JP2688968B2 - Hydraulic circuit for boom cylinder of work equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic circuit for a boom cylinder of a working device provided in a construction machine such as a hydraulic excavator, and more particularly, to a sudden stop while the boom is being lowered. The present invention relates to a boom cylinder hydraulic circuit for a working device capable of preventing the boom from repeatedly swinging up and down.

[Conventional technology]

6 to 8 show a hydraulic circuit for a boom cylinder of a working device according to the prior art.

In the figure, 1 is a lower traveling body of a hydraulic excavator, 2 is an upper revolving body mounted on the lower traveling body 1 so as to be rotatable, and the upper revolving body 2 constitutes a working machine body together with the lower traveling body 1. , And has a revolving frame 2C having a frame structure together with the brackets 2A and 2B shown in FIG. The upper revolving structure 2 is provided with a machine room 3, a driver's cab 4, and a counterweight 5 located on the revolving frame 2C.

Reference numeral 6 denotes a working device provided on the front part of the upper revolving structure 2 so as to be able to move up and down. The working device 6 is, as shown in FIG. An arm 8 rotatably pin-connected to the tip of the boom 7.
And a bucket 9 as a working tool that is rotatably pin-coupled to the distal end side of the arm 8, and is rotatably provided between the boom 7 and the bracket 2B to raise and lower the boom 7. As shown in Fig. 7, the rod side oil chamber 10A and the bottom side oil chamber 1
It is composed of a boom cylinder 10 having 0B, an arm cylinder 11 for rotating the boom 8, and a bucket cylinder 12 for rotating the bucket 9.

Next, the hydraulic circuit for the boom cylinder 10 will be described with reference to FIG.

In the figure, reference numeral 13 denotes a hydraulic pump which is provided in the machine room 3 and constitutes a hydraulic power source together with a tank 14;
3 shows a pair of main lines connecting between the tank 14 and the boom cylinder 10, and each of the main lines 15 is provided with a directional switching valve 16 to be described later.
Is connected to the rod-side oil chamber 10A and the bottom-side oil chamber 10B of the boom cylinder 10 at the rod-side conduit 15
A, bottom side conduit 15B.

Reference numeral 16 denotes a directional control valve provided in the middle of each main pipe line 15. The directional control valve 16 is operated from the neutral position (a) to the left by manually operating the operating lever 16A provided in the cab 4. By switching to the right switching positions (b) and (c), the pressure oil from the hydraulic pump 13 is supplied to and discharged from the rod side oil chamber 10A and the bottom side oil chamber 10B of the boom cylinder 10. 17 branches off from the pipes 15A and 15B to form a tank 14
The tank lines connected to the side, 18 and 18 indicate check valves as supply valves provided in the middle of the line portions 17A and 17B of the tank line 17, and each check valve 18 is connected to the line 15A, When the pressure in the tank 15B becomes equal to or less than the tank pressure, the valve is opened, and the pipes 15A and 15B are replenished with the oil liquid in the tank 14.
The inside of 15A and 15B is prevented from becoming negative pressure.

In the prior art configured as described above, the operation lever 16A
When the directional control valve 16 is manually operated to switch the directional control valve 16 from the neutral position (a) to the switch position (b), the hydraulic oil from the hydraulic pump 13 is supplied into the rod-side oil chamber 10A of the boom cylinder 10 and the bottom The pressure oil in the side oil chamber 10B is discharged to the tank 14 side, and the rod 10C of the boom cylinder 10 contracts to
Is upset. When the direction switching valve 16 is switched to the switching position (C), the pressure oil from the hydraulic pump 13 is supplied into the bottom side oil chamber 10B, and the pressure oil in the rod side oil chamber 10A is supplied to the tank.
It is discharged to the 14 side, and the boom 7 is the rod of the boom cylinder 10.
Elevated by 10C stretching. When the directional control valve 7 is returned to the neutral position (a), the hydraulic pump
Since the supply of the pressure oil from 13 stops, the boom cylinder 10 stops and the boom 7 also stops.

