JPH06136790A - Drive control device of hydraulic machine - Google Patents

Abstract

PURPOSE:To obtain a specific large excavating force and a specific large hanging up force without changing specially the pressure resisting strength of a conventional hydraulic pressure circuit, and without providing a variable relief valve to convert the pressure into three stages or more as a relief valve to prescribe the exhaust pressure of a main hydraulic pump. CONSTITUTION:To a duct line to connect a direction change-over valve 15 for boom and the bottom side of a boom cylinder 5, a variable type overload relief valve 19 controllable in two steps of the high and the low pressures is provided. A solenoid change-over valve 30 which can drive the overload relief valve 19 is provided, and a heavy lift switch 31 to operate the solenoid change- over valve 30 is provided. And a set pressure of a variable relief valve 18 to prescribe the discharge pressure of a main hydraulic pump 13 is set at 2500kPa at the lower pressure side, and 3000kPa at the high pressure side, while the set pressure of the overload relief valve 19 is set at 2700kPa at the low pressure side, and 3100kPa at the high pressure side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a variable relief valve which is provided in a hydraulic machine such as a hydraulic excavator and which switches a discharge pressure of a main hydraulic pump for supplying pressure oil to a boom cylinder to two stages, high and low, and a boom cylinder. The present invention relates to a drive control device having an overload relief valve in a pipe line connected to.

[0002]

2. Description of the Related Art FIG. 2 is a side view showing a hydraulic excavator cited as an example of a hydraulic machine, and FIG. 3 is a circuit diagram showing a conventional drive control device provided in the hydraulic excavator shown in FIG.

A hydraulic excavator shown in FIG. 2 has a revolving structure 1 forming a main body, a traveling structure 2 arranged below the revolving structure 1, and a revolving wheel 3 connecting the traveling structure 2 and the revolving structure 1.
A boom 6 provided on the revolving structure 1 so as to be vertically rotatable, and a boom cylinder 5 for rotating the boom 6.
An arm 8 rotatably provided at the tip of the boom 6, an arm cylinder 7 for rotating the arm 8, and an arm 8
And a bucket cylinder 9 for rotating the bucket 10.

As shown in FIG. 3, the drive control device provided in the hydraulic excavator shown in FIG. 2 is a main hydraulic pump capable of supplying pressure oil to each of the boom cylinder 5, the arm cylinder 7, and the bucket cylinder 9 described above. 13, a boom directional control valve 15, an arm directional control valve 16, and a bucket directional control valve 15 for controlling the flow of pressure oil supplied from the main hydraulic pump 13 to the boom cylinder 5, the arm cylinder 7, and the bucket cylinder 9, respectively. The switching valve 17, the constant pressure type overload relief valves 33, 20 provided in a pipe line that connects the boom direction switching valve 15 and the boom cylinder 5,
Constant pressure type overload relief valve 2 provided in a pipe line connecting the arm direction switching valve 16 and the arm cylinder 7.
1, 22, constant pressure type overload relief valves 23, 24 provided in a pipe line connecting the bucket directional switching valve 17 and the bucket cylinder 9, and a tank 32. Further, the discharge pressure of the main hydraulic pump 13 is set to a predetermined high pressure, for example 3000 kPa, and a predetermined low pressure, for example 2500 kPa.
A variable relief valve 18 that can be controlled in two stages of Pa, an electromagnetic switching valve 28 connected to a drive portion of the variable relief valve 18, a pilot pump 14 connected to the electromagnetic switching valve 28, and an electromagnetic switching valve. The excavation force increase switch 2 that outputs a signal for driving the electromagnetic switching valve 28 to the drive unit of
9 and 9. The electromagnetic switching valve 28 and the pilot pump 14 described above constitute a driving means for switching the variable relief valve 18. The set pressures of the constant pressure type overload relief valves 33, 20, the constant pressure type overload relief valves 21, 22 and the constant pressure type overload relief valves 23, 24 described above are set to, for example, 2700 kPa.

