JP2689493B2 - Transmission control device for automatic transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

 The present invention relates to a shift control device for an automatic transmission.

[Prior art]

Conventionally, a gear shift mechanism and a plurality of friction engagement devices are provided,
BACKGROUND ART An automatic transmission configured to selectively switch the engagement state of a friction engagement device by operating a hydraulic control device so as to achieve any one of a plurality of shift speeds is already widely known. Further, in order to reduce such a shift at the time of shifting of the automatic transmission, an accumulator capable of adjusting a transient hydraulic pressure between a shift valve for switching a shift stage and a friction engagement device when the friction engagement device is engaged. It is known to provide a. This accumulator has a cylinder piston structure and keeps the transient hydraulic pressure applied to the frictional engagement device at a substantially constant hydraulic pressure for a predetermined period of time, thereby reducing the shock during shifting. The optimum value of the constant hydraulic pressure changes depending on the engine torque input to the automatic transmission. The value of the constant hydraulic pressure can be controlled by changing the hydraulic pressure (back pressure) applied to the back pressure chamber of the accumulator. Therefore, it is known that the hydraulic pressure applied to the back pressure chamber of the accumulator is electronically controlled, and as a result, the transient hydraulic pressure to the frictional engagement device is precisely controlled (for example, Japanese Patent Laid-Open No. 61-14965).
7).

[Problems to be solved by the invention]

By the way, the applicant previously proposed a method of controlling the feedback hydraulic pressure of the transient hydraulic pressure when the frictional engagement device is engaged, also for the purpose of reducing shift shock (Japanese Patent Laid-Open No. 62-44).
700; not known). This feedback control first detects the rotational speed of a member whose rotational speed changes as a result of gear shifting, such as the turbine shaft in an automatic transmission, the drum of each clutch or brake, or the engine. The engagement transient hydraulic pressure of the frictional engagement device in the automatic transmission is fed back controlled so that the rotational speed changes along the trajectory of the target rotational speed that the member should follow after the gearshift output. When such feed back control is adopted, the engagement transient hydraulic pressure of the friction engagement device is always equal to the target rotation speed regardless of the vehicle-specific variations that occur during manufacturing or over time. It is controlled so that it changes along the locus of, and it is possible to always obtain the optimum shift transient state. However, when actually performing such feedback control, it is not possible to respond to a sudden change in the friction engagement of the friction engagement device at the end of the shift due to the response delay of the hydraulic control system. There was a problem that it was not possible to prevent a sudden change in the output shaft torque (occurrence of gear shift shock) that occurs at the moment of final engagement. In view of such a problem, in Japanese Patent Laid-Open No. 61-84446, in controlling the engagement transient oil pressure of the friction engagement device with feedback feedback, the rotation speed of the checkdown drum is 140 rpm.
It is disclosed that, in the following cases, the duty ratio at that time is held for a predetermined time by a timer. However, if the feed back control is stopped at such a timing, the relationship between the magnetism that started to maintain the duty ratio and the gear shift end timing will vary greatly, and the duration of the feed back control will become too short, resulting in an optimal gear shift transient state. However, there is a problem in that it may not be possible to secure the gear, or conversely, the period of the holding control may become too short to prevent the gear shift shock at the end of the gear shift.

[Object of the invention]

The present invention has been made in view of such a problem, and accurately controls the end of the shift while controlling the engagement transient hydraulic pressure with feedback control, and always suppresses the sudden change in the output torque generated at the end of the shift. It is an object of the present invention to provide a shift control device for an automatic transmission that can be performed.

[Means for Solving the Problems]

The present invention relates to a shift control device for an automatic transmission, which is configured to feed back the engagement transient hydraulic pressure of a friction engagement device in the automatic transmission so that the actual shift transient state becomes a target shift transient state. The shift is provided with a means for judging whether or not the centrifugal oil pressure is generated when the shift is executed, and a means for detecting the end of the shift based on the judgment, and the end of the shift is detected. When the feedback control is performed, the feed back control is stopped, and the engagement transient hydraulic pressure at the final stage of the shift is switched to the predictive control to achieve the above object. In addition, the engagement transient hydraulic pressure of the friction engagement device in the automatic transmission is changed so that the actual shift transient state becomes the target shift transient state. In a shift control device for an automatic transmission configured to control a speed by feedback control, a shift speed is controlled based on a difference between a synchronous rotation speed of a member whose rotation speed changes and a real rotation speed after shifting. Means for determining the end, means for detecting the engine torque, and means for determining the end of the shift based on the engine torque, and means for changing the threshold value relating to the difference between the synchronous rotation speed and the actual rotation speed. Be prepared, when the end of the shift is detected,
The above object is also achieved by stopping the feed back control and switching the engagement transient hydraulic pressure at the end of the shift to the prospective control.

