JP6991752B2 - Anti-cavitation hydraulic circuit - Google Patents

Description

The present invention relates to an anti-cavitation hydraulic circuit connected to a hydraulic actuator such as a hydraulic motor, and more particularly to an anti-cavitation hydraulic circuit that reduces cavitation that may occur when the hydraulic actuator is stopped.

Various circuits have been proposed as hydraulic circuits for supplying hydraulic oil to hydraulic motors for traveling and turning. For example, cavitation generated when the hydraulic motor is stopped is accompanied by unpleasant abnormal noise and vibration, and therefore it is preferable to suppress it as much as possible. Patent Document 1 and Patent Document 2 disclose a hydraulic circuit for preventing the occurrence of such cavitation.

Japanese Unexamined Patent Publication No. 2001-214901 Japanese Unexamined Patent Publication No. 2006-17263

The above-mentioned hydraulic circuit disclosed in Patent Document 1 and Patent Document 2 does not necessarily have a simple structure, and a sufficient cavitation suppressing effect cannot always be obtained.

For example, in the hydraulic circuit of Patent Document 1, a return circuit is connected to each of the two main circuits, a check valve is provided in each return circuit, a bypass circuit is connected to the middle point of these return circuits, and the bypass circuit is connected to the bypass circuit. On the other hand, the two branch passages are selectively opened and closed. The hydraulic circuit of Patent Document 1 prevents the occurrence of cavitation by supplying the hydraulic oil of the main circuit on the return side to the main circuit on the supply side when the pump is stopped, but the circuit configuration is complicated and various. It is also necessary to install a check valve in various places. Therefore, the hydraulic circuit of Patent Document 1 tends to be expensive.

Further, in the hydraulic circuit of Patent Document 2, when the hydraulic motor is braked, the suction side supply / discharge passage and the hydraulic motor are connected via a counterbalance valve to suck oil from the suction side supply / discharge passage to the hydraulic motor. Has been improved. However, in this suction side supply / discharge path, the supply of oil is stopped or reduced when the hydraulic motor is braked. Therefore, in the hydraulic circuit of Patent Document 2, a sufficient amount of oil cannot always be supplied to the hydraulic motor, and cavitation may not be sufficiently suppressed in some cases.

As described above, a hydraulic circuit having a simple structure and a high cavitation suppressing effect has not been proposed so far, and there is room for further improvement in terms of cost reduction. Furthermore, with the diversification of needs, some users want a hydraulic circuit that can effectively reduce cavitation even if the cost increases a little, while others want a hydraulic circuit that omits the cavitation reduction function and keeps costs down. .. It is also desired to be able to easily add a cavitation reduction function to an existing circuit as needed so that any of these demands can be met.

The present invention has been made in view of the above circumstances, and one of the objects of the present invention is to provide a hydraulic circuit capable of effectively reducing cavitation by a simple configuration. Another object of the present invention is to provide a hydraulic circuit that can easily add a cavitation reduction function to an existing circuit.

One aspect of the present invention is a first supply / discharge passage and a second supply / discharge passage connected to the hydraulic actuator, in which hydraulic oil is supplied to the hydraulic actuator from one of them and hydraulic oil is discharged from the hydraulic actuator to the other. The first supply / discharge path and the second supply / discharge path are connected to each other via the first connection path, the second supply / discharge path is connected to the second connection path, and the first supply / discharge path is connected. The anti-cavitation valve comprises an anti-cavitation valve having an anti-cavitation spool whose slide position is determined according to the pressure of the hydraulic oil from and the pressure of the hydraulic oil from the second supply / discharge passage, and the anti-cavitation valve has the anti-cavitation spool in the neutral position. The present invention relates to an anti-cavitation hydraulic circuit that takes a connecting path communication state in which the first connecting path and the second connecting path are communicated when the position is at least a part between the stroke end position.

The anti-cavitation hydraulic circuit may include a first block body including a first supply / discharge passage and a second supply / discharge passage, and a second block body attached to the first block body and including an anti-cavitation valve.

The anti-cavitation hydraulic circuit includes a first relay path provided between the first supply / discharge path and the hydraulic actuator, a second relay path provided between the second supply / discharge path and the hydraulic actuator, and a first supply / discharge. A first check valve that operates according to the differential pressure between the pressure of the hydraulic oil in the path and the pressure of the hydraulic oil in the first relay path, and is the hydraulic oil from the first supply / discharge path to the first relay path. The first check valve that allows passage but does not allow the passage of hydraulic oil from the first relay path to the first supply / discharge path, the pressure of the hydraulic oil in the second supply / discharge path, and the operation in the second relay path. It is a second check valve that operates according to the differential pressure from the oil pressure, and allows the passage of hydraulic oil from the second supply / discharge passage to the second relay passage, while allowing the passage of hydraulic oil from the second relay passage to the second relay passage. A second check valve, which does not allow the passage of hydraulic oil toward the road, may be further provided.

