JPH08200304A - Buffer control device for hydraulic working machine - Google Patents

Abstract

PURPOSE: To provide a buffer control device for a hydraulic working machine which certainly absorbes shock of collision of a piston and a cover wall surface when the piston of a hydraulic cylinder approaches a process end without detecting moving direction, and does not deteriorate operability under the state that the piston leaves from the process end or the state that the piston is near the process end. CONSTITUTION: When piston displacement of cylinders 11 to 13 detected by displacement detectors 41 to 43 are near the process end, a control unit 10 computes a limit value corresponding to a displacement rate of the piston detected by the displacement detectors 41 to 43 based on data of response table where a displacement rate of the piston of the hydraulic cylinder read from a stored ROM is corresponded to a regulation value for limiting a pilot pressure. Driving signals corresponding to the regulation value are output to pressure reducing valves 17 to 19 (a, b) for controlling the pilot pressure supplied through manually operated valves 31 to 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the direction and flow rate of pressure oil flowing into and out of a hydraulic cylinder by supplying pilot pressures for pushing spools of a flow control valve in opposite directions in response to operation of an operating lever. The present invention relates to a shock absorber control device for a hydraulic working machine that controls a hydraulic cylinder to expand and contract to operate a working device such as a hydraulic excavator.

[0002]

2. Description of the Related Art When a hydraulic working machine, for example, a hydraulic excavator is operated with a maximum operation amount, when a moving cylinder reaches a stroke end without deceleration, the piston and the cover are impacted by a collision between the piston and the cover wall surface. May be damaged or make a loud noise. Further, the vibration of the shock is propagated to the cockpit to make the operator feel uncomfortable, and further, it hinders the operation. Therefore, various proposals have been made to reduce the impact at the stroke end of the hydraulic cylinder. For example, the actual development sho 58-13550
No. 6 discloses a cushion member including a cylindrical portion provided in the vicinity of the piston end surface in the cylinder and a tapered portion formed at the tip of the cylinder portion, and a cylinder cover for covering the cylinder. Disclosed is a cylinder cushion device having a cylindrical hole into which a portion is fitted, and a bottomed cushion chamber formed of a small diameter portion into which the tapered portion is fitted, the step being formed with a step in the inner part of the cylindrical hole. . According to this invention, since the flow of the pressure oil is throttled by the multistage fixed throttles formed near the stroke end of the cylinder, smooth deceleration of the piston can be realized and the impact at the stroke end of the cylinder can be mitigated. .

As a method of mitigating the impact at the stroke end of the cylinder without using a mechanical device, Japanese Patent Laid-Open No. 5-196004 discloses a cylinder position detection for detecting the position of the cylinder of the working machine in the stroke direction. Means, a moving direction detecting means for detecting the expansion and contraction moving direction of the cylinder, and a signal from both means, when the cylinder moves in the direction approaching the stroke end, it gradually changes from 1 to 0 depending on the deviation to the stroke end. A lever gain calculation means for calculating a gain G (0 <K <1) with respect to a lever signal of a lever device, a multiplication part for multiplying an operation command from the lever device by the gain G, and a cylinder by the output of this multiplication part. There is disclosed an automatic cushion control device having a cylinder control means for controlling the drive of the. According to the present invention, by attenuating the lever signal by the operation of the operator according to the distance to the stroke end of the cylinder, it is possible to reduce the impact when the cylinder is stopped without impairing the operability of the operator. .

[0004]

