JPH0158361B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a power-saving hydraulic circuit that controls the discharge amount of a variable displacement pump in accordance with the speed of an actuator.

<Prior Art> Conventionally, as this type of hydraulic circuit, the one shown in FIG. 2 is known (Japanese Patent Laid-Open No. 51-51682). This hydraulic circuit connects the pressure port P of the directional control valve 3 to the pressure line 2 of the variable displacement pump 1,
The pressure before and after the throttle 4 of the directional control valve 3 is applied to the pilot chamber 6 and spring chamber 7 of the power match valve 5. Then, due to the pressure difference between the pilot chamber 6 and the spring chamber 7, the swash plate control cylinder 1a of the variable displacement pump 1 is switched and connected to the pressure line 2 and the tank 8, thereby controlling the discharge amount of the variable displacement pump 1. is controlled to a value corresponding to the throttle opening of the directional control valve 3, so that the variable displacement pump 1 discharges only the amount of oil corresponding to the speed of the hydraulic cylinder 9, so there is no loss of power. Has advantages.

<Problems to be Solved by the Invention> However, in the conventional hydraulic circuit described above, the directional control valve 3 is returned to neutral and the hydraulic cylinder 9
When attempting to stop the hydraulic cylinder 9, the hydraulic cylinder 9 moves by itself due to the inertia of the load. As a result, the load line that supplies pressure oil to the hydraulic cylinder 9 becomes under negative pressure, causing cavitation and noise. Also, when the load line is under negative pressure,
When the hydraulic cylinder 9 is restarted, the hydraulic cylinder 9
suddenly moves, or instead of hydraulic cylinder 9,
When a hydraulic motor is used, there is a problem that it may spin idly, which is dangerous.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a hydraulic circuit that can prevent a load line from becoming a negative pressure state even when an actuator moves by itself, and prevent cavitation while maintaining a power saving effect. There is a particular thing.

<Means for Solving the Problems> In order to achieve the above object, the present invention connects a pair of load ports A and B and a return port R when in neutral state, and connects a pair of load ports A and B to a return port R, as illustrated in FIG. The directional control valve 81 has a structure in which the pressure port P is opened to the tank, while the pressure port P is connected to one load port (A or B) during switching, and the vent port m is connected to the one load port (A or B).
and a variable displacement pump 11 connected to the pressure port P of this directional control valve 81 via a pressure line 51.
, an actuator 92 having an inertial load connected to load ports A and B of the directional control valve 81 via load lines 52 and 53, and the pressure line 5.
1 and a spring chamber connected to the vent port m, and a power match valve 12 that switches and connects the discharge amount control section 11a of the pump to the pressure line 51 and the tank based on the pressure difference between the two chambers. , a speed regulating means 13 that slows down the response speed of the discharge amount control section 11a to the discharge amount reduction side that controls the discharge amount of the variable displacement pump 11; a pilot chamber connected to the pressure port P of the directional control valve 81; A pressure reducing type pressure compensating valve 22 is provided with a spring chamber connected to the vent port m and reduces the pressure in the pressure line 51 by the pressure difference between the two chambers, and a pilot chamber is connected to the pressure line 51 and connected to the vent port m. a normally closed 2-port valve 40, which is equipped with a pilot chamber connected to the vent port m and a spring chamber connected to the vent port m, and which opens and closes a bypass line 56 branching from the pressure line 51 based on the pressure difference between the two chambers; A back pressure means 75 that provides resistance to the flow from the confluence line with the tank line 55 of the directional control valve 81 to the tank, and a back pressure means 75 that is provided between the load lines 52 and 53 and converts the flow to the actuator in the neutral state into a free flow. A brake valve 91 is provided with a check valve to make the spring differential pressure corresponding to the spring force of the power match valve 12 larger than the spring differential pressure corresponding to the spring force of the pressure reducing type pressure compensating valve 22. It is characterized in that the spring differential pressure corresponding to the spring force of the two-port valve 40 is more closely related than the spring differential pressure corresponding to the spring force of the valve 12.

<Function> When the directional control valve 81 is located at the switching position and the actuator to which the load is connected is constantly driven, the hydraulic circuit configured as described above is operated by the load pressure of the pressure line 51 and the pilot line 62. , the power match valve 12 is switched and the variable displacement pump 1
The discharge amount of No. 1 is controlled to the amount of oil to be supplied to the load line. At this time, the two-port valve 40 is closed due to the spring pressure difference. The pressure reducing type pressure compensation valve 22 controls the differential pressure before and after the directional control valve 81 to be constant. on the other hand,
When the directional control valve 81 is located at the neutral position and the load is to be decelerated, the load moves by itself due to inertia and negative pressure is generated in the load line. However, at this time, by opening the spring chamber of the 2-port valve 40 to the tank, the 2-port valve 40 is opened by the pressure of the pressure line 51.
Replenishment oil generated in the manner described later in the pressure line 51 is discharged to the tank line 55, and back pressure is transmitted by the back pressure means 75, and the direction switching is located at the neutral position and connected to the ABR. valve 81
is supplied to the load line that is about to reach negative pressure. Cavitation is thus prevented.