The anti-cavitation hydraulic circuit is connected to the first supply / discharge passage and the second supply / discharge passage, and the slide position is set according to the pressure of the hydraulic oil from the first supply / discharge passage and the pressure of the hydraulic oil from the second supply / discharge passage. A counterbalance valve having a fixed counterbalance spool that changes the connection state of the first supply / discharge path to the hydraulic actuator and the connection state of the second supply / discharge path to the hydraulic actuator according to the slide position of the counterbalance spool. Further valves may be provided.

The counterbalance valve further has a first elastic body that imparts an elastic force to the counterbalance spool so that the counterbalance spool is placed in the neutral position, and the anticavitation valve is such that the anticavitation spool is placed in the neutral position. It further has a second elastic body that imparts an elastic force to the anti-cavitation spool, and the elastic modulus of the second elastic body may be smaller than the elastic modulus of the first elastic body.

The anti-cavitation hydraulic circuit has a greater resistance to the hydraulic oil from the anti-cavitation spool to the first supply / drainage channel than to the hydraulic fluid from the first supply / drainage channel to the anti-cavitation spool. The valve and the second slow return check valve, which has a greater resistance to the hydraulic oil from the anti-cavitation spool to the second supply / drainage channel than the resistance to the hydraulic oil from the second supply / drainage channel to the anti-cavitation spool. May be further provided.

According to the present invention, cavitation can be effectively reduced by a simple configuration. Further, by including the anti-cavitation valve in the second block body attached to the first block body, it is possible to easily add a function of reducing cavitation to the circuit included in the first block body.

FIG. 1 is a diagram showing a cross-sectional state of an anti-cavitation hydraulic circuit according to an embodiment of the present invention. FIG. 2 is a diagram showing a cross-sectional state of the anti-cavitation hydraulic circuit according to the embodiment of the present invention. FIG. 3 is a diagram showing a cross-sectional state of the anti-cavitation hydraulic circuit according to the embodiment of the present invention. FIG. 4 is a diagram showing a cross-sectional state of the anti-cavitation hydraulic circuit according to the embodiment of the present invention. FIG. 5 is a circuit diagram showing an example of a hydraulic circuit according to an embodiment of the present invention. FIG. 6 is a circuit diagram showing an example of a hydraulic circuit including an anti-cavitation hydraulic circuit according to a modification of the present invention. FIG. 7 is a conceptual diagram showing the relationship between the difference ΔP between the pressure of the hydraulic oil in the first supply / discharge passage and the pressure of the hydraulic oil in the second supply / discharge passage, and the state of the anti-cavitation valve.

An embodiment of the present invention will be described with reference to the drawings. It should be noted that the elements shown in each drawing may include elements whose size, scale, etc. are shown differently from those actually shown for ease of understanding.

The hydraulic circuit described below is applicable to, for example, a construction machine, and can effectively reduce cavitation that may occur when the traveling hydraulic motor and the turning hydraulic motor are stopped. However, the device to which the following hydraulic circuit can be applied is not particularly limited, and the following hydraulic circuit can be suitably used when reduction of cavitation is desired in any device using a hydraulic actuator such as a hydraulic motor. be.

1 to 4 are views showing a cross-sectional state of the anti-cavitation hydraulic circuit 10 according to the embodiment of the present invention, and simply show the connection state of the anti-cavitation hydraulic circuit 10 and the hydraulic motor 15.

[Constitution]
The anti-cavitation hydraulic circuit 10 includes a first supply / discharge passage 21, a second supply / discharge passage 22, a counterbalance valve 40, and an anti-cavitation valve 50. The first supply / discharge passage 21, the second supply / discharge passage 22, and the counterbalance valve 40 are included in the first block body 11, while the anti-cavitation valve 50 is included in the second block body 12. The second block body 12 is fixedly attached to the first block body 11 via an arbitrary fixing tool (not shown) such as a screw.

The first supply / discharge passage 21 and the second supply / discharge passage 22 are connected to the hydraulic motor 15, and hydraulic oil is supplied to the hydraulic motor 15 from one of them, and hydraulic oil is discharged from the hydraulic motor 15 to the other, and the hydraulic motor 15 is discharged. Forward rotation drive or reverse rotation drive is performed. In FIGS. 1 to 4, the first supply / discharge passage 21 is connected to the hydraulic pump P, the second supply / discharge passage 22 is connected to the discharge tank T, and the hydraulic oil is supplied from the first supply / discharge passage 21 to the hydraulic motor 15. The state of the anti-cavitation hydraulic circuit 10 when the hydraulic oil is supplied and the hydraulic oil is discharged from the hydraulic motor 15 to the second supply / discharge passage 22 to drive the hydraulic motor 15 in the forward direction is shown.

The main circuit (oil passage) connected to each of the first connection port 23 and the second connection port 24 is connected to a control switching valve (not shown), and the control switching valve is used for the hydraulic pump P and the discharge tank T. The connection mode of the 1 supply / discharge path 21 and the second supply / discharge path 22 can be changed. That is, by the control switching valve that can be operated by the user, the oil passage configuration on the upstream side of the anti-cavitation hydraulic circuit 10 is connected, and the discharge tank T is connected to the second supply / discharge passage 22 while the hydraulic pump P is connected to the first supply / discharge passage 21. It is possible to switch to the forward rotation drive mode to be connected or the reverse rotation drive mode in which the discharge tank T is connected to the first supply / discharge passage 21 while the hydraulic pump P is connected to the second supply / discharge passage 22.

