JP3977158B2 - Anti-vibration structure of hydraulic system in hydrostatic continuously variable transmission - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vibration isolating structure for a hydraulic device, and more particularly to a technique for preventing noise and vibration of a hydraulic device used in a working machine such as a tractor and a wheel loader such as a hydrostatic continuously variable transmission for traveling. Is.
[0002]
[Prior art]
For example, the hydrostatic continuously variable transmission for traveling shown in Japanese Patent Application Laid-Open No. 11-59210 is provided with a relief valve for determining the upper limit of circuit pressure, and the load is significantly increased by traveling on muddy ground. When the circuit pressure exceeds the limit, the relief valve opens to release the pressure and operate. As described above, a hydraulic device is generally equipped with a relief valve for device protection, maximum pressure setting, and the like.
[0003]
[Problems to be solved by the invention]
As described above, the relief valve is operated to open in a high pressure state in which a pressure exceeding the upper limit is applied to the circuit. Therefore, noise such as “pea” may be generated during the opening operation. This is considered to be caused by noise caused by resonance of movable parts such as a valve body and a return spring, or a valve box part due to pulsating pressure fluctuations during a relief operation.
[0004]
For this reason, noise has been eliminated by measures such as changing the dimensions and weight of each part of the relief valve or changing the shape within a range that does not affect the function. Each relief valve was dedicated. Permanent countermeasures to eliminate resonance are difficult to find, and inconvenient places where noise is generated, there is no choice but to perform dedicated countermeasures by trial and error, requiring troublesome and inefficient work was there.
[0005]
As described above, the hydraulic device of the hydrostatic continuously variable transmission has a surface in which noise and vibration are likely to occur due to resonance, and since there is no permanent countermeasure against them, noise and vibration can be effectively prevented. It was the actual situation that means were desired. Therefore, an object of the present invention is to provide a permanent countermeasure means that reduces or eliminates the noise and vibration such as the above-mentioned “pea” in the hydraulic apparatus, without realizing a significant cost increase.
[0006]
[Means for Solving the Problems]
[Configuration of Claim 1]
The structure of the vibration isolating structure of the hydraulic device in the hydrostatic continuously variable transmission according to the first aspect of the present invention includes a throttle channel and the throttle flow having a sectional area larger than the sectional area of the throttle channel. A damper comprising an expansion chamber communicating with the passage , and in the vicinity of a branch point to the relief valve in the supply / discharge oil passage connecting the hydraulic pump and the hydraulic motor of the hydrostatic continuously variable transmission , and The throttle channel is connected in communication with a portion of the relief valve toward the introduction oil channel .
[0007]
[Configuration of Claim 2]
The structure of the vibration isolating structure of the hydraulic device in the hydrostatic continuously variable transmission according to claim 2 is characterized in that the throttle flow is in a state of having a throttle channel and a cross-sectional area larger than the cross-sectional area of the throttle channel. Introducing oil branched from the supply / discharge oil path to the supply / discharge oil path connecting the hydraulic pump and the hydraulic motor of the hydrostatic continuously variable transmission A discharge-side flow path from a charge pump is connected via a passage, a relief valve is interposed in the introduction oil passage , and the vicinity of a branch point to the introduction oil passage in the supply / discharge oil passage is provided , and the relief The throttle passage is connected in communication with a portion of the valve that faces the introduction oil passage .
[0008]
(Action, effect)
According to the first and second aspects of the present invention, in the vicinity of the branch point to the relief valve in the supply / discharge oil passage connecting the hydraulic pump and the hydraulic motor of the hydrostatic continuously variable transmission , and toward the port of the relief valve This is a means for providing a damper comprising a throttle channel communicating with a part and an expansion chamber having a cross-sectional area larger than the cross-sectional area of the throttle channel. Even if the pulsating pressure fluctuation caused by the operation of the relief valve occurs toward the branch point to the relief valve in the supply / discharge oil passage, the vibration or pulsation is in the vicinity of the branch point , and the oil introduced into the relief valve Since the cross-sectional area increases at a stroke when it is transmitted to the expansion chamber via the constricted flow path provided at the part toward the path, the action of decreasing the impedance near the resonance frequency is created, and the vibration wave is short-circuited. The resonance phenomenon caused by vibration can be reduced without being propagated widely through the oil supply / discharge path.
