JP2009275875A - Hydraulic pressure retaining device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic pressure retaining device which can be provided on an HST vehicle with suppressing increase in production cost of the HST vehicle and increase in size of a hydraulic pressure circuit of the HST vehicle. <P>SOLUTION: The hydraulic pressure retaining device includes a hydraulically piloted negative type parking brake 51 constituting a parking brake as one of hydraulically actuated sections installed on the HST vehicle and releasing the brake of an oil hydraulic motor 24 for travel by using a charge pressure as a release pressure, a change-over valve 52 capable of switching fluid communication/shutoff between a charge circuit 30 and the release pressure of the negative type parking brake 51 and a check valve 53 which prevents pressured oil from flowing in the direction from an oil passage 40 toward the charge circuit 30. When the charge pressure falls down, the negative type parking brake 51 is used as a hydraulic power source to retain the pressure in the oil passage 40. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is provided in an HST vehicle having a hydraulic operation section that operates by receiving charge pressure from a charge circuit directly or indirectly, and the pressure of an oil passage that guides the charge pressure from the charge circuit to the hydraulic operation section. The present invention relates to a hydraulic pressure holding device that holds when a charge pressure is lowered.

  The hydraulic circuit of an HST vehicle such as a wheel loader, a rolling machine, or an agricultural vehicle includes an HST circuit in which a hydraulic pump and a traveling hydraulic motor are connected in a closed circuit, and a charge pump driven by a prime mover. A charge circuit that supplies hydraulic oil and a plurality of hydraulic operation sections that operate by receiving charge pressure from the charge circuit directly or indirectly. There are negative clutches and negative parking brakes that act by receiving charge pressure directly, and negative pressure brakes that act indirectly by receiving charge pressure. There are control valves that operate by receiving a control pressure generated as a primary pressure.

  The charge pressure decreases when a large amount of hydraulic oil is replenished from the charge circuit to the HST circuit, or when the charge pump is stopped due to a stop due to an abnormality of the prime mover. As a result, if the charge pressure supplied to the hydraulic operating unit becomes too low, a malfunction occurs in the operation of the hydraulic operating unit.

  Therefore, conventionally, a hydraulic pressure holding device is provided in the oil passage derived from the charge circuit to apply the charge pressure to the hydraulic operation section, and the pressure in the oil passage is held when the charge pressure is reduced. Yes. The conventional hydraulic pressure holding device has a check valve and an accumulator provided in the oil passage. The check valve is provided on the charge pump side of the accumulator, and prevents the flow of pressure oil in the direction from the oil passage toward the charge circuit.

  In the conventional hydraulic pressure holding device configured as described above, when the charge pressure is reduced, the check valve prevents the flow of pressure oil in the direction from the hydraulic operating portion toward the charge pump, and the accumulator serves as the hydraulic pressure source, The pressure is maintained. Thereby, it is possible to prevent malfunctions in the hydraulic operating part.

For this type of conventional hydraulic pressure holding device, see Patent Document 1.
JP 2001-324014 A

  The above-described conventional hydraulic pressure holding device has a check valve and an accumulator provided in an oil passage derived from a charge circuit, and increases the manufacturing cost of an HST vehicle by the amount of these check valve and accumulator. become. In addition, there is a problem that the hydraulic circuit of the HST vehicle is enlarged by providing the accumulator.

  The present invention has been made in consideration of the above-mentioned problems, and provides a hydraulic holding device that can be provided in an HST vehicle while suppressing an increase in the manufacturing cost of the HST vehicle and an increase in the size of the hydraulic circuit of the HST vehicle. It is in.

  The present invention is configured as follows to achieve the above-described object.

