the direction in which the swash plate 103 approaches the facing surface of the cylinder block 101 with respect to the central axis 105 of the rotating shaft 10c, that is, upward in FIG.
[0035]
Further, a shoe 108 crowned on the right end of the piston 102 is brought into sliding contact with the swash plate 103 on the surface of the disk portion 103 a facing the cylinder block 101 by a shoe holder 109, and the shoe holder 109 is attached to the cylinder block 101. It is pressed to the swash plate 103 side via a needle 111 by a pressing spring 110 disposed on the inner peripheral surface.
[0036]
Therefore, external force is transmitted from the piston 102 to the swash plate 103, but on the lower side when viewed from the swing shaft 104 of the swash plate 103, it acts around the swing shaft by the force transmitted from the piston to the swash plate. Compared with the case where the swing shaft 104 and the central shaft 105 are matched, the moment becomes a larger value as the moment arm becomes longer by the amount corresponding to the eccentricity ε, and on the other hand, the upper side as viewed from the swing shaft 104. On the other hand, the moment acting around the swing axis becomes a small value as the arm of the moment is shortened by the amount corresponding to the eccentricity ε. The side 103 is inclined so as to approach the cylinder block 101.
[0037]
The tilt angle of the swash plate 103 increases as the external force transmitted to the swash plate by each piston increases, and the discharge amount as a fluid pressure motor increases. The external force transmitted from the piston 102 to the swash plate 103 is proportional to the pressure of the fluid pressure chamber of the piston, that is, the working fluid pressure of the difference between the discharge amount of the piston pump 6 supplied to the motor and the suction amount of the motor. Therefore, when the working fluid pressure increases, the tilt angle of the swash plate 103 automatically increases in accordance with this increase.
[0038]
Further, the swash plate 103 is urged by the urging mechanism 113 in a direction in which the tilt angle becomes smaller. The urging mechanism 113 is in contact with the left end surface of the protruding portion 103b of the swash plate 103, and presses the protruding portion 103b of the swash plate 103 in the right direction, that is, in a direction to reduce the tilt angle of the swash plate 103. A cylinder device having a piston 113a, a coil spring 113c disposed in the fluid pressure chamber 113b of the cylinder device and biasing the control piston 113a toward the swash plate 103, and a fluid pressure chamber 113b in the swash plate type variable displacement motor 10 The communication pipe 113d is connected to the low-pressure portion, for example, the low-pressure pipe 8L side, and is opened to the atmosphere, and the orifice 113e interposed in the middle of the communication pipe 113d.
[0039]
On the other hand, the maximum tilt angle of the swash plate 103 is restricted to the lower end side of the swash plate 103 opposite to the protruding portion 103b, and the capacity q of the swash plate type variable displacement motor 10 is controlled._MA capacity regulating mechanism 115 as a capacity regulating means for regulating the above is disposed.
[0040]
The capacity regulating mechanism 115 is screwed into the screw shaft 117 and a step motor 116 configured by, for example, a stepping motor built in the pump housing 100, a screw shaft 117 connected to the rotation shaft of the step motor 116. A ball nut 118 that is non-rotatably guided by the guide member, a locking piece 119 that protrudes from the ball nut 118 and contacts the right end of the disc portion 103a of the swash plate 103, and a ball nut 118 And stoppers 120L and 120S for regulating the large capacity position and the small capacity position.
[0041]
Further, a valve plate 121 fixed to the housing 100 is slidably contacted with the left end surface of the cylinder block 101, and a communication hole 123 is formed between the valve plate 121 and a bore 122 that accommodates each piston 102. . As shown in FIG. 3, the valve plate 121 has an inflow port 10a (backward outflow port) on the left half along the movement path of the communication hole 123, and an outflow port 10b (backward inflow port) on the right half. Is formed.
[0042]
Here, in the piston pump 6 described above, the suction port 6b and the discharge port 6c are not interchanged depending on the rotation direction of the rotating shaft 6a, and the discharge flow rate is indicated by the solid line S in FIG.₁As shown by, vehicle speed from “0” to vehicle speed V₁Until the vehicle speed reaches V, the vehicle speed increases at a relatively large rate in proportion to the increase in vehicle speed.₁Above, maximum discharge flow rate Q_maxIt has a flow characteristic that saturates at. The specific discharge amount of the swash plate type variable displacement motor 10 in a state where the ball nut 118 of the capacity regulating mechanism 115 is moved to the stopper 120L is set to be larger than the specific discharge amount of the piston pump 6. ing.
