KR20030022120A - Hydraulic control arrangement - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control system for damping vibration during movement of a moving work tool, the hydraulic control system comprising a lift cylinder supporting a work tool, a cylinder chamber connected to a pressure medium source or a tank via a control valve device And a damping valve arrangement for connecting one cylinder seal with the hydraulic accumulator and for connecting the other cylinder seal to the tank. According to the present invention, the damping valve device includes a valve installed between the check valve and the hydraulic accumulator to function to limit the pressure, thereby allowing the pressure in the hydraulic accumulator to be limited to a maximum value or less.

Description

Hydraulic Control System {HYDRAULIC CONTROL ARRANGEMENT}

In systems such as, for example, stabilization modules in wheel loaders, control systems are used to dampen pitching vibrations when moving. In patent document DE 197 54 828 C2 filed by the same applicant as the present invention, a stabilization module for a wheel loader can be seen, wherein the boom is supported by a hydraulic cylinder. During the movement, the cylinder seal of the hydraulic cylinder operating in the supporting direction is connected to the hydraulic accumulator. The rod-side ring seal of the hydraulic cylinder is connected to the tank via another logic valve. Between the cylinder seal and the hydraulic accumulator is a valve assembly including a logic valve, which when closed closes the connection between the hydraulic accumulator and the hydraulic cylinder. The end face of the valve body of the logic valve operating in the shut off direction can be released via an electronic directional control valve. The logic valve can thus be opened by the pressure in the cylinder seal and hydraulic accumulator operating in the opening direction.

In order to protect the hydraulic accumulator from excessive pressure occurring in the hydraulic cylinder, another directional control valve is intervened. The directional control valve is set to receive the pressure in the hydraulic accumulator and change to the switching position, in which pressure in the hydraulic accumulator is applied to the end face of the valve body operating in the blocking direction. This prevents the logic valve from returning to its shut-off position again and overloading the hydraulic accumulator. In this mode, the electronic directional control valve returns to its home position against the electromagnetic force through the pilot valve.

Disadvantages of this approach include an electronic directional control valve controlled by a pilot valve to protect the hydraulic accumulator, another directional control valve for safety, and two working together with the ring and cylinder seals of the hydraulic cylinder. Significant cost is associated with the equipment installation, such as the need for a logic valve. Another problem is that the response characteristics under this known stabilization mode, in particular the response characteristics of the pilot valve disposed upstream of the electronic directional control valve, are too slow to prevent overload of the hydraulic accumulator. Another problem is that as the logic valve connected to the ring seal of the hydraulic cylinder is closed simultaneously with the contraction of the hydraulic cylinder, cavitation due to negative pressure in the ring seal occurs.

Patent document DE 39 09 205 C1 describes a hydraulic control system in which a cylinder seal of a hydraulic cylinder is connected with a hydraulic accumulator and a rod side ring seal of a hydraulic cylinder having a tank via an electronic directional control valve while the machine moves. . In order to limit the pressure in the hydraulic accumulator, a pressure reducing valve is arranged between the device and the hydraulic cylinder to limit the pressure in the hydraulic accumulator to below the maximum value. A check valve is provided between the pressure reducing valve and the hydraulic accumulator to prevent the hydraulic accumulator from reducing the load due to the pressure reducing valve. This pressure reducing valve is arranged in a filling line which is connected to a hydraulic accumulator. Another fuel consuming device is connected to this charging line. When the operating conditions are bad, the pressure peak generated by this another fuel consumer is transmitted to the hydraulic accumulator due to the slow reaction speed of the pressure reducing valve. In such a configuration, it is not possible to reduce this pressure peak, so damage to the hydraulic accumulator is inevitable.

The present invention relates to a hydraulic control system according to claim 1.

1 is a circuit diagram of a first embodiment of a control system according to the present invention.

2 is a cross-sectional view of the pressure limiting valve / decompression valve of the damping valve device of FIG. 1.

3 and 4 are circuit diagrams of the second and third embodiments.

FIG. 5 is a circuit diagram of a modified embodiment of the embodiment shown in FIG. 3.

6 is a circuit diagram of a simple embodiment for comparison with the solution described above.

7 is a cross-sectional view of the direction control valve used in the circuit according to FIGS. 1, 3, 4, 5 and 6.

