JPH0366524B2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention provides a brake circuit that absorbs tooth contact shock that occurs when the supply of pressure oil is stopped or when the direction of the load on the actuator is reversed from positive to negative. Regarding the brake circuit.

Prior Art For example, in a hydraulic excavator, a hydraulic circuit as shown in Fig. 1 is used to drive the excavator's rotating body with a hydraulic motor. During the process of driving a rotating body, if the load acting on the rotating body changes from a positive load to a heavy load, that is, if the load on the hydraulic motor that drives the rotating body reverses from positive to negative, a shock occurs. There's a problem. This problem is due to the following reasons.

That is, in order to transmit the power from the hydraulic motor 6 to the revolving body (load) of the shovel, a gear mechanism as shown in FIG. 2 is generally employed.

By the way, as is well known, a backlash 3 is formed between the teeth of the driving gear 1 and the driven gear 2. Therefore, assume that in the hydraulic circuit configured as described above, the direction control valve 15 is switched to the neutral position, the counterbalance valve 14 is returned to the neutral position, and the operation of the hydraulic motor 6 is stopped. At this time, if line 8 is used as a pressure oil supply line and line 9 is used as a pressure oil discharge line, the pressure in line 8 will be approximately equal to the tank line pressure, and the pressure in discharge line 9 will be higher than the pressure in supply line 8. However, one of the relief valves 11 opens and the high pressure oil on the line 9 side flows out to the line 8 side. This applies a brake to the hydraulic motor 6. On the other hand, since the load 7 has an inertial force, it does not stop immediately, so the driven gear 2 connected to the load overruns, and as a result, the teeth 2a of the driven gear 2 and the teeth 1a of the drive gear 1 of the hydraulic motor 6 collide, and this causes a shock. A similar tooth contact shock occurs when the load on the hydraulic motor 6 is reversed from positive to negative.

This problem is caused by the attempt to solve the problem with a single relief valve having only one set pressure to release high-pressure oil in the discharge line to a low-pressure supply line.

Technical problem of the present invention Therefore, the technical problem to be solved by the present invention is not to solve it with one relief valve, but to quickly and sufficiently absorb the shock against the teeth.
The shock absorption process is divided into two stages, and the pressure in the discharge line is immediately absorbed primarily in the first absorption process.
The objective then is to obtain the original brake pressure in the subsequent process.

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, first and second bypass lines are provided between the first and second pressure oil supply/discharge lines connected to an actuator such as a hydraulic motor, and an inlet port is connected to the first pressure oil supply/discharge line to the first bypass line. A first main pressure valve is provided on the supply/discharge line side with its outlet port connected to the second pressure oil supply/discharge line, and a first main pressure valve is provided on the second bypass line with its inlet port connected to the second pressure oil supply/discharge line and its outlet port connected to the second pressure oil supply/discharge line. A second main pressure valve connected to the first pressure oil supply/discharge line is provided, and the pilot ports of the first and second main pressure valves are connected to each inlet and outlet port of the pressure absorption valve via the first and second connection lines. Furthermore, the first connection line is connected to the first bypass line downstream of the first main pressure valve, and the second connection line is connected to the second bypass line downstream of the second main pressure valve, respectively, via relief valves. The pressure absorption valve is configured, for example, by a shuttle valve, that is, a valve having a poppet that can be freely moved by the pressure of the high-pressure oil supply and discharge line, and each of the main pressure valves is configured such that each of the relief valves is opened. The valve is opened by the pressure of the pressure oil supply/discharge line applied to the inlet port when the valve is opened, and is equipped with a spool having a throttle passage that communicates the inlet port with the pilot port.

According to the above configuration, the first pressure oil supply and discharge line is now the pressure oil supply line, the second pressure oil supply and discharge line is the pressure oil discharge line, and when the pressure oil supply is stopped, the pressure in the second pressure oil supply and discharge line is If the pressure suddenly increases, the poppet of the pressure absorption valve will momentarily move in the direction of absorbing pressure, and this movement will cause 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 pressure absorption valve side and quickly absorbs this pressure oil, and the second main pressure valve also opens due to the differential pressure, thereby alleviating the pressure rise in the second pressure oil supply and discharge line. be. Also, slightly later than this, the second
The pressure in the line between the pilot port of the main pressure valve and the second relief valve increases, and this second relief valve opens.As a result, the spool of the second main pressure valve enters the braking state, which causes the secondary Specifically, the pressure in the second pressure oil supply/discharge line is automatically controlled in two stages, and a large amount of the pressure oil flows out into the first pressure oil supply/discharge line through the second bypass line. Therefore, the shock that hits the teeth is rapidly and sufficiently absorbed, and the intended technical problem can be solved.

