JP2000257602A - Hydraulic control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device capable of maintaining switching responsiveness of a pilot switching valve, when it is operated, and capable of using a pump delivery amount with no waste. SOLUTION: In this device, having a compensator valve 2 connected to a pump P through a supply flow path 1 to split pressure oil from the pump to pilot switching valves 5, 6 in a side of a priority flow path 4 and a pilot switching valve 7 in a side of a surplus flow path 8, branch flow path 11 connected to the supply flow path, throttle 13 provided in the branch flow path, flow control valve 12 fixedly holding a differential pressure before/behind the throttle, relief valve 16 provided in the downstream of the throttle to generate a pilot pressure in the upstream thereof, and a pilot flow path 17 guiding the pilot pressure to a pilot chamber of the pilot switching valves 5 to 7, to guide a pressure in the upstream of the priority flow path 4 to one pilot chamber 2a of the compensator valve and to guide the pilot pressure to the other pilot chamber 2b, the pilot flow path 17 is connected to the branch flow path between the throttle 13 and the flow control valve 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control apparatus for shunting discharge oil from a single pump and using the split pressure oil for both an actuator and a pilot.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a hydraulic control device which divides the discharge oil of one pump and uses it for both an actuator and a pilot. FIG.
As shown in the figure, the supply flow path 1 through which the discharge oil of the pump P is guided
Is connected to the compensator valve 2. This compensator valve 2 has a priority flow path 4 connected to its priority flow port 3. The priority flow path 4 includes a pilot switching valve 5 for controlling a lift cylinder (not shown),
A pilot switching valve 6 for controlling a tilt cylinder (not shown) is connected in parallel with each other. The pilot switching valves 5 and 6 are configured to shut off the priority flow path 4 when in the neutral position.

A surplus flow path 8 is connected to a surplus flow port 9 of the compensator valve 2. A pilot switching valve 7 for controlling an attachment actuator (not shown) is connected to the surplus flow path 8. The pilot switching valve 7 is configured to connect the surplus flow path 8 to the tank T when in the neutral position. The switching position of the compensator valve 2 is determined by the balance between the acting force of one pilot chamber 2a, the acting force of the other pilot chamber 2b, and the total force of the springs 10; Will be described later in detail.

A branch flow path 11 is connected to the supply flow path 1 on the upstream side of the compensator valve 2. And
A flow control valve 12 is connected to the branch flow path 11, and a fixed throttle 13 is provided downstream of the flow control valve 12. The flow control valve 12
Guides the pressure upstream of the fixed throttle 13 to one of the pilot chambers 12a through the damper orifice 14, and the other pilot chamber 12b provided with the spring 15
In addition, the pressure on the downstream side of the fixed throttle 13 is guided. The flow control valve 12 as described above exerts a control function of keeping the differential pressure across the fixed throttle 13 equal to the spring force of the spring 15 and keeping the flow rate passing therethrough constant. Therefore, a fixed flow rate set by the flow control valve 12 and the fixed throttle 13 is supplied downstream of the fixed throttle 13. Further, a relief valve 16 is connected to the downstream side of the fixed throttle 13 to which a constant flow rate is supplied, and the pressure on the upstream side is maintained at the set pressure of the relief valve 16.

[0005] A pilot flow path 17 is connected between the relief valve 16 and the fixed throttle 13. The pilot flow path 17 is connected to the pilot switching valves 5 to 7.
Are connected to the proportional electromagnetic pressure reducing valves 18a to 20a and 18b to 20b. A shuttle valve 24 is connected to the pilot flow path 17. And this shuttle valve 24
Is connected to the other pilot chamber 2 b of the compensator valve 2. The shuttle valve 24 is a shuttle valve 23
The shuttle valve 23 is connected to load-side pilot passages 21 and 22 for guiding the load pressure of the cylinders of the pilot switching valves 5 and 6, respectively. The shuttle valve 23 selects the higher one of the load pressures of the cylinders connected to the pilot switching valves 5 and 6, and selects the shuttle valve 2
Lead to 4. Therefore, the shuttle valve 24 selects the higher one of the pressure selected by the shuttle valve 23 and the pressure set by the relief valve 16, and guides the selected pressure to the other pilot chamber 2 b of the compensator valve 2. .

