JP5320003B2 - Hydraulic control device for work machine - Google Patents

Description

  The present invention relates to a hydraulic control device for a work machine having an articulated front work machine in which a hydraulic cylinder and a plurality of joint members are pivotally attached to each other.

Conventionally, work machines represented by hydraulic excavators have been developed that include an articulated front work machine including a two-piece boom and a three-piece boom. For example, Patent Document 1 discloses a two-piece boom including an articulated front working machine in which a first boom and a second boom are jointed to an upper swing body, and an arm and a bucket are jointed at the tip. The working machine is described. Since a hydraulic excavator equipped with such an articulated front work machine has a wider working range than a normal hydraulic excavator, it is possible to dismantle objects (walls, buildings, etc.) above the hydraulic excavator. It is suitable for use when both the operations of disassembling and excavating a lower object (pile, foundation, etc.) are necessary.
JP 2000-240105 A

  By the way, the multi-joint type front working machine has a long distance from the base end portion to the tip end portion, and therefore, the moment acting on the pivoting portion with respect to the hydraulic excavator body and the hydraulic cylinder supporting each joint member tends to increase. In particular, such a tendency becomes prominent when a heavy object such as a breaker for disassembly or a twin header is attached as an attachment. Therefore, for example, if the boom lowering operation is performed when the building is dismantled with the articulated front work apparatus lifted upward, the lowering speed of the boom is likely to increase due to the load of its own weight, and good operability is obtained. There is a problem that it is not possible.

  For such a problem, it is conceivable to limit the operating speed of the boom by suppressing the hydraulic oil flow rate in the boom lowering direction. That is, by narrowing the hydraulic fluid passage on the side from which hydraulic fluid is discharged when the boom is lowered, the flow velocity of the hydraulic fluid is suppressed and acceleration of the lowering speed of the boom is prevented. However, if the hydraulic oil flow path is narrowed, the lowering speed of the boom at the time of dismantling or excavation of the lower object is also lowered, and this also fails to obtain good workability.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a hydraulic control device for a work machine that can acquire good operability and workability regardless of the working posture. To do.

In order to achieve the above object, a hydraulic control device for a work machine according to claim 1 of the present invention has a disassembly mode for disassembling an upper object and an excavation mode for disassembling a lower object. A hydraulic control device for a work machine that drives a two-piece boom composed of an upper boom and a lower boom by expansion and contraction of the upper boom cylinder and the lower boom cylinder, the work mode changeover switch for switching between the dismantling mode and the excavation mode, and the upper A first electromagnetic proportional pressure reducing valve interposed in a pilot circuit (upper extension pilot circuit) for driving the boom cylinder in the extension direction, and a pilot circuit (upper contraction pilot circuit) for driving the upper boom cylinder in the reduction direction. And a pilot circuit (lower) for driving the lower boom cylinder in the extending direction. When the dismantling mode is selected by the third electromagnetic proportional pressure reducing valve interposed in the pilot circuit), the height detecting means for detecting the tip height (H) of the upper boom, and the work mode selector switch. In addition, the dismantling mode control means for reducing the opening degree of the first electromagnetic proportional pressure reducing valve, the excavation mode is selected by the work mode changeover switch, and the tip height detected by the height detecting means ( When H) is equal to or higher than a preset first height (h ₁ ), the opening degrees of the second electromagnetic proportional pressure reducing valve and the third electromagnetic proportional pressure reducing valve are set according to the tip height (H). It is characterized by comprising control means for excavation mode to narrow down.

In addition to the configuration of claim 1, the hydraulic control device for a work machine of the present invention according to claim 2 is characterized in that the excavation mode control means selects the excavation mode with the work mode changeover switch, and When the tip height (H) detected by the height detection means is equal to or higher than the second height (h ₂ ) higher than the first height (h ₁ ), the second electromagnetic proportional pressure reducing valve And the third electromagnetic proportional pressure reducing valve is closed.

