JP2000346195A - Supplying mechanism of hydraulic servo mechanism control pressure in hydraulic continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency in a low load in an integrated hydraulic continuously variable transmission having a hydraulic servomechanism for controlling a movable swash angle by supplying a main circuit pressure through a selector valve as the control pressure of the hydraulic servo mechanism. SOLUTION: When an engine is stopping, or an HST transmission 10 is keeping the neutral state, lateral valves 51L, 51R keep the neutral positions since the hydraulic pressures of lateral main circuits 50L, 50R are substantially equal to each other. When the pressure of the right main circuit 50R of the main circuits 50L, 50R is raised, this pressure gets into a spring chamber through the valve oil passage 51c of a spool 51a in the valve 51R, the spool 51a of the valve 51R is moved to the left to press the spool 51a of the valve 51L to the left, whereby a selector valve 51 is switched to the left. Accordingly, the hydraulic oil of the right main circuit 50R is supplied to a hydraulic servomechanism side through the spool groove, servo connecting passage 51e of the valve 51R.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a hydraulic circuit in a hydraulic continuously variable transmission (hereinafter, referred to as an HST type transmission), and more particularly to a structure for supplying a control pressure to a hydraulic servo mechanism. .

[0002]

2. Description of the Related Art Conventionally, an HST type transmission has a structure in which the angle of a movable swash plate of a hydraulic pump is adjusted by a hydraulic servo mechanism to adjust the discharge amount of hydraulic oil. And the charge circuit pressure was used as the control pressure of the hydraulic servo mechanism.

[0003]

However, while a charge circuit pressure of about 4 to 6 kg / cm ² is sufficient,
If that pressure is also used as the control pressure of the hydraulic servo mechanism,
The charge circuit pressure must be set as high as about 15 to 25 kg / cm ² . Further, the charge flow rate is required most when the main circuit pressure is the highest, and the charge pump must always discharge the maximum flow rate. Even if the required charge flow rate is small because the main circuit is low, the maximum flow rate must be discharged and the surplus flow rate must be released from a relief valve set to about 15 to 25 kg / cm ² . This results in a decrease in the efficiency of the HST type transmission, particularly in a low load region.

[0004]

In order to solve the above problems, the present invention proposes the following solutions. That is, in an integrated hydraulic continuously variable transmission provided with a hydraulic servo mechanism for controlling the movable swash plate angle, the main circuit pressure is supplied as the control pressure of the hydraulic servo mechanism via the switching valve.

In an integrated hydraulic continuously variable transmission provided with a hydraulic servo mechanism for controlling a movable swash plate angle, a main circuit pressure is supplied as a control pressure of the hydraulic servo mechanism via a switching valve and a pressure reducing valve. Configuration.

Further, the switching valve and the pressure reducing valve have an integral structure.

In an integrated hydraulic continuously variable transmission provided with a hydraulic servo mechanism for controlling a movable swash plate angle, a main circuit pressure is supplied as a control pressure of the hydraulic servo mechanism via a pressure reducing valve and a throttle valve. The configuration was adopted.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In an embodiment of the present invention, the HST
A description will be given using a working vehicle equipped with a transmission. FIG. 1 is a side view of a work vehicle, FIG. 2 is a side view thereof, and FIG.
FIG. 4 is a front sectional view of the same type transmission, FIG.
FIG. 6 is an HST hydraulic circuit diagram of the present invention, and FIG.
FIG. 7 is a partially enlarged cross-sectional view of the switching valve, FIGS. 8 and 9 are cross-sectional plan views showing a moving state of the switching valve, and FIG. 10 is a hydraulic circuit diagram of a conventional HST transmission. It is.