Embodiments The present invention will be specifically described below with reference to embodiments illustrated in FIGS. 3 to 7. The present embodiment is intended not only to alleviate the shock caused by tooth contact, but also to alleviate the phenomenon of swinging back of the hydraulic motor when the supply of pressure oil is stopped.

In Figure 3, 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 as an actuator, 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, the plunger (not shown) is on the right side, and when the pressure line 24 side is high pressure, the plunger is on the left side. I try to move. 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, 34 are provided with slidable spools 33e, 33e, 34b in housings 33d, 34d.
34e. This spool 33e, 34
E is always biased forward by built-in springs 33c and 34c, and is of a normally closed type. Note that the spools 33e and 34e have throttle passages 33a and 34a. On the other hand, the housings 33d and 34d each have an inlet port a on the front end wall, outlet ports b and b on the peripheral wall thereof, and a pilot port c on the back wall thereof. It is equipped with a seat 33f.

Returning to FIG. 3 again, the inlet port a of one of the first main pressure valves 33 is connected to the first pressure oil supply/discharge line 31, and the outlet port b thereof is connected to the second pressure oil supply/discharge line 32. 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 the respective inlet ports a and b at both ends of the pressure absorption valve 35.

A shuttle valve is used as the pressure absorption valve 35.
A specific structure of the shuttle valve 35 shown in FIG. 3 is shown in FIG. 4. As shown in FIG. 4, 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 the seat 35 is formed around the inside of each inlet port a and b.
f, 35g. Therefore, a pilot flow is generated until the poppet 35a is seated on the seats 35f, 35g, so that the pressure increase on the high pressure side can be alleviated by this parrot flow.

Now, returning to FIG. 3 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 D side 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 pressure absorption valve 35 is connected to the 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 40 has a housing 40 as shown in the figure.
2 connected to d by a connecting rod 40c.
It has two poppets 40a and 40b, and is urged to a neutral position by springs 40e and 40f from both sides. In this neutral position, both the two poppets 40a and 40b are connected to the seats 40g and 40b.
Farther than 0h. And housing 40d
Outlet ports a and b are formed in each end wall of the pilot line 53 and 5, respectively, and pilot lines 53 and 5 are connected to the outlet ports a and b, respectively.
4 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 53 where pressure oil does not act on line 47
This pilot line 5
3 is opened to the tank 22 via the discharge side pressure line 23. That is, the discharge line 47 is routed through the pilot line of either one of the reverse action shuttle valves 53, 54 (from both pilot lines 53, 54 when the directional control valve 20 and counterbalance valve 25 are in the neutral position). Therefore, the vent pressure acting on the relief valve 38 becomes the tank pressure (zero).

As the relief valve 38, for example, one having the structure shown in FIG. 6 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. In addition,
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 provided on one end wall of the housing 38g, and an inlet port a and an outlet port b are provided on both sides of the collar 38j on the peripheral wall of the housing 38g.
are formed respectively.

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 is not the self pressure but the external pressure. Since the valve is opened by , almost no chattering occurs.

In addition, in FIG. 3, the line 38l is connected to the drain line 47 for draining the 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. 3, 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 configuration 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, in this shuttle valve 39, the inlet ports a and b are connected to the housing 39, respectively.
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 50 to pilot port c of relief valve 38.

The brake circuit according to this embodiment has the above configuration, and its operation is as follows. In the above circuit, by switching the directional control valve 20, 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, but for convenience of explanation, the line 31 is selected as the pressure oil The supply side and line 32 are 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. The pressure oil from the hydraulic motor 51 is supplied to the pressure oil supply/discharge line 32 and the counterbalance valve 2.
5. It passes through the pressure line 24 and the directional control valve 20 in sequence and is released into the tank 22.

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 pressure absorption valve 35 is connected to the throttle passage 33a of the first main pressure valve 33 and the first connection line 4.
Pressure oil applied to the inlet port a through the hydraulic motor 51 moves it from the neutral position to the right position and closes the inlet/outlet port b. Note that when a normal positive load is applied to the hydraulic motor 51, the relief valve 3
6, 37 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. On the other hand, since the supply of pressure oil to the counterbalance valve 25 is stopped,
The counterbalance valve 25 has automatically returned to the neutral position _b2 . Therefore, the pressure on the pressure oil supply/discharge line 32 side is about to rise rapidly. At this time, the pressure absorption valve 35, the relief valve 37, and the second main pressure valve 34 operate.