[0043]
On the other hand, a gear 16 is attached to the rotary shaft 10c of the swash plate type variable capacity motor 10, and a ring gear 17b formed in a differential gear case 17a of the rear wheel side differential 17 is meshed with the gear 16. The rear wheel side differential device 17 has substantially the same configuration as that of the front wheel side differential device 3 described above, and a pair of pinion shafts 17c is formed in the differential gear case 17a and is attached to the pair of pinion shafts 17c. A pair of side gears 17e is meshed with the pinion 17d. A rear axle 18 is connected to the side gears 17e, and a rear wheel 19 is connected to the rear axle 18.
[0044]
The step motor 116 of the capacity regulating mechanism 115 is driven and controlled by the controller 130.
As shown in FIG. 4, the controller 130 includes a microcomputer 130a and a drive circuit 130b. The microcomputer 130a has an input interface circuit 130a having an A / D conversion function.₁And an arithmetic processing unit 130a that performs arithmetic processing for controlling the step motor 116 in accordance with a predetermined program.₂And a storage device 130a such as a ROM or a RAM.₃And an output interface circuit 130a that outputs a control signal CS.₄And.
[0045]
The input interface circuit 130a₁Is connected to the pressure switch 20, the steering angle sensor 22 as the steering angle detection means, the vehicle speed sensor 24 as the vehicle speed detection means, and the accelerator switch 26 as the accelerator depression detection means, and the pressure of the high pressure pipe 8H is the reference. ON signal SP from pressure switch 20 when pressure Ps is exceeded_ONIs inputted, an angle (steering steering angle) α by which a steering wheel (not shown) is steered is inputted from the steering angle sensor 22, and a vehicle speed detection value V using the wheel speed on the rear wheel side as a driven wheel as the vehicle speed is a vehicle speed. The accelerator ON signal SA is input from the accelerator switch 26 when the accelerator 24 is depressed and input from the sensor 24._ONIs entered.
[0046]
Here, the reference pressure Ps of the pressure switch 20 is determined so that the vehicle equipped with the piston pump 6 and the swash plate type variable displacement motor 10 with the capacity set with high accuracy travels straight with the steering angle set to “0”. Release the pedal and release the predetermined first reference vehicle speed V_S1To second reference vehicle speed V_S2(V_S1<V_S2) Is set to the same value as the pressure value in the high-pressure pipe 8H when the inertial running state is performed at a constant speed in the range.
[0047]
As a result, the pressure switch 20 turns ON signal SP._ONIs output (the pressure switch 20 is in an ON state), the pressure value in the high-pressure pipe 8H is low because the capacity of the swash plate type variable displacement motor 10 currently mounted is small or the capacity of the piston pump 6 is large. Can exceed the reference pressure Ps. On the contrary, the pressure switch 20 is turned ON signal SP._ONIs not output (the pressure switch 20 is OFF), because the capacity of the swash plate type variable displacement motor 10 currently mounted is too large or the capacity of the piston pump 6 is small, It can be determined that the pressure value is lower than the reference pressure Ps.
[0048]
Further, the drive circuit 130b described above generates the normal rotation drive pulse CS according to the control signal CS output from the microcomputer 130a._POr reverse drive pulse CS_NIs output to the step motor 116. The forward drive pulse CS_PIs output to the step motor 116, the ball nut 118 moves to the stopper 120S side, and the capacity of the swash plate type variable displacement motor 10 decreases. Further, the reverse drive pulse CS_NIs output to the step motor 116, the ball nut 118 moves to the stopper 120L side, and the capacity of the swash plate type variable displacement motor 10 increases.
[0049]
Next, the operation of the above embodiment will be described with reference to the flowcharts of FIGS.
This control process is executed as a timer interruption process for every predetermined time (for example, 10 msec) while the engine 1 is rotating, that is, when the ignition switch is on. First, the vehicle speed sensor 24 detects in step S1. The vehicle speed detection value V is read, then the process proceeds to step S2, and the angle (steering steering angle) α detected by the steering angle sensor 22 is read.
