JPH0381003B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydraulic control circuit capable of performing both negative control and load sensing control.

(Prior Art) The conventional hydraulic control circuit shown in FIG.
6 is directly led to the shuttle valve 67, and the other points are the same as the present invention.

However, as mentioned above, the second pilot passage 66
If it is directly connected to the shuttle valve 67, the following problems will occur.

That is, when the inflow port 69 of the flow rate adjustment switching valve 68 starts to open, in other words, when controlling a minute flow rate near the neutral position of the switching valve 68, the inflow port 69 and the neutral port 70 open simultaneously. That's what I do.

FIG. 9 shows the relationship between the inflow port and the neutral port. In FIG. 9, the vertical axis represents the opening area of both ports, and the horizontal axis represents the amount of displacement of the spool of the flow rate adjustment switching valve.

Curve a shows the characteristics of the neutral port, and curve b shows the characteristics of the inflow port.

If both ports open at the same time as described above, load sensing control cannot be performed unless the load pressure of the actuator 71 becomes higher than the negative control pressure during minute flow rate control. The boundary is shown by straight line c in Fig. 9, and even when the inflow port is open, there is a negative control region n, and as mentioned above, the load sensing control region l occurs from the point when both pressures become equal. .

Therefore, when controlling the minute flow rate mentioned above, unless the load pressure rises to a certain level, the discharge amount of the variable pump cannot be adjusted according to the load pressure, and for this reason, conventional control circuits have the disadvantage of large energy loss. .

An object of the present invention is to provide a hydraulic control circuit that enables load sensing control even during minute flow rate control of a flow rate adjustment switching valve and reduces energy loss during the minute flow rate control.

(Means for Solving the Problems) This invention provides a flow rate adjustment switching valve that forms a load detection port that detects the load pressure of an actuator and communicates the load detection port with a tank when in a neutral position; When the switching valve is in the neutral position, the valve is provided in a neutral passage communicating with the variable pump through its neutral port or in a pilot passage communicating with the auxiliary pump, so that oil discharged from the variable pump or the auxiliary pump passes through it. A throttle that generates a pressure difference between the front and rear, a pilot passage leading from the load detection port, and a pilot passage leading to the pilot pressure generated by the throttle;
A shuttle valve that merges these two pilot passages and selects the pilot passage with higher pressure, a main pilot passage that guides the pilot pressure from this shuttle valve, and one pilot chamber are connected to the discharge pipe of the variable pump. A tilting system equipped with differential pressure sensing control that controls the tilting angle control cylinder using the differential pressure between these two, and controls the discharge amount of the variable pump so that the differential pressure before and after the flow rate adjustment switching valve is always constant. A pilot port is formed in the flow rate adjustment switching valve, and the pilot pressure generated by the throttle is communicated with the shuttle valve through the pilot port, so that when the flow rate adjustment switching valve is in the neutral state, The present invention is characterized in that when the pilot port opens and the flow rate adjustment switching valve is switched to the operating position, the pilot port closes before the inflow port opens.

(Function) Since the present invention is constructed as described above, when the inflow port of the flow rate adjustment switching valve is opened, the pilot port thereof is in a closed state. Therefore, even during minute flow rate control, since the pilot port of the flow rate adjustment switching valve is closed, pilot pressure for negative control no longer acts on the shuttle valve.

(Embodiment of the present invention) In the first embodiment shown in FIG. 1, a flow rate adjustment switching valve 2 is provided on the downstream side of the variable pump 1. A tank port 4, a load detection port 5, a neutral port 6, and a pilot port 7 are formed.

The inflow port 3 communicates with the variable pump 1 via the load check valve 8 and the main passage 9, and when the flow rate adjustment switching valve 2 is in the neutral position shown, the inflow port 3 is closed. By switching the flow rate adjustment switching valve 2 to either the left or right side, a relationship is established in which it communicates with either the actuator channel 11 or 12 that communicates with the actuator 10.

The tank port 4 directly communicates with the tank 13, while the actuator channel 11 or 12 communicates with the tank 13 depending on the switching position of the flow rate adjustment switching valve 2.