[1] The present invention relates to an HST circuit in which a hydraulic pump and a traveling hydraulic motor are connected in a closed circuit, a charge circuit for supplying discharge oil of a charge pump to the low pressure side of the HST circuit, and a charge pressure of the charge circuit. Pressure of an oil passage provided in an HST vehicle having a plurality of hydraulic operation units that operate by receiving pressure directly or indirectly, and derived from the charge circuit to apply the charge pressure to the hydraulic operation unit In a hydraulic pressure holding device that holds the charge pressure when the charge pressure is reduced, and is a negative type that is one of the plurality of hydraulic operation units, receives the charge pressure as a release pressure, and releases the braking of the traveling hydraulic motor A parking brake, a switching valve capable of switching communication / blocking between the charge circuit and the negative parking brake, and from the oil passage to the charge circuit And having a check valve which prevents the flow of pressure oil countercurrent.

  In the present invention described in “[1]”, when the switching valve communicates the charge circuit and the negative parking brake, the negative parking brake uses the charge pressure as a release pressure to brake the traveling hydraulic motor. It is in a released state. In this state, when the charge pressure decreases, the flow of pressure oil in the direction from the oil path to the charge circuit is blocked by the check valve, and the negative parking brake serves as a hydraulic pressure source to maintain the pressure in the oil path.

  The negative parking brake as the hydraulic pressure source is one of a plurality of hydraulic operating parts already installed in the hydraulic circuit of the HST vehicle. Therefore, it is not necessary to add a hydraulic device as a hydraulic source such as an accumulator in the above-described conventional hydraulic holding device to the hydraulic circuit of the HST vehicle. Accordingly, it is possible to realize a hydraulic pressure holding device that can be provided in the HST vehicle while suppressing an increase in manufacturing cost of the HST vehicle and an increase in the size of the hydraulic circuit of the HST vehicle.

[2] The present invention is characterized in that, in the invention described in “[1]”, a throttle provided in parallel with the check valve is provided.

  An excessive pressure may be generated on the hydraulic operating unit side of the check valve, such as a peak pressure due to pressure fluctuation during travel of the HST vehicle. According to the present invention described in “[2]”, the excessive pressure can be released by the restriction. Thereby, it can avoid that the excessive pressure is provided to a hydraulic action part, and can contribute to ensuring of the reliability of a hydraulic action part.

  Further, the throttle gently releases the release pressure to the charge circuit side when the pressure on the charge circuit side is lower than the release pressure of the negative parking brake. As a result, even if the switching valve fails and does not move with the charge circuit and the negative parking brake communicating, the negative parking brake is braked by stopping the charge pump and reducing the pressure on the charge circuit side. The stop state of the HST vehicle can be safely maintained.

  According to the present invention, it is possible to provide a hydraulic pressure holding device that can be provided in an HST vehicle while suppressing an increase in the manufacturing cost of the HST vehicle and an increase in the size of the hydraulic circuit of the HST vehicle.

  FIG. 1 is a side view showing a wheel loader as an example of an HST vehicle to which a hydraulic pressure holding device according to an embodiment of the present invention is applied.

  As shown in FIG. 1, the wheel loader 1 includes a driver's cab 2, a work machine 3 used for excavation work and the like, and front wheels 9 and rear wheels 10.

  The work machine 3 includes a lift arm 4 coupled to the front portion of the wheel loader 1 so as to be pivotable in the vertical direction, and a bucket 5 coupled to the tip of the lift arm 4 so as to be pivotable. The lift arm 4 is driven by a lift arm cylinder 6 (hydraulic cylinder). The bucket 5 is driven by the operation of the bucket cylinder (hydraulic cylinder) being transmitted by the bell crank 8.

  The front wheel 9 and the rear wheel 10 are each provided on an axle (not shown), and are driven by being transmitted with the power of a drive shaft (not shown). The drive shaft is driven by transmitting the power of a traveling hydraulic motor 24 of the HST circuit 20 described later.

[First Embodiment]
FIG. 2 is a hydraulic circuit diagram showing a hydraulic pressure holding device, an HST circuit, and a charge circuit according to the first embodiment of the present invention.