A hydraulic control device for a work machine according to a third aspect of the present invention, in addition to the configuration according to the first or second aspect, includes a first angle sensor for detecting the elevation angle of the upper boom, And a second angle sensor for detecting an elevation angle of the lower boom.
Further, work machine hydraulic control device of the present invention described in claim 4, in addition to the configuration according to any one of claims 1 to 3,該解body mode control means, said in the working mode switch When the dismantling mode is selected and the tip height (H) detected by the height detection means is less than a preset third height (h ₃ ), the tip height (H) is It is characterized in that the opening degree of the first electromagnetic proportional pressure reducing valve is further reduced than when it is equal to or greater than the third height (h ₃ ).

The hydraulic control device for a work machine according to a fifth aspect of the present invention further includes load detection means for detecting a load acting on the upper boom cylinder and the lower boom cylinder in addition to the configuration of the fourth aspect. The third height is changed according to the magnitude of the load detected by the load detection means.
According to a sixth aspect of the present invention, there is provided a hydraulic control device for a work machine according to the present invention, in addition to the configuration according to the fifth aspect, the first electromagnetic proportional pressure reduction according to the magnitude of the load detected by the load detecting means. It is characterized by changing the throttle opening of the valve.

According to the hydraulic control device for a work machine of the present invention (Claim 1), it is possible to prevent the upper boom from falling by suppressing the extension of the upper boom cylinder in the disassembly mode. On the other hand, since the extension of the upper boom cylinder is not suppressed in the excavation mode, the operability can be improved.
Further, when the tip height of the upper boom becomes high in the excavation mode, the shortening of the upper boom cylinder and the extension of the lower boom cylinder can be suppressed, and the front work machine can be prevented from rising. Thereby, the operator can be informed of the operating range of the front work machine in the excavation mode. Moreover, since the rise of the upper boom is suppressed, the fall can be reliably prevented.

Further, according to the hydraulic control device for a work machine of the present invention (Claim 2), the operation of the front work machine can be limited so that the height of the tip of the upper boom does not exceed the second height. Further, the movable range of the front work machine in the excavation mode can be divided in the height direction.
Further, according to the hydraulic control device for a work machine of the present invention (Claim 3), the tip height of the upper boom can be accurately grasped with a simple configuration.

Further, according to the hydraulic control device for a working machine of the present invention (Claim 4), in the dismantling mode, the amount of suppression of the extension of the upper boom cylinder increases as the tip height of the upper boom decreases. It can be surely prevented.
Further, according to the hydraulic control device for a work machine of the present invention (Claim 5), the height at which the amount of suppression of the extension of the upper boom cylinder starts to increase is changed according to the magnitude of the load, thereby ensuring more certainty. It is possible to prevent the upper boom from falling. For example, when a heavy attachment is worn, the amount of suppression can be increased from a relatively higher position than when a small attachment is worn.

  Further, according to the hydraulic control device for a working machine of the present invention (Claim 6), the operability can be further improved by the throttle control according to the load. For example, when a heavy attachment is attached, the front work machine can be made harder to fall by making the first electromagnetic proportional pressure reducing valve throttle smaller than when a light attachment is attached. Further, it is possible to make the operation speed of the front work machine constant regardless of the weight of the attachment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 6 are views for explaining a hydraulic control device for a working machine according to an embodiment of the present invention, and FIG. 1 is a side view showing an overall configuration of a dismantling work machine equipped with the hydraulic control device. FIG. 2 is a side view showing the posture of the demolition work machine in the excavation mode, FIG. 3 is a hydraulic circuit diagram and a control block diagram showing the overall configuration of the hydraulic control device, FIG. 4 is a control block diagram showing the functions of the controller according to the hydraulic control apparatus, FIG. 5 is a graph showing the setting of the upper limit values of the lower boom extension side pilot pressure and the upper boom contraction side pilot pressure in the hydraulic control apparatus, and FIG. It is a graph which shows the opening characteristic of the control valve in a hydraulic control circuit.
FIG. 7 is a graph showing the setting of the upper limit value of the upper boom extension side pilot pressure in the hydraulic control apparatus as a modification of the present invention.

