JP3688516B2 - Pump controller for hydraulic working machine - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a pump control device for a hydraulic working machine that is provided in a hydraulic working machine such as a hydraulic excavator and performs cutoff control on a discharge flow rate of the hydraulic pump.
[0002]
[Prior art]
Control for reducing the discharge flow rate of the hydraulic pump when the discharge pressure of the hydraulic pump becomes higher than a preset cut-off pressure is well known as cut-off control, and an example thereof is described in JP-A-63-195403. There are things. In this prior art, for each of a plurality of actuators driven by a hydraulic pump, a different cutoff pressure cutoff characteristic is set for each actuator, and in a single operation, control is performed with a cutoff characteristic related to the corresponding actuator. The cut-off characteristic with the highest cut-off pressure is selected and controlled among the cut-off characteristics related to the corresponding actuator.
[0003]
[Problems to be solved by the invention]
Cut-off control is used when the discharge pressure of the hydraulic pump rises above the set pressure of the relief valve of the actuator, for example, the set pressure of the main relief valve or the set pressure of the overload relief valve, while the actuator is being driven. The pressure oil discharged from the hydraulic pump is relieved to reduce the flow rate returning to the tank, thereby reducing energy loss.
[0004]
Here, if the cut-off pressure is set higher than the set pressure of the relief valve, the cut-off control will not work, and if the cut-off control is set lower than the set pressure of the relief valve, the relief valve will operate and operate with pressure oil during work under heavy load. The cut-off control is effected early before the relief, and the predetermined force and speed cannot be obtained and the speed is suddenly reduced, resulting in poor workability.
[0005]
Therefore, it is desirable to set the cut-off pressure to be slightly lower than the set pressure of the relief valve as much as possible. However, the relief valve usually has a characteristic that the relief pressure changes depending on the temperature of the hydraulic oil, and the relief pressure decreases as the temperature of the hydraulic oil increases. For this reason, even if the relief pressure is set at a predetermined temperature, the relief pressure is lowered when the temperature of the hydraulic oil rises during actual work.
[0006]
The conventional cut-off control including the above-mentioned Japanese Patent Application Laid-Open No. 63-195403 does not take any measures against the temperature change of the hydraulic oil. There is a problem that the control may not work effectively.
[0007]
An object of the present invention is to provide a pump control device for a hydraulic working machine that can perform cut-off control accurately and reliably even when the hydraulic oil temperature changes.
[0008]
[Means for Solving the Problems]
(1) In order to achieve the above object, the present invention provides a prime mover, a hydraulic pump driven by the prime mover, at least one actuator driven by pressure oil discharged from the hydraulic pump, and the hydraulic pump Provided in a hydraulic control device including a direction switching valve that controls the flow of pressure oil supplied to the actuator from the pressure sensor and a relief valve that restricts the maximum pressure of pressure oil supplied to the actuator. A tilt control means for controlling the tilt; a tilt control signal generating means for controlling the tilt control means; and a pump pressure detecting means for detecting the pressure of the hydraulic pump. The pump pressure detecting means When the detected pressure exceeds a predetermined threshold value, the tilt control means is controlled by the tilt control signal generating means to reduce the pump tilt, and the cutoff control is performed. A pump control device for a hydraulic working machine includes temperature detecting means for detecting hydraulic oil temperature, and threshold value correcting means for correcting the predetermined threshold value according to the hydraulic oil temperature detected by the temperature detecting means. And
[0009]
Thus, by providing the temperature detecting means and the threshold value correcting means and correcting the threshold value of the cutoff control according to the hydraulic oil temperature, the cutoff control can be performed accurately and reliably even if the hydraulic oil temperature changes. .
[0010]
(2) In the above (1), preferably, the threshold value correction means stores a relationship between a preset hydraulic oil temperature and a correction pressure, and stores the relationship from the hydraulic oil temperature detected by the temperature detection means. Based on the relationship, a corresponding correction pressure is calculated, and this correction pressure is added to the predetermined threshold value.
[0011]
By configuring the threshold value correcting means in this way, the threshold value correcting means corrects a predetermined threshold value according to the hydraulic oil temperature detected by the temperature detecting means, and cuts off accurately and reliably regardless of the hydraulic oil temperature. Control can be performed.
[0012]
(3) In the above (1), the relief valve is, for example, a main relief valve that limits a maximum discharge pressure of the hydraulic pump.