  The HST circuit 20 is a closed circuit via a prime mover 21, a bi-tilting variable displacement hydraulic pump 22 driven by the prime mover 21, and a pair of main pipes 23 </ b> A and 23 </ b> B. And a traveling hydraulic motor 24 connected thereto.

  The HST circuit 20 is provided with a charge circuit 30 for supplying hydraulic oil to the low pressure side of the main pipelines 23A and 23B. The charge circuit 30 includes a charge pump 31 and a bifurcated charge line 32 connecting the charge pump 31 and the main lines 23A and 23B. Check valves 35A and 35B are provided on the branch pipes 34A and 34B of the charge pipe 32, respectively. The check valve 35A defines the flow direction of the pressure oil in the branch pipe line 34A in the direction from the charge pump 31 toward the main pipe line 23A. The check valve 35B defines the flow direction of the pressure oil in the branch pipe line 34B in the direction from the charge pump 31 toward the main pipe line 23B. The main conduit 33 of the charge conduit 32 is provided with a relief valve 36 that regulates the pressure between the charge pump 31 and the check valves 35A and 35B, that is, the charge pressure.

  An oil passage 40 is led out between the check valves 35 </ b> A and 35 </ b> B of the charge circuit 30. The oil passage 40 branches from the trunk oil passage 41 into a plurality of branch oil passages. Each of the plurality of branch oil passages is directly or indirectly connected to each of the hydraulic operation sections that operate by receiving the hydraulic pressure. A branch oil passage 42, which is one of these branch oil passages, is connected to a release pressure chamber 51 e of a negative parking brake 51 that can brake the traveling hydraulic motor 24. The branch oil passage 42 is provided with a switching valve 52 capable of switching communication / blocking between the charge circuit 30 and the release pressure chamber 51e of the negative parking brake 51. The negative parking brake 51 is a hydraulic operation part that operates by receiving pressure directly through the switching valve 52 using the charge pressure as a release pressure.

  The negative parking brake 51 includes a rotor 51a that rotates integrally with the output shaft of the traveling hydraulic motor 24, a pad 51b that can move away from the rotor 51a, a piston 51c that is integral with the pad 51b, a piston The spring 51d presses the pad 51b against the rotor 51a via the 51c, and the release pressure chamber 51e for introducing the release pressure that presses the piston 51c against the spring 51d. When the release pressure is introduced into the release pressure chamber 51e, the piston 51c moves against the spring 51d, and accordingly, the pad 51b is separated from the rotor 51a, and the braking of the traveling hydraulic motor 24 is released. If the pressure in the release pressure chamber 51e does not reach the release pressure, the pad 51b is pressed against the rotor 51a via the piston 51c by the spring 51d, and the traveling hydraulic motor 24 is braked.

  The switching valve 52 is a spring return type valve that is electrically operated, and operates when supplied with electric power via an electric switch 54. The electric switch 54 is provided in the cab 2 of the wheel loader 1 so as to be manually operable. In the switching valve 52 operated by being supplied with electric power, the valve position is switched from the normal position N where the charge circuit 30 and the release pressure chamber 51e of the negative parking brake 51 are disconnected from each other to the operating position A where the communication is established. . FIG. 2 shows a state where the valve position of the switching valve 52 is the normal position N. In this state, the release pressure chamber 51e of the negative parking brake 51 and the hydraulic oil tank 37 communicate with each other, and the pressure in the release pressure chamber 51e is the tank pressure.

