JPS6233948A - Oil-pressure driver - Google Patents

Abstract

PURPOSE:To prevent the change in speed of an arm cylinder by a method in which during the contracting period of arm cylinder, the discharge amount of an oil-pressure pump is controlled according to the signals of an operating lever, and the detected values of the rod-side pressures of the cylinder and the flow rate of the operating lever are controlled. CONSTITUTION:An electromagnetic proportional valve 20 for controlling flow rates is provided between a main pipeline B and a tank 8 constituting the head- side circuit of an arm cylinder 14. The discharge amount of an oil-pressure pump 1 is controlled by an electric oil-pressure pump discharge amount controller 35 according to signals of a controller 30 on the basis of signals of an operating lever 25. Also, according to the signals of the controller 30, the opening degree of the valve 20 is regulated. The pressure of the rod side of the cylinder 14, or the pressure of the main pipeline A is detected by a pressure sensor 40 and sent out to the controller 30. During the contracting period of the cylinder 14, according to the difference between the oil amount on the rod side and the oil amount from the head side and also the output of the sensor 40, the opening degree of the valve 20 is regulated by signals of the controller 30.

Description

Detailed Description of the Invention (Field of Application of the Invention) The present invention relates to a hydraulic drive device in which a single rod cylinder such as an arm cylinder provided in a hydraulic excavator is driven and controlled by pressure oil discharged from a variable displacement hydraulic pump. Regarding.

[Background of the invention]

As this type of hydraulic drive device, there has been a
There is one described in No. 14. FIG. 3 is a circuit diagram showing this conventional hydraulic drive device, in which 1 is a variable displacement hydraulic pump whose discharge amount is controlled in accordance with a signal output from an operation lever (not shown); A single rod cylinder whose drive is controlled by discharged pressure oil, such as an arm cylinder installed in a hydraulic excavator, has a ratio of pressure receiving area on the head side to pressure receiving area on the rod side of approximately 2:1. . In addition, A and B are main pipes that connect the variable displacement hydraulic pump 1 and the arm cylinder 14, 8 is a tank, and 4 is a flushing that detects the pressure in either of the main pipes A or B and communicates the low pressure side with the tank 8. Valve 5 is a relief valve that regulates the minimum pressure of main pipes A and B; 6.
7 is a check valve provided to supply oil to main pipes A and B.

FIG. 4 is a schematic side view of a hydraulic excavator equipped with the hydraulic drive device shown in FIG. 3. In this figure, 14 is the aforementioned arm cylinder, 13 is a boom cylinder, 15 is a packet cylinder, 10 is a rotatable boom driven by the boom cylinder 13, and 11 is connected to the boom 10 and is rotatable by the arm cylinder 14. possible arm,
A packet 12 is connected to the arm 11 and is rotatable by a packet cylinder 15, and these constitute a working machine. Note that G is the center of gravity including the arm 11, packet 12, etc., and θ is the angle formed by the ground plane and a line passing through the connection between the boom 10 and the arm 1 and the center of gravity G.

In the hydraulic drive device configured as described above, the head side of the arm cylinder 14 becomes high pressure and the rod side becomes low pressure, or conversely, the rod side becomes high pressure and the head side becomes low pressure. Therefore, as shown in FIG. 4, a problem occurs when the arm cylinder 14 is retracted from the excavation position in which the arm 11 is retracted to the maximum and transferred to the discharge position.

That is, initially, the dead weight of the arm 11 is the weight of the arm cylinder 1.
4, the main pipe line B side in FIG. In order to extend the arm 11 from this state, the variable displacement hydraulic pump 1 pumps oil from the head side circuit of the arm cylinder 14 to the main pipe A.
When the oil is sent out to the side, the arm cylinder 14 operates at a speed corresponding to the amount of oil sent out, aided by energy due to the weight of the arm 11. At this time, the main pipe A is in communication with the tank 8 as described above. Then, as the arm 11 gradually assumes a nearly vertical posture, the energy due to the weight of the arm 11 decreases, and the operating speed of the arm cylinder 14 decreases.

