JP2001280302A - Hydraulic control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size of a variable discharge pump for load sensing control and reduce the cost of a whole circuit. SOLUTION: An engine ENG as a driving source is provided with the variable discharge pump P1 and a constant discharge pump P2 having the same shaft. A supply passage 1 for the variable discharge pump P1 and a supply passage 20 for the constant discharge pump P2 are combined at a combination point 22 to form a combined flow passage 24. The variable discharge pump P1 and the constant discharge pump P2 are connected to change valves 2, 3 via the combined flow passage 24. The variable discharge pump P1 is controlled to decrease in discharge amount when an actuator requires a less flow rate and to increase in discharge amount when it requires a more flow rate, while a constant flow rate is always supplied from the constant discharge pump P2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to load sensing control of a hydraulic control circuit.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional hydraulic control circuit. In this conventional hydraulic control circuit, switching valves 2 and 3 are connected via a supply path 1 to a variable discharge pump P1 driven by an engine ENG. Note that check valves 4 and 5 are provided upstream of the switching valves 2 and 3, respectively. The switching valves 2 and 3 are manually switched by levers 6 and 7, an actuator (not shown) is connected, and pressure oil is supplied to the actuator by switching the switching valves 2 and 3.

The switching valves 2 and 3 are provided with load pressure ports 2a and 3a for taking out the load pressure of the actuator. These load pressure ports 2a, 3a communicate with the tank T when the switching valves 2, 3 are in the neutral position. When the switching valves 2 and 3 are switched, pressure oil is supplied to the actuators, and the load pressure of each actuator is changed to the load pressure lines 8 and 9 via the load pressure ports 2a and 3a.
It is led to. The pressure guided to the load pressure lines 8 and 9 is selected to be high pressure by the shuttle valve 10, and is guided to the maximum load pressure line 11 as the maximum load pressure.

The load pressure of the highest load pressure line 11 selected at a high pressure is guided to a regulator mechanism 12 for controlling the tilt angle of the variable discharge pump P1. The regulator mechanism 12 is a load sensing control mechanism that controls the tilt angle of the variable discharge pump P1 based on the differential pressure between the maximum load pressure guided by the maximum load pressure line 11 and the discharge pressure. The regulator mechanism 12 includes the regulator valve 1
3. It is composed of a safety valve 14 and a regulator cylinder 15.

[0005] One of the pilot chambers 13a of the regulator valve 13 is connected to the maximum load pressure line 11 to guide the maximum load pressure of the actuator. The supply path 1 is connected to the other pilot chamber 13b, and discharge pressure from the variable discharge pump P1 is guided. The discharge pressure is set to be higher than the load pressure by the amount of the spring force of the spring 16.

For example, when the discharge pressure is lower than the set pressure, the regulator valve 13 switches to the left side in FIG.
4 to the tank T. When the pressure chamber 17 communicates with the tank, the pressure in the pressure chamber 17 decreases, so that the spring 18 expands, the tilt angle of the variable discharge pump P1 is kept large, and the discharge amount increases. On the other hand, when the discharge pressure becomes higher than the set pressure, the regulator valve 13 switches to the right side in FIG. 3 and guides the discharge pressure of the supply passage 1 to the pressure chamber 17 of the regulator cylinder 15 via the safety valve 14. . When the discharge pressure is guided to the pressure chamber 17, the pressure in the pressure chamber 17 increases, so that the spring 18 contracts and the tilt angle of the variable discharge pump P1 is reduced, thereby reducing the discharge amount.

The safety valve 14 is in a normal state maintained by a spring 19 and the regulator valve 13
And the pressure chamber 17 of the regulator cylinder 15. Therefore, in a normal state, the control pressure generated by the regulator valve 13 is controlled by the regulator cylinder 1
5 pressure chamber 17. However, when the discharge pressure of the variable discharge pump P1 becomes abnormally high, the safety valve 14 is switched against the spring 19 so that the discharge pressure of the variable discharge pump P1 is
To the pressure chamber 15a. Therefore, the regulator cylinder 15 operates against the spring 18, and the tilt angle of the variable discharge pump P1 can be reduced to prevent the discharge pressure from further increasing.