[1. overall structure]
The hydraulic control apparatus according to the present invention is applied to a dismantling work machine 30 shown in FIG. The demolition work machine 30 includes a lower traveling body 31 equipped with a crawler traveling device, and an upper revolving body 32 that is rotatably mounted on the lower traveling body 31. A front work machine 33 having a two-piece boom and a cab 38 on which an operator rides are mounted on the front side of the upper swing body 32.

The front work machine 33 includes a lower boom 34, an upper boom 35, an arm 36, and a crusher 37 as an attachment. The lower boom 34 is pivotably attached to the frame 39 of the upper swing body 32, and the upper boom 35 is pivotally attached to the tip of the lower boom 34.
A hydraulically driven lower boom cylinder 8 that swings the lower boom 34 in the vertical direction is interposed between the frame 39 and the lower boom 34, and the upper boom 35 is moved up and down between the lower boom 34 and the upper boom 35. An upper boom cylinder 7 that swings in the direction is interposed. The hydraulic control apparatus controls the expansion and contraction operations of the lower boom cylinder 8 and the upper boom cylinder 7. Further, two lower boom cylinders 8 are provided, and the hydraulic control relating to them is the same.

  The dismantling machine 30 is provided with two dismantling modes and excavation modes. The dismantling mode is a mode for disassembling an object above the dismantling work machine 30, and is mainly selected when working in a posture in which the front work machine 33 is extended upward as shown in FIG. Is. On the other hand, the excavation mode is a mode for disassembling or excavating an object below the dismantling work machine 30, and mainly works in a posture in which the front work machine 33 is extended downward as shown in FIG. This mode is selected at the time. A work mode changeover switch 1 for selectively switching these work modes is provided in the cab 38. Information on the work mode selected by the work mode change-over switch 1 is input to the controller 20 described later.

  An upper boom angle sensor 2a (first angle sensor) for detecting an elevation angle of the upper boom 35 is provided at a pivotally attached portion between the upper boom 35 and the lower boom 34. A lower boom angle sensor 2b (second angle sensor) for detecting the elevation angle is provided. The angles detected by these angle sensors 2a and 2b are input to the controller 20 described later and used for calculating the height H of the tip T of the upper boom 35. In the present embodiment, these angle sensors 2 a and 2 b function as height detection means for detecting the tip height H of the upper boom 35.

[2. Circuit configuration]
FIG. 3 schematically shows a hydraulic circuit for driving the upper boom cylinder 7 and the lower boom cylinder 8. In addition, description is abbreviate | omitted regarding the hydraulic circuit which concerns on another actuator.
The hydraulic pump 11 driven by the engine 13 is a variable displacement pump provided with a regulator 12 and supplies hydraulic oil to both the upper boom cylinder 7 and the lower boom cylinder 8. The regulator 12 is a well-known pump displacement variable means, and the hydraulic pump 11 is configured to decrease the discharge flow rate of the hydraulic pump 11 as the introduced negative control pressure increases and to increase the discharge flow rate as the negative control pressure decreases. The swash plate control is implemented.

  Control valves 6a and 6b are interposed on the hydraulic circuits between the hydraulic pump 11 and the upper boom cylinder 7 and the lower boom cylinder 8, respectively. These control valves 6a and 6b are valves for adjusting the flow rate and flow direction of the hydraulic oil to the upper boom cylinder 7 and the lower boom cylinder 8, and the flow control spool (stem) position is set to three positions S1 to S3 by pilot control. It is configured as a pilot electromagnetic flow control valve that can be switched to variably control the flow rate and flow direction of hydraulic oil.

  For example, when the spool of the control valve 6a for the upper boom cylinder 7 is switched to the S1 position, the hydraulic oil discharged from the hydraulic pump 11 is supplied to the head chamber side of the upper boom cylinder 7 and the upper boom cylinder 7 extends. To do. On the other hand, when the spool is switched to the S3 position, the hydraulic oil is supplied to the rod chamber side of the upper boom cylinder 7 and the upper boom cylinder 7 is shortened. When the spool of the control valve 6b for the lower boom cylinder 8 is switched to the S3 position, hydraulic oil is supplied to the head chamber side of the lower boom cylinder 8 and the lower boom cylinder 8 extends.