[Action]

In the present invention, since the transient hydraulic pressure at the time of engagement of the friction engagement device is feedback-controlled, it is possible to always obtain an ideal shift transient state regardless of variations inherent to the vehicle or changes over time. Will be able to. Further, in the present invention, when executing the feed back control of the engagement transient hydraulic pressure, it is detected whether or not the gear shift has reached the end, and when it is detected that the gear shift has come to the end, this relation is detected. The feed back control of the combined transient hydraulic pressure is stopped, and thereafter, the engagement transient hydraulic pressure is (probably) controlled by a predetermined map. As a result, in the present invention, the rotational speed of the member whose rotational speed changes due to the execution of the speed change from the initial stage to the middle stage of the speed change in the automatic transmission is changed along the trajectory of the target rotational speed. After the engagement hydraulic pressure of the friction engagement device is feedback-controlled and the end of the shift is detected, the feedback transition control of the engagement transient hydraulic pressure is stopped and the engagement transient hydraulic pressure is controlled by a predetermined map. Since the predictive control is performed, the engagement transient hydraulic pressure can be reliably reduced at the final stage of the shift, and the most ideal shift transient state can be obtained from the initial stage to the final stage of the shift. Moreover, the present invention considers whether or not the shift is a shift generated by centrifugal hydraulic pressure in determining the "end of shift" (Claim 1), or the change in the rotational speed of the turbine depending on the engine torque. Since the fact that the method is different is taken into consideration (claim 2), the end of the shift can always be accurately determined (especially in relation to the complete end of the shift). Although the present invention does not limit how to perform the predictive control after the end of the shift is determined, the map used in this predictive control may be, for example, the type of shift (type of friction engagement device). ) And engine load based on the engine load.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this embodiment, the back pressure of the accumulator is controlled in order to control the transient hydraulic pressure when the friction engagement device is engaged. In addition, a turbine shaft is selected as a member whose rotational speed changes when a shift is performed. In the feed back control of the engagement transient hydraulic pressure, the actual turbine rotation speed NT is the turbine target rotation speed.
This is done by electronically controlling the duty solenoid (S _D ) so that it changes along the trajectory of NT ₀ . The turbine target rotation speed NT ₀ is determined for each type of shift according to the engine torque (or throttle opening). FIG. 1 shows an overall outline of an automatic transmission for a vehicle and an engine to which this embodiment is applied. This automatic transmission has a torque converter section 20 as a transmission section and an overdrive mechanism section 40.
And an underdrive mechanism 60 having three forward stages and one reverse stage. The torque converter section 20 includes a pump 21 and a turbine 2
2. It is a well-known device having a stator 23 and a lock-up clutch 24. The overdrive mechanism section 40 includes a sun gear 43, ring gear 44, planetary pinions 42, and includes a pair of planetary gear unit consisting of Kiyariya 41, clutch C ₀ the rotation state of the planetary gear device, the brake B _0, the one-way by the clutch F ₀ are connexion control. The underdrive mechanism 60 includes a common sun gear 6
1, two sets of planetary gear units including ring gears 62 and 63, planetary pinions 64 and 65, and carriers 66 and 67 are provided, and the rotational state of the two sets of planetary gear units and the connection state with the overdrive mechanism are clutched. C _1, C _2, the brake B ₁
.About.B _3, and are by connexion controlled freewheel F _1, F _2. Since this transmission part is known per se, the concrete connection state of each component is only shown as a skeleton in FIG. 1, and its detailed description is omitted. This automatic transmission includes a transmission unit as described above and a computer (ECU) 84. The computer 84 includes a throttle sensor 80 that detects the throttle opening θ for reflecting the output (torque) of the engine 1, a vehicle speed sensor (rotational speed sensor of the output shaft 70) 82 that detects the vehicle speed n ₀ , and a speed change transient. NT sensor 99 for detecting the rotation speed NT of the turbine 22 of the automatic transmission for reflecting the state
Etc. are input. The computer 84 controls the solenoid valves S ₁ , S ₂ (for shift valves), and SL in the hydraulic control circuit 86 according to the preset throttle opening-vehicle speed shift map.
By driving and controlling (for the lockup clutch), a combination of engagements of respective clutches, brakes, etc. as shown in FIG. FIG. 3 shows a main part of the hydraulic control circuit 86. In the figure, reference numeral S _D is a duty solenoid, 108 is an accumulator control valve, 110 is a modulator valve, 112 is an accumulator, 114 is a shift valve,
