JPH1181389A - Hydraulic controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a shock at the time of slewing start regardless of the posture of a working front by changing the travel of a bleed-off valve in response to the reach of the working front calculated on the basis of the detecting value of a posture detecting means. SOLUTION: A relief valve 22 as a main safety valve and a variably operated bleed-off valve 35 are installed to pipelines 20b, 20c branched from the discharge path 20a of a hydraulic pump 20 respectively. The reach arithmetic section of the controller 31 mounted on a working front 3 calculates the front reach (r) of the working front 3 on the basis of angles θ1, θ2 detected by a boom angle sensor 13 and an arm angle sensor 14 and the beforehand stored size of the working front 3. The objective travel of the bleed-off valve 35 is computed on the basis of functional relation, in which objective travel is increased with the reduction of the reach (r) of the working front 3 and the front reach (r). Accordingly, slewing driving pressure corresponding to the reach of the working front 3 at the time of the starting of a revolving superstructure 2 can be set, and a shock at the time of starting can be prevented regardless of the posture of the working front 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for a construction machine, and more particularly to a construction machine such as a hydraulic shovel having an upper swing body and an articulated work front.
The present invention relates to a hydraulic control device including a swing motor that drives an upper swing body.

[0002]

2. Description of the Related Art A hydraulic shovel is a typical example of a construction machine having an articulated work front. In recent years, as the field of use of the hydraulic shovel has expanded, the demand for a small-sized hydraulic shovel that can be easily operated even in a narrow work site has been increasing. FIG. 12 shows the appearance of this small-sized hydraulic excavator.

[0003] In Fig. 12, a hydraulic excavator includes a lower traveling structure 1, an upper revolving structure 2, and a work front 3, and the upper revolving structure 2 is mounted on the lower traveling structure 1 so as to be capable of turning. Is supported at the front part of the upper swing body 2 so as to be rotatable in the vertical direction.

A hydraulic control device mounted on a hydraulic excavator drives the front members of the lower traveling body 1, the upper revolving superstructure 2, and the work front 3, and the lower traveling body 1 includes a traveling motor 1a (one side). Only the upper revolving unit 2 is driven by a revolving motor 24 (see FIG. 13), and each front member of the work front 3 is driven by a boom cylinder 16, an arm cylinder 17, and a bucket cylinder 18.

[0005] By the way, in a hydraulic control device of a small-sized hydraulic excavator, a two-pump or three-pump system is mainly used. This two-pump or three-pump system separates and separates the hydraulic control device for work front / travel and the hydraulic control device for turning, and the hydraulic control device for work front / travel uses one or two hydraulic pumps. The hydraulic control device for turning comprises a hydraulic circuit provided with another hydraulic pump independent of the hydraulic circuit. FIG. 13 shows a circuit configuration of a hydraulic control device for turning in such a two-pump or three-pump system.

[0006] In FIG. 13, a fixed displacement hydraulic pump 120 is driven to rotate by a prime mover 119, and pressure oil discharged from the hydraulic pump 120 is supplied to a turning motor 124 via a direction control valve 123. The directional control valve 123 is a center bypass type through which a center bypass line 126 passes. The upstream side of the center bypass line 126 is connected to the discharge path 120a of the hydraulic pump 120, and the downstream side is connected to a tank. A relief valve 122 as a main safety valve is provided in a discharge passage 120a of the hydraulic pump 120.
Are provided, and actuator lines 127 and 128 between the direction control valve 123 and the swing motor 124 are provided with overload relief valves 125 and 125.

Further, a turning operation lever device 121 is provided as operating means of the turning motor 124. When the operator operates the operation lever of the turning operation lever device 121, the directional control valve 123 is switched in accordance with the operation direction and the operation amount, and the hydraulic oil from the hydraulic pump 120 passes through the directional control valve 123 through the turning motor. The rotating body 124 (see FIG. 12)
Is started.

In the hydraulic control apparatus for turning a small-sized hydraulic excavator as described above, the driving pressure of a turning motor 124 is controlled to improve turning operability in a small turning posture (see FIG. 14). There is a prior art.

[0009] In this prior art, the set pressure of the overload relief valve of the swing motor is changed according to the reach of the work front, so that a shock at the time of startup in a small swing posture is reduced. Trying to reduce.

[0010] In this prior art, the set pressure of the overload relief valve of the turning motor is changed in accordance with the lever operation amount of the turning operation lever device, so that the turning motor can be started smoothly. I have.

In this prior art, when both the angle of the arm and the boom have reached a predetermined angle, the directional control valve is operated to reduce the flow rate and to make a slow speed turn.

