JP2001295813A - Hydraulic circuit for work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that energy loss is not improved in a conventional hydraulic circuit for a work machine using an accumulator device and a booster device to operate a conventional hydraulic actuator. SOLUTION: In an oil pressure supply circuit of a work vehicle switching pressure oil from a hydraulic pump 31 by operating a change-over valve 34 to supply it to the hydraulic actuator 11, an unload branch oil passage 35 for returning oil into an oil tank is provided at a pump outlet, a check valve 33 is provided between a branch position and the change-over valve, and the accumulator device 40 or the booster device 50 operating at an oil pressure exceeding a predetermined pressure is connected between the check valve and the change-over valve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a pressure accumulator or a pressure intensifier between a pump of a working machine having a hydraulic actuator and a switching valve to reduce noise during work and reduce a load on a prime mover to save energy. Related to the technology to achieve.

[0002]

2. Description of the Related Art Conventionally, in a device equipped with a hydraulic actuator such as a backhoe or a loader, in order to operate the hydraulic actuator, a switching valve is switched by an operating tool such as an operating lever to supply hydraulic oil to the hydraulic actuator. Work machine to operate. During operation, a relief valve is used in a hydraulic oil supply circuit to keep the hydraulic pressure applied to the hydraulic actuator at a high pressure and to protect the hydraulic equipment from excessive hydraulic pressure.

[0003] For example, as shown in FIG.
Drives a hydraulic pump 21 for driving a hydraulic actuator and an auxiliary hydraulic pump 22 serving as a hydraulic source for charging and pilot operation. A pilot-operated switching valve 23 is connected to the output side of the hydraulic pump 21, and the switching is performed. A hydraulic cylinder 24 is connected to the secondary side of the valve 23 as a hydraulic actuator.

[0004] An oil passage for draining to an oil tank 25 is connected to a tank port on the primary side of the switching valve 23, and an oil passage to the oil tank 25 and an output side of the main hydraulic pump 21 are provided between the oil passage and the output side of the main hydraulic pump 21. When the relief valve 26 is connected and a hydraulic pressure equal to or higher than the set pressure is applied to the oil supply path to the hydraulic actuator, the relief valve 26 opens to drain the excess hydraulic pressure and maintain the set pressure.

The output side of the auxiliary hydraulic pump 22 is connected to a switching valve 27 for operation.
The switch 7 can be switched with a small force by operating an operating lever. The output port of the switching valve 27 is connected to the operating port of the switching valve 23. Then, a relief valve 28 is interposed between the output side of the auxiliary hydraulic pump 22 and the oil passage to the oil tank 25 to set the upper limit hydraulic pressure of the pilot circuit.

In such a hydraulic circuit configuration, for example, when excavation work is performed by applying a hydraulic actuator to a backhoe, the switching valve 23 is switched so as to reduce the hydraulic cylinder 24, and the bucket reaches hard rock or a stroke end. In such a case, the upper limit hydraulic pressure of the main hydraulic circuit is reached, the relief valve 26 is switched, and the hydraulic pressure higher than the set value is drained. Since the throttle is throttled when draining through the relief valve 26, a load is applied to the main hydraulic pump 21, a large loss of hydraulic energy occurs, and the oil temperature rises. In order to lower the oil temperature, an oil cooler, a fan and the like have been required.

As a technique for reducing the oil pressure loss due to relief by connecting an accumulator in the middle of a supply oil passage for such a structure, the technique of Japanese Utility Model Publication No. 63-12207 is known. There is also known a technique in which a pressure increasing circuit is connected in parallel between a hydraulic actuator and a switching valve so that work can be performed efficiently. For example, the techniques disclosed in JP-A-7-269507 and JP-A-8-93708.