In the prior art having such a structure, when the excavation force increase switch 29 is OFF, the electromagnetic switching valve 28 is kept at the right position as shown in FIG. 3, and the variable relief valve 18 is provided. Is connected to the tank 32, and the set pressure of the variable relief valve 18 is low pressure 2500 k.
It is kept at Pa. Therefore, in this state, for example, when the boom directional control valve 15 is switched, a pressure of 2500 kPa is introduced to the boom cylinder 5, the boom 6 rotates, and excavation work by the force of 2500 kPa becomes possible. During the excavation work, the boom 6 has 2700 kPa.
When the above excessive load is applied, the overload relief valve 33 or the overload relief valve 2
0 operates, and due to the excessive load, the high pressure generated in the pipeline connecting the boom directional control valve 15 and the boom cylinder 5 is released to the tank 32, and damage to the pipeline and the like is prevented.

When the excavation force increase switch 29 is operated so as to increase the excavation force, the electromagnetic switching valve 28 is switched to the left position in FIG. 3, and the variable relief valve 18 is driven. Is connected to the pilot pump 14, and the pilot pressure of the pilot pump 14 is given to the drive unit of the variable relief valve 18 via the electromagnetic switching valve 28, and the set pressure of the variable relief valve 18 is high pressure, that is, 3000 kPa. Can be switched to. In this state, for example, when pressure oil is supplied to the bottom side of the boom cylinder 5 to extend the boom cylinder 5, the pressure of the pressure oil discharged from the main hydraulic pump 13 is The set pressure of the overload relief valve 33 is raised to 2700 kPa. Therefore, a large excavating force equivalent to this 2700 kPa can be obtained.

In such a hydraulic excavator, in addition to the above-described excavation work, a work of lifting a heavy steel pipe 12 with a rope 11 as shown in FIG. 2 may be performed. In such a case, it is desired to supply a higher pressure to the bottom side of the boom cylinder 5.

As a countermeasure against this, the variable relief valve 18 which regulates the discharge pressure of the main hydraulic pump 14 is, for example, 2500 k.
It is theoretically possible to set the set pressure of the overload relief valve 33 provided in the pipe line connected to the bottom side of the boom cylinder 5 to, for example, 3000 kPa, which is configured by a switchable device in three stages of Pa, 2700 kPa, and 3100 kPa. Conceivable. Assuming that such a thing can be realized, at the time of the lifting work of the pipe 12 described above, the setting pressure of the variable relief valve 18 is switched so as to become 3100 kPa, so that the bottom side of the boom cylinder 5 is not moved. The pressure can be supplied up to 3000 kPa, which is the pressure regulated by the overload relief valve 33, and the pipe 12 can be hoisted by a force larger than the large excavation force described above.
However, manufacturing a variable relief valve that can be switched to three stages is technically difficult and costly at present, and is not realistic.

In view of the above, in consideration of the hoisting work with a large force, in the conventional hydraulic circuit shown in FIG. 3, the variable relief valve 18 has 2500 as described above.
It is conceivable that the set pressure can be switched to kPa or 3000 kPa, and only the constant pressure type overload relief valve 33 provided in the conduit connected to the bottom side of the boom cylinder 5 has the set pressure of 3100 kPa. In the case of such a configuration, the set pressure of the variable relief valve 18 becomes 3000 kPa by turning on the excavation force increase switch 29 shown in FIG. That is,
When supplying pressure oil to the bottom side of the boom cylinder 5, the set pressure of the overload relief valve 33 is set to 310.
Since it is 0 kPa, it is possible to supply a two-step operating pressure of 2500 kPa and 3000 kPa to the bottom side of the boom cylinder 5, and 3000 kPa is required for lifting work.
It becomes possible to work with a large force equivalent to Pa.
In addition, during the lifting work, the boom 6 is generally used.
Is performed in small increments, so that
Even when working at a high pressure of 3000 kPa during this hoisting work, a shocking load is hardly generated, and the safety of the circuit is maintained.