[0009]
Since this vibration reduction action can always be exhibited by the presence of the damper, it is possible to obtain a vibration isolation action by performing a single modification in which the damper is connected in communication. Therefore, it is possible to eliminate the troublesome and inefficient conventional anti-vibration work of selecting and setting the best means by applying various measures to the part where the inconvenience due to resonance occurs.
[0010]
As a result, in the vibration isolating structure of the hydraulic device in the hydrostatic continuously variable transmission according to claims 1 and 2, the throttle channel in the damper having the throttle channel and the expansion chamber is supplied to and discharged from the resonance phenomenon. By ingeniously connecting to the portion of the oil passage near the branch point to the relief valve and leading to the introduction oil passage of the relief valve, inconvenience due to resonance such as noise and vibration can be avoided. Therefore, it is possible to provide a permanent vibration isolating means while being a simple and inexpensive single measure simply connecting a damper in the vicinity of the branch point to the relief valve in the supply / discharge oil passage.
[0011]
In particular, when the relief valve is opened due to the vibration reducing action of the damper, the resonance of the movable parts such as the movable valve body and the relief spring is suppressed or eliminated. It is possible to avoid the generation of noise. As a result, it is connected in the vicinity of the branch point to the relief valve in the supply / discharge oil passage connecting the hydraulic pump and the hydraulic motor of the hydrostatic continuously variable transmission , and to the portion of the relief valve toward the introduction oil passage. By providing a damper having a simple structure consisting of a throttle channel and an expansion chamber communicating with the throttle channel, it was possible to eliminate noise that was generated when the relief valve was relief-operated.
[0012]
〔Constitution〕
The structure of claim 3 is characterized in that, in the structure of claim 1 or 2, the damper is formed integrally with a casing for forming the hydraulic device.
[0013]
(Action, effect)
According to the configuration of the third aspect, since the damper is integrally formed with the casing, which is an essential member for constituting the hydrostatic continuously variable transmission, the vibration can be reduced in a compact and economical manner by combining the members. The structure could be provided. For example, when the casing is formed of a cast alloy such as cast iron such as a mission case, it is easy to integrally form a space portion such as a flow path or an expansion chamber.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 shows an agricultural tractor, where E is an engine, 1 is a front wheel, 2 is a rear wheel, 3 is a bonnet, 4 is a driving unit, 5 is an engine, 6 is a traveling mission, 7 is a vehicle body, and 8 is a driving seat. , 9 is a PTO shaft, 10 is a rear working device, 11 is a rear wheel fender, and g is a guard member.
[0015]
2 and 3 show the HST 12 which is the main part of the traveling mission 6, and FIG. 4 shows the hydraulic circuit diagram thereof. The HST 12 transmits engine power input to the input shaft 13 to the pump shaft 15 of the variable displacement hydraulic pump P via the flat gear interlocking mechanism 14 and is operated by the pressure oil of the hydraulic pump P. The output shafts 16 and 17 of the hydraulic motors M1 and M2 are directly coupled using a coupling 18 (an example of the output merging mechanism A), and is configured as a one-pump and two-motor type. In FIG. 4, the portion surrounded by a dashed line is the transmission case 6c, and those drawn on the outside thereof (the discharge side oil passage 19a of the charge pump 19 and the electromagnetic switching valve 39 described later) are external piping. It has become a case external component.
[0016]
The pump shaft 15 is equipped with a charge pump 19 for the HST 12, and its tip protrudes out of the transmission case 6c, and serves as a protruding tip shaft portion 20 that can be used for a live PTO shaft or the like. The transmission case 6c includes a main case portion 21 that mainly covers the hydraulic pump P and the first hydraulic motor M1, a lid case portion 22 that supports the input shaft 13 and the like, a motor case portion 23 that covers the second hydraulic motor M2, and An oil passage block 24 interposed between the main case portion 21 and the motor case portion 23 is provided.