The load detection port 5 described above communicates with the tank port 4 when the flow rate adjustment switching valve 2 is in the neutral position shown, and also communicates with the flow rate adjustment switching valve 2.
When the actuator is switched to the left or right, it communicates with the flow path that supplies pressure oil among the actuator flow paths 11 and 12, and transfers the load pressure of the flow path that supplies pressure oil to the first pilot path 14. via shuttle valve 15
The structure is designed to lead to.

The neutral port 6 is configured to open when the flow rate adjustment switching valve 2 is in the neutral position and close when the flow rate adjustment switching valve 2 is switched to either the left or right side. When the neutral port 6 is open as described above, the variable pump 1 is supplied to the tank 1 via the branch passage 16 → this neutral port 6 → the neutral flow passage 17.
8, but a first throttle 19 and a second throttle 20 are provided in the path that reaches the tank 18 via the neutral flow path 17.

Furthermore, in the passage process of the neutral flow path 17,
A low pressure relief valve 21 is connected upstream of the first throttle 19.

The pilot port 7 is connected to the flow rate adjustment switching valve 2.
It opens when the valve is in the neutral position and closes when the flow rate adjustment switching valve 2 is switched to either the left or right side.

The upstream side of the pilot port 7 is connected to the aforementioned shuttle valve 15 via a passage 22a, and the downstream side thereof is connected to the neutral flow between the first throttle 19 and the second throttle 20 via a passage 22b. It is connected to Route 17. Therefore, when the flow rate adjustment switching valve 2 is in the neutral position, the passages 22a and 22b communicate with each other via the pilot port 7, but in this communicating state, the passages 22a and 22
b together form the second pilot passage 22.

By switching the flow rate adjustment switching valve 2 as described above to either the left or right side, the inflow port 3 communicates with either the actuator flow path 11 or 12 as described above. Accordingly, the opening area of the inflow port 3, that is, the aperture area thereof is determined.

In addition, when controlling the flow rate adjustment switching valve 2 near its neutral position in order to maintain the opening area of the inflow port 3 small and supplying a minute flow rate to the actuator 10, the pilot port 7 closes and the neutral port 6 closes. We have a somewhat open relationship.

Note that the reason why the neutral port 6 is kept slightly open during the minute flow rate control is to bleed off the oil from the variable pump 1 from the neutral port 6. If the oil of the variable pump 1 is not bled off from the neutral port 6 in this manner, the entire amount of oil discharged from the variable pump 1 will flow into the inflow port 3, making it impossible to perform the minute flow rate control described above.

An output detection passage 23 for detecting the output of the variable pump 1 is connected to the main passage 9 between the variable pump 1 and the flow rate adjustment switching valve 2 as described above, and this output detection passage 23 is connected to a differential pressure sensing It communicates with a tilting angle control device 26 consisting of a control valve 24 and a safety valve 25.

The differential pressure sensing control valve 24 guides the pilot pressure of the output detection passage 23 to one pilot chamber 27, and the other pilot chamber 28 is provided with a spring 29, and is connected to the shuttle via the main pilot passage 30. It is connected to valve 15.

The differential pressure sensing control valve 24 operates according to the pilot pressure flowing into the pilot chambers 27 and 28, and when the pressure in one pilot chamber 27 is higher than the pressure in the other pilot chamber 28, It moves against the spring 29 to increase its opening area.

When the opening area of the differential pressure sensing control valve 24 increases, the variable pump 1 flowing in from the output detection passage 23
The amount of oil passing through increases, and the flow rate flows into the passage 31.

On the other hand, when the pilot pressure in the pilot chamber 28 is higher, the opening area of the differential pressure sensing control valve 24 becomes smaller, and the amount of flow into the passage 31 becomes smaller.

When the flow rate to the passage 31 is large, the oil trying to flow from the passage 31 to the tank 32 suffers a large pressure loss due to the orifice 33. flows into. When oil flows into the tilt angle control cylinder 34 in this manner, the piston thereof moves against the spring, reducing the discharge amount of the variable pump 1.

On the other hand, when the opening area of the differential pressure sensing control valve 24 becomes smaller and the flow rate flowing into the passage 31 decreases, the pressure loss due to the orifice 33 becomes smaller. Oil in the control cylinder 34 also flows into the tank 32 via the orifice 33. When the oil in the tilt angle control cylinder 34 flows into the tank 32, the piston moves due to the action of the spring.
The discharge amount of the variable pump 1 is increased.

