JPH073833A - Cylinder controller of construction machinery - Google Patents

Abstract

PURPOSE:To prevent the vibration of a boom in the case of operation stop by providing a selector to a branch line communicating with tank from a rod side hydraulic line, and making the rod side communicate with the tank except in the case high pressure occurs in the rod side. CONSTITUTION:A two position selector 54 is in a block state when hydraulic pressure power of a hydraulic line 16 is stronger than pushing pressure of a spring 58, and it is in a connection state with a tank 52, if it is weaker. After that, in the case a boom 18 is operated, the line 16 communicate with the tank 52 except in the case high pressure is supplied to the line 16. Then, in the case of normal operation, there is no high pressure in the line 16, so that even if a cylinder 11 vibrates, no high pressure occurs in the line 16. If it is usual, the boom 18 is strongly pushed down by rod side high pressure oil added to boom's dead weight, and vibration hard to damp is damped so quickly. According to the constitution, the expansion of the cylinder can be quickly converged after the stop of operation, the boom can be easily positioned, and efficiency can be promoted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a construction machine for driving a boom of a front working machine by selectively supplying hydraulic pressure to the bottom side or rod side of a hydraulic cylinder via a hydraulic pilot type control valve. The present invention relates to a cylinder control device.

[0002]

2. Description of the Related Art Conventionally, for example, a hydraulic excavator as shown in FIG. 4 has been widely used as a construction machine for driving a boom of a front working machine by a hydraulic cylinder.

In this hydraulic excavator, when the hydraulic pilot type control valve 10 having the pilot valve 8 is switched to the A side, pressure oil is sent to the bottom side line 14 of the hydraulic cylinder 11 by the pump 12 and the rod side line 16 is moved. Since the oil returns to the tank, the pressure on the bottom side increases and the piston 1
Boom 18 rises because 7 is pushed up.

Further, when the control valve 10 is switched to the B side, pressure oil is sent to the rod side line 16 by the pump 12, and the oil in the bottom side line 14 returns to the tank, so that the pressure on the rod side increases. Push down on the piston 17 and boom 18
Goes down.

In the state shown in FIG. 4, the control valve 10
Is in a neutral state and the movement of hydraulic pressure is blocked, so that the boom 18 is fixed in that position.

[0006]

However, in the construction machine such as the hydraulic excavator which drives the boom by the hydraulic cylinder as described above, when the operating speed of the cylinder is increased in order to improve the work efficiency, the operation is performed. After the stop, the cylinder slightly expands and contracts due to the inertia of the front working machine, the compressibility of hydraulic oil, and the like, and therefore, in the work of positioning the tip of the front working machine, the efficiency is hindered. Conventionally, since the operating speed of each hydraulic cylinder that drives the front working machine has not been so high, the inertial force when the operation is stopped is not so large, and the above-mentioned inconvenience is not conspicuous.

However, in recent years, construction machines such as hydraulic excavators tend to improve the operating speed of cylinders in order to improve work efficiency. Therefore, a phenomenon in which a cylinder that drives a boom having a large inertia repeats expansion and contraction after its operation is stopped has become remarkable.

The cause of this phenomenon will be described in detail below with reference to FIG.

FIG. 5 is a graph showing changes in the displacement of the boom tip, the bottom side pressure, and the rod side pressure with the lapse of time when the boom is stopped.

In the operation neutral state (FIG. 5), the rod side of the hydraulic cylinder (hereinafter simply referred to as the rod side) is in an unloaded state, and the bottom side of the hydraulic cylinder (hereinafter simply referred to as the bottom side) is at the boom side. Holding pressure is working.

Further, during boom lowering operation in a steady state (see FIG.
In (1), since the boom is dropped by its own weight, the rod side is in an almost unloaded state, and the bottom side is under the fall speed control pressure.

Further, when the operation is stopped (in FIG. 5), the boom tends to further descend due to its inertial force in the process of returning the operation amount to the neutral. At this time, because there is not enough force (pressure) to stop the movement of the boom on the bottom side,
The volume on the bottom side decreases and the boom further descends. Along with this, the pressure on the bottom side increases, as is clear from the following equation (1) showing the pressure change in the container due to the change in the volume of the hydraulic container.