However, in the former technique, since the impact at the stroke end of the cylinder is mitigated by the fixed throttle formed inside the cylinder, the impact mitigation performance of the device depends on the machining precision of the fixed orifice. , It is difficult to get the desired performance. Further, since it is a mechanical shock absorbing mechanism, the shock absorbing characteristics cannot be changed. If the shock-absorbing performance of the cylinder of the hydraulic excavator is too strong, for example, even if you try to use the shock at the end of the stroke of the cylinder to wipe off the dirt adhering to the bucket, the cylinder will be decelerated rapidly at the end of the stroke. Such work cannot be performed. In the latter technique, a means for detecting the expansion / contraction movement direction of the cylinder is required.Because the speed is reduced regardless of the movement speed at the stroke end of the cylinder, the piston is positioned near the stroke end of the cylinder. The operability when performing the gradual work is impaired. The present invention has been made to solve the above problems in the prior art. When the piston of the hydraulic cylinder approaches the stroke end, the impact due to the collision between the piston and the cover wall surface is detected without detecting the moving direction. A shock absorber control device for hydraulic work machines that does not impair operability when the piston is separated from the stroke end or when performing fine operation work while the piston is located near the stroke end The purpose is to provide.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention is directed to a flow control valve for controlling the direction and flow rate of pressure oil flowing in and out of a hydraulic cylinder for operating a working device, and operation of an operating lever. Corresponding to the pilot pressure receiving portion of the flow control valve for supplying the pilot pressure for pushing the spool in the opposite direction to each other, and directly or indirectly detecting the displacement amount of the piston. Displacement detecting means, a pressure reducing means for reducing the pilot pressure supplied to the pilot pressure receiving portion by the pilot pressure supplying means, and a displacement amount of the piston detected by the displacement detecting means approaching the stroke end of the piston. When the pressure is reduced, the pilot pressure receiving portion of the flow control valve is controlled so as to displace the piston toward the stroke end by controlling the pressure reducing means. Mitigating the impact at the stroke end of the piston of the hydraulic cylinder by having pilot pressure limiting means that limits only the pilot pressure from the supplied pilot pressure supply means in accordance with the decrease in the distance from the stroke end of the piston. It was done like this.

[0006]

The pilot pressure supply means supplies pilot pressure for pushing the spool in one direction to a predetermined pilot pressure receiving portion of the flow control valve in response to the operation of the operation lever. As a result, the direction and flow rate of the pressure oil flowing in and out of the hydraulic cylinder is controlled by the flow rate control valve, and the working device operates. The displacement detecting means detects the displacement amount of the piston directly or indirectly, and when the detected displacement amount of the piston is close to the stroke end of the piston, the pilot pressure limiting means controls the pressure reducing means. , Limiting only the pilot pressure from the pilot pressure supply means, which is supplied to the pilot pressure receiving portion of the flow control valve so as to displace the piston toward the stroke end, in accordance with the decrease in the distance from the stroke end of the piston. .

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 is a hydraulic drive circuit diagram of a hydraulic excavator according to a first embodiment of the present invention, and FIG. 2 is a perspective view of the hydraulic excavator. First, in FIG. 2, I is an articulated front device for performing civil engineering construction work, and II is a front device I.
A vehicle body that supports and is movable at the front portion, 1 is a boom whose one end is rotatably supported by a vehicle body II, 2 is an arm whose one end is rotatably supported by the boom 1, and 3 is an arm whose rear end is rotatably supported. Two
A bucket 4 rotatably supported by a front device I
The upper revolving superstructure 5 which is capable of revolving while supporting the upper revolving superstructure 4 is a lower traveling structure which rotatably supports the upper revolving superstructure 4 and is capable of traveling. In FIG. 1, 6 is a hydraulic pump that is a supply source of operating pressure oil for driving an actuator, 7 is a pilot hydraulic pump that is a supply source of pilot pressure oil, 8 is an oil tank for collecting the operating pressure oil, and 10 is a microcomputer. And a control unit (pilot pressure limiting means) that outputs a control signal for controlling each actuator such as buffer control of each cylinder 11 to 13 according to an operation command by an input operation or detection information detected by various detectors. 1
1, 12 and 13 are a boom cylinder, an arm cylinder and a bucket cylinder for driving the boom 1, the arm 2 and the bucket 3, respectively, and 14 is an upper revolving structure 4.
A turning motor for turning the vehicle, 15 and 16 are left and right running motors, 17 (a, b), 18 (a, b), 1
9 (a, b) are pressure reducing valves provided in pilot hydraulic lines between respective manually operated valves and flow rate control valves, which will be described later, 21 to 26 are the cylinders 11 to 13 and the motors 14 to 16 described above. And a hydraulic pump 6 are connected in parallel to each other in a working hydraulic line.

Further, 27 and 28 are relief valves that open when the hydraulic pressures on the discharge side of the hydraulic pumps 6 and 7 exceed a predetermined value, and 29 is a buffer command switch for commanding buffer control operation. 31 to 36 are the flow control valves 21 to 2 according to the operation of the manual operation lever by the operator.
The pilot pressure oil for controlling the flow rate of the working pressure oil supplied to each of the cylinders 11 to 13 and each of the motors 14 to 16 by the switching operation of No. 6 is respectively flow rate control valves 21 to 26.
Manually operated valve for supplying the pilot receiver of the vehicle, 41
Numerals 43 to 43 are displacement detectors (cylinder stroke sensors) attached to the boom cylinder 11, the arm cylinder 12, and the bucket cylinder 13, respectively, for directly detecting their displacements as state quantities.