[0010]

However, in consideration of the hoisting work of the pipe 12 as described above, FIG.
It was intended to obtain a large excavating force by setting only the constant pressure type overload relief valve 33 provided in the pipeline connected to the boom cylinder 5 in the conventional hydraulic circuit shown in FIG. In that case, the excavation force becomes a large force equivalent to 3000 kPa,
There is a concern that a load exceeding the initially allowable load may be applied to the structure such as the boom 6 or the arm 7 or the actuator such as the boom cylinder 5, which is not preferable in terms of safety.

In consideration of such safety, it is not necessary to equip the structure such as the boom 6 and the arm 7 capable of withstanding an operating pressure of 3000 kPa, or the actuator such as the boom cylinder 5 from the beginning of designing the hydraulic excavator. This will lead to higher costs, which is unrealistic.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and its purpose is to define the discharge pressure of the main hydraulic pump without changing the pressure resistance of the conventional hydraulic circuit. It is an object of the present invention to provide a drive control device for a hydraulic machine that can obtain a predetermined large excavating force and a predetermined large lifting force without providing a variable relief valve that switches to a pressure of three or more stages as the variable relief valve.

[0013]

In order to achieve this object, the present invention provides a boom cylinder, a main hydraulic pump for supplying pressure oil for driving the boom cylinder, and a main hydraulic pump for supplying the boom cylinder to the boom cylinder. A directional control valve for controlling the flow of pressure oil, an overload relief valve provided in a pipe line connecting the directional control valve for boom and the bottom side of the boom cylinder, and the discharge of the main hydraulic pump. In a drive control device for a hydraulic machine, which includes a variable relief valve capable of controlling a pressure to a predetermined high pressure and a predetermined low pressure in two stages, and drive means for switching a set pressure of the variable relief valve, the overload relief valve is used as the overload relief valve. A controllable overload relief valve is provided in two stages of high pressure and low pressure, and the set pressure of this overload relief valve is set. A switching means for switching and a switch for outputting a signal for driving the switching means are provided, and the set pressure on the high pressure side of the overload relief valve is higher than the set pressure on the high pressure side of the variable relief valve, and Set to a value lower than the set pressure on the high pressure side of the variable relief valve, and set the set pressure on the low pressure side of the overload relief valve to the set pressure on the low pressure side of the variable relief valve and the high pressure of the variable relief valve. The pressure is set to an intermediate value with the set pressure on the side.

[0014]

For example, the preset pressure on the high pressure side of the overload relief valve provided in the bottom pipeline of the boom cylinder is set to a value larger than the preset pressure on the high pressure side of the variable relief valve.

Then, by setting the set pressure of the variable relief valve to the set pressure on the low pressure side and operating, for example, the boom direction switching valve, the pressure oil discharged from the main hydraulic pump is guided to the boom cylinder, and this variable relief is provided. It is possible to perform excavation work with a relatively small excavation force corresponding to the set pressure on the low pressure side of the valve. Further, the variable relief valve is set to a high pressure side set pressure, the overload relief valve is set to a low pressure side set pressure, and the boom directional control valve is operated, for example, to discharge from the main hydraulic pump. Hydraulic oil is guided to the boom cylinder, and excavation work is performed with a relatively large excavation force corresponding to a pressure higher than the low pressure side set pressure of the overload relief valve, that is, the low pressure side set pressure of the variable relief valve. You can

Further, the setting pressure of the variable relief valve is set to the setting pressure on the high pressure side, the setting pressure of the overload relief valve is set to the setting pressure on the high pressure side, and the boom direction switching valve is operated so as to extend the boom cylinder. Causes the pressure oil discharged from the main hydraulic pump to be guided to the bottom side of the boom cylinder to reach a pressure higher than the set pressure on the high pressure side of the variable relief valve, that is, the pressure set on the low pressure side of the overload relief valve described above. It is possible to carry out lifting work with a correspondingly large force.

