JPH02261901A - Make-up device of hydraulic circuit using load sensing system - Google Patents

Abstract

PURPOSE:To prevent an undesired rise of pressure as well as to attempt to improve make-up efficiency by releasing a make-up line by way of opening a make up valve when a hydraulic motor rotates and it is detected that a control valve is in a neutral position. CONSTITUTION:When an inertial running state is detected by a rotation detec tion means 35 of a hydraulic motor 4A and a neutral position detection means 37 of a control valve 2A, a make-up valve 34 opens, and discharge oil of a variable capacity hydraulic pump 1 is supplied to main lines 13A, 13B through make-up lines 32a, 32b to carry out make-up. In this case, the discharge capacity of the pump 1 is controlled by a load sensing regulator 11 and make-up oil is thoroughly supplied to the motor 4A. Additionally, when differential pressure between the discharge pressure of the pump 1 and the load pressure of the motor 4A becomes more than a specific value, an unload valve 15 opens, and accordingly, even if the makeup flow increases, its pressure never becomes more than the specific value. Consequently, it is possible to improve make-up efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a make-up device for a hydraulic circuit using a load sensing system suitable for use in a hydraulic excavator or the like.

B. Prior art FIG. 4 shows an example of a hydraulic circuit of a conventional hydraulic sliding vehicle using a load sensing system. This hydraulic circuit includes a travel hydraulic circuit TC for driving the hydraulic travel motor 4A and an excavation hydraulic circuit DC for moving the hydraulic cylinders 4Bti-iH, and each circuit is provided with control valves 2A and 2B. .

The load sensing system is a control valve 2A.

2B front and back pressure, i.e. control valve inlet pressure (pump pressure)
The discharge volume (hereinafter referred to as the tilting angle) of the variable displacement hydraulic pump 1 is controlled so that the differential pressure between be.

Therefore, a load sensing regulator 11 is provided which switches according to the differential pressure between the pump pressure and the load sensing pressure.
When the pressure exceeds the pressure set by la, the load sensing regulator 11 switches to position A in accordance with the pressure. In this position, the pump pressure is guided to the servo cylinder 12, the pump tilting angle becomes small, and the pump discharge flow rate is reduced.On the other hand, when the differential pressure becomes less than the pressure set by the spring Lla, the load sensing regulator 11 Switching towards the mouth position, the servo cylinder 12 is connected to the tank. As a result, the pump tilt angle increases and the pump discharge flow rate increases.

In addition, the load sensing pressure is the load sensing line 1.
The load sensing regulator 11 is taken out from either one of the circuits via the high pressure selection valve 17 provided at the
guided by. Furthermore, in FIG. 4, 19A and 19B are pressure compensation valves that independently compensate the load pressure of each circuit TC and DC, and 15 is an unload valve, which is used to adjust the load sensing pressure and the discharge pressure of the variable displacement hydraulic pump 1. When the differential pressure between the valve and the pump reaches a predetermined value or more, the valve opens and the oil discharged from the variable displacement hydraulic pump 1 is guided to the tank.

Through the above operations, in the load sensing system, the pump tilting angle is controlled so that the pump discharge flow rate becomes the required flow rate of the control valve 2A or 2B, and unnecessary flow is not discharged and waste due to throttling loss is eliminated. It improves fuel efficiency and is easy to operate.

The direction and flow rate of the pressure oil discharged from the variable displacement hydraulic pump 1 controlled by such a load sensing system are controlled by the hydraulic pilot type control valves 2A and 2B.

For example, in the travel hydraulic circuit TC, when the forward/reverse switching valve 8 is switched to forward (F position fil) and the pedal 6a of the pilot valve 6 is operated, the oil discharged from the hydraulic pump 5 is transferred to the pilot port 2a of the pilot type control valve 2A. Guided by
This control valve 2A switches with a stroke amount depending on the pilot oil pressure. As a result, the oil discharged from the variable displacement hydraulic pump 1 is supplied to the hydraulic motor 4Δ via the counterbalance valve 3, and the vehicle runs. Vehicle speed is controlled by pilot valve 6
Depends on the amount of depression.

When the pedal 6a is released while the vehicle is running, the pilot valve 6 shuts off the pressure oil and its outlet port is communicated with the tank 10. As a result, the pressure oil acting on the pilot port 2a is removed from the forward/reverse switching valve 8. Slow return valve7. Returns to tank 10 via pilot valve 6.