When the buffer command switch 29 is turned on,
The control unit 10 controls the pressure reducing valves 17 (a, b) to 19 (a, based on the displacement detection signals from the displacement detectors 41 to 43).
A drive signal for controlling the opening amount is output to b) to perform cylinder buffer control near the stroke end of each cylinder 11-13. In order to simplify the description of the embodiment, the operation will be described below by limiting the cylinder buffer control of the boom cylinder 11, but the cylinder buffer control of the other cylinders 12 and 13 is exactly the same. 3 and 4 are a boom cylinder cushioning control function block diagram of the control unit 10 and a boom cylinder cushioning control flowchart, respectively. The operation of the boom cylinder cushioning control will be described with reference to these figures.

The control unit 10 has ROMs 101a, 1
01b is built in, and the ROM 101a, 101
B is a boom cylinder 11 as shown in FIG.
The data of the correspondence table of the displacement X of the piston and the limiting pressures P _a and P _b for the pressure reducing valves 17a and 17b are stored. That is, the limiting pressure P _a is _a constant maximum limiting pressure P _max with respect to the displacement X close to the maximum value from the minimum value, but it rapidly decreases when approaching the maximum value of the displacement X, and at the maximum value of the displacement X. The minimum limiting pressure P _min is reached. On the other hand, the limiting pressure _Pb is the minimum limiting pressure _Pmin at the minimum value of the displacement X, and when the displacement X increases from the minimum value, the limiting pressure _Pb rapidly increases to a constant maximum limiting pressure _Pmax . In other words, limiting the piston of the boom cylinder 11 is moved closer to one or the other end of the cylinder pressure P _a,
The values of P _b are associated so as to decrease sharply.

The displacement detection signal x of the displacement X of the piston of the boom cylinder 11 detected by the displacement detector 41 is input to the comparison calculation circuits 102a and 102b of the control unit 10.
Then, the data of the limiting pressures P _a and P _b corresponding to the values of the displacement X read from the ROMs 101 a and 101 _b are compared, and the data of the corresponding limiting pressures P _a and P _b are output.
The data of these limiting pressures P _a and P _b is the maximum limiting pressure P _max.
Input to the switching circuits 103a and 103b together with the data of
According to the switching signal of the buffer command switch 29, any one of them is selected and output as pilot control pressures P _ao and P _bo signals. The pilot control pressures P _ao and P _bo signals are amplified by the amplifiers 104a and 104b, and the pressure reducing valve 17a,
It is supplied to the power receiving unit 17b. The pressure reducing valves 17a and 17b limit the pilot hydraulic pressure controlled by the manually operated valve 31 in accordance with the values of the pilot pressure control pressures P _ao and P _bo signals.
The pilot oil whose pressure is limited by the pressure reducing valves 17a and 17b is supplied to the pilot receiving portion of the flow control valve 21,
By moving the spool of the flow control valve 21 by the pilot pressure, the moving direction and speed of the piston of the boom cylinder 11 are controlled.

As shown in FIG. 4, the displacement detection signal x of the displacement X of the piston of the boom cylinder 11 detected by the displacement detector 41 is fetched into the control unit 10 at any time (S
1) The comparison calculation circuit 102a compares and compares the piston displacement X of the boom cylinder 11 read from the ROM 101a with the data in the corresponding table of the limiting pressure P _a for the pressure reducing valve 17a, and the corresponding limiting pressure P _a data is obtained. It is output (S2). Next, it is determined whether or not the buffer command switch 29 is in the ON state (S3), and if the result is Yes,
The value of the pilot control pressure P _ao is set as the limiting pressure P _a output from the comparison operation circuit 102a (S4), and if the determination result is No, the value of the pilot control pressure P _ao is set to a constant maximum limiting pressure P a.
_Set to _max (S5).