In such a hydraulic control circuit, the variable discharge pump P1 does not completely reduce the discharge amount to zero even when the switching valves 2 and 3 are in the neutral state, that is, when the device is not operated. This is because there is a meaning of a countermeasure against an oil leak, and furthermore, when the valve is actually operated, a small amount of oil is supplied in consideration of a time loss until the oil reaches the entire circuit. Further, even when the switching valves 2 and 3 are switched, that is, when the actuator is used, it is not always necessary to control the flow rate of all the oils required for operating the actuator. For example, when the required flow rate of the actuator is small, the flow rate control is not usually performed.

[0009]

As described above, the capacity of the variable discharge pump includes not only those requiring actual flow control but also those not requiring bleed-off and flow control. In. Since the running cost of the variable discharge pump is high, discharging the oil from the variable discharge pump even to an oil amount that does not require flow control as described above causes an increase in the cost of the entire hydraulic circuit. In particular, in order to cope with the required flow rate when the switching valve is switched, the variable discharge pump P1 necessarily becomes large, and there is a problem that the running cost of the large variable discharge pump P1 becomes extremely high.

When the switching valve is in the neutral position,
The discharge amount of the variable discharge pump is controlled to be small, but this amount is sometimes too small to reach the bleed-off amount. Further, the switching of the switching valve is manually performed by an operator using a lever directly connected to the switching valve. Therefore, when the load pressure is large, the lever is heavy,
Switching requires great power.

An object of the present invention is to use a constant discharge pump in addition to a variable discharge pump to discharge an oil amount that does not require flow rate restriction from the constant discharge pump, thereby reducing the capacity and the cost. An object of the present invention is to provide a hydraulic control device that can use a variable discharge pump. Another object of the present invention is to provide a hydraulic control device that allows an operator to perform switching with a small force by performing switching of the switching valve by electronic control.

[0012]

A hydraulic control circuit according to a first aspect of the present invention includes a variable discharge pump connected to a drive source, a switching valve connected to the variable discharge pump via a supply path, and a differential pressure across the switching valve. With a regulator device to adjust the
The regulator device is composed of a control valve and a control cylinder, and transmits the differential pressure across the switching valve led to the control valve to the control cylinder. The control cylinder controls the tilt angle of the variable discharge pump. A constant discharge pump is connected to the discharge pump, and the total flow rate of the variable discharge pump and the constant discharge pump is supplied to the switching valve. The hydraulic control circuit according to the second aspect of the invention is based on the premise of the first aspect, in which a solenoid portion is provided in the switching valve, and a pilot flow path is provided through a pressure reducing valve in a flow path branched from the supply path. The switching valve is switched by being adjusted by a solenoid unit.

[0013]

FIG. 1 shows a first embodiment of the present invention. The same reference numerals are used for the same components as in the conventional example. In addition, a detailed description of this similar configuration will be omitted. The hydraulic control circuit according to the first embodiment is characterized in that a variable discharge pump P1 and a constant discharge pump P2 separately from this are connected to an engine ENG as a drive source. The variable discharge pump P1 has a smaller capacity and a smaller size than a conventional variable discharge pump.

The variable discharge pump P1 and the constant discharge pump P
2 means that it is driven by the same drive shaft of the engine ENG,
It is connected in parallel to the engine ENG. The constant discharge pump P2 is connected to the switching valves 2 and 3 through the supply path 20.
And the supply path 20 joins the supply path 1 at the junction 22 via the check valve 21 to form a junction flow path 24.

Now, it is assumed that the switching valves 2 and 3 are at the neutral position shown in FIG. The load pressure port 2a of the switching valve 2 and the load pressure port 3a of the switching valve 3 communicate with the tank T. When these load pressure ports 2a, 3a communicate with the tank T,
The load pressure lines 8 and 9 become the tank pressure, and the tank pressure is led to the pilot chamber 13 a of the regulator valve 13.

A discharge pressure is guided to the other pilot chamber 13b of the regulator valve 13. When the discharge pressure becomes larger than the spring force of the spring 16, the regulator valve 13 switches to the right side in FIG. When the regulator valve 13 is switched to the right side, the discharge pressure is reduced to the safety valve 14.
Through the pressure chamber 17 of the regulator cylinder 15. When the discharge pressure is led to the pressure chamber 17, the spring 18 of the regulator cylinder 15 contracts, and the tilt angle of the variable discharge pump P1 is kept small.
Discharge amount from the nozzle. Thus, in the regulator mechanism 12, when the required flow rate of the actuator is small, the discharge amount of the variable discharge pump P1 is reduced to reduce the pressure loss.