At this time, the return oil is throttled by the throttle 7a of the slow return valve 7, the two pilot type control wells are gradually switched to the neutral position, and the vehicle is decelerated.

During such deceleration, from the hydraulic pump 1 to the main pipe 13A,
13B is no longer supplied with pressure oil, the hydraulic motor 4A acts as a pump, and the oil is supplied to the hydraulic motor 4A.

It circulates within the control valve 2A and main pipes 13A and 13B.

However, due to pressure loss, leakage, or drain in the circuit, the amount of oil flowing into the hydraulic motor 4A may be insufficient and cavitation may occur.

Therefore, the oil discharged from the pilot hydraulic pump 5 is transferred to the makeup line 20 and the double check valve 21a.

21b to the main pipes 13A and 13B connected to the hydraulic motor 4A and the control valve 2A to prevent cavitation.

Problems to be Solved by the C0 Invention However, in order to ensure a sufficient makeup flow rate, it is necessary to sufficiently increase the capacity of the pilot hydraulic pump 5, which increases costs.

In addition, when restarting after deceleration, if the discharge oil of the pilot hydraulic pump 5 flows to the makeup pipe vr20 side, the flow rate to the control valve 2 side will be insufficient, causing a delay in the pilot pressure acting on the control valve 2A. . This phenomenon becomes particularly noticeable when exiting the vehicle, and has a negative impact on driving feeling.

Note that instead of making up the oil from the pilot hydraulic pump 5, there is also a method of making up by connecting the double check valves 21a and 21b directly to the tank, but if the tank back pressure is low, the makeup flow rate will be insufficient. Cavitation is particularly likely to occur during deceleration during deceleration, which has a negative impact on the lifespan of hydraulic equipment. In order to increase the tank back pressure, increase the set pressure of the tank low pressure relief valve (not shown).

The effective pressure of the hydraulic motor decreases, which is undesirable. moreover,
Pressurizing the tank with air increases costs.

A technical object of the present invention is to improve make-up efficiency in a hydraulic circuit using a load sensing system without increasing costs or affecting other hydraulic equipment.

01 Means for Solving the Problems The present invention will be explained with reference to FIG. 1 showing an embodiment of the invention. A hydraulic motor 4A that is rotated by oil to drive an inertial load, a control valve 2A that controls pressure oil flowing to the hydraulic motor 4A,
A load sensing system comprising a load sensing regulator 11 that controls the discharge volume of the variable displacement hydraulic pump 1 so as to maintain the discharge pressure of the variable displacement hydraulic pump 1 by a predetermined value higher than the load pressure of the hydraulic motor 4A is used. Applied to hydraulic circuit makeup equipment.

The above-mentioned technical problem is solved by the following configuration.

Rotation detection means 35 detects that the hydraulic motor 4A is rotating, valve position detection means 37 detects that the control valve 2A is in the neutral position, and the hydraulic motor 4A and the control valve 2A.
Main conduit 13A communicating with.

13B to the discharge pipe 31 of the variable displacement hydraulic pump 1, and both detection means 35.3 disposed in the makeup pipes 32a, 32b.
When it is detected in step 7 that the hydraulic motor 4A rotates and the control valve 2A is in the neutral position, the makeup lines 32a, 3
2b.

An unload valve 1 that opens when the differential pressure between the discharge pressure of the variable displacement hydraulic pump 1 and the load pressure of the hydraulic motor 4A exceeds a predetermined value and releases the discharge pressure of the variable displacement hydraulic pump 1 to a low pressure line.
5 may be provided.

81 action For example, when an inertial running state is detected by the rotation detecting means 35 and the valve position detecting means 37, the make-up valve 34 opens and the oil discharged from the variable displacement hydraulic pump 1 passes through the make-up pipes 32a and 32b. It is supplied to main conduits 13A and 13B connected to the input/output port of the hydraulic motor 4A. This allows makeup to be applied. Since the discharge volume (tilting angle) of the variable displacement hydraulic pump 1 is controlled by the load sensing regulator 11, the pump tilting angle is controlled according to the make-up request diversion, so that makeup oil can be sufficiently supplied to the hydraulic motor 4A. .