That is, as mentioned above, since the pressure absorption valve 35 employs the easily movable poppet 35a,
Throttle passage 3 of spool 34e of second main pressure valve 34
4a, the poppet 35a 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/outlet port b of the pressure absorption valve 35 via the pilot port c and the second connection line 44. At this time, until the poppet 35a closes the inlet port a, the inlet port b and the inlet port a
In other words, since the pressure absorption valve 35 has a transient open characteristic, a pilot flow occurs until the inlet port a is closed, and a differential pressure is created across the spool 34e by the throttle passage 34a. Occur. When this differential pressure increases sufficiently, the spool 34e moves to the left in the figure against the spring 34c, and communicates between the inlet port a and the outlet port b of the second main pressure valve 34, and connects the second supply/discharge line. 3
2 pressure oil is passed through the second bypass line 42 to the first
It is discharged into the supply/discharge line 31. 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. Then, the transient state of the pressure absorption valve 35 passes,
When the poppet 35a is seated on the seat 35f and the pressure in the pressure oil supply/discharge line 32 is sufficiently increased, the relief valve 37 opens and the second main pressure valve 34 then functions as a brake valve. In this case as well, the spool 34e of the second main pressure valve 34 moves to the pilot port c side and opens the second main pressure valve 34.
The inlet port a and outlet port b of the main pressure valve 34 are opened. Therefore, the second pressure oil supply and discharge line 32
The pressure oil flows out from the inlet port a of the second main pressure valve 34 to the outlet port b, passes through the second bypass line 42, and escapes to the first pressure oil supply and discharge line 31 side.

As described above, the pressurized oil in the second pressure oil supply/discharge line 32 is supplied primarily to the pressure absorption valve 35 and the second main pressure valve 34, and after a certain period of time, secondarily to the second main pressure valve. 34 and 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 contact with the teeth and alleviating it. Moreover, sufficient braking action can be obtained.

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 repeat reverse rotation, forward rotation, reverse rotation, and so on, causing a so-called swing back phenomenon. According to the embodiment, this swing back phenomenon can also be 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 of the first pressure oil supply/discharge line 31 increased, is removed from the outlet port c of the pressure absorption valve 35 by the relief valve 38, which is now in an open state. to the inlet port c of the reverse action shuttle valve 40. This reverse action shuttle valve 40 is connected to the pressure lines 23, 2.
4 are open to the tank 22, and are in the neutral state shown in the figure. Therefore,
The pressure oil flowing into the inlet port c of the reverse action shuttle valve 40 is passed through the pilot lines 53 and 54 from both outlet ports a and b to each pressure line 23,
24 and then released into tank 22. Therefore, the second main pressure valve 34 is opened again, and the residual pressure is transferred to the second pressure oil supply and discharge line 32 side.
It is suddenly released to the pressure oil supply and discharge line 31 side. For this reason,
The pressure balance between both pressure oil supply and discharge lines 31 and 32 is rapidly restored, and the repetition of reverse and forward rotation of the hydraulic motor, that is, the swinging back phenomenon is suppressed.
Poppets 39a, 39b of reverse action shuttle valve 39
is pressed by the higher pressure of the pressure oil supply/discharge lines 31 and 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. Note that 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 this spring 38a, it opens, and the discharge line 47
unaffected by pressure.

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. When the gear is stopped, the driven gear of the gear transmission mechanism is ahead of the driving gear, so no tooth contact phenomenon occurs. However, when 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, so the pressure in the pressure oil supply/discharge line 32 further increases, and the hydraulic motor 51
A reversal phenomenon is about to occur in the same way as in the previous case, but the second pressure oil supply and discharge line 32
The pressure is reduced along the route of pressure absorption valve 35→relief valve 38→reverse operation 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
It stabilizes when the 1 side pressure is set to 0.

Now, the above explanation is about the case where the supply of pressure oil is stopped, but a tooth contact shock will similarly occur if 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 alleviated 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/discharge line 3
2 is high pressure. At this time, similar to the case where the hydraulic motor 51 is forcibly stopped, the high pressure oil in the pressure oil supply/discharge line 32 is supplied primarily to the pressure absorption valve 35 and the second main pressure valve 34, and secondarily to the is the second main pressure valve 3
4 and the relief valve 37, and the shock against the teeth is alleviated.

