JPH1061605A - Hydraulic driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent regression of metering against lowering of rotating speed of a prime mover by providing a bleed-off valve control means, thereby suitably throttling a bleed-off valve when the prime mover is rotated at low speed. SOLUTION: A relational relationship is formed in such a manner that when reference rotating speed is Ne=No, a pump minimum discharge flow is taken to be a point A, and if the rotating speed is reduced to the half (Ne-No/2), it is taken to be a point C. According to the negative flow control by seventh and eighth operation functions 40, 41, the negative flow control characteristic of a hydraulic pump can be set in such a manner that a decrease in pump minimum discharge flow Qpmin due to lowering of rotating speed of a prime mover is taken as lowering rate from the reference rotating speed, and the coefficient is Kn. Accordingly, even if the pump minimum discharge flow is lowered with a lowering of the rotating speed of the prime mover in cooperation with the drive control for the bleed-off valve, the pump discharge pressure limit equal to that in the case of reference rotating speed No can be obtained so as to prevent regression of metering and keep the same operability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive device provided in a hydraulic machine such as a hydraulic excavator or a hydraulic crane.

[0002]

2. Description of the Related Art As a hydraulic drive device provided in a hydraulic machine such as a hydraulic excavator or a hydraulic crane, those described in, for example, JP-A-5-202904 and JP-A-7-63203 are known.

FIG. 8 shows a hydraulic drive device disclosed in Japanese Patent Application Laid-Open No. 5-202904.

In FIG. 8, an open center type directional control valve 50- is connected to a supply path 3 for a discharge flow rate from a variable displacement type hydraulic pump 1 which is driven to rotate by a motor (not shown).
1, 50-2, 50-3 are connected, and the actuators 60-, 6-2, 60-
3 is drive-controlled. A center is provided in each of the directional control valves 50-1, 50-2, and 50-3 in the bypass passage 80 branched from the supply path 3, and is linked so that the opening degree becomes narrower as the switching amount of these directional control valves increases. A bypass throttle 51 (hereinafter referred to as “bypass throttle”) is provided, and a flow meter 61 capable of detecting the bypass flow rate is disposed downstream of the most downstream bypass throttle 51 provided in the bypass passage 80. Is input to the controller 60 via a signal line.

[0005] The controller 60 performs a negative flow rate control operation for decreasing or increasing the amount of tilt of the hydraulic pump 1 based on an input signal, that is, an increase or decrease of the detected flow rate, and outputs an output signal based on the negative control. The hydraulic pump 1 is guided to the device 62 so as to be able to electrically control the negative flow rate. 70 is a relief valve for defining the maximum pressure of the main circuit.

[0006] Such a hydraulic drive device using an electric negative flow rate control is a technique aimed at replacing a hydraulic negative flow rate control. FIG. 9 shows a hydraulic drive device based on the hydraulic negative flow rate control. Note that, in FIG. 9, portions denoted by the same reference numerals as those in FIG. 8 represent equivalent portions.

FIG. 9 differs from FIG. 8 in that the bypass flow rate is detected by pressure and that the tilt control device of the hydraulic pump is of a hydraulic type. That is, the bypass passage 80
Direction switching valves 50-1, 50-2, 50-3 provided in
A negative control valve 54 comprising a throttle 52 and a relief valve 53 downstream of the most downstream bypass throttle 51
(Hereinafter referred to as a negative control valve), a pressure signal (hereinafter referred to as a negative control pressure) generated by the negative control valve 54 is guided to a hydraulic displacement control device 56 via a signal line 55, and a hydraulic pump is provided based on the increase / decrease of the negative control pressure. Negative flow rate control is performed hydraulically so as to decrease or increase the amount of tilt in (1).

In such a hydraulic drive device, for example, if none of the directional control valves 50-1, 50-2, 50-3 is operated and is in the neutral state in the figure, the opening amount of the bypass throttle 51 in the bypass passage 80 is reduced. Both are large, and the bypass flow rate supplied to the throttle 52 of the negative control valve 54 increases. As a result, the negative control pressure generated at the throttle 52 increases,
The tilt control device 56 works so that the tilt amount of the hydraulic pump 1 becomes small, so that the discharge flow rate of the hydraulic pump 1 is reduced to a preset small flow rate.

Further, for example, the directional control valves 50-1 and 50
When at least one of -2 and 50-3 is operated, the opening amount of the bypass throttle 51 in the bypass passage 80 decreases according to the operation amount, and the bypass flow rate supplied to the throttle 52 also decreases. For this reason, the negative control pressure decreases, and the tilt control device 56 operates to increase the tilt amount. Therefore, the discharge flow rate of the hydraulic pump 1 is increased to a large flow rate. If the amount of operation further increases and the bypass throttle 51 of the direction switching valve is shut off, the bypass flow rate is lost and no negative control pressure is generated, and the tilt control device 56 works so as to have the maximum tilt amount. The discharge flow rate is maximum.

FIG. 10 shows a hydraulic drive device described in Japanese Patent Application Laid-Open No. 7-63203.

In FIG. 10, a supply path 3 from a hydraulic pump 1 is connected to a closed center type directional control valve 5-1 and 5-1.
2,..., 5-j are connected, and a bleed-off valve 90 is provided in the bypass passage 4 branched from the supply passage 3.
Reference numerals 9-a and 9-b denote, for example, electric operation lever devices which are operated by an operator.
The symbol a indicates an operation signal S1 for driving the direction switching valve 5-1 and the bleed-off valve 8 for the actuator 6-1 and the direction switching valve 5-2 and the bleed-off valve 8 for the actuator 6-2. Operation signal S2 can be output alone or in combination.
-B is capable of outputting an operation signal Sj for driving another direction switching valve, for example, the direction switching valve 5-j and the bleed-off valve 8, and the operation signals S1, S2, and Sj are transmitted through respective signal lines. It is input to the controller 10.

The controller 100 has a calculation / storage function, processes the operation signals S1, S2, Sj from the operation lever devices 9-a, 9-b input to the controller 100, and processes the operation signals S1, S2, Sj to provide the direction switching valve 5-1. , 5-2 and 5-j, and a drive signal Io for driving the bleed-off valve 90.

Therefore, in the conventional hydraulic drive device constructed as described above, the controller 100 calculates and outputs based on the operation signal from the operation lever device, and accordingly, the respective direction switching valves 5-1 and 5-. 2,5-j and the bleed-off valve 90 are switched.

[0014]

In a hydraulic shovel using this type of hydraulic drive device, an ordinary engine is used as a prime mover 7 which is a drive source of a hydraulic pump. There are digging and loading work that requires the speed of the actuator (that is, large flow rate, high engine speed and high output), and leveling work that requires fine operability (that is, small flow rate, low engine speed and low output). Actually, the engine speed is variously set according to the work content. In the case where the conventional hydraulic drive device configured as described above is used, the hydraulic pump 1
The rotation speed of the engine (motor)
The following problems arise. FIG. 11 to FIG.
This will be described.

FIG. 11 shows the relationship between the bypass flow rate and the pump negative flow rate control of the hydraulic drive device shown in FIG.