On the other hand, the pressure on the upstream side of the pilot switching valves 5 and 6 is guided to one pilot chamber 2 a of the compensator valve 2. Therefore, when the load pressure of the lift cylinder or the tilt cylinder is lower than the pilot pressure, the compensator valve 2 operates with a balance between the pressure on the upstream side of the pilot switching valves 5 and 6 and the pilot pressure set by the relief valve 16. When the load pressure of the lift cylinder or the tilt cylinder is higher than the pilot pressure, the operation is performed in a balance between the pressure on the upstream side of the pilot switching valves 5 and 6 and the pressure on the downstream side thereof. Reference numerals 25 and 26 denote damper orifices, and reference numeral 27 denotes a main relief valve.

In the conventional apparatus as described above, when the pump P is driven with the pilot switching valves 5 and 6 kept at the neutral position, that is, the closed position, as shown in FIG. However, since the pilot switching valves 5 and 6 are closed, no flow occurs in the priority flow path 4. However, the pressure generated in the priority flow path 4 acts on one pilot chamber 2 a of the compensator valve 2. On the upstream side of the compensator valve 2, the discharge oil of the pump P passes through the branch flow path 11.
A pilot pressure corresponding to the set pressure of the relief valve 16 is generated. The pilot pressure generated in the pilot flow path 17 is selected by the shuttle valve 24 and guided to the other pilot chamber 2b of the compensator valve 2.

Therefore, the compensator valve 2 is
The position where the acting force of the pilot pressure in the one pilot chamber 2a and the acting force of the pilot pressure in the other pilot chamber 2b and the spring force of the spring 10 are kept in balance. However, in this case, the pilot pressure of the other pilot chamber 2b is maintained at a constant pressure set by the relief valve 16. Then, if the discharge pressure of the pump P rises from the above balanced state, the acting force of one pilot chamber 2a of the compensator valve 2 overcomes, and the spool of the compensator valve 2 moves to the left, and the position on the right side in the drawing. Switch to. Therefore, the discharge oil of the pump P is discharged to the tank T via the surplus flow path 8 and the neutral flow path of the pilot switching valve 7. Then, in this state, a standby state is set.

On the other hand, the pilot pressure generated on the upstream side of the relief valve 16 is supplied to the proportional electromagnetic pressure reducing valves 18 a to 20 of the pilot switching valves 5 to 7 via the pilot flow path 17.
a, 18b to 20b. These proportional electromagnetic pressure reducing valves 18a to 20a and 18b to 20b reduce the pilot pressure to a pressure proportional to the exciting current, and guide the reduced pressure oil to the pilot chambers 5a to 7a and 5b to 7b. Therefore, each pilot switching valve 5-7 is connected to the pilot chamber 5
Switching is performed by the action of the pressure guided to a to 7a and 5b to 7b.

For example, assuming that only the proportional electromagnetic pressure reducing valve 18a is excited from the standby state and the pilot switching valve 5 is switched, the pilot switching valve 5 maintains the throttle opening according to the switching amount. The pressure on the upstream side of the throttle formed by the opening degree of the pilot switching valve 5 is applied to one pilot chamber 2 of the compensator valve 2.
a, and the pressure downstream of the throttle is
It is led to the shuttle valve 24 via 3. In the above state, when the pressure on the downstream side of the throttle, that is, the load pressure of the lift cylinder connected to the pilot switching valve 5 becomes equal to or higher than the set pressure of the relief valve 16, the compensator 2 performs load sensing on the lift cylinder. Demonstrate function. That is, the compensator valve 2 controls the differential pressure before and after the throttle determined by the opening degree of the pilot switching valve 5 to be constant. Therefore, a constant flow rate is supplied to the lift cylinder irrespective of the load fluctuation.

When the pilot switching valve 5 and the pilot switching valve 6 are simultaneously switched, the compensator valve 2 is controlled by the higher load pressure of the cylinders connected to the pilot switching valves 5 and 6. You. However, at this time, only the flow rate supplied to the priority flow path 4 is controlled, and the compensator valve 2 does not exert the load sensing function for the cylinders connected to the individual pilot switching valves 5 and 6. . If the load sensing function is to be exerted on the cylinders connected to the individual pilot switching valves 5 and 6, a compensator valve must be provided for each of the pilot switching valves 5 and 6.