The oil supplied to the negative pressure line is generated as follows. That is, when the required flow rate is small, such as when the load is decelerated, the power match valve 21 controls the pressure to the discharge amount control section 11a to reduce the discharge amount.
Due to the action of
It is discharged through port valve 40 to tank line 55.

<Examples> Hereinafter, the present invention will be described in detail with reference to illustrated examples.

As shown in Fig. 1, this hydraulic circuit includes a variable capacity pump unit 10 whose discharge amount is adjusted according to the load, and a variable displacement pump unit 10 that reduces the pressure of the oil from the pump unit 10 to a constant pressure corresponding to the load and switches it. The switching valve unit 80 to be connected and the switching valve unit 80
The tank line 55 is connected to the return port R of the switching valve 81 of the switching valve unit 80, and the pressure line 51 from the pump unit 10 is provided. A normally closed two-port valve 40 is installed between the two and supplies oil from the variable displacement pump 11 to the load line 53.

The pump unit 10 includes a variable displacement pump 1
1, a so-called power match valve 12 consisting of a 2-position 3-port switching valve, and a throttle valve 13 with a check.
A pilot relief valve 14 is provided. The control section 11a of the variable displacement pump 11, for example, consisting of a swash plate control cylinder, is connected in series with a check throttle valve 13 and a power match valve 1.
2 to the branch line 60 of the pressure line 51 from the variable displacement pump 11, and manually switches the power match valve 12 corresponding to the load to the control unit 11 at its symbol position _a1 .
a to the pressure line 51, and the variable displacement pump 1
1 to the neutral side to reduce the discharge amount, and at the symbol position a ₂ , the control unit 1
1a is opened to the tank to return the variable displacement pump 11 to the maximum discharge rate, and the throttle 13a of the checked throttle valve 13 controls the response speed to the side where the discharge rate of the variable displacement pump is decreased.
The switching of the power match valve 12 is performed by the hydraulic pressure of a pilot line 61 connected to a branch line 60 of the pressure line 51 applied to one end, the spring pressure of the spring 12a applied to the other end, and the load lines 52, 5.
It is actuated by the pressure of a pilot line 62 which is switch-connected to 3. By switching the power match valve 12, the discharge pressure of the variable displacement pump 11 is adjusted to a predetermined pressure (for example, 6 kg/cm ² ) higher than the load by the spring 12a, that is, according to the spring force of the spring 12. It is made to have a differential pressure. In addition, the above pilot line 62
A branch line 63 leading to the tank is provided, and a relief valve 14 is provided in the middle of the line 63. When the pressure in the pilot line 62 exceeds the set pressure, the relief valve 14 is opened to the tank, and the pilot line 62 is opened to the tank. 62 is limited within a certain limit, and the maximum discharge pressure of the variable displacement pump 11 is limited by controlling the power match valve 12.

The switching valve unit 80 includes a switching valve 81 with a so-called ABR connection type neutral vent unload passage, and a pressure reducing type pressure compensating valve 22, in which both ports A and B on the outlet _side and the return port R are connected in the neutral state b2. The pressure reducing type pressure compensating valve 22 and the switching valve 81 are connected in series to the pressure line 51. The spring differential pressure of the pressure reducing type pressure compensation valve 22 is the power match valve 12.
is smaller than the spring differential pressure.

The hydraulic motor unit 90 also includes a brake valve 91 with a check valve for both passages when in neutral, and a load 11.
Hydraulic motor 92 connected to 0 and relief valve 9
3 and 94, and check valves 95 and 96, and these elements are connected by connecting the load lines 52 and 53 from the switching valve 81 to the ports C and D on the inlet side of the brake valve 91, respectively. At the same time, the ports E and F on the outlet side of the brake valve 91 are respectively connected to the ports G and H of the hydraulic motor 92 via the load lines 97 and 98, while the load lines 97 and 98 are connected to each other. , each relief valve 9 in the middle
3 and 94 are connected by parallel lines 99 and 100 installed in opposite directions, respectively, and a drain line 10 is connected to the hydraulic motor 92 leading to the tank.
1 and the drain line 101
Then, the load lines 97 and 98 are connected to each other through the lines 102 and 103 in which the check valves 95 and 96 are installed, respectively, and the drain line 10 is connected to the drain line 10.
Oil can flow into each load line 97, 98 from load line 1, but oil cannot flow into drain line 30 from each load line 97, 96. Therefore, when the switching valve 81 is in the neutral position _b2 as shown in FIG. 1, the pressure line 51 is closed and the hydraulic motor 92 is closed.
operation is stopped and the pilot line 62 leads to the tank, so that the power match valve 12 is placed in its symbol position a ₁ , so that the swash plate of the variable displacement pump 11 is placed in the neutral position and the The variable displacement pump 11 discharges almost no oil and begins to operate under no load.