In FIG. 11, the first quadrant shows the relationship between the bypass flow rate Qt and the negative control pressure Pn, which is a pressure loss characteristic set by the throttle 52 of the negative control valve 54 for detecting the bypass flow rate. In a relationship.

Pn = k1 · Qt (1) The second quadrant is the negative control pressure Pn and the tilt amount Dp of the hydraulic pump 1.
This is a negative flow rate control characteristic set in the tilt control device 56, and has the following relationship.

Dp = Do−k2 · Pn (2) The third quadrant shows the relationship between the pump 1 tilt amount Dp and the discharge flow rate Qp of the hydraulic pump 1, and the discharge flow rate Qp of the hydraulic pump 1 is It is proportional to Ne.

Qp = k3 · Dp · Ne (3) Accordingly, the fourth quadrant shows the relationship between the bypass flow rate Qt and the negatively controlled pump discharge flow rate Qp.

Therefore, these relations are repeated such that a flow rate multiplied by the number of engine revolutions by the pump tilt amount Dp determined for the negative control pressure Pn corresponding to the bypass flow rate Qt is discharged from the hydraulic pump, Negative flow control is performed.

Here, when all the directional control valves are in operation neutral, the entire discharge flow rate of the hydraulic pump 1 is the bypass flow rate. That is, Qp = Qt (4). Therefore, the pump discharge flow rate Qp in the neutral state with respect to the rotation speed Ne of the prime mover 7 can be calculated from the above equations (1) to (3) by using the characteristic line of Dp = Do−k1 · k2 · Qt in FIG.
= K3 · Dp · Ne as an intersection of characteristic lines.
Therefore, when the rotation speed Ne = No, the intersection becomes point A. For example, when Ne = No / 2 where the rotation speed is reduced by half, the intersection becomes point B, and the pump discharge flow rate at the time of neutralization with the decrease in rotation speed, that is, Pump minimum discharge flow is from Q _PminA to Q
_{It turns} out that it falls to _PminB .

As described above, a decrease in the minimum discharge flow rate of the hydraulic pump 1 due to a decrease in the number of revolutions causes the following problem.

FIG. 13A shows the opening areas of the meter-in throttle and the center bypass throttle set with respect to the stroke of the open center type directional control valve. As the stroke increases, the opening area of the center bypass stop decreases, and the opening area of the meter-in stop increases.

FIG. 13B shows the discharge pressure limit (maximum possible discharge pressure) of the hydraulic pump 1 with respect to the stroke.
The discharge pressure limit of the hydraulic pump 1 for this stroke is
It is determined from the following equation based on the center bypass throttle and the pump minimum discharge flow rate according to the rotation speed of the prime mover.

Ps = (Q _pmin / C · a) ² (5) Ps: pump discharge pressure limit Q _pmin : pump minimum discharge flow rate a: opening area of center bypass throttle (center bypass opening) C: constant pump discharge pressure limit Ps in the center bypass opening a same stroke when the pump minimum discharge flow rate Q _pmin with decreasing rotational speed is reduced is lowered. Therefore, even if the actuator load pressure is the same,
Unless the center bypass is narrowed by making the stroke larger, the pump discharge pressure for driving the actuator cannot be secured. Therefore, even if the stroke is performed as shown in FIG. 3C, the meter-in flow rate cannot be obtained, and the actuator does not move. As the dead zone increases, the effective stroke for controlling the meter-in flow rate decreases, so that the operability deteriorates. This is referred to as "retraction of metering" in the present specification. The regression of the metering becomes more remarkable as the minimum discharge flow rate of the pump decreases (as the rotation speed of the prime mover decreases) or as the load pressure increases.

Further, the decrease in the minimum discharge flow rate of the hydraulic pump 1 due to the decrease in the number of revolutions causes the following problem.

Returning to FIG. 11, the relationship between the bypass flow rate and the pump discharge flow rate under the negative flow rate control is shown in the fourth quadrant. Here, since the negative flow rate control increases the pump discharge flow rate according to the decrease of the bypass flow rate,
The difference between the pump discharge flow rate and the bypass flow rate is the meter-in flow rate. For example, when the rotation speed of the motor is Ne = No, the characteristic of the pump discharge flow rate increases as the bypass flow rate decreases and reaches the maximum flow rate from the point A at the time of neutral, and the bypass discharge flow rate characteristic is subtracted from the pump discharge flow rate characteristic. The broken line indicates the meter-in flow rate characteristic.

However, although this bypass flow rate is necessary for control, it is an energy loss for discharging a part of the pump discharge flow rate to the tank through the bypass throttle.
Therefore, when the rotation speed of the motor is Ne = No (high rotation), the flow rate is high and the output is high, and it can be said that this energy loss is apparently small.
In the case of o / 2, the pump discharge flow rate indicated by the solid line and the meter-in flow rate characteristic indicated by the alternate long and short dash line are obtained from the neutral point B, and the energy loss due to the bypass flow rate becomes extremely large. This is because the control characteristics of the tilt control device shown in the second quadrant are uniquely set.

As described above, in the hydraulic drive system using the hydraulic negative flow rate control, a problem arises with respect to a decrease in the rotation speed of the prime mover which is a driving source of the pump.

Further, in the electric hydraulic drive device shown in FIG. 8, it is possible to make the negative flow control characteristic variable by taking advantage of the electronic control by the controller 60. However, the opening area of the center bypass throttle is uniquely determined by the stroke of the direction switching valve, and the configuration cannot correct the opening area of the center bypass throttle in relation to the rotation speed of the prime mover. Further, actually, the rotation speed of the prime mover is not detected, and the opening area of the center bypass throttle and the negative flow rate control of the hydraulic pump 1 are not corrected according to the rotation speed of the prime mover. Therefore, a problem similar to that of the hydraulic drive device shown in FIG. 9 occurs with respect to a decrease in the rotation speed of the prime mover.

Further, in the hydraulic drive system shown in FIG. 10, the center bypass throttle portion of the open center type directional control valve as shown in FIGS. 8 and 9 is separated from the directional control valve.
By installing one bleed-off valve independently in the bypass passage, a closed center type directional control valve that can simplify the valve structure is used, while controlling the bypass flow rate like an open center type directional control valve. The actuator can be driven.

However, even in this hydraulic drive device, the rotational speed of the prime mover is not detected, and the opening area of the bleed-off valve and the negative flow rate control of the hydraulic pump 1 are corrected according to the rotational speed of the prime mover. Has not gone. Therefore, a problem similar to that of the hydraulic drive device shown in FIG. 9 occurs with respect to a decrease in the rotation speed of the prime mover.

A first object of the present invention is to drive the actuator while controlling the bypass flow rate using a closed center type directional control valve, and to prevent the metering from retreating due to a decrease in the rotation speed of the prime mover. It is to provide a hydraulic drive.

A second object of the present invention is to drive the actuator while controlling the bypass flow rate by using a closed-center type directional control valve, and to suppress energy loss due to the bypass flow rate against a decrease in the rotation speed of the prime mover. It is to provide a hydraulic drive device which can be used.

