JP2556999B2 - Hydraulic circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention may be one hydraulic pump or a plurality of hydraulic pumps.
The present invention relates to a hydraulic circuit in which a discharge circuit of a pump is connected to an upstream side of an operation valve to supply discharge hydraulic fluid of a hydraulic pump, which can be regarded as substantially one, to a plurality of hydraulic actuators.

[Conventional technology]

One hydraulic pump or a plurality of hydraulic pumps has a discharge circuit connected to the upstream side of the operating valve and can be regarded as substantially one. It is sufficient to supply multiple pressure valves to each hydraulic actuator by providing multiple operation valves on the discharge passage of the switch and switching the operation valves. The pressure oil is supplied only to the hydraulic actuator having a small load, and the pressure oil is not supplied to the hydraulic actuator having a large load.

Therefore, in the hydraulic circuit of a hydraulic excavator having a plurality of hydraulic actuators, in the above-mentioned case, the operator reduces the operation amount of the operation valve on the side of the hydraulic actuator with a small load to reduce the opening area, making it difficult for pressure oil to flow. By doing so, it is possible to supply pressure oil to a hydraulic actuator having a large load, and to simultaneously drive a plurality of hydraulic actuators having different loads. In other words, the operator always balances the load,
The complicated operation of driving a plurality of hydraulic actuators at the same time by changing the operation amount of a plurality of operating valves has been performed.

A hydraulic circuit that solves this problem is disclosed in
The one shown in Japanese Patent Laid-Open No. 59-197603 has been proposed.

A schematic view of such a hydraulic circuit is shown in FIG.

That is, a plurality of operating valves 2 are provided in the discharge passage 1a of the hydraulic pump 1, a pressure compensating valve 5 is provided in each circuit 4 that connects each operating valve 2 and each hydraulic actuator 3, and the pressure of each circuit 4, that is, the load. The highest pressure among the pressures is detected by the shuttle valve 6, and the detected load pressure is detected by each pressure compensation valve 5.
Of the operating valve 2 and the second pressure-receiving portion 5b of the pressure compensating valve 5 to set the pressure corresponding to the load pressure. Here, the setting means that the opening area of the pressure compensating valve connected to another hydraulic actuator is made smaller with the highest load pressure among the plurality of hydraulic actuators, and its upstream pressure (that is, the outlet pressure of the operating valve 2). Is to be the same as the highest load pressure.

By doing so, the outlet side pressure (downstream pressure) of each operating valve 2 becomes the same pressure as the highest load pressure when the operating valve 2 is operated at the same time by making the outlet side pressures of the operating valves 2 equal, The pressure on the inlet side of the operating valve 2 is the same as that of the common hydraulic pump 1.
Since the pump pressure is equal to each other, the differential pressure across the opening area of each operation valve 2 becomes equal, so that the pressure oil can be supplied to each hydraulic actuator 3 at a diversion ratio proportional to the opening area of each operation valve.

[Problems to be Solved by the Invention]

The conventional technique shown in FIG. 2 is a hydraulic circuit having a plurality of hydraulic actuators 3.
The purpose of the present invention is to supply pressure oil proportional to the operation amount of the operation valve 2 to a plurality of hydraulic actuators 3, regardless of the magnitude of the load acting on the. However, there are the following problems.

In FIG. 2, the hydraulic actuator (cylinder) 3 is shown on the right side on the high load side, and the hydraulic actuator (motor) on the left side is shown.
Assuming that 3 is on the low load side, the load pressure of the right hydraulic actuator 3 is selected by the shuttle valve 6 and introduced into the control device of the hydraulic pump 1, and at the same time, the pressure compensation valve (right side) 5 and low load It acts on the side pressure compensation valve (left side) 5.

The pressure compensating valve 5 (right side) of the pressure compensating valve 5 has its own load pressure P ₃ and a weak spring force (without indicating the number) acting on the side where the opening of the pressure compensating valve 5 is narrowed, and pressure is applied to the side where the opening is opened. The inlet side pressure P ₂ of the compensating valve 5 acts. Since there is some passage resistance in the pressure compensation valve 5, the inlet side pressure P ₂ and the outlet side pressure (load pressure) P ₃
Since the relation of P ₂ > P ₃ , the pressure compensating valve 5 of its own is (force in the opening direction by P ₂ ) = (force in the closing / opening direction by P ₃ ) + (weak spring force) + (flow force) It becomes a balanced state, and the flow rate is almost full
Supply Q1 pressure oil to the right hydraulic actuator 3 (cylinder).