Similarly, as is apparent from the equation (1), the volume increases and the pressure decreases on the rod side (however, immediately after the operation is stopped, the load is originally unloaded).

ΔP = −ΔV / (β × V) (1) ΔP: pressure change amount β: compression rate V: container volume ΔV: volume change amount

The compression ratio β of the hydraulic oil is theoretically a constant and small value irrespective of the pressure, but in reality, a small amount of air bubbles are mixed in the hydraulic oil, which is larger than the theoretical value. Becomes

When the pressure (force) on the bottom side becomes equal to the inertial force of the boom, the movement of the boom stops once. When the boom has stopped (Fig. 5), the pressure above the holding pressure is accumulated on the bottom side, so this pressure (force)
As a result, the boom tries to move up, but at this time, since there is no force (pressure) to stop the movement on the rod side, the boom starts to move up this time. Along with this, the volume on the bottom side increases and the pressure decreases (see equation (1)).

Even if this pressure drops to the holding pressure at the time of neutrality, the boom further rises due to its inertial force, and the bottom side pressure drops further. At this time, on the contrary, the volume on the rod side decreases, and the pressure increases (see formula (1)). When the pressure (force) becomes equal to the inertial force of the boom, the movement stops once.

In the state where the boom is once again stopped (in FIG. 5), the pressure on the bottom side is equal to or lower than the holding pressure, and therefore the boom is lowered. Along with this, the pressure on the bottom side rises to the holding pressure in the neutral state, but the boom further falls due to its inertial force.

Hereinafter, the above-mentioned states of FIG. 5 and FIG. 5 are repeated, and the cylinder converges with energy loss while repeatedly expanding and contracting.

Even after the boom raising operation is stopped, the cylinder repeatedly expands and contracts by the same phenomenon until it converges.

Therefore, in order to improve work efficiency, it has become necessary to converge the expansion and contraction of the cylinder as soon as possible.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a cylinder control device for a construction machine capable of quickly converging the expansion and contraction of the cylinder after the operation is stopped. .

[0023]

SUMMARY OF THE INVENTION The present invention is a construction for driving a boom of a front working machine by selectively supplying hydraulic pressure to the bottom side or rod side of a hydraulic cylinder via a hydraulic pilot type control valve. In a cylinder control device of a machine, a hydraulic line that communicates with a tank is branched from the hydraulic line on the rod side, and a switching valve that switches depending on the hydraulic pressure on the rod side is provided in the middle of the branched hydraulic line. Except when high pressure is generated on the side
The above object is achieved by allowing the rod side to communicate with the tank.

The present invention also provides a cylinder control for a construction machine for driving a boom of a front working machine by selectively supplying hydraulic pressure to the bottom side or rod side of a hydraulic cylinder via a hydraulic pilot type control valve. In the device,
A hydraulic line that communicates with the tank is branched from the hydraulic line on the rod side, and a switching valve that switches depending on the hydraulic pressure on the rod side and the pilot hydraulic pressure of the hydraulic pilot control valve is provided in the middle of the branched hydraulic line. The above-mentioned object is similarly achieved by allowing the rod side to communicate with the tank except when the high pressure is generated on the rod side or when the high pressure is being generated on the rod side.

[0025]

According to the present invention, the hydraulic line communicating with the tank is branched from the hydraulic line on the rod side, and a switching valve is provided in the middle of the branched hydraulic line. By this switching valve, a high pressure is actually generated on the rod side. The rod side can communicate with the tank except when (or when it is about to generate), and the high pressure due to the vibration of the boom is not generated on the rod side.

Thus, when positive pressure is required on the rod side, for example, when the boom is strongly pressed against the ground and the main body is lifted up (jacked up), the high pressure is applied to the rod side as in the conventional case. Can be generated, and during normal operation other than that, that is, when high pressure is not generated on the rod side, even if the boom vibrates, high pressure due to the vibration does not occur on the rod side, The boom is lowered only by its own weight (when vibrating), which effectively suppresses the repeated long vibration as in the conventional case.