  Further, branch oil passages other than the branch oil passage 42 are not shown, but are provided in a negative clutch, a service brake, a hydraulic pilot control valve, etc., which are hydraulic operation parts different from the negative parking brake 51. It is connected. Similarly to the negative parking brake 51, the negative clutch is a hydraulic operating part that directly receives and operates the charge pressure. The control valve is a hydraulic operating part that receives a control pressure generated by a pilot valve using a charge pressure as a primary pressure, that is, receives a charge pressure indirectly, and operates, for example, a steering cylinder (not shown). A control valve for controlling the flow of pressure oil supplied to the lift arm cylinder 6, a control valve for controlling the flow of pressure oil supplied to the lift arm cylinder 6, and a control valve for controlling the flow of pressure oil supplied to the bucket cylinder 7. . In FIG. 2, the negative clutch, the service brake, the control valve, and the like are collectively used as another hydraulic operation unit 60, and branch oil passages other than the branch oil passage 42 are collectively used as another branch oil passage 43. The diagram is simplified.

  Further, a check valve 53 is provided in the trunk oil passage 41 of the oil passage 40 to block the flow of pressure oil in the direction from the oil passage 40 toward the charge circuit 30.

  The hydraulic pressure holding device 50 according to the first embodiment is configured to include the negative parking brake 51, the switching valve 52, and the check valve 53.

  The operation of the hydraulic pressure holding device 50 configured as described above will be described together with the operations of the HST circuit 20 and the charge circuit 30.

  When the variable displacement hydraulic pump 22 and the charge pump 31 are driven by the prime mover 21, pressure oil is supplied to the traveling hydraulic motor 24 via the main line 23A or 23B and a charge pressure is generated in the charge circuit 30. .

  When the electric switch 54 is turned on and the switching valve 52 is activated, the charge circuit 30 and the release pressure chamber 51e of the negative parking brake 51 communicate with each other via the switching valve 52, and the charge pressure is supplied to the release pressure chamber 51e. . As a result, the negative parking brake 51 operates using the charge pressure as the release pressure, and releases the braking of the traveling hydraulic motor 24. Accordingly, the traveling hydraulic motor 24 is permitted to be driven by the pressure oil from the variable displacement hydraulic pump 22.

  When the pressure on the low pressure side of the main pipelines 23A, 23B becomes lower than the charge pressure, the discharge oil of the charge pump 31 is supplied to the low pressure side main pipeline 23A or 23B through the check valve 35A or 35B.

  The charge pressure decreases when a large amount of hydraulic oil is replenished from the charge circuit 30 to the HST circuit, or when the charge pump 31 is stopped due to a stop due to an abnormality of the prime mover 21. When the charge pressure decreases, the flow of pressure oil in the direction from the oil passage 40 toward the charge circuit 30 is blocked by the check valve 53, the negative parking brake 51 serves as a hydraulic pressure source, and the oil passage on the downstream side of the check valve 53 A pressure of 40 is maintained.

  According to the hydraulic pressure holding device 50 according to the first embodiment, the following effects can be obtained.

  In the hydraulic pressure holding device 50 according to the first embodiment, the negative parking brake 51 as a hydraulic pressure source is one of a plurality of hydraulic operating portions already installed in the hydraulic circuit of the wheel loader 1. Therefore, it is not necessary to add a hydraulic device as a hydraulic source such as an accumulator in the conventional hydraulic holding device described above to the hydraulic circuit of the wheel loader 1. Thereby, it is possible to realize a hydraulic pressure holding device that can be provided in the wheel loader 1 while suppressing an increase in manufacturing cost of the wheel loader 1 and an increase in the size of the hydraulic circuit of the wheel loader 1.

  In the description of the first embodiment, the wheel loader 1 is taken as an example of an HST vehicle to which the hydraulic pressure holding device 50 is applied. However, the HST vehicle to which the present invention is applied is not limited to a wheel loader. Alternatively, it may be a rolling machine or an agricultural vehicle.

[Second Embodiment]
FIG. 3 is a hydraulic circuit diagram showing a hydraulic pressure holding device, an HST circuit and a charge circuit according to the second embodiment of the present invention.