[0013]
As a result, an overload relief valve for limiting the maximum load pressure of the actuator is provided for the actuator of the hydraulic control device, and the set pressure of the overload relief valve is higher than the set pressure of the main relief valve. The cut-off control works before the main relief valve operates, and the cut-off control can be performed accurately and reliably regardless of the operating oil temperature.
[0014]
(4) In the above (1), the relief valve may be an overload relief valve that limits the maximum load pressure of the actuator.
[0015]
As a result, a main relief valve that restricts the maximum discharge pressure of the hydraulic pump is provided for the hydraulic pump of the hydraulic control device, and even when the set pressure of the overload relief valve is lower than the set pressure of the main relief valve. The cut-off control works before the overload relief valve operates, and the cut-off control can be performed accurately and reliably regardless of the hydraulic oil temperature.
[0016]
(5) Further, in the above (1), preferably, the temperature detecting means is provided in the immediate vicinity of the variable relief valve.
[0017]
As a result, the temperature detecting means can detect the hydraulic oil temperature without being affected by the high pressure, and the strength of the temperature detecting means can be reduced.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0019]
First, a first embodiment of the present invention will be described with reference to FIGS.
[0020]
In FIG. 1, a hydraulic control apparatus related to the pump control apparatus of the present embodiment includes a prime mover 1, a variable displacement hydraulic pump 2 driven by the prime mover 1, and an actuator that is operated by pressure oil discharged from the hydraulic pump 2. 11, 14; directional switching valves 8 and 10 for controlling the flow of pressure oil supplied to the actuators 11 and 14; and an operating lever device 7 having a pilot valve for controlling the stroke amount of the directional switching valves 8 and 10; 9, a main relief valve 4 for limiting the maximum discharge pressure of the hydraulic pump 2, a pilot pump 5 driven by the prime mover 1, and a pilot relief valve 6 for limiting the maximum discharge pressure of the pilot pump 5; Limiting the maximum load pressure of the overload relief valves 12, 13 and the actuator 14 for limiting the maximum load pressure of the actuator 11 And an overload relief valve 15, 16.
[0021]
The pump control apparatus according to the present embodiment is provided in such a hydraulic control apparatus, and includes a pump regulator 3 that controls the tilting of the hydraulic pump 2, a pump pressure sensor 19 that detects the discharge pressure of the hydraulic pump 2, and an operation. A temperature sensor 20 that detects the oil temperature, and a control device 18 that receives a signal from the pump pressure sensor 19 and the temperature sensor 20 and outputs a command to the pump regulator 3 are configured.
[0022]
The processing contents of the control device 18 are shown in a functional block diagram in FIG.
[0023]
In FIG. 2, the control device 18 has functions of a first and second table calculation units 18a and 18b, an addition unit 18c, a subtraction unit 18d, a third table calculation unit 18e, and a subtraction unit 18f.
[0024]
The pump pressure detected by the pump pressure sensor 19 is input to the first table calculation unit 18a, and the first table calculation unit 18a determines the target pump tilt by the first table A stored in the control device 18.
[0025]
Here, in the first table A, an input torque limiting characteristic is set such that the target pump tilt decreases as the pump pressure increases.
[0026]
The hydraulic oil temperature detected by the temperature sensor 20 is input to the second table calculation unit 18b, and the second table calculation unit 18b determines the correction pressure for the cut-off control using the second table B stored in the control device 18. To do.
[0027]
Here, as shown in FIG. 3, the main relief valve 4 generally has a temperature characteristic in which the relief pressure decreases as the hydraulic oil temperature increases. As an example, assuming that the average hydraulic oil temperature during actual work is 50 ° C., the main relief valve 4 is set so that the relief pressure is 350 kg / cm ² at an oil temperature of 50 ° C. (set pressure: 350 kg / cm ² ). For this reason, when the hydraulic oil temperature is in the vicinity of 50 ° C., the relief pressure substantially matches the set pressure. However, when high-load work such as heavy excavation work continues and the oil temperature rises, the relief pressure decreases to 350 kg / cm ² or less. In the second table B, for example, when the hydraulic oil temperature is 50 ° C. or less, the correction pressure is 0, and when the hydraulic oil temperature exceeds 50 ° C., the relief pressure is reduced based on 350 kg / cm ² in FIG. The correction pressure characteristic is set so that a correction pressure corresponding to the amount can be obtained.
[0028]
The adder 18c adds the correction pressure determined by the second table calculator 18b to the cut-off set pressure Pc that has been set and stored in advance to correct the cut-off set pressure Pc.