[0017]
As shown in FIG. 4, the plunger type hydraulic pump P is a variable capacity type, the axial piston type first hydraulic motor M1 is a constant capacity type, and the axial piston type second hydraulic motor M2 is a variable capacity type. Each of these two hydraulic motors M1, M2 is connected to the pressure oil input side ports 25, 26 and the oil discharge side ports 27, 28 in communication to form a parallel circuit h. It is connected to a hydraulic pump P via supply / discharge oil passages 29 and 30. 34 and 35 are travel relief valves for setting the maximum load pressure on the forward side and the reverse side, and 36 is a main relief valve for setting the upper limit of the circuit pressure. Note that the functions of the input side and oil drain side ports 25 to 28 are opposite to each other when the output rotation direction as the HST 12 is forward rotation and reverse rotation.
[0018]
By operating the hydraulic speed change cylinder 31 linked to the swash plate operating portion 33 of the hydraulic pump P by switching the speed change valve 32, the swash plate angle of the hydraulic pump P changes and the pressure oil per unit time is changed. The discharge amount is changed, the energy of the discharged pressure oil is converted into rotational force by the first and second hydraulic motors M1, M2, and the rotational power from the input shaft 13 can be switched between the forward side and the reverse side. At the same time, the HST 12 functions so as to shift continuously and take out from the output shaft 17 and transmit it to the rear wheel 2 via a sub transmission mechanism (not shown) on both the forward side and the reverse side.
[0019]
The second hydraulic motor M2 is configured as a two-state switching type between a first speed state in which the swash plate angle is equal to the swash plate angle in the first hydraulic motor M1 and a second speed state in which the swash plate angle is 0 degrees. . As shown in FIG. 4, a switching cylinder 38 acting on the swash plate operating portion 37a of the swash plate 37 of the second hydraulic motor M2, a two-position switching type electromagnetic switching valve 39 for switching the switching cylinder 38, and A button switch 40 is provided. That is, by operating the button switch 40 and switching the electromagnetic switching valve 39 to expand and contract the switching cylinder 38, the first speed state (the state shown in FIG. 3) in which the swash plate 37 is inclined and the swash plate 37 are The second speed state (the state shown in FIG. 2) in which the inclination angle is 0 when standing vertically is configured to be selectively switched.
[0020]
The switching cylinder 38 is configured by disposing an operation portion 41 composed of a cylinder chamber 41a and a piston rod 41b and a return portion 42 composed of a return spring 42a and a push rod 42b in the motor case portion 23 so as to face each other. If pressure oil is supplied to the cylinder chamber 41a and the piston rod 41b is forcibly pushed out against the urging force of the return spring 42a, the first speed state shown in FIG. 3 is reached, and oil is discharged from the cylinder chamber 41a. The push rod 42b pushes the swash plate operating portion 37a back to the 0 degree position by the urging force of the return spring 42a, and self-returns to the second speed state shown in FIG.
[0021]
The second hydraulic motor M2 is disposed so that the axis of the output shaft 17 is aligned with the axis X of the output shaft 16 of the first hydraulic motor M1. Therefore, when viewed as a motor unit, it is long in the axial center X direction (front-rear direction), but can be compactly formed in the vertical and horizontal directions, and is suitable for a tractor or the like that has a long mission space. It has a layout.
[0022]
In the first speed state, both the hydraulic motors M1 and M2 have the same swash plate angle, so that it is possible to generate almost twice as much torque as that by the first hydraulic motor M1. Theoretically, the torque is doubled, but in reality there is an energy loss such as a mechanical friction loss, so the torque extracted from the output shaft 17 is “almost twice”. Accordingly, if the hydraulic pump P is operated at the lowest speed in the first speed state, the maximum torque can be generated almost twice as much as the conventional one, which is suitable for work traveling in which the load torque such as plow work in a muddy area becomes very large. It will be a thing. Further, in the second speed state in which the inclination angle is 0, the pressure oil passes through the second hydraulic motor, so that it is used as an HST in a one-motor state in which only the first hydraulic motor M1 is provided. can do.
[0023]
Next, a description will be given of an anti-vibration mechanism B that reduces noise during operation of the relief valve and discharge pulsation of the charge pump.
[0024]
As shown in FIG. 4, a vibration isolation mechanism B communicating with each oil passage (an example of the pressure oil passage r) is provided near the branch point to the relief valves 34 and 35 in each of the supply / discharge oil passages 29 and 30. It is. The two anti-vibration mechanisms B and B near the relief valves 34 and 35 are configured to avoid the generation of noise such as “pea” from the relief valves 34 and 35 during the relief operation.