  Unlike the hydraulic pressure holding device 50 according to the first embodiment, the hydraulic pressure holding device 70 according to the second embodiment includes a check valve 53 and a throttle 72 provided in parallel to the check valve 53. Although not shown, the check valve 53 and the throttle 72 are provided together in one valve block to constitute a slow return valve 71.

  On the downstream side of the check valve 53, excessive pressure may be generated with respect to another hydraulic operating unit 60 such as a peak pressure due to pressure fluctuation during traveling of the wheel loader 1. In the hydraulic pressure holding device 70 according to the second embodiment, the excessive pressure is released to the charge circuit 30 side by the throttle 72. The charge circuit 30 discharges the excessive pressure to the hydraulic oil tank 37 by the relief valve 36.

  According to the hydraulic pressure holding device 70 according to the second embodiment, the following effects can be obtained.

  In the hydraulic pressure holding device 70 according to the second embodiment, when excessive pressure is generated on the downstream side of the check valve 53 by the throttle 72, the excessive pressure can be released to the charge circuit 30 side. As a result, it is possible to avoid applying an excessive pressure to another hydraulic operating unit 60, and to contribute to ensuring the reliability of another hydraulic operating unit 60.

  In addition, the throttle 72 gently releases the release pressure to the charge circuit 30 side when the pressure on the charge circuit 30 side is lower than the release pressure of the negative parking brake 51. As a result, even when the switching valve 52 fails and does not move in a state where the charge circuit 30 and the release pressure chamber 51e of the negative parking brake 51 are in communication, the charge pump 31 is stopped together with the prime mover 21, and the charge circuit 30 side By reducing the pressure, the negative parking brake 51 can be brought into a braking state, and the stopped state of the wheel loader 1 can be safely maintained.

1 is a side view showing a wheel loader as an example of an HST vehicle to which a hydraulic holding device according to an embodiment of the present invention is applied. 1 is a hydraulic circuit diagram illustrating a hydraulic pressure holding device, an HST circuit, and a charge circuit according to a first embodiment of the present invention. FIG. 6 is a hydraulic circuit diagram showing a hydraulic pressure holding device, an HST circuit, and a charge circuit according to a second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wheel loader 2 Driver's cab 3 Working machine 4 Lift arm 5 Bucket 6 Lift arm cylinder 7 Bucket cylinder 8 Bell crank 9 Front wheel 10 Rear wheel 20 HST circuit 21 Motor | power_engine 22 Variable capacity | capacitance type hydraulic pump 23A, 23B Main line 24 Traveling hydraulic motor 30 charge circuit 31 charge pump 32 charge line 33 trunk line 33A, 33B branch line 34A, 34B check valve 35 relief valve 36 hydraulic oil tank 40 oil path 41 trunk oil path 42 branch oil path 43 another branch oil path 50 Hydraulic holding device 51 Negative parking brake 51a Rotor 51b Pad 51c Piston 51d Spring 51e Release pressure chamber 52 Switching valve 53 Electric switch 60 Another hydraulic operating part

70 Hydraulic holding device 71 Slow return valve 72 Restriction

Claims (2)

An HST circuit in which a hydraulic pump and a traveling hydraulic motor are connected in a closed circuit, a charge circuit that supplies discharge oil of the charge pump to the low-pressure side of the HST circuit, and a charge pressure of the charge circuit is directly or indirectly received. Provided in an HST vehicle having a plurality of hydraulic operating parts that operate in the same manner, and the pressure of an oil passage derived from the charge circuit for applying the charge pressure to the hydraulic operating part is reduced. In the hydraulic holding device that holds sometimes,
A negative parking brake that receives one of the charge pressures as a release pressure and releases the braking of the traveling hydraulic motor; and the charge circuit and the negative parking brake. A hydraulic holding device, comprising: a switching valve capable of switching between communication and interruption between the two and a check valve for preventing a flow of pressure oil in a direction from the oil passage toward the charge circuit.   2. The hydraulic holding device according to claim 1, further comprising a throttle provided in parallel with the check valve.

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