[0050]
Next, the process proceeds to step S3, and it is determined whether or not the process completion flag FC indicating that the motor capacity control process is completed is reset to “1” (indicating that the motor capacity control process is completed). When the process completion flag FC is reset to “1”, the timer interrupt process is terminated, while the process completion flag FC is reset to “0” (the motor capacity control process is not performed). If YES, the process proceeds to step S4.
[0051]
In step S4, the vehicle speed detection value V is set to the first reference vehicle speed V._S1It is determined whether or not the vehicle speed exceeds the first reference vehicle speed V._S1When the vehicle speed exceeds the value, the process proceeds to step S5. On the other hand, the vehicle speed detection value V is equal to the first reference vehicle speed V._S1When it is below, it is determined that the motor capacity control process is not being performed, and the timer interrupt process is terminated.
[0052]
In step S5, the vehicle speed detection value V is set to the second reference vehicle speed V._S2Whether the vehicle speed detection value V is less than the second reference vehicle speed V_S2When the vehicle speed is lower than the value, the process proceeds to step S6. On the other hand, the vehicle speed detection value V is equal to the second reference vehicle speed V._S2As described above, it is determined that the motor capacity control process is not being performed, and the timer interrupt process is terminated.
[0053]
In step S6, it is determined whether or not the steering angle α is “0”. When the steering angle α is “0”, the process proceeds to step S7, while the steering angle α is “0”. If any other value is indicated, it is determined that the motor capacity control process is not being performed, and the timer interrupt process is terminated.
[0054]
In step S7, it is determined whether or not the accelerator switch 26 is in an ON state by depressing the accelerator pedal. When the accelerator switch 26 is in an ON state, it is determined that the motor capacity control process is not being performed. When the timer interrupt process is finished and the accelerator switch 26 is in the OFF state, the process proceeds to step S8.
[0055]
In step S8, the motor capacity control process shown in FIG. 6 is executed, and then the timer interrupt process is terminated.
In the motor capacity control process of FIG. 6, it is determined whether or not the pressure switch 20 is in the ON state in Step S10. If the pressure switch 20 is in the ON state, the process proceeds to Step S11. Migrate to
[0056]
In step S11, it is determined whether or not the capacity reduction process flag FS indicating that the motor capacity has been reduced to a predetermined capacity is reset to “1” (indicating that the capacity reduction process has been completed). When the capacity reduction process flag FS is reset to “1”, the process proceeds to step S13. On the other hand, the capacity reduction process flag FS is set to “0” (indicating that the capacity reduction process is not performed). If yes, the process proceeds to step S14.
[0057]
In step S13, the first correction reverse rotation drive pulse CS set to a small value so as to slightly move the ball nut 118 to the stopper 120L side._N1Is output to the step motor 116 as a reverse drive pulse. Then, the process proceeds to step S15, the process completion flag FC is set to “1”, and the timer interrupt process is terminated.
[0058]
Further, since the capacity reduction processing flag FS is set to “0”, when the process proceeds to step S14, in this step S14, the ball nut 118 is set to a large value for greatly moving to the stopper 120L side. 2 reverse rotation drive pulse CS for correction_N2(CS_N2≫CS_N1) To the step motor 116 as a reverse drive pulse. Then, the timer interrupt process is terminated.
[0059]
On the other hand, in step S12 which is shifted when the pressure switch 20 is in the OFF state in step S10, the capacity reduction processing flag FS is set to “1”. Next, the process proceeds to step S16, and the correction normal rotation drive pulse CS for moving the ball nut 118 to the stopper 120S side._PIs input as a normal rotation drive pulse, and then the timer interrupt process is terminated.
[0060]
Here, the capacity regulation mechanism 115, the controller 130, and the control processes of FIGS. 5 and 6 correspond to the motor capacity control processing means of the present invention.
Next, vehicle operation based on the above configuration will be described.
[0061]
Now, when the vehicle is stopped on a high friction coefficient road such as a dry road surface and an ignition switch (not shown) is in an off state and the engine is started with the ignition switch on, the ignition switch is on. As a result, the controller 130 is turned on to initialize the processing completion flag FC and the capacity reduction processing flag FS to “0”. At the same time, the step motor 116 is driven to stop the ball nut 118 as a stopper. Move to a position close to the 120L side.
