JPH07111180B2 - Load sensing hydraulic drive - Google Patents

Description

The present invention relates to a load-sensing hydraulic drive system for civil engineering and construction machinery such as a hydraulic excavator, and particularly to detecting the displacement of a hydraulic pump and performing feedback control to the displacement. The present invention relates to a load-sensing hydraulic drive device that controls a motor.

[Conventional technology]

In recent years, in hydraulic drive systems for construction machines equipped with multiple working members such as hydraulic excavators and hydraulic cranes, the discharge pressure of the hydraulic pump is a constant value higher than the maximum load pressure of the multiple hydraulic actuators that drive the multiple working members. The discharge amount of the pump is controlled so that it becomes higher only by this, and this control is called load sensing control. In the present specification, the hydraulic drive device that performs this load sensing control is referred to as a load sensing hydraulic drive device.

By the way, this load sensing hydraulic drive system has conventionally used one hydraulic pump as a basic hydraulic pump, and is configured to drive a plurality of actuators by this one hydraulic pump. Also, various types of control devices for hydraulic pumps have been proposed,
Most of them are, for example, DE-A1-3422165 (JP-A-60-1).
(Corresponding to No. 1706), the discharge pressure of the hydraulic pump and the maximum load pressure are introduced to the switching valve of the pump regulator, and the displacement of the hydraulic pump in response to the pressure difference between the two,
The swash plate pump has a hydraulic control system that controls the position of the swash plate.

[Problems to be Solved by the Invention]

In contrast to the above-mentioned state of the art, it has been attempted to use a hydraulic pump control device with an electronic control system, for example, Japanese Patent Application No. 1-16.
No. 837 was made by the applicant of the present application, and in order to perform satisfactory load sensing control in this electronic control system, displacement detection that directs displacement of hydraulic pump and swash plate position in swash plate pump The swash plate position is controlled by feedback control.

By the way, in a load-sensing hydraulic drive system equipped with a plurality of hydraulic actuators with a large capacity, it is necessary to use a large-capacity hydraulic pump capable of accommodating the actuator capacity. If this is not possible, it is necessary to use multiple hydraulic pumps. However, in the conventional hydraulic control type pump control device, when there are a plurality of hydraulic pumps, a control device must be provided for each hydraulic pump, and the hydraulic circuit becomes complicated.

Further, it is assumed that the electronically controlled pump control device proposed by the applicant of the present invention is also a single hydraulic pump, and when there are a plurality of hydraulic pumps, the position of the swash plate is detected for each of the plurality of pumps. However, there is a problem that the number of sensors is increased.

An object of the present invention is to provide a load sensing hydraulic drive system that can cope with a large capacity of the hydraulic actuator and can simplify the configuration of the pump control system.

[Means for Solving the Problems]

In order to achieve the above object, the present invention adopts the following configurations.
That is, supplying pressure oil to a plurality of hydraulic actuators,
At least a first hydraulic pump that drives this, and detection means that detects the displacement of the first hydraulic pump,
The target displacement of the first hydraulic pump that holds the differential pressure between the discharge pressure of the first hydraulic pump and the maximum load pressure of the plurality of actuators at a predetermined value is calculated, and the target displacement and the detection are calculated. Control means for calculating a first operation command value from the displacement volume detected by the means, and outputting a first command signal corresponding thereto, and displacement of the first hydraulic pump based on the first command signal. In a load-sensing hydraulic drive device including a first pump regulator that operates a volume varying means to control the displacement of the first hydraulic pump, a second hydraulic pump connected to a discharge line of the first hydraulic pump. A hydraulic pump and a second pump regulator for controlling the displacement of the second hydraulic pump by operating the displacement of the second hydraulic pump, and the control means. The second pump regulator is controlled based on the calculated target displacement of the first hydraulic pump, and the displacement of the second hydraulic pump is controlled to be the same as the displacement of the first hydraulic pump. And a second instruction signal corresponding to the second operation instruction value calculated based on the target displacement of the first hydraulic pump obtained by the control means. Is output and the second pump regulator is controlled by the second command signal.