[0029]
The subtracting unit 18d subtracts the corrected cutoff setting pressure Pc from the pump pressure to obtain a pressure deviation.
[0030]
The third table calculation unit 18e inputs the pressure deviation obtained by the subtraction unit 18d, and determines the pump tilt correction amount based on the third table C stored in the control device 18.
[0031]
Here, in the third table C, when the pump pressure is higher than the cut-off set pressure Pc corrected and the pressure deviation obtained by the subtracting unit 18d becomes negative, the pump tilt correction amount of a predetermined tilt angle. Is set to output. Further, when the pump pressure decreases after the predetermined tilt angle is output, if the pump pressure becomes lower than the corrected cutoff pressure Pc by a predetermined value or more, that is, the pressure deviation obtained by the subtractor 18d is a predetermined negative value. Hysteresis is given so that the pump tilt correction amount becomes zero when the value is less than the value.
[0032]
In the subtracting unit 18f, the target pump tilt for output is determined by subtracting the tilt correction amount determined by the third table calculating unit 18e from the target pump tilt determined by the first table calculating unit 18a. . This target pump tilt is commanded to the pump regulator 3 to control the tilt of the hydraulic pump 2.
[0033]
In the present embodiment configured as described above, when the hydraulic oil temperature exceeds 50 ° C., the second table calculation unit 18b calculates a correction pressure corresponding to the hydraulic oil temperature, and this correction pressure is cut by the addition unit 18c. The cut-off set pressure Pc is corrected by adding to the off-set pressure Pc, and cut-off control is performed based on the corrected cut-off set pressure Pc. Thus, by performing temperature correction of the cut-off setting pressure when performing the cut-off control, the cut-off control can be accurately and reliably performed regardless of the hydraulic oil temperature before the relief valve is operated.
[0034]
A second embodiment of the present invention will be described with reference to FIGS. In the figure, members and functions equivalent to those shown in FIGS. 1 and 2 are denoted by the same reference numerals. This embodiment is different from the first embodiment in that operation detection switches 21 and 22 for detecting the operation of the operation lever devices 7 and 8 are added, and signals from the operation detection switches 21 and 22 are also input to the control device 18A. The A hydraulic oil temperature sensor 20 is attached to the hydraulic oil tank 17.
[0035]
Assuming that the set pressure of the main relief valve 4 is P1, the set pressure of the overload relief valves 12 and 13 of the actuator 11 is P2, and the set pressure of the overload relief valves 15 and 16 of the actuator 14 is P3, these magnitude relationships are as follows: P2 <P1 <P3.
[0036]
FIG. 5 is a functional block diagram showing the processing contents of the control device 18A.
[0037]
In FIG. 5, the control device 18A has switch switching units 18g and 18h and a maximum value selection unit 18i added to the functional block diagram of the first embodiment shown in FIG.
[0038]
In the switch switching unit 18g, when the operation of the operation lever device 7 is detected by the operation detection switch 21, the switch is turned on by a signal from the operation detection switch 21, and the preset cutoff pressure Pc1 is output.
[0039]
In the switch switching unit 18h, when the operation of the operation lever device 9 is detected by the operation detection switch 22, it is turned on by a signal from the operation detection switch 22, and the preset cutoff pressure Pc2 is stored. .
[0040]
The maximum value selection unit 18i selects the larger output value of the switch switching units 18g and 18h and outputs the selected value to the addition unit 18c as the cut-off setting pressure Pc.
[0041]
Others are the same as those of the first embodiment shown in FIG.
[0042]
Here, since the set pressure P2 of the overload relief valves 12 and 13 of the actuator 11 is lower than the set pressure P1 of the main relief valve 4, the cut-off set pressure Pc1 for the actuator 11 must be set to a value smaller than P2. Since the off control does not work and the set pressure P3 of the overload relief valves 15 and 16 of the actuator 14 is higher than the set pressure P1 of the main relief valve 4, the cutoff set pressure Pc2 for the actuator 14 must be set to a value smaller than P1. The cut-off control does not work.
[0043]
Therefore, Pc1 is set to a predetermined value smaller than P2 (Pc1 <P2), and Pc2 is set to a predetermined value smaller than P1 (Pc2> P1).
[0044]
In the present embodiment configured as described above, when only the actuator 11 is operated, it is detected by the device detection switch 21 that the operation lever device 7 is operated, the switch switching unit 18g is turned ON, and the cutoff setting is set. Control is performed by the pressure Pc1.