[0062]
When the engine 1 starts to travel forward from a braking state in which the engine 1 is idling, a startable state can be achieved by switching a shift lever (not shown) to the forward traveling state. At this time, since the shift position detection switch 9b on the reverse travel side maintains the OFF state, the solenoid 9a of the electromagnetic direction switching valve 9 for forward / reverse switching maintains the non-energized state, and the switching position is the normal position shown in FIG. Hold.
[0063]
In this state, when the brake pedal is released and the accelerator pedal is depressed, the rotational force of the engine 1 is transmitted to the front wheel side differential 3 via the transmission 2, and the front wheel 5 is moved by the front wheel side differential 3. Drive forward of the vehicle is started by rotationally driving in the forward direction.
[0064]
Then, when the rotary shaft 6a of the suction throttle type piston pump 6 is rotationally driven, the hydraulic oil having a discharge flow rate corresponding to the rotational speed is discharged from the piston pump 6. The discharged hydraulic oil is supplied to the inflow port 10a of the swash plate type variable displacement motor 10 through the high-pressure pipe 8H and the electromagnetic switching valve 9 for forward / reverse switching. , And the rotational shaft 10c of the swash plate type variable displacement motor 10 is rotated via the rear wheel side differential device 17, whereby hydraulic oil is drawn from the inflow port 10a. Discharged.
[0065]
At this time, when the process of FIG. 5 is executed, the process completion flag FC is reset to “0” by initialization, so the process proceeds to step S4. However, since the vehicle has just started, the process is read in step S1. The vehicle speed detection value V is the first reference vehicle speed V_S1The timer interrupt process is terminated as it is from step S4.
[0066]
At this time, the maximum discharge amount Q per unit time in the swash plate type variable displacement motor 10_MIs the maximum specific discharge amount when the swash plate 103 is close to the maximum tilt angle, and Q is the rotational speed of the rotary shaft 10c, that is, the rotational speed of the driven axle._RThen, Q × N_RAnd increases in proportion to the rotational speed of the driven axle.
[0067]
On the other hand, the discharge amount from the piston pump 6, that is, the inflow flow rate Q supplied to the swash plate type variable displacement motor 10._P, The speed of the rotary shaft 6a, that is, the rotational speed N of the drive axle._FThe amount is proportional to Here, the specific discharge amount Q of the swash plate type variable displacement motor 10_MMAXIs the specific discharge amount Q of the piston pump 6_PMAXSince the front wheel 5 and the rear wheel 19 are rotating at substantially the same number of rotations, Q_P<Q_M(= V × N_R) Accordingly, since the swash plate 103 has an inclination angle smaller than the maximum inclination angle, the lower right portion of the swash plate 103 does not come into contact with the locking piece 119 formed on the ball nut 118, and either in the clockwise direction or in the counterclockwise direction. It is in a swingable state.
[0068]
Accordingly, the swash plate 103 is automatically adjusted to a slope corresponding to the flow rate of the supplied hydraulic oil, and the swash plate type variable displacement motor 10 discharges substantially the same amount as the inflow flow rate supplied from the piston pump 6. As a result, the pressure of the high-pressure pipe 8H is maintained at substantially zero without increasing, and the swash plate type variable displacement motor 10 does not transmit drive torque to the driven axle 18, that is, the rear wheel 19. Therefore, the vehicle travels forward in the same state as the front wheel drive vehicle (two wheel drive vehicle).
[0069]
Thereafter, the vehicle speed is increased and the vehicle speed detection value V becomes the first reference vehicle speed V._S1To 1st reference vehicle speed V_S2When the steering angle α is other than “0”, the timer interruption process is terminated from step S6 of the process of FIG. 5 or when the accelerator pedal is depressed, the timer from step S7 is started. End the interrupt process.
[0070]
When the accelerator pedal is released after a predetermined time and coasting is maintained, the vehicle speed V becomes the first reference vehicle speed V._S1And second reference vehicle speed V_S2At this point, the process proceeds from step S3 in FIG. 5 to step S6 via steps S4 and S5. Since the steering angle α is “0” by maintaining the straight traveling, the routine proceeds from step S6 to step S7, where the depression of the accelerator pedal is released and the accelerator ON signal SA is released._ONIs not input, the process proceeds to step S8, and the motor capacity control process shown in FIG. 6 is performed.