Further, there is the following prior art for changing a driving pressure of an actuator by operating a hydraulic element other than an overload relief valve. In this prior art, in a hydraulic control device using a closed center type directional control valve, a bleed-off valve is provided in a bypass pipe branched from a discharge pipe of a hydraulic pump,
It has a closed center type directional control valve that controls the discharge pressure of the hydraulic pump (drive pressure of the actuator) by changing the opening area (opening) of the bleed-off valve according to the operation signal for driving the directional control valve. The hydraulic circuit has the same bleed control characteristics as a center bypass type directional control valve to control the driving pressure.

[0013]

However, the above prior art has the following problems.

In the conventional hydraulic control device for turning a small hydraulic excavator shown in FIG. 13, the turning motor 124 is driven to rotate by the operator operating the operating lever of the turning operation lever device 121 as described above. The revolving superstructure 2 is started. At this time, since the revolving superstructure 2 has an inertial load, the driving pressure has a considerably high value at the beginning of normal movement. That is, for example, if the full lever operation is performed instantaneously, the hydraulic pump 120 immediately before the revolving unit 2 starts to rotate.
As shown in FIG. 15, the total pressure Q of the pressure oil discharged from the cylinder and having no place to go is relieved by the main relief valve 122. At this time, the driving pressure of the swing motor 124 is reduced as shown in FIG. As shown in FIG.
, And the driving torque of the swing motor 124 also becomes maximum (constant).

The work front 3 of the hydraulic shovel is articulated, and the reach of the work front 3 changes depending on the posture of the work front 3, and the inertial load of the swing body 2 changes. Therefore, when the driving torque of the turning motor 124 is maximized at the time of starting the turning,
The turning acceleration changes depending on the posture of the work front 3. That is, in the posture in which the work front 3 is extended as shown in FIG. 12, the inertial load of the revolving unit 2 is large.
As shown by the solid line in FIG.
Even if the driving torque of the motor 24 is maximized, the acceleration of the turning does not become so large. However, when the work front 3 is rolled in as shown in FIG. 14 and is in a so-called small turning posture, the inertial load is significantly reduced, and the acceleration is also extremely increased at the same time as shown by the dashed line in FIG.
In this case, the operator perceives this large acceleration as a shock feeling, that is, a deterioration in the operation feeling.

JP-A-6-173299 and JP-A-6-173299
In the prior art described in Japanese Patent Application Laid-Open No. 159314, the start-up in the small turning posture is performed by changing the set pressure of the overload relief valve of the turning motor according to the reach of the work front or the lever operation amount of the turning operation lever device. The turning drive pressure (turning drive torque) is reduced and the turning acceleration is reduced, thereby reducing the shock at the time of startup in the small turning posture.

However, it is necessary to use a variable relief valve to change the set pressure of the overload relief valve. The mechanism of the variable relief valve is extremely complicated and expensive, such as arranging a spool operated by a hydraulic signal at a setting portion on the spring side. Further, it is necessary to arrange two overload relief valves as shown in FIG. Therefore, using two such variable relief valves is disadvantageous in terms of cost. In addition, since the setting of the variable relief valve changes only after the spool is moved, a response delay occurs in the operation of changing the setting, which causes a problem in the reliability of the operation at the time of startup in the small turning posture.

In the prior art described in Japanese Patent Application Laid-Open No. Hei 6-330540, when both the angle of the arm and the boom reach a predetermined angle, the directional control valve is operated to reduce the flow rate, thereby performing the slow speed turning. However, even if the flow rate is reduced by the direction control valve, the drive pressure of the swing motor cannot be controlled, and the drive pressure of the swing motor at the time of starting the swing increases to the maximum pressure set by the main relief valve. For this reason, the problem of sudden acceleration in a small turning posture cannot be substantially solved. In addition, since the speed is switched at the timing of on / off, a feeling of strangeness occurs in the operability.

In the prior art described in Japanese Patent Application Laid-Open No. 7-63203, since the attitude of the work front is not monitored,
Shock at starting in small turning posture cannot be reduced.

An object of the present invention is to provide a hydraulic control device for a construction machine which does not generate a shock at the time of turning start regardless of a posture of a work front and which can realize the shock with a simple structure.

[0021]

(1) In order to achieve the above object, the present invention relates to an upper revolving structure that is rotatably mounted on a lower traveling structure, and that the upper revolving structure is rotatable vertically. Provided on a construction machine having an articulated work front supported by a prime mover, a fixed displacement hydraulic pump driven by the prime mover, and driven by pressure oil supplied from the hydraulic pump, In a hydraulic control device including a swing motor that drives an upper swing body and a directional control valve that controls the flow of pressure oil supplied from the hydraulic pump to the swing motor, the hydraulic pump and the directional control valve are connected. A bleed-off valve provided in the discharge path for bleeding the pressure oil supplied from the hydraulic pump to the tank, a posture detecting means for detecting the posture of the work front, and a detection value of the posture detecting means. The reach of the working front calculates Hazuki shall and a control means for changing an opening degree of the bleed-off valve in accordance with this reach. By providing the bleed-off valve and the posture detecting means as described above and changing the opening of the bleed-off valve by the control means, a part of the hydraulic oil discharged from the hydraulic pump in accordance with the reach of the work front is bleed-off. The valve is removed from the valve and controlled to reduce the discharge pressure of the hydraulic pump. For this reason, it is possible to set the swing drive pressure according to the reach of the work front at the time of starting the swing body, and it is possible to prevent a shock at the time of start regardless of the posture of the work front.

