JPH11270514A - Hydraulic control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control deceleration in an stroke end without necessitating a fluid pressure type shock absorber having a complex structure, and confirm setting pressure, and perform a warming-up operation of operation oil. SOLUTION: This hydraulic control device provided with a hydraulic pump 1, a direction selector valve 9, a hydraulic cylinder 5 controlled by the direction selector valve 9, a stroke rate detecting means 5a for detecting a stroke rate of the hydraulic cylinder 5, and a pilot line 10a for supplying pilot pressure to the direction selector valve 9 by operating operating levers 8a, 8b; is constituted by providing with a pilot pressure control part 4a formed in such a constitution that it is confirmed that a piston is positioned near a stroke end on the basis of the stroke rate outputted from the stroke rate detecting means 5a, and a pressure reduction output command of a pilot line is stopped when the operating levers 8a, 8b are operated to a stroke end side for a prescribed time or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for performing deceleration control when a piston of a hydraulic cylinder approaches a stroke end.

[0002]

2. Description of the Related Art Conventionally, when a hydraulic cylinder is lowered while a large load is applied, an inertial load becomes excessive, and a collision may occur when a piston in the hydraulic cylinder reaches a stroke end. When a collision occurs, the impact causes the hydraulic cylinder to vibrate and adversely affect peripheral devices such as attachments, devices, and piping attached to the hydraulic cylinder. Further, in some cases, the hydraulic cylinder may be damaged, or peripheral devices thereof may be damaged. Therefore, hydraulic cylinders usually have
A shock absorber is provided which can reduce a collision at a stroke end. As this type of shock absorber, a fluid pressure type and a sensor type are known.

[0003] The basic configuration of a hydraulic shock absorber is to reduce the flow rate of hydraulic oil discharged from the rod side of a hydraulic cylinder by an orifice to generate a back pressure at the stroke end side of the hydraulic cylinder to reduce the cylinder speed. It has become.

In such a hydraulic shock absorber, if the operating lever is continuously operated while the piston has reached the stroke end, a relief valve for maintaining a constant circuit pressure is operated, and excess hydraulic oil is stored in a tank. Is returned to. Therefore, in this state, the operator can check the set pressure of the hydraulic circuit and perform a so-called warm-up operation in which the operating oil temperature is increased at the start of operation.

On the other hand, the configuration of the sensor type shock absorber is such that the stroke amount is detected by a position sensor attached to the hydraulic cylinder, and when the piston reaches the vicinity of the stroke end, the pressure in the pilot line is reduced, and the main spool of the switching control valve is removed. The cylinder is returned to the neutral position, thereby reducing the cylinder speed.

[0006]

Among the above-mentioned prior arts, the fluid pressure type shock absorber has a problem that the cost of the hydraulic device is increased due to its complicated structure. In this case, since the load applied to the hydraulic cylinder is larger than the design load, there is a problem that insufficient deceleration occurs at the stroke end.

On the other hand, the sensor type has an advantage that the cost of the hydraulic device can be reduced because the configuration is simpler than that of the fluid pressure type shock absorber. However, when the sensor type determines that the piston approaches the stroke end based on the detected stroke amount,
The controller performs control to return the main spool of the switching control valve to the neutral position. Therefore, when the pump pressure of the hydraulic circuit stops rising, it is impossible to confirm the set pressure of the hydraulic circuit and perform the warm-up operation of the hydraulic oil, which is possible with the above-mentioned fluid pressure type shock absorber.

The present invention has been made in view of the above circumstances, and can reduce the cylinder speed at the stroke end without requiring a fluid pressure type shock absorber having a complicated structure. And a hydraulic control device capable of performing a warm-up operation of hydraulic oil.