115 is a damper. In this figure, the brake B ₂
Are typically shown. As is clear from FIG.
The brake B ₂ is a friction engagement device that is engaged when a shift from the first gear to the second gear is achieved. Using a hydraulic pressure generated by an oil pump (not shown) as a base pressure, a line pressure PL is generated by a known method. This line pressure PL is applied to the port 110A of the modulator valve 110. Modulator valve 110 has a line pressure PL
Receiving the specified modulator pressure Pm in a well-known manner
Occurs at 110B. The duty solenoid S _D receives the modulator pressure Pm and receives the turbine rotation speed NT and the turbine target rotation speed NT _0.
A solenoid pressure PS ₁ is generated according to the difference between and by a known method. That is, the rotation speed NT of the turbine 22 is input to the computer 84 as described above. The turbine speed NT is compared to a turbine target rotation speed NT ₀ set in advance according to the type of engine torque and speed. For example, in the case of a 1 → 2 shift, the execution of the 1 → 2 shift lowers the turbine rotational speed NT. If turbine speed NT
Falls earlier than the target rotation speed NT ₀ (NT−NT ₀ <
(In the case of 0), the shift progresses too fast, so
In order to reduce the engagement transition oil pressure of the brake B _2, the NT-
Duty ratio command corresponding to the NT ₀ is applied to the de Yu Tay solenoid S _D, De Yu Tay solenoid S _D, is intended to generate solenoid pressure PS ₁ in accordance with the duty ratio command in a known manner. In this example, when the duty ratio increases (10
As it approaches 0%), the generated solenoid pressure PS ₁ becomes smaller. Reference numeral 115 in FIG. 3 is a damper for suppressing the pulsating flow. The solenoid pressure PS ₁ is input to the port 108A of Aki Yumu regulator control valve 108. The accumulator control valve 108 receives the line pressure PL ₁ and the solenoid pressure PS ₁ from the duty solenoid S _D as input signals, and uses the line pressure PL ₂ of the port 108B as the accumulator back pressure Pac.
Adjust the pressure. That is, the accumulator back pressure Pac, in other words, basically the line pressure PL ₂ is regulated by the line pressure PL ₁ and the biasing force of the spring 108C, and the solenoid pressure PS ₁ of the duty solenoid S _D. It has been corrected. When the shift determination (in this case, shift determination from the first speed to the second speed) is performed by the computer 84, the solenoid valve S ₁
Shift valve 114 is switched in a known manner via
Line pressure PL (P _B0 ) begins to be supplied to brake B ₂ . In response to this supply, the piston 112 of the accumulator 112
A begins to rise. While the piston 112A is rising, the hydraulic pressure (P _B0 ) supplied to the brake B ₂ is maintained at a substantially constant hydraulic pressure that balances the downward biasing force of the spring 112B and the downward force acting on the piston 112A. Will be done. The force that pushes the piston 112A downward is the accumulator back pressure P applied to the back pressure chamber 112C of the accumulator 112.
It is generated by ac. Therefore, back pressure
As described above, the Pac is connected to the modulator valve 110, the duty solenoid S _D and the accumulator control valve 10
By controlling via 8, it is possible to arbitrarily control the transient hydraulic pressure P _B0 at the time of engagement with the brake B ₂ . Since the duty solenoid S _D is controlled depending on the difference between the turbine rotation speed NT and the turbine target rotation speed NT ₀ as described above, the turbine rotation speed NT is eventually changed by such a hydraulic system. The feed back control can be performed so as to change along the turbine target rotation speed NT ₀ . Generally, in an automatic transmission, due to influences of characteristics of a hydraulic control system, engine characteristics, and gear ratio of a gear train, different gear characteristics are exhibited for each gear stage and throttle opening. Therefore, it is very effective to reduce the gear shift shock by controlling the engagement transient hydraulic pressure in the feed back manner by catching the change in the turbine rotational speed NT ₀ during gear shift as described above. However, this hydraulic control system necessarily includes a response delay and cannot cope with a sudden change in output torque (shift shock) particularly due to a change in the friction coefficient of the friction engagement device at the end of the shift. Therefore, as a qualitative tendency, in consideration of the fact that the output torque at the completion of the shift increases due to the dynamic friction coefficient <static friction coefficient of the friction engagement device, the feedback control is stopped at the end of the shift, and the so-called “probability” is assumed. Consider lowering the engagement transient oil pressure. At this time, it is necessary to change the degree of decrease in the engagement transient hydraulic pressure depending on the type of gear shift (specifically, the type of friction engagement device involved in the gear shift) and the throttle opening.