In addition, at least a first hydraulic pump that supplies pressure oil to a plurality of hydraulic actuators and drives the hydraulic oil, a detection unit that detects a displacement of the first hydraulic pump, and a discharge pressure of the first hydraulic pump. A target displacement of the first hydraulic pump that holds the differential pressure between the maximum load pressure of the actuators and a predetermined pressure, and calculates a target displacement based on the target displacement and the displacement detected by the detection means. A control means for calculating a first operation command value and outputting a first command signal corresponding to the first operation command value; and a displacement volume changing means of the first hydraulic pump based on the first command signal. And a first pump regulator for controlling the displacement of the hydraulic pump of the first hydraulic pump, the second pump connected to the discharge line of the first hydraulic pump. And pressure pump, said second hydraulic pump displacement to operate the variable volume means, a second pump regulator for controlling a displacement volume of the second hydraulic pump,
The second pump regulator is controlled on the basis of the target displacement of the first hydraulic pump obtained by the control means so that the displacement of the second hydraulic pump becomes the same as the displacement of the first hydraulic pump. And a means for controlling the second pump regulator by the first command signal, the operation means outputting the first command signal obtained by the control means. And

Further, at least a first hydraulic pump that supplies pressure oil to a plurality of hydraulic actuators and drives the hydraulic oil, a detection unit that detects a displacement of the first hydraulic pump, and a discharge pressure of the first hydraulic pump. And a target displacement volume of the first hydraulic pump that holds a differential pressure between the maximum load pressures of the plurality of actuators at a predetermined value is calculated, and a target displacement volume and a displacement volume detected by the rendering means are calculated as a first value. A control means for calculating a first operation command value and outputting a first command signal corresponding to the first operation command value; and a displacement volume changing means of the first hydraulic pump based on the first command signal. And a first pump regulator for controlling the displacement of the hydraulic pump of the first hydraulic pump, the second pump connected to the discharge line of the first hydraulic pump. And pressure pump, said second hydraulic pump displacement to operate the variable volume means, a second pump regulator for controlling a displacement volume of the second hydraulic pump,
The second pump regulator is controlled based on the target displacement of the first hydraulic pump obtained by the control means, and the displacement of the second hydraulic pump becomes the same as the displacement of the first hydraulic pump. And a solenoid proportional valve for converting the first command signal into a hydraulic signal, and the first pump regulator is controlled by the hydraulic signal from the solenoid proportional valve. However, the operating means is means for guiding the hydraulic signal from the solenoid proportional valve to the second pump regulator and controlling it.

[Action]

In the present invention thus configured, the pump regulator of the second hydraulic pump is based on the target displacement of the first hydraulic pump, and the displacement of the second hydraulic pump is the same as the displacement of the first hydraulic pump. By providing the operating means for controlling so that the pressure oil can be supplied from the first and second hydraulic pumps to the plurality of actuators, the capacity of the actuators can be increased and the second hydraulic pump can be provided. Since it is not necessary to provide a detecting means for detecting the displacement, the structure of the pump control device can be simplified.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1, reference numeral 1 is a first variable displacement hydraulic pump, the displacement of which is controlled by a displacement variable mechanism, that is, a swash plate 2. Further, reference numeral 50 is a swash plate 51.
It is a variable displacement type second pressure oil pump whose capacity is controlled by, and its discharge pipe line 52 is connected to the discharge pipe line 3 of the first hydraulic pump 1. The pressure oil discharged from the hydraulic pumps 1 and 50 is supplied from the discharge pipe 3 through the direction switching valves 4A and 4B to the hydraulic motor 5A and the hydraulic cylinder 5B which are loads, and drives them.

Reference numeral 6 is a control device for the first and second hydraulic pumps 1, 50, which is a differential pressure gauge 7, a pressure detector 8, and a displacement detector 9 common to the first and second hydraulic pumps 1, 50. Sensor group and controller 10 and first and second hydraulic pumps
It consists of solenoid proportional valves 11,53 and pump regulators 12,54, respectively.

