JPS5916123B2 - hydraulic control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a hydraulic circuit, particularly a hydraulic control device used in a working device of a construction machine such as a motor grader.

A hydraulic circuit used in a working device of construction machinery such as a motor grader has a control valve 1 as shown in Figure 1.
In the neutral state (when the actuator 2 is not operated), the pressure oil from the hydraulic pump 3 returns to the oil tank 4 as it is, forming a pent unload circuit.

This is an effective method because it suppresses the hydraulic pressure generated in neutral to a low pressure caused only by piping resistance and reduces power loss.

In such a hydraulic circuit, when an electro-hydraulic servo valve is used, such as in an automatic earth removal plate control device, the servo valve requires a constant hydraulic pressure supply source even when in neutral. could not be used.

By the way, as a method of supplying a constant hydraulic pressure even when the vehicle is in neutral, the following method, which is used in machine tools, etc., can be considered.

(1) Block the vent circuit of the pent unload circuit and relieve excess flow with the relief valve.

(11) A pressure-controlled variable discharge pump is used as the hydraulic pump.

However, these have the following drawbacks.

In the method (1), since the power loss is large, the temperature of the oil increases rapidly and an oil cooler is required.

In the method (11), compared to the gear pump that is generally used for pressure-controlled variable discharge pump construction machinery,
The structure is complex and expensive.

The present invention does not have the above-mentioned drawbacks, has low power loss and low heat generation, and is capable of providing at low cost a constant hydraulic power source that is suitable for construction machinery and supplies the necessary flow rate to working equipment using servo valves. This was proposed for the purpose of providing a hydraulic circuit, and in addition to the main pump normally used for the working equipment of construction machinery, it can also supply the servo valve leakage flow that occurs when the servo valve is in neutral, even when the engine is running at low speed. A second small-sized pump has been newly installed, and during normal operation (when the servo valve is not used), the pressure oil from the main pump is guided to the normal control valve, and the pressure oil from the second pump is routed to the normal control valve. It is returned to the oil tank and unloaded, and when the automatic control device is activated (when using a servo valve), the pressure oil from the second pump is relieved by the relief valve to obtain a constant oil pressure, and the servo is used when the actuator operates rapidly. The present invention is characterized in that when the valve requires a large flow rate, an unload relief valve is provided in the hydraulic circuit so that the insufficient amount can be supplied from the first pump.

An embodiment of the present invention will be explained in detail below with reference to FIGS. 2 to 4.

In FIG. 2, the engine 5 includes a first hydraulic pump (main hydraulic pump) 6 and a second hydraulic pump (auxiliary hydraulic pump) 7.
It is designed to drive.

The main hydraulic pump 6 corresponds to the hydraulic pump 3 in FIG. 1, and is capable of supplying sufficient power to operate the actuator 8 of the working device.

On the other hand, the auxiliary hydraulic pump 7 is small enough to ensure the neutral leakage flow rate of the servo valve 9 and the leakage flow rate of the unload IJ-F valve 10 even when the engine is rotating at low speed.

This auxiliary hydraulic pump 7 is preferably driven by a V-belt so that it can be added even after the construction machine is completed.

Suction ports of the main hydraulic pump 6 and the auxiliary hydraulic pump 7 are each connected to a hydraulic tank 11, so that oil can be sucked in when the engine 5 rotates.

The discharge port of the main hydraulic pump 6 is the unload IJ IJ
- is connected to the first input port 12 of the valve 10, and the discharge port of the auxiliary hydraulic pump 7 is connected to the second input port 13.

The first output port 14 of the unload relief valve 10 is
It is connected to the pressure port 16 of the control valve 15, and the second output port 17 is connected to the filter 180 input port.

Drain port 19 is connected to hydraulic tank 11.

A vent port 20 and a tank port 21 of the control valve 15 are connected to the hydraulic tank 11.

Furthermore, two control ports (22, 22') are connected to the actuator 8.

A relief valve 23 is connected to an oil passage between the first output port 14 of the unload relief valve 10 and the pressure port 16 of the control valve 15.

The output port of the filter 18 is the pressure port 2 of the servo valve 9.
4, and the tank port 25 of the servo valve 9 is connected to the hydraulic tank 11.

Furthermore, two control ports (26, 26') are connected to an actuator 27.

Here, the control valve 15 after the first output port 14 of the unload relief valve 10, the actuator 8
, the hydraulic circuit consisting of the relief valve 23 is shown in FIG.
It has a hydraulic circuit similar to the pent unload circuit,
A first hydraulic circuit is formed.