[0008]

However, in the case of the former technique, since the Prada-type accumulator is used, it is difficult to control the stored energy, and the hydraulic circuit is complicated. In addition, only one of the head side and the rod side of the hydraulic cylinder detects the pressure,
It could only be reduced during one-way operation. In addition, the latter technique is a technique for assisting torque, and is not for suppressing energy loss. Therefore, the present invention is to provide a simple hydraulic circuit configuration and energy saving by using a pressure accumulating device or a pressure increasing device.

[0009]

The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described. That is, in claim 1, in a hydraulic supply circuit of a working vehicle that switches hydraulic oil from a hydraulic pump by operating a switching valve and supplies the hydraulic actuator to an hydraulic actuator, an unload branch oil passage returning to an oil tank is provided at a pump outlet, A check valve was provided between the branch position and the switching valve, and a pressure accumulator operating at a predetermined oil pressure or higher was connected between the check valve and the switching valve.

According to a second aspect of the present invention, in a hydraulic supply circuit of a working vehicle for switching hydraulic oil from a hydraulic pump by operating a switching valve and supplying the hydraulic oil to a hydraulic actuator, an unload branch oil passage returning to an oil tank at a pump outlet. And a check valve is provided between the branch position and the switching valve, and a pressure increasing device is connected between the check valve and the switching valve.

According to a third aspect of the present invention, the unload branch oil passage is provided with an unload valve that is operated by a supply pressure to the actuator.

According to a fourth aspect of the present invention, the supply pressure to the actuator is detected by pressure detection means, and an unload valve is provided in the unload branch oil passage, and the unload valve is operated by the output of the pressure detection means. I opened and closed it.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings. 1 is an overall side view of a backhoe, FIG. 2 is a hydraulic circuit diagram using a pressure accumulator of the present invention, and FIG.
Is a cross-sectional view showing an embodiment of the pressure accumulator, FIG. 4 is a hydraulic circuit diagram using the pressure booster of the present invention, FIG. 5 is a cross-sectional view showing an embodiment of the pressure booster, FIG. 6 is a conventional hydraulic circuit diagram, FIG. 7 is a diagram showing output changes of a hydraulic pump and a prime mover when the pressure booster of the present invention is applied, and FIG. 8 is a diagram showing output changes of a conventional motor.

A case where the hydraulic circuit of the present invention is applied to a backhoe will be described. First, the overall configuration of the backhoe will be described with reference to FIG. A turning frame 2 is attached to the upper part of a crawler type traveling device 1 equipped with a pair of right and left crawlers so as to be able to turn, and an earth discharging plate 3 protrudes forward. A tank and the like are arranged and covered by the hood 14. A seat is arranged substantially at the center of the front and rear of the revolving frame 2, and a cabin 8 covers a steering unit such as an operation lever for operating the steering and working machine disposed at the front of the seat and the seat.

An attachment portion 2a is provided at the front left and right center of the revolving frame 2 to pivotally support a base of an excavating machine 7. The excavating machine 7 includes a bucket 4, an arm 5, a boom 6, The base of the boom 6 is pivotally supported by a boom bracket 12 so as to be able to rotate back and forth, and the boom bracket 12 is rotatable left and right at the front left and right center of the turning frame 2. It is supported and can be rotated left and right by a swing cylinder 17. A boom cylinder 11 is interposed between the boom 6 and the boom bracket 12, so that the boom 6 can be turned up and down. An arm cylinder 10 is interposed between the boom 6 and the arm 5 rotatably attached to the tip of the boom 6, and allows the arm 5 to rotate back and forth. A bucket cylinder 9 is interposed between the arm 5 and the bucket 4 pivotally supported at the tip of the arm 5, so that the bucket 4 can be scooped and rotated.

An embodiment of the hydraulic circuit of the present invention in which the boom cylinder 6 is a hydraulic actuator will be described with reference to FIG. The hydraulic pump 31 is driven by the engine 20 serving as a prime mover, and sucks and pumps hydraulic oil filled in the oil tank 25. An unload branch oil passage 35 is provided on the discharge side of the hydraulic pump 31 and connected to the oil tank 25, and an unload valve 36 is interposed in the unload branch oil passage 35. The unload valve 36 is composed of a 2-port 2-position switching electromagnetic valve having a communication position C and a block position D.

