JPH0366523B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a brake circuit, and more particularly to a brake circuit designed to alleviate the swinging back or swinging phenomenon of an actuator, such as a hydraulic motor, that occurs when the supply of pressure oil is stopped.

Prior Art For example, in a hydraulic excavator, a hydraulic circuit as shown in Fig. 1 is used to drive the revolving body of the excavator, but when the supply of pressure oil is stopped in this hydraulic circuit, the actuator of the revolving body of the excavator is There is a problem in that the hydraulic motor rotates in reverse or repeats reverse and forward rotations, that is, the above-mentioned rocking back phenomenon or rocking phenomenon occurs. This problem is due to the following reasons.

In other words, if the inertia of the load is large, such as the revolving body of a shovel, even if the supply of pressure oil to the hydraulic motor is stopped, the inertia of the load will cause the hydraulic motor to overrun, resulting in pressure oil being discharged. The pressure in the line increases, compressing the oil and storing energy in the line.As a result, this compressed energy causes the hydraulic motor to reverse and swing back.
Furthermore, due to this reversal, the pressure on the pressure oil supply line side becomes high again, which then causes normal rotation, causing a so-called rocking phenomenon in which this reversal and forward rotation are repeated. When this swinging back phenomenon or swinging phenomenon occurs, it not only becomes difficult to perform an accurate positioning operation, but also causes anxiety to the driver and further shortens the life of the machine.

To explain this point regarding the brake circuit (Fig. 1) with the above configuration, if you try to stop the operation of the hydraulic motor 1 by switching the direction control valve 10 to the neutral position and setting the counterbalance valve 9 to the neutral position, the load The hydraulic motor 1 is further rotated by the inertia force of 2, and as a result, if line 3 is now used as a pressure oil supply line and line 4 is used as a pressure oil discharge line, the pressure in the discharge line 4 becomes equal to that of the supply line 3. It becomes higher than the pressure and acts to reverse the hydraulic motor 1, but at this time, one of the relief valves 8 opens and high pressure oil from the line 4 side flows into the line 3 side, suppressing the reverse rotation of the hydraulic motor 1. . Then, the high pressure oil in the discharge line 4 flows into the supply line 3 via the bypass line 6, and the hydraulic motor 1 is decelerated. A problem occurs in which the movement starts in reverse immediately after stopping. When reversed, the pressure relationship is also reversed, with high pressure on the supply line 3 side and low pressure on the discharge line 4 side. Due to this reversal, compression energy is stored in the supply line 3 side, so that the hydraulic motor 1 repeats forward and reverse rotations until finally, when the pressure in the supply and discharge lines 3 and 4 balances with the static load of the hydraulic motor 1. Hydraulic motor 1 stops.

Although the brake circuit configured as described above has a certain effect on stopping the inertial load, the effect cannot be said to be sufficient. In other words, when the supply of pressure oil to the hydraulic motor 1 is stopped, it has no function in suppressing the reverse rotation of the hydraulic motor 1 that occurs immediately after that, and therefore, the repeated forward and reverse rotation of the hydraulic motor 1 is prevented. Problems still arise.

Technical Problems of the Present Invention Therefore, the technical problems to be solved by the present invention are as follows:
A special pilot circuit consisting of a normally closed main pressure valve, a relief valve, and a shuttle valve is used to quickly and sufficiently absorb the pressurized oil in the discharge line, which has increased in pressure when the pressure oil supply to the actuator is stopped, before the reversal continues. By adding , the pressure on the supply line side immediately after entering the reversal is utilized,
The purpose is to allow the compressed fluid on the discharge line side to quickly escape to the supply line side.

Structure and operation of the present invention In order to achieve the above-mentioned technical problem, the present invention was structured as follows.