First, the configuration of a working vehicle equipped with a rotary cultivator will be described with reference to FIGS. A rotary tiller 2 is connected to the rear of the work vehicle 1, and the rotary tiller 2 is driven by a part of the output of the engine 3 of the work vehicle 1. This work vehicle 1 has front and rear wheels 4
A bonnet 6 is disposed at the front of a main body that suspends the rear wheel 5, and the engine 3 is disposed inside the bonnet 6. A steering handle 7 is provided behind the hood 6, and a seat 8 is provided behind the steering handle 7. A main transmission lever is protruded from the side of the seat 8. The steering handle 7 and the seat 8 are covered by a cabin 9.

A hydraulic continuously variable transmission (HST type transmission) 10 is disposed behind the engine 3 to transmit the power from the engine 3 to the rear wheels 5 for driving. However, depending on the operation, a four-wheel drive that transmits the driving force to the front wheel 4 and the rear wheel 5 at the same time is also possible.

The driving force of the engine 3 is transmitted to a PTO shaft 11 protruding from the rear end of the HST transmission 10,
The TO shaft 11 is driven, and the rotary tiller 2 which is a working machine connected to the rear end of the machine is driven. The rotary cultivator 2 is connected to the work vehicle via the connection device 12, and the vertical position and the left and right inclination angles of the rotary cultivator 2 can be adjusted by an elevating device provided in the work vehicle 1. .

Next, the configuration of the HST type transmission 10 will be described. 3 and 4, the variable displacement hydraulic pump 21 and the hydraulic motor 22 are included in a housing 31 and are arranged on the same surface of an oil passage plate 32. The variable displacement hydraulic pump 21 includes a drive shaft 21a,
The cylinder block 21b includes a cylinder block 21b which is inserted and rotates together with the drive shaft 21a, a plunger 21e slidably inserted into the cylinder block 21b, and a movable swash plate 21c abutting the plunger 21e. The movable swash plate 21c is configured to regulate the sliding amount of the plunger 21e and to adjust the discharge amount of the working oil of the variable displacement hydraulic pump 21. The oil passage plate 32 is provided with an oil passage.
Hydraulic oil is supplied from a variable displacement hydraulic pump 21 to a hydraulic motor 22 via the oil passage.

The hydraulic motor 22 is a variable displacement hydraulic pump 2
1, is inserted into the oil passage plate 32, and one end is inserted into the housing 3.
1, an output shaft 22a rotatably supported by 1, a cylinder block 22b into which the output shaft 22a is inserted and rotated together with the drive shaft 22a, a plunger 22e slidably inserted into the cylinder block 22b, and the plunger 22
e of the fixed swash plate 22c.
The cylinder block 22b is configured to rotate together with the output shaft 22a, and a plunger 22e is slidably inserted into the cylinder block 22b. The plunger 22e is a fixed swash plate 2 fixed to the housing 31.
2c. With the above configuration, the driving force is input to the driving shaft 21a, and the hydraulic pump 21 is driven. The hydraulic oil discharged from the hydraulic pump 21 is supplied to a hydraulic motor 22 via an oil passage plate 32, the hydraulic oil 22 is driven by the hydraulic oil, and the driving force is transmitted to an output shaft 22a.

The cylinder blocks 21b and 22b are respectively provided with valve plates 41 fixed on the oil passage plate 32.
42, and the hydraulic oil is supplied from the hydraulic pump 21 via the valve plate 41 to the main circuit 50R.5.
The hydraulic fluid flows into and out of the hydraulic circuit 22 through the valve plate 42 from the main circuits 50R and 50L. Check valves 44, 44 are connected to the main circuits 50R, 50L, respectively. When the operating oil in the main circuits 50R, 50L is insufficient, the check circuit 44, 44
Hydraulic oil is supplied via 44.

In the HST transmission 10 of the present invention, as shown in the hydraulic circuit diagrams of FIGS. 4 and 5, a switching valve 51 is interposed between the main circuits 50R and 50L. The switching valve 51 is provided to use the hydraulic pressure of the main circuits 50R and 50L as the control pressure of the hydraulic servo mechanism 71, and as shown in FIG.
0L is supplied to the throttle valve 53 via the pressure reducing valve 52 and the switching valve 51.
After that, it is configured to be supplied to the hydraulic servo circuit 70. That is, the hydraulic oil fed from the tank 62 by the charge pump 61 is supplied from the charge circuit 60 via the filter 63 and the like to the main circuit 50R / 50.
L, and the hydraulic oil of the main circuits 50R and 50L is
It is configured to be supplied to the hydraulic servo circuit 70 via the switching valve 51 and the like.

