JP2000220607A - Hydraulic driving device for construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic driving device for a construction machine which can secure a stable relief pressure regardless of the variation of the hydraulic oil temperature. SOLUTION: While a hydraulic pump 2 driven by a prime mover 1; a pilot pump 3; an actuator 7 operated by the pressure oil fed from the hydraulic pump 2; a flow rate control valve 8 to control the flow of the pressure oil fed to the actuator 7 from the hydraulic pump 2; an operation means 6 to control the stroke amount of the flow rate control valve 8; and a variable relief valve 9 to prescribed the maximum discharge amount of the hydraulic pump 2; are provided to this hydraulic driving device, a temperature sensor 13 to detect the hydraulic oil temperature is provided. A relief pressure control means to control the variable relief valve 9 consists of a controller 11 to put out a control signal depending on the hydraulic oil temperature detected by the temperature sensor 13, and a solenoid proportional valve 5 driven according to the control signal put out from the controller 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive system for a construction machine such as a hydraulic shovel, and more particularly to a variable relief valve for defining a maximum discharge pressure of a hydraulic pump and a relief for controlling the relief pressure of the variable relief valve. The present invention relates to a hydraulic drive device for a construction machine having a pressure control means.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open Publication No.
No. 0704 is disclosed. FIG. 5 is a circuit diagram showing a configuration corresponding to the prior art disclosed in this publication.

[0003] The prior art shown in FIG.
0, a prime mover 21 for driving the hydraulic pump 20, a plurality of actuators 22, 23 operated by hydraulic oil discharged from the hydraulic pump 20, and a flow of hydraulic oil supplied from the hydraulic pump 20 to the actuators 22, 23. Control valve 24 including a plurality of flow control valves for controlling pressure
Operating means 26 and 27 for operating the actuators 22 and 23; and a pilot pump 33 for supplying a pilot pressure for switching the flow control valve in accordance with the operation of the operating means 26 and 27. ing.

A variable relief valve 28 is provided in a pipe 35 communicating with the discharge pipe of the hydraulic pump 20 and regulates the maximum discharge pressure of the hydraulic pump 20.
8, an electromagnetic proportional valve 29 provided between the above-described pilot pump 33, a controller 30 that outputs a control signal for controlling the electromagnetic proportional valve 29, and switching of a flow control valve included in the control valve 24. A pressure switch 31 for detecting an operation and outputting a detection signal to the controller 30; In FIG. 5, reference numeral 34 denotes a tank.

The above-described electromagnetic proportional valve 29 and controller 3
0 and the pressure switch 31 constitute a relief pressure control means for controlling the relief pressure of the variable relief valve 28.

In the prior art shown in FIG.
When the valves 6 and 27 are not operated and the flow control valve included in the control valve 24 is kept neutral, the detection signal is not input from the pressure switch 31 to the controller 30, and accordingly, the electromagnetic proportional valve 29 is transmitted from the controller 30 to the controller 30. No driving control signal is output, and the electromagnetic proportional valve 29 is
Is maintained at the lower switching position shown in FIG. Thereby, the control chamber 28a of the variable relief valve 28 communicates with the tank via the electromagnetic proportional valve 29. In this state, the opening amount of the variable relief valve 28 depends on the spring force of the control chamber 28a and the hydraulic pump 20.
The opening amount is balanced with the force due to the discharge pressure. That is, the variable relief valve 28 tends to open, and the maximum discharge pressure of the hydraulic pump 20 is maintained at a predetermined low value.

[0007] From such a state, the actuator 2
When the operating means 26 and 27 are operated to operate the control units 2 and 23, the switching operation of the flow control valve included in the control valve 24 is detected by the pressure switch 31, and the detection signal is input to the controller 30. As a result, a control signal is output from the controller 30 to the control unit of the electromagnetic proportional valve 29. As a result, the electromagnetic proportional valve 29 is switched to the upper switching position shown in FIG. 5, and the control chamber 28a of the variable relief valve 28 is connected to the pilot pump 33 via the electromagnetic proportional valve 29.
Communicate with Therefore, the pilot pressure of the pilot pump 33 is controlled by the variable relief valve 2 via the electromagnetic proportional valve 29.
8 to the control chamber 28a, and the variable relief valve 28 tends to close. As a result, the maximum discharge pressure of the hydraulic pump 20 increases and is changed to a predetermined high value.