  Hereinafter, in the control valve 6a on the upper boom cylinder 7 side, a circuit for introducing the pilot pressure in the direction of switching the spool from the neutral S2 position to the S1 position is referred to as an upper extension pilot circuit L1, and the direction of switching the spool to the S3 position. A circuit for introducing the pilot pressure into the upper is referred to as an upper contraction pilot circuit L2. Further, in the control valve 6b on the lower boom cylinder 8 side, a circuit for introducing pilot pressure in a direction for switching the spool from the neutral S2 position to the S3 position is called a lower extension pilot circuit L3, and a direction for switching the spool to the S1 position. The circuit that introduces the pilot pressure into the lower is referred to as a lower-reduction pilot circuit L4.

  The upper extension pilot circuit L1 and the upper contraction pilot circuit L2 are connected to the secondary side of the remote control valve 16 that opens and closes according to the amount of operation of the upper boom 35 to the operation lever. On the other hand, the lower extension pilot circuit L3 and the lower contraction pilot circuit L4 are connected to the secondary side of the remote control valve 17 that opens and closes according to the operation amount of the lower boom 34 to the operation lever. Each of these pilot circuits L1 to L4 transmits a pilot pressure corresponding to the operation amount of the operator to each control valve 6a, 6b.

  As shown in FIG. 3, on each of the upper extension pilot circuit L1, the upper contraction pilot circuit L2 and the lower extension pilot circuit L3, electromagnetic proportional pressure reducing valves 3, 4 for suppressing the transmitted pilot pressure by electromagnetic control. , 5 are interposed. The first electromagnetic proportional pressure reducing valve 3 on the upper extension pilot circuit L1 limits the upper limit value of the pilot pressure transmitted from the remote control valve 16a corresponding to the extension operation of the upper boom 35. Similarly, the second electromagnetic proportional pressure reducing valve 4 and the third electromagnetic proportional pressure reducing valve 5 are pilot pressures transmitted from the remote control valve 16b corresponding to the retracting operation of the upper boom 35 and the remote control valve 17a corresponding to the extending operation of the lower boom 34, respectively. Limit the upper limit of. The opening degree of these electromagnetic proportional pressure reducing valves 3, 4, 5 is controlled by the controller 20.

[3. Controller configuration]
The controller 20 is an electronic control device configured by a microcomputer, and is provided as an LSI device in which a known microprocessor, ROM, RAM, and the like are integrated. As shown in FIG. 4, the controller 20 includes a member data storage device 21, an attitude calculator 22, a maximum signal generator 23, an output setting device 24 (one of the control means during excavation mode), and a first signal switching device 25 ( One of the excavation mode control means), a dismantling work signal generator 26 and a second signal switching device 27 (dismantling mode control means). Note that these configurations may be provided as an electronic circuit or software.

Connected to the input side of the controller 20 are the above-described work mode switch 1, the upper boom angle sensor 2a, and the lower boom angle sensor 2b. Information on the work mode selected by the work mode switch 1 is input to the first signal switch 25 and the second signal switch 27.
The member data storage 21 includes a length from the base end (the pivot center with the frame 39) to the tip (the pivot center with the upper boom 35) of the lower boom 34 and the base end (the pivot with the lower boom 34). The length from the center) to the tip is stored.

The posture calculator 22 calculates the tip height H of the upper boom 35 based on the elevation angles detected by the upper boom angle sensor 2 a and the lower boom angle sensor 2 b and the length stored in the member data storage 21. . The tip height H calculated here is input to the output setting unit 24.
The output setting unit 24 sets the upper limit value of the pilot pressure of the upper contraction pilot circuit L2 and the lower extension pilot circuit L3 according to the tip height H. Here, as shown in the graph of FIG. 5, the tip has a sufficiently high upper limit is set in the case of the first height h less than ₁ the height H is set in advance, the pilot pressure is not suppressed. On the other hand, the tip height H in the case where the first height h ₁ above, the tip height H is restricted higher upper limit is low, is set to zero comes to the second height h ₂ above. The upper limit value of the pilot pressure set here is input to the excavation side of the first signal switch 25.