[0071]
Here, as shown in FIG.₁Motor capacity q of the swash plate type variable capacity motor 10 at_MLIs the optimal motor capacity range q_MBWhen the pressure switch 20 is greatly below the pressure switch 20, the pressure switch 20 is turned on by the pressure increase in the high-pressure pipe 8H._ONTherefore, the process proceeds from step S10 to step S11 in the process of FIG. Since the capacity reduction process flag FS is set to “0”, the process proceeds to step S14 and the second correction reverse rotation drive pulse CS._N2Is output to the step motor 116. As a result, the ball nut 118 moves greatly toward the stopper 120L, and the capacity of the swash plate type variable capacity motor 10 increases.
[0072]
Thereafter, time t in FIG.₂Motor capacity q_M1Is the optimal motor capacity range q_MBIf the pressure is slightly exceeded, the pressure in the high-pressure pipe 8H does not increase, and the pressure switch 20 is turned off. Therefore, the process proceeds from step S10 to step S12 in FIG. 6, and the capacity reduction processing flag FS is set to “1”. . Then, the process proceeds to step S16, and the normal rotation drive pulse CS for correction_PIs output to the step motor 116. Thereby, since the ball nut 118 moves to the stopper 120S side, the capacity of the swash plate type variable capacity motor 10 decreases.
[0073]
Thereafter, time t in FIG.₃Motor capacity q_M2Is the optimal motor capacity range q_MBIf the pressure switch 20 is slightly below, the pressure switch 20 is turned on by the pressure increase in the high-pressure pipe 8H._ONTherefore, the process proceeds from step S10 to step S11 in the process of FIG. Since the capacity reduction processing flag FS is set to “1”, the process proceeds to step S13 and the first correction reverse rotation drive pulse CS._N2Is output to the step motor 116. As a result, the ball nut 118 slightly moves toward the stopper 120L, so that the capacity of the swash plate type variable capacity motor 10 increases by a small amount. As a result, time t in FIG.₄The motor capacity of the swash plate type variable capacity motor 10 is the optimum motor capacity range q_MBSet in.
[0074]
Then, by proceeding to step S15 and setting the process completion flag FC to “1”, the process does not proceed to step S4 in step S3 of the process of FIG. 5, and the motor capacity control process from the next time is not performed.
[0075]
Also, as shown in FIG.₅Motor capacity q of the swash plate type variable capacity motor 10 at_MHIs the optimal motor capacity range q_MBIf the pressure switch 20 is greatly exceeded, the pressure switch 20 is turned off due to the pressure drop in the high-pressure pipe 8H. Therefore, the process proceeds from step S10 to step S12 in FIG. 6, and the capacity reduction process flag FS is set to “1”. Set to. Then, the process proceeds to step S16, and the normal rotation drive pulse CS for correction_PIs output to the step motor 116. Thereby, since the ball nut 118 moves to the stopper 120S side, the capacity of the swash plate type variable capacity motor 10 decreases.
[0076]
Thereafter, time t in FIG.₆Motor capacity q_M3Is the optimal motor capacity range q_MBIf the pressure is slightly higher, the pressure switch 20 is turned off due to the pressure drop in the high-pressure pipe 8H, so the process proceeds from step S10 to step S12 in the process of FIG. Pulse CS_PIs output to the step motor 116, the ball nut 118 is moved to the stopper 120S side, and the capacity of the swash plate type variable capacity motor 10 is decreased.
[0077]
And time t in FIG.₇Motor capacity q_M4Is the optimal motor capacity range q_MBIf the pressure switch 20 is slightly below, the pressure switch 20 is turned on by the pressure increase in the high-pressure pipe 8H._ONTherefore, the process proceeds from step S10 to step S11 in the process of FIG. Since the capacity reduction processing flag FS is set to “1”, the process proceeds to step S13 and the first correction reverse rotation drive pulse CS._N2Is output to the step motor 116. As a result, the ball nut 118 slightly moves toward the stopper 120L, so that the capacity of the swash plate type variable capacity motor 10 increases by a small amount. As a result, time t in FIG.₈Motor capacity is the optimal motor capacity range q_MBSet in.
[0078]
Then, by proceeding to step S15 and setting the process completion flag FC to “1”, the process does not proceed to step S4 in step S3 of the process of FIG. 5, and the motor capacity control process from the next time is not performed.