<Description of the symbols for the main parts of the drawings>

2: lift cylinder 4: loader control block

6: pump 8: damping valve device

10: hydraulic accumulator 12: cylinder seal

14: ring seal 16: control valve

18: pressure limiting valve 20: passage

22: passage 24: directional control valve

26: tank passage 28: control passage

30: check valve 32: pressure passage

34: control valve 36: compression spring

38: branch passage 40: control tube

42: shutoff valve 44: branch furnace

46: valve housing 48: valve bore

50: valve member 52: connecting bush

56: spring seal 57: spring retainer

58: pocket 60: control land

62: control land 64: pressurized space

66: accumulating space 68: tank space

70: radial bore 72: axial blind bore

74: measuring piston 76: end face

78: space 80: floating position valve

82: tank ship 84: check valve

86: control tube 88: accumulator ship

90: plunger 92: valve body

94: control tube 96: valve assembly

98: valve plate 100: operating passage

102: storage bore 104: piston

106, 108, 110, 112: ring seal

114: screw plug 116: guide bush

118: internal space 120, 122: ring collar

124: bush 126: sheet

128: closing spring 130: jacket bore

132: spring seal 134: release means

136: release piston

In contrast, it is an object of the present invention to provide a hydraulic control system for vibration damping during movement of a mobile work tool, which can prevent damage to the hydraulic accumulator at minimal cost in terms of equipment installation.

The object of the invention is realized through a hydraulic control system having the features of claim 1.

According to the present invention, a pressure limiting valve is provided at the connection portion between the hydraulic cylinder and the hydraulic accumulator, and a check valve is provided upstream of the pressure limiting valve based on the direction from the hydraulic cylinder to the hydraulic accumulator. According to this relative arrangement, the intermediary action of the pressure limiting valve can limit the pressure in the hydraulic accumulator below a preset maximum value. Here, the load of the hydraulic accumulator on the tank side can be reduced by the check valve provided upstream of the pressure limiting valve.

In this way, even if the pressure peak due to the slow response of the damping valve device reaches the hydraulic accumulator, this pressure peak can be reduced at maximum speed, thereby substantially reducing the safety of the operation of the hydraulic control system compared to the prior art. Can be improved. Another advantage of the present invention is that, in contrast to the structure described above, excellent functions can be realized at low cost in terms of device installation.

The check valve of the present invention is preferably designed to be releaseable. The control pressure released here is released from the hydraulic cylinder or hydraulic accumulator. On discharge from the hydraulic accumulator, the advantage is that the conversion rate of the releaseable check valve can be lowered for higher pressure levels.

The damping valve device of the present invention connects the rod-side ring seal to the tank when the direction control valve is moved and / or the control port of the check valve to one cylinder seal (at the bottom side of the ascending cylinder) or hydraulic accumulator. To be connected to.

The connection of the tank with the ring seal of the hydraulic cylinder can be effected from the actuator valve or the other releaseable check valve. In the latter case, the control port of the other releaseable check valve is subjected to the same pressure as the pressure of the former check valve.

One of the features of the present invention resides in an actuator valve. The ring seal of the hydraulic cylinder is connected to the tank seal through one side of the actuator valve, and the releaseable check valve can be released through the mechanical or hydraulic coupling on the other side. Thus, the pressure of the hydraulic accumulator can be applied to one cylinder chamber of the hydraulic cylinder. This means is particularly characterized by a simple structure. In addition, since the piston of the actuator valve can operate as a topping piston for the check valve, there is no need to separately provide a topping piston for the releaseable check valve as compared with the prior art.

The stability of the operation of the hydraulic circuit can be improved through release means connected with the directional control valve. The directional control valve can switch to its non-operational position even in the event of a pressure peak, controlling the damping device and preventing damage to the hydraulic accumulator.

According to the invention, the damping valve device is implemented as a pressure control valve having a tank port, a pressure port connected with a pressure accumulator, and an inlet port connected with a cylinder chamber. The valve member of the pressure control valve operates on the one hand in accordance with the pressure in the hydraulic accumulator and on the other hand in response to the elastic force of the compression spring and the pressure in one cylinder chamber. When a pressure peak occurs in the hydraulic accumulator, the valve member is switched to the pressure limiting position to limit the pressure in the hydraulic accumulator to below the maximum value.

In order to relieve the pressure in the hydraulic accumulator, it is possible to branch the pressure valve device using a branch furnace with a manually operated shutoff valve. When the shutoff valve is opened, the pressure in the hydraulic accumulator is released to the tank side.

The pressure control valve of the present invention can achieve a more compact design if the metering piston is assigned to the piston member. This instrumentation piston is supported on the housing and guided along the piston member, the end face of which can be affected by the pressure in the hydraulic accumulator.

Other features of the invention are as described in the dependent claims.

1 is a simplified circuit diagram of a control system for controlling a hydraulic cylinder supporting a boom of a moving work tool such as a wheel loader. In the following, the hydraulic cylinder is also referred to as the lift cylinder 2. This lift cylinder can be connected to the hydraulic pump 6 or the tank T via the loader control block 4 indicated by the dotted line.