That is, between the first and second pressure oil supply and discharge lines connected to an actuator such as a hydraulic motor, the first,
a second bypass line is provided, and a first main pressure valve is provided in the first bypass line, the inlet port being connected to the first pressure oil supply/discharge line side and the outlet port being connected to the second pressure oil supply/discharge line side, respectively; A second main pressure valve having an inlet port connected to the second pressure oil supply/discharge line side and an outlet port connected to the first pressure oil supply/discharge line side is provided in the second bypass line, and the first and second main pressure valves are connected to each other. The pilot port is connected to each inlet port of the shuttle valve by first and second connection lines, and the first connection line is connected to the outlet port of the first main pressure valve, and the second connection line is connected to the second main pressure valve. are connected to the outlet port sides of the shuttle valve through first and second relief valves, respectively, and the outlet port of the shuttle valve is opened to the tank via a third relief valve, and each inlet at both ends of the reverse action shuttle valve is connected to the outlet port side of the shuttle valve. The ports are connected to each pressure oil supply/discharge line, while the outlet port of the reverse action shuttle valve is connected to the pilot port of the third relief valve. Each of the main pressure valves includes a spool for opening and closing the first and second bypass lines, and a throttle passage communicating the inlet port and the pilot port.

According to the upper air configuration, if the first pressure oil supply and discharge line is now the pressure oil supply line and the second pressure oil supply and discharge line is the pressure oil discharge line, and the supply of pressure oil is stopped, the second pressure oil supply and discharge line The pressure of the valve is about to rise rapidly, and the poppet of the shuttle valve moves in the direction of absorbing the pressure, and this movement causes the pressure oil in the second pressure oil supply and discharge line to flow through the throttle passage of the second main pressure valve. The pressure oil flows into the shuttle valve side and is quickly absorbed, and at the same time, the second main pressure valve also opens due to the differential pressure, thereby allowing the pressure oil in the second pressure oil supply and discharge line to pass through the second bypass line. By flowing into the first pressure oil supply/discharge line, the pressure increase in the second pressure oil supply/discharge line is alleviated. Furthermore, if the poppet of the shuttle valve moves as described above and closes one inlet port, and the pressure in the second pressure oil supply and discharge line increases, the second relief valve opens, and accordingly, the second main pressure The valve is opened again, and a large amount of pressure oil in the second pressure oil supply and discharge line flows into the first pressure oil supply and discharge line by the same action as described above, thereby reducing the pressure in the second pressure oil supply and discharge line. The increase will be moderated secondarily. At the time of reversal, the pressure in the first pressure oil supply and discharge line increases slightly, but since the residual pressure in the second pressure oil supply and discharge line is still high, the reverse action shuttle valve reduces the pressure oil in the first pressure oil supply and discharge line. In addition to the pilot port of the third relief valve, this third relief valve is opened, and the pressure oil applied to the shuttle valve from the second pressure oil supply/discharge line is discharged into the tank via the third relief valve. Therefore, the second main pressure valve is fully opened and suddenly releases the pressure oil in the second pressure oil supply and discharge line to the first pressure oil supply and discharge line. As a result, the pressures of both pressure oil supply and discharge lines are quickly balanced, and the repetition of reverse rotation and forward rotation of the hydraulic motor, that is, the shaking phenomenon of the hydraulic motor is alleviated. Therefore, the above configuration can solve the intended technical problem.

Embodiments The present invention will be specifically described below with reference to embodiments illustrated in FIGS. 2 to 6.

In Figure 2, 21 is a hydraulic power source, 20 is an ABR
Connection type 4 port 3 position directional control valve, 25 is a counterbalance valve, 30 is a brake valve unit, 5
1 is a hydraulic motor, and 52 is a load driven by the hydraulic motor 51.

The hydraulic power source 21 is connected to the inlet port P of the directional control valve 20 via a pump line 28 . Each outlet port A, B of the directional control valve 20 is connected to each pressure line 2.
3 and 24 to the respective inlet ports P ₁ and P ₂ of the counterbalance valve 25, and the tank port R of the directional control valve 20 is open to the tank 22.

The counterbalance valve 25 has a known structure, and has outlet ports A and B connected to both ends of the hydraulic motor 51 via pressure oil supply and discharge lines 31 and 32, and spring chambers 25a and 25b at both ends.
is connected to each pressure line 23, 24 via each pilot line 26, 27, and when the pressure line 23 side is high pressure, move the plunger (not shown) to the right side, and when the pressure line 24 side is high pressure, move the plunger to the left side. I try to do that. When the plunger is moved, for example, to the right from the neutral position _b2 , the pressure oil flows from the inlet port _P1 to the outlet port A, while the pressure oil from the port B is throttled by the notch part of the plunger (not shown). while being released from port B to port _P2 .