  The maximum signal generator 23 sets an upper limit value of a sufficiently high pilot pressure. The upper limit value of the pilot pressure set here means a value corresponding to the maximum pilot pressure generated in the pilot circuits L1 to L4 when the operation lever of the upper boom 35 and the operation lever of the lower boom 34 are fully operated. It is used when the pilot pressure is not suppressed. The upper limit value of the pilot pressure set here is input to the dismantling side of the first signal switch 25 and the excavation side of the second signal switch 27.

The dismantling work signal generator 26 sets an upper limit value of the low pressure rather than the upper limit value of the pilot pressure related to the setting in the maximum signal generator 23. The upper limit value set here is a signal for suppressing the lowering speed of the front work machine 33 when the dismantling work machine 30 is in the posture of extending the front work machine 33 upward. 27 is input to the dismantling side.
The first signal switch 25 and the second signal switch 27 selectively control the opening degree of each of the electromagnetic proportional pressure reducing valves 3, 4, 5 according to the selected work mode. First, when the work mode selected by the work mode changeover switch 1 is the dismantling mode, the first signal switch 25 is input from the maximum signal generator 23 among the two types of input upper limit values. The upper limit value is selected and the opening degree of the second electromagnetic proportional pressure reducing valve 4 and the third electromagnetic proportional pressure reducing valve 5 is controlled. On the other hand, when the work mode is the excavation mode, the upper limit value input from the output setting unit 24 is selected to control the opening degree of the second electromagnetic proportional pressure reducing valve 4 and the third electromagnetic proportional pressure reducing valve 5. .

Further, when the work mode is the dismantling mode, the second signal switching device 27 selects the upper limit value input from the dismantling signal generator 26 and controls the opening degree of the first electromagnetic proportional pressure reducing valve 3. To do. On the other hand, when the work mode is the excavation mode, the upper limit value input from the maximum signal generator 23 is selected to control the opening degree of the first electromagnetic proportional pressure reducing valve 3.
The control contents of the controller 20 in the hydraulic control apparatus according to the present embodiment are summarized as follows.

As described above, the output setting unit 24 and the first signal switching unit 25 are selected when the excavation mode is selected by the work mode switching switch 1 and the tip height H is equal to or higher than the preset first height h _1. Furthermore, it functions as an excavation mode control means for reducing the opening degree of the second electromagnetic proportional pressure reducing valve 4 and the third electromagnetic proportional pressure reducing valve 5 according to the tip height H. The second signal switch 27 functions as a dismantling mode control means for restricting the opening degree of the first electromagnetic proportional pressure reducing valve 3 when the dismantling mode is selected by the work mode switching switch 1.

[4. Action]
[4-1. In dismantling mode]
As shown in FIG. 1, at the time of dismantling work on the upper object, the dismantling mode is selected by operating the work mode changeover switch 1 by the operator. In the disassembly mode, the upper limit value of the pilot pressure of the upper extension pilot circuit L1 is limited to the value set by the disassembly work signal generator 26, and the opening degree of the first electromagnetic proportional pressure reducing valve 3 is reduced. Thereby, when the operator operates the operation lever of the upper boom 35 in the lowering direction, the pilot pressure transmitted to the control valve 6a via the upper extension pilot circuit L1 is limited.

  FIG. 6 shows the opening characteristics of the control valve 6a. The spool of the control valve 6a moves in accordance with the input pilot pressure (ie, generally the lever operation amount), and simultaneously controls the flow path opening in the center bypass direction, cylinder direction, and tank direction. doing. In the hydraulic circuit of the present embodiment, since the maximum value of the pilot pressure input to the control valve 6a is limited, the position B where the spool moves with the maximum pilot pressure and the position of the spool when the control valve 6a is neutral. Each channel opening is set with O.

Accordingly, the flow rate of hydraulic oil supplied to the head chamber side of the upper boom cylinder 7 is reduced and the upper boom cylinder 7 is difficult to extend, and the flow rate of return oil from the rod chamber side to the tank 15 is also reduced. Falling is suppressed.
Further, the opening degrees of the second electromagnetic proportional pressure reducing valve 4 and the third electromagnetic proportional pressure reducing valve 5 are opened to the maximum, and the pilot pressures of the upper contraction pilot circuit L2 and the lower extension pilot circuit L3 are not limited. As a result, the secondary pressures of the remote control valves 16b and 17a are introduced into the control valves 6a and 6b, respectively, while maintaining the magnitude corresponding to the lever operation. Therefore, the upper boom 35 is raised, the lower boom 34 is lowered, and the lower boom 34 is moved. The raising operation becomes smooth without being limited in speed.