On the other hand, since the constant discharge pump P2 is not controlled like the variable discharge pump P1, the engine E
A constant flow rate corresponding to the number of rotations of NG is discharged. Since the check valve 21 is provided in the supply path 20 of the constant discharge pump P2, the supply flow rate from the variable discharge pump P1 does not flow back to the constant discharge pump P2. Thus, according to the first embodiment, a constant flow rate is ensured in the circuit, no matter how small the discharge amount from the variable discharge pump P1 is. Therefore, the amount of bleed-off when the switching valves 2 and 3 are neutralized can be sufficiently maintained, so that the switching valves 2 and 3
At the same time, pressure oil is immediately supplied to the actuator.

Next, it is assumed that the switching valves 2 and 3 are switched to the switching position. When switching to the switching position, the amount of oil is supplied to the actuator, so that the load pressure rises in the pilot chamber 2a of the switching valve 2 and the pilot chamber 3a of the switching valve 3. This load pressure is led to the load pressure lines 8 and 9, the high pressure is selected by the shuttle valve 10, and is led to the highest load pressure line 11. The selected high-pressure load pressure is guided to one pilot chamber 13 a of the regulator valve 13 via the highest load pressure line 11.

A load pressure guided to the pilot chamber 13a;
When the sum of the spring force of the spring 16 and the other pilot chamber 13b becomes larger than that of the other pilot chamber 13b, the regulator valve 13 switches to the position on the left side in FIG. When the regulator valve 13 is at the left position in FIG. 1, the pressure chamber 17 of the regulator cylinder 15 communicates with the tank T via the safety valve 14. When the pressure chamber 17 reaches the tank pressure,
The spring 18 extends to increase the tilt angle of the variable discharge pump P1 to increase the discharge amount.

On the other hand, a constant flow is constantly supplied from the constant discharge pump P2. The supply path 1 of the variable discharge pump P1 and the supply path 20 of the constant discharge pump P2 join at a junction 22. That is, the total discharge amount of both pumps P1 and P2 is supplied to the switching valves 2 and 3. Therefore, even if the variable discharge pump P1 having a smaller capacity than the conventional one is used,
There is no shortage of the flow rate supplied to the actuator.

According to the first embodiment, the cost of the entire circuit can be reduced by changing the conventional large variable discharge pump to the small variable discharge pump P1. If two pumps are provided, the cost will increase. However, since the constant discharge pump is much cheaper than the variable discharge pump, if the price of the variable discharge pump can be suppressed, adding one constant discharge pump leads to a reduction in the overall cost. The variable discharge pump P
Since the constant discharge pump P2 is provided at the same time as 1, the bleed-off amount can be covered, and when the load increases, a sufficient amount can be supplied to the actuator.

The second embodiment shown in FIG. 2 is characterized in that the switching of the switching valve is performed by electronic control. The same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof will be omitted. This second
In this embodiment, the variable discharge pump P1 and the constant discharge pump P2 are connected to the same drive shaft of the engine ENG, and the respective supply paths 1 and 20 are merged at a merge point 22 to the merge flow path 24. Lead. And, through this merging channel 24,
Three switching valves 25, 2, 3 are connected. These switching valves 25, 2, 3 have solenoids 26, 27,
28 are provided.

Further, the pressure reducing valve 2 is
9, the combined discharge pressure is reduced, and the pilot flow path 3
3, the power is supplied to the solenoid units 26, 27, and 28. The pilot pressure supplied through the pilot flow path 33 is adjusted by the solenoids 26, 27, and 28 to switch the switching valves 25, 2, and 3.

The switching valves 2 and 3 have load pressure ports 2a and 3a, respectively.
Is provided, and the load pressure of the actuator is guided to the load pressure lines 8 and 9 via the load pressure ports 2a and 3a. The load pressure lines 8 and 9 are connected to a load pressure line 30 via a shuttle valve 10. Further, the pressure of the load pressure port 25 a of the switching valve 25 is led to the load pressure line 31. The load pressure line 31 joins with the load pressure line 30 via a shuttle valve 32, and the shuttle valve 32
Is selected at high pressure. The high pressure selected is the switching valve 2
As the maximum load pressure of 5, 2, and 3, the maximum load pressure line 11
It is led to.