In the brake valve unit 30, two bypass lines, namely a first bypass line 41 and a second bypass line 42, are provided between the pressure oil supply and discharge lines 31 and 32, and each bypass line 41 and 42 is provided with a first main pressure valve. 33, a second main pressure valve 34 is provided, respectively.

The first and second main pressure valves 33 and 34 have the same structure, and their structure is shown in FIG. These main pressure valves 33 and 34 are connected to the housing 3
Spools 33e, 3 that are slidable inside 3d, 34d
Equipped with 4e. This spool 33e, 34e
are always urged forward by built-in springs 33c and 34c, and are normally closed. Note that the spools 33e and 34e have throttle passages 33a and 34a. On the other hand, the housings 33d and 34d have inlet ports a on their front end walls.
It also has outlet ports b and b on its peripheral wall, and a pilot port c on its back wall, and a sheet 33f around the inside of the inlet port a.
It is equipped with

Returning to FIG. 2 again, the inlet port a of one of the first main pressure valves 33 is connected to the first pressure oil supply and discharge line 31 side, and the outlet port b thereof is connected to the second pressure oil supply and discharge line 32. However, the inlet port a of the other second main pressure valve 34 is connected to the second pressure oil supply/discharge line 32 , and the outlet port b thereof is connected to the first pressure oil supply/discharge line 31 .

Furthermore, each pilot port c of each main pressure valve 33, 34 is connected to the first and second connection lines 43, 4.
4 to respective inlet ports a and b at both ends of a pressure absorption valve or shuttle valve 35. Second
A specific structure of the shuttle valve 35 shown in the figure is shown in FIG. 3. As shown in FIG. 3, the shuttle valve 35 has a ball-shaped poppet 35a movably housed in a housing 35e. The inlet ports a and b are formed on both end walls of the housing 35e, and the outlet port c is formed on the peripheral wall thereof.
The poppet 35a moves to the lower side due to the pressure difference applied to the inlet ports a and b, and seats 35f and 3 are formed around the inner sides of the inlet ports a and b.
It is designed to sit at 5g. Therefore,
Since a pilot flow occurs until the poppet 35a is seated on the seats 35f and 35g, the pressure increase on the high pressure side can be alleviated by this parrot flow.

Now, returning to FIG. 2 again, the first connection line 43 is connected to the outlet port b of the first main pressure valve 33.
On the side, a second connection line 44 is connected to the outlet port b of the second main pressure valve 34 via relief valves 36 and 37, respectively. Therefore, each relief valve 3
6 and 37 are opened by the pressure of the pressure oil supply and discharge lines 31 and 32, each spool 3 of each main pressure valve 33 and 34 opens.
3e and 34e move to the back wall side of the housings 33d and 34d, and the inlet port a and outlet port b
The pressure oil in the pressure oil supply and discharge lines 31 and 32 can be released to the opposing pressure oil supply and discharge lines 32 and 31 via the bypass lines 41 and 42, respectively.

The outlet port c of the shuttle valve 35 is connected to an inlet port c formed in the center of the peripheral wall of the housing 40d of the reverse action shuttle valve 40 via a discharge line 47 provided with a relief valve 38. This reverse action shuttle valve 40 has a housing 4 as shown in the figure.
The poppet 0d has two poppets 40a and 40b connected by a connecting rod 40c, and is urged to a neutral position by springs 40e and 40f from both sides. In this neutral position, the two poppets 40a and 40b each have a seat 40g,
More than 40h away. And housing 40
outlet ports a and b are formed in each end wall of d, respectively;
Pilot lines 53,
54 are connected to each other. Therefore, when pressure oil acts on either one of the pilot lines 53, 54, for example, when pressure oil acts on the pilot line 54, the space between the pilot line 54 and the discharge line 47 is closed, and the discharge line 47 is closed. Pilot line 5 where pressure oil does not act on line 47
This pilot line 53 is connected to the tank 22 via the discharge side pressure line 23.
It will be opened to the public. That is, the discharge line 47 is connected to either one of the reverse action shuttle valves 40 (the directional control valve 20 and the counterbalance valve 2).
5 is in the neutral position, it is constantly opened to the tank 22 via the pilot lines (from both pilot lines 53, 54), and the vent pressure acting on the relief valve 38 is reduced to the tank pressure (zero). Become.