As described above, in this embodiment, when the piston of the boom cylinder 11 moves and approaches the stroke end, regardless of the pilot oil pressure controlled by the manual operation valve 31, the pilot receiving portion of the flow control valve 21 can be operated. The pressure of the supplied pilot oil is limited to the limiting pressure P _a , and further, as the piston of the boom cylinder 11 approaches its stroke end, it rapidly decreases to the minimum value P _min , and when it goes away from the stroke end, the pilot oil pressure is reduced. Since the pressure of the oil is not limited at all, the impact at the stroke end of the boom cylinder 11 (similarly to the other cylinders 12 and 13) is mitigated without damaging the operability, and the piston and the cover are damaged.
Alternatively, generation of large noise can be effectively prevented.

Further, since the impact relaxation is due to the pressure limitation of the pilot oil supplied to the pilot receiving portion of the flow control valve 21, even if the displacement X of the piston of the boom cylinder 11 is near its stroke end. , when the control pilot pressure by the manual operation valve 31 does not exceed a limit pressure P _a, that is, when the the at stroke end near the boom cylinder 11 is performing fine operation work, is not impaired operability. Of course, by switching the buffer command switch 29 to the off side when the cylinder buffer control is unnecessary,
By operating the manual operation valve 31 to control the hydraulic oil outflow direction and flow rate of the flow rate control valve 21, it is possible to perform normal boom cylinder control for switching the moving direction and speed of the boom cylinder 11.

Although the control unit 10 is composed of a microcomputer in this embodiment, it may be composed of a relatively simple analog circuit. A second embodiment of the present invention in which the control unit 10 is thus configured by an analog circuit will be described. FIG. 5 is a boom cylinder cushioning control function block diagram of the control unit 10 according to the second embodiment. The same reference numerals are given to the same or similar parts as those in the first embodiment, and the duplicated description will be omitted. The same applies to the following description. In this embodiment, the ROMs 101a and 101b and the switching circuit 1 in the first embodiment are used.
03a and 103b are analog function generating circuits 10 respectively.
5a, 105b and relays 106a, 106b.

Analog function generating circuits 105a and 105b
Is a circuit for generating a conversion analog function having the conversion characteristics described above when the displacement X of the piston of the boom cylinder 11 is given, and the displacement detector 4 is provided to the control unit 10.
Displacement X of the boom cylinder 11 piston detected by 1
When the displacement detection signal x of
Reference numerals a and 102b calculate and output the limiting pressures P _a and P _b corresponding to the value of the displacement X of the piston of the boom cylinder 11. The relays 106a and 106b are buffer command switches 29.
According to the intermittent operation of, the input signals of the limiting pressures P _a and P _{b and} the input signal of the maximum limiting pressure P _max are switched and output. Other configurations and operations are the same as those of the first embodiment. In the present embodiment, since the control unit 10 does not use a microcomputer, there is little risk of malfunction even in an environment with many noise signals, and stable cylinder buffer control can be performed.

In the above embodiment, each cylinder 11-13
Although the displacement of the piston is directly detected as the state quantity, the joint angle of the connecting portion of each of the cylinders 11 to 13 is detected to calculate the displacement of the piston of the cylinders 11 to 13 to perform the above-described cylinder buffer control. By doing so, the impact at the stroke end of each of the cylinders 11 to 13 can be mitigated. The third embodiment of the present invention having such a displacement detecting mechanism will be described below. 6 and 7 are a hydraulic drive circuit diagram of a hydraulic excavator and a perspective view of the hydraulic excavator according to the third embodiment, respectively. As shown in FIG. 7, in the present embodiment, an angle detection including a rotary potentiometer for detecting a rotation angle between the vehicle body II and the boom 1, the boom 1 and the arm 2, and the joints of the arm 2 and the bucket 3 is performed. Units 44, 45 and 46 are provided respectively. The angle signals of the joints detected by the angle detectors 44, 45, 46 are input to the control unit 10.