[0035]

[Means for Solving the Problems]

(1) In order to achieve the first object, the present invention provides a motor, a variable displacement hydraulic pump rotationally driven by the motor, and a plurality of hydraulic pumps driven by pressure oil discharged from the hydraulic pump. Actuator, a closed center type directional control valve for controlling the flow of pressure oil supplied to each of the actuators from the hydraulic pump,
A bleed-off valve disposed in a bypass passage connecting the hydraulic pump and the tank, an operation device for outputting operation signals for driving the directional switching valve and the bleed-off valve, and a preset negative flow rate control A hydraulic drive device comprising a regulator device that controls a discharge capacity of the hydraulic pump according to a bypass flow rate flowing out of the bleed-off valve based on characteristics, wherein a first detection unit that detects a rotation speed of the prime mover; An operation signal from an operating device and a rotation speed signal from the first detection means are input, and as the operation signal increases, the opening area of the bleed-off valve is reduced, and the rotation of the prime mover is controlled by the input rotation speed signal. As the number decreases, a correction is made to further reduce the opening area of the bleed-off valve for the same operation signal. It shall comprise a offs valve control means.

The provision of such a bleed-off valve control means enables the bleed-off valve to be properly throttled in accordance with the rotation speed during low-speed operation of the prime mover. Is kept almost constant, metering is prevented from retreating, and operability equivalent to that at the time of high-speed rotation can be maintained.

(2) In the above (1), preferably,
The bleed-off valve control means reduces the opening area of the bleed-off valve so that the discharge pressure limit of the hydraulic pump increases as the operation signal increases, and controls the same operation signal when the rotation speed of the prime mover changes. The opening area of the bleed-off valve is reduced as the rotation speed of the prime mover is reduced so that the discharge pressure limit of the hydraulic pump is kept constant.

(3) In the above (1), preferably, the bleed-off valve control means calculates a coefficient based on a current rotation speed based on the input rotation speed signal and a preset reference rotation speed. A first calculating means, a second calculating means for calculating a reference opening area, which is an opening area at a reference rotation speed of the bleed-off valve, according to an operation signal for driving the direction switching valve, respectively; A third calculating means for calculating a target opening area of the bleed-off valve based on the reference opening area obtained by the calculating means and the coefficient obtained by the first calculating means; And a fourth calculating means for calculating a drive signal for driving the bleed-off valve based on the obtained target opening area.

(4) In the above (3), preferably, the second arithmetic means includes an operation signal for driving each of the direction switching valves, an operation signal set in advance, and an opening area element of the bleed-off valve. A fifth calculating means for calculating each opening area element of the bleed-off valve based on each opening characteristic which is a functional relationship of the following, and based on each opening area element obtained by the fifth calculating means. And a sixth calculating means for calculating a reference opening area of the bleed-off valve. (5) Further, in the above (4), preferably, the reference opening area of the bleed-off valve by the sixth calculating means is ,
According to the condition determination based on each of the opening area elements obtained by the fifth arithmetic means, if at least one of these opening area elements is closed, the reference opening area becomes 0; The opening area is a value determined to be the reciprocal of the square root of the reciprocal sum of the square of each opening area element.

(6) In the above (3), preferably, the target opening area of the bleed-off valve by the third arithmetic means is determined by the coefficient obtained by the first arithmetic means and the second arithmetic means. It is the product of the reference opening area obtained in the above.

(7) In order to achieve the second object, the present invention provides the hydraulic drive device according to any one of the above (1) to (3), wherein a second detecting means for detecting the bypass flow rate;
The bypass flow rate signal from the second detection means and the rotation speed signal from the first detection means are input, and the discharge flow rate of the hydraulic pump is increased as the bypass flow rate by the bypass flow rate signal decreases, and the input rotation speed is increased. A pump flow control means for correcting the negative flow control characteristic of the hydraulic pump so that the bypass flow for the same operation signal decreases as the rotation speed of the prime mover according to the number signal decreases.

By providing such a pump flow control means, the rate of decrease in the opening area of the bleed-off valve by the bleed-off valve control means when the rotation speed of the prime mover is reduced and the discharge flow rate of the hydraulic pump by the pump flow control means are reduced. By properly associating the ratios, during low-speed operation of the prime mover, the bleed-off valve is appropriately narrowed according to the rotation speed as described in (1) above to prevent retreating of metering, and to reduce the bypass flow rate according to the rotation speed. , The negative flow rate control characteristic of the hydraulic pump is corrected, and the energy loss due to the bypass flow rate can be suppressed.

(8) In the above (7), preferably,
The pump flow rate control means reduces the negative flow rate so as to decrease the discharge flow rate of the hydraulic pump at the same rate as the reduction rate of the opening area of the bleed-off valve by the bleed-off valve control means as the rotation speed of the prime mover decreases. This is for correcting the control characteristics.

(9) In the above (8), preferably, when the preset reference rotation speed is No and the current rotation speed based on the input rotation speed signal is Ne, the bleed-off valve control means controls the bleeding. The opening area of the off valve and the decrease rate of the discharge flow rate of the hydraulic pump by the pump flow rate control means are Ne / No, respectively.

(10) In the above (7), preferably, the pump flow rate control means is based on a current bypass flow rate based on the input bypass flow rate signal and a coefficient obtained by the first arithmetic means. A seventh calculating means for calculating a target displacement of the hydraulic pump, and an eighth calculating means for calculating a drive signal for driving the regulator device of the hydraulic pump based on the target displacement obtained by the seventh calculating means. Computing means.

(11) Further, in the above (10), preferably, the coefficient by the first calculating means is a ratio obtained by dividing the current rotational speed by the reference rotational speed.

(12) In the above (10), preferably, the target displacement of the hydraulic pump by the seventh calculating means is obtained by using the bypass flow rate as an input variable and the reference gradient by the first calculating means. It is obtained by a linear proportional function relationship consisting of the slope and the intercept divided by the coefficient and the limiter calculation for setting the upper and lower limits.

[0048]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydraulic drive device according to the present invention will be described below with reference to FIGS.

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

In FIG. 1, reference numeral 1 denotes a variable displacement hydraulic pump which is driven to rotate by a prime mover 7.
Is a supply path 3 and a closed center type directional control valve 5-
, 6-j in parallel through 1, 5-2,..., 5-j. , 6-j are driven. Also,
By operating the direction switching valves 5-1, 5-2,.
The flow rate and the flow direction of the pressure oil supplied to 2, ..., 6-j are controlled. The displacement (displacement volume) of the hydraulic pump 1 is controlled by a regulator device, that is, the displacement control device 2, and the discharge flow rate is controlled.

A bypass passage 4 is provided for connecting the supply passage 3 from the hydraulic pump 1 to the tank T. The bypass passage 4 is provided with a bleed-off valve 8 composed of an electromagnetic valve and a downstream of the bleed-off valve 8. A flow meter 11 for detecting a bypass flow rate is arranged on the side, and a bypass flow rate signal Sq, which is an electric signal corresponding to the detected flow rate, is input to a controller 10 described later in detail via a signal line.