[0008]

However, in the above-mentioned prior art, there is a problem that the relief set pressure of the variable relief valve 28 varies depending on the temperature of the hydraulic oil. That is, when the operating oil temperature decreases, the viscosity of the operating oil temperature increases, and the pressure loss of the pipe line 35 in which the variable relief valve 28 is provided increases, so that the relief pressure tends to increase. As the pressure increases, the viscosity of the hydraulic oil temperature decreases, and the pressure loss in the pipe line 35 decreases, and the relief pressure tends to decrease. As described above, in the related art, the relief set pressure changes depending on the hydraulic oil temperature, and the relief pressure decreases at a high temperature and a desired operating force of the actuator cannot be obtained. The equipment that forms the device is likely to be damaged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation in the prior art, and has as its object to provide a hydraulic drive device for a construction machine capable of securing a stable relief pressure irrespective of a change in hydraulic oil temperature. To provide.

[0010]

According to one aspect of the present invention, there is provided a hydraulic pump, a pilot pump, and a motor for driving the hydraulic pump and the pilot pump. An actuator operated by pressure oil supplied from the hydraulic pump, a flow control valve for controlling a flow of pressure oil supplied to the actuator from the hydraulic pump, and an operating means for controlling a stroke amount of the flow control valve; In a hydraulic drive device for a construction machine, comprising: a variable relief valve that regulates a maximum discharge pressure of the hydraulic pump; and a relief pressure control unit that controls a relief pressure of the variable relief valve. Means, and the relief pressure control means controls the variable relief based on the hydraulic oil temperature detected by the temperature detection means. Are a configuration consisting controls the relief pressure of the off valve.

According to the first aspect of the present invention, when the temperature detecting means detects that the operating oil temperature is lower than at normal temperature, for example, the relief pressure control means operates the variable relief valve. It is controlled to be slightly open compared to the room temperature. This suppresses the tendency that the relief pressure tends to increase due to the hydraulic oil having a high viscosity at a low temperature, so that the relief pressure can be maintained at the same level as that at normal temperature. Conversely, when the temperature detecting means detects that the operating oil temperature is higher than at normal temperature, for example, the relief pressure control means controls the variable relief valve to be more closed than at normal temperature. Accordingly, the relief pressure that is likely to be reduced by the hydraulic oil whose viscosity has been reduced at a high temperature is suppressed so as not to be reduced, and the relief pressure can be maintained at a level substantially equal to that at a normal temperature.

As described above, according to the first aspect of the present invention, when the operating oil temperature changes to a higher temperature or a lower temperature as compared with the temperature at normal temperature or the like, Can maintain a relief pressure equivalent to that at normal temperature or the like, and can always secure a stable relief pressure.

According to a second aspect of the present invention, in the first aspect of the present invention, the temperature detecting means is arranged on the upstream side of the variable relief valve and at a position near the variable relief valve. It has a configuration.

According to the second aspect of the present invention, since the relief pressure can be controlled based on the temperature of the hydraulic oil immediately before flowing into the variable relief valve, a more accurate relief pressure control can be performed. Can be realized.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydraulic drive device for a construction machine according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of a first embodiment of a hydraulic drive device for construction machines of the present invention. FIG. 2 is a hydraulic oil temperature and an electromagnetic proportional valve set in a controller provided in the first embodiment shown in FIG. FIG. 3 shows a correlation with the output pressure, and FIG.
FIG. 4 is a diagram showing a correlation between an output pressure and an electromagnetic proportional valve output pressure set in a controller provided in the embodiment.