The illustrated control system comprises a damping valve system 8, shown in dashed lines. As a result, vibrations generated during the movement of the wheel loader, for example, pitching vibrations, are attenuated. This damping valve device 8 connects the lift cylinder 2 and the hydraulic accumulator 10 during movement so that the pressure in the hydraulic accumulator 10 acts in the supporting direction on the lift cylinder.

In the embodiment shown in FIG. 1, the loader control block 4 comprises a pressure port P to which a hydraulic pump 6 is connected. The two actuation ports A, B of the loader control block 4 are respectively connected to the cylinder chamber 12 or the rod side ring chamber 14 of the hydraulic cylinder 2 via the damping valve device 8. The tank T is connected to the tank port S. FIG.

The loader control block 4 comprises an electronic control valve 16 designed as a 4 / 3-way control valve. This electronic control valve blocks the actuation ports A and B from the pressure port P and the tank port S in their spring-biased initial position.

In the first switching position a, the pressure port P is connected to the operating port B, and the operating port A is connected to the tank port T to advance the hydraulic cylinder 2. Here, the pressure medium is supplied to the cylinder chamber 12 and is supplied to the tank T from the ring chamber 14. In the second switching position b, the operating port A is connected to the pressure port P, and the tank port S is connected to the operating port B to reverse the hydraulic cylinder 2.

In order to limit the pressure acting on the actuation port B, the loader control block 4 comprises a pressure limiting valve 18. The actuation port B can be connected to the tank port S via this pressure limiting valve when a pressure above the maximum pressure value of 330 bar is applied.

The damping valve device 8 has two inlet ports R, U and a tank port T connected to the operating ports A, B and the operating ports A ', B'. Two inlet ports R, U are connected to the inlet port of the electronic 4 / 2-way control valve 24 via the passages 20, 22. This directional control valve blocks the passages 20, 22 at their initial position biased by the compression spring. When voltage is applied to the electromagnet of the direction control valve 24, the direction control valve is switched to the second switching position. In this second switching position, the passage 20 is connected to the tank passage 26 connected to the tank port T, and the passage 22 is connected to the control passage 28. The control passage extends from the passage 22 to the control port of the releaseable check valve 30 installed in the pressure passage 32. This pressure passage leads to the pressure port P 'to which the hydraulic accumulator 10 is connected. Between the pressure port P 'and the check valve 30, a control valve 34 having a decompression and pressure limiting function is provided. This control valve 34 is demonstrated in detail next. This control valve 34 is returned to its initial position by the compression spring 36 and by the pressure released from the control passage 28 via the branch passage 38 and reversed by the pressure in the hydraulic accumulator 10. Switch to position. This pressure is released through the control tube 40 in the range of the control port P 'and is transmitted to the end face of the valve member acting against the compression spring 36.

A shutoff valve 42 for relieving the pressure of the hydraulic accumulator 10 with a load is provided in the branch path 44. This shutoff valve is connected to the damping valve device 8 and connects the pressure port P 'to the tank passage 26 while bypassing the control valve 34. Under normal operating conditions of the wheel loader, this shutoff valve 42 is closed.

Suppose the shovel connected to the boom lies on the ground when the wheel loader is first started. Once the motor starts to operate, the control valve 16 is switched to its switching position a. As a result, a pressure medium is supplied from the pump 6 to the cylinder seal 12 of the lift cylinder 2, the ring seal 14 is connected to the tank T so that the lift cylinder 2 is advanced and the shovel is moved from the ground. Is lifted. Pressure in the cylinder chamber 12 is transmitted to the hydraulic accumulator 10 through the pressure passage 32, the check valve 30, and the control valve 34 in its initial position. The pressure in the lift cylinder 2 under no load reaches approximately 30 to 50 bar, depending on the weight of the shovel. This pressure is also present in hydraulic accumulators.

If this pressure is increased by the shovel being loaded during working operation, the control valve 34 is moved from its spring-biased initial position to the control position with the pressure limiting function by the control pressure in the control tube 40. Is switched. In this position, the pressure delivered to the hydraulic accumulator 10 is reduced to a limit value, i.e. 120 bar or less. The control pressure acting in the direction of the compression spring 36 in the branch passage 38 is equal to the tank pressure so that the directional control valve 24 still remains in its initial position.

Since it is not possible to fill the hydraulic accumulator 10 with a pressure greater than 120 bar set under the decompression function, the control valve 34 comes to an intermediate position which is a shut off position.

When the pressure in the hydraulic accumulator 10 increases above the previously mentioned limit value of 120 bar due to the pressure peak, the control valve 34 switches to the pressure limiting position due to the pressure in the control tube 40. In this pressure limit position, the hydraulic accumulator 10 is connected to the tank passage 26 to release the pressure to be below the maximum pressure limit of 150 bar, for example.