[0079]
As described above, the capacity of the swash plate type variable displacement motor 10 currently installed is not set with high accuracy, and has a small motor capacity as shown in FIG. 8 or a large motor capacity as shown in FIG. However, the vehicle maintains a straight running, and after a predetermined time, the accelerator pedal is released and the coasting is carried out. The vehicle speed V is the first reference vehicle speed V._S1And second reference vehicle speed V_S2When the motor capacity control process described above is performed based on the pressure of the high-pressure pipe 8H, the broken line S shown in FIG.₂As shown by the flow characteristics of the piston pump 6 (solid line S₁) Can be set to the optimum motor capacity.
[0080]
When the vehicle starts on a low friction coefficient road such as an icy road or a snowfall road, the front wheel 5 is first rotationally driven as described above. However, since the front wheel 5 is a low friction coefficient road, By slipping, the rotational speed N of the front wheel 5_FIs the rotational speed N of the rear wheel 19_RTherefore, a predetermined rotational speed difference is generated between the front wheel 5 and the rear wheel 19.
[0081]
Thus, as the slippage of the front wheel 5 increases, the discharge amount per unit time of the piston pump 6 relatively increases, and the same discharge amount is obtained on the swash plate type variable displacement motor 10 side that is set to an optimum capacity following the increase. Is automatically adjusted in a direction in which the tilt angle of the swash plate 103 is increased.
[0082]
That is, for example, the rear wheel speed is the wheel speed V shown in FIG._R1The front wheel speed V_FIs the rear wheel speed V_R1Is a broken line S in FIG.₂As shown by the characteristics, the discharge flow rate Q of the swash plate type variable displacement motor 10 set to the optimum capacity is shown._MAnd the discharge flow rate Q discharged from the piston pump 6_PDischarge flow rate Q₁However, the front wheel speed V_FIs the rear wheel speed V_R1When the flow rate increases, the discharge flow rate Q of the piston pump 6 is increased accordingly._PIs the solid line S in FIG.₁Increase as shown in
[0083]
Thus, the discharge flow rate Q of the piston pump 6_PIs increased, the swash plate 103 of the swash plate type variable displacement motor 10 is tilted to the maximum tilt angle side, and the discharge flow rate Q of the swash plate type variable displacement motor 10 is increased._MIs an alternate long and short dash line S in FIG.₃The wheel speed V_R1Discharge flow rate Q_M1Increase to. And the maximum discharge flow rate Q_M1Is reached, the lower right portion of the swash plate 103 of the swash plate type variable displacement motor 10 comes into contact with the locking piece 119 of the ball nut 118, so that the tilt angle of the swash plate type variable displacement motor 10 is fixed near the maximum tilt angle. Is done.
[0084]
Further, the front wheel side wheel speed V due to the front wheel side slip._FIncreases and the maximum discharge flow rate Q on the rear wheel side_M1Wheel speed V that matches_F1For example, wheel speed V_F2Then, the discharge flow rate Q of the piston pump 6_P2Is the discharge flow rate Q of the swash plate type variable displacement motor 10_M1Therefore, the resistance of the swash plate type variable displacement motor 10 becomes a load and the hydraulic pressure of the high pressure pipe 8H increases.
[0085]
Therefore, as shown in FIG. 7, the swash plate type variable displacement motor 10 generates a drive torque in accordance with the supply pressure from the high pressure pipe 8H and transmits it to the rear wheel 19 via the rear wheel side differential device 17. The vehicle travels forward in the same state as a four-wheel drive vehicle.
[0086]
That is, the driving torque transmitted to the rear wheel side is indicated by a solid line L in FIG.₁As shown in FIG. 5, the maximum output torque T is generated only when a predetermined rotational speed difference occurs between the front and rear wheels, and increases rapidly with an increase in the rotational speed difference between the front and rear wheels._MAXTherefore, the vehicle can travel forward in an optimal four-wheel drive state without causing the driver to feel uncomfortable.
[0087]
Next, when the vehicle is moved backward, the shift position detection switch 9b is turned on by switching the shift lever to the reverse position, so that the solenoid 9a of the electromagnetic switching valve 9 for forward / reverse switching is energized, The switching position is switched from the normal position to the offset position, whereby the hydraulic oil in the high pressure pipe 8H is supplied to the reverse flow inflow port 10b of the swash plate type variable displacement motor 10 and the hydraulic oil discharged from the reverse flow outflow port 10a flows. By returning to the low-pressure pipe 8L side through the path 12, the rotating shaft 10c of the swash plate type variable displacement motor 10 is reversely rotated from the forward travel, and the rear wheel 19 is rotated in reverse. For this reason, even when the vehicle is moving backward, the driving force is transmitted in exactly the same way as when moving forward, and pressure is generated in the high-pressure pipe 8H only when the front wheel 5 slips and a predetermined rotational speed difference occurs between the front and rear wheels. Torque is transmitted to the rear wheel 19.
