JPS63158302A - Brake valve - Google Patents

Abstract

PURPOSE:To reduce a shock by communicating a secondary pressure chamber with the first adjustment chamber through two oil passages, and closing one of the oil passages with the movement in such an direction as enlarging the volume of the first adjustment chamber of a free piston. CONSTITUTION:The first adjustment chamber 39 is demarcated from the second adjustment chamber 40 by slidably engaging a free piston 38 between a casing C and the outer periphery of a relief housing 30. A secondary pressure chamber 8 is communicated with the first adjustment chamber 39 through the first and the second oil passages 43, 44. The second oil passage 44 is so constructed as to be closed when the free piston 38 is moved in such a direction as enlarging the volume of the first adjustment chamber 39. Accordingly, the preset pressure of a cross over type relief valve can be changed through three steps like firstly from a low pressure, secondly to a middle pressure, and at last to a high pressure, so that a shock becomes less than that of the conventional device in which the pressure changes all at once from a low pressure to a high pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention relates to a brake valve used as a brake device for industrial machinery, etc.

(Prior Art) The conventional brake valve shown in FIG. 4.5 has a counterbalance valve 1 connected to the upstream side of a hydraulic motor m, and a main passage 2 connecting the hydraulic motor m and the counterbalance valve 1. .A pair of crossover type relief valves between 3! QI and lz are provided.

The crossover type relief valve fL1,12 has its inlet side 4.5 communicating with the main passage 2.3, and its outlet side 6.7 communicating with the opposite side main passage 3.2.

A free piston 12.13 is connected to the secondary pressure chambers 8 and 9 of the relief valve fB and 12, and this cylinder 10.11 is equipped with a free piston 12.13 and the 11g1 adjustment chamber is connected to the cylinder 10.11. 14.15 and second adjustment room 16°17
It is divided into And this first adjustment room 10.11
is communicated with the secondary pressure chamber 8.9, the second adjustment chamber 16 is communicated with the main passage 3 on the opposite side, and the second adjustment chamber 17 is communicated with the main passage 2 also on the opposite side.

A switching valve (not shown) is connected to the upstream side of the counterbalance valve 1, and when this switching valve is switched, one of the passages 18 and 19 communicates with the pump, and the other passage communicates with the tank. do.

When pressure oil is supplied to either passage, the pressure oil acts on the pilot chamber 20 or 21 of the counterbalance valve 1, switching the counterbalance valve 1 to either the left or right position.

In addition, the above-mentioned counterbalance valve 1, crossover type leaf intervening 1. AC 2 and shockless cylinder IQ, 1
1 are integrally provided in the casing C.

The specific structure of this casing C is as shown in FIG.

That is, the counterbalance valve 1 has a pump boat 2.
2.23 and a motor boat 24.25, and both ends of the spool 26 are connected to the pilot chamber 20.21.
I'm making it happen. This spool 26 is equipped with check valves 27 and 28 that only allow flow from the pump port to the motor boat.

The phosphor type leaf valve fB, sentence 2 is.

Since the left and right sides have the same structure, one relief valve fL+
I will only explain about.

In this relief valve IL+, a relief housing 30 having a seat member 28 fitted at its tip is inserted into a casing C, and a poppet 31 is installed inside the housing 30. This poppet) 31 is the housing 3
Due to the action of the spring 32 installed in the secondary pressure chamber 8 within 0,
Normally, there is an introduction passage 33 which is in pressure contact with the valve seat of the seat member 23 and communicates with the motor boat 24, and a motor boat 25.
The communication with the outlet passage 34 that communicates with the outlet passageway 34 is cut off. An orifice 35 is formed in the poppet 31 of the relief interposition 1, and the introduction passage 33 and the secondary pressure chamber 8 are communicated through the orifice 35. And sheet member 2
The pressure receiving area S2 on the secondary pressure chamber 8 side is made smaller than the pressure receiving area S+ of the poppet 31 facing the 8 side.

When the switching valve is switched, for example, the passage 18 is made to communicate with the pump and the passage 18 is made to communicate with the tank, the pressure oil on the passage 18 side flows into the pilot chamber 2 of the counterbalance valve 1.
0 to move the spool 26 to the right and switch the counterbalance valve 1 to the left position in FIG.

When the counterbalance valve 1 is switched to the left position, the pressure oil in the passage 1 pushes the check valve 27 open.