Further, in the present invention, the set pressure on the high pressure side of the overload relief valve may be predetermined so as to be smaller than the set pressure on the high pressure side of the variable relief valve. In this case, set the variable relief valve to the high pressure side, set the overload relief means to the high pressure side, and operate the boom directional control valve to extend the boom cylinder. Causes the pressure oil discharged from the main hydraulic pump to be guided to the bottom side of the boom cylinder, and is higher than the set pressure on the high pressure side of the overload relief valve, that is, the pressure set on the low pressure side of the overload relief valve described above. It is possible to carry out lifting work with a large force equivalent to.

As described above, in the present invention, the set pressure on the low pressure side of the variable relief valve is set to a set pressure corresponding to a comparatively small excavation force similar to the conventional one, and the set pressure on the low pressure side of the overload relief valve is set to the conventional one. By setting the set pressure corresponding to the same relatively large excavation force, excavation work with a relatively small excavation force and excavation work with a relatively large excavation force can be performed as in the conventional case, and the lifting During lowering work, a large force corresponding to the set pressure on the high pressure side of the variable relief valve or a large force corresponding to the set pressure on the high pressure side of the overload relief valve, that is, even greater than the relatively large excavation force described above. This lifting work can be performed by force.

Therefore, since the maximum pressure when performing excavation work is about the same as the conventional pressure, it is not necessary to change the pressure resistance of the conventional hydraulic circuit, and the variable relief valve and overload are not required. High pressure as a relief valve,
It is only necessary to switch to a low pressure in two stages, that is, a predetermined large excavating force and a predetermined large lifting force can be obtained without providing a variable relief valve or the like for switching to a pressure of three or more stages.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a drive control device for a hydraulic machine according to the present invention will be described below with reference to FIG. FIG. 1 is a circuit diagram showing an embodiment of a drive controller for a hydraulic machine according to the present invention, which is drawn in correspondence with the circuit diagram shown in FIG. That is,
The embodiment shown in FIG. 1 also exemplifies the drive control device provided in the hydraulic excavator. In FIG. 1, the same members as those shown in FIG. 3 described above are designated by the same reference numerals.

That is, also in the embodiment shown in FIG. 1, the actuators such as the boom cylinder 5, the arm cylinder 7, the bucket cylinder 9 and the like, the main hydraulic pump 13 capable of supplying pressure oil to these actuators, and the main hydraulic pump 13 are provided. From the main hydraulic pump 13 to the boom cylinder 5, the arm cylinder 7,
A boom directional control valve 15, an arm directional control valve 16, a bucket directional control valve 17, a boom directional control valve 15, and a rod of the boom cylinder 5 that control the flow of pressure oil supplied to each of the bucket cylinders 9. Constant pressure type overload relief valve 20 provided in a pipe line that communicates with the
Constant pressure type overload relief valve 2 provided in a pipe line connecting the arm direction switching valve 16 and the arm cylinder 7.
1 and 22, constant pressure type overload relief valves 23 and 24 provided in a pipe line that connects the bucket directional control valve 17 and the bucket cylinder 9, and a tank 32.

Further, the discharge pressure of the main hydraulic pump 13 is a predetermined high pressure, for example 3000 kPa, and a predetermined low pressure, for example 2
Variable relief valve 1 that can be controlled in two stages of 500 kPa
8, the electromagnetic switching valve 28 connected to the drive unit of the variable relief valve 18, the pilot pump 14 connected to the electromagnetic switching valve 28, and the drive unit of the electromagnetic switching valve 28, the electromagnetic switching valve 28. An excavation force increase switch 29 that outputs a driving signal is provided.

In particular, in this embodiment, as the overload relief valve provided in the conduit communicating with the bottom side of the boom cylinder 5, an overload relief valve that can be controlled in two stages of a predetermined high pressure and a predetermined low pressure. For example, a variable overload relief valve 19 is provided, and an electromagnetic switching valve 30 is provided in a pipe line connecting the variable overload relief valve 19 and the pilot pump 14, and the electromagnetic switching valve is further provided. A switch for outputting a signal for activating 30, that is, a heavy lift switch 31 is provided. The electromagnetic switching valve 30 and the pilot pump 14 described above constitute switching means for switching the set pressure of the variable overload relief valve 19.