The differential pressure gauge 7 includes the discharge pressure Ps of the hydraulic pump 1 and the shuttle valve 22.
Hydraulic motor 5 and hydraulic cylinder 5B taken out by
Of the maximum load pressure PLmax of the hydraulic pump 1, the pressure detector 8 detects the discharge pressure Ps of the hydraulic pump 1, and the displacement detector 9 detects the position of the swash plate 2 of the hydraulic pump 1, that is, the displacement. It detects and sends the corresponding electric signal to the controller 10. The controller 10 calculates the target position of the swash plate 2 of the hydraulic pump 1 based on these detection signals, and outputs two command signals X1 and X2 corresponding thereto. This command signal X1,
X2 is sent to the solenoid proportional valves 11 and 53, and converted into hydraulic signals, which are each pump regulator 1
Loaded at 2,54.

The pump regulator 12 has a servo cylinder 13 that drives the swash plate 2 of the hydraulic pump 1, and a servo control valve 14 that determines the movement of the servo cylinder 13. The servo control valve 14 has a hydraulic pressure from the solenoid proportional valve 11 at one end. It has a pressure receiving portion 15 to which a signal is guided and a spring 16 at the other end, and the servo control valve 14 is driven to the left side in the figure against the spring 16 according to the level of the hydraulic signal guided to the pressure receiving portion 15. , The position of the piston of the servo cylinder 13, that is, the position of the swash plate 2 of the hydraulic pump 1 is determined. Similarly for the pump regulator 54, the servo cylinder 5
5, it has a servo control valve 58, a pressure receiving portion 57, and a spring 58.
Servo cylinders 13,55 and servo control valves 14,56 have hydraulic pumps 1,50 as fluids for driving the servo cylinders 13,55.
Discharge pressure is introduced via the check valve 17.

Reference numeral 18 is a pilot pump, the pilot pressure of which is set by a relief valve 19. This pilot pressure is sent to the solenoid proportional valves 11 and 53 and used as the hydraulic pressure source of the hydraulic pressure signal. Further, the pilot pressure is introduced downstream of the above-mentioned check valve 17 via the check valve 20, and is used as a second fluid for driving the servo cylinders 13, 55 when the discharge pressure of the hydraulic pump 50 is low. In addition, 21 is a tank.

The content of the calculation performed by the controller 10 is shown in a functional block diagram in FIG.

In FIG. 2, reference numeral 30 is a block for calculating a target position θo of the hydraulic pump 1 swash plate 2 from the differential pressure ΔP and pump discharge pressure Ps, and reference numeral 31 is a command signal X1, X2 from the target position θo. Is a block for generating.

In block 30, block 32 changes from differential pressure ΔP to differential pressure Δ
Differential pressure target discharge amount θΔ for maintaining P at the target differential pressure ΔPo
The change speed Δp of p is calculated, and the change speed Δp calculated here is integrated by the integration block 33 to obtain the differential pressure target discharge amount θΔp. On the other hand, in block 34, the input limit target discharge amount θT is obtained from the discharge pressures Ps of the hydraulic pumps 1 and 50 based on the input torque limit function stored in advance. The two target values θΔp, θT thus obtained are selected from the minimum values in the minimum value selection block 35, and the target value of the displacement of the hydraulic pump 1, that is, the target position θ of the swash plate 2 is selected.
o is determined.

The block 31 is composed of a first block 31A for obtaining a command signal X1 for the solenoid proportional valve 11 from the swash plate target position θo, and a second block 31B for obtaining a command signal X2 for the solenoid proportional valve 53 from the swash plate target position θo. Has become.

The first block 31A has a first control path 36 and a second control path 37. In the first control path 36, the basic command value io1 is based on the relationship in which the swash plate target position θo is stored in advance in the block 38A. Convert to. This function converts the target position θo of the swash plate 2 into the basic command value io1 according to the characteristics of the solenoid proportional valve 11. In the second control path 37, the difference between the swash plate target position θo and the position θ of the swash plate 2 detected by the displacement detector 9 is taken by the subtraction unit 39, and the block 40 having a switch function is provided.
Then, in block 41, a proportional constant K is multiplied to obtain a correction value ic. The basic command value io1 obtained in the block 38A and the correction value ic obtained in the block 41 are added by the adder 42, and the operation command value ix
And the operation command value ix is amplified by the amplifier 43A. Converted to command signal X1.