[Problems to be solved by the invention]

However, in the above-described conventional technique, the boom cylinder 10 is moved downward, and while the boom 7 is being rapidly lowered, the directional control valve 7 is rapidly returned to the neutral position (a), and the boom cylinder When the boom 10 is stopped, the boom 7 receives an inertia force F based on the weight of the entire working device 6 such as the arm 8 and the bucket 9 in the direction of the arrow in FIG. The pressure oil contained in the chamber 10B is temporarily compressed by the inertial force F, and the pressure in the bottom side oil chamber 10B is between the points A and B as indicated by the characteristic line 19 shown in FIG. The pressure suddenly rises, and then the rod 10C and the piston 10D of the boom cylinder 10 are pushed upward by this pressure to lower the pressure. This pressure rises and falls as shown by the characteristic line 19 due to the weight of the entire working device 6. It is gradually attenuated while repeating.

Therefore, in the prior art, when the boom 7 is stopped in the middle of abrupt lowering, the boom 7 has a characteristic line shown in FIG.
By repeating swinging up and down as shown by 20, excessive vibration is applied to the boom 7, the boom cylinder 10 and the like, the connecting pins and the like are quickly worn, and the bucket 9 and the like are quickly positioned. However, there is a drawback that the work efficiency is lowered.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and the present invention can prevent the boom from repeatedly swinging upward and downward when the boom is suddenly lowered and stopped, thereby improving work efficiency. The hydraulic circuit for the boom cylinder of the working device is provided.

[Means for solving the problem]

The features of the configuration adopted by the present invention to solve the above-mentioned problems are that a neutral position detection switch that detects that the directional control valve is in the neutral position, a bottom side oil chamber of the boom cylinder, and the directional control valve are provided. Located in the middle of the main conduit communicating with the bottom side oil chamber, normally closed solenoid valve, based on the signal from the neutral position detection switch,
There is provided a control device for opening the solenoid valve for a predetermined time after the directional control valve is returned to the neutral position for a predetermined time to open the bottom side pressure of the boom cylinder to a low pressure side.

Further, the solenoid valve may be provided in the middle of the pipeline connecting the pair of main pipelines, or may be provided in the middle of the pipeline connecting the main pipeline communicating with the bottom side oil chamber and the tank. Good. A flow rate control valve may be provided in series with the solenoid valve in the middle of the pipeline.

Further, it is preferable that the valve opening timing and the valve opening time of the solenoid valve are set to be within a quarter of the natural vibration cycle of the work device.

[Action]

With the above configuration, when the directional control valve is returned to the neutral position in order to stop the boom while it is being suddenly lowered, the control device receives a signal from the neutral position detection switch for a certain period of time, for example, the natural vibration of the working device. After the time corresponding to 1/4 cycle of the cycle, the solenoid valve is opened for a predetermined time to release the pressure on the bottom side of the boom cylinder to the low pressure side such as the main pipe line on the rod side. It is possible to effectively prevent the pressure from being lowered and the pressure being repeatedly increased and decreased.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 5. In the embodiment, the same components as those in the prior art shown in FIGS.
The description is omitted.

FIGS. 1 to 4 show a first embodiment of the present invention.

In the figure, reference numeral 21 denotes a neutral position detection switch provided on the base end side of the operation lever 16A, etc., and the detection switch 21 is, for example, a detection signal when the direction switching valve 16 is at the neutral position (a) as shown in the figure. And an OFF signal as a detection signal when the directional control valve 16 is slightly switched from the neutral position (B) to the switching position (B) and (C) by manual operation of the operation lever 16A. It is supposed to do.

Reference numeral 22 denotes a solenoid valve provided in the middle of a pipe line 23 connecting the rod side pipe line 15A and the bottom side pipe line 15B. The solenoid valve 22 is closed by an operation signal from a controller 24, which will be described later. ) To the valve open position (b), and the spring 22A closes the valve closed position (b) while the output of the operation signal is stopped.
As shown in the figure, it is automatically returned.