The maximum load pressure is determined by the regulator mechanism 12
The discharge pressure of the variable discharge pump P1 is controlled such that the discharge pressure becomes higher than the load pressure by the set pressure. That is, the discharge pressure guided to the other pilot chamber 13b of the regulator valve 13 is reduced to the one pilot chamber 13a.
When the spring force is larger than the spring force of the spring 16, the regulator valve 13 is switched to the right side in FIG.
To introduce pressure. With this pressure, the spring 18 is contracted to reduce the discharge amount of the variable discharge pump P1.

Incidentally, such a state is caused by the switching valve 25,
2, 3 are in the neutral position or when the load is small and the required flow rate of the actuator is small. Thus, the variable discharge pump P1 is controlled, but the constant discharge pump P1 is controlled.
2 is not controlled, so that a constant flow can be supplied to the circuit. Therefore, even if the flow rate supplied from the variable discharge pump P1 decreases, the flow rate of the entire circuit does not become insufficient.

On the other hand, when the switching valves 25, 2, and 3 are switched to the switching position and the required flow rate of the actuator increases, the maximum load pressure guided to the pilot chamber 13a increases. Switch to the left side. When the regulator valve switches to the left,
The pressure chamber 17 and the tank T communicate with each other via the safety valve 14 and the regulator valve 13. When the pressure chamber 17 and the tank T communicate with each other, the spring 18 expands and the discharge amount of the variable discharge pump P1 increases. Thus, when the required flow rate from the actuator is large, the variable discharge pump P1
Is increased, and is combined with the discharge amount from the constant discharge pump P2 and supplied to the actuator.

Therefore, even if the small variable discharge pump P1 is used, the flow rate does not become insufficient, and a sufficient flow rate can be supplied to the actuator. Further, in the second embodiment, since the switching of the switching valves 25, 2, and 3 is performed by electronic control, precise control is possible, and a strong force is not required for switching. In the first embodiment, two switching valves are used, and in the second embodiment, three switching valves are used. However, in the present invention, any number of switching valves may be used.

[0029]

According to the first aspect of the present invention, since the variable discharge pump and the constant discharge pump are used in combination, the amount of oil that does not require flow control is supplied from the constant discharge pump, and the amount of oil that really requires flow control is controlled. Since it is sufficient to supply only the amount by the variable discharge pump, an inexpensive variable discharge pump having a small capacity can be used. Therefore, the cost of the entire circuit can be reduced. According to the second aspect of the invention, since the switching of the switching valve is performed by electronic control, a large force is not required unlike when switching is directly performed by a lever, and the switching can be easily performed, and more precise control can be performed.

[Brief description of the drawings]

FIG. 1 is a hydraulic control circuit diagram of a first embodiment.

FIG. 2 is a hydraulic control circuit diagram of a second embodiment.

FIG. 3 is a conventional hydraulic control circuit diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Supply path 2 Switching valve 3 Switching valve 12 Regulator mechanism 13 Regulator valve 15 Regulator cylinder 25 Switching valve 26 Solenoid part 27 Solenoid part 28 Solenoid part 29 Pressure reducing valve 33 Pilot flow path P1 Variable discharge pump P2 Constant discharge pump ENG Engine

Claims (2)

[Claims] 1. A variable discharge pump connected to a drive source, a switching valve connected to the variable discharge pump via a supply path, and a regulator mechanism, wherein the regulator mechanism includes a regulator valve and a regulator cylinder. In the hydraulic control circuit that transmits the differential pressure before and after the guided switching valve to the regulator cylinder, and the regulator cylinder controls the tilt angle of the variable discharge pump, a constant discharge pump is connected to the variable discharge pump. A hydraulic control circuit configured to supply a total flow rate with a constant discharge pump to the switching valve. 2. A switching valve is provided with a solenoid section, a pilot flow path is provided through a pressure reducing valve in a flow path diverted from the supply path, and the pilot pressure is adjusted by the solenoid section to switch the switching valve. Claim 1
The described hydraulic control circuit.