JP3727737B2 - Shock absorber for hydraulic circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a shock mitigation device for mitigating shock when an actuator is operated by switching a switching valve.
[0002]
[Prior art]
A configuration in which a plurality of switching valves are connected to one pump, a predetermined actuator is connected to each switching valve, and the actuators are controlled by switching the switching valves has been conventionally known.
The switching valve is configured such that the opening degree is controlled according to the switching position.
[0003]
[Problems to be solved by the invention]
In the conventional apparatus as described above, for example, when the switching valve is suddenly switched, there is a problem that a shock at the time of activation occurs on the actuator side. This is because if the switching valve is switched suddenly, the opening degree also increases correspondingly, and the supply flow rate at the time of startup increases.
An object of the present invention is to provide a shock mitigation device that does not generate a shock at start-up even when the switching valve is suddenly switched.
[0004]
[Means for Solving the Problems]
The present invention presupposes a hydraulic circuit that drives a plurality of actuators with at least one pump, connects a switching valve to each actuator, and controls the operation of the actuator by switching the switching valves.
Based on the above circuit, the first aspect of the present invention is to connect a shock relief valve to the upstream side of the switching valve at the most upstream position among the switching valves , and to discharge the pump in its normal state. A part of the oil is returned to the tank, and when the pilot pressure is applied to the pilot chamber of the shock relief valve, the discharge oil is prevented from returning to the tank, and the pilot pressure is applied to the pilot chamber of the shock relief valve. A pilot line is provided, and the pilot line is connected to a branch passage communicating with the tank when each switching valve is in the neutral position, and when one of the switching valves is switched from the neutral position , the branch passage and the tank are connected to each other. This is characterized in that the communication is blocked and the pilot pressure is generated in the pilot line .
[0005]
Therefore, if all the switching valves are in the neutral position, no pilot pressure is generated in the pilot line. For this reason, the shock relief valve is kept in a normal state. If the shock relief valve is in the normal state, a part of the pump discharge oil is returned to the tank through the shock relief valve.
When one of the switching valves is switched, a pilot pressure is generated in the pilot line, and the shock relief valve is switched by the action of the pilot pressure. When the shock relief valve is switched in this way, the entire amount of pump discharge oil is supplied to the switching valve side.
[0006]
However, after switching the switching valve, pilot pressure is generated in the pilot line, and it takes some time for the pilot pressure to act on the pilot chamber of the shock relief valve. In other words, there is a slight time difference from when the switching valve is switched to when the shock relief valve is switched. The fact that the timing of switching the shock mitigation valve is later than the timing of switching the switching valve in this way means that a part of the pump discharge oil is returned to the tank at the moment when the switching valve is switched. become. If a part of the pump discharge oil is returned to the tank when the switching valve is switched, no matter how suddenly the switching valve is switched, a large flow rate is not supplied to the actuator. Therefore, no shock or the like occurs in the actuator.
[0007]
According to a second aspect of the present invention, the shock mitigation valve has a valve body, a spool slidably provided on the valve body, a pilot chamber facing the end of the spool, and an introduction for introducing discharge oil from the pump. A port, a supply port that communicates with the most upstream switching valve, and a drain port that communicates with the tank. In the normal position, the introduction port, supply port, and drain port communicate with each other, and the pilot chamber has pilot pressure. It is characterized in that, when switched by operation, the introduction port and the supply port are communicated to block the drain port , and the shock is mitigated during the spool switching process .
The third invention is characterized in that a booster relief valve is used as a shock relief valve and the pilot pressure of the pilot line is guided to the pilot chamber of the booster relief valve.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 show a first embodiment, FIG. 1 is a circuit diagram for a power shovel, and FIG. 2 is a cross-sectional view of a shock relief valve.
The power shovel circuit shown in FIG. 1 includes a first pump P ₁ , a second pump P _2, and a third pump P ₃ . The first pump P ₁ is connected to a first circuit system consisting of switching valves 1 to 3, the second pump P ₂ is connected to a second circuit system consisting of switching valves 4 to 3, and the third pump P ₃ is connected to a third circuit system composed of switching valves 7-9.
[0009]
And the switching valves 1 to 3 and 4 to 6 of the first circuit system and the second circuit system open the neutral flow paths 10 and 11 when they are in the neutral position, but when they are open, The neutral flow paths 10 and 11 communicate with the tank T through the tank passage 12. Moreover, the neutral flow paths 10 and 11 are closed by switching one of the switching valves.