In this way, the decompression shock due to the excessive pressure in the hydraulic accumulator 10 due to the operation of the control valve 16 can be prevented at a minimum cost.

When the pressure in the hydraulic accumulator 10 drops below 120 bar, the check valve 30 prevents the pressure from being released to the hydraulic accumulator 10 through the pressure passage 32.

If the wheel loader is traveling around the work area, the control valve 16 is initially in a neutral central position with the ports A, B, P, S blocked against each other. When the directional control valve 24 is switched, the ring seal 14 of the lift cylinder 2 is connected with the tank port T. In this switching position of the directional control valve 24, the control passage 28 is connected to the passage 22 so that the pressure in the cylinder chamber 12 spreads out. By appropriately adjusting the conversion rate of the check valve 30, the pressure in the control passage 28 can sufficiently release the check valve 30, whereby the hydraulic accumulator 10 is controlled by the control valve 34, the open check valve ( 30 and through the wall passage 32 can be connected to the cylinder chamber 12. The lift cylinder 2 here is kept in its support position by the pressure in the accumulator 10. The control valve 34 is here in its initial position. Since the hydraulic accumulator 10 always depends on the pressure when the device is switched, it is possible to reliably prevent the boom from hitting down. Since the right end face of the valve member of the control valve 34 depends on the pressure present in the cylinder chamber 12, the control valve stays in its initial position. Since the hydraulic accumulator 10 always depends on the pressure when the device is switched, the shovel is prevented from falling. In the moving situation, the pressure limiting function of the control valve 34 by the pressure limiting valve 18 is performed to limit the pressure in the pressure passage 32. The pressure limiting valve 18 has a function of preventing cavitation.

According to the present invention, the pressure reducing and pressure limiting functions of the control valve 34 may be given to one valve as shown in FIG.

FIG. 2 is a longitudinal sectional view of the preferred embodiment of the control valve 34 of FIG. 1. The control valve is designed as a pressure reducing / pressure limiting valve that combines pressure reducing and pressure limiting functions into one. The control valve 34 has a valve housing 46 with a valve bore 48 extending into the valve housing. In this valve bore, the pressure port P, the accumulator port A, the tank port T shown by the dotted line, and the control port X of the front end side are formed. In the valve bore 48, the valve member 50 is biased by the stop screw 52 and the compression spring 36 to be guided to its initial position (not shown). The stop screw 52 is screwed to the end face portion of the valve bore 48 shown on the right side of FIG.

The compression spring 36 is provided in the spring chamber 56 extending radially with respect to the valve bore 48 and is supported by the connecting bush 54. The connecting bush is screwed into the housing 46 at the contact portion with the valve bore 48 or the spring seal 56, and a control port X is formed therein. The compression spring 36 acts on the valve member 50 via a spring retainer 57. The valve member has several pockets 58 on its outer circumferential surface, and two control lands 60 and 62 are formed on the end surface thereof.

The pressurized space 64 open to the pressure port P side and the accumulator space 66 open to the accumulator port A side are opened or closed by the control land 62. The connection path between the accumulating space 66 and the tank space 68 is opened or closed by the control land 60.

In the web region present between the pockets 58, the valve member 50 is opened with a radial bore open toward the axial blind bore 72, on which the measuring piston 74 is guided. 70) The radial bore is penetrating. The end of the metering piston 74 protrudes from the valve member 50 and is supported by the end face of the stop screw 52.

Accordingly, the pressure medium flows from the pressure storage space 66 through the radial bore 70 into the space formed by the measurement piston 72 and the axial blind bore 72, and the pressure of the axial blind bore 72. Pressure on the end face 76 acts on the valve member 50 against the elastic force of the compression spring 36.

In the spring-biased initial position, the valve member 50 is in contact with the stop screw 52. Thus, the connection path from the pressure port P to the accumulator port A is opened by the control land 62 while the connection path to the tank port T is closed. This corresponds to the first switching position of the control valve 34 shown in FIG. The pressure in the hydraulic accumulator 10 is transmitted into the spring seal 56 through the control port X, and the pressure component due to the compression of the spring seal 56, together with the force of the compression spring 36, forces the valve member 50 together. Be biased in the closed position. On the other hand, the pressure acting on the end face 76 acts to move the valve member 50 in the opposite direction. The space 78 remaining between the stop screw 52 and the end face of the valve member 50 is connected to the tank port T through a connecting bore, although not shown.

Referring to FIG. 1, the pressure port P is connected to the pressure passage 32, the accumulator port A is connected to the hydraulic accumulator 10, and the tank port T is connected to the tank passage 26, respectively. The passage 38 communicates with the control passage X. When the directional control valve 24 is not in operation, this branch passage 38 is connected to the tank port T via the directional control valve 24, thereby allowing the tank pressure to act on the spring seal 56. do.