Reference numeral 24 denotes a controller as a control device configured by a microcomputer or the like, the input side of the controller 24 is connected to the neutral position detection switch 21, and the output side is connected to the solenoid valve 22. Then, the controller 24 stores a timer and the like in the memory circuit together with the program shown in FIG. 2 so as to open / close the solenoid valve 22. Further, in the storage circuit of the controller 24, in the storage area, a counting time corresponding to a fixed time t ₁ second for determining the opening timing of the solenoid valve 22 and a predetermined time for determining the opening time of the solenoid valve 22. The counting time corresponding to t ₂ seconds is stored (see FIG. 3).

Here, the valve opening timing and valve opening time of the solenoid valve 22 are set based on the natural vibration period T of the working device 6 shown in FIG. Time is t
_One second is set to a time substantially corresponding to the quarter cycle T / 4, and the valve opening time t ₂ seconds is set to a time slightly shorter than the quarter cycle T / 4. The natural vibration characteristic of the work device 6 shown in FIG. 4 is the vibration characteristic line of the boom 7 when the boom 7 is about to be stopped at the point A shown in FIG.
Substantially corresponds to 20. Further, since the natural vibration characteristic does not change due to the speed or the like when the working device 6 is operating, and is the natural vibration characteristic when the working device 6 is stopped, the valve opening timing t ₁ Seconds, the valve opening time t ₂ seconds is based on the quarter period T / 4 of the natural vibration period T,
It can be set as a fixed time, and a rocking prevention effect described later can be given.

The boom cylinder hydraulic circuit according to the present embodiment has the above-described configuration, and its basic operation is not particularly different from that of the prior art.

Therefore, the opening / closing valve processing operation of the solenoid valve 22 by the controller 24 will be described with reference to FIG.

First, when the processing operation is started, the signal from the neutral position detection switch 21 is read in step 1 and step 2
Then, it is determined whether or not the directional control valve 16 has been returned to the neutral position (a). When it is determined to be "NO" in step 2, the detection signal from the detection switch 21 is OFF (the third
(Refer to the drawing), the directional control valve 16 is switched from the neutral position (a) to the switching positions (b) and (c), so step 3
Then, the output of the actuation signal to the solenoid valve 22 is continued to be stopped, and the processing from step 1 onward is continued.

Next, when “YES” is determined in step 2,
The directional control valve 16 is returned to the neutral position (a) and the detection switch
Since the detection signal from 21 is ON, the timer t is reset to zero in step 4, and the detection switch 21 is reset in step 5.
It is judged whether the detection signal from is ON and the constant valve opening timing t ₁ seconds has been reached, and when t ₁ seconds has elapsed, the process proceeds to step 6 and a predetermined time t ₂ seconds as shown in FIG. Only, an operation signal is output to the solenoid valve 22, the solenoid valve 22 is switched from the closed position (a) to the open position (b), and the valve is opened for t ₂ seconds.

Thereby, for example, the directional control valve 16 is set to the switching position (b).
From abruptly to the neutral position (a), and when the boom 7 is about to be lowered suddenly and stopped, the solenoid valve 22 is opened for a predetermined time t ₂ seconds after t ₁ second, so that the boom cylinder 10 At the moment when the bottom side pressure in the bottom side conduit 15B communicating with the bottom side oil chamber 10B turns from rising to falling as indicated by the characteristic line 19 shown in FIG. It can be opened from the side pipe line 15B to the rod side pipe line 15A via the pipe line 23, and the bottom side pressure can be rapidly reduced as indicated by a characteristic line 25 shown by a dotted line in FIG.

That is, the direction t ₁ seconds which is the opening timing of the solenoid valve 22 switching valve 16
Is returned to the neutral position (a) at the point A shown in FIG.
Since it is set as a time t ₁ second corresponding to a quarter period T / 4 of the natural vibration period T of the working device 6 shown in FIG. With B, the bottom side pressure can be released to the low pressure side such as the rod side pipeline 15A,
This bottom side pressure can be rapidly reduced. And the solenoid valve
By setting the valve opening time of 22 to t ₂ seconds, the bottom side pressure is reduced to the pressure level of the point C as shown by the characteristic line 25 shown by the dotted line in FIG. Pipe line 15A
The solenoid valve 22 can be closed again when and become almost the same pressure (see step 3), and the boom 7 repeats swinging up and down as shown by the characteristic line 20 shown in FIG. It can be prevented.