Further, a rotation speed detection sensor 12 for detecting the rotation speed of the prime mover 7 which is the driving source of the hydraulic pump 1 is provided, and a rotation speed signal S which is an electric signal corresponding to this rotation speed is provided.
n is input to the controller 10 via the signal line.

Reference numerals 9-a and 9-b denote, for example, an electric operation lever device operated by an operator. The operation lever device 9-a includes a direction switching valve 5-1 for the actuator 6-1 and a bleed-off. An operation signal S1 for driving the valve 8 and a direction switching valve 5-2 for the actuator 6-2.
And the operating signal S2 for driving the bleed-off valve 8 can be output alone or in combination, and the operating lever device 9-b is provided with another directional switching valve, for example, the directional switching valve 5-j and the bleed-off. An operation signal Sj for driving the valve 8 can be output, and the operation signals S1, S2, and Sj are input to the controller 10 via respective signal lines.

The controller 10 has a calculation and storage function, and operates the operation lever device 9-
a, 9-b to process the operation signals S1, S2, Sj, the bypass flow rate signal Sq, and the rotation speed signal Sn to drive the direction switching valves 5-1, 5-2, 5-j.
1, I1 ', I2, I2', IJ, IJ ', a drive signal It for driving the bleed-off valve 8, and a drive signal Ip for driving the tilt control device 2 of the hydraulic pump 1.

First, the processing functions of the controller 10 regarding the drive control of the direction switching valve and the bleed-off valve will be described.

As shown in FIG. 2, the controller 10
A first arithmetic function 20 related to the prime mover speed, second, third and fourth arithmetic functions 30, 31 and 32 related to drive control of the bleed-off valve 8, and a ninth related to drive control of the direction switching valve. The second arithmetic function 30 relating to the drive control of the bleed-off valve 8 includes fifth and sixth arithmetic functions 34 and 35.

The first arithmetic function 20 has a coefficient kn (= Ne / Ne), which is a ratio between the current rotational speed Ne based on the detected rotational speed signal Sn and a preset reference rotational speed No, which will be described in detail later.
No) is calculated.

The second arithmetic function 30 is provided with a directional control valve 5-
1, 5-2 and 5-j, respectively.
Reference rotational speed No of bleed-off valve 8 according to S2 and Sj
The reference opening area, which is the opening area at the time, is calculated.

That is, in the second arithmetic function 30,
The fifth arithmetic function 34 is set (stored) in consideration of the operation signal S1 for driving the direction switching valve 5-1 for the actuator 6-1 in FIG. 1 and a desired operation mode of the actuator 6-1 in advance. Based on the opening characteristic, which is a functional relationship between the operation signal S1 and the opening area element a1 of the bleed-off valve 8,
The opening area element a1 is calculated. The actuator 6
An operation signal S2 for driving the direction switching valve 5-2 for -2,
An operation signal S2 and a bleed-off valve 8 which are set (stored) in advance in consideration of a desired operation form of the actuator 6-2
The opening area element a2 is calculated based on the opening characteristic which is a functional relationship with the opening area element a2. Similarly, an operation signal Sj for driving the direction switching valve 5-j for the actuator 6-j, an operation signal Sj set (stored) in advance in consideration of a desired operation mode of the actuator 6-j, and the bleed-off valve 8 The opening area element aj is calculated based on the opening characteristic which is a functional relationship with the opening area element aj. In addition,
These opening characteristics are set in accordance with the reference rotation speed No, and may be different depending on, for example, each actuator. In both cases, the opening area element gradually decreases from the maximum opening in response to an input operation from the neutral time of the operation signal. For example, the stroke of the center bypass throttle with respect to the stroke of the conventional open center type directional control valve is changed. The opening area characteristic can be replaced and used.

The sixth arithmetic function 35 is the fifth arithmetic function 3
The reference opening area At of the bleed-off valve 8 is calculated based on the opening area elements a1, a2, aj obtained in step 4.
In the sixth arithmetic function 35, for example, a pressure / flow rate characteristic of a center bypass restricting section group of a conventional open center type directional control valve arranged in series on a bypass passage from a discharge flow path of a hydraulic pump to a tank is provided. When the aperture is replaced by only one aperture, the condition determination element 35-1 and the operation element 3
5-2 and 35-3 are provided, and the reference opening area At of the bleed-off valve 8 at the reference rotation speed No is calculated by these. That is, the condition determination element 3 based on the opening area elements a1, a2, and aj obtained by the fifth arithmetic function 34
By 5-1, if at least one of these area elements is closed, the operation element 35-3 is selected, otherwise, the operation element 35-2 is selected, and the reference opening area At is obtained.

The third arithmetic function 31 is the second arithmetic function 3
0 and the first arithmetic function 20 described above.
The target opening area A (= kn · At) of the bleed-off valve 8 is calculated by multiplying by the coefficient kn obtained in (1).

The fourth arithmetic function 32 is a third arithmetic function 3
1 and a drive signal It for the bleed-off valve 8 based on a functional relationship between the target opening area A set in advance and the preset target opening area A and the drive current It for the bleed-off valve 8.
Is calculated and output. Note that the functional relationship described above is such that the drive current It takes the maximum value when the target opening area A is 0, and the drive current It decreases as the target opening area A increases.

The ninth operation function 33 is a function of the actuator 6
An operation signal S1 for driving the direction switching valve 5-1 for -1;
Direction switching valve 5 with operation signal S1 set (stored) in advance
-1 based on the functional relationship with the drive signals I1 and I1 ',
The drive signals I1 and I1 'for the direction switching valve 5-1 are calculated and output. Also, a direction switching valve 5- for the actuator 6-2.
2 and a drive signal I2, I of the direction switching valve 5-2 between an operation signal S2 that is set (stored) in advance.
Based on the functional relationship with 2 ', the drive signals I2 and I2' for the direction switching valve 5-2 are calculated and output. Similarly, a function of an operation signal Sj for driving the direction switching valve 5-j for the actuator 6-J, a function of an operation signal Sj set (stored) in advance and driving signals Ij, Ij of the direction switching valve 5-j. Based on the relationship, drive signals Ij and Ij 'for direction switching valve 5-j are calculated and output. Note that the above-described functional relationship is such that when the operation signal is neutral, that is, when the operation signal is 0, the drive current takes a minimum value, and the value of the drive current to the direction control side intended with the input operation from the neutral time is As it increases, the driving current in the other direction has a relationship of maintaining a minimum value.

The operation of the directional control valve and the bleed-off valve of the present embodiment configured as described above is as follows.

For example, if the rotation speed Ne of the prime mover 7 is operating at the reference rotation speed No, the rotation detection sensor 1
2, the rotation speed signal Sn is input to the controller 10, and the first arithmetic function 20 of the controller 10 determines kn = Ne / No = No / No = 1 and a coefficient kn = 1. Further, operation signals S1 and S1 that are operated neutral or input from the operation lever device 9 intended to stop or drive the actuator 6
2 and Sj are input to the controller 10. The ninth operation function 33 of the controller 10 responds to the respective operation signals S1, S2, and Sj by using the respective drive currents I1,
I1 ',..., IJ, Ij' are obtained, and these drive currents are supplied to the drive units of the respective directional control valves 5. Thereby, each directional control valve is switched to the intended neutral state or directional side.