Further, in this embodiment, for example, the set pressure on the high pressure side of the variable overload relief valve 19 is larger than the set pressure of the variable relief valve 18 described above.
The set pressure on the low pressure side of the overload relief valve 19 is set to 100 kPa, which is an intermediate value between the set pressure on the low pressure side and the set pressure on the high pressure side of the variable relief valve 18, for example, 2700 kPa.

The operation of the embodiment thus configured is as follows. That is, the excavation force increase switch 2
When 9 is OFF, the electromagnetic switching valve 28 is kept at the right position as shown in FIG. 1, and the drive unit of the variable relief valve 18 is connected to the tank 32 via the electromagnetic switching valve 28, whereby the variable valve is changed. The set pressure of the relief valve 18 is the low pressure side 2
It is set to 500 kPa. Therefore, for example, by operating the boom direction switching valve 15, the pressure oil discharged from the main hydraulic pump 13 is guided to the boom cylinder 5 via the boom direction switching valve 15, and the variable relief valve 1
It is possible to perform excavation work with a relatively small excavation force corresponding to the set pressure of 2,500 kPa.

When the excavation force increase switch 29 is turned on, the electromagnetic switching valve 28 is switched to the left position in FIG. 1, and the pilot pressure of the pilot pump 14 drives the variable relief valve 18 via the electromagnetic switching valve 28. And the set pressure of the variable relief valve 18 is 300
The variable relief valve 18 is switched so that it becomes 0 kPa. At this time, the heavy lift switch 31 is O
In the case of FF, the electromagnetic switching valve 30 is kept in the right position shown in FIG. 1, and the drive unit of the variable overload relief valve 19 is connected to the tank 32 via the electromagnetic switching valve 30 and the variable overload relief valve is connected. The set pressure of the valve 19 is set to the low pressure side of 2700 kPa. Therefore, for example, by operating the boom direction switching valve 15 in this state, the pressure oil discharged from the main hydraulic pump 13 is guided to the boom cylinder 5 via the boom direction switching valve 15, and the overload relief valve 19 is operated. It is possible to carry out excavation work with a relatively large excavation force corresponding to 2700 kPa, which is the set pressure on the low pressure side.

When the heavy lift switch 31 is turned on with the excavation force increase switch 29 turned on,
The electromagnetic switching valve 30 is switched to the left position in FIG. 1, and the pilot pressure of the pilot pump 14 is applied to the drive unit of the variable overload relief valve 19 via the electromagnetic switching valve 30. As a result, the overload relief valve 19
Indicates that the set pressure is 3100k, which is the set pressure on the high pressure side.
Operates to become Pa. Therefore, by operating the boom direction switching valve 15 so as to extend the boom cylinder 5 in this state, the pressure oil discharged from the main hydraulic pump 13 is guided to the bottom side of the boom cylinder 15,
3000 which is the set pressure on the high pressure side of the variable relief valve 18.
It is possible to carry out the lifting work with a large force corresponding to kPa.

In the embodiment constructed as described above, 2
It is possible to perform excavation work with a relatively small excavation force equivalent to 500 kPa, excavation work with a relatively large excavation force equivalent to 2700 kPa, and lifting work with a large force equivalent to 3000 kPa. Also, the maximum pressure when carrying out excavation work is 2700
Since the size is the same as the conventional one in kPa, it is not necessary to specifically change the pressure resistance of the hydraulic circuit including the conventional structures such as booms and arms, the actuators such as the boom cylinder 5 and the like. Further, the variable relief valve 18 and the variable overload relief valve 19 need only be relief valves that switch between high and low stages, that is, it is not necessary to provide a variable relief valve that switches between three or more stages.

Therefore, from these facts, it is possible to secure a relatively large excavating force equivalent to 2700 kPa and a large lifting force equivalent to 3000 kPa without inviting a rise in manufacturing cost, which is highly practical.