When the flow rate adjustment switching valve 2 is in the neutral position shown, the inflow port 3 is closed, so that the entire amount of oil discharged from the variable pump 1 flows into the neutral port 6. The oil that has flowed into this neutral port 6 flows through the neutral flow path 17 → first throttle 19 → second throttle 20
It reaches tank 18 via. When the oil from the variable pump 1 passes through the first throttle 19 in this way,
Since a pressure loss occurs there, the pressure reaching the second throttle 20 is reduced, and a pressure difference is generated before and after the second throttle 20 as well.

The prepressure of the second throttle 20 flows into the passage 22b as pilot pressure, and also reaches the passage 22a through the open pilot port 7, from which it flows into the shuttle valve 15.

At this time, since the load detection port 5 is in communication with the tank 13, the first pilot passage 14 becomes the tank pressure.
Then, the pilot pressure from the second pilot passage 22 is selected, and the pilot pressure flows into the other pilot chamber 28 of the differential pressure sensing control valve 24 via the main pilot passage 30.

At the same time, the pressure in the main passage 9, that is, the first
The prepressure of the throttle 19 flows into one pilot chamber 27 of the differential pressure sensing control valve 24 via the output detection passage 23.

Therefore, in the differential pressure sensing control valve 24, the pressure P ₁ in one pilot chamber 27, the pressure P ₂ in the other pilot chamber 28, and the spring force FD of the spring 29 are as follows: P ₁ =P ₂ +F Balance will be achieved in this relationship. For example, pilot compartment 2
When the pilot pressure P ₁ on the 7 side is higher than the pilot pressure P ₂ on the pilot chamber 28 side, the differential pressure sensing control valve 24 moves against the spring 29 and stops at a position balanced to the above P ₂ +F. hand,
Determine the opening area at the balance position.

Oil flows into the passage 31 according to the opening area determined as above, and the orifice 33
The front pressure flows into the tilt angle control cylinder 34 and reduces the discharge amount of the variable pump 1.

If the discharge amount of the variable pump 1 decreases, the differential pressure before and after the second throttle 20 also decreases, but as long as the condition of P ₁ = P ₂ +F is satisfied in this state,
The opening area of the differential pressure sensing control valve 24 is kept constant.

On the other hand, if P ₁ becomes lower than P ₂ +F, the opening area of the differential pressure sensing control valve 24 becomes smaller, and the discharge amount of the variable pump 1 increases accordingly.

The discharge amount of the variable pump 1 is determined as described above, but the discharge amount is determined within a range that satisfies the condition of P ₁ = P ₂ +F, and is ultimately determined by the difference between the pump discharge pressure and the pilot pressure. The pressure is always kept constant to be equal to the spring force, and negative control is possible when the flow rate adjustment switching valve 2 is held at the neutral position.

Furthermore, if the flow rate adjustment switching valve 2 is switched to either the left or right side, the pilot port 7 is closed and the communication state of the second pilot passage 22 is cut off, so that the pilot pressure flowing into the passage 22b is
There is no flow to the shuttle valve 15 at all.

For example, when the flow rate adjustment switching valve 2 is switched to the left side position in the drawing, the inflow port 3 communicates with the actuator flow path 11, but as described above, the opening of the inflow port 3 depends on the switching amount of the flow rate adjustment switching valve 2. The area is determined. Once the opening area of this inflow port 3 is determined, the inflow port 3
A differential pressure occurs between the front and rear.

Of the differential pressure generated before and after the inflow port 3 as described above, the front pressure is transferred to one pilot chamber 2 of the differential pressure sensing control valve 24 via the output detection passage 23.
The load pressure on the actuator 10 side flows into the other pilot chamber 28 via the load detection port 5 → first pilot passage 14 → shuttle valve 15 → main pilot passage 30.

Therefore, in this case as well, the discharge amount of the variable pump 1 is controlled within a range that satisfies the equation P ₁ =P ₂ +F described above, and a flow rate corresponding to the load is supplied.

In other words, as the load on the actuator 10 increases, the differential pressure across the inflow port 3 changes. Then, the differential pressure sensing control valve 24 operates in accordance with the change in the differential pressure, and controls the discharge amount of the variable pump 1 within a range that satisfies the condition of P ₁ = P ₂ +F. will be carried out. In other words, the differential pressure before and after the inflow port 3 is controlled to be always constant.