Since the bleed-off valve is merely a variable throttle, highly reliable control is possible with a simple structure.

(2) In the above (1), preferably,
The control means changes the opening of the bleed-off valve so that the opening of the bleed-off valve increases as the reach decreases.

Thus, the turning drive pressure is set to decrease as the reach of the work front decreases,
Shock at the time of starting small turning can be reduced.

(3) In the above (1), preferably, the apparatus further comprises a rotation speed detecting means for detecting a rotation speed of the prime mover, wherein the control means opens the bleed-off valve as the reach becomes smaller. To increase the degree,
Further, the opening degree of the bleed-off valve is changed so that the opening degree of the bleed-off valve decreases as the rotation speed decreases.

Thus, even when the rotation speed of the prime mover is set low, the swing drive pressure can be increased to the same pressure as when the rotation speed is rated, and the acceleration of the swing body can be maintained.

(4) In the above (1), preferably, the bleed-off valve is provided in a pipe branched from the discharge path, and operates between a fully closed position and a fully open position. It is.

Thus, the bleed-off valve can be arranged without providing a valve in the discharge path, and the discharge path can be simplified.
(5) Further, in the above (1), preferably, the bleed-off valve is provided on the discharge path, and communicates between the hydraulic pump and the tank with a first position for interrupting communication between the hydraulic pump and the tank. A switching valve that operates between the second position.

As a result, the bleed-off valve can be installed without using a branch pipe, and the circuit configuration can be simplified.

(6) Further, in the above (1), preferably, the bleed-off valve is of a hydraulic pilot drive type, and the control means is driven by a controller and a signal from the controller to apply a hydraulic pressure to the bleed-off valve. An electromagnetic proportional pressure reducing valve for outputting a signal.

Thus, the drive means for the bleed-off valve can be manufactured at low cost.

(7) In the above (1), preferably, the bleed-off valve is of an electromagnetic proportional type, and the control means has a controller for outputting a command signal to the bleed-off valve.

Thus, the driving means of the bleed-off valve can be simplified.

(8) Further, in the above (1), preferably, the posture detecting means has a plurality of angle sensors for detecting a predetermined joint angle of the work front.

As a result, a detection signal for calculating the reach of the work front can be output.

(9) In order to achieve the above object,
The present invention is provided for a construction machine having an upper revolving structure rotatably mounted on a lower traveling structure and an articulated work front rotatably supported on the upper revolving structure in a vertical direction. And first and second variable displacement hydraulic pumps and fixed displacement hydraulic pumps driven by the prime mover, and driven by pressure oil supplied from the first and second variable displacement hydraulic pumps And a plurality of actuators for driving the undercarriage and the work front, and a plurality of directional control valves for controlling the flow of pressure oil supplied from the first and second variable displacement hydraulic pumps to the plurality of actuators. A swing motor driven by the pressure oil supplied from the fixed displacement hydraulic pump to drive the upper swing body, and a flow of the pressure oil supplied to the swing motor from the hydraulic pump. A bleed-off valve provided in a discharge path communicating the hydraulic pump and the directional control valve, and bleeding pressure oil supplied from the hydraulic pump to a tank; Attitude detection means for detecting the attitude of the work front, and control means for calculating the reach of the work front based on the detected value of the attitude detection means, and changing the opening of the bleed-off valve according to the reach. Shall be provided.

Thus, as described in the above (1), it is possible to prevent a shock at the time of starting the revolving structure regardless of the posture of the work front, and it is possible to perform highly reliable control with a simple structure. .

Further, since the lower traveling body and the actuator of the work front are driven by the first and second variable displacement hydraulic pumps, the opening of the bleed-off valve changes, and the discharge pressure of the fixed displacement hydraulic pump changes. The lower traveling structure and the work front actuator can be driven without being affected by the decrease in the discharge pressure even if the
Excellent combined operability with the work front can be secured.

(10) In the above (9), preferably, the plurality of actuators include a boom cylinder and an arm cylinder.

Thus, as a combined operation of the turning and the work front described in the above (9), it is possible to secure excellent combined operability of raising the turning boom and turning arm cloud.

[0041]

Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows an overall view of a hydraulic shovel having an articulated work front and a circuit configuration of a hydraulic control device for turning.