FIG. 10 shows the HST in the conventional configuration.
The hydraulic circuit diagram of FIG. In the conventional configuration, as shown in the drawing, the hydraulic pressure of the charge circuit 60 is directly supplied to the hydraulic servo circuit 70. In the case of this configuration, as described above, the efficiency of the HST is reduced, and particularly, the efficiency is significantly reduced in a low load region. Therefore, the present invention provides a hydraulic circuit that can improve the efficiency of HST.

In FIGS. 4 and 6, the switching valve 51 is composed of left and right valves 51L and 51R. The valves 51L and 51R are disposed to face each other, and spools 51a and 51a provided respectively are depressurized. Spring 51b
-It is urged by 51b to abut each other to maintain balance. The spools 51a are provided with valve oil passages 51c, respectively. The valve oil passage 51c is an oil passage formed in the longitudinal direction of the spool 51a. One end of the valve oil passage 51c communicates with the outer periphery of the spool 51a through a communication hole 51f, and the other end of the valve oil passage 51c
It communicates with the d side. Then, with the switching operation of the switching valve 51 described later, the communication hole 51f is connected to the main circuit 50R.
L or the servo communication paths 51e.

The switching operation of the switching valve 51 configured as described above will be described with reference to FIGS. First, FIG. 6 shows a case where the engine is stopped or the HST type transmission 10 maintains a neutral state. At this time, since the hydraulic pressures of the left and right main circuits 50L and 50R are substantially equal,
The left and right valves 51L and 51R do not slide and maintain the neutral position. That is, as shown in FIG. 6, the valve oil passages 51c of the left and right spools 51a are respectively connected to the main circuit 50L via the communication holes 51f.
-Although it communicates with 50R, since the respective pressures are substantially equal, the hydraulic pressure and the urging forces of the left and right pressure reducing springs 51b maintain a balance.

When the pressure of the main circuit 50R on the right side of the main circuit 50 increases, the increased pressure is:
The valve oil passage 51 of the spool 51a in the valve 51R
Through c, it enters the spring chamber 51d. On the other hand, the valve 51L
When the pressure in the spring chamber 51d on the valve 51R side overcomes the pressure reducing spring 51b of the valve 51L, the spool 51a of the valve 51R moves to the left. As a result, the spool 51a of the valve 51L is pushed leftward, and as a result, the switching valve 51 switches to the left.

As a result, the hydraulic oil of the right main circuit 50R is supplied to the spool groove 5 of the valve 51R as shown in FIG.
The oil is supplied to the hydraulic servo mechanism 71 through the servo communication path 51e through 1g. Thus, the hydraulic pressure of the main circuit 50R is used as the control pressure of the hydraulic servo circuit 70. At this time, the spool 51a on the valve 51L side has moved to a position that closes the servo communication path 51e.

When the pressure of the main circuit 50R further increases, the spool 51a of the valve 51R moves further to the left as shown in FIG. 8, and the main circuit 50R and the valve oil passage 51c of the valve 51R are shut off. . As a result, the hydraulic circuit including the spring chamber 51d and the hydraulic servo circuit 70 is shut off from the main circuit 50R. Therefore, even if the pressure of the main circuit 50R further increases, the pressure does not increase because the spring chamber 51d is disconnected from the main circuit 50R. That is, the pressure reducing spring 5
1b, the spool 51a, and the like constitute the pressure reducing valve 52. Further, when the pressure of the hydraulic servo circuit 70 decreases, the spool 51a of the valve 51R moves to the valve 51L.
Of the main 50R is supplied to the hydraulic servo circuit 70 again. That is, the hydraulic servo control pressure is kept constant by the balance between the pressure reducing spring 51b and the hydraulic pressure, no matter how high the circuit pressure of the main circuit 50R becomes.