A flow rate higher than the flow rate supplied to the priority flow path 4 is supplied to the surplus flow path 8 as a surplus flow rate. Therefore, the attachment cylinder not shown is
The operation is performed at the surplus flow rate supplied to the surplus flow path 8.

On the other hand, from the standby state, only the proportional electromagnetic pressure reducing valve 20a of the pilot switching valve 7 is excited,
When only the pilot switching valve 9 is switched, the pressure oil is supplied to the attachment actuator, and it operates. Then, in this case, the load pressure of the attachment actuator is generated in the surplus flow path 8. Since the priority flow port 3 and the surplus flow port 9 of the compensator valve 2 are actually in communication with each other, the load pressure generated in the surplus flow path 8 is applied to one pilot chamber 2 a of the compensator valve 2. Be guided. Then, the load pressure guided to the one pilot chamber 2a is:
When the discharge force becomes larger than the discharge force of the pump P in the standby state, the spool of the compensator valve 2 is further pushed to the left, and a full stroke state is set.

As described above, when the proportional electromagnetic pressure reducing valve 18a is excited to guide the pilot pressure to the pilot chamber 5a from the state where the spool of the compensator valve 2 is fully stroked leftward, the pilot switching valve 5 is switched. .
When the pilot switching valve 5 is switched in this manner, the priority flow path 4 communicates with a lift cylinder (not shown), a flow is generated in the priority flow path 4, and the pressure decreases. Therefore, the pressure in one pilot chamber 2a of the compensator valve 2 communicating with the priority flow path 4 also decreases.

When the pressure in one of the pilot chambers 2a decreases as described above, the spool of the compensator valve 2 moves from the full stroke in the left direction in the drawing to the right in the drawing. Therefore, the discharge oil of the pump P is divided into the priority flow path 4 side and the excess flow path 8 side according to the switching position of the compensator valve 2.

The pilot switching valves 5 to 7 are switched within a fixed pilot flow rate range determined by the flow control valve 12 and the fixed throttle 13. The pilot flow rate is determined based on a flow rate required to simultaneously switch any two of the pilot switching valves 5 to 7 at a predetermined speed. The reason for determining the pilot flow rate in this way will be described below.

In order to switch the pilot switching valves 5 to 7 at a predetermined speed, the pilot flow maintained at a predetermined pressure is supplied to the pilot chambers 5a to 7a, 5b to 7b of the pilot switching valves 5 to 7 by the spool. The amount must be supplied in proportion to the stroke amount. For example, when all the pilot switching valves 5 to 7 are simultaneously switched at a predetermined speed, a pilot flow amount to be supplied to three pilot chambers is required. However, it is rare that the operator operates three actuators at the same time, and switching the three switching valves 5 to 7 at the same time requires:
The fact is that there is little.

Further, in this conventional example, since the discharge oil of one pump P is divided and used for both the pilot and the actuator, if the discharge amount of the pump P is constant, the pilot flow rate Increases the flow rate for the actuator relatively decreases. Therefore, when the pilot flow rate is increased, there is a problem that the maximum operation speed of the actuator is reduced. Therefore, in this conventional device, in consideration of the actual use condition and the maximum operation speed of the actuator,
The pilot flow rate is set to a flow rate necessary for simultaneously changing any two of the pilot switching valves 5 to 7 at a predetermined speed.

[0019]

In the above conventional apparatus, the responsiveness of the compensator valve 2 is deteriorated depending on the operating state of the pilot switching valves 5 to 7, and as a result, the pressure in the supply flow path 1 is reduced. There is a problem that the responsiveness of the actuators connected to the pilot switching valves 5 to 7 is deteriorated. The problem of this conventional device will be described in detail below.

For example, as described above, by actuating the attachment actuator connected to the pilot switching valve 7, the pilot switching valve 7 is moved from the state where the spool of the compensator valve 2 is fully stroked leftward in the drawing. When the pilot switching valve 5 is switched back to neutral and the pilot switching valve 5 is switched, the pilot switching valve 7 is opened to connect the surplus flow path 8 and the tank T, and the pilot switching valve 5 is opened and the priority flow path 4 is not shown. Communicate with the lift cylinder. At this time, in the pilot switching valve 7, the pilot flow is sucked into the pilot chamber 7b by returning the spool to neutral, and in the pilot switching valve 5, the pilot flow is supplied to the pilot chamber 5a.