As the relief valve 38, for example, one having the structure shown in FIG. 5 is used. This relief valve 38 is constructed by slidably housing a spool 38c in a housing 38g and biasing the spool 38c in one direction with a spring 38a. housing 3
The pressure chambers within 8g are composed of a small diameter pressure chamber 38k and a large diameter pressure chamber 38i, and a large diameter pressure chamber 38i.
A collar 38j having an inner diameter d ₂ that is the same as the inner diameter d ₁ of the small diameter pressure chamber 38k is formed inside. Note that the spring side edge 38b of this collar 38j constitutes a seat. A pilot port c communicating with the small diameter pressure chamber 38k is formed on one end wall of the housing 38g, and an inlet port a and an outlet port b are formed on both sides of the collar 38j on the peripheral wall of the housing 38g.

The spool 38c includes a piston 38d that slides within the small-diameter pressure chamber 38k, and a cone-shaped valve 38f that slides in the spring side chamber of the large-diameter pressure chamber 38i.
It consists of a connecting rod 38e that connects a piston 38d and a cone-shaped valve 38f.

The inlet port a is the upstream side 4 of the discharge line 47.
7a, the outlet port b is connected to the downstream side 47b of the discharge line, and the pilot port c is connected to a pilot line 50, which will be described later.

In this relief valve 38, when a pressure greater than the set pressure determined by the spring force of the spring 38a is applied to the pilot port c, the spool 38c moves in the direction of the spring and the cone-shaped valve 38f is separated from the seat 38b. As a result, it is opened, and the pressure oil applied to the inlet port a is transferred to the downstream side 47 of the discharge line 47 from the outlet port b.
It flows out to b. The pressure of the relief valve 38 is set to be much lower than that of the relief valves 36 and 37, for example, about 10 kg/cm ² , and the pressure of the pilot line 50, which is external pressure, rather than self-pressure, is set. Since the valve is opened, almost no chattering occurs.

In FIG. 2, the line 38l is connected to the drain line 47 for draining oil in the large diameter pressure chamber (spring chamber) 38i when the cone valve 38f is separated from the seat 38b.
It is shown that the water is released to the downstream side 47b.

Again in FIG. 2, the pilot line 5
0 is connected to the outlet port c of one reverse action shuttle valve 39, and the inlet ports a and b at both ends of this reverse action shuttle valve 39 are connected to the pressure oil supply and discharge lines 31 and 32, respectively, to each pilot line. 48, 49
are connected via. This reverse action shuttle valve 3
Reference numeral 9 has the same structure as the reverse action shuttle valve 40 except that the positions of the inlet ports a, b and the outlet port c are different. That is, this reverse action shuttle valve 39
In this case, the inlet ports a and b are formed on both end walls of the housing 39c, while the outlet port c is formed in the center of the peripheral wall of the housing 39c.
Therefore, the two poppets 39a and 39b connected by the connecting rod 39d are pressed by the high-pressure side pressure of the pilot lines 48 and 49 to close one seat 39e or 39f, allowing the pressure oil in the low-pressure side line to flow to the outlet port. c and pilot line 5
0 to the pilot port c of the relief valve 38.
Add to.

The brake circuit according to this embodiment has the above configuration, and its operation is as follows. In addition, in the above circuit, by switching the directional control valve 20,
Although the pressure oil supply and discharge lines 31 and 32 can be selected as the pressure oil supply side and the pressure oil discharge side, for convenience of explanation, the line 31 is assumed to be the pressure oil supply side and the line 32 is assumed to be the pressure oil discharge side.