In order to lift the shovel, ie to advance the lift cylinder 2, the control valve 16 switches to the switching position a in the manner described above. As a result, the pressure medium flows through the pressure passage 32 to the pressure port P, from which the hydraulic accumulator 10 is reached across the connecting path between the pressurizing space 64 and the accumulating space 66, and thus the hydraulic pressure. The accumulator expands in response to the pressure of the lift cylinder 2. This accumulator pressure also acts on the axial blind bore 72 such that the valve member is forced to act in the opposite direction of the elastic force of the compression spring 36. By filling the hydraulic accumulator 10 through the pressure port P, the accumulator pressure increases, and due to the pressure acting on the end face 76, the valve member 50 moves to the left against the elastic force of the compression spring 36. By shifting, the connecting path between the pressurizing space 64 and the accumulating space 66 is reduced in size through the control land 62. This causes the control valve 34 to function as a decompression.

When a preset limit value, for example 120 bar, is reached, the connection path between the pressurizing space 64 and the accumulating space 66 is completely blocked by the control land 62. This valve position corresponds to the central blocking position of the control valve 40 shown in FIG. That is, in this situation, since the connection paths to the lift cylinder 2 or the hydraulic pump 6 are respectively blocked, the hydraulic accumulator 10 is no longer charged. During the depressurization or blocking action of the control valve 34, the connection path between the pressure storage space 66 and the tank space 68 is continuously blocked.

When a pressure peak to the hydraulic accumulator 10 occurs in the device, for example when a pressure peak is generated by another energy consuming device, the valve member is moved to the left shifted position shown in FIG. 2 due to the increase in the accumulator pressure. Shift to a more advanced position. In this position, the connection path between the accumulator space 66 and the tank space 68 is opened through the control land 60, whereby the valve performs its own pressure limiting function so that the maximum pressure of the hydraulic accumulator is set in advance. Value, for example 150 bar or less. This excess accumulator pressure may occur due to leakage or increased temperature.

In the movement operation, the direction control valve 24 is switched so that the control pressure corresponding to the pressure in the cylinder chamber 12 is transmitted to the control port X through the control passage 28 and the branch passage 38. That is, in the movement operation, the valve member returns to its home position again due to this control pressure and the elastic force of the compression spring 36 which repels the end face 76. In this position, the pressurizing space 64 is connected to the accumulating space 66 via the control land 62, while the connection to the tank space via the control land 60 is blocked.

The control valve 34 may be modified and used as described below.

In the embodiment shown in FIG. 1, the directional control valve 24 is designed as a 4/2 type directional control valve. Here, the ring seal 14 of the lift cylinder 2 is connected to the tank passage 26 via the direction control valve 24 in the movement situation. 3 shows a variant of the control system according to the invention. The direction control valve 24 is here designed as a 3 / 2-way control valve. This directional control valve, at its spring-biased initial position, blocks the passage between the tank passage 26 and the control passage 28 and the cylinder chamber 12. In movement, the direction control valve 24 is switched so that the passage 22 is connected to the control passage 28 to release the check valve 30. In this switching position of the directional control valve 24, the tank passage 26 is blocked.

In addition to the foregoing, the ring seal 14 of the lift cylinder 2 is connected to the tank T via the actuator valve 14 of the loader control block 4. This actuator valve 80 is provided in the tank ship 82, and connects the tank port S and the channel | path 20. As shown in FIG. The actuator valve 80, designed as an electronic 2 / 2-way control valve, shuts off the tanker 82 at the spring-biased initial position. At the time of movement, the actuator valve 80 is switched in position by the action of the switching magnet so that the connection path between the ring seal 14 and the tank T is opened.

In other cases, since the modification of FIG. 3 corresponds to the embodiment described with reference to FIG. 1, the description of FIG. 1 will be omitted for simplicity.

FIG. 4 shows another embodiment similar to FIG. 3. The direction control valve 24 here is designed as a 3 / 2-way control valve and connects the control passage 28 and the tank passage 26 in a spring-biased initial position. In the embodiment of FIG. 4, the passage 20 leading to the ring seal 14 is connected to the tank passage via another releaseable check valve 84. In order to release the check valve 84, the pressure at the outlet side of the directional control valve 24, that is, the pressure in the control passage 28, can be released through the control pipe 86. Thus, the two check valves 30, 84 are released by switching the directional control valve 24 by the pressure in the cylinder chamber 12 of the lift cylinder 2. As a result, the hydraulic accumulator 10 is connected to the cylinder chamber 12, while the ring seal 14 of the lift cylinder is connected to the tank passage 26 via the passage 20 and the check valve 84. An additional check valve 84 allows the pressure medium to be sucked into the ring seal 14 during refilling.