When the pilot switching valve 7 is opened and the excess flow path 8 communicates with the tank T while the spool of the compensator valve 2 is in the full stroke in the left direction in the drawing as described above, the compensator valve 2 , The pump P and the tank T are kept in communication. Therefore, the pump pressure instantaneously decreases, and the pressure in the supply flow path 4 also decreases. When the pressure in the priority flow path 4 decreases in this way, the pressure in one pilot chamber 2a of the compensator valve 2 also decreases. Therefore, the spool of the compensator valve 2 starts to move rightward in the figure, overcoming the thrust of the one pilot chamber 2a.

At this time, since the spool of the compensator valve 2 moves rightward from the position where the full stroke is leftward in the drawing, the stroke amount is large.
Since the pilot flow rate is proportional to the stroke amount, if the stroke amount is large, the other pilot chamber 2b
The flow rate supplied to the hopper also increases. However, as described above, the pilot flow rate is set to such a value that only two pilot switching valves are switched at the same time, so that the pilot chamber 5 of the two pilot switching valves 5 and 7 is used as described above.
When the pilot flow is supplied to a and 7b and also to the pilot chamber 2b of the compensator valve 2, the pilot flow tends to be short. Therefore, the pilot pressure decreases, and the spool of the compensator valve 2 cannot be pushed at a predetermined pressure.
Therefore, the switching response of the compensator valve 2 is deteriorated.

When the switching response of the compensator valve 2 is deteriorated as described above, the supply flow path 1 and the surplus flow path 8 are maintained in communication with each other.
Is connected to the tank T via the pilot switching valve 7, so that the pressure in the supply passage 1 drops rapidly. When the pressure in the supply passage 1 decreases in this way, the pressure in the branch passage 11 also decreases, and the relief valve 16 closes. If the relief valve 16 is closed, the pilot flow path 1
The pilot pressure of 7 also becomes lower than the set pressure of the relief valve 16, and the predetermined pilot pressure cannot be maintained. If the predetermined pilot pressure cannot be maintained, the switching response of the pilot switching valve 5 deteriorates, and there is a problem that an operation delay occurs in a lift cylinder (not shown) connected to the switching valve 5. .

An object of the present invention is to maintain the switching response of the pilot switching valve regardless of how the pilot switching valve is operated, and to use the pump discharge oil without waste. It is to provide a hydraulic control device.

[0025]

SUMMARY OF THE INVENTION The present invention provides a pump,
A supply flow path connected to the pump, and a compensator valve connected to the supply flow path and for distributing pump discharge oil to a priority flow path side and an excess flow path side, and a pilot switching valve connected to the priority flow path, A pilot switching valve connected to the surplus flow path, a branch flow path connected to the supply flow path, a throttle provided in the branch flow path, and a throttle provided on the upstream side of the throttle, and the differential pressure before and after the throttle is kept constant. A flow control valve to be maintained, a relief valve provided downstream of the throttle and generating a pilot pressure upstream thereof, and a pilot guiding the pilot pressure generated upstream of the relief valve to the pilot chamber of the pilot switching valve. And a flow path.

The compensator valve is premised on a hydraulic control device configured to guide the load pressure on the priority flow path side to one pilot chamber and to guide the pilot pressure to the other pilot chamber via the pilot flow path. And The present invention is characterized in that the pilot flow path is connected between a throttle and a flow control valve while assuming the above device.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus of the embodiment shown in FIG. 1 is characterized in that a pilot flow path 17 connected to a branch flow path 11 is located between a flow control valve 12 and a fixed throttle 13. Having. Also, this pilot flow path 17 is branched,
The compensator valve 2 is communicated with the other pilot chamber 2b, and a shuttle valve 24 is provided in the communication process. The shuttle valve 24 selects a high pressure between the load pressure and the pilot pressure. Since other configurations are the same as those of the above-described conventional example shown in FIG. 2, the same components are denoted by the same reference numerals, and detailed description thereof will be omitted.