Assume now that the directional control valve 20 is at the neutral position _a2 and the counterbalance valve 25 is at the neutral position _b2 (the state shown in FIG. 3). Therefore, when the directional control valve 20 is switched to the left symbol position _a1 , pressure oil from the hydraulic source 21 is supplied to the pressure line 23, and the pressure line 23 and the pressure oil supply/discharge line 31 become high pressure.
Therefore, this high pressure oil is in the pilot line 26.
through the left spring chamber 25a of the counterbalance valve 25, and the counterbalance valve 25 is switched to the left symbol position _b1 . The pressure oil that has passed through the counterbalance valve 25 reaches the hydraulic motor 51 through the pressure oil supply/discharge line 31, and causes the hydraulic motor 51 to rotate in the forward direction. This rotation of the hydraulic motor 51 drives the load 52 in a predetermined direction. Pressure oil from the hydraulic motor 51 is released into the tank 22 through the pressure oil supply/discharge line 32, the counterbalance valve 25, the pressure line 24, and the directional control valve 20 in sequence.

In the above operation, since the pressure on the pressure oil supply/discharge line 31 side is higher than the pressure oil supply/discharge line 32 side,
The poppet 35a of the shuttle valve 35 is connected to the throttle passage 33a of the first main pressure valve 33 and the first connection line 4.
The pressure oil applied to the inlet port a through 3 causes the inlet and outlet port b to be moved from the neutral position to the right position, thereby closing the inlet and outlet port b. Note that when a normal positive load is applied to the hydraulic motor 51, the relief valves 36, 3
7 and relief valve 38 are closed.

In the above operating state, if the positive load applied to the hydraulic motor 51 becomes an overload, the first main pressure valve 33 functions as a safety valve. That is, at the time of overload, the pressure on the pressure oil supply and discharge line 31 side becomes abnormally high, so the relief valve 36 opens, and therefore the spool 33e of the first main pressure valve 33 closes to the spring 3.
3c retreats against the spring force and opens, and the pressure oil in the pressure oil supply/discharge line 31 flows from the inlet port a of the first main pressure valve 33 to the outlet port b and then through the first bypass line 41. It flows into the supply/discharge line 32.
This prevents the pressure in the pressure oil supply and discharge line 31 from increasing.

Assume now that a positive load is being applied to the hydraulic motor 51, and in this state, the directional control valve 20 is switched to the neutral position _a2 , and the supply of pressure oil to the supply/discharge line 31 is stopped. In general, a tooth contact phenomenon occurs in the power transmission gear mechanism interposed between the hydraulic motor 51 and the load 52 (because there is a discrepancy between the drive gear on the hydraulic motor side and the driven gear on the load side, the driven gear changes according to the inertia of the load). When the gear overruns, the teeth of the driven gear collide with the teeth of the driving gear.) This causes a shock, but this problem is also solved in this embodiment. To explain this point, when the supply of pressure oil to the hydraulic motor 51 is stopped, the counterbalance valve 25 automatically returns to the neutral position _b2 . For this reason, the pressure on the pressure oil supply/discharge line 32 side tends to rise rapidly. At this time, the shuttle valve 35 and the relief valve 37,
The second main pressure valve 34 is activated.

That is, as mentioned above, since the shuttle valve 35 employs the easily movable poppet 35a,
Throttle passage 3 of spool 34e of second main pressure valve 34
4a, the poppet 35a instantaneously moves from the right position to the left due to the high pressure of the pressure oil supply/discharge line 32 applied to the inlet port b of the shuttle valve 35 via the pilot port c and the second connection line 44. At this time, the poppet 35a is connected to the inlet port a.
Since the inlet port a and the inlet port b are in communication until the inlet port a is closed, in other words, the shuttle valve 35 has a transient open characteristic, so a pilot flow is generated until the inlet port a is closed. A differential pressure is generated before and after the spool 34e due to the throttle passage 34a. When this differential pressure increases sufficiently, the spool 34e moves to the left in the figure against the spring 34c, communicating between the inlet port a and the outlet port b of the second main pressure valve 34, and opening the second supply/discharge line 32. Pressure oil is discharged to the first supply/discharge line 31 via the second bypass line 42. As a result, the pressure increase in the pressure oil supply/discharge line 32 is quickly absorbed. Here, the shock caused by the tooth contact phenomenon described above is alleviated. When the transient state of the shuttle valve 35 has passed and the poppet 35a is seated on the seat 35f, and the pressure in the second pressure oil supply/discharge line 32 has risen sufficiently, the relief valve 37 opens, and then the second main pressure valve 34 opens. It functions as a brake valve. In this case as well, the spool 34 of the second main pressure valve 34
e moves to the pilot port c side to open the inlet port a and outlet port b of the second main pressure valve 34. Therefore, the pressure oil in the second pressure oil supply and discharge line 32 flows out from the inlet port a of the second main pressure valve 34 to the outlet port b, and passes through the second bypass line 42 to the first pressure oil supply and discharge line 31. Run to the side.