The present embodiment is provided, for example, in a hydraulic shovel. As shown in FIG. 1, a prime mover 1, a hydraulic pump 2 and a pilot pump 3 driven by the prime mover 1, and discharge from the hydraulic pump 2 are provided. An actuator 7 driven by pressure oil, a flow control valve 8 for controlling the flow of pressure oil supplied from the hydraulic pump 2 to the actuator 7, and a variable relief defining the maximum pressure of the pressure oil discharged from the hydraulic pump 2 A valve 9, a pilot relief valve 4 for regulating a pilot pressure discharged from the pilot pump 3, and an operating means 6 for controlling the stroke amount of the flow control valve 8 described above are provided. The flow control valve 8 and the variable relief 9 described above are provided in one control valve block 10 together with a flow control valve (not shown) for controlling a plurality of other actuators (not shown).

Further, it has an electromagnetic proportional valve 5 disposed between the pilot pump 3 and the variable relief valve 9, an input / output unit, a storage unit, and a calculation unit, and outputs a control signal for driving the electromagnetic proportional valve 5. A controller 11, a tank 12 for storing hydraulic oil sucked by the hydraulic pump 2 and the pilot pump 3, and a tank 12 provided at a position of the tank 12;
Detects the temperature of the hydraulic oil in the controller and sends the detection signal to the controller 1.
1 is provided with a temperature detecting means, that is, a temperature sensor 13.

The storage section of the controller 11 stores the correlation between the hydraulic oil temperature and the output pressure of the electromagnetic proportional valve shown in FIG. 2, and the output pressure and output of the electromagnetic proportional valve set in the controller 11 shown in FIG. Each correlation with the current is stored. Here, the correlation shown in FIG. 2 is a relationship of the electromagnetic proportional valve output pressure which increases proportionally with the increase of the hydraulic oil temperature, and the correlation shown in FIG. 3 is with the increase of the electromagnetic proportional valve output pressure. And the output current is proportionally increased, and the corresponding output current is output as a control signal for driving the electromagnetic proportional valve 5 described above.

The above-described electromagnetic proportional valve 5 and controller 1
Reference numeral 1 denotes relief pressure control means for controlling the relief pressure of the variable relief valve 9 based on the operating oil temperature detected by the temperature sensor 13.

In the first embodiment configured as described above, when the temperature sensor 13 detects that the temperature of the hydraulic oil in the tank 12 is, for example, the temperature t at normal temperature, the detection signal is sent to the controller 11. The data is read into the calculation unit via the input unit. The arithmetic unit calls out the correlation between the hydraulic oil temperature and the output pressure of the electromagnetic proportional valve, which is stored in the storage unit and shown in FIG.
From this, the calculation for obtaining the electromagnetic proportional valve output pressure P corresponding to the temperature t is performed. Further, the calculation unit calls out the correlation between the output voltage of the electromagnetic proportional valve and the output current shown in FIG. 3, and from the correlation and the output pressure P of the electromagnetic proportional valve, the output current i corresponding to the output pressure P of the electromagnetic proportional valve is obtained. Is performed.
A control signal corresponding to the output current i is output from the controller 11
Is supplied to the control unit of the electromagnetic proportional valve 5 from the output unit. As a result, the electromagnetic proportional valve 5 is driven, and the opening amount is maintained at the predetermined first opening amount. The pilot pressure discharged from the pilot pump 3 is supplied to the control unit of the variable relief valve 9 via the electromagnetic proportional valve 5 held at the first opening amount. As a result, the variable relief valve 9 is driven, and the opening amount of the variable relief valve 9 is maintained at the reference opening amount at normal temperature. Accordingly, the maximum discharge pressure of the hydraulic pump 2 is maintained at a predetermined reference discharge pressure that is large enough not to damage the components of the driving device while obtaining a desired operating force when driving the actuator 7. .

In this state, when the operating means 6 is operated, the pilot pressure of the pilot pump 3 is changed to the flow control valve 8.
And the flow control valve 8 is switched. Thus, the pressure oil discharged from the hydraulic pump 2 is supplied to the actuator 7 via the flow control valve 8, and the actuator 7 is driven to perform a desired excavation operation or the like.

