JP2000283104A - Hydraulic controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic controller allowing miniaturization of a flow control valve. SOLUTION: This hydraulic controller has a first pump P1; a main flow valve Mv connected to the first pump P1; a control flow side circuit comprising one or more sub flow valves Sv connected to a control flow port 27 of the main flow valve Mv; an excessive flow circuit (a) connected to an excessive flow port 29 of the main flow valve Mv; and a second pump P2 for joining direct by pressure oil to the excessive flow port 29 side of the main flow valve Mv. A set flow rate in the control flow port 27 side of the main flow valve Mv is set to a total flow rate of maximum required flow rates of controlled objects connected to the control flow side circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydraulic control device used for a forklift or the like.

[0002]

2. Description of the Related Art An example of a hydraulic control device used for a forklift is shown in FIG. In the conventional hydraulic control device shown in FIG. 2, a first flow control valve 1 is connected to a first pump P1. The first flow control valve 1 has a control flow port 2 connected to a first control flow path 3, and the first control flow path 3 connected to a power steering device PS. A throttle 4 is provided in the first control flow path 3, a pressure downstream of the throttle 4 is guided to a first pilot chamber 1 a of the first flow control valve 1, and a pressure upstream of the throttle 4 is changed to a damper orifice. 5 to the second pilot chamber 1b. A first excess flow path 7 is connected to the excess flow port 6 of the first flow control valve 1, and the first excess flow path 7 is connected to the excess flow circuit a through a parallel flow path 19 and a neutral flow path 20. Connected to Note that the first flow control valve 1
A spring s1 is provided in the pilot chamber 1a, and the spring force acts on the spool.

The first flow control valve 1 maintains a position where the acting force of the pilot pressure in the first pilot chamber 1a and the spring force of the spring s1 and the acting force of the pilot pressure in the second pilot chamber 1b are balanced. Then, at this balanced position, the differential pressure across the throttle 4 is kept constant,
The flow rate through is kept constant. If the flow rate passing through the throttle 4 is kept constant in this way, a constant flow rate will always be supplied to the power steering device PS connected downstream thereof. The surplus flow not supplied to the power steering device PS is supplied from the surplus flow port 6 to the surplus flow circuit a via the first surplus flow path 7. That is, the first
The flow control valve 1 preferentially supplies a constant flow rate of the discharge oil of the first pump P1 to the power steering device PS, and supplies a surplus flow rate to the surplus flow circuit a.

[0004] Similarly to the above, the second pump P2 has a second pump P2.
A flow control valve 8 is connected, and a brake booster BB is connected to a control flow port 9 of the second flow control valve 8 via a second control flow path 10. Further, a second excess flow path 12 is connected to the excess flow port 11 of the second flow control valve 8, and the second excess flow path 12 joins the first excess flow path 7. Further, a throttle 13 is provided in the second control flow path 10, and a pressure downstream of the throttle 13 is guided to a first pilot chamber 8 a of a second flow control valve 8 provided with a spring s 2,
The pressure on the upstream side of the throttle 13 is guided to the second pilot chamber 8 b via the damper orifice 14. The second flow control valve 8 as described above gives priority to the brake booster BB for a constant flow rate of the discharge oil of the second pump P2.
To the excess flow circuit a.

That is, in this conventional apparatus, the surplus side of the first flow control valve 1 and the surplus side of the second flow control valve 8 are connected in parallel to the surplus flow circuit a, The total surplus flow rate of the flow control valves 1 and 8 is supplied to the surplus flow circuit a. The surplus flow circuit a includes first and second surplus flow paths 7 and 1
1 to 3 switching valves 15 to 15 connected in parallel to 2
17. These first to third switching valves 1
A lift cylinder, a tilt cylinder, and an attachment cylinder (not shown) are connected to 5 to 17, respectively. When one of the switching valves is switched by the lever, the excess flow derived from the first and second flow control valves 7 and 12 is supplied to the cylinder by an amount corresponding to the switching amount, and the cylinder operates.

A check valve 18 is provided upstream of the power steering device PS in the first excess flow path 3 to prevent the backflow of the pressure oil from the power steering device PS. The reason why the check valve 18 is provided will be described below. For example, when a large load is acting on a lift cylinder (not shown) of the surplus flow circuit a during the operation of the power steering device PS, the first flow control valve 1 opens the surplus flow port 6 greatly, , Control flow port 2
Squeeze. At this time, the first flow control valve 1 is in a state in which the control flow port 2 and the surplus flow port 6 are in communication. When the lift cylinder is returned to the neutral state from the above state and the neutral flow path 20 communicates with the tank t, the pump pressure rapidly decreases. This decrease in pump pressure is maintained until the excess flow port 6 of the first flow control valve 1 closes.

