JP2001107399A - Hydraulic cylinder circuit for construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the structure of a buffer cylinder, miniaturize it, and surely provide a buffer effect. SOLUTION: A head side oil chamber 12a of boom cylinder 12 is connected to one pressure chamber 24 of a buffer cylinder 22, a pilot pump 17, or a hydraulic power source of a remote-control valve 18 is connected to the other pressure chamber 27, and a piston 23 is actuated based on the difference in the pressures introduced to the both pressure chambers 24, 27 so as to absorb the pressure fluctuation of the boom cylinder 12 and suppress the vibration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic actuator circuit for a construction machine in which a hydraulic cylinder supporting a large inertial load, such as a boom of a hydraulic shovel, is suppressed from vibrating when the cylinder is stopped or started.

[0002]

2. Description of the Related Art The prior art will be described with reference to a boom cylinder for supporting a boom of a hydraulic shovel.

In FIG. 6, reference numeral 1 denotes a hydraulic excavator body,
A work attachment 8 including a boom 2, an arm 3, a bucket 4, a boom cylinder 5 for operating the boom up and down, an arm cylinder 6 for operating the arm, and a bucket cylinder 7 for operating the bucket is mounted on the front portion of the shovel body 1. Is done.

A control valve 10 for controlling the operation direction and speed of the boom cylinder 5 is provided between the boom cylinder 5 and a hydraulic pump 9 and a tank T as a hydraulic pressure source thereof.

The control valve 10 is switched between a neutral position A, a cylinder extension position B, and a cylinder contraction position C, and pressure oil from the pump 9 is supplied to the head side oil chamber of the boom cylinder 5 at the cylinder extension position B. The boom cylinder 5 is supplied to the rod side oil chamber 5b at the cylinder contraction position c and the boom cylinder 5 is extended and contracted.

In FIG. 6, reference numeral 11 denotes an engine for driving the pump 9.

In this configuration, for example, when the operation of the boom 2 in the falling direction is stopped, the boom cylinder 5 vibrates due to the inertial load of the boom 2.

That is, when the boom stops, the pressure in the head side oil chamber 5a of the boom cylinder 5 sharply increases due to the inertial load, and conversely, the pressure in the rod side oil chamber 5b sharply decreases. Then, the reaction of the head-side pressure increase acts on the piston 5c, so that the rod-side pressure rapidly increases and the head-side pressure rapidly decreases. This repetition causes a pressure pulsation, which causes machine vibration.

This vibration also occurs when the operation of the boom 2 in the upright direction is stopped and when the boom is started up, and this vibration causes problems such as an increase in operator fatigue and a reduction in work efficiency.

Therefore, conventionally, in order to suppress such vibration, Japanese Utility Model Registration No. 2577406, Japanese Unexamined Patent Publication No.
As disclosed in Japanese Patent No. 30601, a technique has been proposed in which a buffer cylinder is provided between pipes on both sides of a cylinder, and pressure fluctuation of an actuator is mitigated by movement of a piston of the buffer cylinder.

[0011]

In this technique,
For example, in the case of the boom cylinder 5 in FIG. 6, since there is a difference in pressure receiving area between the head side and the rod side, the pressure acting on the oil chambers on both sides of the buffer cylinder is unbalanced due to this area difference, and the piston moves to the low pressure side. Since the cylinder is deviated and does not function, a difference in pressure receiving area is provided on the buffer cylinder side as a means for absorbing this.

More specifically, utility model registration No. 257740
In JP-A-6-63, the cylinder diameter of the buffer cylinder is increased on the side corresponding to the rod side of the boom cylinder.
In No. 30601, the piston of the cylinder is provided with a rod according to the boom cylinder side.

As a result, the structure of the shock-absorbing cylinder becomes complicated or large, which is disadvantageous in cost and circuit space.

SUMMARY OF THE INVENTION The present invention provides a hydraulic actuator circuit of a construction machine which can have a simple and small structure of a shock-absorbing cylinder and can obtain a reliable shock-absorbing effect.