In addition, the discharge pressure of the variable displacement hydraulic pump 1 and the hydraulic motor 4
The unload valve 15 opens when the differential pressure with the load pressure of A exceeds a predetermined value, and even if the makeup flow rate increases, the makeup pressure does not rise above the above differential pressure, and each device forming the makeup circuit There is no effect on the durability of the product.

F. Example 1.First embodiment- A first embodiment of the present invention will be described with reference to FIG.

Note that the same parts as in FIG. 4 will be described with the same reference numerals.

The device according to this embodiment supplies make-up oil to the traveling hydraulic circuit TC using the discharge oil of the variable displacement hydraulic pump 1.
Make-up conduits 32a, 32b are provided between a and 21b.
, a make-up valve IMc including a make-up valve 34 and a make-up valve 34 are provided.

The make-up valve 34 is controlled by the differential pressure between the load sensing pressure and the discharge pressure of the pilot hydraulic pump 5, and is switched between the m position, which communicates the make-up pipes 32a and 32b, and the Ω position, which closes the make-up pipes 32a and 32b. The pilot hydraulic pump 5 is configured so that the discharge pressure of the pilot hydraulic pump 5 is guided to one pilot boat 34a of the make-up valve 34 only when traveling.
and one pilot boat 34a of the make-up valve 34.
A traveling detection valve 35 is disposed between the two. This traveling detection valve 35 is a three-position switching valve, and in the neutral position N, one pilot boat 34a of the make-up valve 34 is connected to the pipe 36.
b to the tank, and the pilot boat 34a and the pilot hydraulic pump 5 are connected to the pipe line 3 at the operating positions ILL and M.
6a and 36b. The other pilot boat 34b of the make-up valve 34 is connected to the load sensing pipe 18 by a pipe 37. Furthermore, make-up Ir! A relief valve 38 is provided in the passage 32b.

In addition, 45 is a swivel joint installed at the connection portion between the upper revolving structure and the lower traveling structure.

In the above configuration, the running detection valve 35 connects the rotation detection means to the pipe l537 connected to the load sensing line 18.
constitute the valve position detection means.

The operation of the hydraulic circuit configured in this way will be explained.

During normal running, when the running pedal 6a is released and the vehicle starts decelerating running, the control valve 2A is gradually switched to the neutral position. Therefore, for example, the pressure in the conduit 13B becomes high, the pressure in the conduit 13A becomes low, and the travel detection valve 35 is switched to the M position. As a result, the discharge pressure of the pilot hydraulic pump 5 is guided to one pilot boat 34a of the make-up valve 34. On the other hand, during this deceleration operation, the control valve 2A is switched to the neutral position, so the load sensing pressure becomes zero, and as a result, the make-up valve 34 is switched to the m position, and the make-up pipe 32a
and 32b are connected. Therefore, the oil discharged from the variable displacement hydraulic pump 1 passes through the make-up circuit MC, is guided from the double check valves 21a and 21b to the main conduits 13A and 13B of the travel motor 4A, and is made up.

Here, since the tilting angle of the variable displacement hydraulic pump 1 is controlled by the load sensing regulator 11, when the required make-up flow rate increases and the pressure in the pump discharge pipe 31 decreases, the tilting angle of the pump 1 is controlled accordingly. The corner becomes larger and the discharge flow rate increases, allowing a sufficient amount of makeup oil to be supplied. Furthermore, when the differential pressure between the load sensing pressure and the load pressure of the hydraulic motor 4A exceeds a predetermined value, the unload valve 15 opens and the discharge pressure of the variable displacement hydraulic pump 1 escapes to the low pressure line. This prevents the make-up pressure from increasing undesirably even if a sufficient flow rate is applied.

1.Second embodiment- A second embodiment of the present invention will be described with reference to FIG.

The same parts as in FIG. 1 will be described with the same reference numerals.

The pilot hydraulic make-up valve 34 is an electromagnetic switching make-up valve 134, and when an inertial running state is detected, the make-up valve 134 is electrically switched to supply make-up oil to the running hydraulic circuit TC.