When the pump pressure decreases as described above, the pressure on the surplus flow port 6 side becomes lower than the pressure on the control flow port 2 connected to the power steering device PS. Therefore, the pressure oil on the power steering device PS side flows backward through the control flow port 2 to the surplus flow port 6 side. If the pressure oil on the side of the power steering device PS flows back in this way, problems such as an insufficient assist force occur. In order to solve such a problem, a check valve 18 is provided in the first control flow path 3 to prevent the backflow of the pressure oil from the power steering device PS. Reference numerals 21 and 22 in FIG.
Is a relief valve.

[0008] The conventional apparatus as described above, for example,
The maximum required flow rate of the power steering device PS is 20 l /
min, the maximum required flow rate of the brake booster BB is 5 l
/ Min, the maximum required flow rate on the surplus flow circuit side a is 175 l /
In the case of min, the first and second pumps P1 and P2 have a discharge rate of 100 l / min. By using the first and second pumps P1 and P2 having a discharge rate of 100 l / min, the first flow control valve 1
Is the value obtained by subtracting the flow rate supplied to the power steering device PS from the discharge rate of the first pump P1, that is, 100 l / min.
-20 l / min = 80 l / min. Also, the second
The surplus flow supplied to the surplus flow port 11 side of the flow control valve 8 is a value obtained by subtracting the flow supplied to the brake booster BB side from the discharge amount of the second pump P2, that is, 10
0 l / min-5 l / min = 95 l / min.

Therefore, the surplus flow circuit a has the first
The total of the surplus flow rate 80 l / min on the flow control valve 1 side and the surplus flow rate 95 l / min on the second flow control valve 8 side is 17
5 l / min will be supplied. By supplying the pressure oil of 175 l / min, which is the maximum necessary flow rate, to the excess flow circuit a in this manner, each cylinder on the excess flow circuit a side can be moved at a predetermined operating speed.

[0010]

The above-mentioned conventional device is a controlled object that must always supply a constant flow rate, such as a power steering device PS and a brake booster BB.
In the case where there are a plurality of components, a flow control valve and a pump are provided for each controlled object. The discharge amount of each pump is controlled by a flow control valve, so that a constant flow is always supplied to the control target side, and the remaining flow is supplied to another actuator.

However, as described above, the controlled object such as the power steering device PS or the brake booster BB which always requires a constant flow rate has a maximum required flow rate of 20 l.
/ Min or 5 l / min does not require much flow rate. On the other hand, the surplus flow circuit a that operates with the surplus flow includes:
In some cases, an actuator larger than the power steering device PS or the brake booster BB is provided and the large actuator is moved. In that case, since a large excess flow rate is required, the discharge amount of each pump must be increased. If the discharge amount of each pump is increased in this manner, the flow control valve must be correspondingly increased in size.

That is, in the conventional apparatus, when a large flow rate is required on the surplus flow circuit a side, the discharge amount of each pump must be increased. However, when the discharge amounts of the individual pumps are increased as described above, there is a problem that all the flow control valves are enlarged accordingly. An object of the present invention is to provide a hydraulic control device capable of reducing the size of a flow control valve.

[0013]