At the same time, these operation signals S1, S
2, Sj, the opening area elements a1, a of the bleed-off valve 8 by the fifth arithmetic function 34 of the second arithmetic function 30.
2, aj are obtained, respectively, and these opening area elements a
The reference opening area At is obtained by the third arithmetic function 35 based on 1, a2, and aj.

That is, at least one of these area elements is determined by the condition determining element 35-1 based on the opening area elements a1, a2 and aj obtained by the fifth arithmetic function.
If one is closed (opening area element = 0), operation element 3
5-3 is selected and the reference opening area At is obtained as At = 0. Otherwise, the operation element 35-2 is selected, and the reference opening area At is calculated as follows.

[0068]

(Equation 1)

The reference opening area At is determined by one of the arithmetic expressions. Here, the reference opening area At is determined at least by one of the cases as described above.
When one opening area element is closed (opening area element = 0), 1 / ai ² (i =
1 to j) = ∞, and the calculation becomes impossible.

Then, the third arithmetic function 31 multiplies the reference opening area At by the coefficient kn = 1 obtained by the first arithmetic function 20 to obtain the target opening area A of the bleed-off valve 8 as follows: A = kn・ At = At is obtained.

Further, a drive current It corresponding to the above-described target opening area A is obtained by the fourth arithmetic function 32,
This drive current is supplied to the drive section of the bleed-off valve 8. As a result, the bleed-off valve 8 has the third arithmetic function 3
The target opening area A obtained in step 1 is switched.

Here, for example, if the rotation speed of the prime mover 7 is set to be halved and the motor 7 is operated at the rotation speed Ne = No / 2, this is detected by the rotation speed detection sensor 12 and the first arithmetic function 20 of the controller 10 is performed. Kn = Ne / No = (No / 2) / No = 1/2 and the coefficient kn = 1/2 are obtained.

In the directional control valve, the respective drive currents are obtained by the ninth arithmetic function 33 of the controller 10 based on the respective operation signals S1, S2, and Sj, as described above. Switch to the intended state.

At the same time, these operation signals S1, S
2, Sj, the opening area elements a1, a of the bleed-off valve 8 by the fifth arithmetic function 34 of the second arithmetic function 30.
2, aj are obtained, respectively, and these opening area elements a
The reference opening area At is obtained by the third arithmetic function 35 based on 1, a2, and aj.

That is, the condition determining element 35-1 based on the opening area elements a1, a2, aj obtained by the fifth calculating function 34 determines whether one of the calculating element 35-3 and the calculating element 35-2. Is selected, and the reference opening area At is obtained.

Then, the third arithmetic function 31 multiplies the reference opening area At by the coefficient kn = １ ／ determined by the first arithmetic function 20 to obtain the target opening area A of the bleed-off valve 8 as A = Kn · At = At / 2.

Further, a drive current It corresponding to the above-described target opening area A is obtained by the fourth arithmetic function 32.
Thereby, the bleed-off valve 8 is switched to the target opening area A (= At / 2) obtained by the third arithmetic function 31.

Therefore, when the motor 7 is operated with the rotation speed set to half, the bleed-off valve 8 has an opening area that is 1/2 times the reference rotation speed, that is, the first calculation function. The drive control is performed so that the opening amount becomes a coefficient kn (= Ne / No) times as large as 20.

The purpose of such control is to prevent the metering from retreating due to a decrease in the minimum discharge flow rate of the hydraulic pump 1 due to a decrease in the rotational speed, which is a technical problem of the present invention. In other words, the bleed-off valve 8 is controlled so as to be further narrowed down by a factor (coefficient kn).

Here, in the conventional hydraulic drive device having an open center type directional control valve, metering retreats due to a decrease in the minimum discharge flow rate of the hydraulic pump 1 due to a decrease in the rotation speed as described above.

That is, in the conventional hydraulic drive, FIG.
As shown in 3 (B), the pump discharge pressure limit Ps in the center bypass opening a same stroke when the pump minimum discharge flow rate Q _pmin with the decrease of the engine rotational speed is lowered is lowered. Therefore, even if the actuator load pressure is the same, the pump discharge pressure for driving the actuator cannot be secured unless the stroke is made larger and the center bypass is narrowed. Therefore, even if the stroke is made as shown in FIG. Meter-in flow rate cannot be obtained,
The dead zone in which the actuator does not move increases, and the effective stroke for controlling the meter-in flow rate decreases, so that the operability deteriorates. That is, the metering retreats.

In this embodiment, the negative flow rate control characteristic of the hydraulic pump is set so that the decrease in the pump minimum discharge flow rate due to the decrease in the rotational speed becomes a coefficient kn times as a decrease ratio from the reference rotational speed. That is, it is set as in the following equation.

Q _pmin = kn · Q _pmin ^* (7) Q _pmin ^* : pump minimum discharge flow rate at reference rotation speed In this case, the above-described pump discharge pressure limit Ps is as follows.

Ps = ( _Qpmin / C · A) ² (8) = (kn · _Qpmin ^* / C · kn · At) ² = ( _Qpmin ^* / C · At) ² = Ps ^* Ps ^* : Reference Pump discharge pressure limit at rotation speed At: Open area of bleed-off valve at reference rotation speed That is, even if the pump minimum flow rate decreases at a lowering of the motor rotation speed, a pump discharge pressure limit equal to that at reference rotation speed No is obtained. Can be Therefore, retreat of metering can be prevented, and the same operability can be maintained.

Next, a description will be given of the processing flow of the tilt control of the pump related to the negative flow rate control which obtains such a relationship.

FIG. 3 is a characteristic diagram relating to the negative flow rate control of the present invention. The above-mentioned relationship, that is, the decrease in the minimum pump discharge flow rate due to the decrease in the rotational speed becomes a coefficient kn times as a decrease ratio from the reference rotational speed. It is a set negative flow control characteristic of the hydraulic pump 1.

In this case, the pump minimum discharge flow rate when the reference rotation speed Ne = No is point A (Q _pmin ^* ), and when the rotation speed is reduced by half to Ne = No / 2, point C (Q _pmin ^* / 2) The relational expression is constructed so that That is, the relationship is
Slope −K / kn based on intercept Do and the above-described coefficient kn
Thus, the tilt amount Dp of the hydraulic pump 1 related to the negative flow rate control may be related to the bypass passing flow rate Qt.

Accordingly, the controller 10 serves as a portion for controlling the tilt control device 2 of the hydraulic pump 1 so as to obtain the negative flow control characteristics shown in FIG.
As shown in FIG. 7, seventh and eighth arithmetic functions 40 and 4 related to the drive of the pump negative flow rate control and tilt control device.
And 1.