The counterbalance valve 40 is connected to the first supply / discharge passage 21 and the second supply / discharge passage 22, and the pressure of the hydraulic oil from the first supply / discharge passage 21 and the pressure of the hydraulic oil from the second supply / discharge passage 22. It has a first spool (counterbalance spool) 41 in which the slide position with respect to the axial Da is determined according to the above. A plurality of notches 42 and a plurality of land portions 43 are formed in the first spool 41, and a state in which the first supply / discharge path 21 is connected to the hydraulic motor 15 according to the slide position of the first spool 41. And the connection state of the second supply / discharge path 22 changes. Both ends of the first spool 41 receive an elastic force in the axial direction Da from the first springs 47a and 47b housed in the first spring chambers 46a and 46b. The first spring chambers 46a and 46b each have a first supply / discharge passage 21 and a through passage 45 formed inside the first spool 41 and a fixed throttle portion 44 formed in the notch 42 of the first spool 41, respectively. It communicates with the second supply / discharge passage 22. The first springs 47a and 47b apply an elastic force to the first spool 41 so as to arrange the first spool 41 in a neutral position, whereas the hydraulic oil flowing into the first spring chambers 46a and 46b is the first spool. Hydraulic pressure is applied to the first spool 41 so as to move the 41 toward the stroke end position. Therefore, the slide position of the first spool 41 is the pressure of the hydraulic oil flowing into the first spring chamber 46a from the first supply / discharge passage 21, the elastic force of the first spring 47a, and the first spring chamber from the second supply / discharge passage 22. It is determined according to the pressure of the hydraulic oil flowing into the 46b and the elastic force of the first spring 47b.

The anti-cavitation valve 50 is connected to the first supply / discharge passage 21 via the counterbalance valve 40 and the first connecting passage 61, and is connected to the second supply / discharge passage 22 via the counterbalance valve 40 and the second connecting passage 62. It has a second spool (anti-cavitation spool) 51 which is connected to and whose slide position is determined according to the pressure of the hydraulic oil from the first supply / discharge passage 21 and the second supply / discharge passage 22. Each of the first connecting path 61 and the second connecting path 62 is composed of holes formed in the first block body 11 and the second block body 12, and has a spool hole in which the first spool 41 is slidably arranged. , The second spool 51 is connected to the spool hole in which the second spool 51 is slidably arranged. Further, the first communication path 61 and the second communication path 62 communicate with the corresponding fixed narrowing section 54, respectively.

A plurality of notches 52 and a plurality of land portions 53 are formed on the second spool 51. The anti-cavitation valve 50 has a communication path cutoff state in which the communication between the first communication path 61 and the second communication path 62 is blocked by the land portion 53 and the first communication path 61 according to the slide position of the second spool 51. And the second connecting path 62 are communicated with each other through the notch 52, which is one of the connecting paths communicating states. Both ends of the second spool 51 receive an elastic force in the axial direction Da from the second springs 57a and 57b housed in the second spring chambers 56a and 56b. The second spring chambers 56a and 56b communicate with the first communication path 61 and the second communication path 62, respectively, via the fixed drawing portion 54 formed in the second block body 12. The second springs 57a and 57b apply an elastic force to the second spool 51 so as to arrange the second spool 51 in a neutral position, whereas the hydraulic oil flowing into the second spring chambers 56a and 56b is the second spool. Hydraulic pressure is applied to the second spool 51 so as to move the 51 toward the stroke end position. Therefore, the slide position of the second spool 51 is the pressure of the hydraulic oil flowing into the second spring chamber 56a from the first supply / discharge passage 21 through the counterbalance valve 40, the first connecting passage 61 and the fixed throttle portion 54, and the second. The elastic force of the spring 57a, the pressure of the hydraulic oil flowing from the second supply / discharge passage 22 into the second spring chamber 56b via the counterbalance valve 40, the second connecting path 62 and the fixed throttle portion 54, and the pressure of the second spring 57b. It depends on the elastic force.

The plurality of notches 42 of the first spool 41 (particularly, the plurality of notches 42 in which the fixed throttle portion 44 is formed) are the first supply / discharge passage 21 and the first regardless of the slide position of the first spool 41. It is arranged between the connecting path 61 and between the second supply / draining path 22 and the second connecting path 62. Therefore, regardless of the slide position of the first spool 41, the hydraulic oil in the first supply / discharge passage 21 and the hydraulic oil in the second supply / discharge passage 22 are the fixed throttle portion 44, the through-passage 45, and the first spring chamber 46a. It flows into the 46b and acts on the first spool 41, and also flows into the notch 42, the first connecting path 61, the second connecting path 62, the fixed throttle portion 54 and the second spring chambers 56a and 56b, and flows into the second spool 51. Acts on.