In the above embodiment, the set pressure on the high pressure side of the overload relief valve 19 is set to the variable relief valve 18.
Although it is set to be higher than the set pressure on the high pressure side of the above, on the contrary, the set pressure on the high pressure side of the overload relief valve 19 may be set to be smaller than the set pressure on the high pressure side of the variable relief valve 18. Good.

With the above-described structure, when the heavy lift switch 31 is turned on with the excavation force increase switch 29 turned on, the overload relief valve 19 is turned on.
Operates so that the set pressure becomes the set pressure on the high pressure side. Therefore, by operating the boom direction switching valve 15 so as to extend the boom cylinder 5 in this state, the pressure oil discharged from the main hydraulic pump 13 is guided to the bottom side of the boom cylinder 15, and the variable relief valve 18 is provided. Which is smaller than the set pressure on the high pressure side of, which is equivalent to the set pressure on the high pressure side of the overload relief valve 19, that is,
The hoisting work can be carried out by a hoisting force larger than the excavating force corresponding to the set pressure 2700 kPa on the low pressure side of the overload relief valve 19 which gives the maximum pressure during the excavating work, and the operation is almost the same as the above-mentioned embodiment. The effect can be obtained.

Further, in the above embodiment, the overload relief which is provided in the pipe line connecting the boom directional control valve 15 and the bottom side of the boom cylinder 5 and is controllable in two stages of a predetermined high pressure and a predetermined low pressure. Although the variable overload relief valve 19 is provided as the valve, the present invention is not limited to this, and instead of the variable overload relief valve 19,
For example, a constant pressure type overload relief valve with a set pressure of 3100 kPa and a low pressure type overload relief valve with a set pressure of 2700 kPa may be provided.
Even with this configuration, it is possible to obtain substantially the same operational effects as those of the above-described embodiment.

[0033]

Since the drive control device for the hydraulic machine of the present invention is constructed as described above, the discharge pressure of the main hydraulic pump can be regulated without changing the pressure resistance of the conventional hydraulic circuit. It is possible to obtain a predetermined large excavating force and a predetermined large hoisting force without providing a variable relief valve that switches to a pressure of three or more stages as a variable relief valve that operates, and therefore is easy to manufacture in view of the current state of the art. In addition, the manufacturing cost can be kept relatively low, and it is highly practical.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a drive control device for a hydraulic machine according to the present invention.

FIG. 2 is a side view showing a hydraulic excavator taken as an example of a hydraulic machine.

FIG. 3 is a circuit diagram showing a conventional drive control device provided in the hydraulic excavator shown in FIG.

[Explanation of symbols]

 5 Boom cylinder 13 Main hydraulic pump 14 Pilot pump 18 Variable relief valve 19 Variable overload relief valve 28 Electromagnetic changeover valve 29 Excavation force increase switch 30 Electromagnetic changeover valve 31 Heavy lift switch 32 Tank

Claims (2)

[Claims] 1. A boom cylinder, a main hydraulic pump that supplies pressure oil for driving the boom cylinder, and a boom directional control valve that controls the flow of pressure oil supplied from the main hydraulic pump to the boom cylinder. The discharge pressure of the main hydraulic pump and an overload relief valve provided in a pipe line connecting the boom direction switching valve and the bottom side of the boom cylinder can be controlled to a predetermined high pressure and a predetermined low pressure. In a drive control device for a hydraulic machine including a variable relief valve and a drive means for switching a set pressure of the variable relief valve, an overload controllable as two stages of a predetermined high pressure and a predetermined low pressure as the overload relief valve. A relief valve is provided, and switching means for switching the set pressure of this overload relief valve and a signal for driving this switching means are output. A pressure switch is provided to set the high pressure side set pressure of the overload relief valve to a value higher than the high pressure side set pressure of the variable relief valve and lower than the high pressure side set pressure of the variable relief valve. One of them is set, and the set pressure on the low pressure side of the overload relief valve is set to an intermediate value between the set pressure on the low pressure side of the variable relief valve and the set pressure on the high pressure side of the variable relief valve. A drive control device for a characteristic hydraulic machine. 2. The overload relief valve is a variable overload relief valve.
Drive control device for the hydraulic machine described.