The seventh arithmetic function 40 is a hydraulic pump 1 that is negatively flow-controlled based on the current bypass flow rate Qt based on the detected bypass flow rate signal Sq and the coefficient kn obtained by the first arithmetic function 20 described above. Of the target displacement amount (target displacement volume) Dp. In the seventh arithmetic function 40, the prime mover 7 which is a driving source of the hydraulic pump 1 is
Negative flow rate control characteristics variable according to the number of rotations of the
That is, there are provided calculation elements 40-1 and 40-2 indicating the functional relationship between the signal Sq and the pump displacement amount Dp which are set in advance in consideration of the variable characteristics of the inclination as shown in FIG. A target tilt amount Dp of the hydraulic pump 1 controlled by the negative flow rate is calculated. That is, the bypass flow rate Sq and the coefficient k obtained by the first arithmetic function 20 are used.
n = D-Do- (K
/ Kn) Qt (slope K / kn, intercept Do, bypass flow rate Qt) and the target tilt amount Dp of the hydraulic pump 1 are obtained via the limiter of the computing element 40-2.

The eighth arithmetic function 41 is the seventh arithmetic function 4
0 based on the functional relationship between the target tilt amount Dp obtained at 0 and the preset (stored) target tilt amount Dp and the drive current Ip of the tilt control device 2 of the hydraulic pump 1. Is calculated and output. It should be noted that the above-described functional relationship indicates that as the target tilt amount Dp increases, the drive current I
The relationship is such that the value of p increases.

The operation related to the negative flow rate control of the embodiment configured as described above will be further described with reference to FIG. FIG.
Shows the relationship between the bypass flow rate and the negative flow rate control in the present embodiment.

In FIG. 5, the first quadrant shows the relationship between the bypass flow rate Qt and the electrical flow rate signal Sq corresponding to the bypass flow rate, which is the detection characteristic of the flow meter 11 in FIG. It is in the relationship of the formula.

Sq = k1 '· Qt (9) The second quadrant indicates the relationship between the flow signal Sq and the amount of displacement Dp of the hydraulic pump 1, which is determined by the controller 10 described above.
Are the negative flow rate control characteristics achieved by the calculation and tilt drive by the seventh and eighth calculation functions 40 and 41, and have the following relationship.

Dp = Do− (k2 ′ / kn) · Sq (10) The third quadrant indicates the relationship between the tilt amount Dp of the hydraulic pump 1 and the discharge flow rate Qp of the hydraulic pump 1. The discharge flow rate Qp is proportional to the motor rotation speed Ne.

Qp = k3 · Dp · Ne (11) Therefore, the fourth quadrant indicates the relationship between the bypass flow rate Qt and the negatively controlled pump discharge flow rate Qp.

Accordingly, the hydraulic pump 1 discharges a flow rate that is the engine speed multiplied by the pump displacement Dp determined based on the flow rate signal Sq and the coefficient kn with respect to the flow rate signal Sq corresponding to the bypass flow rate Qt. Thus, these relationships are repeated, and the negative flow rate control of the present embodiment is performed.

In this case, the relationship between the bypass flow rate Qt and the pump discharge flow rate Qp shown in the fourth quadrant is as described in the above (5) to (5).
The following equation is obtained by developing and organizing the equation (7).

Qp = k3 · Ne · (Do−k1 ′ · k2 ′ · Qt / kn) (12) Here, the minimum discharge flow rate _Qpmin of the hydraulic pump 1 is expressed by the above equation, Qp = Qt, and the operation of the prime mover 7. Rotation speed Ne = kn · N
When rearranging using o, it is shown by the following equation.

[0099]

(Equation 2)

Now, when the prime mover 7 is operated at the reference rotational speed, N
Assuming that e = No, the first arithmetic function 20 determines the coefficient kn = No / No = 1. Therefore, the minimum discharge flow rate Q _pmin ^* at the reference rotation speed is:

[0101]

(Equation 3)

And is shown by point A in FIG. Further, for example, if the operation is performed at Ne = No / 2 where the rotation speed is set to half, the coefficient k is calculated by the first arithmetic function 20 described above.
n = (No / 2) / No = 1/2 is required. Therefore, the minimum discharge flow rate _Qpmin at this rotation speed is:

[0103]

(Equation 4)

The minimum discharge flow rate of the pump is reduced by half as shown by point C in FIG.

That is, according to the negative flow rate control of the present embodiment by the seventh and eighth arithmetic functions 40 and 41 shown in FIG. 4, the decrease in the pump minimum discharge flow rate Q _pmin due to the decrease in the rotation speed of the prime mover 7 is Since the negative flow rate control characteristic of the hydraulic pump 1 can be set so as to be a coefficient kn (Q _pmin = kn · Q _pmin ^* ) as a rate of decrease from the reference rotation speed, the drive control of the bleed-off valve 8 described above is combined. Even if the pump minimum discharge flow rate decreases with a decrease in the motor rotation speed, a pump discharge pressure limit equal to that at the reference rotation speed No can be obtained, so that the metering can be prevented from retreating and the same operability can be obtained. Can be maintained.

Returning to FIG. 5, the fourth quadrant shows the relationship between the bypass flow rate Qt and the pump discharge flow rate Qp subjected to the negative flow rate control in the present invention. Here, also in the negative flow rate control of the present embodiment, the pump discharge flow rate Qp is increased according to the decrease of the bypass flow rate Qt, so that the difference between the pump discharge flow rate Qp and the bypass flow rate Qt is the meter-in flow rate. For example, when the rotation speed of the motor is Ne = No, the pump discharge flow rate Qp increases as the bypass flow rate Qt decreases from the point A at the time of neutral, and becomes a characteristic indicated by a solid line reaching the maximum flow rate. The dashed line obtained by subtracting indicates the meter-in flow rate characteristic. Therefore, when the motor rotation speed Ne = No (high rotation), the flow rate is high and the output is high, and this energy loss is apparently small. In this case, the energy loss in the conventional negative flow rate control shown in FIG. Equivalent to loss.

However, Ne = halved rotation speed =
In the case of No / 2, the pump discharge flow rate Q from the neutral point C
The pump discharge flow rate characteristic of the solid line where p increases and the meter-in flow rate characteristic of the one-dot chain line obtained by subtracting the bypass flow rate therefrom are obtained. Bypass flow rate Qt
Is extremely small. That is, in the present embodiment, the bypass flow rate Qp is reduced by about a factor kn compared to the conventional technique, and when Ne = No / 2, the bypass flow rate Qp can be reduced to about 1/2. Therefore, the energy loss due to the bypass flow rate Qp is extremely small. That is, the seventh line shown in FIG.
According to the negative flow rate control by the eighth arithmetic functions 40 and 41, the energy efficiency can be improved during the low-speed operation of the prime mover.

As described above, according to the present embodiment, at the time of low-speed operation of the prime mover, the bleed-off valve is appropriately narrowed according to the number of revolutions to prevent the metering from retreating, and the same operability as at the time of high-speed operation is obtained. In addition to the above, the negative flow rate control characteristic is corrected in accordance with the number of revolutions, the energy loss due to the bypass flow rate is suppressed, and the energy efficiency can be improved as compared with the related art.