When the arm 11 passes the vertical position, the arm cylinder 14
The force applied to is reversed, and the pressure on the rod side, that is, the main pipe A becomes high, and the pressure on the head side, that is, the main pipe B becomes low,
The flushing valve 4 is switched to communicate the main pipe B with the tank 8. At this time, the arm cylinder 14 is rapidly accelerated to a speed determined by the discharge amount of the variable displacement hydraulic pump 1 and the pressure receiving area on the rod side.

FIG. 5 (al is a characteristic diagram showing the operating speed corresponding to the angle θ shown in FIG. 4 described above of the arm cylinder 14 described above,
Figure 5 (bl, (cl, and d) each have θ of 5o.
°.

It is an explanatory view illustrating the form of the arm 11 part at 90 degrees and 130 degrees. In addition, SL in FIG. 5 (al) is the head side pressure receiving area of the arm cylinder 14 and the hydraulic pump 1.
The form in the explanatory diagram of FIG. 5 (bl) corresponds to this, S2 shows the free fall range due to the arm 11's own weight, Corresponding to this, S3 indicates the speed depending on the rod side pressure receiving area of the arm cylinder 14 and the discharge amount of the hydraulic pump 1, and the form in the explanatory diagram of Fig. 5+d+ corresponds to this. The switching point of the flushing valve 4 is shown.

In this way, in the conventional hydraulic drive device, when transitioning from the excavation operation to the discharge operation as described above, the main pipe A
, B, and the force due to the weight of the arm 11, the operating speed of the arm cylinder 14 is rapidly accelerated at the switching point of the flushing valve 4, resulting in a shock. There is a problem that this causes problems such as poor operability. Furthermore, since the operating speed of the arm cylinder 14 is affected by the weight of the arm 11,
This free fall of the arm 11 causes a decrease in speed, resulting in a problem of poor operability.

[Object of the Invention] The present invention has been made in view of the above-mentioned actual situation in the prior art, and its purpose is to prevent speed changes of the single-rod cylinder regardless of changes in the force applied to the single-rod cylinder. The purpose of the present invention is to provide a hydraulic drive device.

[Summary of the invention]

To achieve this object, the present invention provides a variable displacement hydraulic pump whose discharge amount is controlled in accordance with a signal output from an operating lever, and a hydraulic pump whose drive is controlled by the pressure oil discharged from the variable displacement hydraulic pump. For those equipped with a rod cylinder, a valve is installed between the head side circuit of the single rod cylinder and the tank to control the flow rate, and a pressure detection system that detects the pressure on the rod side of the single rod cylinder and outputs a signal. Means is provided to control the discharge amount of the variable displacement hydraulic pump in response to the signal when the single rod cylinder is contracted, and to control the flow rate of the valve in response to the signal and the signal output from the pressure detection means. This is the configuration that controls it.

[Embodiments of the invention]

Hereinafter, the hydraulic drive device of the present invention will be explained based on the drawings.

1 and 2 are explanatory diagrams showing one embodiment of the present invention, FIG. 1 is a circuit diagram showing the main configuration, and FIG. 2 is an explanatory diagram showing a control section provided in the circuit shown in FIG. 1. It is. In these figures, the same parts as those shown in FIG. 3 described above are designated by the same reference numerals.

The variable displacement hydraulic pump 1 is provided with an electric/hydraulic pump discharge amount control device 35, and this control device 35 controls the discharge amount of the hydraulic pump 1 in accordance with an electric signal from a control section 30, which will be described later. Further, a valve for controlling the flow rate, for example, an electromagnetic proportional valve 20 is provided between the main pipe B constituting the head side circuit of the arm cylinder 14 and the tank 8. A relief valve 5 is arranged to regulate the minimum pressure of the main pipes A and H. Note that the valve opening degree of the electromagnetic proportional valve 20 is adjusted in accordance with a signal output from the control section 30. Reference numeral 40 denotes pressure detection means, ie, a pressure detector, which detects the pressure on the rod side of the arm cylinder 14, that is, the pressure in the main pipe A, and outputs a signal to the control section 30.