The temperature sensor 13 detects that the temperature of the hydraulic oil in the tank 12 is lower than a temperature t at a normal temperature, for example, t1.
Is detected, the detection signal is read into the arithmetic unit via the input unit of the controller 11. The calculation unit calls out the correlation between the hydraulic oil temperature and the output pressure of the electromagnetic proportional valve shown in FIG. 2 stored in the storage unit, and obtains the temperature t1 from the correlation and the value of the detection signal, that is, the temperature t1.
Is performed to obtain the electromagnetic proportional valve output pressure P1 (<P) corresponding to. Further, the arithmetic unit calls out a correlation between the output pressure of the electromagnetic proportional valve and the output current shown in FIG. 3, and, based on the correlation and the output pressure P1 of the electromagnetic proportional valve, an output current i1 corresponding to the output pressure P1 of the electromagnetic proportional valve. The calculation for (<i) is performed. A control signal corresponding to the output current i1 is provided from an output section of the controller 11 to a control section of the electromagnetic proportional valve 5. As a result, the electromagnetic proportional valve 5 is driven, and its opening amount is maintained at the second opening amount smaller than the above-described first opening amount. The pilot pressure discharged from the pilot pump 3 is supplied to the control unit of the variable relief valve 9 via the electromagnetic proportional valve 5 held at the second opening amount. That is,
The pilot pressure applied from the pilot pump 3 to the control unit of the variable relief valve 9 via the electromagnetic proportional valve 5 becomes smaller than when the hydraulic oil temperature is t at normal temperature. As a result, the variable relief valve 9 is driven so that its opening amount becomes larger than the above-mentioned reference opening amount at normal temperature. At this time, since the hydraulic oil temperature is the low temperature t1, the viscosity tends to be higher than the hydraulic oil temperature t at normal temperature, and the relief pressure tends to be higher. However, since the opening amount of the variable relief valve is made larger than the reference opening amount at normal temperature as described above, the relief pressure is not likely to be increased, and the maximum discharge pressure of the hydraulic pump 2 is reduced. A pressure equivalent to the above-described reference discharge pressure can be maintained.

The temperature sensor 13 detects that the temperature of the hydraulic oil in the tank 12 is higher than the temperature t at normal temperature t2.
Is detected, the detection signal is read into the arithmetic unit via the input unit of the controller 11. The arithmetic unit calls out the correlation between the hydraulic oil temperature and the output pressure of the electromagnetic proportional valve shown in FIG. 2 stored in the storage unit, and obtains the temperature t2 from the correlation and the value of the detection signal, that is, the temperature t2.
Is calculated to find the electromagnetic proportional valve output pressure P2 (> P) corresponding to Further, the arithmetic unit calls out a correlation between the output voltage of the electromagnetic proportional valve and the output current shown in FIG. 3, and, based on the correlation and the output pressure P2 of the electromagnetic proportional valve, an output current i2 corresponding to the output pressure P2 of the electromagnetic proportional valve. (> I) is calculated. A control signal corresponding to the output current i2 is provided from the output of the controller 12 to the controller of the electromagnetic proportional valve 5. As a result, the electromagnetic proportional valve 5 is driven, and its opening amount is maintained at the third opening amount larger than the above-described first opening amount. The pilot pressure discharged from the pilot pump 3 is supplied to the control unit of the variable relief valve 9 via the electromagnetic proportional valve 5 held at the third opening amount. That is,
The pilot pressure supplied from the pilot pump 3 to the control unit of the variable relief valve 9 via the electromagnetic proportional valve 5 becomes larger than when the hydraulic oil temperature is t at normal temperature. As a result, the variable relief valve 9 is driven such that the opening amount is smaller than the above-described reference opening amount at normal temperature. At this time, since the operating oil temperature is the high temperature t2, the viscosity tends to be lower than the operating oil temperature t at normal temperature, and the relief pressure tends to be lower. However, since the opening amount of the variable relief valve is smaller than the reference opening amount at normal temperature as described above, it is suppressed that the relief pressure tends to decrease so that the maximum discharge pressure of the hydraulic pump 2 is reduced. A pressure equivalent to the above-described reference discharge pressure can be maintained.