In FIG. 1, a hydraulic excavator A includes a lower traveling structure 1, an upper revolving structure 2, and a work front 3, and the lower traveling structure 1 includes a discharging blade 5 at a front portion and an upper revolving structure 2 Is mounted on the lower traveling body 1 so as to be pivotable, and the work front 3 is supported at the front of the upper revolving body 2 so as to be pivotable in the vertical direction.

The hydraulic excavator A has a hydraulic control for driving the lower traveling unit 1, the upper revolving unit 2, the front members (boom 10, arm 11, bucket 12) of the work front 3, and the discharging blade 5. The hydraulic control device includes a traveling motor 1a (only one side is shown) for driving the lower traveling body 1, a turning motor 24 for driving the upper revolving body 2, and a front member of the work front 3. Boom cylinder 16 to be moved up and down, and arm cylinder 1
7, a bucket cylinder 18, and a discharging blade cylinder (not shown) for moving the discharging blade 5 up and down.

As shown in FIG. 2, the hydraulic control device includes a variable displacement hydraulic pump 101a, 101b, a fixed displacement hydraulic pump 20, a pilot pump 33, and these pumps 101a, 101b, 20, 23. An engine 19 that is driven to rotate, a valve device 104 connected to the hydraulic pumps 101a and 101b, and a valve device 105 connected to the hydraulic pump 20 are provided.

The valve device 104 includes direction control valves 106 to 109
Directional control valves 110 to 113, and the directional control valves 106 to 108 are connected to a center bypass line 115 connected to a discharge path 114a of the hydraulic pump 101a.
a, and the direction control valves 110 to 113 are located on a center bypass line 115b connected to a discharge path 114b of the hydraulic pump 101b. Direction control valve 106-1
08 is for the traveling right, for the bucket, for the first boom, respectively.
For the second arm, the direction control valves 110 to 113 are the first
The flow rate of the pressure oil supplied to the boom cylinder 16 is controlled by the directional control valves 108 and 111 for the arm, the second boom, the spare, and the traveling left, and the first and second booms. The flow rate of the pressure oil supplied to the arm cylinder 17 is controlled by the directional control valves 110 and 109 for the two arms, and the flow rate of the pressure oil supplied to the bucket cylinder 18 is controlled by the directional control valve 107 for the bucket. The right and left direction control valves 106 and 113 control the flow rate of the pressure oil supplied to the right and left traveling motors 1a (only one side is shown).

The valve device 105 is provided with a direction control valve 23,1.
17, and these directional control valves are located on a center bypass line 26 connected to the discharge passage 20 a of the hydraulic pump 20. The directional control valve 23 is for turning, and the directional control valve 117 is used.
Is for the earth discharging blade, the flow rate of the pressure oil supplied to the turning motor 24 is controlled by the turning direction control valve 23, and the earth discharging blade cylinder (not shown) is controlled by the direction controlling valve 117 for the earth discharging blade. Is controlled.

A pilot relief valve 34 for maintaining the discharge pressure of the pilot pump 33 at a constant pressure is connected to the discharge path 33a of the pilot pump 33.

The turning hydraulic control apparatus shown in FIG. 1 is a hydraulic circuit connected to the fixed displacement hydraulic pump 20 shown in FIG. It is.

The hydraulic control device for turning is as described above.
A fixed displacement hydraulic pump 20 and a swing motor 24 driven to rotate by hydraulic oil discharged from the hydraulic pump 20
A center bypass line 26 leading to a discharge passage 20a extending from the hydraulic pump 20, and a directional control valve 23 for turning.
And The direction control valve 23 is a center bypass type valve through which a center bypass line 26 passes, and the downstream side of the center bypass line 26 is connected to a tank. Further, a turning operation lever device 21 for driving and operating the direction control valve 23 is provided.

Pipe lines 20b and 20c are branched from the discharge path 20a of the hydraulic pump 20, and a relief valve 22 as a main safety valve is provided in the pipe line 20b.
B is provided with a bleed-off valve 35 which is a variable throttle valve of a hydraulic drive system that variably operates. Direction control valve 2
3 and the swing motor 24 are connected to an actuator line 27,
And the actuator lines 27 and 28 have overload relief valves 25 and 25
Is provided.

The work front 3 further includes an upper revolving unit 2
A boom angle sensor 13 for detecting an angle θ1 of the boom 10 with respect to the boom 10, and an angle θ2 of the arm 11 with respect to the boom 10
Arm angle sensor 14 for detecting the angles θ1, θ
2 is provided with a controller 31 which inputs the detection signal of No. 2 and performs an arithmetic processing thereof, and an electromagnetic proportional pressure reducing valve 32 which is operated by a command signal outputted from the controller 31.

The electromagnetic proportional pressure reducing valve 32 is connected to the pilot pump 3
3. Based on the pilot pressure generated by the pilot relief valve 34, a pressure corresponding to the current value of the command signal is output as the pilot pressure. This pilot pressure is applied to the swivel drive 3 of the bleed-off valve 35 via a pilot line 36.
7 to switch the bleed-off valve 35.