When the switching valve 81 is switched to the left or right symbol position b ₁ or b ₃ in FIG. 1, the inlet side vent port m is connected to the switching valve 81.
The pilot line 62 connected to the load port A or B connected to the pressure port P of the inlet side vent port m is connected to the load line 52
or connected to 53. Therefore, at this time, the variable displacement pump 11 discharges oil at a pressure equal to the pressure of the load line from the pilot line 62 plus the spring pressure of the spring 12a of the power match valve 12 by the power match valve 12, Further, the pressure reducing valve 22 reduces the oil pressure in the pressure line 51 to the pressure in the load line, and supplies oil to the switching valve 81. Therefore, the so-called power match circuit including the switching valve unit 80 and the variable displacement pump unit 10 is connected to the load line 5.
Only the necessary oil sent to the pumps 2 and 53 is discharged from the pump 11, and unnecessary oil is not discharged.

On the other hand, the two-port valve 40 is provided in the middle of a bypass line 56 connecting a pressure line 51 between the pump unit 10 and the switching valve unit 20 and a tank line 55.

The two-port valve 40 is operated by the hydraulic pressure of a pressure line 51 applied to one end and the spring 4 applied to the other end.
It is operated by the spring pressure of 0a and the hydraulic pressure of the pilot line 62 applied to the other end via the pilot line 71, and a check throttle valve 72 is installed in the middle of the pilot line 71. Therefore, when the hydraulic pressure in the pressure line 51, which is the discharge pressure of the variable displacement pump 11, exceeds the pressure obtained by adding the spring pressure of the spring 40a to the hydraulic pressure in the pilot line 62, the two-port valve 40 closes the two-port valve 40.
The oil in the spring chamber of the port valve 40 is quickly discharged to the tank through the check 72b of the check throttle valve 72, and the 2-port valve 40 is opened, and the oil in the pressure line 51 is transferred to the tank line 55,
The switching valve 81 in the neutral position b ₂ quickly becomes supplied to the load line 53 where negative pressure is to be generated. On the other hand, when the oil pressure in the pressure line 51 decreases, oil is regulated by the throttle 72a of the check throttle valve 72 and oil flows into the spring chamber again.
The two-port valve 40 is closed, and the valve 40 is closed by adjusting the throttle of the throttle 72a.
The closing time can be adjusted. The spring pressure of the spring 40a of the two-port valve 40 is as follows:
The spring pressure is set to be greater than the spring pressure of the spring 12a of the power match valve 12. That is, 2
The spring differential pressure of the port valve 40 is greater than the spring differential pressure of the power match valve 12.

Further, in the tank line 55 on the downstream side of the confluence of the bypass line 56 and the tank line 55,
A check valve 75 with a spring is provided as a back pressure means so that a constant back pressure can be applied to the tank line 55. The hydraulic circuit configured as described above operates as follows.

First, move the switching valve 81 to the right symbol position b ₁
At the same time, the brake valve 91 is located at the upper symbol position _c1 , and while the hydraulic motor 92 is rotating the load 110, the switching valve 81 and the brake valve 91 are now forced to the neutral position. Even if you try to stop the hydraulic motor 92 by positioning it in the positions b ₂ and c ₂ or decelerating the hydraulic motor 92 by switching the switching valve 81 and the brake valve 91 to the neutral direction, the load 110 will continue to rotate for a while due to inertia. At the same time, the hydraulic motor 92 also rotates, and the rotation of the hydraulic motor 92 and the discharge of oil into the drain line 101 combine to create negative pressure in the load lines 97 and 53, while the tank line 55 is under pressure. Because of the power match circuit, sufficient oil pressure is not generated to replenish the oil in the load lines 97, 53 that generated the negative pressure. However, surge pressure is generated in the pressure line 51 due to the switching of the switching valve 81, and the 2-port valve 40 is opened to the tank, causing oil to flow from the pressure line 51 into the tank line 55, further creating negative pressure. It flows into the generated load lines 53, 97. Therefore, since the back pressure in the tank is not large enough, the drain line 101 is passed through each check valve 95, 96.
Even if it is not possible to replenish tank oil to each load line 97, 98, the load line 97 generates negative pressure by allowing the oil in the pressure line 51 to flow into the tank line 55 for a certain period of time as described above. ，
53 can be supplied with oil.

The relief valves 94 and 93 are opened to the other load line to protect the hydraulic motor 92 when the pressure in each of the load lines 97 and 98 exceeds a set pressure.