In the second embodiment shown in FIG. 2, a flow rate adjustment changeover valve 35 having the same configuration as the flow rate adjustment changeover valve 2 is provided separately, and these flow rate adjustment changeover valves are connected in series. 35 is connected to an actuator 36.

The flow rate adjustment switching valve 35 forms an inflow port 37, a tank port 38, a load detection port 39, a neutral port 40, and a pilot port 41 similarly to the flow rate adjustment switching valve 2.

The neutral port 40 of this flow rate adjustment switching valve 35
is communicated with the neutral port 6 of the flow rate adjustment switching valve 2 through the passage 42, and when the flow rate adjustment switching valve 2 is held at the neutral position, the oil from the variable pump 1 is transferred from the main passage 9 to the branch passage. 16→neutral port 6→flow into this neutral port 40 via passage 42. When the flow rate adjustment switching valve 35 is in the neutral position shown, the passage 4
The oil that has flowed in through the channel 2 is guided to the neutral flow path 17.

Further, the inflow port 37 communicates with the main passage 9 via a parallel passage 43, and pressure control valves 44 and 45 are provided upstream of the inflow port 3 and the inflow port 37.

These pressure control valves 44, 45 are connected to pilot channels 46, 47 from their outlet sides, that is, from their downstream sides.
The pilot pressure is introduced into the pilot chambers 48 and 49 of one of the pressure control valves 44 and 45 through the pressure control valves 44 and 45, respectively.

Further, the other pilot chambers 50 and 51 are provided on the opposite side from the one pilot chamber 48 and 49,
A spring 5 is installed in the pilot chambers 50 and 51.
2, 53 internally, and the actuator 1
0, the load pressure from the actuator 36 is led from the inflow port 3 and the load detection port 39.

The load detection port 5 and the load detection port 39 communicate with the shuttle valve 54 via the passage 14a and the passage 14b. 54 and the first
The water flows into the pilot passage 14.

Further, the pilot port 41 is connected to the passage 22c.
through the pilot port 7 of the flow rate adjustment switching valve 2.
It is connected to the line between the first aperture 19 and the second aperture 20 via a passage 22b.

These flow rate adjustment switching valves 2 and 35 are also completely similar to those in the first embodiment, and when they are in the neutral position, the neutral ports 6, 40 and the pilot ports 7, 41 open, and the inflow ports 3 and 37 open.
closes.

By switching the flow rate adjustment switching valves 2 and 35 to either the left or right side, the neutral port and the pilot port are closed, and the inflow ports 3 and 37 are opened, but the timing of opening and closing of these is the same as in the first embodiment. It's exactly the same.

Therefore, when both the flow rate adjustment switching valves 2 and 35 are held in the neutral position, the total amount of oil discharged from the variable pump 1 is as follows: Main passage 9 → Branch passage 16 → Neutral port 6 → Passage 42 → Neutral port 40 → It reaches the tank 18 via the neutral flow path 17 → first throttle 19 → second throttle 20.

Therefore, a flow is generated in the first restrictor 19 and the second restrictor 20, and a pilot pressure is generated in the same manner as in the first embodiment. This pilot pressure is applied to the passage 22b.
→ Pilot port 41 → Passage 22c → Pilot port 7 → Shuttle valve 1 via passage 22a
5 and further flows into the other pilot chamber 28 of the differential pressure sensing control valve 24 through the main pilot passage 30.

At the same time, the oil discharged from the variable pump 1 flows into one pilot chamber 27 of the differential pressure sensing control valve 24 via the output detection passage 23, so that P ₁ =P ₂ as in the first embodiment. The discharge amount of the variable pump 1 is negatively controlled within a range that maintains the relationship of +F.

When the flow rate adjustment switching valve 2 or 35 is switched to either the left or right position other than the neutral position, the pilot port of the switched valve closes, and therefore the second
Since the communication state of the pilot passage 22 is cut off, the negative control is canceled.

For example, if the flow rate adjustment switching valves 2 and 35 are switched at the same time, those pressure control valves 44 and 45
works like this:

First, a case will be described in which the flow rate adjustment switching valve 2 is switched to the left position. Pressure oil that has passed through the pressure control valve 44 flows into the actuator 10 from the inflow port 3 through one of the actuator flow paths 11. The return oil from the actuator 10 is
It returns to the tank 13 from the other actuator flow path 12 via the tank port 4.