The operation of the switching valve 51 when the left main circuit 50L rises is the same.
As the pressure of L rises, the pressure in the spring chamber 51d of the valve 51L rises, overcoming the urging force of the pressure reducing spring 51b of the valve 51R, and moving the spool 51a to the right. Thus, the hydraulic pressure of the main circuit 50L passes through the spool groove 51g of the valve 51L and passes through the servo communication path 5L.
After passing through 1e, it is supplied to the hydraulic servo circuit 70. Then, when the pressure of the main circuit 50L further increases, the spool 51a moves further rightward as shown in FIG. 9, and shuts off the main circuit 50L, the hydraulic servo circuit 70 and the spring chamber 51d of the valve 51L.

That is, as the pressure of the main circuit 50 increases, the switching valve 51 of the present invention controls the control pressure of the hydraulic servo mechanism 71 from one of the main circuits 50L and 50R via the servo communication paths 51e and 51e. Supply.
That is, the switching valve 51 switches so as to supply the control pressure from the high-pressure side main circuits 50L and 50R whose pressure has increased to the hydraulic servo mechanism 71. Furthermore, the main circuit 5
When the oil pressure of 0R (or 50L) rises, the main circuit 50R (50L) and the hydraulic servo circuit 70 are shut off, so that the function as a pressure reducing valve works, and a constant control of the hydraulic servo circuit 70 is performed. It is possible to supply pressure.

When the main circuit pressure is supplied directly to the hydraulic servo circuit 70, it is necessary to increase the strength of the oil passage, and when the oil passage is a pipe or a hose, the oil passage can withstand the pressure. Must be used, which is costly. In addition, if the contact is made with a drilled hole, it is necessary to increase the strength of the base material, and the selection of the material is limited, for example, the aluminum material cannot be used. Therefore, as described above, the pressure reducing valve is interposed between the main circuit 50 and the hydraulic servo circuit 70, so that the main circuit pressure is reduced to the required pressure and used. The freedom of design expands.

Then, as shown in FIG. 5, the control pressure supplied to the hydraulic servo circuit 70 is supplied to a hydraulic servo mechanism 71 via a three-port switching valve 72 and the like. The hydraulic servo mechanism 71 is controlled by operating the 3-port switching valve 72 with the lever 73, and the hydraulic pump 2 of the HST transmission 10 is controlled by the hydraulic servo mechanism 71.
The adjustment of the first movable swash plate 21c is performed.

As described above, in the HST type transmission 10 of the present invention, since the control pressure is supplied from the main circuit 50 to the hydraulic servo circuit 70 via the switching valve 51, the charge circuit pressure is low (for example, 4-6kg / c
m ² ) can be set.
The loss can be reduced as compared with the T-type transmission. The control flow rate of the hydraulic servo is H
The flow is supplied from the main circuit 50 of the ST-type transmission 10, but the required flow rate is insignificant compared to the operating flow rate of the HST-type transmission 10, and does not lead to a decrease in efficiency. As a result, the efficiency of the HST type transmission 10 is improved, and particularly, the efficiency at a low load is improved.

Also, since the hydraulic servo control pressure can be increased, the diameter of the servo piston can be reduced, and the hydraulic servo mechanism 7 can be used.
1 can be downsized. Further, in the present invention,
As described above, since the pressure reducing valve 52 is integrated with the switching valve 51 that supplies the control pressure to the hydraulic servo circuit 70, the structure can be simplified and a compact configuration can be achieved. The layout of the transmission 10 can be effectively designed.