An outline of the processing functions of the controller 31 is shown in a functional block diagram in FIG. In FIG. 3, the controller 31 has the respective processing functions of a reach calculator 31a, a bleed-off valve target opening calculator 31b, and a command signal calculator 31c.

The reach calculating section 31a calculates the angles θ1, θ2 detected by the boom angle sensor 13 and the arm angle sensor 14.
And the front reach r of the work front 3 is calculated based on the dimensions of the work front 3 stored in advance.

Bleed-off valve target opening calculating section 31b
Calculates the target opening of the bleed-off valve 35 based on the front reach r calculated by the reach calculating unit 31a and the functional relationship shown in FIG. The functional relationship shown in FIG. 4 is stored in the memory as a table used in the target opening calculating section 31b, and the functional relationship is set so that the target opening Ao increases as the front reach r decreases. I have.

The command signal calculator 31c calculates the target opening Ao of the bleed-off valve calculated by the target opening calculator 31b.
Is converted into a command signal for the electromagnetic proportional pressure reducing valve 32, and the current value corresponding to the command signal is
2a.

The operation of this embodiment configured as described above will be described.

First, the principle of operation of the present invention will be described. FIG.
1 schematically shows the hydraulic circuit according to the present embodiment shown in FIG. In the figure, the same reference numerals are given to members equivalent to the members shown in FIG.

In FIG. 5, a momentary stop state of the swing motor 24 when the upper swing body is started will be considered. At this time, the opening degree (opening area) of the bleed-off valve 35 is f, the discharge pressure of the hydraulic pump 20 when the relief valve 22 is assumed to be Pt, the discharge flow rate of the hydraulic pump 20 is Q, Assuming that the flow coefficient of the throttle is c, since the entire amount of Q passes through the bleed-off valve 35, the relational expression of Q = fc ・ (Pt) (1) holds. Here, since the hydraulic pump 20 is of a fixed displacement type, Q is constant as long as the rotation speed of the prime mover 19 is constant. Therefore, when the equation (1) is modified, Pt = Q ² / (fc) ² ... (2) Here, as shown in FIG. 5, the discharge pressure of the hydraulic pump 20 in the actual hydraulic circuit having the relief valve 22 is P
d, assuming that the set pressure of the relief valve 22 is Pr, if Pt ≧ Pr, Pd = Pr (3) If Pt <Pr, Pd = Pt (4) That is, if Pt is less than Pr, Pd becomes Pt,
The discharge pressure of the hydraulic pump 20 can be arbitrarily set depending on the opening degree (opening area) of the bleed-off valve 35.

Therefore, if the opening is set as a function f (r) of the reach r of the work front, the equation (2) becomes: Pt = Q ² / (f (r) · c) ² (5) As long as is constant,
Accordingly, it is possible to set the discharge pressure Pd of the hydraulic pump 20, that is, the swing driving pressure at the time of starting the upper swing body.

The hydraulic control device according to the present embodiment operates based on the above principle, and FIGS. 6 (a) and 6 (b)
The change in the drive pressure (swing drive pressure) of the swing motor 24 and the change in the swing speed when the upper swing body 2 is activated at that time are shown. In the figure, a solid line indicates a change in a posture in which the work front 3 is extended, and a dashed line indicates a change in a posture in which the work front 3 is involved.

As shown by the solid line in FIG. 6A, in the posture in which the work front 3 is extended (the maximum reach r), the opening of the bleed-off valve 35 is minimized. Turns to the set relief pressure Pr of the relief valve 22.

Further, since the inertia load of the upper swing body 2 is large in the posture where the work front 3 is extended, even if the swing drive pressure (swing drive torque) is maximized, the swing speed is increased as shown in FIG. Does not immediately increase to the target speed (command speed of the turning operation lever device 21), and the turning acceleration does not increase.

On the other hand, in the posture in which the work front 3 is involved (the reach r is minimum), the opening of the bleed-off valve 35 is maximized. Therefore, as shown by the chain line in FIG. Does not rise up to the set relief pressure Pr of the relief valve 22, but becomes the pressure set by the bleed-off valve 35.

Therefore, in the posture in which the work front 3 is involved, as in the posture in which the work front 3 is extended, as shown in FIG.
As shown in (b), the turning speed does not immediately increase to the target speed (the command speed of the turning operation lever device 21), and the acceleration at the time of starting the turning does not increase.

As described above, according to the present embodiment, it is possible to set the swing drive pressure according to the reach of the work front when the upper swing body is started, and to prevent shock at the start regardless of the posture of the work front. be able to. Further, since the bleed-off valve is merely a variable throttle, highly reliable control is possible with a simple structure.