The control section 30 described above includes function generators 30a, 30b and a comparator 30f connected to the operating lever 25, and a function generator 3 connected to the pressure detector 40, as shown in FIG.
0e, an adder 30h connected to the function generator 30e and the function generator 30a via the switch 30g, and an amplifier 30C connected to the adder 30h and connected to the electromagnetic proportional valve 20. , function generator 30b
and an electric/hydraulic pump discharge amount control device 35
The amplifier 30d is connected to the amplifier 30d.

The function generator 30a described above has an operating lever 25.
A signal Qv1 is output to the adder 30h in relation to the signal X output from the adder 30h. Note that when the arm cylinder 14 is extended, that is, during excavation operation, the amount of oil in the circuit is insufficient, so the oil in the tank 8 is supplied to the main pipe A or B from the check valve 6 or check valve 7 shown in FIG. In this case, QvL=O is set. Also,
When the arm cylinder 14 contracts, that is, when the excavation operation shifts to the discharge operation, the amount of oil in the circuit becomes surplus, so a value corresponding to the signal XL of the operating lever 25 is output as QvL.

Further, the function generator 30b controls the discharge amount of the variable displacement hydraulic pump 1 according to the amount of operation of the operation lever 25.
A signal QF is output to the amplifier 30d in relation to the signal XL of the operating lever 25. That is, the speed and driving direction of the arm cylinder 14 are determined by this signal Q.

The relationship between the signal QP and the signal Qv described above is as follows: Let Qp be the amount of oil flowing to the rod side of the arm cylinder 14 in response to the signal Q when the arm cylinder 14 is contracted, and this oil amount q
Let ql be the amount of oil flowing out from the head side of the arm cylinder 14 due to l, then the amount of oil qvWqh Qp
The setting is such that a signal Q%IL is applied to drive the electromagnetic proportional valve 20 so that it flows into the tank 8 via the electromagnetic proportional valve 20.

Furthermore, the function generator 30e outputs a signal Qvp in response to the signal output from the pressure detector 40.

Here, the relationship between the signal P indicating the pressure in the main pipe A and the signal Qvp is that when P is smaller than the set pressure PO of the relief valve 5, a negative signal Qv proportional to the difference between these Po and P is established.
p, and when P is 20 or more, a positive signal Qv2 proportional to the difference between these Po and P is output, that is, Qv, = α (p - po ) (α: constant)
The relationship is set as follows.

Further, the comparator 30f determines whether the operating lever signal XL is a signal when the arm cylinder 14 is contracted, and when it is determined that this is a signal when the arm cylinder 14 is contracted, and when the operating lever 25 has exceeded the dead zone. Sometimes, switch 30g is turned on.
An N signal is output, which closes the switch 30g and connects the function generator 30e and adder 30h. At this time, the adder 30h outputs the signal Qvp output from the function generator 30e and the signal Q output from the function generator 30a.
v [ and output to the amplifier 30c.

In this embodiment, when the arm cylinder 14 is contracted to transition from the excavation operation to the retraction operation, the signal QP having the above-mentioned relationship corresponding to the output signal X, , of the operating lever 25 is output to the function generator 30b. Further, according to the output from the amplifier 30d, the discharge amount control device fft35 is operated to control the discharge amount of the hydraulic pump 1, and at the same time, the output signal XL of the operating lever 25 and the pressure detector 4 are Signal QvL and signal Qvp, which have the above-mentioned relationship corresponding to signal P output from The opening degree of the electromagnetic proportional valve 20, that is, the amount of excess oil flowing through the electromagnetic proportional valve 2°, is adjusted, and thereby the operating speed of the arm cylinder 14 is controlled to a predetermined operating speed corresponding to the operating amount of the operating lever 25. .