[0015]

According to a first aspect of the present invention, there is provided a hydraulic pump, a hydraulic cylinder driven by hydraulic oil from the hydraulic pump, and supply and discharge of hydraulic oil from the hydraulic pump to the hydraulic cylinder. In a hydraulic cylinder circuit of a construction machine having a control valve for controlling, a hydraulic pressure source for buffering is provided separately from the hydraulic pump, and between the hydraulic pressure source for buffering and at least one oil chamber of the hydraulic cylinder, A buffer cylinder provided with a piston that operates based on a difference between the pressure of the oil chamber and the pressure of the buffer hydraulic pressure source is provided.

According to a second aspect of the present invention, in the configuration of the first aspect, a boom cylinder for raising and lowering the boom in the construction machine having the boom is used as the hydraulic cylinder, and at least one of the oil chamber and the buffer for the boom is used. A buffer cylinder is provided between the hydraulic cylinder and a hydraulic pressure source.

According to a third aspect of the present invention, in the configuration of the first or second aspect, a throttle for restricting oil flowing into or out of the buffer cylinder is provided.

According to a fourth aspect of the present invention, in the configuration of the third aspect, the throttle is provided on both sides of the buffer cylinder.

According to a fifth aspect of the present invention, in the configuration according to any one of the first to fourth aspects, the shock-absorbing cylinder is provided with a spring for applying a spring force toward the neutral position to the piston.

According to a sixth aspect of the present invention, in the configuration of any one of the first to fifth aspects, between the buffer hydraulic pressure source and the tank,
A relief valve for setting a pressure of a pipe connecting the hydraulic pressure source for the buffer and the buffer cylinder is provided.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects, a hydraulic pilot type switching valve is used as the control valve, and a hydraulic source of a remote control valve for supplying pilot pressure to the control valve is provided. This is used as a buffer hydraulic pressure source for the buffer cylinder.

According to the above construction, the hydraulic cylinder (boom cylinder in claim 2) is provided in one oil chamber of the buffer cylinder.
And the other oil chamber is supplied with the pressure of a buffer hydraulic pressure source different from that of the hydraulic cylinder drive pump, and based on these differences, the piston operates to suppress the pressure fluctuation of the hydraulic cylinder and reduce vibration. Is prevented.

Accordingly, by appropriately setting the pressure of the buffer hydraulic pressure source so as not to cause the bias of the piston, the desired vibration absorbing function can be achieved especially in a hydraulic cylinder having a large inertial load as in the boom cylinder of the second aspect. Can be reliably obtained.

Further, unlike the prior art in which the pressures in the oil chambers on both the head side and the rod side of the hydraulic cylinder are introduced into the oil chambers on both sides of the buffer cylinder, there is no need to make the pressure receiving areas on both sides of the buffer cylinder different. Therefore, there is no need to make the buffer cylinder a double structure or a structure with a rod, so that the structure of the buffer cylinder is simple and small.

According to the third and fourth aspects of the present invention, the vibration energy of the oil is converted to heat energy by restricting the oil flowing into or out of the buffer cylinder in addition to the basic buffering action by the movement of the piston. To be
The vibration suppressing effect is enhanced. In particular, according to the configuration of claim 4 in which the throttle is provided on both sides of the buffer cylinder, this effect is remarkable.

According to the fifth aspect of the present invention, since the piston is biased to the neutral position by the spring, even if the difference between the pressures introduced into the oil chambers on both sides of the buffer cylinder is large,
By providing this spring on the side where the pressure is low, the differential pressure can be reduced.

Therefore, the desired vibration suppression function can be ensured even under conditions where the pressure of the buffer hydraulic pressure source cannot be increased, or even when the range of pressure fluctuation of the hydraulic cylinder is wide.

According to the configuration of claim 6, since the upper limit of the pressure of the pipeline connecting the buffer cylinder and the buffer hydraulic pressure source is regulated by the relief valve, particularly, the buffer hydraulic pressure source is connected to another hydraulic device (claim 7). In the case where the configuration is shared as the hydraulic pressure source of the remote control valve, there is no possibility that the operation of other hydraulic equipment is adversely affected.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

In the following embodiment, a boom cylinder circuit of a hydraulic shovel is taken as an example in accordance with the description of the prior art.