According to a first aspect of the present invention, there is provided a first pump, a main flow control valve connected to the first pump, and one or more sub-flow control units connected to a control flow port of the main flow control valve. A control flow side circuit comprising a valve, a surplus flow circuit connected to the surplus flow port of the main flow control valve, and a second pump for directly joining the pressure oil to the surplus flow port side of the main flow control valve. The set flow rate on the control flow port side of the main flow control valve is a total flow rate of the maximum required flow rate of the control target connected to the control flow side circuit. According to a second aspect of the present invention, the sub-flow control valve has an extra flow port connected to the power steering device, the control flow port connected to another actuator, and a restrictor provided downstream of the control flow port. The pressure on the downstream side is guided to one pilot chamber of a sub flow control valve provided with a spring, and the pressure on the upstream side of the throttle is guided to the other pilot chamber of the sub flow control valve. .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment shown in FIG. 1, a main flow control valve Mv is connected to a first pump P1, and a control flow port 23 thereof is connected to a sub flow control valve via a first control flow path 24. It is connected to the Sv inflow port 25. The surplus flow port 26 of the main flow control valve Mv is connected to the surplus flow circuit a via the first surplus flow path 7. The constant flow rate of the discharge oil of the first pump P1 is always supplied to the sub flow rate control valve Sv by the main flow rate control valve Mv,
The surplus flow rate is supplied to the surplus flow circuit a side.
Further, a brake booster BB is connected to the control flow port 27 of the sub flow control valve Sv via a second control flow path 28, and the power steering device is connected to the surplus flow port 29 via a second surplus flow path 30. PS is connected. And
The main flow control valve M is controlled by the sub flow control valve Sv.
Of the pressure oil derived from v, a constant flow is always supplied to the brake booster BB side, and an excess flow is supplied to the power steering device PS.

Further, the second excess flow path 7 is provided with a second
The pump P2 is directly joined, and the discharge oil of the second pump P2 is directly supplied to the surplus flow circuit a. In this embodiment, the check valve 18 provided on the upstream side of the power steering device PS in the conventional example is unnecessary. Reference numerals 31 and 32 denote apertures, and reference numerals 33 and 34 denote damper orifices. Reference numerals 35a, 35b
Denotes first and second pilot chambers of the main flow control valve Mv, and reference numeral 37 denotes a spring. Further, reference numeral 36a
Is a first pilot chamber corresponding to one pilot chamber of the present invention, and reference numeral 36b is a second pilot chamber corresponding to the other pilot chamber of the present invention. Reference numeral 38 denotes a spring. Since the surplus flow circuit a and the relief valves 21 and 22 are the same as those in the conventional example, the same components are denoted by the same reference numerals and detailed description thereof will be omitted.

In the embodiment described above, for example, the maximum required flow rate of the power steering device PS is 20 l / min, the maximum required flow rate of the brake booster BB is 5 l / min, and the excess flow circuit a When the maximum required flow rate is 175 l / min and the discharge rates of the first and second pumps P1 and P2 are respectively 100 l / min, the set flow rate of the main flow control valve Mv to the control flow port 23 side is determined by the power steering apparatus PS. Maximum required flow rate 20 l / mi
n and a maximum required flow rate of the brake booster of 5 l / min, that is, a total flow rate, that is, 25 l / min.
Therefore, the surplus flow port 26 of the main flow control valve Mv
The flow rate obtained by subtracting the flow rate supplied to the control flow port 23 side from the discharge rate of the first pump P1, ie, 100 l
/ Min-25 l / min = 75 l / min of pressure oil is supplied.

25 l / min from the main flow control valve Mv
Is supplied to the sub flow control valve Sv, the inflow amount of which is smaller than the inflow amount supplied to the second flow control valve of the conventional example, that is, 100 l / min. Therefore, in this embodiment, the sub flow control valve can be made smaller than the conventional second flow control valve. And the sub flow control valve S
v is set to 5 l / min, which is the maximum required flow rate of the brake booster BB, and the remaining flow rate of 20 l / min is set to the excess flow port 29 side.
That is, the maximum required flow rate of the power steering device PS is supplied. In this way, the brake booster BB
The maximum required flow is always supplied to both the power steering device PS and the power steering device PS.

On the other hand, a flow rate of 100 l / min is merged from the second pump P2 into the first surplus flow path 7 to which a flow rate of 75 l / min is supplied from the surplus flow port 26 of the main flow control valve Mv. Therefore, a flow rate of 175 l / min, which is the maximum required flow rate, is supplied to the surplus flow circuit a. Therefore, each cylinder on the surplus flow circuit a side can be moved at a predetermined speed.

According to the above embodiment, the sub flow control valve Sv
Required by the vehicle, that is, the power steering device P
The total maximum required flow of S and brake booster BB
It is supplied from the control flow port 23 of the main flow control valve Mv. Therefore, the flow rate supplied to the sub flow rate control valve Sv can be made smaller than the flow rate supplied to the second flow rate control valve of the conventional example. Therefore, the sub flow control valve Sv can be made smaller than the conventional second flow control valve.