Also, the second output port 17 of the and load relief valve 10, the filter 18, the actuator 27, the servo valve 9
The hydraulic circuit consisting of the above forms a second hydraulic circuit.

In FIGS. 3 and 4, the unload relief valve 10
Inside the valve body 31 are two spools 32 and 33.
There is.

The first spool 32 constitutes the unload valve 71 together with the spring 35, and is inserted into the first stepped hole 34 of the valve body 31 and is pressed against the shoulder part by the spring 35. 1st spool 3
2 closes off the space between the oil passage 36 connected to the first input port 12 and the oil passage 37 connected to the first output port 14 by its land portion.

The shoulder side of the first spool 32 is connected to an oil passage 38 connected to the second output port 17 through an orifice 39 .

The second spool 33 constitutes a pilot relief valve 72 together with the spring 41, is inserted into the second stepped hole 40 of the valve body 31, and is pressed against a shoulder portion thereof by the spring 41.

A cavity 42 is provided at the end of the spool 33 on the shoulder side, and is connected to an oil passage 43 that continues to the second input port 13 .

The cavity 42 is also connected to an outer peripheral groove 44 of the spool 33.

The spool 33 is normally pushed by a spring 41 into a circumferential groove 44 and an oil passage 45 connected to the drain port 19.
The land section closes off the area between the two.

The spool 33 also has an orifice 46 that connects the cavity 42 and the cavity 47 into which the spring 41 is inserted.

Note that the spools 32 and 33 move to the left when the pushing force to the left due to the difference in pressure acting on the left and right end faces exceeds the spring pushing force, but the spool 32 moves to the left.
It is possible to move with a smaller pressure difference than the 3rd one.

A first check valve 48 is located between the oil passages 36 and 38, and the check valve 48 allows oil to flow only from the oil passages 36 to 38 by means of a spring 49.

Further, there is a second check valve 50 between the oil passages 43 and 38, and the check valve 50 is connected to the oil passage 4 by a spring 51.
Only oil flow from 3 to 38 is allowed.

The first and second spool 32° 330 spring side cavities 52, 47 are connected to an oil passage 53.

A relief valve body 54 is located on the left side of the valve body 31.
is fixed.

IJ IJ-Full valve body 54 has an oil passage 55 connected to oil passage 53 .

The relief valve body 54 also has a stepped hole 56 which is connected to the tank port 19 by an oil passage 57.

The stepped hole 56 has an oil passage connected to the oil passage 55, and the stepped portion has a conical valve 58, which is operated by a spring 59.
Normally, the space between the oil passage 55 and the stepped hole 56 is closed.

These constitute a relief valve 73, and when the pressure in the oil passage 55 rises above a certain set pressure, the conical valve is pushed back by the pressure, so that the oil passage 55 and the stepped hole 56 communicate with each other. It has become.

Plug 60 holds spring 59.

Further, a solenoid valve 61 is attached to the relief valve body 54, and a needle 62 of the solenoid valve 61 is connected to the solenoid valve 61.
1 is not energized, it is pushed up by the spring 63 and the oil passages 55 and 64 are pushed up as shown in the figure.
I am communicating with you.

Further, when the electromagnetic valve 61 is energized, the needle 62 lies in the oil passage 64 according to the spring 63, and the tapered portion thereof closes the space between the oil passages 55 and 64.

Note that the oil passage 64 passes through the stepped hole 56 and connects to the tank port 19.
contact.

Also, the relief valve body 54 has springs 35, 41
It also supports 0.

There is a cover 65 on the right side of the valve body 31, and the cover 65 has the second output port 17 and the oil passage 38, and also serves to support the springs 49 and 510.

One embodiment of the present invention is constructed as described above.
A case in which only the servo valve 5 is operated and the servo valve 9 is not used) will be explained.

At that time, the servo valve 9 and the solenoid valve 61 are not energized.

Since the electromagnetic valve 61 is not energized, the needle 62 is pushed up by the spring 63 and communicates between the oil passages 55 and 64. Therefore, the oil in the spring-side cavities 52, 47 of the spools 32, 33 is discharged. There is.

When the engine rotates, pressure oil is sent out from the discharge ports of the main hydraulic pump 6 and the auxiliary hydraulic pump 7, and reaches the inlet ports N2 and 13 of the unload relief valve 10, respectively.