8 and 9 are a boom cylinder cushioning control function block diagram and a boom cylinder cushioning control flowchart of the control unit 10 according to the present embodiment, respectively. In this embodiment as well, the cylinder cushion control mechanism for only the boom cylinder 11 and its operation will be described, but the other cylinders 12, 13 are exactly the same. Angle detector 44
The angle signal for detecting the rotation angle θ ₁ between the vehicle body II and the boom 1 detected by the coordinate conversion circuit 10 of the control unit 10
The rotation angle θ that is input to 7 and is calculated in advance.
Coordinate conversion for converting ₁ into displacement X of the piston of boom cylinder 11 is performed. The displacement detection signal x output from the coordinate conversion circuit 107 is the comparison calculation circuits 102a and 102b.
Is input to the pressure reducing valves 17a, 17 and the pilot control pressures P _ao , P _bo signals follow the same procedure as in the first embodiment.
It is supplied to the power receiving unit of b. In the boom cylinder cushioning control operation, after the procedure S0 of converting the rotation angle θ ₁ into the displacement X of the piston of the boom cylinder 11 is first performed, the same operation as in the first embodiment is followed.

In the above embodiment, each cylinder 11-1
3. The switching operation of the flow rate control valves 21 to 26 for controlling the flow rate of the working pressure oil supplied to the motors 14 to 16 is the switching operation of the manually operated valves 31 to 36 of the pilot pressure oil supplied by the pilot hydraulic pump 7. However, the hydraulic pressure of the pilot pressure oil supplied to the pilot pressure receiving portion of the flow rate control valve may be indirectly controlled by operating the electric lever instead of being directly controlled by the manual operating valve. 10, 11 and 12 are a hydraulic drive circuit diagram of a hydraulic excavator according to a fourth embodiment of the present invention, a boom cylinder cushioning control function block diagram of the control unit 10, and a boom cylinder cushioning control flowchart, respectively. Is.

As shown in FIG. 10, each cylinder 11-
13, the pressure reducing valve 17 (a, a) in the oil pipeline between the pilot hydraulic pressure pump 7 and the pilot pressure receiving portion of the flow rate control valves 21 to 26 for controlling the flow rate of the operating pressure oil supplied to the motors 14 to 16, respectively. b) to 20 (a, b), 37 (a,
b) and 38 (a, b) are provided, but these pressure reducing valves 17 (a, b) to ... 38 (a, b) are the operation lever 5
It functions as a pressure control valve that controls the pilot pressure supplied to the pilot pressure receiving portions of the flow rate control valves 21 to 26 by the drive signal output from the control unit 10 according to the manipulated variable of 1 to 56. That is, when the operation levers 51 to 56 are operated by the operator, a drive signal corresponding to the operation amount of the operation levers 51 to 56 is transmitted from the control unit 10 to the pressure reducing valve 17.
(A, b) to ... 38 (a, b) are output, but when the displacement of each cylinder 11 to 13 reaches the vicinity of their stroke ends, a limit corresponding to the displacement is added to the drive signal. To be Next, as in the first embodiment, the boom cylinder 11
The operation of the present embodiment will be described by limiting to the cylinder buffer control of.

The displacement detection signal x of the displacement X of the piston of the boom cylinder 11 detected by the displacement detector 41 is input to the comparison calculation circuits 102a and 102b of the control unit 10.
Therefore, ROM 101A, limit pressure P _a corresponding to the value of the read displacement X from 101b, the reference data P _b is, the corresponding limit pressure P _a, the data of P _b is output.
The data of these limiting pressures P _a and P _b is the maximum limiting pressure P _max.
Input to the switching circuits 103a and 103b together with the data of
Either of them is selected according to the switching signal of the buffer command switch 29 and output to the minimum value selection circuits 108a and 108b. Command values P _ai and P _bi signals corresponding to the operation amount of the operating lever 51 are input to the minimum value selection circuits 108a and 108b, and the minimum value selection circuits 108a and 108b respectively command the limiting pressures P _a and P _b. The smaller value of the values P _ai and P _bi is selected and output as the pilot control pressures P _ao and P _bo signals.

Displacement of piston of boom cylinder 11 X
As shown in FIG. 12, the cylinder buffer control near the stroke end that gives the maximum value of S is the same as that of the first embodiment in the processes from step S1 to step S5, but thereafter, the limiting pressure P _a is the command value. It is determined whether or not it is smaller than P _ai (S6), and if the result is Yes, the pilot control pressure P _{ao is set} to the limiting pressure P.
_{If a} (S7) and the determination result is No, the pilot control pressure P _ao is set to the command value P _ai corresponding to the operation amount of the operation lever 51.
(S8). In this embodiment, the flow rate control of the flow rate control valves 21 to 26 is based on the operation of the operation levers 51 to 56, which are electric levers, so that the configuration of the pilot hydraulic circuit can be simplified.