For example, in the case of shifting from the first speed to the second speed, the friction engagement device to be engaged is the brake B ₂ as shown in FIG. Since the brake B ₂ is fixed to the housing, no particular centrifugal oil pressure is generated when engaging the brakes. Therefore, it is necessary to consider the influence of the centrifugal oil pressure on the engagement transient oil pressure at the end of the shift. There is no. On the other hand, in the case of shifting from the second speed to the third speed, the friction engagement device to be engaged is the clutch C ₂ as shown in FIG. This clutch C ₂ starts to rotate upon engagement, so that centrifugal pressure is generated by this rotation. Therefore, the engagement pressure at the end of the shift becomes larger by the amount of the centrifugal oil pressure than in the case of the shift from the first speed to the second speed described above. Conversely, in order to reduce the gear shift shock by lowering the engagement transient hydraulic pressure at the end of the gear shift,
In the case of shifting from the third speed to the third speed, a larger decrease in hydraulic pressure is required than in the case of shifting from the first speed to the second speed. Further, in general, even for the same type of gear shift, the amount of energy to be absorbed by the friction engagement device varies depending on the engine torque (engine load). Therefore, it is necessary to consider the factor of engine torque. That is, when it is determined whether or not the shift has reached the end, whether or not the difference between the synchronous rotational speed of the turbine and the actual rotational speed reaches a predetermined value as described later, the same is applied. Even for the type of gear shifting, the amount of change in turbine rotation speed before and after gear shifting differs depending on the engine torque. Therefore, the difference (threshold value) between the turbine synchronous rotation speed and the actual rotation speed for determining the end of gear shifting is Needs to be changed according to the engine torque. FIG. 4 shows the control procedure in this embodiment. At step 202, a shift determination is made according to the vehicle speed and the throttle opening. As a result, a predetermined shift output is output at step 204. In step 206, the inertia-phase (substantially the start of shifting, that is, the rotation speed of the turbine 22 is reduced at the rotational speed NT ₀ )
Is detected. When the inertia phase is detected, the duty output value D _i to the duty solenoid S _D is calculated in step 208, and the feed back control of the engagement transient hydraulic pressure is executed. The duty output value D _i is calculated based on the difference between the target rotation speed NT and the actual rotation speed NT ₀ of the turbine 22 as described above. After the feed back control has been executed in this manner, the end of the shift is detected at step 210. This detection is based on the fact that the turbine speed NT is the output shaft 70 of the automatic transmission.
It is performed by determining whether or not the rotational speed n ₀ has been close to the value (turbine synchronous rotational speed) obtained by multiplying the gear ratio i _H of the newly formed shift stage. Specifically, NT ₀ −n ₀ × i _H
By determining whether the difference .DELTA.N has decreased below a predetermined value. The predetermined value for the difference ΔN is determined in advance depending on the type of shift and the engine torque (slottle opening) for the reason described above. An example thereof is shown in the left column of FIGS. 5 (A) and 5 (B). In FIG. 5, (A) shows an example of 1 → 2 shift, and (B) shows an example of 2 → 3 shift. When the end of the shift is detected at step 210, the routine proceeds to step 212, where the predictive control of the duty ratio D _E as shown in the right column of FIGS. 5A and 5B is performed. The reason why the duty ratio D _E in this predictive control is thus determined for each type of shift and throttle opening is as described above. As a result, the engagement transient hydraulic pressure can be reliably reduced at the end of the gear shift, and gear shift shock can be reduced. This state is shown in FIGS. 6 and 7. In the example of FIG. 6, all the transient hydraulic pressures at the engagement from the start of the inertia phase to the completion of the shift are determined by the feed back control.
Therefore, it cannot follow the sudden change in the friction coefficient at the end of the shift, and
A sudden torque change occurs at the point. On the other hand, FIG. 7 shows the gear shift characteristic in the above-mentioned embodiment. Since the hydraulic pressure is reduced from point B to a predetermined level in anticipation of the increase in the friction coefficient at the end of gear shift, a rapid increase in torque occurs. It can be suppressed. The duty ratio at point B is the duty ratio in Fig. 5.
It is equivalent to D _E. In step 214, it is detected whether the difference ΔN becomes smaller than 50, that the shift is completely completed,
End the prospective control. It should be noted that the present invention does not limit how to determine the end of the shift. Further, in the above-mentioned embodiment, the back pressure of the accumulator is regulated by the duty solenoid, but this may naturally be a linear solenoid.