In other cases, since the modification of FIG. 4 corresponds to the embodiment described with reference to FIG. 1, further description thereof will be omitted.

In the above-described embodiment, the check valves 30 and 84 are released by switching the pressure in the cylinder chamber 12 of the lift cylinder 2 and the valve member 50 of the control valve 34 is directed toward the compression spring 36. Headed to. Under certain operating conditions, this pressure may be lower than the pressure in the hydraulic accumulator 10 that is charged during the working cycle. However, in order to release the check valves 30 and 84 and to keep the work tool below the pressure in the cylinder chamber 12, the control valve 34 and the releaseable check valves 30 and 84 must have a high pressure conversion rate. This greatly increases the size of the releaseable check valves 30 and 84.

The embodiment of FIG. 5 is for a variant in which the pressure conversion rate is adjusted to be substantially lower than the embodiment described above. The basic principle of the circuit shown in FIG. 5 corresponds in principle to the embodiment shown in FIG. However, the variant according to FIG. 5 may be moved to that for the embodiment according to FIGS. 1 and 4.

In a manner similar to that in the embodiment shown in FIG. 3, under the moving operation, the ring seal 14 of the lift cylinder 2 is connected to the tank T via the actuator valve 80 shown in FIG. 5. Release of the check valve 30 is made by an electronic directional control valve 24. This directional control valve has the form of a 3 / 2-way control valve in FIG. 5.

In the spring-biased initial position, the directional control valve 24 connects not only the branch passage 38 but also the control passage 28 to the tank passage 26. In accordance with the operation of the directional control valve 24, the connection to the tank passage 26 is interrupted and the branch passage 38 and the control passage 28 are connected to the accumulator line 88 which runs through the control conduit 40. That is, according to the operation of the direction control valve 24, the pressure in the hydraulic accumulator 10 is transmitted to the control passage 28 through the control tube 40 and the accumulator wire 88, and the check valve is operated by the high pressure of the hydraulic accumulator. 30 is released.

In the embodiment shown in FIG. 5, the check valve 30 is released by a pressure equal to the pressure acting on the end face of the valve member 50 of the control valve 34 against the compression spring 36. Due to the higher control pressure, the pressure conversion rate of the check valve 30 can be designed to be substantially smaller.

In the above embodiment, in the moving operation, the ring seal 14 of the hydraulic cylinder 2 is connected to the tank via the directional control valve 24 or the actuator valve 80 or an additional releaseable check valve 84. . In all the embodiments described above the release of the check valve 30 is influenced by the control pressure released through the direction control valve from the cylinder chamber 12 of the hydraulic accumulator 10 or the hydraulic cylinder 2. This control pressure acts on the topping piston to cause the check valve 30 to switch to its open position.

6 is a circuit diagram of one embodiment simply by omitting the topping piston of the check valve 30. The basic configuration of the embodiment shown in FIG. 6 corresponds to the circuit diagram and basic principles of the embodiment shown in FIGS. 3 and 5.

In the embodiment shown in FIG. 6, the direction control valve 24 is designed as a 3 / 2-way control valve. The control passage 28 is connected to the tank passage 26 in the non-operational position of the directional control valve 24 and to the accumulator passage 88 in the switching position, i. In this case, the hydraulically actuated actuator valve 80 is not disposed in the loader control block 4 as shown in Figs. 3 and 5 and is part of the damping means.

In the illustrated embodiment, the actuator valve 80 is in the form of a 2/2 changeover valve and is connected to the valve body 92 of the release valve 30 via a plunger 90. In this way, the switching movement of the actuator valve 80 is transmitted to the check valve 30 so as to switch to the open position. Through this mechanical connection between the actuator valve 80 and the check valve 30, the topping piston required in the above embodiment can be omitted.

The actuator valve 80 blocks the connection path between the tank passage 26 and the ring seal 14 of the lift cylinder 2 in the initial position shown. The end face of the actuator valve 80 operating in the opening direction depends on the pressure in the control passage 28 through the control pipe 94. This causes the tank pressure to act on the control surface described above in the non-operational position of the direction control valve 24.

When a voltage is applied to the electromagnet 96 of the directional control valve 24, the directional control valve is switched to a position connecting the control passage 28 to the accumulator wire 88, so that the control valve 34 has its own The initial position 1 is switched. However, in the variant shown in FIG. 3, this control pressure may be released in the cylinder chamber 12 of the lift cylinder 2.