[0023]

As described above, according to the first aspect of the invention, when the displacement amount of the piston detected by the displacement detecting means is close to the stroke end of the piston, the pressure reducing means is controlled. , The pilot pressure supplied to the pilot pressure receiving portion of the flow control valve so as to displace the piston toward the stroke end side is limited according to the decrease in the distance from the stroke end of the piston. When the piston of the cylinder approaches the stroke end, the impact due to the collision between the piston and the cover wall is reliably mitigated without detecting the movement direction of the cylinder, and when the piston is separated from the stroke end or the piston is at the stroke end. It is possible to provide a buffer control device that does not impair the operability when performing fine operation work in a state of being located in the vicinity.

According to the second aspect of the present invention, the data of the correspondence table in which the displacement amount of the piston of the hydraulic cylinder and the limit value for limiting the pilot pressure are associated with each other are stored in advance, and these data are read out to detect the displacement detecting means. Since the limit value corresponding to the displacement amount of the piston detected by is calculated, the accurate buffer control using a small computer becomes possible. According to the third aspect of the invention, the piston detected by the displacement detecting means in accordance with the function value generated by the function generating means for generating the function value for associating the displacement amount of the piston of the hydraulic cylinder with the limit value for limiting the pilot pressure. Since the limit value corresponding to the displacement amount of is calculated, the pilot pressure limiting means can be configured with a relatively simple electric circuit, and in this case, there is less risk of malfunction even in an environment with many noise signals. A stable cylinder buffer control can be performed.

According to the fourth aspect of the invention, the pilot pressure oil supply source and the operation lever for controlling the direction and flow rate of the pilot pressure oil supplied from the pilot pressure oil supply means constitute the pilot pressure oil supply means, and the operation lever and the flow rate. Since the pressure reducing means is constituted by the pressure reducing valve which is arranged on the way of the pilot hydraulic circuit connecting the pilot pressure receiving portion of the control valve and driven by the drive signal output from the pilot pressure limiting means, the pilot for driving the pressure reducing valve The circuit configuration of the pressure limiting means can be simplified. According to the invention of claim 5, the pressure reducing means is constituted by a pressure reducing valve arranged on the way of a pilot hydraulic circuit connecting the pilot pressure oil supply source and the pilot pressure receiving portion of the flow control valve, and the pilot pressure supplying means Is a pilot pressure oil supply source, a pressure reducing valve, and a pilot pressure limiting means for outputting a drive signal to the pressure reducing valve that limits the value of the command signal corresponding to the operation of the operating lever according to the decrease in the distance from the stroke end of the piston. Since it is configured by, the configuration of the pilot hydraulic circuit that connects the pilot pressure oil supply source and the pilot pressure receiving portion of the flow control valve can be simplified. According to the sixth aspect of the invention, the hydraulic work machine is a hydraulic excavator, and the displacement detection means calculates the displacement amount of the piston of the hydraulic cylinder based on the rotation angle that detects the joint angle of the work machine. Therefore, the displacement amount of the piston of the hydraulic cylinder in the hydraulic shovel can be detected relatively easily.

[Brief description of drawings]

FIG. 1 is a hydraulic drive circuit diagram of a hydraulic excavator according to a first embodiment of the present invention.

[Fig. 2] Similarly, a perspective view of the hydraulic excavator.

[Fig. 3] Similarly, a boom cylinder buffer control function block diagram of the control unit

[Fig. 4] Similarly, a flow chart of boom cylinder cushioning control

FIG. 5 is a block diagram of a boom cylinder cushioning control function of the control unit according to the second embodiment.

FIG. 6 is a hydraulic drive circuit diagram of a hydraulic excavator according to a third embodiment.

[Fig. 7] Similarly, a perspective view of the hydraulic excavator.

FIG. 8 is a block diagram of a boom cylinder cushioning control function of the control unit.

[Fig. 9] Similarly, a flow chart of boom cylinder cushioning control

FIG. 10 is a hydraulic drive circuit diagram of a hydraulic excavator according to a fourth embodiment of the present invention.

FIG. 11 is a block diagram of a boom cylinder cushioning control function of the control unit.