The anti-cavitation hydraulic circuit 10 further includes a first relay path 31, a second relay path 32, a first check valve 65, and a second check valve 66. The first relay path 31 is provided between the first supply / discharge path 21 and the hydraulic motor 15, and the second relay path 32 is provided between the second supply / discharge path 22 and the hydraulic motor 15. The first relay path 31 is provided with a first communication port 35 that communicates with the hydraulic motor 15 via the first communication oil passage 37, and the second relay path 32 is hydraulically supplied via the second communication oil passage 38. A second communication port 36 that communicates with the motor 15 is provided. The first check valve 65 passes through the first check through passage 26 between the first supply / discharge passage 21 and the first relay passage 31 with the pressure of the hydraulic oil in the first supply / discharge passage 21 and the inside of the first relay passage 31. It opens and closes according to the pressure difference between the hydraulic oil and the hydraulic oil, allowing the hydraulic oil to pass from the first relay path 21 to the first relay path 31, while allowing the passage of the hydraulic oil from the first relay path 31 to the first relay path 31. Do not allow the passage of hydraulic oil toward 21. The second check valve 66 makes the second check through path 27 between the second supply / discharge path 22 and the second relay path 32 the pressure of the hydraulic oil in the second supply / discharge path 22 and the inside of the second relay path 32. It opens and closes according to the pressure difference from the pressure of the hydraulic oil, and allows the hydraulic oil to pass from the second relay path 22 to the second relay path 32, while allowing the passage of the hydraulic oil from the second relay path 32 to the second relay path 22. Do not allow the passage of hydraulic oil toward.

The anti-cavitation valve 50 having the above configuration cuts off communication between the first supply / discharge passage 21 and the second supply / discharge passage 22 when the second spool 51 is located at least in the neutral position and the stroke end position. The communication path is cut off, and when it is located at least a part between the neutral position and the stroke end position, the communication path communication state is established in which the first supply / discharge path 21 and the second supply / discharge path 22 are communicated with each other. Therefore, the first supply / discharge passage 21 and the second supply / discharge passage 22 communicate with each other while the second spool 51 moves from the neutral position to the stroke end position and while the second spool 51 moves from the stroke end position to the neutral position. There is a communication path communication state.

The neutral position here means, for example, a state in which no force is applied to the spool from the hydraulic oil, or a force applied to the spool from the hydraulic oil in the first supply / discharge passage 21 and the inside of the second supply / discharge passage 22. It is a position where the spool is arranged in a state where the force applied from the hydraulic oil of the above is equal, and is a position determined by the elastic force of the springs arranged at both ends. The stroke end position is the most end position (left and right end positions in FIG. 1) in the axial direction Da among the positions where the spool can slide.

At the initial stage of the stop operation of the hydraulic motor 15, the hydraulic motor 15 continues to rotate due to inertia and exerts a vacuum action to suck hydraulic oil from the first supply / discharge passage 21 while trying to suck hydraulic oil from the hydraulic pump P. 1 The supply of hydraulic oil to the supply / discharge passage 21 is stopped or reduced. Therefore, an imbalance occurs between the amount of hydraulic oil that the hydraulic motor 15 tries to suck in and the amount of hydraulic oil that can be supplied to the hydraulic motor 15 from the first supply / discharge passage 21. Due to this imbalance, cavitation may occur when the hydraulic motor 15 is stopped. In the anti-cavitation hydraulic circuit 10 of the present embodiment described above, the anti-cavitation valve 50 is described above in at least a part of the time when the second spool 51 moves from the stroke end position to the neutral position in the initial stage of the stop operation of the hydraulic motor 15. Take a communication path communication state. As a result, the hydraulic oil once discharged from the hydraulic motor 15 is guided to the first supply / discharge passage 21 and can be supplied to the hydraulic motor 15 again, so that the above-mentioned imbalance is suppressed and cavitation is effectively reduced. Can be done.

[Operation]
Hereinafter, the specific operation of the counterbalance valve 40 and the anti-cavitation valve 50 will be described.

When the supply of hydraulic oil to the first supply / discharge passage 21 and the second supply / discharge passage 22 is stopped, the first spool 41 and the second spool 51 are arranged in the neutral position as shown in FIG. In this case, the oil passage between the first supply / discharge passage 21 and the second supply / discharge passage 22 (that is, the spool hole of the counterbalance valve 40 and the spool hole of the anti-cavitation valve 50) is the land portion 43 of the first spool 41 and the land portion 43. It is blocked by the land portion 53 of the second spool 51. Further, each of the oil passage between the first supply / discharge passage 21 and the first relay passage 31 and the oil passage between the second supply / discharge passage 22 and the second relay passage 32 (that is, the spool hole of the counterbalance valve 40). Is also blocked by the land portion 43 of the first spool 41. Further, the first check valve 65 shuts off the first check through-passage 26, and the second check valve 66 shuts off the second check through-passage 27. Therefore, the hydraulic oil is not supplied or discharged from the hydraulic motor 15, and the hydraulic motor 15 is placed in a stopped state.