The hydraulic control device for the swing motor 24 is as follows:
The hydraulic controller for the actuators (travel motor 1a, boom cylinder 16, arm cylinder 17, etc.) related to the undercarriage 1 and the work front 3 is configured in a separate circuit from the hydraulic control device. Since the pump is driven by the pressure oil from the pumps 101a and 101b, even if the discharge pressure of the hydraulic pump 20 decreases due to the change in the opening of the bleed-off valve as described above, the actuators of the lower traveling unit 1 and the work front 3 do not operate. Driving can be performed without being affected by a decrease in the discharge pressure, and excellent combined operability between turning and the lower traveling body / working front, such as turning the boom and turning arm cloud, can be secured.

Next, a second embodiment of the present invention will be described with reference to FIGS. In the drawing, members that are the same as the members illustrated in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted. In this embodiment,
The degree of opening of the bleed-off valve is also changed depending on the number of revolutions of the prime mover that drives the hydraulic pump.

In FIG. 7, a motor 19 for rotating the hydraulic pump 20 is provided with a rotation speed sensor 15 for detecting the rotation speed (hereinafter referred to as rotation speed) N of the motor 19.
In addition to the detection signals of the angles θ1 and θ2 by the boom angle sensor 13 and the arm angle sensor 14 provided on the work front 3, the controller 31A
The detection signal of the number of rotations N by 5 is also input.

As shown in FIG. 8, the controller 31A includes an engine speed N detected by the speed sensor 15 in addition to a reach calculator 31a, a target opening calculator 31Bb for the bleed-off valve, and a command calculator 31c. Flow rate calculator 31 that calculates the discharge flow rate Q of the hydraulic pump 20 based on
d, the bleed-off valve target opening degree calculating section 31Bb bleeds the front reach r calculated by the reach calculating section 31a and the rotational speed N calculated by the pump flow rate calculating section 31d. The opening degree of the off valve 35 is calculated.

The pump flow rate calculator 31d calculates the discharge flow rate of the hydraulic pump 20 by multiplying the number of revolutions N by the capacity (displacement volume) of the hydraulic pump 20 and a predetermined coefficient.
The target opening calculating section 31Bb of the bleed-off valve calculates the target opening Ao based on the front reach r, the rotation speed N, and the functional relationship shown in FIG. The functional relationship shown in FIG. 9 is stored in the memory as a table used in the target opening calculating unit 31Bb of the bleed-off valve. The functional relationship is such that as the front reach r decreases, the target opening A
The target opening Ao is set to decrease as the rotation speed N decreases as o increases.

The operation of the present embodiment configured as described above will be described.

When the rotation speed N of the prime mover is rated (at the rotation speed Nr), the operation is performed in the same manner as in the first embodiment.

When the rotation speed N of the prime mover is set lower than Nr, the discharge flow rate of the hydraulic pump 20 decreases. At this time, in the first embodiment, the target opening Ao does not change even if the rotation speed N changes, so that the discharge pressure of the hydraulic pump 20 decreases and the front acceleration decreases.

In the present embodiment, the target opening Ao is determined by the rotation speed N
Is controlled so that it becomes smaller as
Even if the rotation speed N decreases and the discharge flow rate of the hydraulic pump 20 decreases, the discharge pressure of the hydraulic pump 20 can be controlled to the same pressure as when the rotation speed N is at Nr, and the acceleration of the revolving structure can be maintained.

Therefore, according to the present embodiment, it is possible to set the swing drive pressure according to the reach of the work front at the time of starting the revolving structure regardless of the change in the rotational speed N, and to start the work regardless of the posture of the work front. Shock at the time can be prevented.

A third embodiment of the present invention will be described with reference to FIG. In the drawing, members that are the same as the members illustrated in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted. This embodiment is different from the first embodiment in that the mounting position of the bleed-off valve is changed.

That is, in FIG. 10, the bleed-off valve 3
5A is directly mounted on the discharge path 20a of the hydraulic pump 20.

The present embodiment thus configured operates almost in the same manner as the first embodiment, and the same effects as in the first embodiment can be obtained. Further, in the present embodiment, the bleed-off valve can be installed without using a branch pipe, so that the circuit configuration can be simplified.

A fourth embodiment of the present invention will be described with reference to FIG. In the drawing, members that are the same as the members illustrated in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted. This embodiment is a modification of the first embodiment in which the operation method of the bleed-off valve is changed.

That is, in FIG. 11, the bleed-off valve 3
The bleed-off valve 35B is an electromagnetic proportional type.
A command signal is directly transmitted from the controller 31 to the turning drive unit 37b.

The present embodiment thus configured operates almost in the same manner as the first embodiment, and provides the same effects as the first embodiment. Further, in the present embodiment, the driving means of the bleed-off valve can be simplified.