[4-2. In excavation mode]
As shown in FIG. 2, at the time of dismantling and excavation work of the lower object, the work mode changeover switch 1 is operated by the operator to select the excavation mode. In the excavation mode, the opening degree of the first electromagnetic proportional pressure reducing valve 3 is opened to the maximum, and the pilot pressure of the upper extension pilot circuit L1 is not limited. The flow path opening of the control valve 6a has a spool position (valve stroke) set between a position O and a position A in FIG. As a result, the secondary pressure of the remote control valve 16a is introduced into the control valve 6a with the magnitude corresponding to the lever operation, so the lowering operation of the upper boom 35 and the raising operation of the lower boom 34 are smoothly performed without speed limitations. Become.

On the other hand, the opening degree of the second electromagnetic proportional pressure reducing valve 4 and the third electromagnetic proportional pressure reducing valve 5 is controlled according to the height H of the tip T of the upper boom 35 shown in FIG.
When the tip height H is less than the first height h ₁ , a sufficiently high pilot pressure upper limit value is set by the output setting unit 24 of the controller 20, so that the upper contraction pilot circuit L 2 and the lower extension pilot circuit The pilot pressure of L3 is not suppressed. Accordingly, as in the dismantling mode, the raising operation of the upper boom 35 and the lowering operation of the lower boom 34 are smooth without being limited in speed.

When the front work machine 33 is lifted until the tip height H becomes equal to or higher than the first height h ₁ , the upper limit value of the pilot pressure is lowered by the output setting unit 24 of the controller 20 according to the height H. Thus, for example, if the operating lever of the upper boom 35 is fully operated in the raising direction, a large secondary pressure corresponding to the amount of operation is output from the remote control valve 16b, but the first retracted pilot circuit L2 is interposed. Since the pressure is reduced in the two electromagnetic proportional pressure reducing valve 4, the operation amount of the spool of the control valve 6a is reduced. Accordingly, the speed of the reduction operation of the upper boom cylinder 7 is suppressed, and the upper boom 35 moves slowly in the raising direction. Further, since the speed in the extending direction of the lower boom cylinder 8 is also suppressed, the operation in the raising direction of the lower boom 34 becomes slow.

Further, when the tip height H front operating mechanism 33 is lifted until the second height h ₂ above, the upper limit value of the pilot pressure set by the output setting unit 24 is zero. Accordingly, the reduction operation of the upper boom cylinder 7 and the extension operation of the lower boom cylinder 8 are prohibited, and the upper boom 35 and the lower boom 34 do not move any further.

[5. effect]
As described above, according to the hydraulic control circuit, it is possible to prevent the upper boom 35 from dropping by suppressing the extension of the upper boom cylinder 7 in the dismantling mode in which the front work machine 33 is positioned upward. For example, even if an attachment such as a heavy crusher 37 is attached, the posture of the front work machine 33 is not lowered by its own weight. On the other hand, in the excavation mode in which the front work machine 33 is positioned below, the operation in the extending direction of the upper boom cylinder 7 is not suppressed, so that favorable operability and workability can be obtained.

  Further, in the excavation mode, when the tip height H of the upper boom 35 is increased, the upper boom cylinder 7 is restrained from moving in the shortening direction and the lower boom cylinder 8 in the extending direction to prevent the front work machine 33 from being lifted. can do. Thereby, the operation range of the front work machine 33 in the excavation mode can be informed to the operator. Further, since the upper boom 35 and the lower boom 34 are prevented from rising, the fall can be reliably prevented.

In particular, in the present invention, when the tip height H becomes equal to or higher than the first height h ₁ , even if the full lever is operated, the upper boom 35 and the lower boom 34 operate slowly, and further stop at the second height h ₂ . Therefore, the movable range of the front work machine 33 can be divided in the height direction.