On the other hand, when the first supply / discharge passage 21 is communicated with the hydraulic pump P and the second supply / discharge passage 22 is communicated with the discharge tank T by a control switching valve (not shown), the hydraulic oil from the hydraulic pump P is communicated with the first supply / discharge passage. It is supplied to 21, and the pressure of the hydraulic oil in the first supply / discharge passage 21 increases. As a result, as shown in FIGS. 2 and 3, the first check valve 65 opens the first check through-passage 26, and the first supply / discharge passage 21 to the first relay path 31, the first communication port 35, and the first communication oil flow. Hydraulic oil is supplied to the hydraulic motor 15 via the passage 37. Further, the pressure of the hydraulic oil flowing into the first spring chamber 46a from the first supply / discharge passage 21 through the fixed throttle portion 44 and the through passage 45 increases, and the notch portion 42 and the first contact from the first supply / discharge passage 21. The pressure of the hydraulic oil flowing into the second spring chamber 56a through the path 61 and the fixed throttle portion 54 increases. As a result, the first spool 41 and the second spool 51 move toward one stroke end position (stroke end position on the right side in FIG. 2). At this time, as shown in FIGS. 2 and 3, the second relay path 32 communicates with the second supply / discharge passage 22 via the notch 42 of the first spool 41, and the hydraulic motor 15 to the second communication oil passage 38, Hydraulic oil is discharged to the second supply / discharge passage 22 through the second communication port 36, the second relay path 32, and the notch 42. In this way, the hydraulic motor 15 is driven in the forward rotation.

In the state shown in FIGS. 2 and 3, the second spool 51 is arranged at the stroke end position on the right side, and the oil passage between the first connecting passage 61 and the second connecting passage 62 (that is, the anti-cavitation valve 50). The spool hole) is blocked by the land portion 53 of the second spool 51. In this state, the hydraulic oil does not directly flow out from the first supply / discharge path 21 to the second supply / discharge path 22 via the first connecting path 61 and the second connecting path 62 without passing through the hydraulic motor 15. , The hydraulic motor 15 can be driven with energy efficiency.

However, while the second spool 51 is moving from the neutral position to the stroke end position, the first connecting path 61 and the second connecting path 62 communicate with each other through the notch 52 of the second spool 51, and the hydraulic motor 15 There is a state in which the hydraulic oil directly flows out from the first supply / discharge passage 21 to the second supply / discharge passage 22 without passing through. In order to shorten the time for maintaining that state as much as possible, the spring constants (elastic modulus) of the second springs 57a and 57b of the anticavitation valve 50 are set sufficiently small so that the second springs 57a and 57b to the second spool It is preferable to keep the elastic force applied to the 51 low. In this case, the second spool 51 can be reached from the neutral position to the stroke end position in a very short time according to the increase in the pressure of the hydraulic oil in the first supply / discharge passage 21, and the first hydraulic oil can be reached. It is also possible to reduce the energy loss due to the direct outflow from the supply / discharge passage 21 to the second supply / discharge passage 22 to a substantially negligible level. In addition, when the spring constants of the second springs 57a and 57b are very small, the force of the second springs 57a and 57b to return the second spool 51 to the neutral position becomes weak. The low restoring force (low elastic force) of the second springs 57a and 57b and the throttle effect of the fixed throttle portion 54 combine to slowly return the second spool 51 from the stroke end position to the neutral position. It is possible to obtain the effect of reducing cavitation for a long period of time.

In the present embodiment, the elastic modulus (for example, spring constant) of the second springs 57a and 57b (second elastic body) of the anti-cavitation valve 50 is the elastic modulus (for example, spring constant) of the first springs 47a and 47b (first elastic body) of the counterbalance valve 40. It is set smaller than the elastic modulus. In this case, as shown in FIG. 2, the second spool 51 reaches the stroke end position in advance before the first spool 41 reaches the stroke end position, and after a certain time has elapsed from that point, as shown in FIG. The first spool 41 also reaches the stroke end position.

On the other hand, when the hydraulic motor 15 is stopped by a control switching valve (not shown), the first spool 41 and the second spool 51 gradually move from the stroke end position toward the neutral position (toward the left side in FIG. 4). It moves and is finally placed in the neutral position shown in FIG. 1, and the supply and discharge of hydraulic oil in the hydraulic motor 15 is stopped. That is, when the hydraulic motor 15 is stopped, the supply of hydraulic oil from the hydraulic pump P to the first supply / discharge passage 21 is stopped, but the pressure of the hydraulic oil in the first supply / discharge passage 21 gradually increases over time. descend. Therefore, the first spool 41 and the second spool 51 have strokes according to the decrease in the pressure of the hydraulic oil in the first supply / discharge passage 21 and the elastic force from the first springs 47a, 47b and the second springs 57a, 57b. Gradually move from the end position to the neutral position. In this way, while the second spool 51 returns from the stroke end position to the neutral position, the first connecting path 61 and the second connecting path 62 are communicated with each other through the notch 52 of the second spool 51, and the first connecting path 61 and the second connecting path 62 are communicated with each other. 2 The hydraulic oil is sent from the connecting path 62 to the first connecting path 61, and cavitation is reduced.