As mentioned above, the pressurized oil in the second pressure oil supply/discharge line 32 is supplied primarily to the shuttle valve 35 and the second main pressure valve 34, and secondarily after a certain period of time to the second main pressure valve 34. and the relief valve 37, this absorption function has very good responsiveness and can absorb a sufficient amount of pressure oil, rapidly absorbing the shock caused by tooth contact and alleviating it. , and obtain sufficient braking action.

Now, after the supply of pressure oil is stopped, the second pressure oil supply/discharge line 32 side becomes high pressure, and as a result, the next phenomenon that occurs is the compressibility of oil (oil is theoretically incompressible, but in oil Because there are always air bubbles in the oil, oil is highly compressible.) This causes the hydraulic motor 51 to undergo a oscillation phenomenon in which it repeats reverse rotation → forward rotation → reverse rotation, etc.; According to the example, this rocking phenomenon can be effectively prevented or alleviated.

That is, due to the pressure increase on the second pressure oil supply/discharge line 32 side, the hydraulic motor 51 tries to reverse, but due to this reverse phenomenon, the first pressure oil supply/discharge line 31
The pressure on the side is increasing again. On the other hand, the second pressure oil supply/discharge line 32 has a sufficient residual pressure higher than that of the other line 31. Therefore, the reverse action shuttle valve 3
The poppets 39a and 39b of No. 9 are moved to the left by the pressure on the second pressure oil supply and discharge line 32, and the pressure oil in the other pressure oil supply and discharge line 31 passes through the inlet port a and the outlet port c. Relief valve 38
It joins the pilot port c. As described above, the pressure in the pressure oil supply and discharge line 31 is increasing, so the relief valve 38 is opened. Therefore,
The pressure oil in the pilot port c of the second main pressure valve 34, which closed or was about to close at the same time as the pressure rise on the first pressure oil supply/discharge line 31 side, is released from the open relief valve 38 through the outlet port c of the shuttle valve 35. and reaches the inlet port c of the reverse action shuttle valve 40. This reverse action shuttle valve 40 is in the neutral state shown in the figure, since both pressure lines 23 and 24 are open to the tank 22. Therefore, the pressure oil flowing into the inlet port c of the reverse action shuttle valve 40 reaches the respective pressure lines 23 and 24 via the pilot lines 53 and 54 from both outlet ports a and b, and is then released into the tank 22. be done. Therefore, the second main pressure valve 34 is opened again, and the residual pressure on the second pressure oil supply and discharge line 32 side is suddenly released to the first pressure oil supply and discharge line 31 side. Therefore, the pressure balance between both pressure oil supply and discharge lines 31 and 32 is rapidly restored, and the repetition of reverse and forward rotations of the hydraulic motor, that is, the rocking phenomenon is suppressed. The poppets 39a, 39b of the reverse action shuttle valve 39 are pressed by the higher pressure of the pressure oil supply/discharge lines 31, 32, and the lower pressure is applied to the pilot port c of the relief valve 38. The relief valve 38 closes when both the pressure oil supply and discharge lines 31 and 32 reach a sufficiently low pressure, and when a constant positive load is applied to the hydraulic motor 51 while the load 52 is stopped, , the second pressure oil supply and discharge line 32 is brought to a sufficiently low pressure and stabilized while a constant load pressure remains on the pressure oil supply and discharge line 31 side. The pressure of the relief valve 38 is set by a spring 38a, so when the pressure of the pilot line 50 overcomes the force of the spring 38a, it opens and is not affected by the pressure of the discharge line 47.