[0009]

SUMMARY OF THE INVENTION The present invention provides a hydraulic pump for delivering hydraulic oil by driving a prime mover, a directional control valve for controlling a flow rate and a direction of hydraulic oil sent from the hydraulic pump, and a directional switching valve. A hydraulic cylinder operated by hydraulic oil controlled by a valve, stroke amount detecting means for detecting a stroke amount of the hydraulic cylinder, and a pilot line for supplying a pilot pressure to the direction control valve by operating an operating body. The hydraulic control device having the function of recognizing that the piston is located near the stroke end based on the stroke amount output from the stroke amount detecting means, and operating the operating body to the stroke end side for a predetermined time or more. The pressure reduction command to reduce the pilot pressure near the stroke end for the pilot line A hydraulic control device including a pilots pressure control means.

In the present invention, it is preferable that the pilot pressure control means determines that a range obtained by adding a stroke amount measurement error to a theoretical stroke amount at the stroke end is near the stroke end.

In the present invention, it is preferable that the predetermined time is set to a time sufficient to operate by a measurement error in the detected stroke amount.

According to the present invention, when the piston of the hydraulic cylinder approaches the stroke end, normal deceleration control is performed. Specifically, a pressure reduction command is output to the pilot line, and for example, the flow rate of the pressure reduction valve provided between the operating body and the flow rate control valve is reduced, and the cylinder speed is reduced.
The pilot pressure control means constantly monitors the stroke amount output from the stroke amount detection means, and when the piston of the hydraulic cylinder is located near the stroke end, whether the operating body is still operated to the stroke end side for a predetermined time or more. Judge whether or not. If it has been operated on the stroke end side for a predetermined time or more, the pilot pressure control means stops the pressure reduction command of the pilot line. This allows the operator to move the main spool of the flow control valve in a direction to drive the hydraulic cylinder toward the stroke end.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 shows a hydraulic control device according to the present invention. In the figure, reference numeral 1 denotes a hydraulic pump for supplying hydraulic oil for driving a hydraulic cylinder, 2
Reference numeral denotes a pilot hydraulic pump that supplies pilot pressure, and reference numeral 3 denotes an oil tank that collects hydraulic oil. Reference numeral 4 denotes a controller constituted by a microcomputer, which receives an operation command output from an operation lever and a detection signal detected by each detection unit, and controls each cylinder, specifically a boom cylinder 5 for driving a boom, and an arm. The operation of the arm cylinder 6 to be driven and the operation of the offset cylinder 7 for performing offset are controlled, and the cylinder speed is reduced at the stroke end.

A pressure reducing valve 1 is provided on a pilot line 10a between the boom raising operation lever 8a and the boom flow control valve 9.
The operation amount of the boom raising operation lever 8a is detected by a boom raising operation amount detection sensor 12a. On the other hand, the boom lowering operation lever (operation body) 8
Pilot line 1 between b and boom flow control valve 9
0b is provided with a pressure reducing valve 11b, and the operation amount of the boom lowering operation lever 8b is controlled by the boom lowering operation amount detecting sensor 1b.
2b. The operation levers can be regarded as operation members, and the flow control valves can be regarded as direction switching valves.

A pressure reducing valve 16a is provided in a pilot line 15a between the arm pulling operation lever 13a and the arm flow control valve 14, and the operation amount of the arm pulling operation lever 13a is determined by an arm pulling operation amount detecting sensor. 17a
Is detected by Arm push operation lever 13b
Line 1 between the arm and the flow control valve 14 for the arm
5b is provided with a pressure reducing valve 16b, and the operation amount of the arm pushing operation lever 13b is detected by an arm pushing operation amount detection sensor 17b.

A pilot line 2 between the offset pressure operation pedal 18a and the offset flow control valve 19
0a is provided with a pressure reducing valve 21a, and the operation amount of the offset pressure operation pedal 18a is detected by an offset operation amount detection sensor 22a. A pressure reducing valve 21b is provided in a pilot line 20b between the offset left operation pedal 18b and the offset flow control valve 19, and the operation amount of the offset right operation pedal 18b is detected by an offset operation amount detection sensor 22b.

Each of the operation amount detection sensors 12a, 12 described above
The detection signals output from b, 17a, 17b, 22a and 22b are given to the controller 4.