Among these, the pressure oil from the auxiliary hydraulic pump 7 is passed through the oil passage 43 from the cavity 42 to the orifice 46 of the spool 33.
At this time, a pressure drop occurs, so the hydraulic pressure in the cavity 42 becomes higher than that in the cavity 47.

When this pressure exceeds a certain level, the spool 33 overcomes the spring pushing force and moves to the left, leading the pressure oil in the oil passage 43 to the oil passage 45 through the circumferential groove 44 of the cavity 42 and draining it into the hydraulic tank 11.

Therefore, the hydraulic pressure of the pressure oil from the auxiliary hydraulic pump 7 is kept low, resulting in an unloaded state.

The pressure oil from the main hydraulic pump 6 that has reached the first input port 12 pushes up the check valve 48 through the oil passage 36 and reaches the oil passage 38 .

A portion of this flows out from the second output port 17 and passes through the filter 20 to reach the pressure port 24 of the servo valve 9.

Then, the servo valve 9 leaks internally and the tank port 25
It has now returned to the hydraulic tank 11.

However, since the amount is small, the pressure in the oil passage 38 increases.

The pressure acts on the right end of spool 32 through orifice 39, overcomes spring 35, and moves spool 32 to the left.

The orifice 39 is used to stabilize the operation of the spool 32 by adjusting the flow rate flowing in and out of the right side of the spool 32.

Since the oil passages 36 and 37 communicate there, the pressure oil flows out from the output port 14 of Biao 1 to the control valve 15.The pressure required to move the spool 32 to the left is discharged to the drain by the spring side cavity 52. Therefore, the power loss is small and the power loss is also small.

Pressure oil flowing out from the first output port 14 reaches the control valve 15, but the process from this point on is similar to a normal vent unloading circuit. When the control valve 15 is in neutral, the pressure oil that has reached the pressure port 16 reaches the vent port 20. It returns to the hydraulic tank 11.

Further, when the control valve 15 is operated, pressure oil flows out from either of the control ports 22 and 22' and reaches the actuator 8, thereby operating it.

Return oil from actuator 8 is control port)
22, 22', returns to the hydraulic tank 11 through the tank port 21.

The maximum value of oil pressure acting on actuator 8 is 1.11J
- It is regulated by the valve 23.

In this way, the pressure of the pressure oil from the main hydraulic pump 6 is
Like a normal pent unload circuit, it changes depending on the magnitude of the load acting on the actuator 8.

Next, the case where the servo valve is operated as in automatic operation will be explained.

At this time, the electromagnetic valve 61 is energized, and an appropriate current is applied to the servo valve 9 by a control panel (not shown).

Since the electromagnetic valve 61 is energized, the needle 62 overcomes the spring 63 and is pushed down, closing the space between the oil passages 55 and 64.

Therefore, the pressure oil from the auxiliary hydraulic pump 7 reaches the cavity 47 from the second input port 13 through the oil passage 43, cavity 42, orifice 46, and the pressure increases.

When this pressure acts on the conical valve 58 and reaches a certain pressure determined by the relationship between the area acting on the conical valve 58 and the mounting load of the spring 59, the pressure oil pushes the conical valve open and passes through the oil passage 57. It flows out from the drain port 19.

At the same time, this pressure oil pushes open the second check valve 50 and exits from the second output port 17 via the oil passage 38 to the filter 1.
8 and reaches the pressure port 24 of the servo valve 9.

This pressure also acts on the right end of the spool 32.

When the flow rate of pressure oil from the auxiliary hydraulic pump 7 is greater than the sum of the leakage flow rate of the servo valve 9 and the control flow rate of the servo valve 9 determined by the control current flowing through the coil of the servo valve 9, the excess flow rate flows through the orifice 46. For,
A pressure drop occurs across the orifice 460.

When this pressure drop exceeds a certain value, the spool 32 moves to the left to guide the pressure oil from the main hydraulic pump 6 from the first input port 12 to the first output port 14, and the engine rotation increases further. When the discharge flow rate from the auxiliary hydraulic pump 7 increases, the pressure drop at the orifice 46 becomes even larger, and as a result, the spool 33 also moves to the left, and the excess flow is passed through the oil passage 45 through the capity 42 and the circumferential groove 44. It flows out from drain boat 19.