On the other hand, in the pressure compensation valve 5 on the low load side, the load pressure P ₃ on the high load side acts on the side that throttles the opening, so the opening of the pressure compensation valve 5 is throttled, and the inlet side pressure P ₂ is consequently It boosted to a pressure of P _3. (More accurately, the spring force of the weak spring is also added.) In other words, the flow rate Q ₁ of the pressure oil on the high load side is (C is a constant, a ₁ is the opening area of the operation valve 2, P ₁ is the discharge pressure of the hydraulic pump 1) The flow rate Q ₂ of the pressure oil on the low load side is (C is a constant, a ₂ is the opening area of the operation valve 2, P ₁ is the discharge pressure of the hydraulic pump 1), and even if the opening area is a ₁ = a ₂ , the supply flow rate to each hydraulic actuator 3 is Q ₁ = It doesn't become Q ₂ .

That is, if the outlet pressure of the operation valve 2 on the low load side (the inlet side pressure of the pressure compensation valve 5) P ₂ is the same as the outlet pressure of the operation valve 2 on the high load side (the inlet side pressure of the pressure compensation valve 5) P _2. No pressure, lower than that, the outlet side pressure (load pressure) P ₃ of the pressure compensating valve 5 on the high load side.
Therefore, even if the opening area of the operation valve 2 is the same, the flow rate supplied to the hydraulic actuator 3 on the low load side becomes larger.

In order to solve this problem, load pressure is applied not to the circuit 4 on the outlet side of the pressure compensation valve 5 but to the inlet side of the pressure compensation valve 5 (P ₂ part).
There is also a plan to detect it with this method, but if this is done, the pressure compensating valve 5 on its own (high pressure side) will have pressure on the inlet side in the direction of opening the opening.
Since P ₂ acts on the inlet side pressure P _{2 in the} closing direction again,
The pressure compensation valve 5 of its own cannot be opened.

Alternatively, the pressure detected as the load pressure is detected closer to the pressure compensating valve 5 than the position where the inlet pressure P ₂ is detected between the operation valve 2 and the pressure compensating valve 5 (that is, the load pressure P ₃ is the inlet pressure P _2). detected) as a slightly lower pressure P _'2 from P _2, even 5 themselves of the pressure compensating valves so as to open, to act the flow force due to the passage of the pressure oil in the pressure compensating valve 5, itself The pressure compensating valve 5 is moved to a position where the opening is further narrowed, and as a result, P ₂ and P ′ ₂ are further raised.

Then, the pressure difference between P ₂ and P ′ ₂ and the load pressure P ₃ increases, and the flow force increases in accordance with the pressure difference, so the pressure compensating valve 5 is further throttled and P ₂ and P ′ ₂ further rise. As a result, the pressure compensating valve 5 on the high pressure side, which should have been in a state close to full open by a slight passage resistance, is throttled, causing a large pressure difference and causing a power loss. Cannot be adopted.

Therefore, an object of the present invention is to provide a hydraulic circuit capable of solving the above-mentioned problems.

[Means and Actions for Solving the Problems]

The present invention provides a plurality of operation valves 1 in the discharge passage 10a of the hydraulic pump 10.
5, the pressure compensating valve 18 is provided in the connection circuit of each operation valve 15 and each hydraulic actuator 16, and each pressure compensating valve 18 is pushed by the pressure oil of the first pressure receiving portion 19 in the large opening area direction, and the second pressure receiving It is assumed that the pressure oil of the portion 20 pushes the opening area in a small direction, and the inlet side and the outlet side of each of the pressure compensating valves 18 are connected by a first load pressure introducing passage 29, and each of the first load pressure introducing passages 29 is connected. Check valves 28 for blocking the flow of pressure oil from the inlet side to the outlet side are respectively provided near the inlet side of the first throttle valve 26 of the first throttle valve 26 in the first load pressure introduction path 29 closer to the inlet side than the check valve 28. Two throttles 27 are provided respectively, and the first load pressure introducing path 29 is connected between the first throttle 26 and the second throttle 27 on the inlet side of the second shuttle valve 22, and the second shaft valve thereof is connected.
The circuit 32 is connected to the outlet side of 22, and the actuator holding introduction path 33 is connected to the outlet side of each of the pressure compensation valves 18,
The respective actuator holding and introducing passages 33 and the circuit 32 are respectively connected to the inlet sides of the respective first shuttle valves 21, and the outlet sides of the respective first shuttle valves 21 are connected to the second side of the respective pressure compensation valves 18.
The hydraulic circuit is characterized in that it is connected to the pressure receiving portion 20 and the first pressure receiving portion 19 of each pressure compensation valve 18 is connected to the output side of each operation valve 15.

In the hydraulic circuit of the present invention, since the intermediate pressure between the inlet side pressure and the outlet side pressure of the pressure compensation valve 18 is detected as the load pressure, the first pressure receiving portion of the low load side pressure compensation valve 18 is detected.
The pressure difference between the pressure of 19 and the pressure of the second pressure receiving portion 20 becomes small, and the difference between the flow rate of the hydraulic actuator 16 on the low load side and the flow rate of the hydraulic actuator 16 on the high load side becomes small, and the pressure on the high load side becomes small. The pressure of the first pressure receiving portion 19 of the compensating valve 18 is always higher than the pressure of the second pressure receiving portion, and the pressure compensating valve 18 opens in a state of being almost fully opened.

Further, the actuator holding pressure of the hydraulic actuator 16 and the load pressure are compared by the first shuttle valve 21, and the higher pressure is supplied to the second pressure receiving portion 20 of the pressure compensating valve 18, so that the operation valve 15 is set to the neutral position. Since the actuator holding pressure is supplied to the second pressure receiving portion 20 of the pressure compensating valve 18, the opening area of the pressure compensating valve 18 is small when the operating valve 15 is operated to supply pressure oil to the hydraulic actuator 16. Hydraulic pumps 10
The pressure rises quickly.

〔Example〕

As shown in FIG. 1, the hydraulic pump 10 is a variable displacement type hydraulic pump in which the displacement, that is, the discharge flow rate per rotation is changed by changing the angle of the swash plate 11. The swash plate 11 has a large-diameter piston 12 Tilts in the capacity decreasing direction, and tilts in the capacity increasing direction with the small diameter piston 13.

The pressure receiving chamber 12a of the large-diameter piston 12 is connected to and cut off from the discharge passage 10a of the hydraulic pump 10 by the switching valve 14, and the small-diameter piston 13
The pressure receiving chamber 13a is connected to the discharge passage 10a.

A plurality of operating valves 15 are provided in the discharge passage 10a of the hydraulic pump 10, and a pressure compensating valve 18 is provided in a circuit 17 connecting each operating valve 15 and the hydraulic actuator 16, and the pressure compensating valve 18 is The pressure oil of the first pressure receiving valve 19 pushes the opening area in a larger direction and the pressure oil of the second pressure receiving portion 20 pushes the opening area in a smaller direction. The inlet pressure is supplied to the second pressure receiving portion 20, and the second pressure receiving portion 20 is connected to the respective load pressure introducing passages 23 via the first and second shuttle valves 21 and 22 and has the highest load pressure or the actuator described later. The holding pressure introduction passage 33 supplies the actuator holding pressure.

The switching valve 14 is pushed in the communicating direction by the pressure in the discharge passage 10a, and is pushed in the drain direction by the spring 24 and the load pressure, and the differential pressure between the discharge pressure P ₁ and the load pressure PLS (P ₁ -P _LS ). Becomes larger than the spring force set by the spring 22, the switching valve 14 switches to the communicating position, supplies the discharge pressure to the pressure receiving chamber 12a of the large-diameter piston 12, tilts the swash plate 11 in the capacity decreasing direction, and P ₁ and load pressure
When the differential pressure of PLS (P ₁ -P _LS ) becomes smaller than the spring force set by the spring 22, the switching valve 14 switches to the drain position and flows out from the pressure receiving chamber 12a of the large diameter piston 12 to the tank side and the swash plate. Tilt 11 in the capacity increasing direction.

The operation valve 15 is operated in a direction in which the opening area increases in proportion to the pilot pressure oil from the pilot control valve 25, and the pilot pressure oil is proportional to the operation stroke of the lever 25a.

The load pressure introducing passage 23 connects the inlet side and the outlet side of the pressure compensating valve 18, and has a first load pressure introducing passage 29 having first and second throttles 26, 27 and a check valve 28, and the first load. Pressure introduction path 29
The second load pressure introducing passage 30 communicating between the first throttle 26 and the second throttle 27 in the load pressure port 15a of the operation valve 15, the load pressure port 15a of the operation valve 15 and the second shuttle valve 22. The third load pressure introducing passage 31 is connected, the outlet side of the second shuttle valve 22 is connected to one inlet side of the first shuttle valve 21 in the circuit 32, and the other inlet side is an actuator holding pressure introducing passage.
33 is connected to the outlet side of the pressure compensating valve 18, and the outlet side of the first shuttle valve 21 is connected to the second pressure receiving portion 20.

The load pressure port 15a of the operation valve 15 communicates with the tank at the neutral position N, and is disconnected from the tank at the first and second pressure oil supply positions I and II, and the second load pressure introducing passage 30 and the third load Pressure introduction path
Connect 31.

 Next, the operation will be described.

An example will be described in which the plurality of operation valves 15 are switched to the first pressure oil supply position I to supply the pressure oil to the plurality of hydraulic actuators 16.

The load pressure port 15a of the operating valve 15 shuts off from the tank
Since the load pressure introducing passage 30 and the third load pressure introducing passage 31 are communicated with each other,
The intermediate pressure between the inlet side pressure and the outlet side pressure of the pressure compensating valve 18 flows into the inlet side of the second shuttle valve 22 as the load pressure P _LS , and the load pressures of the plurality of hydraulic actuators 16 are compared to determine the maximum load pressure. Is output to the circuit 32, and the maximum load pressure is supplied from the first shuttle valve 21 to the second pressure receiving portion 20 of each pressure compensation valve 18.

Therefore, assuming that the right hydraulic actuator (cylinder) 16 is on the high load side and the left hydraulic actuator (motor) 16 is on the low load side, the inlet pressure P ₂ and the outlet of the right pressure compensating valve 18 are An intermediate pressure P ₄ of the side pressure P ₃ is detected as a load pressure, and this intermediate pressure P ₄ is applied to the left and right pressure compensation valves 18
To the second pressure receiving portion 20 of each.

For this reason, the flow rate Q ₁ of the pressure oil on the high load side (right side) is (C is a constant number, a ₁ is the opening area of the operation valve 2, P ₁ is the discharge pressure of the hydraulic pump 1) The flow rate Q ₂ of the pressure oil on the low load side (left side) is (C is a constant, a ₂ is an opening area of the operation valve 2, and P ₁ is a discharge pressure of the hydraulic pump 1).

Here, since the intermediate pressure P ₄ is lower than the inlet pressure P _{2 and} higher than the outlet pressure P ₃ , (P ₁ −P ₄ ) becomes smaller than (P ₁ −P ₃ ), and the low load side Since the flow rate Q ₂ is smaller than before, the difference between the flow rate Q ₁ on the high load side and the flow rate Q ₂ on the low load side becomes smaller than before when the opening areas of the left and right operation valves 2 are the same.

In addition, the inlet pressure P ₂ acts on the first pressure receiving portion 19 of the pressure compensation valve 18 on the high load side, and the intermediate pressure P ₄ acts on the second pressure receiving portion 20, so that P ₂ > P ₄ . Therefore, the pressure compensation valve 5 can be opened.

Further, when the pressure compensation valve 5 on the high load side moves to a position where the opening is throttled by the flow force, the inlet side pressure P ₂ becomes slightly higher, but the outlet side pressure P ₃ is constant, so the intermediate pressure P 2 ₄ is slightly higher, and the pressure compensating valve 5 on the high load side is in a state of being almost fully opened, so that power loss does not occur.

When each operating valve 15 is in the neutral position N and the hydraulic actuator 16 has a holding pressure.

Although the load port 15a of the operation valve 15 communicates with the tank, the holding pressure of the hydraulic actuator 16 is generated on the upstream side of the check valve 28 in the first load pressure introducing path 29, and the holding pressure of the hydraulic actuator 16 is held by the actuator. Pressure introduction path 33
From the first shuttle valve 21, and the load pressure introduction path at this time
Since the load pressure of 23 is zero, the actuator holding pressure is supplied to the second pressure receiving portion 20 of the pressure compensating valve 18, and the opening area of the pressure compensating valve 18 is small.

Because of this, when the operating valve 2 is operated to supply pressure oil to the hydraulic actuator 16, the pressure compensating valve 18
Has a small opening area, and the pressure of the hydraulic pump 10 rises quickly, resulting in excellent responsiveness.

〔The invention's effect〕

An intermediate pressure between the inlet side pressure and the outlet side pressure of the pressure compensating valve 18 is detected as the load pressure of the hydraulic actuator 16, and the highest load pressure of each hydraulic actuator is supplied to the second pressure receiving portion 20 of each pressure compensating valve 18. So multiple hydraulic actuators
When 16 are operated simultaneously, the differential pressure between the inlet side pressure of the low load side pressure compensating valve 18 and the discharge pressure of the hydraulic pump becomes small, and the pressure of the first pressure receiving portion 19 of the high load side pressure compensating valve 18 becomes It is always higher than the pressure of the second pressure receiving portion 20.

Therefore, when a plurality of hydraulic actuators are operated simultaneously, the difference between the flow rate of the hydraulic actuator on the high load side and the flow rate of the hydraulic actuator on the low load side becomes small, and the pressure compensation valve 18 on the high load pressure side becomes almost full open. There is no power loss due to valve opening.

Further, the actuator holding pressure of the hydraulic actuator 16 and the load pressure are compared by the first shuttle valve 21, and the higher pressure is supplied to the second pressure receiving portion 20 of the pressure compensating valve 18, so that the operation valve 15 is set to the neutral position. The second pressure receiving portion 20 of the pressure compensating valve 18
Since the actuator holding pressure is supplied to the hydraulic pump, the opening area of the pressure compensating valve 18 is small when the operating valve 15 is operated to supply pressure oil to the hydraulic actuator 16.
The pressure of 10 rises quickly and the responsiveness is improved.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, and FIG. 2 is a hydraulic circuit diagram of a conventional example. Reference numeral 10 is a hydraulic pump, 10a is a discharge passage, 15 is an operation valve, 16 is a hydraulic actuator, 17 is a circuit, 18 is a pressure compensating valve, 19 and 20 are first and second pressure receiving portions, and 21 and 23 are first and second. 2 shuttle valves, 23
Is a load pressure introducing path, 26 and 27 are first and second throttles, 28 is a check valve, 29 is a first load pressure introducing path, 30 is a second load pressure introducing path,
Reference numeral 31 is a third load pressure introducing passage, 32 is a circuit, and 33 is an actuator holding pressure introducing passage.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Yamashita 3-20-1 Nakase, Kawasaki-ku, Kawasaki-shi, Kanagawa Komatsu Ltd. Kawasaki Plant (72) Inventor Shinichi Shinozaki Nakase-ku, Kawasaki-ku, Kanagawa 3-20 ―1 Komatsu Ltd. Kawasaki Plant (56) References JP 59-197603 (JP, A) JP 63-9703 (JP, A)

Claims (1)

(57) [Claims] 1. A plurality of operating valves 1 in a discharge passage 10a of a hydraulic pump 10.
5, the pressure compensating valve 18 is provided in the connection circuit of each operation valve 15 and each hydraulic actuator 16, and each pressure compensating valve 18 is pushed in the large opening area direction by the pressure oil of the first pressure receiving portion 19, It is assumed that the pressure oil of the pressure receiving portion 20 is pushed in the direction of the small opening area, and the inlet side and the outlet side of each of the pressure compensating valves 18 are connected by the first load pressure introducing passages 29, respectively. Check valves 28 for blocking the flow of pressure oil from the inlet side to the outlet side are provided near the inlet side at 29, and the first throttle 26 is provided closer to the inlet side than the check valve 28 at each of the first load pressure introducing paths 29. And a second throttle 27 are respectively provided, and the first load pressure introducing passage 29 is connected between the first throttle 26 and the second throttle 27 on the inlet side of the second shuttle valve 22.
A circuit 32 is connected to the outlet side of 22 and an actuator holding pressure introducing passage 33 is connected to the outlet side of each pressure compensating valve 18, and each actuator holding pressure introducing passage 33 and the circuit 32 are connected.
Are connected to the inlet side of each first shuttle valve 21, and the outlet side of each first shuttle valve 21 is connected to each pressure compensation valve 18
And a first pressure receiving portion 19 of each pressure compensating valve 18 is connected to an output side of each operation valve 15, respectively.