In this embodiment, the sub flow control valve S
Although v functions as the check valve 18 of the conventional example, the principle is as follows. That is, when the check valve 18 is required, the power steering device P
During the operation of S, the control flow port 2 of the main flow control valve Mv
3 is a case where it communicates with the tank via the surplus flow port 26, as has been made clear in the conventional explanation.
As described above, the control flow port 23 of the main flow control valve Mv
Communicates with the tank via the surplus flow port 26, the pressure oil on the brake booster BB side slightly flows backward. If the pressure oil of the brake booster BB flows backward even a little, the throttle 32
The pressure difference before and after is reversed, or the pressure difference becomes almost zero.

When the differential pressure is reversed as described above, the pressure in the first pilot chamber 36a of the sub flow control valve Sv becomes higher than the pressure in the second pilot chamber 36b. Therefore, the pressure in the first pilot chamber 36a and the spring force of the spring 38 are switched to switch the sub flow control valve Sv, and the surplus flow port 29 is completely closed. Even if the differential pressure becomes zero, the sub flow control valve Sv is switched in the same manner as described above by the spring force of the spring 38 set on the first pilot chamber 36a side, and the excess flow port 29 is completely removed. close.

Since the excess flow port 29 is completely closed in this way, the pressure oil on the power steering device PS side
The return to the tank via the main flow control valve Mv is eliminated. As described above, the pressure oil on the brake booster BB side may be slightly returned to the tank side, but its flow rate is very small and does not impair the brake function. As described above, in this embodiment,
Since the sub flow control valve Sv functions as a check valve for the power steering device PS, there is no need to provide a special check valve. The cost of parts can be reduced accordingly.

On the other hand, in this embodiment, the sub flow control valve S
Although the brake booster BB is connected to the control flow port 27 of v, a further sub flow rate control valve may be connected instead. In that case, the set flow rate on the control flow port 27 side of the upstream side sub flow rate control valve Sv is the total maximum required flow rate of the control object connected to the downstream side sub flow rate control valve. Also, the control flow port 23 of the main flow control valve Mv
The set flow rate on the side is the total flow rate of the maximum required flow rates of the control objects connected to these two sub flow rate control valves. According to the above, the size of the upstream side sub flow rate control valve Sv can be reduced, and the size of the downstream side sub flow rate control valve can also be reduced. That is, in this embodiment, when another sub-flow control valve is connected in series to the control flow port side of the sub-flow control valve one after another to form a control flow side circuit, the sub flow control connected to the downstream side is formed. The valve can be smaller than the upstream sub-flow control valve.

[0024]

According to the first aspect of the present invention, the control flow rate of the control flow port side of the main flow control valve is set to the total flow rate of the maximum required flow rate of the control object connected to the control flow side circuit. The flow rate supplied to the sub flow rate control valve that constitutes the side circuit can be reduced. Since the supply flow rate to the sub flow rate control valve can be reduced in this way, it can be reduced in size.

According to the second invention, the sub flow control valve is
When the pressure oil flows backward from the control flow port side, the excess flow port is shut off. Therefore, backflow of pressure oil from the power steering device connected to the surplus flow port side can be prevented. As described above, since the sub-flow control valve exerts the function of a check valve for the power steering device, there is no need to provide a special check valve. Accordingly, the cost of parts can be reduced accordingly.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment.

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

[Explanation of symbols]

a Excess flow circuit P1 First pump P2 Second pump PS Power steering device Mv Main flow control valve Sv Sub flow control valve 23, 27 Control flow port 26, 29 Excess flow port 32 Restrictor 36a Equivalent to one pilot chamber of the present invention A first pilot chamber 36b which corresponds to the other pilot chamber of the present invention.

Claims (2)

[Claims] A control flow side circuit comprising a first pump, a main flow control valve connected to the first pump, and one or more sub flow control valves connected to a control flow port of the main flow control valve; A surplus flow circuit connected to the surplus flow port of the flow control valve, and a second pump for directly joining the pressurized oil to the surplus flow port of the main flow control valve, wherein the setting of the control flow port side of the main flow control valve is provided. The hydraulic control device is characterized in that the flow rate is a total flow rate of a maximum required flow rate of a control object connected to a control flow side circuit. 2. The sub-flow control valve has a surplus flow port connected to the power steering device, a control flow port connected to another actuator, and a restrictor provided downstream of the control flow port. The pressure on the downstream side is led to one pilot chamber of the sub flow control valve provided with a spring,
2. The hydraulic control device according to claim 1, wherein the pressure upstream of the throttle is guided to the other pilot chamber of the sub flow control valve.