Further, with regard to the control of the opening area of the bleed-off valve, since the pressure / flow rate characteristics of the center bypass restricting section group of the conventional open center type directional control valve are replaced, the closed center type directional control valve can be used. The actuator can be driven while controlling the bypass flow rate by using the directional control valve.
An inexpensive hydraulic drive can be provided.

A second embodiment of the present invention will be described with reference to FIGS. In the above embodiment, both the retraction and the energy loss of the metering due to the decrease in the rotation speed of the prime mover are improved, but the present embodiment improves only the retreat of the metering due to the decrease in the rotation speed of the prime mover. It is. In the figure, functions equivalent to the functions shown in FIGS. 2 and 4 are denoted by the same reference numerals.

In FIG. 6, a controller 10 (see FIG. 1) includes a first arithmetic function 20 relating to the rotation speed of the prime mover as a part for controlling the driving of the direction switching valve and the bleed-off valve.
A, and second and third related to drive control of the bleed-off valve 8.
And a fourth arithmetic function 30, 31, and 32, and a ninth arithmetic function 33 related to the drive control of the directional control valve. The second arithmetic function 30 related to the drive control of the bleed-off valve 8 is the fifth arithmetic function. And a sixth arithmetic function 34, 34. The second to sixth arithmetic functions 30 to 35 are the same as those of the first embodiment shown in FIG.

In FIG. 7, the controller 10
Has seventh and eighth arithmetic functions 40A and 41 as a part for driving and controlling the tilt control device 2 of the hydraulic pump 1, and the seventh arithmetic function 40A is configured to perform the current operation based on the detected bypass flow rate signal Sq. Arithmetic elements 40A-1 and 4A for calculating a target tilt amount (target displacement) Dp of the hydraulic pump 1 that is negatively flow-controlled based on the bypass flow rate Qt.
0-2. The operation element 40-2 and the eighth operation function 41 of the seventh operation function 40A are the same as those of the first embodiment shown in FIG.

The first arithmetic function 20A in FIG. 6 and the seventh arithmetic function in FIG.
The operation element 40-1 of the operation function 40A will be described.

In the hydraulic drive device shown in FIG. 1, if the negative flow rate control of the hydraulic pump 1 is the same as the conventional one, the relationship between the bypass flow rate and the negative flow rate control is the same as that of the conventional open center type shown in FIG. This is the same as that of the hydraulic drive device provided with the switching valve, and the discharge flow rate of the hydraulic pump 1 by the negative flow rate control is represented by the above-described equations (1) to (3) described with reference to FIG.

Pn = k1 · Qt (1) Dp = Do−k2 · Pn (2) Qp = k3 · Dp · Ne (3) Here, the minimum pump discharge flow _{Qpmin at} the rotation speed Ne of the prime mover is (4) From the condition of Q _pmin = Qp = Qt in the equation,

[0116]

(Equation 5)

Are shown. Therefore, the rotation speed Ne = N
o (reference speed) the minimum discharge flow rate Q _pmin ^* and minimum discharge flow rate Q _pmin o'clock arbitrary rotation number of time is known. In FIG. 12, the minimum discharge flow rate decreases from point A when Ne = No to point B as the rotational speed decreases.

If the opening area of the bleed-off valve 8 equivalent to the opening area of the center bypass throttle is not corrected even if the rotation speed Ne of the prime mover decreases, the reference rotation speed Ne =
Assuming that At remains the same as that at the time of No, the pump discharge pressure limit Ps is given by: Ps = (Q _pmin / C · At) ² = (Q _pmin / Q _pmin ^* ) ² · Ps ^* (17) ^* = ( _Qpmin ^* / C.At) ² (18) Ps ^* : The pump discharge pressure limit at the reference rotation speed. Therefore, the pump discharge pressure limit Ps is lowered by the square of the ratio of the minimum pump discharge flow rate Q _pmin ^* in at minimum pump discharge flow rate Q _pmin and reference rotational speed at that time.

Therefore, in such a situation, as described above, the metering is retracted and the operability is deteriorated. To prevent this, the opening area of the bleed-off valve 8 may be further reduced so that the pump discharge pressure limit Ps becomes equal to the pump discharge pressure limit Ps ^* at the reference rotation speed even when the rotation speed decreases. .

That is, the opening area A of the bleed-off valve for satisfying Ps ^* = Ps is determined by setting an arbitrary rotation speed to Ne = kn ·
If you say No,

[0121]

(Equation 6)

Is set so that

The first arithmetic function 20A in FIG. 6 calculates the coefficient k from the relationship between the current rotation number Ne based on the detected rotation number signal Sn and the above-mentioned preset rotation number Ne and coefficient kA.
A is calculated. The third arithmetic function 31 is based on the reference opening area At obtained by the second arithmetic function 30 and the first arithmetic function 2.
Multiply by the coefficient kA obtained at 0A, and bleed-off valve 8
Of the target opening area A (= kA · At) is calculated.

On the other hand, the negative flow rate control of the hydraulic pump 1 is the same as the conventional method. That is, the seventh in FIG.
The calculation element 40-1 of the calculation function 40A has a bypass flow rate S
Characteristic expression D of conventional negative flow rate control based only on q
= Do-KQt (slope K, intercept Do, bypass flow rate Q
The target displacement amount D is calculated using t), and is calculated by the operation element 40-2.
The target tilt amount Dp of the hydraulic pump 1 is obtained through the limiter.

According to the present embodiment configured as described above, at the time of low-speed operation of the prime mover, the bleed-off valve is appropriately narrowed down in accordance with the number of revolutions, to prevent the metering from retreating, and to perform the same operation as during high-speed operation. Nature can be secured.

[0126]

According to the present invention, at the time of low-speed operation of the prime mover, the bleed-off valve is appropriately narrowed according to the number of revolutions to prevent the metering from retreating, thereby ensuring the same operability as during high-speed operation. In addition to this, the negative flow rate control characteristic is corrected according to the number of revolutions, the energy loss due to the bypass flow rate is suppressed, and the energy efficiency can be improved as compared with the related art.

Further, regarding the opening area control of the bleed-off valve, the actuator can be driven while controlling the bypass flow rate by using a closed center type directional switching valve, so that the directional switching valve can be simplified and downsized. And an inexpensive hydraulic drive can be provided.

[Brief description of the drawings]

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

FIG. 2 is a control block diagram relating to control of a direction switching valve and a bleed-off valve by the controller shown in FIG. 1;

FIG. 3 is a characteristic diagram relating to negative flow rate control of the first embodiment.

FIG. 4 is a control block diagram relating to negative flow rate control of the hydraulic pump by the controller of the first embodiment.

FIG. 5 is a relationship diagram between a bypass flow rate and negative flow rate control in the first embodiment.

FIG. 6 is a control block diagram related to control of a direction switching valve and a bleed-off valve by a controller of a hydraulic drive device according to a second embodiment of the present invention.

FIG. 7 is a characteristic diagram relating to negative flow rate control by a controller according to the second embodiment.

FIG. 8 is a configuration diagram of a conventional hydraulic drive device.

FIG. 9 is a configuration diagram of another conventional hydraulic drive device.