At this time, the oil that has passed through the pressure control valve 44 is
The pressure control valve 4 is connected to the pressure control valve 4 via the pilot flow path 46.
4 into one of the pilot chambers 48.

Further, the load pressure of the actuator 10 flows into the other pilot chamber 50 from the load detection port 5.

Therefore, in the above state, the pressure control valve 44 functions similarly to the differential pressure sensing control valve 24.

That is, the pressure P ₁ in one pilot chamber 48,
The flow rate passing through the pressure control valve 44 is controlled within the range where the pressure P ₂ in the other pilot chamber 50 and the spring force F of the spring 52 maintain the relationship P ₁ =P ₂ +F.

Since the pressure control valve 44 is controlled as described above, a flow rate corresponding to the load is supplied to the actuator 10.

Then, the surplus flow rate from the variable pump 1 flows into the pressure control valve 45 via the parallel passage 43,
This 45 also performs the same control as the pressure control valve 44 and supplies the required flow rate to the actuator 36 .

In the second embodiment as described above, since the pressure control valves 44 and 45 are provided, even when the load pressure of one actuator is low, the oil from the variable pump 1 is supplied only to the low actuator side. This eliminates the inconvenience caused by

The third embodiment shown in FIG.
A relief valve 55 and a throttle 56 are provided in the flow process from the main passage 7 to the tank 57, while a pilot passage 58 is branched from the main passage 9, and the pilot passage 58 passes through the pilot port 7 and the pilot port 41. Shuttle valve 15
A relationship that reaches out.

A flow rate adjustment throttle valve 59 is provided in the pilot passage 58 on the upstream side of the flow rate adjustment switching valve 2, and controls the pilot pressure supplied to the shuttle valve 15 when the flow rate adjustment switching valves 2 and 35 are in the neutral position. It is configured to adjust.

When the flow rate adjustment switching valves 2 and 35 are in the neutral position shown in the figure, the oil discharged from the variable pump 1 passes from the neutral flow path 17 through the throttle 56 to the tank 5.
As the oil flows through the throttle 56, a pressure difference is generated before and after the throttle. The prepressure of the throttle 56 generated in this way passes through the flow rate adjusting throttle valve 59 → pilot port 7 → pilot port 41 → second pilot passage 22 to reach the shuttle valve 15, and from there to the main pilot passage 30. It flows into the other pilot chamber 28 of the differential pressure sensing control valve 24 via the differential pressure sensing control valve 24.

The pilot pressure flowing into the shuttle valve 15 as described above is reduced by the flow rate adjustment throttle valve 59, but the front pressure of the flow rate adjustment throttle valve 59 is controlled by differential pressure sensing via the output detection passage 23. It flows into the pilot chamber 27 of one of the valves 24.

Therefore, this third embodiment also allows negative control similar to that of the second embodiment.

Also in this embodiment, when either the flow rate adjustment switching valve 2 or 35 is switched, the pilot port 7 is opened before the inflow port 3 or 37 is opened.
Or 41 is closed.

Note that the load sensing control of this third embodiment is the same as that of the second embodiment.

In the fourth embodiment shown in FIG. 4, a flow rate adjustment throttle valve 59 is provided downstream of the flow rate adjustment switching valve 35, and the other configurations are the same as the third example.

In the fifth embodiment shown in FIG. 5, a first throttle 60, a second throttle 61, and a relief valve 62 are provided in the pilot passage 58 in place of the flow rate adjusting throttle valve 59 of the third embodiment. be. These first apertures 6
The pilot pressure is introduced from between 0 and the second throttle 61, and the other configuration is the same as that of the third embodiment.

The sixth embodiment shown in FIG. 6 is based on the first throttle 60, second throttle 61 and relief valve 62 of the fifth embodiment.
is provided on the downstream side of the flow rate adjustment switching valve 35,
The other configurations are the same as in the fifth embodiment.