In addition, the first block 31A has a third control path 37A,
In the third control path 37A, the detection signal of the position θ of the swash plate 2 obtained by the displacement detector 9 is sent to the abnormality determination block 44, and it is determined whether or not the detection signal is abnormal. For this determination, for example, the level range of the detection signal at the normal time is stored in advance,
This can be done by checking whether the level of the detection signal is within that range. The block 44 determines that the detection signal is normal when the detection signal is within a predetermined level range, outputs a level 0 signal, determines that the level is abnormal when the detection signal deviates from the predetermined level range, and outputs a level 1 signal. This signal is block 40
Sent to. The block 40 is at the position shown in the figure when the signal is 0, transmits the deviation Δθ to the block 41, shuts off the second control path 37 when the signal becomes 1, and blocks prepared in advance.
Output the value of Δθ = 0 of 45. This causes block 41
The correction value ic sent to is 0, and the adder 42 outputs the value of the basic command value io1 as it is as the operation command value ix.

The second block 31B consists of a single control path corresponding to the first control path 36 of the first block 31A, in which the block 38B is similar to the block 38A of the first control path 36. The swash plate target position θo is converted into a basic command value io2 based on the relationship stored in advance. This function converts the target position θo of the swash plate 51 into the basic command position io2 according to the characteristics of the solenoid proportional valve 53. This basic command value io2 is directly amplified as an operation command value by the amplifier 43B and converted into a command signal X2.

The command signals X1 and X2 obtained as described above are sent to the solenoid proportional valves 11 and 53 as described above, and the pump regulators 12 and 54
The capacity of the hydraulic pump 1,50 is controlled by.

In the present embodiment configured as described above, in the block 31 in the subsequent stage of the controller 6, the first block 31A
Since the second control path 37 is not shut off when the detection signal of the displacement detector 9 is normal, the basic command value io1 is calculated from the swash plate target position θo obtained in block 30 through the first control path 36.
Is obtained, and the correction value i obtained by the second control path 37
c is added to obtain the operation command value ix, and the command signal X1 corresponding to this is generated. Therefore, the hydraulic pump 1
The swash plate position is subjected to feedback control so as to match the target position θo. That is, the first control path 36 and the second control path 37 are combined to form a feedback control system.

When an abnormality occurs in the detection signal of the displacement detector 9 due to a failure of the displacement detector 9 or an abnormality in the signal transmission system from the displacement detector 9 to the controller 10, the abnormality determination block 44 outputs level 1 Is output, and the block 40 shuts off the second control path 37. Therefore, the basic command value i
The o1 becomes the operation command value ix as it is, and the inclination 2 of the hydraulic pump 1 is controlled in an open loop by the operation command value ix. Therefore, even if an abnormality occurs in the detection signal, the hydraulic pump 1 will not be out of control, and highly reliable pump control can be performed.

On the other hand, in the second block 31B of the block 31, the basic command value io2 is calculated in the block 38B by using the same swash plate target position θo calculated in the block 30, and the command signal X2 corresponding to the basic command value io2 is generated. It is output to the proportional valve 53. That is, the swash plate 51 of the hydraulic pump 50 is controlled by the open loop so that the swash plate target position θo of the hydraulic pump 1 is used and the swash plate 2 of the hydraulic pump 1 is substantially tilted.

Then, in the preceding block 30 shown in FIG. 2, the differential pressure target discharge amount θΔp and the input limit target discharge amount θT are calculated, and the differential pressure target discharge amount θΔp is calculated as the input limit target discharge amount θT.
If it is smaller than the above, the differential pressure target discharge amount θΔp is selected as the swash plate target position θo, and if the input limit target discharge amount θT becomes smaller than the differential pressure target discharge amount θΔp, the input limit target discharge amount θT will be changed. Therefore, the swash plate positions of the hydraulic pumps 1 and 50 are controlled by the differential pressure target discharge amount θΔp while the input torque limit control is performed so that the total pump discharge amount does not exceed the input limit target discharge amount θT. Load sensing control is performed so that ΔP is maintained at the target differential pressure ΔPo.