Even when the direction switching valve 16 is returned from the switching position (C) to the neutral position (A) and the boom 7 is stopped in the middle of a sudden rise, the solenoid valve 22 is opened in step 6, but in this case By incorporating a check valve 22B or the like in the solenoid valve 22, it is possible to prevent pressure oil from flowing in the opposite direction from the rod side conduit 15A to the bottom side conduit 15B.

Thus, according to the present embodiment, when it is attempted to stop the boom 7 while it is being rapidly lowered, the directional control valve 16 is returned to the neutral position (a) and a predetermined time t ₁ second has elapsed, for example, the eighth position. At the point B in the figure, the solenoid valve 22 is opened for t ₂ seconds to open the bottom side pressure to the rod side conduit 15A. Therefore, this bottom side pressure is indicated by the characteristic line 25 shown in FIG. As described above, the bottom side pressure can be maintained at the pressure level at the point C by rapidly reducing the pressure between the points B and C, and the boom 7 can be stably stabilized as the characteristic line 26 shown by the dotted line in FIG. It can be stopped and the bucket 9 can be positioned quickly,
Various effects such as the improvement of work efficiency can be achieved.

Next, FIG. 5 shows a second embodiment of the present invention. In this embodiment, the same components as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted. The feature of this embodiment is that the flow control valve 31 is connected in series with the solenoid valve 22 in the middle of the pipeline 23.
Has been established. Here, the flow control valve 31 includes a spring 31
The solenoid valve 22 is normally placed in the valve open position (b) by A, the solenoid valve 22 is switched to the valve open position (b), and a large amount of fluid flows from the bottom side conduit 15B to the rod side conduit 15A via the conduit 23. Pressure oil is squeezed 3
When circulating 2, the valve is switched to the valve closed position (a) side against the spring 31A to control the flow rate of the pressure oil flowing through the throttle 32.

Thus, in this embodiment configured as described above, it is possible to obtain substantially the same operation and effect as in the first embodiment. However, particularly in this embodiment, the flow control valve 31 is provided in the middle of the pipeline 23. Therefore, when the solenoid valve 22 is opened, the bottom side oil chamber
It is possible to prevent pressure oil in the 10B and bottom side conduits 15B from flowing out to the rod side conduit 15A side excessively, and it is possible to limit the excessive lowering (down) of the boom 7 and improve safety. There are various effects such as being possible.

In each of the above-described embodiments, the solenoid valve 22 is provided in the middle of the pipe line 23 that connects the rod side pipe line 15A and the bottom side pipe line 15B. However, instead of this, in FIG. The solenoid valve 22 may be provided in the middle of the pipe line 27 connecting the bottom side pipe line 15B and the tank pipe line 17 shown by the two-dot chain line.

Further, the flow control valve 31 and the throttle described in the second embodiment are
32 may be provided in series with the solenoid valve 22 in the middle of the pipe 27. When the solenoid valve 22 is provided in the pipe line 27,
Even when the flow control valve 31 and the like are provided together with the solenoid valve 22, the bottom side pressure can be released to the tank line 17 to the low pressure side, and the boom 7
Can be stopped stably.

Further, in each of the above-described embodiments, the hydraulic excavator has been described as an example, but the present invention is not limited to this, and is used for a working device such as a hydraulic crane in which the boom is raised and lowered by the boom cylinder. It is also applicable to the hydraulic circuit for boom cylinders.

Further, the neutral position detection switch 21 may be provided at the end of the direction switching valve 16 or the like.