[0027]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a hydraulic circuit diagram showing the structure of a front working machine (hydraulic shovel) according to a first embodiment of the present invention.

In FIG. 1, reference numeral 10 is a pilot valve 8
Hydraulic pilot type control valve including, 11 is a hydraulic cylinder,
Reference numeral 12 is a pump, 14 is a bottom side line, 16 is a rod side line, 17 is a piston, and 18 is a boom. There is no particular difference in the basic configuration from the configuration of the conventional hydraulic excavator already described.

On the other hand, reference numeral 50 is a hydraulic line branched from the hydraulic line 16 on the rod side and connected to the tank 52, and 54 is a switching valve provided in the middle of the hydraulic line 50. It is provided for this purpose.

This switching valve 54 is basically a two-position switching valve, and the rod side hydraulic line 16 (or the hydraulic line 5 branched from this) is inputted from the right side in the figure.
The hydraulic pressure of 0) and the balance of the spring 58 are used to switch the communication state of the hydraulic line 50 to the tank 52.

Specifically, the hydraulic line 16 (the hydraulic line 5
When the oil pressure of 0) is stronger than the pressing force of the spring 58, the block state (state B in the figure) is set, and when it is weak, the communication state (state A in the figure) is set.

Reference numeral 60 in the drawing is an orifice.
The function of the orifice 60 will be described later.

Next, the operation of the device of the first embodiment will be described by focusing on the added components. Due to the presence of the switching valve 54, the hydraulic line 16 on the rod side is as if it was during the jack-up operation. Basically, the hydraulic line 16 always communicates with the tank 52 except when high pressure is being supplied. Therefore, since high pressure is not generated on the rod side during normal operation, even if the cylinder 11 vibrates, the high pressure is not generated on the hydraulic line 16 on the rod side. For this reason, vibration that could not be easily damped due to the fact that the high hydraulic pressure on the rod side strongly pushes down the boom in addition to the boom's own weight can be damped more quickly.

According to the first embodiment, when a high pressure is positively generated on the rod side, for example, at the time of jacking up, until the hydraulic line on the rod side reaches a predetermined pressure. The switching valve 54 is located on the A side in the figure. However, in this case, the orifice 6
Due to the presence of 0, the drain speed via the switching valve 54 is suppressed, so that the hydraulic pressure can rise relatively easily.
As a result, the switching valve 54 is switched and reliably blocked when the hydraulic pressure reaches or exceeds the predetermined value.

When the hydraulic pressure in the hydraulic line 16 on the rod side is lowered from the high pressure state, the orifice 60 suddenly increases the drain amount from the time when the switching valve 54 is switched, and the hydraulic pressure sharply drops. It also has a function to prevent the accidental loss.

On the other hand, the second embodiment shown in FIG. 2 makes smoother the rise of the hydraulic pressure when supplying the hydraulic pressure to the rod side as in the jack-up operation, and does not provide any effect when the high pressure is supplied to the rod side. Even if the boom vibrates and the hydraulic pressure on the rod side suddenly drops due to such a cause, the switching valve 54 is prevented from switching to the communication side.

That is, in the second embodiment, the shuttle valve 70 is provided in the output oil passage of the pilot valve 8 and the switching valve 54 is also operated by the pilot oil pressure of the pilot valve 8.
Are switched.

As a result, the switching valve 54 is provided with the pilot valve 8 when the oil pressure in the rod side hydraulic line 16 is equal to or higher than a predetermined value, and even when the hydraulic pressure in the rod side hydraulic line is equal to or lower than the predetermined value. As long as the pilot oil pressure is output, it is switched to the block state (state B in the figure).
For this reason, when a command to supply high pressure to the rod side is issued, for example, during a jack-up operation, the hydraulic line 16 on the rod side is blocked from the beginning, so that it can be raised very smoothly. Will be able to.

