JP2014202220A - Hydraulic transmission for construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the present invention to be adapted for both of an attachment requiring a large flow rate and an attachment requiring a small flow rate without requiring a replacement and reform of a control valve and limiting a pilot pressure changing-over a direction changing over valve for the attachment.SOLUTION: A hydraulic transmission of this invention is installed at a mini-shovel, for example, and it has a selector valve device 34 for changing over a flow rate supplied to a direction changing-over valve 6 acting as a direction changing-over valve for an attachment to any one of a large flow rate merging hydraulic oil of a second hydraulic pump P2 and hydraulic oil of a third hydraulic pump P3 and a small flow rate corresponding to hydraulic oil of only the second hydraulic pump P2. The selector valve device 34 is disposed outside a control valve 2 and enables a supply of the hydraulic oil of the third hydraulic pump P3 to the control valve 2 and a discharge thereof to a tank T in response to the instruction positions H and L of a flow rate changing-over switch 33 to be selectively carried out.

Description

  The present invention relates to a hydraulic drive device for a construction machine such as a hydraulic excavator that can supply pressure actuators of a plurality of hydraulic pumps to an attachment actuator that drives an attachment such as a crusher.

  As a first prior art, there is a hydraulic excavator having a traveling body and a revolving body constituting a vehicle body, and a working device attached to the revolving body, that is, a front working machine, and a plurality of hydraulic pumps, that is, a first hydraulic pump, a second hydraulic pressure A hydraulic pressure pump of the second hydraulic pump and the hydraulic pressure of the third hydraulic pump are merged by a switching operation of an attachment direction switching valve that is provided with a pump and a third hydraulic pump and controls an attachment actuator. There is known a hydraulic drive apparatus that supplies an actuator for attachment to drive the corresponding attachment.

  As a second conventional technique, Patent Document 1 proposes a hydraulic drive device that can handle both a first attachment with a large required flow rate and a second attachment with a small required flow rate. . This second prior art is also provided in a construction vehicle such as a hydraulic excavator, that is, a construction machine. The second prior art includes a plurality of hydraulic pumps, that is, a first hydraulic pump, a second hydraulic pump, and a third hydraulic pump, and a plurality of actuators that are driven by pressure oil discharged from these hydraulic pumps and include an actuator for attachment. Actuator. In addition, the second prior art includes a control valve that includes a plurality of directional switching valves including an attachment directional switching valve that controls the flow of pressure oil supplied to the plurality of actuators and controls the attachment actuator. Yes. In addition, the second prior art includes a plurality of operation devices including an attachment operation device that switches each of the plurality of direction switching valves and switches each of the attachment direction switching valves. In the second prior art, the flow rate supplied to the directional switching valve for attachment is a large amount in which the pressure oil of a plurality of hydraulic pumps, that is, the pressure oil of the second hydraulic pump and the pressure oil of the third hydraulic pump are merged. There is provided an open control valve, that is, a switching valve device, for switching between a flow rate and a small flow rate corresponding to a single hydraulic pump among a plurality of hydraulic pumps, that is, pressure oil of only the second hydraulic pump. This open control valve is built in the control valve together with each direction switching valve.

Japanese Patent No. 4139352

  In the second prior art described in Patent Document 1 described above, both attachments requiring a large flow rate such as a crusher and attachments requiring a small flow rate such as a breaker can be supported. However, in the case where the existing hydraulic drive device provided in the construction machine is configured to be compatible only with an attachment that requires a large flow rate as in the first prior art, a small amount is used instead of the attachment that requires a large flow rate. There is a problem when you want to install a flow attachment.

  Such a case has conventionally been dealt with by changing or modifying the control valve, limiting the pilot pressure for switching the attachment direction switching valve, or the like. However, replacement of the control valve has a problem that requires a large amount of money and work. In addition, the modification of the control valve has a problem that it is difficult to ensure performance and quality assurance after the modification. Further, the restriction of the pilot pressure for switching the attachment direction switching valve has a problem that the supply flow rate to the attachment actuator is not stabilized due to the influence of the load pressure of the attachment, and the reliability is likely to be lowered.