In the embodiment configured in this way, a flushing valve is not provided, and the arm cylinder 1 is
function generator 30 without having to consider the force applied to 4.
Since the operating speed of the arm cylinder 14 can be set to a predetermined value by the functional relationship set in a and 30b, the operating speed of the arm cylinder 14 can be adjusted as the shape of the arm changes.
Regardless of changes in the force applied to the arm cylinder 14
Therefore, good operability can be obtained without causing a speed change due to rapid acceleration of the speed or a drop in speed due to free fall of the arm.

Further, when the arm cylinder 14 is contracted and a fine operation is performed by the operating lever 25, the main line B is closed and the pressure of the main line B increases, and accordingly, the main line A on the rod side of the arm cylinder 14 is closed. When the pressure increases, a signal Qv corresponding to the signal Qv2 outputted from the function generator 30e corresponding to the signal P detected by the pressure detector 4° is added to the signal QvL outputted from the function generator 30a. As a result, the opening degree of the electromagnetic proportional valve 20 is adjusted, so that as the pressure in the main pipe B increases, the main pipe B is immediately opened, the increase in pressure in the main pipe B is restricted, and the energy is reduced. In addition to reducing wastage, arm cylinder 1
4 without causing speed changes (good fine controllability can be obtained).

In the above embodiment, the arm cylinder 14 was used as an example of a single rod cylinder, but the present invention is not limited to this, and can be applied to any cylinder having a single rod cylinder to which a force that changes in magnitude and direction is applied. It is possible.

〔Effect of the invention〕

Since the hydraulic drive device of the present invention is configured as described above, it is possible to prevent the speed of the single-rod cylinder from changing regardless of changes in the force applied to the single-rod cylinder.
The operability is improved compared to the conventional model, and it is possible to prevent the main pipeline from being blocked when performing small operations when the single-rod cylinder is retracted, suppressing energy waste, and preventing speed changes of the single-rod cylinder. This has the effect of providing fine controllability.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams showing one embodiment of the hydraulic drive device of the present invention, FIG. 1 is a circuit diagram showing the main configuration, and FIG.
The figure is an explanatory diagram showing a control unit provided in the circuit shown in Fig. 1, Fig. 3 is a circuit diagram showing a conventional hydraulic drive device, and Fig. 4 is a diagram of a hydraulic excavator equipped with the hydraulic drive device shown in Fig. 3. Schematic side view, FIG. 5 (al is a characteristic diagram showing the operating speed corresponding to the angle θ shown in FIG. 4 of the arm cylinder shown in FIG. 3, FIG. 5(b), (C1, (d+ is the fourth It is an explanatory view illustrating the form of the arm part when the angle θ shown in the figure is 50°, 90°, and 130°, respectively. 1... Variable displacement hydraulic pump, 8... Tank, 1
4...Arm cylinder (single rod cylinder), 20
... Solenoid proportional valve, 25 ... Operation lever, 30.
...Control unit, 30a, 30b, 30e...=Function generator, 30c, 30d...Amplifier, 30f...
Comparator, 30g...switch, 30h...adder, 35...electric/hydraulic pump discharge amount control device, 4
o...Pressure detector (pressure detection means). Figure 3

Claims (1)

[Claims] 1. A hydraulic drive device that includes a variable displacement hydraulic pump whose discharge amount is controlled according to a signal output from an operating lever, and a single rod cylinder whose drive is controlled by the pressure oil discharged from the variable displacement hydraulic pump. A valve for controlling the flow rate is provided between the head side circuit of the single rod cylinder and the tank, and a pressure detection means for detecting the pressure on the rod side of the single rod cylinder and outputting a signal is provided. The discharge amount of the variable displacement hydraulic pump is controlled in accordance with the signal when the single rod cylinder contracts, and the flow rate of the valve is controlled in accordance with the signal and a signal output from the pressure detection means. Hydraulic drive device.