In addition, a control pressure corresponding to the pressure in the hydraulic accumulator 10 or the cylinder chamber 12 acts on the control surface of the actuator valve 80 through the control pipe 94, whereby the actuator valve is switched to the opening position and lifted. The ring seal 14 of the cylinder 2 is connected with the tank passage 26. The switching movement of the actuator valve 80 is transmitted to the valve body 92 of the check valve 30 through the plunger 90, whereby the check valve is switched to the opening position so that the lift cylinder 2 is moved to the hydraulic accumulator 10. To be supported by pressure.

7 is a cross-sectional view of the valve assembly 96 integrating the actuator valve 80 and the check valve 30.

The illustrated valve assembly 96 includes a valve plate 98 in which two actuation ports A and B, a tank port T which is opened perpendicular to the face shown, and an accumulator port P 'are formed. Include. The actuation port A is connected to the cylinder chamber 12 via the pressure passage 32, and the actuation port B is connected to the ring seal 14 of the lift cylinder 2 via the actuation passage 100, respectively ( 6). The hydraulic accumulator 10 is connected to the accumulator port P '.

A valve bore 102 is formed across the valve plate 96, in which the valve body 92 of the check valve 30 and the piston 104 of the actuator valve 80 are housed.

Ring bores 106, 108, 110 and 112 are formed in the receiving bore 102, which has a tank port T, an operation port B, an operation port A and an accumulator port P '. ) Are each connected. The receiving bore 102 has its front face blocked by a screw plug 114, and the other side thereof is blocked by a guide bush 116 guiding the piston 104. The guide bush 116 has a plurality of jacket depressions 117, 119 that open up to the ring seals 106, 108, whereby the pressure medium enters into the interior space 118 of the guide bush 116. Can be introduced.

On one end surface of the piston 104, two radially protruding ring collars 120 and 122 are formed to slidably contact the outer circumferential wall of the inner space 118. A portion of the inner space 118 adjacent to the end face of the ring collar 122 is connected to the tank port T and thus is not subjected to pressure. In the right end face in FIG. 7, the guide bush 116 is sealedly inserted into the bush 124, and the plunger 90 is guided to slide in the bush 124.

One end of the plunger 90 rushes into the inner space 118 of the guide bush 116 and contacts the adjacent end face of the piston 104. The other end of the plunger 90 protrudes into the ring seal 110 and is in contact with or slightly separated from the valve body of the check valve 30 provided at the right end of the receiving bore 102. Within this range, the receiving bore 102 has a valve seat 126 in which the conical end of the valve body 92 in the form of a hollow piston against the valve seat is connected to the closing spring 128. Biased by The closing spring 128 is supported by the closing spring 114 and is in contact with the annular end surface inside the valve body 92.

The valve body 92 has a plurality of jacket bores 130 in the range of the conical end. Through this jacket bore 130 a spring seal 132 for the closing spring 128 is connected to the accumulator port P ', whereby the check valve is connected to the pressure of the hydraulic accumulator 10 and the closing spring 128. ) The elastic force is received in the closing direction. In the opening direction, the pressure in the ring chamber 110 corresponding to the pressure in the cylinder chamber 12 acts on the valve body 92.

The valve body 92 is above the valve seat 126 in its initial position, thereby disconnecting the connection path between the cylinder chamber 12 and the hydraulic accumulator 10. The piston 104 is moved to its leftmost position by the plunger 90. In this position, the ring collar 122 closes the opening 119 of the jacket, and the opening 117 of the jacket opens. Accordingly, the ring seal between the two ring collars 120 and 122 is subjected to tank pressure.

The control port X, which is connected to the control passage 28 and the outlet port of the directional control valve 24 via the control tube 94, is opened to the pressure space side adjacent to the left end surface of the piston 104. Therefore, the tank pressure acts on this control port X at the position where the direction control valve 24 does not operate.

When the directional control valve 24 is switched by the electromagnet 96, the pressure of the hydraulic accumulator 10 (for the embodiment according to FIG. 6) or the pressure in the cylinder chamber 12 (for the embodiment according to FIG. 3) Acts on the control port (X). Since the piston 104 has a wider end face than the end face of the valve body 92 operating in the opposite direction, the piston 104 shown in FIG. 7 moves to the right by a control pressure acting on the left side, As a result, the ring collar 122 opens the opening 119 of the jacket to open the connection path from the operating port B to the tank port T communicating with the ring seal 108. Movement of the piston 104 in the axial direction is transmitted to the valve body 92 through the plunger 90 so that the valve body is disengaged from the valve seat 126 and from the hydraulic accumulator 10 to the cylinder chamber 12. The link is opened. The lift cylinder 2 is thus supported by the pressure in the hydraulic accumulator 10.