In addition, the check valve 75 with a spring in the tank line 55 prevents the oil flowing out from the two-port valve 40 from directly flowing into the tank.
This provides a certain resistance between the tank and the tank so that the water flows into the tank. Instead of the spring-loaded check valve 75, a line filter, a long pipe, or a throttle valve may be used to provide resistance.

In addition, the 2-port valve 40 opened as described above
When the swash plate of the variable displacement pump 11 returns to the predetermined position and the oil pressure in the pressure line 51 becomes less than the pressure equal to the oil pressure in the pilot line 62 plus the spring pressure of the spring 40a, the pump attempts to close, but the Due to the presence of the throttle 72a of the throttle valve 72, the amount of oil from the pilot line 62 that is about to flow into the spring chamber of the two-port valve 40 is adjusted according to the magnitude of the negative pressure in the load lines 53, 97. Thus, the time period during which the two-port valve 40 is open is controlled.

Further, in the above embodiment, the check throttle valve 13 is provided between the power match valve 12 and the control section 11a of the variable displacement pump 11, but the throttle valve is simply placed on the branch line 60 of the pressure line 51, 60 and the pilot line 61 and the power match valve 12 to control the response speed of the variable displacement pump 11 to the side that reduces the discharge amount. In this case, even without providing the check valve 13b as in the above embodiment, the oil can be quickly discharged from the control section 11a to the tank, and the response speed to increase the discharge amount of the variable displacement pump 11 can be increased. can do.

<Effects of the Invention> As is clear from the above description, the hydraulic circuit of the present invention uses the power match valve to control the discharge amount of the variable displacement pump, so it does not cause power loss and is effective in saving energy.

In addition, a directional control valve is connected between the pressure line of the variable displacement pump and the load line, and the directional control valve is connected to the load line through the return port of the directional control valve, which is connected to the ABR when in neutral, and is connected to the back pressure means. A normally closed type 2-port valve was installed between the tank line having a , when the actuator decelerates, the variable displacement pump discharges extra oil for a while, and the two-port valve is opened to the tank line by the action of the pressure line pressure, so the load that is about to generate negative pressure is Oil can be supplied to the line through the directional control valve connected to the ABR when the line is in neutral, thus preventing cavitation from occurring.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram of the present invention, and FIG. 2 is a conventional hydraulic circuit diagram. 11... Variable displacement pump, 12... Power match valve, 110... Load, 51... Pressure line, 5
2, 53, 97, 98...Load line, 55...
Tank line, 40... Normally closed 2-port valve, 81... Directional control valve, 91... Brake valve with check valve, 92... Hydraulic motor, 13, 7
2... Throttle valve with check, 13a, 72a... Throttle.

Claims (1)

[Claims] 1. When neutral, a pair of load ports A and B and return port R are connected, and vent port m is opened to the tank, while when switching, pressure port P is connected to one load port (A or B). and a variable displacement pump connected to the pressure port P of the directional control valve 81 via a pressure line 51. 11, an actuator 92 having an inertial load connected to load ports A and B of the directional control valve 81 via load lines 52 and 53, and a spring connected to the pilot chamber and vent port m connected to the pressure line 51. The discharge amount control unit 1 of the pump is provided with a chamber, and the pressure difference between the two chambers causes
1a to the pressure line 51 and the tank, and a speed regulating means 13 that slows down the response speed of the discharge amount control section 11a, which controls the discharge amount of the variable displacement pump 11, to the discharge amount decreasing side. and a pressure reducing type pressure compensating valve 22 which includes a pilot chamber connected to the pressure port P of the directional control valve 81 and a spring chamber connected to the vent port m, and reduces the pressure in the pressure line 51 by the pressure difference between the two chambers. , comprising a pilot chamber connected to the pressure line 51, a pilot chamber connected to the vent port m, and a spring chamber connected to the vent port m,
a normally closed two-port valve 40 that opens and closes a bypass line 56 branching from the pressure line 51 based on the pressure difference between the two chambers; and the bypass line 56 and the direction control valve 81.
A back pressure means 75 that provides resistance to the flow from the confluence line with the tank line 55 to the tank, and a check valve that is interposed in both the load lines 52 and 53 and allows the flow to the actuator to be a free flow in the neutral state. A brake valve 91 is provided, the spring pressure difference corresponding to the spring force of the power match valve 12 is made larger than the spring pressure difference corresponding to the spring force of the pressure reducing type pressure compensating valve 22, and the spring force of the power match valve 12 is increased. A hydraulic circuit characterized in that a spring differential pressure corresponding to the spring force of the two-port valve 40 is made larger than a spring differential pressure corresponding to the spring force. 2. The hydraulic circuit according to claim 1, wherein the speed regulating means 13 is a check throttle valve 13 provided between the discharge amount control section 11a and the power match valve 12.