Basic Embodiment (See FIGS. 1 to 3) In FIG. 1, reference numeral 12 denotes a boom cylinder, and both head-side and rod-side oil chambers 12a and 12b of the boom cylinder 12 are provided.
Are connected to the head-side and rod-side conduits 13 and 14, respectively.
5 is connected to the main pump 16 or the tank T.

The control valve 15 has neutral, extended and contracted positions a and b, similarly to the control valve 10 of FIG.
The pressure oil from the main pump 16 is supplied to the boom cylinder 1 at the extended position b of the control valve 15.
The boom cylinder 12 is extended and contracted by being supplied to the rod-side oil chamber 12b at the contraction position c, respectively, to the second head-side oil chamber 12a.

The control valve 15 is configured as a hydraulic pilot type switching valve, and is switched and operated by operating a remote control valve 18 using a pilot pump 17 as a hydraulic pressure source.

Reference numeral 19 denotes both the main and pilot pumps 16,
The engine which drives 17, 20 is the pilot pump 17
Discharge line (hereinafter referred to as pilot pump line) 2
This is a relief valve provided between the tank 1 and the tank T.

In this circuit, the boom cylinder 12
A buffer cylinder 22 that absorbs pressure fluctuations generated in the cylinder and suppresses vibration is provided between the cylinder head side pipe line 13 and the pilot pump line 21.

The buffer cylinder 22 has a piston 23 inside, and a first pressure chamber 24 provided on one side with the piston 23 interposed therebetween is connected to a cylinder head side via a first throttle 25 and a first conduit 26. A second pressure chamber 27 provided on the opposite side of the pipe 13 is connected to the pilot pump line 21 via a second throttle 28 and a second pipe 29, respectively.

That is, the pressure on the head side of the boom cylinder 12 (for example, 40 to 50 kgf /
cm ² . Hereinafter, the pressure of the pilot pump 17 (for example, 3
5~50Kgf / cm ^2. Hereinafter, referred to as pilot pump pressure).

The second pressure chamber 27 has a piston 23
Is provided to the first pressure chamber 24 side. The sum of the force of the spring 30 and the pilot pump pressure (hereinafter referred to as the opposing force) opposes the cylinder head side pressure. It moves to absorb pressure fluctuations of the boom cylinder 12 and suppress vibration.

The operation of this point will be described in detail below.

When the control valve 15 is in the neutral position A and the boom cylinder 12 is not operated, a pressure (holding pressure) for supporting the attachment weight is generated in the head side oil chamber 12a of the boom cylinder 12, The cylinder head side pressure and the above-described opposing force are balanced, and the piston 23 is held at a substantially neutral position in the center of the cylinder.

In this state, when the control valve 15 is operated to the cylinder reduction position C, the boom cylinder 12 is reduced and the boom falls.

At this time, since the head-side oil chamber 12a of the boom cylinder 12 communicates with the tank T, the cylinder head-side pressure becomes lower than that during the stop of the operation, and the piston 23 balances the cylinder head-side pressure with the opposing force. Held in position.

Next, when the control valve 15 is returned to the neutral position A, the reduction operation of the boom cylinder 12 is stopped, and the boom falling operation is stopped. At this time, the inertial load of the attachment including the boom acts on the boom cylinder 12, so that the cylinder head side pressure sharply increases, and conversely, the cylinder rod side pressure tends to sharply decrease.

Here, the pressure on the cylinder head side is introduced into the first pressure chamber 24 of the buffer cylinder 22, and both pressure chambers 24,
Since the balance of 27 is lost, the piston 23 moves to the second pressure chamber 27 side, and stops at a position where the balance is achieved.
Due to the movement of the piston 23, the increase in the cylinder head side pressure is absorbed by the buffer cylinder 22.

Also, the first cylinder 26 is connected to the buffer cylinder 22
The oil flowing into the cylinder and the oil flowing out of the buffer cylinder 22 pass through the throttles 25 and 28, respectively, so that the vibration energy of the oil is consumed and reduced as heat energy.

By the movement of the piston and the action of the throttle, pressure fluctuations in the boom cylinder 12 are absorbed and vibration is suppressed.