[0045]
Similarly, when only the actuator 14 is operated, the switch switching unit 19h is turned ON, and the control is performed by the cutoff set pressure Pc2.
[0046]
When the actuator 11 and the actuator 14 are operated simultaneously, the maximum value selection unit 18i selects and controls the larger one of Pc1 and Pc2.
[0047]
By configuring in this way, energy loss can be reduced by cut-off control according to the maximum operating pressure of each actuator in the case of single operation, and cut-off control is performed with the larger relief set pressure in the case of compound operation. Therefore, the force and speed of the actuator having the higher relief set pressure can be prevented from being affected by the cutoff of other actuators.
[0048]
When the cutoff control is performed as described above, the cutoff set pressure is corrected in accordance with the hydraulic oil temperature as in the first embodiment, so that the cutoff control can be accurately and reliably performed regardless of the hydraulic oil temperature. Yes.
[0049]
In the present embodiment, since the temperature sensor 20 is provided in the tank 17, the temperature sensor 20 is not subjected to high pressure, and the strength of the temperature sensor 20 can be reduced. The temperature sensor 20 is the same even if it is provided in the suction portion of the hydraulic pump 2.
[0050]
【The invention's effect】
According to the present invention, since the hydraulic oil temperature changes, the problem that the set pressure of the relief valve changes and the cutoff control does not operate normally can be avoided, and the cutoff is accurately and reliably performed regardless of the hydraulic oil temperature. You can control.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a hydraulic control apparatus including a pump control apparatus according to a first embodiment of the present invention.
FIG. 2 is a functional block diagram showing processing contents of the control device shown in FIG. 1;
FIG. 3 is a graph showing the relationship between hydraulic oil temperature and relief valve set pressure.
FIG. 4 is a diagram showing a hydraulic control device including a pump control device according to a second embodiment of the present invention.
FIG. 5 is a functional block diagram showing processing contents of the control device shown in FIG. 4;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Prime mover 2 Hydraulic pump 3 Pump regulator 4 Main relief valve 5 Pilot pump 6 Pilot relief valve 7, 9 Operation lever apparatus 8, 10 Direction switch valve 12, 13 Overload relief valve 11, 14 Actuator 15, 16 Overload relief valve 18 , 18A Control device 18a First and second table calculation unit 18b First and second table calculation unit 18c Addition unit 18d Subtraction unit 18e Third table calculation unit 18f Subtraction unit 18g, 18h Switch switching unit 18i Maximum value selection unit 19 Pump Pressure sensor 20 Temperature sensor 21, 22 Operation detection switch

Claims (5)

A prime mover, a hydraulic pump driven by the prime mover, at least one actuator driven by pressure oil discharged from the hydraulic pump, and a direction for controlling a flow of pressure oil supplied from the hydraulic pump to the actuator Provided in a hydraulic control device including a switching valve and a relief valve for limiting the maximum pressure of the pressure oil supplied to the actuator;
A tilt control means for controlling the tilt of the hydraulic pump; a tilt control signal generating means for controlling the tilt control means; and a pump pressure detecting means for detecting the pressure of the hydraulic pump. When the pressure detected by the pressure detection unit exceeds a predetermined threshold value, the tilt control signal generation unit controls the tilt control unit to reduce the pump tilt, and the hydraulic working machine that performs cut-off control. In the pump control device,
Temperature detection means for detecting hydraulic oil temperature;
A pump control apparatus for a hydraulic working machine, comprising: a threshold value correcting unit that corrects the predetermined threshold value according to the hydraulic oil temperature detected by the temperature detecting unit. 2. The pump control device for a hydraulic working machine according to claim 1, wherein the threshold value correction unit stores a relationship between a preset hydraulic oil temperature and a correction pressure, and the hydraulic oil temperature detected by the temperature detection unit is stored in the threshold value correction unit. A pump control apparatus for a hydraulic working machine, wherein a corresponding correction pressure is calculated based on the stored relationship, and the correction pressure is added to the predetermined threshold value. 2. The pump control apparatus for a hydraulic working machine according to claim 1, wherein the relief valve is a main relief valve that limits a maximum discharge pressure of the hydraulic pump. 2. The pump controller for a hydraulic working machine according to claim 1, wherein the relief valve is an overload relief valve that limits a maximum load pressure of the actuator. 2. The pump control device for a hydraulic working machine according to claim 1, wherein the temperature detecting means is provided in the immediate vicinity of the variable relief valve.

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