The stroke amount of the boom cylinder 5 is detected by the boom stroke detecting means 5a, the stroke amount of the arm cylinder 6 is detected by the arm stroke detecting means 6a, and the stroke amount of the offset cylinder 7 is detected by the offset detecting means 7a. , Detection signals are provided to the controller 4. It should be noted that each of the detection means 5a, 6
Reference numerals a and 7a each include a potentiometer (not shown), function as stroke detection means, and output an angle sensor signal (detection signal) corresponding to the operating angle.

FIGS. 2 to 4 show the angle sensor signals output from the respective detecting means. First, FIG. 2 shows the relationship between the boom operating angle and the angle sensor signal output from the boom stroke detecting means 5a to which the boom is attached. At the end of the boom raising stroke, the boom operation angle is 28 °, and the angle sensor signal output at that time is 0.8V.

FIG. 3 shows the relationship between the arm operating angle and the angle sensor signal output from a potentiometer provided on the arm. In the arm pushing operation, the arm pushing operation angle at the end of the stroke is 26 °, and the angle sensor signal output at that time is 0.72.
V. In the arm pulling operation, the arm pulling operation angle at the end of the stroke is 143 °, and the angle sensor signal output at that time is 3.99V.

FIG. 4 shows the relationship between the offset operation angle and the angle sensor signal in the potentiometer provided at the offset. In the offset operation, the offset operation angle at the end of the stroke is 49 °, and the angle sensor signal output at that time is 1.36.
V.

As described above, the angle sensor signal corresponding to the operating angle can be theoretically determined from the above-mentioned characteristic diagram.

On the other hand, in the ROM 4a of the controller 4,
Data defining a pressure reducing command for the pressure reducing valves 11a and 11b in accordance with the displacement of the piston in the boom cylinder 5 is stored, and a pressure reducing command is output to the pressure reducing valve 11 as the piston of the boom cylinder 5 approaches the stroke end. It has become. Similarly, the arm cylinder 6 and the offset cylinder 7 output a pressure reducing command to the pressure reducing valve as the piston approaches the stroke end.

Specifically, a pilot pressure whose pressure is limited by the pressure reducing valves 11a and 11b is supplied to a pilot pressure supply section of the flow control valve 9, and the spool of the flow control valve 9 is moved by the pilot pressure. Boom cylinder 5
The movement of the piston approaching the stroke end is reduced. Similarly, for the arm cylinder 6 and the offset cylinder 7, the movement of the piston approaching the stroke end is reduced.

A pilot pressure control section (pilot pressure control means) 4b of the controller 4 constantly monitors the stroke amount output from the arm stroke detection means 5a, the boom stroke detection means 6a, and the offset detection means. When the piston No. 5 is located near the stroke end, it is determined whether or not the operation lever 8a or 8b is still operated to the stroke end side for a predetermined time or more.
Stop the pressure reduction command.

The operation of the pilot pressure control section 4b will be described below with reference to the flowchart shown in FIG. In the following description, the boom cylinder 5 will be described as a representative.

First, the pilot pressure control section 4b determines whether or not the position of the piston in the boom cylinder 5 is near the stroke end based on the stroke amount output from the stroke amount detecting means 5a (step S).
1).

In the vicinity of the stroke end, the threshold is a certain amount before the stroke amount which theoretically becomes the stroke end, and the threshold is determined to be near the stroke end by exceeding the threshold. That is, theoretically, when the angle sensor signal is 0.8 V (see FIG. 2), the operation angle of the boom cylinder 5 becomes 28 °, which means that the stroke end has been reached. The angle sensor signal includes a measurement error. Therefore, for example, if the measurement error is ± 0.2 V,
When the piston reaches the stroke end within the range obtained by adding the stroke measurement error to the theoretical stroke end, that is, 0.8V ± 0.2V, in other words, in the range of the angle sensor signal 0.6V to 1.0V. Could be.

Therefore, in this embodiment, when the detected value of the angle sensor signal exceeds the upper limit of the error range, that is, 1.0 V, it is considered that the stroke end is near.

Next, the pilot pressure control section 4b controls the boom raising operation lever 8a or the boom lowering operation lever 8b based on the lever operation amount signals output from the boom raising operation amount sensor 12a and the boom lowering operation amount sensor 12b.
It is determined whether is still operated to the stroke end side (step S2).