A check valve 33 is connected to the discharge side of the hydraulic pump 31, and a switching valve 34 is connected to the secondary side of the check valve 33. The switching valve 34 is provided with an operating lever provided in the cabin 8 By operating the switch valve, the switching valve 34 is switched.
A boom cylinder 11 is connected to the secondary side of the boom cylinder. When the switching valve 34 is switched to the A side by operating the operation lever, the boom cylinder 11 is contracted, and the boom 6 is rotated downward to perform excavation work or the like. When the switching valve 34 is switched to the B side by operating in the opposite direction, the boom cylinder 11
, And the boom 6 can be pivoted upward to perform a lifting operation or the like.

A pressure switch 37 is disposed in the oil passage 39 of the check valve 33 and the switching valve 24 as a pressure detecting means. The pressure switch 37 is connected to a solenoid 36a of the unload valve 36, When the pressure switch 37 is turned on, the solenoid 36a is activated and the unload valve 36 is switched.

A pressure accumulator (spring accumulator) 40 is connected to an oil passage 39 between the check valve 33 and the switching valve 34. The pressure accumulator 40 is configured, for example, as shown in FIG. A piston 42 is slidably housed in a case 41, and a room on one side separated by the piston 42 in the case 41 communicates with a supply oil passage 41a, and a spring 43 and an adjusting plate 44 are provided in a room on the other side. The adjustment plate 44 is provided with an adjustment bolt 4 screwed into the case 41.
5 is rotated to adjust the spring pressure (cracking pressure) P1.

In such a configuration, for example, when the switching valve 34 is switched to the A side so as to lower the boom 6, the pressure oil from the hydraulic pump 31 causes the check valve 33,
It is supplied to the boom cylinder 11 via the switching valve 34 to reduce the size. Check valve 33 and switching valve 34
When the oil pressure in the oil passage 39 during the period reaches the set pressure P1, the piston 42 in the pressure accumulating device 40 slides and starts accumulating pressure.
The set oil pressure P1 can be changed by rotating the adjustment bolt 45.

The oil pressure in the oil passage 39 is equal to the set pressure P1.
When the pressure accumulates after the pressure accumulates, since the pressure accumulator 40 is of a spring type, the pressure in the oil passage 39 further increases while accumulating the pressure. When the circuit upper limit set pressure P2 (P2> P1) is reached, the pressure switch 37 is turned on, the solenoid 36a is operated, and the unload valve 36 is switched to the C position.
A communication state is established between the hydraulic pump 31 and the oil tank 25,
The hydraulic pump 31 is operated under no load, the noise is reduced, and the generation of heat is suppressed. The circuit upper limit set pressure P2 corresponds to a conventional relief pressure.

On the other hand, in the oil passage 39, when the boom cylinder 11 is further reduced, pressure oil is supplied from the pressure accumulator 40 to the boom cylinder 11 at the set pressure P2.
Then, the spring 43 in the pressure accumulator 40 is extended and the piston 4
2 slides to the longest stroke position, the oil pressure in the oil passage 39 drops below P1, and when the pressure reaches the set pressure P1, the pressure switch 37 is turned off and the unload valve 36
The position is switched to the position, the unload branch oil passage 35 is blocked, and the pressure oil from the hydraulic pump 31 is supplied to the check valve 3.
3 to the oil passage 39 and again the boom cylinder 1
When the oil pressure is equal to or higher than the set pressure P1, the oil is also sent to the pressure accumulator 40 and accumulated. The above operation is repeated in this manner.

The same operation is performed when the switching valve 34 is switched to the B side. When the boom cylinder 11 is returned to the neutral position, the boom cylinder 11 is maintained at that position, and the pressure accumulator 40
The working oil in the tank is drained to the oil tank 25. In addition, the same circuit can be applied to the bucket cylinder 9, the arm cylinder 10, and other hydraulic actuators, and the drain can be drained without load instead of the relief valve at the time of work, thereby improving the heat balance and saving energy. It can also be made.