It flows into the hydraulic motor m via one main passage 2. At this time, the return oil from the hydraulic motor m is returned to the tank from the other main passage 3 via the passage 19.

The hydraulic motor m is started as described above.

At this time, the pressure oil in one of the men's passages 2 flows from the introduction passage 33 through the orifice 35 of the relief interposition 1 to the secondary pressure chamber 8.
At the same time, it flows from this secondary pressure chamber 8 into the first adjustment chamber 14 of the shockless cylinder 16. When pressure oil flows into the first adjustment chamber 14 in this way, the free piston 1
2 moves against the spring of the second adjustment chamber 16 and expands the volume of the first adjustment chamber 14. While the volume of the first adjustment chamber 14 is expanding, the orifice 35 of the relief intervention 1
During this time, the poppet 31 opens due to the pressure difference across the orifice 35.

Then, when the free piston 12 makes a full stroke,
The flow in the orifice 35 will also disappear, so this time,
The set pressure is determined by the area difference between the pressure receiving area S1 on the introduction side of the poppet 31 and the pressure receiving surface mS2 on the secondary pressure chamber 8 side, and the spring load on the secondary pressure chamber 8 side.

That is, while the free piston 12 is moving to increase the volume of the first adjustment chamber 14, the relief valve fL
1 becomes the low pressure setting, and after the free piston 14 has made a full stroke, the pressure becomes the high pressure setting.

As mentioned above, when starting the motor m, the relief valve i1 is set to a low pressure to alleviate the shock at the time of starting. When the motor m starts moving, the relief intervenor 1 is set to a high pressure to maintain the torque of the motor m.

In addition, the pressure in one main passage 2 is determined by the second pressure of the sea cress cylinder 11 connected to the relief intermediary 2.
It will be used for 5 tsubo. Democratic power 1. Due to the spring force of the spring in the second adjustment chamber 17, the free piston 13 moves to the first position.
The hydraulic oil in the first adjustment chamber 15 is transferred to the main passage 3 on the low pressure side via the secondary pressure chamber 9 of the relief intervening 2 and the orifice formed in its poppet. Push out.

Therefore, as long as the motor m is driven, the shockless cylinder 10 connected to the secondary pressure chamber 8 of the relief intermediary 1 is maintained at the full stroke position that maximizes the volume of the first adjustment chamber 14. It will be done. In addition, the shockless cylinder 11 connected to the secondary pressure chamber 9 of the relief interposition 2 is
It is set at an initial position that minimizes the volume of the first adjustment chamber 15.

In the above state, return the switching valve to the neutral position, and both passages 18.
19 to the tank, the pilot chamber 20 of the counterbalance valve 1 also reaches tank pressure, so that the counterbalance valve 1 returns to the neutral position shown and closes the main passage 2.3.

Even when the main passage 2.3 is closed, the motor m continues to rotate due to its inertia, so that the motor m performs a pumping action to discharge the hydraulic oil sucked in from the main passage 2 side into the main passage 3.

Therefore, the main passage 3, which has been at low pressure until now, becomes high pressure, and the high pressure oil flows into the main passage 2 on the opposite side via the relief interposition 2.

Therefore, a short circuit is formed by the main passage 2 → hydraulic motor m → main passage 3 → relief valve 2, and when the pressure oil on the main passage 3 side passes through the relief valve fL2, the inertia energy of the hydraulic motor m is absorbed.

Then, at the moment when the counterbalance valve 1 is switched to the neutral position, the pressure on the main passage 3 side suddenly becomes high and a shock is generated in the hydraulic motor m. At this time, the shockless cylinder 11 operates and the shock absorb.

In other words, since the free piston 13 of this shockless cylinder 11 is set at the initial position as described above, when the pressure in the main passage 3 increases, the pressure oil passes through the secondary pressure chamber 9 of the relief valve fL2. 1st tA Seating Room 1
5, and the free piston 13 is transferred to the second adjustment chamber 17.
is moved against the spring force of the spring, thereby increasing the volume of the first adjustment chamber 15.

If the volume of the first adjustment chamber 15 is increased in this way, the set pressure of the relief intervenor 2 will be lowered as described above, so that the above-mentioned shock will be absorbed.

(Problems to be Solved by the Invention) In the conventional brake valve as described above, as shown in FIG. , the difference becomes too large. Furthermore, since the time t1 for maintaining the set pressure at a low pressure is not long enough, there is a problem in that a shock occurs when changing from a low pressure setting to a high pressure setting.