Further, since the tip height H of the upper boom 35 is calculated on the basis of the respective elevation angles detected by the upper boom angle sensor 2a and the lower boom angle sensor 2b, it is possible to perform an accurate calculation with a simple configuration and with little error, and thus an accurate Control becomes possible.
Thus, according to the hydraulic control device for a work machine of the present invention, good operability and workability can be obtained regardless of the work posture.

[6. Modified example]
Then, the modification with respect to the above-mentioned embodiment is demonstrated. In the above-described embodiment, the tip height H of the upper boom 35 is not used for control in the disassembly mode, but the opening degree of the first electromagnetic proportional pressure reducing valve 3 is controlled according to the tip height H. It is also possible to do.

For example, the upper limit value of the pilot pressure set by the dismantling work signal generator 26 of the controller 20 may be lowered as the tip height H is lower. That is, as shown in FIG. 7, the distal end when the height H is preset predetermined third height h ₃ than the orientation, the upper limit value of the pilot pressure than in the third height h ₃ or more posture And the opening degree of the first electromagnetic proportional pressure reducing valve 3 is further reduced. By such control, it is possible to make it difficult for the upper boom 35 to be lowered as the tip height H becomes lower in the dismantling mode, and the fall prevention effect of the front work machine 33 can be further enhanced.

The setting value of the third height h ₃ is arbitrary, and the first height h ₁ and the second height h ₂ may be set independently, or the second height h ₂ a it may be set to the same with the three height h _3. Further, if the upper limit value of the pilot pressure is set to zero when the tip height H becomes too low, further lowering operation can be prohibited.
The control contents of the controller 20 in the hydraulic control apparatus of this modification are summarized as follows.

  In addition to the configuration in which the upper limit value of the pilot pressure as shown in FIG. 7 is given by a function set in advance with respect to the tip height H, the load acting on the upper boom cylinder 7 and the lower boom cylinder 8 is large. It is also possible to make it changeable accordingly. For example, the load is calculated using a known load pressure sensor or a sensor that detects the stroke fluctuation speed of the hydraulic cylinder, and the opening degree of the first electromagnetic proportional pressure reducing valve 3 is reduced as the load increases. . Operability can be further improved by such aperture control according to the load.

  That is, when the heavy attachment is attached, the front work machine 33 can be made difficult to drop by making the first electromagnetic proportional pressure reducing valve throttle smaller than when the light attachment is attached. Further, it is possible to make the operation speed of the front work machine 33 constant regardless of the weight of the attachment.

  It is also conceivable to change the tip height H for starting the throttle control in the first electromagnetic proportional pressure reducing valve 3 in accordance with the magnitude of the load. Such control can prevent the upper boom 34 from dropping more reliably. For example, when a heavy attachment is worn, the amount of suppression can be increased from a relatively higher position than when a small attachment is worn.

  In addition, the opening degree control according to the magnitude | size of the load which acts on the upper boom cylinder 7 and the lower boom cylinder 8 is not only the 1st electromagnetic proportional pressure reducing valve 3, but the 2nd electromagnetic proportional pressure reducing valve 4 and the 3rd electromagnetic proportional pressure reducing valve. The present invention can also be applied to the opening degree control of the valve 5.

[7. Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the upper boom angle sensor 2 a and the lower boom angle sensor 2 b detect the elevation angles of the upper boom 35 and the lower boom 34, but the relative angles of the upper boom 35 and the lower boom 34, It is good also as a structure which detects a relative angle with the turning body 32 (or frame 39). In this case, the tip height H may be calculated in consideration of the inclination of the vehicle body of the dismantling work machine 30.