Further, in the first circuit system, the inflow ports 13 and 14 of the switching valves 2 and 3 have a path branched from the neutral flow path 10 with respect to the neutral flow path 10 on the downstream side of the most upstream switching valve 1. They are connected in parallel through. Therefore, when the most upstream switching valve 1 is switched , the neutral flow path 10 is closed, so that the inflow ports 13 and 14 of the switching valves 2 and 3 are also closed.
[0010]
In the second circuit system, the switching valves 4 to 6 are all connected in tandem via the neutral flow path 11. Therefore, if the upstream switching valve is switched, the oil discharged from the second pump P2 is not supplied to the downstream switching valve.
The switching valves 7 to 9 of the third circuit system are also connected in tandem via the neutral flow path 15. However, the neutral flow path 15 on the downstream side of the switching valve 9 located on the most downstream side of the third circuit system is connected to the switching valve 6 of the second circuit system and the downstream side of the switching valve 6 via the junction passage 16. The neutral channel 11 is communicated.
In the figure, reference numeral 17 is a check valve provided in the junction passage 16 and is configured to permit only the flow from the neutral flow path 15 of the third circuit system to the switching valve 6 of the second circuit system. Reference numeral 18 denotes a connection passage for communicating the neutral flow paths 11 and 15, and an orifice 19 is provided in the connection passage 18.
[0011]
A shock mitigation valve V is provided on the upstream side of the switching valves 1 and 4 located in the uppermost stream of the first and second circuit systems as described above.
The shock relief valve V is specifically shown in FIG. As apparent from FIG. 2, the shock relaxation valve V forms a first introduction port 20 and a second introduction port 21 in the valve body b, and a spool 22 is slidably incorporated therein. Then, connect the first inlet port 20 to the first pump P _1, it connects the second inlet port 21 to the second pump P _2.
The first and second introduction ports 20 and 21 configured as described above communicate with the supply ports 23 and 24 and the drain ports 25 and 26, respectively.
[0012]
The one supply port 23 is opened in the neutral flow path 10 of the first circuit system, and the other supply port 24 is opened in the neutral flow path 11 of the second circuit system. Further, the drain ports 25 and 26 communicate with the tank passage 12.
One end of the spool 22 faces the pilot chamber 27 and the spring force of the spring 28 is applied to the other end.
When the spool 22 is in the illustrated normal position, the introduction ports 23 and 24 communicate with each other via the annular grooves 22a and 22b formed in the spool 22, and the drain ports 25 and 26 are also formed in the spool 22. Are communicated with the tank passage 12 through the annular grooves 22c and 22d.
[0013]
Therefore, as long as the spool 22 is in the illustrated normal position, part of the discharged oil from the _first and second pumps P ₁ and P ₂ is returned to the tank T via the drain ports 25 and 26.
When the spool 22 is thus moved to the spring 28 by the action of the pilot pressure in the pilot chamber 27, the drain ports 25 and 26 are closed by the spool 22. However, the supply ports 23 and 24 and the neutral flow paths 10 and 11 remain in communication with each other. Therefore, in this case, the entire discharge amount of the _first and second pumps P ₁ and P ₂ is supplied to the neutral flow paths 10 and 11.
[0014]
In the figure, reference numeral 29 denotes a pilot port, which is connected to the pilot pump PP via a pilot line 30 in FIG. Further, a branch passage 31 is connected to the pilot line 30 and the branch passage 31 is connected in tandem to each switching valve of the first and second circuit systems. The most downstream side of the branch passage 31 communicates with the tank T.
Accordingly, no pilot pressure is generated in the pilot chamber 27 when all the switching valves 1 to 6 are in the neutral position. Therefore, the shock relief valve V maintains the normal position shown in FIG .
Further, when any one of the switching valves 1 to 6 is switched, the branch passage 31 is blocked and the communication between the pilot line 30 and the tank and T is also blocked, so that a pilot pressure is generated in the pilot chamber 27. Therefore, the spool 22 moves against the spring 28 by the action of the pilot pressure, and the shock relief valve V is switched.
[0015]
Next, the operation of the first embodiment will be described.
Now, assuming that the switching valves 1 to 6 of the first and second circuit systems are maintained at the neutral positions shown in the drawing, the total amount of oil discharged from the pilot pump PP is returned to the tank T via the branch passage 31. Accordingly, no pilot pressure is generated in the pilot chamber 27, and the shock relaxation valve V maintains the illustrated normal position.