[0088]
Therefore, the four-wheel drive vehicle of the present embodiment has a motor based on the pressure of the high-pressure pipe 8H in the initial stage of vehicle travel, even if the capacity of the currently mounted swash plate type variable displacement motor 10 is not set with high accuracy. By performing capacity control processing, it is possible to set the optimal motor capacity, so it is possible to reliably avoid variations in the characteristics of the drive torque to the rear wheel side with respect to the difference in the rotation speed of the front and rear wheels, and to perform optimal four-wheel drive traveling Can be obtained.
[0089]
In addition, the motor capacity control processing is performed when the motor capacity is too small.₁When the motor capacity is once set to a large value as in the control indicated by₂As shown by the optimal motor capacity range q_MBA slightly larger value, at time t₃As shown in the control, the optimal motor capacity range q_MBBy making the final volume adjustment after making it slightly smaller, time t₄Motor capacity range q_MBIf the motor capacity is too large, the time t in FIG.₅, T₆As shown in the control, gradually reduce the motor capacity, and the optimum motor capacity range q_MBWhen it becomes slightly smaller t₇To adjust the final capacity from time t₈As shown in FIG._MBThe optimal motor capacity range q in a short time_MBTherefore, the stability of the motor capacity control can be improved.
[0090]
Further, when performing the motor capacity control processing, processing is performed after confirming that the steering angle α inputted from the steering angle sensor 22 is “0”, that is, that the vehicle is traveling straight ahead. Therefore, avoiding the motor capacity control process in a state where a rotational speed difference occurs between the front and rear wheels when the vehicle is turning and the discharge flow rate of one of the piston pump 6 and the swash plate type variable capacity motor 10 is increasing. Therefore, the motor capacity control process can be performed with high accuracy.
[0091]
Further, in addition to the case where the steering angle α is “0”, the accelerator ON signal SA is output from the accelerator switch 26._ONIs not input, that is, after confirming that the accelerator pedal is not depressed, the motor capacity control process is started. Therefore, the motor capacity control process with the increased discharge flow rate of the piston pump 6 is performed. It is possible to avoid this, and the motor capacity control process can be performed with higher accuracy.
[0092]
Since the pressure state in the high pressure pipe 8H is detected by the ON / OFF state of the pressure switch 20, and the start time of the motor capacity control process is determined based on the detection result, the device configuration is simplified. Can do.
[0093]
Further, in this embodiment, even if the capacity of the piston pump 6 is not set with high accuracy, it is possible to obtain the optimum characteristic of the driving torque to the rear wheel side with respect to the difference in the rotational speed of the front and rear wheels by the motor capacity control process. Therefore, it is not necessary to set the capacity of the piston pump 6 and the swash plate type variable displacement motor 10 with high accuracy at the production stage, and the piston pump 6 and the swash plate type variable displacement motor 10 can be manufactured at low cost.
[0094]
In addition, even when different diameter tires are mounted on one of the front wheels or the rear wheels, the capacity of one of the piston pump 6 and the swash plate type variable displacement motor 10 changes. Since the characteristic of the driving torque toward the rear wheel with respect to the difference is corrected to the optimum value, normal four-wheel drive traveling can be obtained.
[0095]
In the above embodiment, the case where the step motor 116, the screw shaft 117, the ball nut 118, and the like are applied as the actuator of the capacity regulating mechanism 115 has been described. However, the present invention is not limited to this, and the pump housing is used as the actuator. A cylinder tube fixed to 100, a piston slidably disposed in the cylinder tube 140a, one end of which is connected to the piston, and a locking piece which contacts the lower right end of the swash plate 103 at the other end. A hydraulic cylinder having a formed piston rod may be applied, and this hydraulic cylinder may be controlled by a three-port, two-position electromagnetic directional switching valve controlled by the controller 130.
[0096]
In the four-wheel drive vehicle shown in FIG. 1, the case where the rear wheel differential 17 is provided has been described. However, the present invention is not limited to this, and the rear wheel differential 17 is omitted. Instead of this, a variable displacement motor may be provided individually on the left and right axles 18 of the left and right rear wheels 19.