[0025]
As shown in FIG. 5 to FIG. 7, the anti-vibration mechanism B for noise prevention includes the throttle channel 43 and the throttle channel 43 in a state having a cross-sectional area larger than the sectional area of the throttle channel 43. The damper d is configured by including an expansion chamber 44 that communicates, and the throttle channel 43 is connected to the supply / discharge oil channel (an example of a pressure oil channel in the hydraulic device) 29 and 30 in communication. A throttle channel 43 composed of pores having a diameter of 1.5 mm and an expansion chamber 44 having a diameter several times that of the throttle channel 43 are integrally formed in a transmission case 6c made of cast iron, and the expansion chamber 44 is sealed. In the state in which the plug 45 is screwed, the volume of the expansion chamber 44 is set to be about 1.5 cubic centimeters.
[0026]
The pair of relief valves 34 and 35 are the same, and the relief valve 34 will be described. The relief valve 34 also has a check valve function. The flow is configured as a composite valve that exerts a check action that allows almost no resistance to pass. In FIG. 5, 46 is a relief spring, 47 is a damping chamber, 48 is a valve body, 49 is a plug, 50 is a valve seat, 59 is a support body in which the relief valve body 48 is slidably fitted, 60 is a spring receiver, 61 Is a winding spring for closing and energizing the valve body 48 very lightly.
[0027]
That is, when the pressure of the introduction oil passage 29b communicated with the supply / discharge oil passage 29 becomes a predetermined value or more, the relief valve 34 is opened against the biasing force of the relief spring 46, and the pressure of the supply / discharge oil passage 29 is increased. Until the pressure becomes less than the predetermined pressure, a relief action is exerted to release the pressure to the discharge side oil passage 19a through the discharge oil passage 29a. If the hydraulic oil as the HST 12 becomes insufficient due to leakage or the like, the relief valve 34 is opened against the extremely light urging force of the winding spring 61, and the charge pressure can be supplied to the HST 12 with almost no resistance. is there.
[0028]
The throttle passage 43 communicates with the damping chamber 47 in each relief valve 34, 35 via the respective introduction oil passages 29b, 30b. The throttle channel 43 and the expansion chamber 44 can be formed by machining such as drilling from the end of the mission case 6c. The relief valve 34 can also be configured inside a hole formed by machining that drills from the end of the mission case 6c (an example of a casing).
[Brief description of the drawings]
FIG. 1 is a side view of a tractor. FIG. 2 is a side view showing a structure of an HST in a second speed state. FIG. 3 is a side view showing a structure of the HST in a first speed state. Fig. 5 is a cross-sectional view showing a relief valve and a vibration isolating mechanism for noise prevention. Fig. 6 is a front view of a mission case at a site where the vibration isolating mechanism is mounted.
6c Casing 12 Hydrostatic continuously variable transmission 19 Charge pump 19a Discharge side passage 29, 30 Supply / discharge oil passage 29b, 30b Introduction oil passage 34, 35 Relief valve 43 Throttle passage 44 Expansion chamber A Output junction mechanism d Damper P Pump M1, M2 Motor

Claims (3)

The damper includes a throttle channel and an expansion chamber communicating with the throttle channel in a state having a cross-sectional area larger than the sectional area of the throttle channel. A hydrostatic type in which the throttle passage is connected to a portion of the supply / discharge oil passage connecting the hydraulic pump and the hydraulic motor in the vicinity of the branch point to the relief valve and toward the introduction oil passage of the relief valve. Anti-vibration structure of hydraulic device in continuously variable transmission. The damper includes a throttle channel and an expansion chamber communicating with the throttle channel in a state having a cross-sectional area larger than the sectional area of the throttle channel. A discharge side flow path from the charge pump is connected to the supply / discharge oil path connecting the hydraulic pump and the hydraulic motor via an introduction oil path branched from the supply / discharge oil path, and a relief valve is connected to the introduction oil path. And a hydrostatic continuously variable transmission in which the throttle passage is connected to a portion of the supply / discharge oil passage that is near the branch point to the introduction oil passage and that faces the introduction oil passage of the relief valve. Anti-vibration structure of the hydraulic device in the device.   The vibration isolating structure for a hydraulic device in a hydrostatic continuously variable transmission according to claim 1 or 2, wherein the damper is formed integrally with a casing for constituting the hydrostatic continuously variable transmission.

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