FIG. 3 shows the state of pressure fluctuation when the buffer cylinder 22 is provided (broken line) and when it is not provided (solid line). By providing the cylinder 22 as shown in the figure, pressure fluctuations on both the boom cylinder rod side and the head side are attenuated and converged early.

Further, as shown in the lower part of FIG.
In 9, oil flows in and out due to the movement of the piston 23 of the buffer cylinder 22, but the pressure in the pipe line 29 is kept constant by the relief valve 20, so that pressure fluctuation hardly occurs. Therefore, the primary pressure of the remote control valve 18 does not fluctuate, and there is no possibility that the switching operation of the control valve 15 is adversely affected.

4. Other Embodiments (1) In the basic embodiment, the cylinder head side pressure is introduced into the buffer cylinder 22 to reduce it.
The first pressure chamber 24 of the buffer cylinder 22 is
It may be connected to the cylinder rod side pipe 14 through the throttle 25 and the first pipe 26.

According to this configuration, the fluctuation of the cylinder rod side pressure is directly absorbed by the buffer cylinder 22, and as a result, the same vibration suppression effect as in the first embodiment can be obtained.

(2) It is desirable to provide a spring 30 in the buffer cylinder 22 to fill the difference between the cylinder side pressure and the pilot pressure as in the above embodiment, but this spring 30 is omitted as shown in FIG. Alternatively, a configuration in which the pressure fluctuation is absorbed only by the moving action of the piston 23 may be adopted.

Even with this configuration, the intended purpose can be achieved by minimizing the difference between the cylinder side pressure and the pilot pressure.

(3) The buffer cylinder 22 is preferably provided with throttles 25 and 28 in both the first and second conduits 26 and 29 as in the basic embodiment. Is also good.

Alternatively, as shown in FIG.
5 and 28 may be omitted. In this case, apertures 25 and 28
As an alternative, it is possible to obtain a pressure fluctuation absorbing action due to pressure loss in the relief valve 20.

(4) The buffer cylinder 22 may be provided on only one of the cylinder head side and the rod side as in the above embodiment, but may be provided on both sides as necessary.

(5) In the above embodiment, the remote control valve 18
Although the pilot pump 17 which is a hydraulic pressure source is used as the hydraulic pressure source for buffering, another pump (or a pump dedicated to buffering) may be used as the hydraulic pressure source for buffering.

(6) The present invention can be widely applied not only to the boom cylinder of the hydraulic excavator described in the above embodiment, but also to a hydraulic cylinder on which a particularly large inertial load acts on a construction machine.

[0058]

As described above, according to the present invention, the pressure of the hydraulic cylinder (boom cylinder in claim 2) is applied to one oil chamber of the buffer cylinder, and the other oil chamber is provided with a pressure different from the hydraulic cylinder driving pump. Since the pressure of the hydraulic pressure source for buffering is introduced and the piston is operated based on the difference between them to absorb the pressure fluctuation of the hydraulic cylinder and suppress the vibration, the hydraulic pressure source for buffering is prevented so that the piston is not biased. By appropriately setting the pressure, the desired vibration absorbing function can be reliably obtained, especially in a hydraulic cylinder having a large inertial load as in the boom cylinder of the second aspect.

Further, unlike the prior art in which the pressures of the oil chambers on both the head side and the rod side of the hydraulic cylinder are introduced into the oil chambers on both sides of the buffer cylinder, there is no need to provide a difference in the pressure receiving area on both sides of the buffer cylinder. Therefore, there is no need to make the buffer cylinder a double structure or a structure with a rod, so that the structure of the buffer cylinder is simple and small.
This is advantageous in cost and circuit space.

According to the third and fourth aspects of the present invention, in addition to the basic buffering action by the movement of the piston, the oil flowing into or out of the buffer cylinder is throttled to convert the vibration energy of the oil into heat energy. To be
The vibration suppressing effect is enhanced. In particular, according to the invention of claim 4 in which the throttle is provided on both sides of the buffer cylinder, this effect is remarkable.

Further, according to the fifth aspect of the present invention, since the piston is biased to the neutral position by the spring, even if the difference between the pressures introduced into the oil chambers on both sides of the buffer cylinder is large,
By providing this spring on the side where the pressure is low, the differential pressure can be reduced.