The purpose of this invention is to provide an area that can be called intermediate pressure in the process where the set pressure of a crossover type relief valve shifts from low pressure to high pressure, so that the set pressure smoothly shifts from low pressure to high pressure, and no shock occurs. It is to do so.

(Means for Solving the Problems) In order to achieve the above object, the present invention communicates the secondary pressure chamber and the first adjustment chamber via two oil passages, and the volume of the first adjustment chamber is As the free piston moves in the direction of enlarging the free piston, one of the oil passages is closed by the free piston.

(Operation of the present invention) Since the present invention is configured as described above, in the initial stage when the free piston moves in the direction of expanding the volume of the first adjustment chamber, the secondary oil The pressure chamber and the first adjustment chamber communicate with each other. Then, in the process of the free piston moving in the above direction, one oil passage is closed.

In other words, when the two oil passages are open, the first y
The flow rate per unit time flowing into the J-setting room increases. In this way, as the flow rate per unit time increases, the pressure in the secondary pressure chamber is maintained at a lower pressure, so the relief valve is also set at a lower pressure.

Furthermore, when one oil passage is closed, the flow rate per unit time decreases, so the moving speed of the free piston becomes slow and the pressure in the secondary pressure chamber becomes relatively high. Therefore, in this case, the set pressure of the relief valve is slightly higher than when the two oil passages are open.

When the free piston makes a full stroke from the above state, the relief valve is operated by the difference in pressure receiving area before and after the orifice, so the set pressure at that time becomes high.

(Effects of the present invention) According to the brake valve of the present invention, the set pressure of the crossover type relief valve is changed through three stages such as low pressure → medium pressure → high pressure, so from low pressure to The shock is less than that of conventional models, which change to high pressure all at once.

(Embodiment of the present invention) FIG. 1.2 showing an embodiment of the present invention shows only one relief valve 1 of the crossover type relief valves installed inside the casing C. The arrangement of the relief interposition 1 and other constituent elements are exactly the same as those of the prior art, so the description of the prior art will be used as is for the same parts.

In the relief valve Ml of this embodiment, an annular free piston 38 is slidably fitted between the casing C and the outer periphery of the relief housing 30, and the first adjustment is performed after three days of this free piston. Room 38 and second adjustment room 4
0.

The free piston 38 has its first adjustment chamber 3
The outer diameter of the 8 side is made slightly smaller, and an annular gap 41 is maintained between it and the casing C. Furthermore, a plurality of communication holes 42 are formed in the free piston 38 in its diametrical direction, and the outer end of the communication hole 42 is opened toward the annular gap 41 side, and the other end is opened on the inner periphery of the free piston 3. The opening is made on the sliding surface.

Furthermore, a first oil passage 43 and a second oil passage 44 are formed in the relief housing 30, but the first oil passage 43 is
The free piston is always open regardless of the movement position on the 3rd day.
The first adjustment chamber 38 and the secondary pressure chamber 8 are always communicated with each other. When the free piston 38 is at the initial position shown in FIG. 1 that minimizes the volume of the first adjustment chamber 39, the second oil passage 44
and the communication hole 42 overlap, and the secondary pressure chamber 8 communicates with the first adjustment chamber 38 via the second oil passage 44 → communication hole 42 → annular gap 41. Therefore, when the free piston is in the above initial position, the secondary pressure chamber 8 and the first adjustment chamber 38
are communicated via the 1st and 2nd oil passages 43 and 44.

When the free piston 38 moves in a direction to expand the volume of the first adjustment chamber 38, the communication hole 42 crosses the second oil passage 44, and communication between the two is cut off as shown in FIG. However, in this embodiment, the free piston 3
The opening of the second oil passage 44 on the sliding surface between the relief housing 30 and the relief housing 30 is expanded outward, and the opening of the second oil passage 44 is expanded outwardly until the free piston 38 moves to some extent from the initial position. It is arranged to communicate with the communication hole 42.

Further, the second adjustment chamber 40 is communicated with the main passage 3 on the opposite side via a throttle 45 and an outlet passage 34 on the outflow side.

Therefore, when the pressure oil on the main passage z side is guided to the introduction passage 33 side, this pressure oil flows into the secondary pressure chamber 8 via the orifice 35 formed in the boppet 31, and at the same time flows into the secondary pressure chamber 8.
．． It also flows into the first adjustment chamber 39 via the two oil passages 43 and 44, and its pressure acts on the free piston 38.