If Yes in step S2, the timer starts counting (step S3). Note that the timer measures the time by software using the internal clock of the controller 4.

If No in step S4, the process returns to the start and repeats the processes in steps S1 to S3.
Integrate the time measured by the timer.

If Yes in step S4, that is, if the accumulated time exceeds the predetermined value Tsec, the pilot pressure control section 4b stops the pressure reducing command output to the pressure reducing valve 11a (step S5). Thereby,
The operator can operate the boom raising operation lever 8a or the boom lowering operation lever 8b, and can move the spool of the flow control valve 9 to the stroke end.

When the value of the detected angle sensor signal is, for example, 1.0 V, the predetermined value T is calculated based on the theoretical stroke end from 1.2 V obtained by adding the plus-side measurement error 0.2 V. The time is set to a time sufficient to fall below 0.8 V shown. That is, when the piston has not actually reached the stroke end, it is confirmed that the operation is still performed on the stroke end side.

In steps S1 and S2, N
If it is o, the time measurement of the timer is initialized and step S1
Return to

By performing such control, it is possible to control the deceleration of the hydraulic cylinder when the hydraulic cylinder reaches the stroke end without providing a hydraulic shock absorber, and to respond to the demand of the operator. As a result, the pressure reduction command to the pressure reduction valve can be stopped.

Further, in the above embodiment, the hydraulic control device of the present invention is provided with a boom cylinder, an arm cylinder,
Although an example in which the invention is applied to an offset cylinder has been described, the invention is not limited to this, and the invention can be applied to a hydraulic cylinder of an arbitrary hydraulic control device.

[0038]

As is apparent from the above description,
According to the first aspect of the present invention, it is possible to reduce the cylinder speed at the stroke end without requiring a fluid pressure type shock absorber having a complicated structure, and to issue a pressure reducing command to the pressure reducing valve according to an operator's request. Since the main spool of the flow switching valve can be stopped and moved to the stroke end side, the set pressure can be confirmed and the operation oil can be warmed up.

According to the second aspect of the present invention, since the stroke end is recognized in consideration of the measurement error, there is an advantage that an impact due to a sudden stop does not occur. Claim 3
According to the present invention, the pilot pressure can be reduced near the stroke end by confirming that the operation is being performed on the stroke end side.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a hydraulic control device according to the present invention.

FIG. 2 is a graph illustrating a stroke end in a boom raising cylinder.

FIG. 3 is a graph illustrating a stroke end in an arm cylinder.

FIG. 4 is a graph illustrating a stroke end in an offset cylinder.

FIG. 5 is a flowchart showing a control operation of a controller 4 shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 hydraulic pump 2 pilot hydraulic pump 3 oil tank 4 controller 5 boom cylinder 6 arm cylinder 7 offset cylinder 9 boom flow control valve 8a boom raising operation lever 8a 10a pilot line 11a pressure reducing valve 12a boom raising operation amount detection sensor

Claims (3)

[Claims] 1. A hydraulic pump for sending hydraulic oil by driving a prime mover, a directional control valve for controlling the flow rate and direction of hydraulic oil sent from the hydraulic pump, and a hydraulic oil controlled by the directional switch valve. An operating hydraulic cylinder, a stroke amount detecting means for detecting a stroke amount of the hydraulic cylinder, and a pilot line for supplying a pilot pressure to the directional control valve by operating an operating body;
In the hydraulic control device having the above, it is recognized that the piston is located near the stroke end based on the stroke amount output from the stroke amount detecting means, and the operating body is operated to the stroke end side for a predetermined time or more. And a pilot pressure control means for stopping a pressure reduction output command for reducing the pilot pressure in the vicinity of the stroke end with respect to the pilot line. 2. The hydraulic control device according to claim 1, wherein the pilot pressure control means determines that a range obtained by adding a stroke measurement error to a theoretical stroke end is near the stroke end. 3. The hydraulic control device according to claim 2, wherein the predetermined time is set to a time sufficient to operate by a measurement error in the detected stroke amount.