As described above, some embodiments of the present invention have been described with reference to the drawings. However, the present invention is not limited to these embodiments, and various changes and additions may be made without departing from the gist of the present invention. You may.

For example, in the present invention, it is important that a functional relationship f (r) is established between the reach r and the opening of the bleed-off valve. Is assumed to be supplied to For this reason, in the above-described embodiment, the hydraulic circuit of the hydraulic control device for turning is provided with the hydraulic cylinder for the earth discharging blade that is less likely to be driven simultaneously with the turning motor 24 as an actuator other than the turning motor. An actuator other than the hydraulic cylinder for the discharging blade may be provided as long as the actuator is less likely to be driven simultaneously with the motor 24.

In the above embodiment, the angle sensor is used as the posture detecting means for detecting the posture of the work front. However, a stroke sensor for detecting each stroke of the boom cylinder and the arm cylinder may be used.

Further, the bleed-off valve according to the second embodiment shown in FIG. 7 may be arranged on the discharge path of the hydraulic pump as shown in FIG. 10, or the bleed-off valve according to the second embodiment shown in FIG. The operation method of the off valve may be of the electromagnetic proportional type as shown in FIG. 11, or the operation method of the bleed off valve of the third embodiment shown in FIG. 10 may be of the electromagnetic proportional type as shown in FIG. You may.

[0089]

According to the present invention, a shock is prevented from being generated at the time of turning start regardless of the posture of the work front,
And it can be realized with a simple structure.

Even if the discharge pressure of the fixed displacement hydraulic pump decreases due to a change in the opening of the bleed-off valve, the lower traveling body and the actuator at the work front are driven without being affected by the decrease in the discharge pressure. This makes it possible to ensure excellent combined operability between turning and the lower traveling body / work front.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall view of a hydraulic excavator having an articulated work front according to a first embodiment of the present invention and a circuit configuration of a hydraulic control device for turning.

FIG. 2 is a circuit diagram showing the concept of the entire hydraulic control device of the hydraulic shovel shown in FIG.

FIG. 3 is a functional block diagram showing processing contents of a control device for a hydraulic shovel having an articulated work front according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a functional relationship stored in a table used in an opening calculator of a bleed-off valve of a hydraulic shovel having an articulated work front according to the first embodiment of the present invention.

FIG. 5 is a diagram schematically illustrating a state of a hydraulic circuit when a driving torque of a swing motor of a hydraulic shovel having an articulated work front according to the first embodiment of the present invention is maximum (constant).

FIG. 6A is a diagram illustrating a change in a driving pressure (swing driving pressure) of a swing motor when a swing of a swing body of a hydraulic shovel having an articulated work front according to the first embodiment of the present invention is started. (B) is a diagram showing a change in the turning speed in the same manner.

FIG. 7 is a diagram showing an overall view of a hydraulic shovel having an articulated work front and a circuit configuration of a hydraulic control device for turning according to a second embodiment of the present invention.

FIG. 8 is a functional block diagram showing processing contents of a control device for a hydraulic shovel having an articulated work front according to a second embodiment of the present invention.

FIG. 9 is a diagram showing a functional relationship stored in a table used in an opening calculator of a bleed-off valve of a hydraulic shovel having an articulated work front according to a second embodiment of the present invention.

FIG. 10 is a diagram showing an overall view of a hydraulic shovel having an articulated work front according to a third embodiment of the present invention and a circuit configuration of a hydraulic control device for turning.

FIG. 11 is a diagram showing an overall view of a hydraulic shovel having an articulated work front and a circuit configuration of a hydraulic control device for turning according to a fourth embodiment of the present invention.

FIG. 12 is an overall view showing a posture in which a work front of a conventional hydraulic excavator having an articulated work front is extended.

FIG. 13 is a diagram showing a circuit configuration of a conventional hydraulic control device for turning a hydraulic shovel having an articulated work front.

FIG. 14 is an overall view showing a small turning posture of a conventional hydraulic excavator having a multi-joint type work front.

FIG. 15 is a diagram schematically illustrating a state of a hydraulic circuit when a driving torque of a swing motor of a conventional hydraulic shovel having an articulated work front is maximum (constant).

FIG. 16 (a) is a diagram illustrating a change in a driving pressure (swing driving pressure) of a swing motor when a swing body of a conventional hydraulic excavator having a multi-joint type work front starts swinging;
(B) is a figure which shows the change of the turning speed similarly.