That is, for a while after the stop operation of the hydraulic motor 15, the hydraulic motor 15 continues to rotate while being decelerated by inertia, and tries to continue sucking oil from the first supply / discharge passage 21. On the other hand, the hydraulic oil discharged from the hydraulic motor 15 is connected from the second relay path 32 to the second supply / discharge path 22 and the second through the notch 42 of the first spool 41 in which the communication passage area is gradually reduced. It flows into the road 62. The hydraulic oil that has flowed into the second connecting path 62 flows into the first connecting path 61 through the notch 52 of the second spool 51 of the anti-cavitation valve 50, and then flows through the notch 42 of the counterbalance valve 40. It flows into the first supply / discharge channel 21. As a result, the imbalance between the amount of hydraulic oil that the hydraulic motor 15 tries to suck in from the first supply / discharge passage 21 and the amount of hydraulic oil that can be supplied to the hydraulic motor 15 from the first supply / discharge passage 21 is suppressed, and cavitation is suppressed. Can be reduced.

Although the above description mainly relates to the forward rotation drive mode, those skilled in the art can understand that the same effect can be obtained in the case of the reverse rotation drive mode. That is, when the hydraulic oil from the hydraulic pump P is supplied to the second supply / discharge passage 22 and the hydraulic oil from the first supply / discharge passage 21 is discharged to the discharge tank T, the flow of the hydraulic oil and the hydraulic motor 15 The rotation direction, the operating direction of the counterbalance valve 40 and the anti-cavitation valve 50, and the behavior of the first check through path 26 and the second check through path 27 are opposite to the above-mentioned forward rotation drive mode, but basically. Shows the same behavior as the forward rotation drive mode.

[circuit diagram]
FIG. 5 is a circuit diagram showing an example of the hydraulic circuit 90 according to the embodiment of the present invention. Note that FIG. 5 mainly shows a state reflecting the working surface of the anti-cavitation hydraulic circuit 10 shown in FIGS. 1 to 4, the anti-cavitation hydraulic circuit 10 shown in FIG. 5 and the anti-cavitation hydraulic circuit 10 shown in FIGS. 1 to 4. Does not necessarily match structurally with.

FIG. 5 shows a state in which the first spool 41 of the counterbalance valve 40 and the second spool 51 of the anti-cavitation valve 50 are arranged in a neutral position (see FIG. 1), and the counterbalance valve 40 has a sign “40b”. The block indicated is selected, and the block indicated by the sign "50c" is selected in the anti-cavitation valve 50.

On the other hand, when the first spool 41 is arranged in a slide position other than the neutral position, the block represented by the sign "40a" is selected in the forward rotation drive mode, and the block represented by the sign "40c" is selected in the reverse rotation drive mode. Will be done. Further, in the anti-cavitation valve 50, when the second spool 51 is arranged at the stroke end position in the forward rotation drive mode, the block indicated by the sign “50a” is selected, and the second spool 51 is set in the forward rotation drive mode. When the block is arranged between the stroke end position and the neutral position (particularly during the above-mentioned communication path communication state), the block indicated by the sign “50b” is selected, and the second spool 51 is the stroke end in the reverse drive mode. When arranged at the position, the block indicated by the sign "50e" is selected, and when the second spool 51 is arranged between the stroke end position and the neutral position in the reverse drive mode (particularly the above-mentioned communication). The block indicated by the sign "50d" is selected during the road communication state).

The hydraulic circuit 90 shown in FIG. 5 further includes a high-pressure selection valve 91, a brake device 92, a switching valve 93, and a switching cylinder 94 in addition to the above-mentioned anti-cavitation hydraulic circuit 10. The high-pressure selection valve 91 selects a high-pressure side oil passage among the first supply / discharge passage 21 and the second supply / discharge passage 22 and allows hydraulic oil to flow toward the switching valve 93. The switching valve 93 switches the oil passage according to the pilot pressure oil from the pilot pressure source P, and switches whether or not the hydraulic oil is supplied from the high pressure selection valve 91 to the switching cylinder 94. The switching cylinder 94 switches the hydraulic motor 15 to a high speed mode or a low speed mode depending on the presence or absence of supply of hydraulic oil from the switching valve 93. Further, the brake device 92 when the hydraulic motor 15 is stopped is connected to the hydraulic motor 15. Further, the hydraulic motor 15 is connected to the drains D1 and D2.

As described above, according to the present embodiment, cavitation can be effectively reduced by the anti-cavitation valve 50 having a simple configuration. Further, the first supply / discharge passage 21, the second supply / discharge passage 22, and the counterbalance valve 40 are formed in the first block body 11, while the anti-cavitation valve 50 is formed in the second block body 12. Therefore, relatively simple processing such as forming the first connecting path 61 and the second connecting path 62 is added to the first block body 11, and the second block body 12 is simply attached to the first block body 11. A cavitation reduction function can be added to the hydraulic circuit included in the first block body 11. Therefore, the user can easily select whether or not to add the cavitation reduction function to the hydraulic circuit included in the first block body 11 in the hydraulic circuit manufacturing process.