According to the first embodiment configured as described above, the operating oil temperature is higher than the normal temperature t by the temperature t2.
, Or when the temperature changes to a low temperature t1, a relief pressure equivalent to the normal temperature t can be maintained, and a stable relief pressure can always be secured. A change in the maximum discharge pressure of the hydraulic pump 2 due to a change in the hydraulic oil temperature can be prevented, and regardless of the change in the hydraulic oil temperature, the operating force of the actuator 7 can be ensured, and the equipment forming the hydraulic drive device can be damaged. Can be realized at the same time.

FIG. 4 is a diagram showing the configuration of the second embodiment of the present invention. In the second embodiment, the temperature sensor 13 is arranged on the control valve block 10 located on the upstream side of the variable relief valve 9 and near the variable relief valve 9. Other configurations are the same as those of the first embodiment shown in FIGS.

The second embodiment configured as described above has the same functions and effects as those of the above-described first embodiment.
Since the relief pressure can be controlled based on the temperature of the hydraulic oil immediately before flowing into the variable relief valve 9, more accurate relief pressure control can be realized, and accordingly, the maximum discharge pressure of the hydraulic pump 2 is more stable. Pressure can be maintained.

[0027]

According to the invention of each claim of the present invention,
A stable relief pressure can be secured irrespective of changes in hydraulic oil temperature, thereby preventing fluctuations in the maximum discharge pressure of the hydraulic pump due to changes in hydraulic oil temperature. In addition, it is possible to simultaneously realize both securing of the operating force of the actuator and prevention of damage to the equipment forming the hydraulic drive device.

In particular, according to the second aspect of the present invention,
Since the relief pressure can be controlled based on the temperature of the hydraulic oil immediately before flowing into the variable relief valve, more accurate relief pressure control can be realized, and accordingly the maximum discharge pressure of the hydraulic pump can be controlled to a more stable pressure. Can be maintained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a first embodiment of a hydraulic drive device for a construction machine of the present invention.

FIG. 2 is a diagram showing a correlation between a hydraulic oil temperature set in a controller provided in the first embodiment shown in FIG. 1 and an output pressure of an electromagnetic proportional valve.

FIG. 3 is a diagram showing a correlation between an output pressure and an output pressure of an electromagnetic proportional valve set in a controller provided in the first embodiment shown in FIG. 1;

FIG. 4 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 5 is a circuit diagram illustrating an example of a conventional hydraulic drive device for a construction machine.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 motor 2 hydraulic pump 3 pilot pump 4 pilot relief valve 5 solenoid proportional valve 6 operating means 7 actuator 8 flow control valve 9 variable relief valve 10 control valve block 11 controller [relief pressure control means] 12 tank 13 temperature sensor (temperature detecting means) ) [Relief pressure control means]

Continued on the front page (72) Inventor Takeshi Nakamura 650, Kandamachi, Tsuchiura-shi, Ibaraki F-term in Tsuchiura Works, Hitachi Construction Machinery Co., Ltd. F-term (reference) DB47 DB49 EE01 EE04 EE17 EE22 EE36 FF01 GG02 JJ02

Claims (2)

[Claims] 1. A prime mover, a hydraulic pump and a pilot pump driven by the prime mover, an actuator operated by hydraulic oil supplied from the hydraulic pump, and a hydraulic oil supplied from the hydraulic pump to the actuator. A flow control valve for controlling the flow, operating means for controlling the stroke amount of the flow control valve, a variable relief valve for regulating the maximum discharge pressure of the hydraulic pump, and a relief pressure for controlling the relief pressure of the variable relief valve A hydraulic drive device for a construction machine having control means, comprising: a temperature detection means for detecting a hydraulic oil temperature;
A hydraulic drive device for a construction machine, wherein the relief pressure control means controls a relief pressure of the variable relief valve based on a hydraulic oil temperature detected by the temperature detection means. 2. The hydraulic drive device for a construction machine according to claim 1, wherein said temperature detecting means is arranged on the upstream side of said variable relief valve and at a position near said variable relief valve.