According to the apparatus of the embodiment shown in FIG. 1, for example, the actuator of the attachment connected only to the pilot switching valve 7 is operated to move the spool of the compensator valve 2 to the full stroke in the leftward direction. If the pilot switching valve 7 is returned to neutral and the pilot switching valve 5 is switched in either direction at the same time,
A pilot flow is supplied to the pilot chambers of the pilot switching valves 5 and 7 and the other pilot chamber 2 b of the compensator valve 2 via the pilot flow path 17.

When the pilot flow is supplied to the plurality of pilot chambers as described above, the flow supplied to the relief valve 16 tends to decrease relatively. It exerts the function of keeping the differential pressure around 13 constant and increases its opening. Therefore, the flow rate passing through the flow control valve 12 increases, and the flow rate supplied downstream thereof also increases. Thus, the flow control valve 12
If the flow rate supplied to the downstream side of the valve increases, the relief valve 16
Maintain the relief state, and maintain the pressure on the upstream side at the set pressure of the relief valve 16. Therefore, the pressure in the pilot passage 17 is always kept at a predetermined pressure.

As described above, the pressure in the pilot passage 17 becomes
If the pressure is constantly maintained at a predetermined value, no response delay occurs in the pilot switching valves 5 and 7 and the compensator valve 2. Therefore, the operation delay of the actuator connected to the pilot switching valves 5 and 7 can be prevented. Since there is no response delay of the compensator valve 2, the pressure in the supply passage 1 does not decrease unlike the conventional example.

According to this embodiment, the relief valve 1
If a predetermined pilot pressure can be generated upstream of the fixed throttle 6, the flow rate supplied to the downstream side of the fixed throttle 13 can be reduced. That is, it suffices to supply a flow rate enough to cause the relief valve 16 to be relieved downstream of the fixed throttle 13. Therefore, the discharge flow rate of the relief valve 16 can be reduced. If the discharge flow rate of the relief valve 16 is small, the relief valve 16 can be downsized.

[0032]

According to the present invention, a pilot flow path is connected between the fixed throttle and the flow control valve, so that the pilot flow is supplied from the upstream side of the fixed throttle. As the pilot flow increases, the flow control valve opens accordingly to increase the flow through it. Therefore, the relief valve is always kept in a relief state. As described above, if the relief valve is always kept in the relief state, the pressure of the pilot flow path connected to the upstream side is always kept at the set pressure of the relief valve. Therefore, the switching response of the pilot switching valve and the compensator valve can be maintained, and the operation delay of the actuator connected to the pilot switching valve can be prevented.

Further, according to the present invention, it is sufficient to supply a flow rate enough to relieve the relief valve downstream of the fixed throttle. Therefore, the flow rate discharged through the relief valve can be reduced. If the discharge flow rate of the relief valve can be reduced in this way, the size of the relief valve can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Supply flow path 2 Compensator valve 2a One pilot chamber 2b The other pilot room 4 Priority flow path 5-7 Pilot switching valve 5a-7a, 5b-7b Pilot chamber 8 Excess flow path 11 Branch flow path 12 Flow control valve 13 Fixed Restrictor 16 Relief valve 17 Pilot flow path P pump

Claims (1)

[Claims] A pump, a supply flow path connected to the pump, a compensator valve connected to the supply flow path, and distributing oil discharged from the pump to a priority flow path side and an excess flow path side; The pilot switching valve connected to the, the pilot switching valve connected to the surplus flow path, the branch flow path connected to the supply flow path, the throttle provided in this branch flow path, and provided on the upstream side of the throttle, A flow control valve for maintaining the differential pressure before and after the throttle constant, a relief valve provided downstream of the throttle and generating a pilot pressure upstream thereof, and a pilot pressure generated upstream of the relief valve as the pilot pressure. A pilot flow path leading to a pilot chamber of the switching valve, wherein the compensator valve includes:
In the hydraulic control device configured to guide the load pressure on the priority flow path side to one of the pilot chambers and to guide the pilot pressure to the other pilot chamber via the pilot flow path, the pilot flow path is controlled by restricting and controlling the flow rate. A hydraulic control device connected between the valve and the valve.