FIG. 10 is a configuration diagram of still another conventional hydraulic drive device.

11 is a relationship diagram between a bypass flow rate and negative flow rate control in the hydraulic drive device shown in FIG.

FIG. 12 is a graph showing a relationship between a pump minimum flow rate (tilt amount) and a rotation speed of a motor in a conventional hydraulic drive device.

13A and 13B are diagrams showing characteristics of the conventional hydraulic drive device shown in FIG. 10, wherein FIG. 13A is an opening area diagram with respect to a stroke of a directional control valve, and FIG. The diagram (C) is a meter-in flow rate diagram for the stroke of the directional control valve.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 Variable displacement hydraulic pump 2 Tilt control device (regulator device) 3 Supply path 4 Bypass path 5-1, 5-2, 5-3 Direction switching valve 6-1, 6-2, 6-3 Actuator 7 Motor Reference Signs List 8 bleed-off valve 9 operating lever device 10 controller 11 flow meter 12 rotation speed detection sensor 20; 20A first calculation function (bleed-off valve control means) 30 second calculation function (bleed-off valve control means) 31 third Arithmetic function (bleed-off valve control means) 32 Fourth arithmetic function (bleed-off valve control means) 33 Ninth arithmetic function 34 Fifth arithmetic function 35 Sixth arithmetic function 35-1 Element of sixth arithmetic function 35-2 Element of sixth arithmetic function 35-3 Element of sixth arithmetic function 40; 40A Seventh arithmetic function (pump flow control means) 40-1 Element of seventh arithmetic function 4 -2 seventh element 41 arithmetic function of the eighth arithmetic functions (pump flow rate control means)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Kasuya 650 Kandamachi, Tsuchiura-shi, Ibaraki Pref.

Claims (12)

[Claims] 1. A motor, a variable displacement hydraulic pump rotationally driven by the motor, a plurality of actuators driven by hydraulic oil discharged from the hydraulic pump, and each of the actuators from the hydraulic pump. A closed center type directional control valve for controlling the flow of the supplied pressure oil, a bleed-off valve disposed in a bypass passage connecting the hydraulic pump and the tank, and driving of the directional switch valve and the bleed-off valve And a regulator device for controlling a discharge capacity of the hydraulic pump according to a bypass flow rate flowing out of the bleed-off valve based on a preset negative flow rate control characteristic. A driving device, wherein: a first detecting means for detecting a rotation speed of the prime mover; A signal and a rotation speed signal from the first detection means are input, and as the operation signal increases, the opening area of the bleed-off valve decreases, and as the rotation speed of the prime mover decreases due to the input rotation speed signal. A bleed-off valve control means for correcting the opening area of the bleed-off valve for the same operation signal so as to be further reduced. 2. The hydraulic drive device according to claim 1, wherein the bleed-off valve control means reduces the opening area of the bleed-off valve so that the discharge pressure limit of the hydraulic pump increases as the operation signal increases. The opening area of the bleed-off valve decreases as the rotation speed of the prime mover decreases so that the discharge pressure limit of the hydraulic pump for the same operation signal is kept constant when the rotation speed of the prime mover changes according to the input rotation speed signal. A hydraulic drive device characterized in that the pressure is reduced. 3. The hydraulic drive device according to claim 1, wherein the bleed-off valve control means calculates a coefficient based on a current rotation speed based on the input rotation speed signal and a preset reference rotation speed. Calculating means for calculating a reference opening area, which is an opening area of the bleed-off valve at a reference rotation speed, in accordance with an operation signal for driving the direction switching valve, respectively; A third calculating means for calculating a target opening area of the bleed-off valve based on the reference opening area obtained by the means and the coefficient obtained by the first calculating means; And a fourth calculating means for calculating a drive signal for driving the bleed-off valve based on the target opening area. 4. The hydraulic drive device according to claim 3, wherein said second calculating means is a function of an operation signal for driving each of said direction switching valves, a function of a preset operation signal and an opening area element of a bleed-off valve. Fifth calculating means for calculating each opening area element of the bleed-off valve based on the respective opening characteristics that are related to each other. Based on each opening area element obtained by the fifth calculating means, A sixth calculating means for calculating a reference opening area of the bleed-off valve. 5. The hydraulic drive device according to claim 4, wherein the reference opening area of the bleed-off valve by the sixth calculating means is a condition based on each opening area element obtained by the fifth calculating means. According to the determination, if at least one of these opening area elements is closed, the reference opening area is 0; otherwise, the reference opening area is the reciprocal of the square root of the reciprocal sum of the square of each opening area element. A hydraulic drive device characterized in that the hydraulic drive device has a value determined as follows. 6. The hydraulic drive device according to claim 3, wherein the target opening area of the bleed-off valve by the third arithmetic means is obtained by the coefficient obtained by the first arithmetic means and by the second arithmetic means. A hydraulic drive device characterized by the product of the reference opening area and the reference opening area. 7. The hydraulic drive device according to claim 1, wherein a second detecting means for detecting the bypass flow rate, a bypass flow signal from the second detecting means, and the first detecting means. , The discharge flow rate of the hydraulic pump is increased as the bypass flow rate by the bypass flow rate signal is reduced, and the bypass for the same operation signal is reduced as the rotational speed of the prime mover is reduced by the input speed signal. A hydraulic drive device further comprising a pump flow control means for correcting the negative flow control characteristic of the hydraulic pump so as to reduce the flow. 8. The hydraulic drive system according to claim 7, wherein the pump flow rate control means is configured to reduce the bleed-off valve opening means by the bleed-off valve control means in proportion to a decrease rate of the opening area of the valve as the rotation speed of the prime mover decreases. A hydraulic drive device, wherein the negative flow control characteristic is corrected so as to reduce the discharge flow rate of the hydraulic pump by a ratio. 9. A bleed-off valve controlled by said bleed-off valve control means, wherein a predetermined reference rotation speed is No, and a current rotation speed by an input rotation speed signal is Ne. Opening area of the hydraulic pump and the reduction rate of the discharge flow rate of the hydraulic pump by the pump flow rate control means,
Hydraulic drive devices characterized by Ne / No. 10. The hydraulic drive device according to claim 7, wherein
A pump calculating unit configured to calculate a target displacement of the hydraulic pump based on a current bypass flow rate based on the input bypass flow rate signal and the coefficient obtained by the first calculating unit; A hydraulic drive device comprising: an eighth calculation means for calculating a drive signal for driving the regulator device of the hydraulic pump based on the target displacement obtained by the seventh calculation means. 11. The hydraulic drive device according to claim 10, wherein a coefficient obtained by said first calculating means is a ratio obtained by dividing a current rotational speed by a reference rotational speed. 12. The hydraulic drive device according to claim 10, wherein the target displacement of the hydraulic pump by the seventh calculating means is a coefficient obtained by using the bypass flow rate as an input variable and determining the reference gradient by the first calculating means. A hydraulic drive apparatus characterized in that the hydraulic drive apparatus is obtained by a first-order proportional functional relationship consisting of an inclination and an intercept divided by (1) and limiter calculations for setting upper and lower limits.