【The invention's effect】

As described above, according to the present invention, while the feed back control of the engaging hydraulic pressure is being performed, the end of the shift is accurately determined, and the hydraulic pressure is changed from the determination of the end of the shift until the complete shift. As a result, it is possible to properly execute the prospective control that reduces the shift control, and it is possible to obtain an excellent effect that the shift shock can always be favorably reduced.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an automatic transmission for a vehicle to which an embodiment of the present invention is applied, FIG. 2 is a diagram showing an operating state of a friction engagement device in the automatic transmission, and FIG. FIG. 4 is a hydraulic circuit diagram showing a main part in the hydraulic control device of the automatic transmission, FIG. 4 is a flow chart showing a control procedure, and FIG. 5 is ΔN for determining the end of the shift, and FIG. Fig. 6 is a diagram showing the duty ratio D _E , Fig. 6 is a gear shift characteristic diagram when the feed back control is executed until the gear shift is completed, and Fig. 7 is a diagram when the feed back control is stopped from the end of the gear shift and the prospective control is executed. It is a shift characteristic diagram. 108 …… Aquimulator control valve, 112 …… Akyumulator, 114 …… Shift valve, S _D …… Duty solenoid, PS ₁ …… Solenoid pressure, NT …… Turbine rotation speed, NT ₀ …… Turbine target rotation Speed, D _i …… Due duty ratio in feedback control, D _E …… Duty ratio in open control.

Front Page Continuation (72) Inventor Yuji Kashiwara 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (56) References JP-A-61-84446 (JP, A)

Claims (2)

(57) [Claims] 1. A shift control device for an automatic transmission configured to feed-back control an engagement transient hydraulic pressure of a friction engagement device in the automatic transmission so that an actual shift transient condition becomes a target shift transient condition. , The means for determining whether or not the shift is a shift in which centrifugal oil pressure is generated when the shift is executed, and means for detecting the end of the shift based on the determination, When detected, the feed back control is stopped, and the engagement transient hydraulic pressure at the final stage of the shift is switched to predictive control. 2. The rotational speed of the engagement transient hydraulic pressure of the frictional engagement device in the automatic transmission changes as the gear shifting is executed so that the actual gear shifting transient state becomes the target gear shifting transient state. In a shift control device for an automatic transmission configured to control the rotational speed of a member by feedback control, based on a difference between a synchronous rotational speed after shifting of a member whose rotational speed changes and an actual rotational speed. Means for determining the end of the shift, means for detecting the engine torque, and means for changing the threshold value for the difference between the synchronous rotation speed and the actual rotation speed for judging the end of the shift based on the engine torque. And when the end of the shift is detected, the feed back control is stopped and the engagement transient hydraulic pressure at the end of the shift is switched to the prospective control. Shift control device of the dynamic transmission.