6 shows an embodiment with damping valve means. This embodiment has a release means 134 for the directional control valve 24. In this embodiment, the release means 134 is embodied as a release piston 136. This release piston operates in the same direction as the compression spring of the direction control valve 24. The back side of the releasing piston 136 receives pressure in the pressure passage 32 through the actuation passage 138. The operating surface of the releasing piston 136 is designed such that when a pressure peak occurs, the direction control valve 24 can return to its non-operating position against the electromagnetic force of the electromagnet. Accordingly, the damping means is turned off so that the hydraulic accumulator 10 can be prevented from being damaged. Of course, this release means may equally be provided in the embodiment of FIGS. 1 to 5. In addition to the mechanical release means, an electronic pressure release means may also be provided, such that the directional control valve 24 will return to its non-operating position when the maximum pressure in the pressure space 32 or the hydraulic accumulator 10 is exceeded. Can be.

The description so far relates to a hydraulic control system for damping vibrations during movement of a moving work tool, which is a lift cylinder supporting the work tool, a cylinder connected to a pressure medium source or a tank via a control valve system. Seal and a damping valve system for connecting one cylinder seal with the hydraulic accumulator and for connecting the other cylinder seal to the tank. According to the present invention, the damping valve system includes a valve installed between the check valve and the hydraulic accumulator which functions to limit the pressure, thereby allowing the pressure in the hydraulic accumulator to be limited to below the maximum value.

Claims (15)

Hydraulic cylinder (2) for supporting the working mechanism, Cylinder seals 12, 14 connected to the pressure medium source 6, 10 or tank T via a control valve device 4, and Damping valve arrangement 8 for connecting one cylinder seal 12 to the hydraulic accumulator 10 and the other cylinder seal 14 to the tank. Including, The damping valve device A valve 34 that affects the pressure in the hydraulic accumulator 10, Check valve 30 to prevent pressure medium from flowing back from the hydraulic accumulator 10 into the cylinder chamber 12. Including, The check valve 30 is provided between the one cylinder chamber 12 and the valve 34, The valve 34 has a pressure limiting function to release the pressure medium from the hydraulic accumulator 10 to the tank T when the limit pressure is exceeded. Hydraulic control system for vibration damping during movement of a moving work tool. In claim 1, The check valve (30) is designed to be releasable and the control pressure released is tapped out of the one cylinder chamber (12) or the hydraulic accumulator (10). In claim 2, The damping valve device comprises a directional control valve 24, preferably an electronic directional control valve, The other cylinder seal 14 is connected to the tank via a directional control valve in one switching position and / or the control port of the check valve 30 is connected to the one cylinder seal 12 or the hydraulic pressure. Connected to the accumulator 10 Hydraulic control system. The method according to any one of claims 1 to 3, And an actuator valve (80) to allow the other cylinder seal (14) to be connected to the tank. The method of claim 2 or 3, Another releaseable check valve 84, The control port of the check valve is operated at the same pressure as the check valve 30, it is controllable to open the connection path between the other cylinder chamber 14 and the tank (T) through the check valve Hydraulic control system. In claim 4, The check valve (30) can be switched to its opening position through the actuator valve (80). In claim 6, The piston (104) of the actuator valve (80) acts as a topping piston for the check valve (30). The method according to any one of claims 2 to 7, A release means (134) is connected to the directional control valve (24) so that the release means allows the directional control valve (24) to switch to its spring biased non-operational position. In claim 8, The release means comprises a release piston (136) acting on the valve member of the directional control valve (24), the release piston operating in accordance with the pressure of the one cylinder chamber (12). The method according to any one of claims 1 to 9, The valve 34 receives the pressure in the hydraulic accumulator 10, or the pressure in the one cylinder chamber 12 of the compression spring 36 and the hydraulic cylinder 2 or the pressure in the hydraulic accumulator 10. Receiving valve member 50, The hydraulic accumulator port A connected to the hydraulic accumulator and the pressure port P or the tank port T can be controlled to be opened in accordance with the accumulator pressure. Hydraulic control system. In claim 10, The measuring piston is guided while being supported along the housing of one end of the valve member 50 of the valve 34, The space formed by the metering piston 74 and the valve member 50 receives pressure in the hydraulic accumulator 10. Hydraulic control system. The method according to any one of claims 1 to 11, The control valve device (4) has a pressure limiting valve (18) that is adjustable to limit the pressure in the one cylinder chamber (12). In claim 12, The pressure limiting valve (18) is designed to have a function of preventing cavitation. The method according to any one of claims 1 to 13, An outlet port of the directional control valve (24) connected to the control port of the check valve (30) is connected to the spring seal (56) of the valve (34) through a control passage (38). The method according to any one of claims 1 to 14, A branch passage 44 for bypassing the valve 34, The branch passage is provided with a shutoff valve 42 for allowing the hydraulic accumulator 10 to be connected to the tank T. Hydraulic control system.