  In the above-described embodiment, the present invention is applied to the dismantling machine 30 provided with the crusher 37 as an attachment. However, a general hydraulic excavator, a bulldozer, a wheel loader, a hydraulic crane, etc. It can be applied to hydraulic circuits of various work machines.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view illustrating an entire configuration of a dismantling work machine equipped with a hydraulic control device for a work machine according to an embodiment of the present invention, and illustrates a posture in a dismantling mode in which an upper object is disassembled. In the demolition work machine of FIG. 1, the posture in the excavation mode in which a lower object is dismantled and excavated is shown. It is a hydraulic circuit diagram of the present invention. It is a control block diagram which shows the function of the controller of this invention. It is a graph which shows the setting of the upper limit of the lower boom extension side pilot pressure and upper boom contraction side pilot pressure in the present invention. It is a graph which shows the opening characteristic of the control valve of this invention. It is a graph which shows the setting of the upper limit of upper boom extension side pilot pressure of the modification of the present invention.

Explanation of symbols

1 Work mode changeover switch 2a Upper boom angle sensor (one of height detection means)
2b Lower boom angle sensor (one of height detection means)
3 First electromagnetic proportional pressure reducing valve 4 Second electromagnetic proportional pressure reducing valve 5 Third electromagnetic proportional pressure reducing valve 6a, 6b Control valve 7 Upper boom cylinder 8 Lower boom cylinder 11 Hydraulic pump 12 Regulator 13 Engine 14 Pilot pump 15 Tank 16, 17 Remote control Valve 20 Controller 21 Material data memory 22 Attitude calculator 23 Maximum signal generator 24 Output setting device (one of the control means during excavation mode)
25 1st signal switcher (one of the control means during excavation mode)
26 Demolition work signal generator 27 Second signal switcher (disassembly mode control means)
30 Demolition work machine 33 Front work machine 34 Lower boom 35 Upper boom L1 Upper extension pilot circuit L2 Upper contraction pilot circuit L3 Lower extension pilot circuit L4 Lower contraction pilot circuit

Claims (6)

Work to drive a two-piece boom composed of an upper boom and a lower boom by expanding and contracting the upper boom cylinder and the lower boom cylinder, having a dismantling mode for disassembling the upper object and an excavation mode for disassembling the lower object A hydraulic control device for the machine,
A work mode switch for switching between the dismantling mode and the excavation mode;
A first electromagnetic proportional pressure reducing valve interposed in a pilot circuit for driving the upper boom cylinder in the extending direction;
A second electromagnetic proportional pressure reducing valve interposed in a pilot circuit for driving the upper boom cylinder in a shortening direction;
A third electromagnetic proportional pressure reducing valve interposed in a pilot circuit for driving the lower boom cylinder in the extending direction;
Height detecting means for detecting the tip height of the upper boom;
When the dismantling mode is selected with the work mode switch, the dismantling mode time control means for restricting the opening of the first electromagnetic proportional pressure reducing valve;
When the excavation mode is selected by the work mode changeover switch and the tip height detected by the height detecting means is equal to or higher than a preset first height, A hydraulic control device for a work machine, comprising: an excavation mode control means for restricting an opening degree of the second electromagnetic proportional pressure reducing valve and the third electromagnetic proportional pressure reducing valve. The excavation mode control means is
When the excavation mode is selected by the work mode changeover switch and the tip height detected by the height detection means is equal to or higher than a second height higher than the first height, the second electromagnetic The hydraulic control device for a work machine according to claim 1, wherein the proportional pressure reducing valve and the third electromagnetic proportional pressure reducing valve are closed. The height detection means
A first angle sensor for detecting an elevation angle of the upper boom;
The hydraulic control device for a work machine according to claim 1, further comprising a second angle sensor that detects an elevation angle of the lower boom. 該解body mode control means,
When the dismantling mode is selected by the work mode changeover switch and the tip height detected by the height detection means is less than a preset third height, the tip height is the third height. The hydraulic control device for a work machine according to any one of claims 1 to 3, wherein the opening degree of the first electromagnetic proportional pressure reducing valve is further reduced than when the height is equal to or higher than the height. Load detecting means for detecting a load acting on the upper boom cylinder and the lower boom cylinder;
5. The hydraulic control device for a work machine according to claim 4, wherein the third height is changed according to the magnitude of the load detected by the load detection means. 6. The hydraulic control device for a work machine according to claim 5, wherein the throttle opening of the first electromagnetic proportional pressure reducing valve is changed according to the magnitude of the load detected by the load detecting means.

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