In the seventh embodiment shown in FIG. 7, an auxiliary pump 63 is directly connected to the pilot passage 58 in order to generate pilot pressure flowing into the other pilot chamber 28 of the differential pressure sensing control valve 24. When the flow rate adjustment switching valves 2 and 35 are in the neutral position, oil from the auxiliary pump 63 flows into the pilot passage 58.
→Pilot port 7→Pilot port 41→
It reaches the tank 65 via the throttle 64, and at this time, a pressure difference is generated before and after the throttle 64. The front pressure of this throttle 64 flows as pilot pressure into the other pilot chamber 28 of the differential pressure sensing control valve 24 via the second pilot passage 22 → shuttle valve 15 → main pilot passage 30.

On the other hand, the discharge oil of the variable pump 1 is from the neutral port 6→
It reaches the tank 57 via the passage 42 → neutral port 40 → throttle 56. When the oil passes through the throttle 56 in this way, a differential pressure is generated before and after the throttle 56, and this front pressure passes through the output detection passage 23 to the differential pressure sensing control valve 2.
4 into one of the pilot chambers 27.

Therefore, in this seventh embodiment, the pilot pressure P ₁ in the pilot chamber 27 generated as the front pressure of the throttle 56, the pilot pressure P ₂ in the pilot chamber 28 generated by the auxiliary pump 63, and the spring of the spring 29. The force F is P 1 = P ₁ =
Negative control is performed within the range that maintains the relationship P ₂ +F.

The rest is the same as the sixth embodiment.

(Effect) Since the present invention is configured as described above, when the negative control area n becomes narrow and the inflow port starts to open, for example, as shown in FIG. Enter l.

Since load sensing control is always possible when the inflow port is opened in this way, it is possible to control the pump according to the load pressure no matter how small the flow rate is, and it is possible to reduce energy loss during the minute flow rate.

[Brief explanation of drawings]

Drawings 1 to 7 show embodiments of the present invention; FIG. 1 is a circuit diagram of the first embodiment, and FIG. 2 is a circuit diagram of the second embodiment.
A circuit diagram of the embodiment, FIG. 3 is a circuit diagram of the third embodiment,
4 is a circuit diagram of the fourth embodiment, FIG. 5 is a circuit diagram of the fifth embodiment, FIG. 6 is a circuit diagram of the sixth embodiment, and FIG.
Figure 8 is a circuit diagram of the seventh embodiment, Figure 8 is a conventional circuit diagram, Figure 9 is a graph showing conventional control characteristics, and Figure 1 is a graph showing conventional control characteristics.
FIG. 0 is a graph showing the control characteristics of the present invention. 1... Variable pump, 2, 35... Flow rate adjustment switching valve, 3, 37... Inflow port, 5, 39... Load detection port, 6, 40... Neutral port, 7, 41
...Pilot port, 14, 22, 30, 41
...Pilot passage, 15...Shuttle valve, 2
0, 64... Throttle, 59... Flow rate adjustment throttle valve that exhibits a throttling function, 24... Differential pressure sensing control valve, 26
... Tilt angle control device, 27... One pilot chamber, 28... Other pilot chamber, 30... Main pilot passage, 34... Tilting angle control cylinder.

Claims (1)

[Claims] 1. A flow rate adjustment switching valve that forms a load detection port that detects the load pressure of the actuator and communicates the load detection port with the tank when it is in the neutral position, and a flow rate adjustment switching valve that communicates the load detection port with the tank when the flow rate adjustment switching valve is in the neutral position. A restrictor is provided in the neutral flow path that communicates with the variable pump or the pilot path that communicates with the auxiliary pump, and generates a differential pressure between the front and rear when the oil discharged from the variable pump or the auxiliary pump passes through it, and the above-mentioned load. A pilot passage led from the detection port, a pilot passage leading to the pilot pressure generated by the throttle, a shuttle valve that joins these two pilot passages and selects the pilot passage with higher pressure, and from this shuttle valve. The main pilot passage leading to the pilot pressure of a tilting angle control device equipped with differential pressure sensing control that controls the discharge amount of the variable pump so that it is always constant; a pilot port is formed in the flow rate adjustment switching valve; The pilot pressure is communicated with the shuttle valve through this pilot port, and when the flow rate adjustment switching valve is in the neutral state, the pilot port opens, and the flow rate adjustment switching valve is switched to the operating position, the above-mentioned pressure is applied before the inflow port opens. Hydraulic control circuit configured to close the pilot port.