[0097]
Furthermore, in the above-described embodiment, the embodiment based on the front wheel drive vehicle has been described. However, the present invention is not limited to this, and even when the rear wheel drive vehicle is used as a base, the rear wheel 19 is used as the drive wheel, and each component is arranged. By providing, the same effect as the said embodiment can be acquired.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a four-wheel drive vehicle according to the present invention.
FIG. 2 is a cross-sectional view showing a free swash plate type variable displacement motor according to the present invention.
FIG. 3 is a schematic diagram showing a mechanism of a free swash plate type variable displacement motor.
FIG. 4 is a block diagram showing a controller according to the present invention.
FIG. 5 is a flowchart showing a control processing procedure of the controller shown in FIG. 4;
FIG. 6 is a flowchart showing a processing procedure of motor capacity control processing means of the present invention.
FIG. 7 is a diagram showing the relationship between vehicle speed, discharge flow rate, and maximum output torque in a piston pump and a swash plate type variable displacement motor.
FIG. 8 is a time chart for explaining the operation of the motor capacity control processing means when the motor capacity of the swash plate type variable capacity motor is too small.
FIG. 9 is a time chart for explaining the operation of the motor capacity control processing means when the motor capacity of the swash plate type variable capacity motor is too large.
[Explanation of symbols]
1 Engine (main prime mover)
4 Drive axle
6 Piston pump (fluid pressure pump)
8H high-pressure piping (first flow path)
8L low-pressure piping (second flow path)
10 Swash plate type variable displacement pump (fluid pressure motor)
18 Driven axle
20 Pressure switch (pressure detection means)
22 Steering angle sensor (steering angle detection means)
24 Vehicle speed sensor (vehicle speed detection means)
26 Accelerator switch (accelerator depression detection means)
115 Capacity regulation mechanism
116 step motor
118 Ball nut
130 controller
CS_N1  First correction reverse rotation drive pulse
CS_N2  Second correction reverse rotation drive pulse
CS_P  Forward rotation drive pulse for correction
V_S1  First reference vehicle speed
V_S2  Second reference vehicle speed
α Steering angle

Claims (4)

A driving axle driven by the main prime mover, a fluid pressure pump that rotates in conjunction with the driving axle and discharges the working fluid, a fluid pressure motor that rotates in conjunction with the driven axle, and a discharge port of the fluid pressure pump -Wheel drive provided with a first flow path communicating with the suction port of the fluid pressure motor and a second flow path communicating with the suction port of the fluid pressure pump and the discharge port of the fluid pressure motor In the car,
Pressure detecting means for detecting the fluid pressure in the first flow path, traveling state detecting means for detecting the traveling state of the vehicle, and motor capacity control processing means for changing and controlling the capacity of the fluid pressure motor,
The motor capacity control processing means starts a control process when a rotational speed difference is not generated between the driving axle and the driven axle based on a running condition detection value of the running condition detecting means, and the pressure detecting means When the pressure detection value is greater than or equal to a predetermined value, the capacity of the fluid pressure motor is increased rapidly so that the capacity value exceeds the optimum capacity, and then the capacity is gradually increased to reach the optimum capacity. A four-wheel drive characterized in that the value is decreased, and when the pressure detection value of the pressure detection means is less than a predetermined value, the displacement of the fluid pressure motor is reduced and changed to an optimum capacity. car. The traveling state detecting means is constituted by a vehicle speed detecting means for detecting a vehicle speed, and the motor capacity control means is configured such that when the vehicle speed detection value of the vehicle speed detecting means is traveling in a predetermined low speed state, The four-wheel drive vehicle according to claim 1, wherein the capacity control is started . The running state detection means includes a steering angle detection means for detecting a steering angle, and the motor capacity control means controls the capacity of the fluid pressure motor when the detected value of the steering angle of the steering angle detection means is zero. The four-wheel drive vehicle according to claim 2, wherein The running state detection means includes an accelerator depression detection means for detecting whether or not the accelerator pedal is depressed, and the motor capacity control means determines that the accelerator pedal is not depressed by the accelerator depression detection means. 4. The four-wheel drive vehicle according to claim 3, wherein capacity control of the fluid pressure motor is started .

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