Accordingly, the desired vibration suppression function can be ensured even under conditions where the pressure of the buffer hydraulic pressure source cannot be increased, or even when the range of pressure fluctuation of the hydraulic cylinder is wide.

According to the sixth aspect of the present invention, since the upper limit of the pressure in the pipeline connecting the shock-absorbing cylinder and the shock-absorbing hydraulic power source is regulated by the relief valve, the shock-absorbing hydraulic power source is connected to another hydraulic device (claim 7). In the case where the configuration is shared as the hydraulic pressure source of the remote control valve, there is no possibility that the operation of other hydraulic equipment is adversely affected.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a boom cylinder circuit according to a basic embodiment of the present invention.

FIG. 2 is a sectional view of a buffer cylinder used in the circuit.

FIG. 3 is a diagram for explaining a pressure fluctuation absorbing state by a buffer cylinder.

FIG. 4 is a circuit diagram of a boom cylinder circuit according to another embodiment of the present invention.

FIG. 5 is a sectional view of a buffer cylinder used in a boom cylinder circuit according to another embodiment of the present invention.

FIG. 6 is a circuit diagram of a conventional boom cylinder circuit.

[Explanation of symbols]

12 Boom cylinder as a hydraulic cylinder to be applied 16 Hydraulic pump as a hydraulic source of boom cylinder 15 Control valve 22 Buffer cylinder 23 Piston of buffer cylinder 24 First pressure chamber of buffer cylinder 27 Second pressure chamber of buffer cylinder 25, 28 Throttle 30 Spring 17 Pilot Pump as Buffer Hydraulic Source 18 Remote Control Valve 20 Relief Valve

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hirohisa Kimura 1682-2, Honimacho, Ogaki-shi, Gifu In-house Shinko Machinery Co., Ltd. (72) Inventor Takao Nanjo 1-5-5 Takatsukadai, Nishi-ku, Kobe Stock Company Kobe Steel, Kobe Research Institute F-term (reference) 2D003 AA01 AB03 BA08 BB03 CA06 DA03 3H089 AA66 BB05 CC01 CC20 DA02 DA06 DB03 DB13 DB33 DB47 DB49 EE15 EE22 GG02 JJ02

Claims (7)

[Claims] 1. A construction machine comprising a hydraulic pump, a hydraulic cylinder driven by hydraulic oil from the hydraulic pump, and a control valve for controlling the supply and discharge of hydraulic oil from the hydraulic pump to the hydraulic cylinder. In the hydraulic cylinder circuit, a buffer hydraulic pressure source is provided separately from the hydraulic pump, and between the buffer hydraulic pressure source and at least one oil chamber of the hydraulic cylinder, the pressure of the oil chamber and the hydraulic pressure source for the buffer are provided. A hydraulic cylinder circuit for a construction machine, comprising: a shock-absorbing cylinder provided with a piston that operates based on a pressure difference between the cylinders. 2. A boom cylinder for raising and lowering a boom in a construction machine having a boom is used as a hydraulic cylinder, and a buffer cylinder is provided between at least one oil chamber of the boom cylinder and a buffer hydraulic pressure source. The hydraulic cylinder circuit for a construction machine according to claim 1, wherein: 3. A throttle for restricting oil flowing into or out of the buffer cylinder is provided.
Or a hydraulic cylinder circuit of a construction machine according to 2. 4. The hydraulic cylinder circuit for a construction machine according to claim 3, wherein the throttle is provided on both sides of the buffer cylinder. 5. The hydraulic cylinder circuit for a construction machine according to claim 1, wherein the buffer cylinder is provided with a spring that applies a spring force to the piston toward a neutral position. 6. The relief valve according to claim 1, wherein a relief valve for setting a pressure of a pipe connecting the hydraulic pressure source for the buffer and the buffer cylinder is provided between the hydraulic pressure source for the buffer and the tank. A hydraulic cylinder circuit for a construction machine according to any one of the above. 7. A control valve, wherein a hydraulic pilot type switching valve is used, and a hydraulic source of a remote control valve for supplying pilot pressure to the control valve is used as a hydraulic pressure source for a buffer cylinder. Item 7. A hydraulic cylinder circuit for a construction machine according to any one of Items 1 to 6.