[Explanation of symbols]

A Small hydraulic excavator 1 Lower traveling body 1a Traveling motor 2 Upper turning body 3 Work front 10 Boom 11 Arm 12 Bucket 13 Boom angle sensor 14 Arm angle sensor 15 Engine speed sensor 16 Boom cylinder 17 Arm cylinder 18 Bucket cylinder 19 Prime mover 20 Fixed displacement hydraulic pump 20a Discharge path 20b, 20c Pipe line 21 Swing operation lever device 22 Relief valve 23 Direction control valve 24 Swing motor 25 Overload relief valve 26 Center bypass line 27, 28 Actuator line 31, 31A Controller 31a Reach calculation Units 31b, 31Bb Target opening calculating unit for bleed-off valve 31c Command signal calculating unit 31d Pump flow calculating unit 32 Electromagnetic proportional pressure reducing valve 33 Pilot pump 34 Pilot relief valve 35, 35A, 35B Bleed-off valve 36 Pilot line 37, 37a, 37b Swing drive unit 101a, 101b Variable displacement hydraulic pump 106-113 Flow control valve for lower traveling body and work front

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiaki Nishida 650, Kandamachi, Tsuchiura-shi, Ibaraki Pref.

Claims (10)

[Claims] 1. A construction machine having an upper revolving body rotatably mounted on a lower traveling body and an articulated work front rotatably supported on the upper revolving body in a vertical direction, A prime mover, a fixed displacement hydraulic pump driven by the prime mover, a slewing motor driven by the pressure oil supplied from the hydraulic pump to drive the upper revolving unit, and a slewing motor supplied from the hydraulic pump to the slewing motor. A hydraulic control device provided with a directional control valve for controlling the flow of hydraulic oil, which is provided in a discharge path connecting the hydraulic pump and the directional control valve, and bleeds hydraulic oil supplied from the hydraulic pump to a tank. A bleed-off valve, a posture detecting means for detecting a posture of the work front, and a reach of the work front is calculated based on a detection value of the posture detecting means, and the reach is calculated according to the reach. Hydraulic control system for a construction machine characterized in that it comprises a control means for changing an opening degree of the bleed-off valve. 2. The hydraulic control apparatus for a construction machine according to claim 1, wherein said control means changes the opening of said bleed-off valve so that the opening of said bleed-off valve increases as said reach decreases. A hydraulic control device for a construction machine. 3. The construction machine hydraulic control device according to claim 1, further comprising a rotation speed detecting means for detecting a rotation speed of said prime mover, wherein said control means controls said bleed-off valve as said reach decreases. A hydraulic control device for a construction machine, wherein the opening degree of the bleed-off valve is changed so that the opening degree increases and the opening degree of the bleed-off valve decreases as the rotation speed decreases. 4. The hydraulic control device for a construction machine according to claim 1, wherein the bleed-off valve is provided in a pipe branched from the discharge path, and operates between a fully closed position and a fully opened position. A hydraulic control device for a construction machine, being a valve. 5. The hydraulic control device for a construction machine according to claim 1, wherein the bleed-off valve is provided on the discharge passage, and a first position for interrupting communication between the hydraulic pump and the tank, the hydraulic pump and the tank. A hydraulic control device for a construction machine, wherein the control valve is a switching valve that operates between a second position communicating with the second position. 6. A hydraulic control apparatus for a construction machine according to claim 1, wherein said bleed-off valve is of a hydraulic pilot drive type, and said control means is driven by a controller and a signal from said controller to control said bleed-off valve. A hydraulic control device for a construction machine, comprising: an electromagnetic proportional pressure reducing valve that outputs a hydraulic signal. 7. A hydraulic control system for a construction machine according to claim 1, wherein said bleed-off valve is of an electromagnetic proportional type, and said control means has a controller for outputting a command signal to said bleed-off valve. Hydraulic equipment for construction machinery. 8. A hydraulic control system for a construction machine according to claim 1, wherein said posture detecting means has a plurality of angle sensors for detecting a predetermined joint angle of said work front. apparatus. 9. A construction machine having an upper revolving structure rotatably mounted on a lower traveling structure and an articulated work front rotatably supported on the upper revolving structure in a vertical direction, A prime mover, first and second variable displacement hydraulic pumps and fixed displacement hydraulic pumps driven by the prime mover, and pressure oil supplied from the first and second variable displacement hydraulic pumps. A plurality of driven actuators for driving the undercarriage and the work front, and a plurality of direction controls for controlling the flow of pressure oil supplied to the plurality of actuators from the first and second variable displacement hydraulic pumps A valve, a swing motor driven by the pressure oil supplied from the fixed displacement hydraulic pump, and driving the upper revolving unit, and a pressure oil supplied to the swing motor from the hydraulic pump. A bleed-off valve provided in a discharge path communicating the hydraulic pump and the directional control valve, and bleeding pressure oil supplied from the hydraulic pump to a tank. A posture detecting means for detecting the posture of the work front, a control means for calculating a reach of the work front based on a detection value of the posture detection means, and changing an opening of the bleed-off valve according to the reach; A hydraulic control device for a construction machine, comprising: 10. The hydraulic control device for a construction machine according to claim 9, wherein said plurality of actuators include a boom cylinder and an arm cylinder.