The pressure oil from the hydraulic pumps 1 and 50 whose discharge amounts are controlled as described above merges in the discharge pipe line 3 and the hydraulic motors 5A and / or
Alternatively, it is supplied to the hydraulic cylinder 5B to drive them.

Therefore, according to the present embodiment, since the first and second hydraulic pumps 1 and 50 are provided, a sufficient amount of pressure oil is supplied even when the hydraulic motor 5A and the hydraulic cylinder 5B have large capacities. The second hydraulic pump 50 can also be driven appropriately, and the second hydraulic pump 50 is also controlled by using the swash plate target position θo of the first hydraulic pump 1. Therefore, the second hydraulic pump 50 can detect the swash plate position. It is not necessary to provide a displacement detector that operates, and the configuration of the pump control device can be simplified.

Further, the first hydraulic pump 1 can accurately control the swash plate position by feedback control, and when an abnormality occurs in the detection signal from the displacement detector 9, the first hydraulic pump 1 is switched to the open loop and is controlled. The hydraulic pump 1 will not be out of control when an abnormality occurs, and highly reliable control can be performed.

Another embodiment of the present invention will be described with reference to FIG. In the figure, the same members as those shown in FIG. 2 are designated by the same reference numerals.

In FIG. 3, the block 60 at the subsequent stage is configured such that the signal line 61 is branched on the output side of the amplifier 43A and the command signal X1 output to the solenoid proportional valve 11 is output to the solenoid proportional valve 53 as it is.

According to this embodiment, the second block 31B shown in FIG. 2 of the first embodiment is unnecessary, the calculation in the controller 10 is simplified, and the hydraulic pump 50 is also the swash plate of the hydraulic pump 1. Since the feedback control is performed using the displacement detector 9 that produces the position, the control accuracy is improved.

Still another embodiment of the present invention will be described with reference to FIGS. In the figure, the same members as those shown in FIGS. 1 and 2 are designated by the same reference numerals.

In FIG. 4, the pump control device 6 of this embodiment is
The solenoid proportional valve 53 provided for the pump regulator 54 of the embodiment is not provided, but instead the solenoid proportional valve 11 for the pump regulator 12 is shared, and the hydraulic signal of the solenoid proportional valve 11 is servo-controlled by the pilot line 70. It is configured to lead to the pressure receiving portion 57 of the control valve 56.

In FIG. 5, the block 71 at the latter stage of the controller 10
Is a configuration including only the first block 31A in FIG.

According to the present embodiment, since the solenoid proportional valve is also shared, the number of solenoid proportional valves used is reduced, and the configuration of the pump control device can be further simplified.

〔The invention's effect〕

According to the present invention, it is possible to cope with an increase in the capacity of the actuator and a part of the equipment of the pump control device can be shared, so that the configuration of the pump control device can be simplified.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a load sensing hydraulic drive system according to an embodiment of the present invention, FIG. 2 is a functional block diagram showing calculation contents of the controller shown in FIG. 1, and FIG.
FIG. 4 is a functional block diagram similar to FIG. 2 according to another embodiment of the present invention, FIG. 4 is a schematic view of a load sensing hydraulic drive system according to still another embodiment of the present invention, and FIG.
The figure is a functional block diagram similar to FIG. Explanation of symbols 1,50 …… hydraulic pump 2,51 …… swash plate (displacement volume changing means) 3 …… discharging pipe line 5A …… hydraulic motor 5B …… hydraulic cylinder 9 …… displacement detector 10 …… controller ( Control means) 11,53 …… Electromagnetic proportional valve 12,54 …… Pump regulator 31B …… Second block (operating means) 61 …… Signal line (operating means) 70 …… Pilot line (operating means) θo… … Swash plate target position (target displacement) io1, io2 …… Basic command value ix …… Operation command value X1, X2 …… Command signal

Claims (3)