When pressure is applied to the free piston 38, the piston 38 moves to the left in FIG. 2 while pushing out the hydraulic oil in the second adjustment chamber 40 from the throttle 45. When the free piston moves in this way, the volume of the first adjustment chamber 38 expands, and the volume of the secondary pressure chamber 8 is substantially expanded by the expanded volume.

When the volume inside the secondary pressure chamber 8 is expanded, the inside of the secondary pressure chamber 8 is maintained at a low pressure, and the pressure oil in the introduction passage 33 passes through the orifice 35, so there is a pressure difference before and after the orifice 35. occurs, and the poppet 31 opens due to the effect of this pressure difference.

In the process in which the free piston 38 moves as described above, the second oil passage 44 is blocked, as shown in FIG. The flow rate per hour decreases. When the flow rate flowing into the first adjustment chamber 39 decreases in this way, the moving speed of the free piston 38 decreases. Therefore, the secondary pressure chamber 8
Since the amount of volume expansion per unit time also decreases, the pressure difference before and after the orifice 35 also decreases.

Therefore, when the second oil passage 44 is closed, compared to when both the first and second oil passages 43 and 44 are open,
The set pressure becomes relatively high.

Furthermore, when the free piston 38 moves and reaches the full stroke position, pressure oil no longer flows into the orifice 35, so the set pressure of the relief intervention is set at the pressure receiving surface m.
It is determined by the difference between S + and S2 and the spring force of the spring 32.

In other words, when the free piston 38 makes a full stroke, the relief valve fL+ is set to a high pressure.

FIG. 3 shows this relationship. That is, during the time t1 when both the first and second oil passages 43 and 44 are open when the hydraulic motor m is started, the relief intervention 1 maintains the set pressure PI.
maintain. Then, the second oil passage 44 is connected to the free piston 3.
During the time t2 blocked by 8, the set pressure P2 is maintained, and when the free piston 38 reaches the stroke end, the set pressure becomes the set pressure P.

Therefore, when the hydraulic motor m is started, the set pressure of the relief intermediary 1 becomes the low pressure PI, which alleviates the shock at the time of starting. After the motor m is started, its torque does not decrease and the set pressure passes through the intermediate pressure P2 in the process of reaching the high pressure P, so the set pressure changes from the low pressure P1 to the high pressure P. The shock is gone.

Note that in the above embodiment, the second adjustment chamber 40 and the outlet passage 34
Although a diaphragm 45 is provided between the diaphragm 45 and the diaphragm 45, if a spring is interposed in the second adjustment chamber 40, the diaphragm 45 portion may be in a free flow state.

[Brief explanation of the drawing]

Drawings 1 to 3 show embodiments of this invention.
The figure is a sectional view of the relief valve, Figure 2 is a sectional view of the relief valve with the free piston slightly moved, Figure 3 is a graph showing the process of change in the set pressure of the relief valve, and Figures 4 to 6 are 4 is a sectional view, FIG. 5 is a circuit diagram, and FIG. 6 is a graph showing the process of change in the set pressure of the relief valve. C...Casing, 2,3...Main passage, m...
・Hydraulic motor, l+, 12...Crossover type relief valve, 8, 9...Secondary pressure chamber, 35...Orifice, 33...Introduction passage which is the inflow side, 34...Outflow side The outlet passage, S, , S2... pressure receiving area, 38.
...Free piston, 38...First adjustment chamber, 40...
・Second adjustment room, 43.44...Oil passage.

Claims (1)

[Claims] A motor is connected to the downstream side of a pair of main passages formed in the casing, and a pair of crossover type relief valves are provided, the inflow sides of the relief valves are connected to each main passage, and the outflow sides are connected to the inflow side. In addition, an orifice is formed in this relief valve, and the pressure oil on the inflow side is introduced into the secondary pressure chamber through this orifice. While operating based on the difference in pressure receiving area, a free piston is installed inside the casing, and a first adjustment chamber and a second adjustment chamber are separated by the free piston, and the secondary pressure chamber of the relief valve is adjusted to the first adjustment chamber. In the brake valve, the secondary pressure chamber and the first adjustment chamber communicate with each other via two oil passages, and the second adjustment chamber communicates with the main passage on the opposite side. The brake valve is configured such that one of the oil passages is closed by the free piston as the free piston moves in a direction to expand the volume of the brake valve.