From the above state, for example, assuming that rapidly switching the switching valve 2, first, the branch passage 31 at this switching valve 2 is closed.
If the branch passage 31 is closed in this manner, the communication between the pilot line 30 and the tank T is blocked, so that a pilot pressure is generated in the pilot chamber 27 and the shock relief valve V is switched.
[0016]
However, there is a slight timing shift after the switching valve 2 is switched as described above until the shock mitigation valve V is switched. In other words, after switching the switching valve 2, the timing is slightly delayed and the shock relief valve V is switched.
Therefore, at the moment when the switching valve 2 is switched, the drain ports 25 and 26 of the shock relief valve V are kept open. Then, in the process in which the spool 22 moves against the spring 28, the drain ports 25 and 26 are gradually closed. Therefore, at the initial stage when the switching valve 2 is switched, a part of the discharge amount of the first pump P ₁ is returned to the tank T, and accordingly, the supply flow rate to the actuator connected to the switching valve 2 is also increased. Less. If the supply flow rate decreases in this way, the shock is alleviated accordingly.
[0017]
Further, in the first embodiment, since the shock relief valve V is provided at the most upstream of the first and second circuit systems, it is not particularly necessary to provide the shock relief valve V for each switching valve, and the circuit as much as that. The configuration is simplified.
Furthermore, the shock mitigation valve V of the first embodiment can alleviate shocks of both the first and second circuit systems with a single spool, and therefore is configured in comparison with the case where the shock mitigation valve V is provided for each circuit system. Becomes easier.
[0018]
The second embodiment shown in FIG. 3 uses the _first and second boosting relief valves V ₁ and V ₂ as the shock relief valve V, and the others are the same as the first embodiment. That is, the pilot line 30 is connected to the pilot chambers 32 and 33 of the boost relief valves V ₁ and V ₂ .
In the case of the second embodiment, by switching any of the switching valves, the set pressures of the _first and second boosting relief valves V ₁ and V ₂ are increased. This is based on the fact that it is delayed from the timing at the time of switching.
[0019]
【The invention's effect】
According to the shock mitigation device of the present invention, even when the switching valve is suddenly switched, no shock is generated when the actuator is started.
In addition, since the shock relief valve is provided in the uppermost stream of the hydraulic circuit, the configuration is simplified as compared with the case where the shock relief valve is provided for each switching valve.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a first embodiment.
FIG. 2 is a cross-sectional view of the shock relief valve of the first embodiment.
FIG. 3 is a circuit diagram of a second embodiment.
[Explanation of symbols]
P ₁ , P ₂ pumps 1 to 6 Switching valve V Shock relief valve b Valve body 20, 21 Introduction port 22 Spool 23, 24 Supply port 25, 26 Drain port 27 Pilot chamber 30 Pilot line V ₁ , V ₂ Shock relief valve Boost relief valve 32, 33 Pilot chamber

Claims (3)

A plurality of actuators are driven by at least one pump, and a switching valve is connected to each of the actuators. In the hydraulic circuit that controls the operation of the actuator by switching these switching valves, the most upstream position among the switching valves. When a shock relief valve is connected to the upstream side of the switching valve at the same time , a part of the pump discharge oil is returned to the tank in its normal state, and the pilot pressure is applied to the pilot chamber of the shock relief valve A pilot line for guiding the pilot pressure to the pilot chamber of the shock mitigation valve is provided to prevent the return of the discharged oil to the tank, and the pilot line is provided when each switching valve is in the neutral position. It was connected to the branch passage communicating with, cut conversion either the switching valve from the neutral position And time, are prevented from communicating with the said branch passage and the tank, the shock absorbing device of a hydraulic circuit which pilot pressure is in the configuration that occurs pilot line. The shock relief valve includes a valve body, a spool slidably provided on the valve body, a pilot chamber facing the end of the spool, an introduction port for introducing oil discharged from the pump, It has a supply port that communicates with the switching valve and a drain port that communicates with the tank. In the normal position, the introduction port, supply port, and drain port communicate with each other, and the pilot chamber is switched by the pilot pressure. 2. The shock mitigation device for a hydraulic circuit according to claim 1, wherein the introduction port and the supply port are communicated to block the drain port , and the shock is mitigated in the spool switching process . 2. The shock relief device for a hydraulic circuit according to claim 1, wherein a pressure relief valve is used as the shock relief valve, and the pilot pressure of the pilot line is guided to a pilot chamber of the pressure relief valve.

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