[First modification]
FIG. 6 is a circuit diagram showing an example of a hydraulic circuit 90 including an anti-cavitation hydraulic circuit 10 according to a modification of the present invention. The hydraulic circuit 90 of this modification has basically the same circuit configuration as the hydraulic circuit 90 shown in FIG. 5 described above, but instead of the fixed throttle portion 54, the first slow return check valve 71 and the second slow return check valve 72 is provided. The first slow return check valve 71 has a resistance to the hydraulic oil from the second spool 51 to the first supply / discharge passage 21 rather than a resistance to the hydraulic oil from the first supply / discharge passage 21 to the second spool 51. Is big. On the other hand, the second slow return check valve 72 brings more resistance to the hydraulic oil from the second spool 51 to the second spool 51 than to the resistance to the hydraulic oil from the second spool 51 to the second spool 51. Is larger.

According to this modification, when the second spool 51 is moved from the neutral position to the stroke end position, the resistance brought to the hydraulic oil by the first slow return check valve 71 and the second slow return check valve 72 is relatively large. Due to its small size, the second spool 51 moves quickly. On the other hand, when the second spool 51 is moved from the stroke end position to the neutral position, the resistance brought to the hydraulic oil by the first slow return check valve 71 and the second slow return check valve 72 is relatively large, so that the second spool 51 is second. The spool 51 moves slowly. According to the anti-cavitation hydraulic circuit 10 having this configuration, cavitation is reduced while reducing energy loss due to direct communication between the first supply / discharge path 21 and the second supply / discharge path 22 in the communication path communication state. The effect of can be ensured for a long time.

The specific configuration of the first slow return check valve 71 and the second slow return check valve 72 is not particularly limited, and known slow return check valves can also be used. Further, the installation positions of the first slow return check valve 71 and the second slow return check valve 72 are not particularly limited, and among the oil passages from the first supply / discharge passage 21 to the second spool 51 (for example, the second spring chamber 56a). It is possible to place the first slow return check valve 71 at a suitable location in the oil passage from the second supply / discharge passage 22 to the second spool 51 (for example, the second spring chamber 56b). It is possible to arrange the second slow return check valve 72 at the location.

[Other variants]
For example, the positions, widths and shapes of the notch 42 and the land portion 43 of the first spool 41 and the positions, widths and shapes of the notches 52 and the land 53 of the second spool 51 can be appropriately changed. .. In particular, by changing the positions, widths, shapes, etc. of the notch 52 and the land 53 of the second spool 51, the state of communication between the first connecting path 61 and the second connecting path 62 (that is, the first supply / discharge path). It is also possible to adjust the state of communication between 21 and the second supply / discharge path 22). It is also possible to adjust the elastic characteristics of the first springs 47a and 47b of the counterbalance valve 40 and the elastic characteristics of the second springs 57a and 57b of the anti-cavitation valve 50.

FIG. 7 shows the difference ΔP (= P1-P2) between the hydraulic oil pressure P1 in the first supply / discharge passage 21 and the hydraulic oil pressure P2 in the second supply / discharge passage 22, and the state of the anti-cavitation valve 50. It is a conceptual diagram showing the relationship between. The horizontal axis of FIG. 7 indicates ΔP, and the right side of the position indicated by “0” (that is, the neutral position) indicates that ΔP is a positive value (+), and the left side of the position indicated by “0”. Indicates that ΔP is a negative value (-). As shown in FIG. 7, when ΔP is positive and larger than the first differential pressure value d1, the anti-cavitation valve 50 takes a communication path cutoff state. When ΔP is positive and is equal to or less than the first differential pressure value d1 and larger than the second differential pressure value d2, the anti-cavitation valve 50 takes a communication path communication state. When ΔP is negative and smaller than the fourth differential pressure value d4, the anti-cavitation valve 50 takes a connecting path cutoff state. When ΔP is negative and is equal to or greater than the fourth differential pressure value d4 and smaller than the third differential pressure value d3, the anti-cavitation valve 50 takes a communication path communication state. When ΔP is the second differential pressure value d2 or less and the third differential pressure value d3 or more, the anti-cavitation valve 50 takes a communication path cutoff state.

Specific values of the first to fourth differential pressure values d1 to d4 shown in FIG. 7 can be appropriately set by adjusting the shape of the second spool 51 and the spring constants of the second springs 57a and 57b. .. For example, the absolute value of the second differential pressure value d2 can be set to be the same as or different from the absolute value of the third differential pressure value d3, and in particular, the difference between the second differential pressure value d2 and the third differential pressure value d2. It is also possible to set the pressure value d3 to "0" or a value in the vicinity thereof. It is also possible to set the absolute value of the first differential pressure value d1 to be the same as or different from the absolute value of the fourth differential pressure value d4.

A form including a component other than the above-mentioned components may also be included in the embodiment of the present invention. Further, an embodiment of the present invention may also include a form in which some of the above-mentioned components are not included. In addition, an embodiment of the present invention may also include some components included in one embodiment of the present invention and some components included in other embodiments of the present invention. Therefore, the components included in each of the above-described embodiments and modifications and the embodiments of the present invention other than the above may be combined, and the embodiments related to such combinations are also included in the embodiments of the present invention. sell. Further, the effect produced by the present invention is not limited to the above-mentioned effect, and a peculiar effect according to the specific configuration of each embodiment can be exhibited. In this way, various additions, changes and partial deletions can be made to each element described in the claims, the specification, the abstract and the drawings without departing from the technical idea and purpose of the present invention. Is.