Further, the main circuit pressure of the HST transmission 10 is pulsating, and if the pressure is directly supplied as the control pressure of the hydraulic servo circuit 70, the stability of the hydraulic servo mechanism 71 will be lacking. Therefore, as shown in FIGS. 5 and 6, between the main circuit 50 and the hydraulic servo circuit 70,
Since the throttle valve 53 is provided, the pulsation width is reduced, and a stable control pressure is supplied to the hydraulic servo circuit 70, so that the stability of the hydraulic servo mechanism 71 is improved.

[0029]

As described above, the integrated hydraulic continuously variable transmission according to the present invention has the following advantages. That is, since the main circuit pressure is supplied as the control pressure of the hydraulic servo mechanism via the switching valve, the circuit pressure can be supplied from the high-pressure side main circuit, and the efficiency of the hydraulic continuously variable transmission is improved. In particular, improved efficiency at low load was realized. Also, since the hydraulic servo control pressure can be increased, the diameter of the servo piston can be reduced, and the hydraulic servo mechanism can be downsized.

Further, since the main circuit pressure is supplied as the control pressure of the hydraulic servo mechanism via the switching valve and the pressure reducing valve, it is possible to prevent excessive control pressure from being supplied to the hydraulic servo circuit. As a result, the oil passage can be configured with a low-pressure pipe, and the cost and the degree of freedom in design are widened.

Further, since the switching valve and the pressure reducing valve are integrated, a compact structure can be achieved. Even when the size is limited as in the case of an integrated hydraulic continuously variable transmission, the layout design can be reduced. It became easy. Also, the number of parts can be reduced, and the cost can be reduced.

Since the main circuit pressure is supplied as the control pressure of the hydraulic servo mechanism via the pressure reducing valve and the throttle valve, the pulsation width of the main circuit pressure can be reduced, and the stability of the hydraulic servo mechanism can be reduced. It is possible to improve the performance.

[Brief description of the drawings]

FIG. 1 is a side view of a work vehicle.

FIG. 2 is a side view of the same.

FIG. 3 is a side sectional view of the HST type transmission.

FIG. 4 is a front sectional view of the same.

FIG. 5 is an HST hydraulic circuit diagram of the present invention.

FIG. 6 is a plan sectional view of the HST type transmission showing a switching valve.

FIG. 7 is a partially enlarged sectional view of a switching valve.

FIG. 8 is a plan sectional view of the HST type transmission showing the switching valve.

FIG. 9 is a plan sectional view of the HST type transmission showing the switching valve.

FIG. 10 is a hydraulic circuit diagram of a conventional HST.

[Explanation of symbols]

 Reference Signs List 10 HST transmission 21 Hydraulic pump 22 Hydraulic motor 50 Main circuit 51 Switching valve 52 Pressure reducing valve 53 Throttle valve 60 Charge circuit 70 Hydraulic servo circuit

Claims (4)

[Claims] 1. An integrated hydraulic continuously variable transmission having a hydraulic servo mechanism for controlling a movable swash plate angle, wherein a main circuit pressure is supplied as a control pressure of the hydraulic servo mechanism via a switching valve. A control structure for supplying a control pressure of a hydraulic servo mechanism in a hydraulic continuously variable transmission. 2. In an integrated hydraulic continuously variable transmission having a hydraulic servo mechanism for controlling a movable swash plate angle, a main circuit pressure is supplied as a control pressure of a hydraulic servo mechanism via a switching valve and a pressure reducing valve. A control structure for supplying hydraulic servo mechanism control pressure in a hydraulic continuously variable transmission, characterized in that: 3. The supply structure for controlling pressure of a hydraulic servo mechanism in a hydraulic continuously variable transmission according to claim 2, wherein the switching valve and the pressure reducing valve are integrated. 4. An integrated hydraulic continuously variable transmission having a hydraulic servo mechanism for controlling a movable swash plate angle, wherein a main circuit pressure is supplied as a control pressure of the hydraulic servo mechanism via a pressure reducing valve and a throttle valve. A control structure for supplying a hydraulic servo mechanism control pressure in a hydraulic continuously variable transmission, characterized by having a configuration.