In this way, while the pressure on the pressure oil supply/discharge line 32 side gradually increases, the pressure on the hydraulic supply/discharge line 31 side also increases due to the supply of pressure oil. It is moved to the right in response to an increase in pressure, and releases pressure oil from the pressure oil supply/discharge line 32 to the tank 22 in accordance with the amount of pressure oil supplied to perform a counterbalance action. In addition, in the above explanation, the case where the directional control valve 20 is set to the symbol position a ₁ on the left side, the pressure oil supply/discharge line 31 is the supply line, and the pressure oil supply/discharge line 32 is the discharge line is explained. control valve 20
Set symbol position a ₃ on the right side, pressurized oil supply/discharge line 3
Even if 1 is used as a discharge line and the pressure oil supply/discharge line 32 is used as a supply line, the first group [first bypass line 41, first main pressure valve 33, first relief valve 36] and second group [ Second bypass line 42, second main pressure valve 34, second relief valve 3
7] are arranged symmetrically, it goes without saying that the effect is the same as that described above.

According to the configuration of the above embodiment, it is possible not only to effectively alleviate the tooth contact shock when the pressure oil supply is stopped and when the load is reversed from positive to negative, but also to prevent the hydraulic motor 51 from swinging back after the pressure oil supply is stopped. can be effectively alleviated.

Note that the present invention is not limited to the above-mentioned embodiments, and can be implemented in various other embodiments.

For example, the pressure absorption valve 35 may be constructed as shown in FIG. 5 instead of the one shown in FIG. The pressure absorbing valve 35 shown in FIG. 5 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, similarly to the embodiment in FIG. 4, a sudden pressure rise in the high-pressure side 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. For example, this reverse action shuttle valve 40 does not need to be provided.

Effects of the Present Invention The present invention provides a pair between a pressure absorbing valve and a main pressure valve having a poppet that can temporarily move the pressure of the pressure oil discharge line due to the inertial force of the load. Since the pressure is absorbed by the pressure oil discharge line and the pressure is absorbed secondarily by the relief valve and the main pressure valve, the pressure increase in the pressure oil discharge line is absorbed quickly and sufficiently.
Tooth contact shock can be effectively alleviated and the desired purpose can be achieved.

Furthermore, since the pressure absorption valve has the simple structure described above, it is advantageous in terms of cost.

Furthermore, the main pressure valve not only suppresses the rise in pressure in the pressure oil discharge line, but also in the event of positive load overload or heavy load overload, the pressure oil in the high pressure side pressure oil supply and discharge line is reduced to low pressure via the bypass line. It also functions as a safety valve by releasing it to the side pressure oil supply and drainage line.

Furthermore, by effectively absorbing the pressure rise in the pressure oil discharge line, this tooth contact shock has the effect of alleviating the phenomenon of swinging back of the actuator when the pressure oil supply is stopped.

[Brief explanation of drawings]

Fig. 1 is a conventional hydraulic circuit diagram, Fig. 2 is an explanatory diagram for explaining the tooth contact phenomenon, Figs. 3 to 7 show embodiments of the present invention, Fig. 3 is a brake circuit diagram, and Fig. 4
The figure is a detailed sectional view of the pressure absorption valve 35 in FIG. 3, and FIG. 5 is a detailed sectional view showing a modification of FIG. 4.
6 is a detailed sectional view showing a specific example of the relief valve 38 in FIG. 3, and FIG. 7 is a detailed sectional view of the main pressure valves 33 and 34 in FIG. 3. 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... Pressure absorption valve, 35a... Poppet, 35d... Piston type 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, each inlet port a, b of the pressure absorption valve 35
and further connect the first connection line 43 to the first
The second connection line 44 is connected to the outlet port b side of the 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.
The pressure absorption valve 35 has a poppet 35a that can be freely moved by the differential pressure between the first and second connection lines 43 and 44, and Each of the above main pressure valves 3
Reference numerals 3 and 34 include spools 33e and 34e that are opened by the pressure of the pressure oil supply and discharge line applied to the inlet port a when the relief valves 36 and 37 are open, and furthermore, spools 33e and 34e that are opened by the pressure of the pressure oil supply and discharge line that is applied to the inlet port a when the relief valves 36 and 37 are open, and furthermore, the spools 33e and 34e are connected to each inlet port a and each pilot port. c,
A brake circuit characterized by comprising throttle passages 33a and 34a that communicate with c.