The above explanation was about the case where a positive load was applied to the hydraulic motor 51 and the supply of pressure oil was stopped in this state. In this case, the driven gear of the gear transmission mechanism precedes the driving gear, so no tooth contact phenomenon occurs. However, after the pressure oil supply is stopped, the load 52 has its inertia force and tries to further rotate the hydraulic motor 51 in the forward direction.
The pressure at 2 becomes even larger, and the reverse phenomenon of the hydraulic motor 51 is about to occur as in the previous case, but
As in the previous case, the pressure in the second pressure oil supply/discharge line 32 is reduced along the route of the shuttle valve 35 → relief valve 38 → reverse action shuttle valve 40, and the swing back phenomenon is alleviated. In this case, the circuit leaves the load pressure on the pressure oil supply and discharge line 32 side, and
Stabilizes by setting the lateral pressure to 0.

Now, the above explanation is about the case where the supply of pressure oil is stopped, but tooth contact shock will similarly occur if the load amount of the load 52 on the hydraulic motor 51 is reversed from positive to negative while the circuit is operating. However, this tooth contact shock is absorbed and relieved by the action of the brake valve unit 30 before entering the counterbalance action.

That is, when the load 52 on the hydraulic motor 51 reverses from positive to negative during operation of the circuit, a braking force is applied to the hydraulic motor 51 by the counterbalance valve 25, so that the pressure oil supply and discharge line 32 High pressure will result. At this time, similarly to the case where the hydraulic motor 51 is forcibly stopped, the high pressure oil in the pressure oil supply/discharge line 32 is primarily transferred to the shuttle valve 35 and the second
It is absorbed by the main pressure valve 34, and secondarily by the second main pressure valve 34 and the relief valve 37, and the tooth contact shock is alleviated.

In this way, the pressure on the pressure oil supply and discharge line 32 side increases gradually, and the pressure on the pressure oil supply and discharge line 31 side also increases due to the supply of pressure oil, so the counterbalance valve 25 It is moved to the right in response to the rise in pressure in the line 31, and releases pressure oil from the pressure oil supply/discharge line 32 to the tank 22 in accordance with the amount of pressure oil supply to perform a counterbalance action.

In the above explanation, the directional control valve 20 is set to the symbol position a ₁ on the left, the pressure oil supply and discharge line 31 is the supply line, and the pressure oil supply and discharge line 32 is the discharge line. Even if the control valve 20 is set to the symbol position _a3 on the right side, the pressure oil supply/discharge line 31 is the discharge line, and the pressure oil supply/discharge line 32 is the supply line, the first group <first bypass line 41, first bypass line 41, 1 main pressure valve 33, 1st relief valve 36> and 2nd group <2nd bypass line 4>
2. Since the second main pressure valve 34 and the second relief valve 37> are arranged symmetrically, it goes without saying that their operation is the same as that described above.

According to the configuration of the above embodiment, it is possible to effectively alleviate the tooth contact shock when the pressure oil supply is stopped and when the load is reversed from positive to negative, and also to prevent the shaking back phenomenon or shaking of the hydraulic motor 51 after the pressure oil supply is stopped. can effectively alleviate dynamic phenomena.

It should be noted that the present invention is not limited to the above embodiments, but can be implemented in various other ways.

For example, the shuttle valve 35 may be constructed as shown in FIG. 4 instead of that shown in FIG. The shuttle valve 35 shown in FIG. 4 is characterized by using a piston-type valve 35d instead of a ball-type poppet. This piston-type valve 35d has seating portions 35i, 35 on both sides thereof for opening and closing inlet ports a, b formed on both end walls of the housing 35h.
It is equipped with j. This piston-type valve 35d is designed to slide on the inner surface of the peripheral wall of the housing 35h, and is easily moved by pressure oil applied to the inlet port a or b, and absorbs pressure oil by expanding the volume due to this movement. That's what I do. Therefore, like the embodiment in FIG. 3, a sudden pressure rise in the high-pressure oil supply/discharge line can be quickly absorbed.

Further, in the embodiment, the relief valve 38
In order to release the pressure oil into the tank 22, a reverse action shuttle valve 40 is used which prevents the pressure oil from flowing into the pressure oil supply side pump line 23 or 24, but if a tank is provided separately. There is no need to provide a reverse action shuttle valve 40 for the cigarette.