Next, a hydraulic circuit configuration for saving energy by using the pressure increasing device 50 will be described. In FIG. 4, an unload branch oil passage 35 is provided on the discharge side of the hydraulic pump 31 and connected to the oil tank 25, and an unload valve 51 is interposed in the unload branch oil passage 35. A check valve 33 is connected to the discharge side of the hydraulic pump 31, a switching valve 52 is connected to a secondary side of the check valve 33, and a boom cylinder 11 is connected to a secondary side of the switching valve 52 as a hydraulic actuator. Have been. The switching valve 52 is constituted by a pilot operated switching valve, and pilot oil passages 54a and 54b connected to the secondary side of the pilot operated switching valve 53 are connected to the operation input ports. An operation section for switching the pilot operation switching valve 53 is connected to an operation lever provided in the cabin 8, and can be switched by operating the operation lever.

An oil passage 54 between the check valve 33 and the switching valve 52 has a control oil passage 55 for switching the unload valve 51 and an oil passage 5 communicating with the pressure increasing device 50.
6 are connected. The unload valve 51 sets an upper limit pressure X for driving the hydraulic actuator.

A pilot operation switching valve 53 is provided on the discharge side of the auxiliary hydraulic pump 57 for generating pilot pressure.
And the relief valve 59 for setting the upper limit of the pilot pressure
The secondary side of the relief valve 59 is connected to the oil tank 25 via the pressure increasing device 50.

The pressure intensifier 50 is constructed, for example, as shown in FIG. A piston 61 having a convex shape in cross section, a spring 62 for returning the piston 61, and a piston 6 having a “D” shape in cross section for applying a force to the piston 61 in the case 60.
3 are stored. Small diameter portion 61a of the piston 61
Is disposed facing the oil passage 56, and the large-diameter portion 61 b communicates with the secondary side of the relief valve 59, and further abuts on the tip 63 a of the piston 63. The piston 6
The rear end 63b of the third cylinder 3 communicates with a spring chamber 65 containing the piston 61 and the spring 62 via an oil passage 64 and a check valve 67. The oil passage 64 communicates with the oil tank 25 via a relief valve 66. The land 63c of the piston 63 communicates with the oil tank 25.

In such a configuration, when the pilot operation switching valve 53 is switched to the E side by operating the operation lever, the pressure oil from the auxiliary hydraulic pump 57 is supplied to the switching valve 52 via the pilot operation switching valve 53 and the oil passage 54b. , The switching valve 52 is switched to the B side, the boom cylinder 11 is extended, and the boom 6 is pivoted upward to perform a lifting operation or the like. When the operation lever is operated in the reverse direction to switch the pilot operation switching valve 53 to the F side, oil is supplied to the oil passage 54a and the switching valve 52 is set to the A position.
Side, the boom cylinder 11 is contracted, and the boom 6 is rotated downward to perform a digging operation or the like.

When the boom cylinder 11 is extended or retracted, the relief valve 5
When the pressure is increased from the set pressure P4 of FIG. 9, pressure oil is supplied to the large diameter portion 61b of the pressure intensifier 50, and the piston 61
Slide. Due to this sliding, the pressure oil in the oil passage 56 facing the small diameter portion 61a is pushed out and the boom cylinder 1
1 is further expanded or contracted. That is, a hydraulic pressure output is obtained which is inversely proportional to the area of the small diameter portion 61a and the large diameter portion 61b at both ends of the piston 61. For example, if the area of the small diameter portion 61a is S1 and the area of the large diameter portion 61b is S2, the pressure P6 on the large diameter portion 61b is S2 / S
The pressure is increased by a factor of one and output from the small diameter portion 61a.