In the second embodiment, since the pilot oil pressure of the pilot valve 8 is taken out by the shuttle valve 70, the switching valve 54 not only supplies the oil pressure to the rod side but also supplies the oil pressure to the cylinder side. In some cases, the control valve 10 is blocked.
Since the original rod-side hydraulic line 16 itself is communicated with the tank, no particular trouble occurs.

Further, in the second embodiment, an orifice 56 is newly added to the oil passage for supplying the oil pressure on the rod side to the switching valve 54 in order to switch the switching valve 54.

The reason for this is that when the control valve 10 is blocked while high pressure is being supplied to the rod side line, that is, when the pilot oil pressure of the pilot valve 8 is not being output, there is no sudden change in the load of the boom. Even if the cylinder vibrates for some reason and the hydraulic pressure of the rod side line suddenly drops below the switching oil pressure of the switching valve 54, the switching valve 54 will not switch due to this sudden drop. This is because This makes it possible to prevent switching of the switching valve 54 at an unintended time.

When supplying hydraulic pressure to the rod side,
As described above, from the beginning, the switching valve 54 has the block side (B
Side), the switching valve 5 increases the hydraulic pressure in the rod side hydraulic line 16 as early as possible as in the first embodiment.
It is not necessary to reflect it for switching of No. 4 and therefore, there is no particular problem even if the orifice 56 is inserted here.

FIG. 3 shows changes in the pressure on the bottom side and the pressure on the rod side when the tip of the front working machine is displaced using the apparatus according to the second embodiment.

As is clear from the comparison of FIGS. 3 and 5,
The expansion and contraction of the cylinder after the operation is stopped can be converged more quickly than before.

[0046]

As described above, according to the present invention,
Even when the work speed is fast, the expansion and contraction of the cylinder after operation is stopped can be quickly converged, and as a result, the boom tip of the front working machine can be easily positioned, and the work efficiency can be improved. The effect is obtained.

Further, since it is possible to suppress the occurrence of vibration of the entire front working machine during operation, it is possible to improve the durability of the movable parts of the working machine.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram showing a configuration of a second embodiment of the present invention.

FIG. 3 is a diagram showing changes over time in displacement of the front working machine tip, bottom side pressure, and rod side pressure, showing the effect of the second embodiment.

FIG. 4 is a hydraulic circuit diagram showing a configuration of a conventional construction machine.

[FIG. 5] A diagram showing displacement of the boom tip, bottom side pressure, and rod side pressure with time, showing the conventional problems.

[Explanation of symbols]

 8 ... Pilot valve 10 ... Hydraulic pilot control valve 11 ... Hydraulic cylinder 12 ... Pump 14 ... Bottom side line 15 ... Tank 16 ... Rod side line 18 ... Front working machine (boom) 50 ... Branching hydraulic line 52 ... Tank 54 ... Switching valve

Claims (2)

[Claims] 1. A cylinder controller for a construction machine for driving a boom of a front working machine by selectively supplying hydraulic pressure to a bottom side or a rod side of a hydraulic cylinder via a hydraulic pilot type control valve. A hydraulic line communicating with the tank is branched from the hydraulic line on the rod side, and a switching valve that switches depending on the hydraulic pressure on the rod side is provided in the middle of the branched hydraulic line to generate high pressure on the rod side. A cylinder control device for a construction machine, characterized in that the rod side can communicate with the tank except when. 2. A cylinder control device for a construction machine for driving a boom of a front working machine by selectively supplying hydraulic pressure to a bottom side or a rod side of a hydraulic cylinder via a hydraulic pilot type control valve, A hydraulic line communicating with the tank is branched from the hydraulic line on the rod side, and a switching valve that switches depending on the hydraulic pressure on the rod side and the pilot hydraulic pressure of the hydraulic pilot type control valve is provided in the branched hydraulic line. A cylinder control device for a construction machine, wherein the rod side can communicate with the tank except when high pressure is generated on the rod side or when high pressure is being generated on the rod side.