[Fig. 12] Similarly, a flow chart of boom cylinder cushioning control

[Explanation of symbols]

 1 Boom 2 Arm 3 Bucket 6 Hydraulic Pump 7 Pilot Hydraulic Pump 10 Control Unit 11 Boom Cylinder 12 Arm Cylinder 13 Bucket Cylinder 17-20, 37, 38 (a, b) Pressure Reducing Valve 21-26 Flow Control Valve 29 Buffer Command Switch 31 -36 Manual operation valve 41-43 Displacement detector 44-46 Angle detector 51-56 Operation lever 101 (a, b) ROM 102 (a, b) Comparison arithmetic circuit 105 (a, b) Analog function generation circuit 107 Coordinates Conversion circuit 108 (a, b) Minimum value selection circuit I Front device II Vehicle body

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 11, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

FIG.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[Figure 6]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Fujishima 650 Jinrachicho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura factory (72) Inventor Hiroyuki Adachi 650 Kintatecho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Ceremony Company Tsuchiura Factory

Claims (6)

[Claims] 1. A hydraulic cylinder that expands and contracts by pressure oil discharged from a hydraulic oil supply source to operate a working device, and a flow rate control valve that controls the direction and flow rate of the pressure oil that flows in and out of the hydraulic cylinder. Pilot pressure supply means for supplying pilot pressure for pushing the spools in mutually opposite directions to respective pilot pressure receiving portions of the flow control valve in response to the operation of the operation lever, and at the stroke end of the piston of the hydraulic cylinder. In a shock absorber damping control device for a hydraulic working machine, displacement detection means for directly or indirectly detecting the displacement amount of the piston, and pilot pressure supply means supply the pressure to the pilot pressure receiving portion. The pressure reducing means for reducing the pilot pressure respectively, and the displacement amount of the piston detected by the displacement detecting means When it is close to the stroke end of the piston, the pilot pressure supplied to the pilot pressure receiving portion of the flow control valve is controlled so as to control the pressure reducing means to displace the piston toward the stroke end. A shock-absorbing control device for a hydraulic working machine, comprising pilot pressure limiting means for limiting only the pilot pressure from the supply means in accordance with a decrease in the distance from the stroke end of the piston. 2. The pilot pressure limiting means stores, in advance, storage means for storing data of a correspondence table that associates the displacement amount of the piston of the hydraulic cylinder with the limit value for limiting the pilot pressure from the pilot pressure supply means, and the storage means. 3. A comparison calculation unit for calculating the limit value corresponding to the displacement amount of the piston detected by the displacement detection unit according to the read data of the correspondence table.
A buffer control device for the hydraulic working machine described. 3. The pilot pressure limiting means generates a function value associating a displacement amount of a piston of a hydraulic cylinder with a limit value for limiting the pilot pressure from the pilot pressure supply means, and the function generating means. 2. The buffer control device for a hydraulic working machine according to claim 1, further comprising a comparison calculation unit that calculates the limit value corresponding to the displacement amount of the piston detected by the displacement detection unit according to the function value. 4. The pilot pressure supply means comprises a pilot pressure oil supply source and an operating lever for controlling the direction and flow rate of the pilot pressure oil supplied from the pilot pressure oil supply source, and the pressure reducing means comprises the operation lever and the flow rate. The hydraulic work according to claim 1, wherein the hydraulic work is a pressure reducing valve which is arranged on the way of a pilot hydraulic circuit connecting the pilot pressure receiving portion of the control valve and which is driven by a drive signal output from the pilot pressure limiting means. Machine buffer control. 5. The pressure reducing means is a pressure reducing valve disposed on the way of a pilot hydraulic circuit connecting the pilot pressure oil supply source and the pilot pressure receiving portion of the flow control valve, and the pilot pressure supplying means is the pilot pressure oil supply source. And a pilot pressure limiting means for outputting to the pressure reducing valve a drive signal in which the value of the command signal corresponding to the operation of the operating lever and the value of the command signal corresponding to the operation of the operating lever are limited in accordance with a decrease in the distance between the stroke end of the piston and the stroke end The shock absorber control device for a hydraulic working machine according to claim 1, comprising: 6. The hydraulic work machine is a hydraulic excavator including a work machine including a boom, an arm, a bucket, and the like,
2. The shock-absorbing control device for a hydraulic work machine according to claim 1, wherein the displacement detection means calculates the amount of displacement of the piston of the hydraulic cylinder based on the rotation angle at which the joint angle of the work machine is detected.