This output is set to be equal to the upper limit pressure of the circuit. The piston 61 slides (forward, FIG. 5).
In the right direction), and the large-diameter portion 61b
When the pressure exceeds 0, the pressure oil passes through the passage 70 and the check valve 67.
, The piston 63 slides, and the land 63 c is connected to the pressure oil chamber 71. Since the land 63c is connected to the oil tank,
The pressure oil in the pressure oil chamber 71 is drained to the tank, and the piston 6
1 returns to the initial position by the force of the spring 62. At this time, the piston 61 pushes back the piston 63, and the pressure oil chamber is closed again. The oil in the passage 64 is pushed back by the force of the spring 62 and is drained through the relief valve 66. At this time, the oil in the passage 64 does not flow into the passage 70 because the check valve 67 is provided. When the oil in the pressure oil chamber 71 is drained, the piston 61 returns to the initial position by the force of the spring 62. At this time, the oil is sucked into the oil passage 56 via the check valve 72. The above operation is repeated in this manner. When the oil pressure in the oil passage 54 rises and reaches the upper limit pressure of the circuit, the unload valve 51 is switched by the pressure in the control oil passage 55, and the communication between the hydraulic pump 31 and the oil tank 25 is established. The pump 31 is in the no-load operation.

On the other hand, in the oil passage 56, when the boom cylinder 11 is further reduced, pressure oil is supplied from the pressure increasing device 50 to the boom cylinder 11 at the set pressure X. Further, the piston 61 in the pressure increasing device 50 moves forward to
When the pressure 1b exceeds the position of the passage 70 and the oil in the pressure oil chamber 71 is drained, the piston 61 returns to the initial position.
And the oil pressure in the oil passage 54 decreases, but the oil pressure in the control oil passage 55 also decreases, so that the unload valve 51 is switched to the block position, and the hydraulic oil from the hydraulic pump 31 passes through the check valve 33 to the oil passage 54. The oil is sent to the boom cylinder 11 again. When the piston 61 in the pressure increasing device 50 returns to the initial position and the pressure increasing effect starts working again, the oil pressure in the oil passages 56 and 54 increases, the unload valve 51 is switched, and the hydraulic pump 31 switches to the no-load operation again. Become. The above operation is repeated in this manner.

When the operation lever is rotated to switch the pilot operation switching valve 53 in this manner, the boom cylinder 11 is operated by the pressure oil from the normal hydraulic pump 31, and the pilot oil pressure is also increased to increase the boom pressure. In addition to the operation of the cylinder 11, the load on the engine 20 can be reduced to form an energy-saving working machine. The output of the prime mover and the output of the pump when the pressure intensifier is used are as shown in FIG. 7, and in the case of the prior art as shown in FIG. 8, the average output of the prime mover is from ps1 to p
It can be reduced to s2. Note that a thick solid line a indicates the prime mover output, and a thin solid line b indicates the hydraulic pump output. However, in the hydraulic circuit of FIG. 2, a pilot hydraulic pressure may be introduced instead of the pressure switch 37 to open and close the unload valve. In the hydraulic circuit of FIG. It is also possible to use a pressure switch 37 and an unload valve 36. It is also possible to adopt a configuration in which a pressure sensor is used instead of the pressure switch, and the pressure is input to the solenoid drive circuit.

[0033]

As described above, the present invention has the following advantages. That is, as in claim 1,
In the hydraulic supply circuit of the working vehicle, which switches the pressure oil from the hydraulic pump by operating the switching valve and supplies it to the hydraulic actuator, an unload branch oil passage returning to the oil tank is provided at the pump outlet, and the branch position and the switching valve are connected. Since a check valve is provided between the check valve and the switching valve, a pressure accumulator that operates at a predetermined oil pressure or higher is connected between the check valve and the switching valve, so that the oil pressure accumulated in the accumulator is supplied to the hydraulic actuator without being drained by the check valve. In this case, the output of the hydraulic pump can be reduced, and energy can be saved. In addition, by draining from the unload branch oil passage while supplying pressure oil from the pressure accumulator, the amount of hydraulic oil can be reduced, the capacity of the hydraulic oil tank can be reduced, and the size can be reduced.