〔The invention's effect〕

As described in detail above, according to the present invention, since the directional control valve is returned to the neutral position and the solenoid valve is opened for a predetermined time after a fixed time, it is stopped while the boom is being rapidly lowered. Even when trying to do so, when the bottom pressure of the boom cylinder changes from rising to falling, the bottom pressure can be released to the low pressure side, preventing the boom from repeatedly swinging up and down and vibrating. Therefore, the boom can be stably stopped, the bucket can be positioned quickly, and the work efficiency can be improved. Also,
If the flow control valve is provided in series with the solenoid valve, it is possible to restrict the boom from being excessively lowered (moved down) due to the opening of the solenoid valve, and various effects such as improving safety can be achieved. .

[Brief description of the drawings]

1 to 4 show a first embodiment of the present invention, FIG. 1 is a hydraulic circuit diagram for a boom cylinder, FIG. 2 is a flow chart showing a solenoid valve opening / closing process, and FIG. Fig. 4 is a characteristic diagram showing signals and actuating signals, Fig. 4 is a characteristic vibration diagram of a working device, Fig. 5 is a hydraulic circuit diagram for a boom cylinder showing a second embodiment, and Figs. Showing the prior art,
FIG. 6 is an overall view of the hydraulic excavator, FIG. 7 is a hydraulic circuit diagram for the boom cylinder, and FIGS. 8A and 8B are characteristic lines showing the pressure in the bottom side oil chamber of the boom cylinder and the displacement of the boom, respectively. It is a figure. 1 ... Lower traveling body, 2 ... Upper swing body, 4 ... Operator's cab,
6 ... Working device, 7 ... Boom, 8 ... Arm, 9 ...
Bucket, 10 …… Boom cylinder, 10A …… Rod side oil chamber, 10B …… Bottom side oil chamber, 13 …… Hydraulic pump, 14 ……
Tank, 15 …… Main pipeline, 15A …… Rod side pipeline, 15B ……
Bottom side conduit, 16 ... Direction change valve, 21 ... Neutral position detection switch, 22 ... Solenoid valve, 24 ... Controller (control device), 31 ... Flow control valve, 32 ... Throttle.

Claims (5)

(57) [Claims] Claim: What is claimed is: 1. A boom, which is provided on a main body of a work machine so that the boom can be raised and lowered, a boom cylinder for supplying and discharging pressure oil to and from a rod-side oil chamber and a bottom-side oil chamber for raising and lowering the boom, and the boom. A pair of main pipes that connect the rod side oil chamber and the bottom side oil chamber of the cylinder to a hydraulic pressure source, and a pair of main pipes that are provided in the middle of the main pipes to supply and discharge to the rod side oil chamber and the bottom side oil chamber of the boom cylinder. In a hydraulic circuit for a boom cylinder of a working device, which comprises a direction switching valve for switching the direction of pressure oil to be operated, a neutral position detection switch for detecting that the direction switching valve is in a neutral position, and a bottom side oil chamber of the boom cylinder. And a directional valve, the solenoid valve is connected in the middle of the main conduit communicating with the bottom side oil chamber and is normally closed, and based on a signal from the neutral position detection switch, The directional valve is middle And a control device for opening the solenoid valve for a predetermined time and returning the bottom side pressure of the boom cylinder to a low pressure side after being returned to the position for a predetermined time. circuit. 2. The hydraulic circuit for a boom cylinder of a working apparatus according to claim 1, wherein the solenoid valve is provided in the middle of a pipeline connecting the pair of main pipelines. 3. The boom cylinder of a working apparatus according to claim 1, wherein the solenoid valve is provided in the middle of a pipeline connecting a main pipeline communicating with the bottom side oil chamber and a tank. Hydraulic circuit. 4. A hydraulic circuit for a boom cylinder of a working apparatus according to claim 2, wherein a flow control valve is provided in series with the solenoid valve in the middle of the pipeline. 5. A valve opening timing and a valve opening time of the solenoid valve are set to be within a quarter cycle of a natural vibration cycle of a working device and outside thereof, as claimed in claims (1) and (2). A hydraulic circuit for a boom cylinder of the working apparatus according to the item (3) or (4).