[Claims] 1. At least a first hydraulic pump for supplying pressure oil to a plurality of hydraulic actuators to drive the hydraulic oil, detection means for detecting displacement of the first hydraulic pump, and the first hydraulic pump. Calculating a target displacement of the first hydraulic pump that holds the differential pressure between the discharge pressure of the first hydraulic pump and the maximum load pressure of the plurality of actuators at a predetermined value,
Control means for calculating a first operation command value from the target displacement and the displacement detected by the detecting means and outputting a first command signal corresponding to the first operation command value, and the control means based on the first command signal. A load sensing hydraulic drive device comprising: a first pump regulator that operates a displacement volume changing means of a first hydraulic pump to control a displacement volume of the first hydraulic pump; and a discharge pipe of the first hydraulic pump. A second hydraulic pump connected to the passage, a second pump regulator for controlling the displacement of the second hydraulic pump by operating the displacement of the second hydraulic pump, and the second pump regulator. The second pump regulator is controlled based on the target displacement of the first hydraulic pump to adjust the displacement of the second hydraulic pump to the first hydraulic pump. Operating means for controlling the displacement to be the same as the displacement of the hydraulic pump, the operating means calculating a second operation command value based on the target displacement of the first hydraulic pump obtained by the control means. Then, the load sensing hydraulic drive device is a means for outputting a second command signal corresponding thereto and controlling the second pump regulator by the second command signal. 2. A first hydraulic pump for supplying pressure oil to a plurality of hydraulic actuators to drive the hydraulic oil, a detection means for detecting displacement of the first hydraulic pump, and the first hydraulic pump. Calculating a target displacement of the first hydraulic pump that holds the differential pressure between the discharge pressure of the first hydraulic pump and the maximum load pressure of the plurality of actuators at a predetermined value,
Control means for calculating a first operation command value from the target displacement and the displacement detected by the detecting means and outputting a first command signal corresponding to the first operation command value, and the control means based on the first command signal. A load sensing hydraulic drive device comprising: a first pump regulator that operates a displacement volume changing means of a first hydraulic pump to control a displacement volume of the first hydraulic pump; and a discharge pipe of the first hydraulic pump. A second hydraulic pump connected to the passage, a second pump regulator for controlling the displacement of the second hydraulic pump by operating the displacement of the second hydraulic pump, and the second pump regulator. The second pump regulator is controlled based on the target displacement of the first hydraulic pump to adjust the displacement of the second hydraulic pump to the first hydraulic pump. Operating means for controlling the displacement to be the same as the displacement of the pump, the operating means outputs the first command signal obtained by the control means, and the second pump regulator A load sensing hydraulic drive system characterized in that it is a means for controlling by a command signal of. 3. At least a first hydraulic pump for supplying pressure oil to a plurality of hydraulic actuators to drive the hydraulic oil, a detection means for detecting displacement of the first hydraulic pump, and the first hydraulic pump. Calculating a target displacement of the first hydraulic pump that holds the differential pressure between the discharge pressure of the first hydraulic pump and the maximum load pressure of the plurality of actuators at a predetermined value,
Control means for calculating a first operation command value from the target displacement and the displacement detected by the detecting means and outputting a first command signal corresponding to the first operation command value, and the control means based on the first command signal. A load sensing hydraulic drive device comprising: a first pump regulator that operates a displacement volume changing means of a first hydraulic pump to control a displacement volume of the first hydraulic pump; and a discharge pipe of the first hydraulic pump. A second hydraulic pump connected to the passage, a second pump regulator for controlling the displacement of the second hydraulic pump by operating the displacement of the second hydraulic pump, and the second pump regulator. The second pump regulator is controlled based on the target displacement of the first hydraulic pump to adjust the displacement of the second hydraulic pump to the first hydraulic pump. And a solenoid valve for converting the first command signal into a hydraulic signal, and the first pump regulator is provided with the solenoid proportional valve. The hydraulic pressure signal from the solenoid proportional valve is used to control the hydraulic pressure signal from the electromagnetic proportional valve.
The load sensing hydraulic drive device, which is a means for guiding and controlling the pump regulator.