In this way, if the discharge flow rate of the auxiliary hydraulic pump 7 is greater than the flow rate required by the servo valve 9, the main hydraulic pump 6
Pressure oil flows out from the first output port 14 as in normal times and acts in the same way as a normal pent unload circuit.
The pressure oil in the auxiliary hydraulic pump 7 rises to a certain constant pressure and supplies the constant oil pressure to the servo valve 9.

Next, when the control current flowing through the coil of the servo valve 9 increases and the flow rate required by the servo valve 9 becomes larger than the discharge flow rate of the auxiliary hydraulic pump 7, the discharge flow rate of the auxiliary hydraulic pump 7 is entirely equal to the second output. Since the flow exits from the port 17 to the servo valve 9, the surplus flow that flows through the orifice 46 also disappears.

Therefore, there is no pressure drop across the orifice 460, and the spools 32 and 33 are connected to the springs 35 and 41.
to move to the right.

Therefore, the pressure oil from the main hydraulic pump 6 passes through the oil path 36 from the first input port 12, pushes open the first check valve 48, flows into the oil path 38, and flows into the servo valve 9 from the second output port. Replenish pressure oil.

If this replenishment of pressure oil exceeds the flow rate required by the servo valve 9, the excess flow will flow out through the orifice 46 again, causing a pressure drop.1. This moves spool 32 to the left.

Therefore, the spool 32 is stabilized at a position where it can supply the flow rate required by the servo valve 9, and the remaining pressure oil from the main hydraulic pump 6 flows out the first output port 14.

As described above, when the servo valve 9 requires a flow rate exceeding the discharge flow rate of the auxiliary hydraulic pump 7, the shortage is replenished from the main hydraulic pump 6, and the surplus of the main hydraulic pump flows toward the control pulp 15. can be used to operate other actuators.

Since the hydraulic circuit of the present invention has the above-described configuration and operation, according to the present invention, (1) during normal work, the discharge flow rate of the main hydraulic pump flows directly to the hydraulic circuit for normal work; , it functions as a conventionally used pent unload circuit, and the discharge flow rate of the auxiliary hydraulic pump returns to the oil tank as it is, so it is possible to minimize power loss and create a hydraulic circuit with low heat generation.

(2) In addition, in cases such as during automatic work using servo valves, when the discharge flow rate of the auxiliary hydraulic pump is larger than the required flow rate of the servo valve, the discharge flow rate of the main hydraulic pump flows entirely to the hydraulic circuit for normal work and Acts as an unload circuit, increasing the hydraulic pressure of only the auxiliary hydraulic pump to the pressure required by the servo valve, so power loss can be reduced.

Further, when the servo valve requires a large flow rate, the discharge flow rate from the main hydraulic pump is supplied to compensate for the shortage, so it is possible to cope with the need for a large flow rate.

(3) Furthermore, the hydraulic pump used in this hydraulic circuit can be a simple, small, and inexpensive pump such as a gear pump used in construction machinery and the like.

As is clear from the above, by using the unload relief valve according to the present invention, even conventional construction machines having a pent unload circuit can be provided with a constant hydraulic pressure source for a hydraulic system having a servo valve at a low cost. can do.

The following practical effects can be mentioned.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an example of a pent unload circuit used in a hydraulic circuit of construction machinery, etc., Figs. 2 to 4 are schematic explanatory diagrams of an embodiment of the present invention, and Fig. 2 is a system of a hydraulic circuit. figure,
FIG. 3 is a detailed longitudinal cross-sectional view of the unload relief valve, and FIG. 4 is an explanatory diagram showing this device using JIS symbols. In Figures 2 and 3, 6: first hydraulic pump (main hydraulic pump), 7: second hydraulic pump (auxiliary hydraulic pump)
, 10: Unload relief valve, 11: Oil tank, 1st
hydraulic circuit, a second hydraulic circuit.

Claims (1)

[Claims] 1. A first hydraulic pump with a relatively large capacity, a second hydraulic pump with a smaller capacity than the first hydraulic pump, and a first and a second hydraulic circuit that requires constant oil pressure, such as a circuit connected to a servo valve, and when the required flow rate of the second hydraulic circuit is small, the above-mentioned Pressure oil is supplied from the second hydraulic pump, the pressure oil from the first hydraulic pump is controlled to flow into the first hydraulic circuit, and when the second hydraulic circuit is not operated, the first A hydraulic system characterized by comprising an unload relief valve that controls the pressure oil from the hydraulic pump to flow into the first hydraulic circuit and the pressure oil from the second hydraulic pump to return into the oil tank. Control device.