For inertial running, control valve 2A is neutral and main pipe &8113A
, 13B can be detected by determining whether high pressure is generated in either one of them. Therefore, the travel detection valve 35 is switched based on the differential pressure between the main pipes 13A and 13B, and the discharge pressure of the pilot hydraulic pump 5 is guided to the pressure sensor 41. On the other hand, when the control valve 2A is in the neutral state, the load sensing pressure is zero. In order to detect this, load sensing pressure is introduced to the pressure sensor 42. The detection outputs of the pressure sensors 41 and 42 are sent to the controller 43.
is input, and the controller 43 determines inertial travel.

FIG. 3 is a flowchart for detecting an inertial running state.

In step S1, the running state signal P1 and the control valve position signal P2, which are the detection outputs of the pressure sensors 41 and 42, are read,
In step S2, it is determined whether Pl is greater than or equal to a predetermined value R1,
In step S3, it is determined whether R2 is zero. Step S
2. If both S3 are affirmed, the process proceeds to step S4, and the makeup valve 134 is switched to the m position. Step S2
, S3 is negative, the process proceeds to step S5, and the makeup valve 134 is switched to the Q position.

Step S4. After executing S5, return to the beginning.

Even in the second embodiment as described above, makeup similar to that in the first embodiment can be achieved.

In addition, detection of whether or not it is actually running is performed using the main pipe 13.
This can be done in various ways, such as directly detecting the differential pressure between A and 13B with a differential pressure gauge, or monitoring the rotation of the travel drive shaft. Furthermore, the neutral state of the control valve 2A can be detected in various ways, such as by monitoring the discharge pressure of the pilot valve 6 or directly monitoring the amount of depression of the travel pedal 6a.

Furthermore, although the makeup of the travel hydraulic circuit has been described above, it can also be applied to a swing hydraulic circuit or a circuit having a hydraulic motor that moves other inertial bodies.

G0 Effects of the Invention According to the present invention, in a hydraulic circuit using a load sensing system, when an inertia turbulence state of the hydraulic motor is detected, the hydraulic motor is inertia-driven by the discharge oil of a variable displacement hydraulic pump for driving the hydraulic motor. Since makeup oil is supplied to the pump, makeup efficiency can be improved without increasing the makeup pump capacity. In addition, when the differential pressure between the load sensing pressure and the load pressure of the hydraulic motor exceeds a predetermined value, the discharge line of the variable displacement hydraulic pump is communicated with the low pressure line, so that the discharge oil of the variable displacement hydraulic pump can provide sufficient flow. Even when applying makeup, the makeup pressure is prevented from increasing undesirably.

[Brief explanation of drawings]

1 and 2 are circuit diagrams showing first and second embodiments of the present invention, FIG. 3 is a flowchart showing an example of the processing procedure of the second embodiment, and FIG. 4 is a circuit showing a conventional example. It is a diagram. 1: Variable displacement hydraulic pump 2A, 2B: Pilot type control well 3: Counter balance valve 4A: Hydraulic motor 5: Pilot hydraulic pump 6: Pilot valve 7: Slow return valve 8:
Forward/forward switching valve 11: Load sensing regulator 12: Servo cylinder 13A, 13B: Main pipe IS;
Unload valves 32a, 32b: Make-up pipe line 34: Make-up valve 35: Travel detection valve 37: Pipe line

Claims (1)

[Claims] 1) A variable displacement hydraulic pump driven by a prime mover, a hydraulic motor that is rotated by pressure oil discharged from the variable displacement hydraulic pump and drives an inertial load, and pressure oil flowing through the hydraulic motor. and a load sensing regulator that controls the discharge volume of the variable displacement hydraulic pump so as to maintain the discharge pressure of the variable displacement hydraulic pump higher than the load pressure of the hydraulic motor by a predetermined value. A make-up device for a hydraulic circuit using a load sensing system, comprising: rotation detection means for detecting that the hydraulic motor is rotating; valve position detection means for detecting that the control valve is in a neutral position; a make-up conduit connecting a conduit communicating the hydraulic motor and the control valve to a discharge conduit of the variable displacement hydraulic pump; A make-up device for a hydraulic circuit using a load sensing system, further comprising a make-up valve that opens a make-up conduit when it is detected that the control valve is in a neutral position. 2) An unload valve is provided that opens when the differential pressure between the discharge pressure of the variable displacement hydraulic pump and the load pressure of the hydraulic motor exceeds a predetermined value, and releases the discharge pressure of the variable displacement hydraulic pump to a low pressure line. A makeup device for a hydraulic circuit using the load sensing system according to claim 1.