According to a second aspect of the present invention, in a hydraulic supply circuit of a working vehicle for switching hydraulic oil from a hydraulic pump by operating a switching valve and supplying the hydraulic oil to a hydraulic actuator, an unload branch oil passage returning to an oil tank at a pump outlet. Is established,
A check valve is provided between the branch position and the switching valve, and a pressure booster is connected between the check valve and the switching valve, so that the pressure oil boosted by the pressure boosting device is supplied to the hydraulic actuator. The operation of the hydraulic actuator can be promoted, and a hydraulic motor having a low required output can be adopted, so that the cost can be reduced. By unloading the hydraulic oil from the hydraulic pump while the increased hydraulic pressure is being supplied, the output of the hydraulic pump can be reduced, and energy can be saved. Further, the amount of hydraulic oil can be reduced, the capacity of the hydraulic oil tank can be reduced, and the size can be reduced.

Further, since the unload branch oil passage is provided with an unload valve which is operated by the supply pressure to the actuator, the unload valve is operated when the set pressure is reached, and the light load is drained. During the drain, noise is small, the rise in oil temperature is small, the life of the hydraulic oil can be extended, and the capacity of the oil cooler can be reduced.

According to a fourth aspect of the present invention, the pressure supplied to the actuator is detected by pressure detecting means, and an unload valve is provided in the unload branch oil passage, and the unload valve is operated by the output of the pressure detecting means. Since it opens and closes, when the pressure rises to the set pressure, the unload valve opens,
It can drain with no load, reduce the load on the hydraulic pump, reduce the noise, increase the oil temperature and reduce the oil temperature during draining, and reduce the oil cooler capacity, or Can be omitted.
Further, when the oil pressure drops to the set oil pressure, the oil pressure is closed and the oil pressure from the hydraulic pump can be supplied to the hydraulic actuator, so that the efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is an overall side view of a backhoe.

FIG. 2 is a hydraulic circuit diagram using the pressure accumulator of the present invention.

FIG. 3 is a sectional view showing an embodiment of the pressure accumulator.

FIG. 4 is a hydraulic circuit diagram using the pressure increasing device of the present invention.

FIG. 5 is a sectional view showing an embodiment of the pressure increasing device.

FIG. 6 is a conventional hydraulic circuit diagram.

FIG. 7 is a diagram showing output changes of a hydraulic pump and a prime mover when the pressure booster of the present invention is applied.

FIG. 8 is a diagram showing a conventional output change.

[Explanation of symbols]

 11 hydraulic cylinder 31 hydraulic pump 33 check valve 34 switching valve 35 unload branch oil passage 40 pressure accumulator 50 pressure booster

Claims (4)

[Claims] An unload branch oil passage returning to an oil tank is provided at a pump outlet in a hydraulic supply circuit of a work vehicle which switches hydraulic oil from a hydraulic pump by operating a switching valve and supplies the hydraulic oil to a hydraulic actuator. A hydraulic circuit for a working machine, characterized in that a check valve is provided between the check valve and the switching valve, and a pressure accumulator that operates at a predetermined oil pressure or higher is connected between the check valve and the switching valve. 2. An unload branch oil passage returning to an oil tank at a pump outlet in a hydraulic supply circuit of a working vehicle for switching hydraulic oil from a hydraulic pump by operating a switching valve and supplying the hydraulic oil to a hydraulic actuator. A check valve is provided between the check valve and the switching valve, and a pressure increasing device is connected between the check valve and the switching valve. 3. The hydraulic circuit for a working machine according to claim 1, wherein an unload valve that is activated by a supply pressure to an actuator is provided in the unload branch oil passage. 4. An unload valve is provided in the unload branch oil passage, wherein the unload valve is opened and closed by an output of the pressure detection means. The hydraulic circuit for a working machine according to claim 1 or 2, wherein: