JPS58117140A - Oil-pressure circuit - Google Patents

Abstract

PURPOSE:To eliminate the need for surge pressure absorptive valve by reducing the amount of discharge of a variable capacity type pump by a method in which the pressure difference before and after the throttling of a throttle switching valve provided in a pump line is controlled constantly and the spring chamber of a discharge amount control valve is led to a tank during the neutral period. CONSTITUTION:When positioning a throttle switching valve 3 to the position S1, the spring chamber 26 and pilot chamber 24 of a discharge amount control valve 22 are equalized with a pump line 2 in terms of pressure, and the chamber 21a is led to a tank 23 and a maximum flow of oil is discharged by a skew plate control cylinder 21. Also, the pressure difference before and after the throttling of the switching valve 3 is controlled constantly by a bypass-shaped pressure compensatory valve 13 and excessive fluid is discharged to the tank 11. Thus, the compensatory valve 13 can serve as a surge pressure absorptive valve. The same is true in the case where the switching valve 3 is positioned at the position S2. When it is positioned at the position S0, a small flow rate of unload operation is made possible by controlling the discharge flow rate of the variable capacity-type pump 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an energy-saving hydraulic circuit using a variable displacement pump.

Conventionally, this type of energy-saving hydraulic circuit uses a variable displacement pump (hereinafter referred to as a variable pump). ] The pressures before and after the throttle switching valve provided in the pump line of the variable pump are transmitted to the pilot chamber and spring chamber of the discharge rate control valve that controls the fluid acting on the discharge rate control section of the variable pump, respectively, to control the discharge rate. The control valve is operated to control the discharge flow rate of the variable pump according to demand so that the differential pressure before and after the throttle switching valve is constant regardless of its opening degree, so as not to discharge wasteful flow. It is known that the surge pressure generated by the poor response of the variable pump is absorbed by a surge absorption valve consisting of a two-port valve, in order to achieve an energy-saving effect. -54301)
.

However, the conventional energy-saving hydraulic circuit described above inevitably requires a surge absorption valve in order to absorb the surge pressure that tends to occur due to the use of a discharge rate control valve and a variable pump with poor response. The disadvantage is that the configuration is complicated and expensive.

Therefore, an object of the present invention is to provide an energy-saving hydraulic system that can omit the surge pressure absorption valve and also prevent the variable pump from discharging wasteful fluid using a method different from the conventional example described above, thereby reducing power loss. The purpose is to provide circuits.

For this reason, this invention provides a pump line for a variable pump.
A throttle switching valve is provided which is closed in the switching position and opened in the neutral position and has a pilot passage leading to the tank, and a bypass type pressure compensating valve is connected between the pump line and the tank to close the throttle valve. The pump line is connected to a pilot chamber of a discharge amount control valve that controls the differential pressure before and after the throttle in the switching valve to be constant, and selectively connects the discharge amount control section of the variable pump to the pump line and the tank, By connecting a pump line to the spring chamber of the discharge amount control valve via a throttle, and connecting the spring chamber to the pilot passage of the switching valve via a pilot line, the bypass type pressure compensation valve can be used as a surge absorption valve. In addition, when the throttle switching valve is in the neutral state, the spring chamber of the discharge amount control valve is communicated with the tank via the pilot passage, so that the surge absorption valve can be omitted. The invention is characterized in that the discharge flow rate of the variable pump is controlled to a very small amount by the operation of the variable pump, so that there is no power loss when the variable pump is in the neutral position.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

In FIG. 1, 1 is, for example, a variable pump consisting of a swash plate type variable displacement piston pump whose swash plate is always biased in the direction of maximum inclination to discharge the maximum flow rate, and 2 is connected to the discharge port of variable pump 1. 3 is a closed center type throttle switching valve installed in the pump line 2; 4 is a hydraulic cylinder whose operating direction and speed are controlled by the throttle switching valve 3;

The throttle switching valve 3 has the functions of a throttle valve and a directional switching valve, and furthermore, in the neutral position, it communicates with the tank 5, and in the switching position, it communicates with the throttle valve 3 downstream (downstream) of the throttle (not shown). In addition to the feedback passage 7 which communicates with the tank 5 (side) and detects the load pressure, there is also a pilot passage 8 which is open in the neutral position and communicates with the tank 5, and which is closed in the switching position.

Also, the pump line 2 upstream of the throttle switching valve 3
From there, a bypass line 12 leading to the tank 11 is branched, and a bypass type pressure compensation valve 1 is connected to the bypass line 12.
3 and a spring chamber 14 of the pressure compensation valve 13.
The pilot line 15 is pulled to connect the throttle switching valve 3 to the fi τ
It is connected to the load pressure detection bong (7a) on the primary side of the double check passage 7. Therefore, when the throttle switching valve 3 is being switched, the bypass type pressure compensation valve 13 is operated in its spring chamber 14.
The differential pressure before and after the throttle of the throttle switching valve 3 is controlled to a constant value corresponding to the spring pressure of the spring 16, and the excess fluid is discharged to the tank 11.

Further, the chamber 21a on the opposite side of the swash plate control cylinder 21 as a discharge amount control section of the variable pump l is connected to the pump line 2 and the tank via a 3-port throttle switching valve 22 as an example of a discharge amount control valve. 23 and can be switched and connected. In the pilot chamber 24 of the discharge amount control valve 22,
The pump line 2 is connected via a pilot line 25, and the spring chamber 26 of the discharge amount control valve 22 is connected to the pump line 2 via a pilot line 28 with a throttle 27 interposed in the middle. 29 to the primary port of the pilot passage 8 of the throttle switching valve 3) 8H
is connected to. The spring pressure of the spring 30 in the spring chamber 26 of the discharge amount control valve 22 is set smaller than the spring pressure of the spring 16 in the spring chamber 14 of the bypass type pressure compensation valve 13.

Further, the spring chamber 26 of the discharge amount control valve 23 is connected to a tank 35 via a pilot line 34 having a pilot relief valve 33 interposed therebetween.

In the energy-saving hydraulic circuit configured as described above, the throttle switching valve 3 is now located at the switching position S□, and the hydraulic cylinder 4
It is assumed that the piston rod 4a of is operated to protrude.

At this time, the spring chamber 26 of the discharge amount control valve 22 communicates with the pump line 2 via the throttle 27 and the pilot line 28, and the pilot passage 8 of the throttle switching valve 3 is closed. The pressure in the spring chamber 26 is the same as the pressure in the pump line 2, and the pressure in the discharge rate control valve 2 is the same as that in the pump line 2.
Since the pilot chamber 24 of No. 2 also communicates with the pump line 2 via the pilot line 25, the pump line 2
The pressure is the same as that of Therefore, the discharge amount control valve 22 is located at the symbol position V1 due to the spring force of the spring 30, and the chamber 21a on the opposite side of the swash plate control cylinder 21 communicates with the tank 23 via the discharge amount control valve 22, and The plate control cylinder 21 inclines the swash plate to the maximum inclination side to discharge the maximum flow rate.

On the other hand, at the switching position S□ of the throttle switching valve 3, the feedback passage 7 communicates with the rear of the throttle of the throttle switching valve 3, so the spring chamber of the bypass type pressure compensation valve 13 is connected to the spring chamber via the pilot line 15. The bypass type pressure compensating valve 13 controls the differential pressure before and after the throttle to be constant, and discharges excess fluid to the tank 11.

In this way, at the switching position S□ of the throttle switching valve 3 (the same applies to the case of 52), the pressure of the throttle of the throttle switching valve 3 is compensated by the valve control method using the bypass type pressure compensation valve 13. Fast response and bypass type pressure compensation valve 1
Since excess fluid is discharged to the tank 11 through the pump 3, the bypass type pressure compensating valve 13 can function as a surge absorbing valve to absorb surge pressure.

Next, assume that the piston rod 4a of the hydraulic cylinder 4 reaches the end of its stroke and stops.

Then, the pressure in the pump line 2 increases, and the pilot relief valve 33 to which the pressure is guided operates, enters a relief state, and controls the pressure in the spring chamber 26 of the discharge amount control valve 22 to the set pressure.

In this case, the discharge amount control valve 22 is operated in its pilot chamber 24.
The variable pump 1 is located at the symbol position Vl or the symbol position ■2 so that the differential pressure between the pump and the spring chamber 26 becomes the spring pressure of the spring 30. control the discharge flow rate. At this point, the pressure of the fluid discharged from the variable pump 1 is high and corresponds to the set pressure of the pilot relief valve 33, but the discharge flow rate is controlled by the differential pressure before and after the small throttle 27 of the pilot line 28. Since the amount is sufficient to correspond to the spring pressure of the spring 30 of the valve 27, the amount is extremely small, resulting in less power loss and an energy saving effect.

Note that in the relief state where the hydraulic cylinder 4 is stopped, no fluid flows through the throttle switching valve 3, so the pilot chamber 38 of the bypass type pressure compensation valve 13 and the spring chamber 1
6 is the same pressure, and the bypass type pressure compensation valve 1
3 is stopped in a closed state by the spring force of the spring 16.

Next, the throttle switching valve 3 is set to the neutral position S. Suppose that it is located at .

Then, the pilot passage 8 of the throttle switching valve 3 is opened and communicated with the tank 5, and the spring chamber 26 of the discharge rate control valve B communicates with the tank 5 via the pilot line 29 and the pilot passage 8, so that the discharge rate can be controlled. The valve 22 is located at the symbol position Vl or v2 so that the differential pressure between the pilot chamber 24 and the spring chamber 26 becomes the spring pressure of the spring 30, that is, the pressure of the pump line 2 becomes the spring pressure of the spring 3o. ,
On a regular basis, it is located between them to control the discharge flow rate of the variable pump l. At this time, the discharge flow rate of the variable pump 1 is extremely small because the pressure difference before and after the small throttle 27 of the pilot line 28 becomes the spring pressure of the spring 3o. Since the discharge pressure is extremely low, corresponding to the spring pressure of the spring 3o, power loss is reduced. That is, by communicating the spring chamber 26 of the discharge amount control valve 22 with the tank 5, the reversible pump l
Therefore, the unload operation is performed with a small discharge pressure and discharge flow rate. Also, at this time, since the pilot line 29 is filled with fluid flowing, the pressure in the spring chamber 26 is quickly reduced by switching the throttle switching valve 3 and operating the discharge amount control valve 22. It can be increased to make its responsiveness faster.

Also, at this point, the spring chamber 1 of the bypass type pressure compensation valve 13
4 is a pilot line 15 and a feedback passage 7
However, since the spring pressure of the spring 16 of the spring chamber 14 is greater than the spring pressure of the spring 30 of the discharge amount control valve 22, the bypass type pressure compensation valve 13 remains closed. It is.

FIG. 2 shows a modification in which the present invention is used as a hydraulic circuit for a hydraulic excavator. Parts having the same functions as those in the first figure are given the same reference numerals, and the explanation thereof will be omitted, and only the different parts will be explained.

In FIG. 2, 50 is a pilot valve for constant horsepower control, and signals from the swash plate indicating the discharge amount of the variable pump 1 and pressure signals of the pump line 2 are transmitted via a signal transmission means 51 such as a link mechanism. The discharge amount control unit 21 is controlled by being located at the symbol position M0 or M2 so that the horsepower obtained by multiplying the discharge pressure and the discharge flow rate of the variable pump 1 is constant. If the discharge flow rate is excessive, the line 52 is located at the symbol position M2 regardless of the operating state of the discharge amount control section 22.
The fluid is supplied to the discharge amount control unit 21 through the valve to reduce the discharge amount of the variable pump 1, and when the discharge amount is too small relative to the discharge pressure, the pilot valve 22 is moved to the symbol position M.
1, but in this case there is a check valve 5 in line 52.
4, the discharge amount control valve 21 is controlled depending on the symbol position of the discharge amount control valve 22.

In addition, 13a is a primary port 56 and a normally open decompression port 57.
A priority type pressure compensation valve having a normally closed bypass port 58 and also functioning as a bypass type pressure compensation valve,
The opening degree between the primary port 56 and the pressure reduction port 57 is controlled to preferentially compensate the pressure of the priority line 59 on the pressure reduction port 57 side, while draining excess fluid from the bypass port 58.

Further, 61 is a throttle switching valve 3a connected to the priority line 59.
・Select the maximum load pressure of 3b and set the priority type pressure compensation valve 56.
62 is the throttle switching valve 3, 3.
This is a shuttle valve that selects the maximum load pressure of and transmits it to the spring chamber of the bypass type pressure compensation valve 13.

In addition, the pilot passages 8.8.8.8 of the above-mentioned calibration switching valves 3.3.31 and 3a are connected in series to the pilot line 29, so that all the throttle switching valves 3.3.3a and 3a are in the neutral state. The spring chamber of the discharge amount control valve 22 is communicated with the tank 5 only when the variable pump 1 is in the position, so that the variable pump 1 is operated in an unloaded state.

Also, 65.65 is a hydraulic motor for driving a hydraulic excavator,
66 is a swing hydraulic motor, 67 is an arm hydraulic cylinder, 68 is a boom hydraulic cylinder, and 69 is a packet hydraulic cylinder.

Note that in FIG. 2, the circuit configuration on the left half is substantially the same as the circuit configuration on the right half, so a description thereof will be omitted.

Although the throttle valves 3.3.3a and 3a are used in each of the above embodiments, the throttle valve and the switch valve may be provided separately.

In addition, the pilot relief valve 33 is replaced with the priority type pressure compensation valve 1.
It may be connected to the spring chamber 3a.

As is clear from the above description, the present invention provides, in the pump line of a variable pump, a throttle switching valve having a pilot passage that is closed in a switching position, opens in a neutral position, and communicates with a tank, and also A bypass type pressure compensating valve is connected between the pump line and the tank to control the differential pressure before and after the throttle in the throttle switching valve to a constant level, and a discharge rate control section of the variable pump is switchably connected to the pump line and the tank. At the same time, the pump line is connected to the pilot chamber of the discharge rate control valve, and the pump line is connected to the spring chamber of the discharge rate control valve via a crest, and the spring chamber is connected to the pilot line to switch the aperture. Since it is connected to the pilot passage of the valve, the bypass type pressure compensation valve can act as a surge absorption valve and the surge absorption valve can be omitted. The chamber is communicated with the tank through the pilot passage, and by operating the discharge amount control valve, the variable pump can be operated with a small discharge flow rate and discharge pressure, thereby reducing power loss. Moreover, in the neutral state, the pilot line is filled with fluid, so when the throttle switching valve is switched and the discharge rate control valve and the discharge rate control section of the variable pump are operated, the discharge rate control valve is Responsiveness can be made quick.

Furthermore, if a pilot relief valve is connected to the spring chamber of the discharge amount control valve, the discharge flow rate of the variable pump can be controlled to a very small amount when the pilot relief valve is relieved, thereby reducing power loss.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram of one embodiment of the present invention, and FIG. 2 is a circuit diagram of a modified example. 1... Possible W pump, 2... Pump line, 3...
Throttle switching valve, 4... Hydraulic cylinder, 8... Pilot passage, 13... Bypass type pressure compensation valve, 22...
Discharge rate control valve, 27...! 12, 29...Pilot line, 33...Pilot relief valve. Patent applicant: Daikin Industries, Ltd. Patent attorney Aoyama Hajime and two others

Claims (2)

[Claims] (1) Pump line (2) of summer displacement pump (1)
) is provided with a throttle switching valve having a pilot passage (8) which is closed in the switching position and opened in the neutral position and communicates with the tank, and a bypass type pressure compensating valve is provided between the pump line (2) and the tank. 0 sudden is connected to control the differential pressure before and after the throttle in the throttle switching valve to be constant, and the discharge amount control section (company) of the variable displacement pump (1) is connected to the pump line (2) and the tank@ Connect the pump line (2) to the pilot chamber of the discharge control valve ■, which is connected to the spring chamber □ of the discharge control valve ■.
Connect the pump line (2) to □□ via the throttle, and connect the spring chamber (A) to the pilot line (2).
is connected to the pilot passage (8) of the throttle switching valve through the throttle switching valve, and when the throttle switching valve is in the neutral state, the spring chamber device of the discharge amount control valve @ is communicated with the tank via the pilot passage (8). A hydraulic circuit, characterized in that the discharge amount of the summerable displacement pump (1) is reduced by the operation of the discharge amount control valve n. (2) The hydraulic circuit according to claim 1, wherein a pilot relief valve opening is connected to the spring chamber of the discharge amount control valve @.