Effects of the Invention In the present invention, the pressure increase in the pressure oil discharge line that occurs when the supply of pressure oil to the actuator is stopped is quickly absorbed by the shuttle valve and the main pressure valve, so that the pressure increase in the pressure oil discharge line is prevented. It is absorbed quickly and sufficiently, and the shock on the teeth is alleviated. When reversing, the third relief valve is opened by applying the pressure oil in the pressure oil supply side line to the third relief valve through the reverse action shuttle valve, and the pressure oil in the pressure oil discharge side line that has flowed into the shuttle valve is released. 3rd above
By releasing the pressure oil into the tank through the relief valve, the main pressure valve is fully opened, and the main pressure valve suddenly releases the pressure oil in the pressure oil discharge side line to the pressure oil supply side line, and both pressure oil supply and discharge lines are released. Since the line pressure is balanced, the pressure increase in the pressure oil discharge side line and the supply side line is suppressed, and therefore, the repetition of reverse rotation and forward rotation of the actuator, that is, the rocking phenomenon of the actuator, is alleviated. be done.

Further, in the present invention, the valve for alleviating the pressure rise in the pressure oil discharge line is constructed of a shuttle valve with a simple structure, which is advantageous in terms of cost.

Furthermore, when the pressure oil supply to the actuator is stopped, the main pressure valve not only suppresses the pressure increase in the pressure oil discharge line, but also supplies pressure oil from the high pressure side pressure oil supply and discharge line via the bypass line to the low pressure side pressure oil supply when the load is overloaded. It also has the effect of functioning as a safety valve by releasing it to the exhaust line side.

[Brief explanation of drawings]

Fig. 1 is a conventional brake circuit diagram, Figs. 2 to 6 show an embodiment of the present invention, Fig. 2 is a brake circuit diagram, Fig. 3 is a detailed sectional view of the shuttle valve 35 in Fig. 2, and Fig. 4 is a detailed sectional view of the shuttle valve 35 in Fig. 3 is a detailed sectional view showing a modification of FIG. 3, FIG. 5 is a detailed sectional view showing a specific example of the relief valve 38 in FIG. 2, and FIG. 6 is a detailed sectional view of the main pressure valves 33 and 34 in FIG. 2. FIG. 20...Direction control valve, 21...Hydraulic pressure source, 25...
... Counter balance valve, 30 ... Brake valve unit, 31, 32 ... Pressure oil supply and discharge line, 33,
34... Main pressure valve, 33a, 34a... Throttle passage, 33e, 34e... Spool, 35... Shuttle valve, 35a... Poppet, 35d... Piston type valve, 38... Relief valve, 39... Reverse Operating shuttle valve, 51...hydraulic motor (actuator), 52...load.

Claims (1)

[Claims] 1 first and second connected to actuator 51
First and second bypass lines 41 and 42 are provided between the pressure oil supply and discharge lines 31 and 32, and the first
The bypass line 41 is provided with a first main pressure valve 33 having an inlet port a connected to the first pressure oil supply/discharge line 31 side and an outlet port b connected to the second pressure oil supply/discharge line 32 side, and the second bypass line 42 , inlet port a
A second main pressure valve 34 is provided with the outlet port b connected to the second pressure oil supply and discharge line 42 side and the first pressure oil supply and discharge line 31 side, and the pilot valves of the first and second main pressure valves 33 and 34 are connected. Connect port c to the first and second connection lines 4
3 and 44 respectively inlet ports a and b of the shuttle valve 35
Furthermore, the first connection line 43 is connected to the outlet port b of the first main pressure valve 33, and the second connection line 44 is connected to the outlet port b side of the second main pressure valve 34, respectively. The outlet port c of the shuttle valve 35 is connected to the tank 22 via the third relief valve 38, and the inlet ports a and b at both ends of the reverse action shuttle valve 39 are connected via the relief valves 36 and 37. Each pressure oil supply and discharge line 31, 3
2, and the outlet port c of the reverse action shuttle valve 39 is connected to the pilot port c of the third relief valve 38, and each of the main pressure valves 33 and 34 is 2. A brake circuit comprising a valve having spools 33e and 34e for opening and closing two bypass lines 41 and 42, and throttle passages 33a and 34a communicating an inlet port a and a pilot port c.