10 ... Anti-cavitation hydraulic circuit, 11 ... 1st block body, 12 ... 2nd block body, 15 ... Hydraulic motor, 21 ... 1st supply / discharge path, 22 ... 2nd supply / discharge path, 23 ... 1st connection port, 24 ... 2nd connection port, 26 ... 1st check through path, 27 ... 2nd check through path, 31 ... 1st relay path, 32 ... 2nd relay path, 35 ... 1st communication port, 36 ... 2nd communication port, 37 ... 1st oil pressure passage, 38 ... 2nd oil pressure passage, 40 ... counter balance valve, 41 ... 1st spool, 42 ... notch, 43 ... land part, 44 ... fixed throttle part, 45 ... through passage, 46a ... 1st spring chamber, 46b ... 1st spring chamber, 47a ... 1st spring, 47b ... 1st spring, 50 ... anti-cavitation valve, 51 ... 2nd spool, 52 ... notch, 53 ... land, 54 ... fixed Squeezing part, 56a ... 2nd spring chamber, 56b ... 2nd spring chamber, 57a ... 2nd spring, 57b ... 2nd spring, 61 ... 1st connecting path, 62 ... 2nd connecting path, 65 ... 1st check valve, 66 ... 2nd check valve, 71 ... 1st slow return check valve, 72 ... 2nd slow return check valve, 90 ... hydraulic circuit, 91 ... high pressure selection valve, 92 ... braking device, 93 ... switching valve, 94 ... switching cylinder , P ... Hydraulic pump, T ... Discharge tank

Claims (6)

A first supply / discharge path and a second supply / discharge path connected to the hydraulic actuator, the first supply / discharge path in which hydraulic oil is supplied to the hydraulic actuator from one of them and hydraulic oil is discharged from the hydraulic actuator to the other. And the second supply / discharge route,
The first supply / discharge path is connected via the first connecting path, the second supply / discharging path is connected via the second connecting path, the pressure of the hydraulic oil from the first connecting path and the second contact. Equipped with an anti-cavitation valve, which has an anti-cavitation spool whose slide position is determined according to the pressure of hydraulic oil from the road.
The anti-cavitation valve is
When the anti-cavitation spool is located at least in the neutral position and the stroke end position, a communication path blocking state is taken in which communication between the first connecting path and the second connecting path is cut off.
When the anti-cavitation spool is located at least in a part between the neutral position and the stroke end position, the anti-cavitation takes a communication path communication state in which the first communication path and the second communication path are communicated with each other. Hydraulic circuit. The first block body including the first supply / discharge passage and the second supply / discharge passage, and
The anti-cavitation hydraulic circuit according to claim 1, further comprising a second block body attached to the first block body and including the anti-cavitation valve. A first relay path provided between the first supply / discharge path and the hydraulic actuator,
A second relay path provided between the second supply / discharge path and the hydraulic actuator,
It is a first check valve that operates according to the differential pressure between the pressure of the hydraulic oil in the first supply / discharge passage and the pressure of the hydraulic oil in the first relay passage, and is the first check valve from the first supply / discharge passage. A first check valve that allows the passage of hydraulic oil toward the relay path but does not allow the passage of the hydraulic oil from the first relay path to the first supply / discharge path.
A second check valve that operates according to the differential pressure between the pressure of the hydraulic oil in the second supply / discharge passage and the pressure of the hydraulic oil in the second relay passage, and is the second check valve from the second supply / discharge passage. 2. Claim 1 or 2 further includes a second check valve that allows the passage of hydraulic oil toward the relay path but does not allow the passage of hydraulic oil from the second relay path to the second supply / discharge path. The described anti-cavitation hydraulic circuit. A counter connected to the first supply / discharge passage and the second supply / discharge passage, and the slide position is determined according to the pressure of the hydraulic oil from the first supply / discharge passage and the pressure of the hydraulic oil from the second supply / discharge passage. A counterbalance valve having a balance spool, in which the connection state of the first supply / discharge path to the hydraulic actuator and the connection state of the second supply / discharge path to the hydraulic actuator are determined according to the slide position of the counterbalance spool. The anti-cavitation hydraulic circuit according to any one of claims 1 to 3, further comprising a variable counterbalance valve. The counterbalance valve further has a first elastic body that applies an elastic force to the counterbalance spool so as to arrange the counterbalance spool in a neutral position.
The anti-cavitation valve further has a second elastic body that imparts an elastic force to the anti-cavitation spool so as to arrange the anti-cavitation spool in a neutral position.
The anti-cavitation hydraulic circuit according to claim 4, wherein the elastic modulus of the second elastic body is smaller than the elastic modulus of the first elastic body. With the first slow return check valve, the resistance to the hydraulic oil from the anti-cavitation spool to the first supply / discharge channel is greater than the resistance to the hydraulic oil from the first supply / discharge channel to the anti-cavitation spool. ,
With the second slow return check valve, the resistance to the hydraulic oil from the anti-cavitation spool to the second supply / discharge channel is greater than the resistance to the hydraulic oil from the second supply / discharge channel to the anti-cavitation spool. The anti-cavitation hydraulic circuit according to any one of claims 1 to 5, further comprising.

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