  The present invention has been made from the actual situation in the prior art described above, and its purpose is that the required flow rate is a large flow rate without requiring control valve replacement or modification, and restriction of pilot pressure for switching the directional switching valve for attachment. Another object of the present invention is to provide a hydraulic drive device for a construction machine that can handle both the attachment and the attachment that requires a small flow rate.

  In order to achieve this object, the present invention is provided in a construction machine having a vehicle body and a work device attached to the vehicle body, an engine, a plurality of hydraulic pumps driven by the engine, and these hydraulic pumps A plurality of actuators including an attachment actuator driven by the pressure oil discharged from the controller, and an attachment direction switching valve for controlling the flow of the pressure oil supplied to the plurality of actuators and controlling the attachment actuator. A construction comprising a control valve incorporating a plurality of directional control valves, and a plurality of operation devices including an operation device for attachment for switching each of the plurality of directional control valves and switching the attachment directional control valve. In the hydraulic drive device of the machine, the attachment direction The flow rate supplied to the valve is either a large flow rate that combines the pressure oils of the plurality of hydraulic pumps, or a small flow rate that corresponds to the pressure oil of only a single hydraulic pump among the plurality of hydraulic pumps. A switching valve device for switching, wherein the switching valve device is disposed outside the control valve, and is configured to be the single hydraulic pump among the plurality of hydraulic pumps that supply the large flow rate to the attachment direction switching valve. Is characterized in that it can selectively supply pressure oil from different hydraulic pumps to the control valve and discharge to the tank.

  In the present invention configured as described above, when an attachment having a large required flow rate is attached, the switching valve device is a hydraulic oil of a hydraulic pump different from a single hydraulic pump among a plurality of hydraulic pumps. Is switched to supply the control valve. As a result, a large flow rate obtained by joining the pressure oil of a single hydraulic pump and the pressure oil of a hydraulic pump different from the single hydraulic pump is supplied to the attachment direction switching valve built in the control valve. It is supplied to the attachment actuator via the attachment direction switching valve. Accordingly, the attachment actuator is driven, and a desired work with the corresponding attachment having a large required flow rate can be realized.

  In addition, when an attachment with a small required flow rate is attached, the switching valve device causes the hydraulic oil of the hydraulic pump different from the single hydraulic pump among the plurality of hydraulic pumps to be discharged to the tank. Can be switched. As a result, only the pressure oil of the single hydraulic pump is supplied to the attachment direction switching valve built in the control valve, and is supplied to the attachment actuator via this attachment switching valve. Therefore, the attachment actuator is driven, and a desired work with the corresponding attachment having a small required flow rate can be realized.

  Thus, the switching valve device provided in the present invention for switching the flow rate supplied to the attachment direction switching valve to either the large flow rate or the small flow rate is arranged outside the control valve. It can be provided without modification and without requiring restriction of the pilot pressure for switching the directional control valve for attachment.

  In the present invention, the plurality of hydraulic pumps include a first hydraulic pump, a second hydraulic pump, and a third hydraulic pump, and the switching valve device supplies the attachment direction switching valve. Switching valve for switching the flow rate to be either a large flow rate that combines the pressure oil of the second hydraulic pump and the pressure oil of the third hydraulic pump or a small flow rate corresponding to the pressure oil of only the second hydraulic pump It consists of a device.

  Further, the present invention is characterized in that, in the above invention, the switching valve device includes an instruction device that outputs a signal instructing that either the large flow rate or the small flow rate can be supplied.

  According to the present invention, in the above invention, the attachment operation device includes an operation pedal that outputs a control pilot pressure corresponding to an operation amount, and includes a pressure detection unit that detects the control pilot pressure output from the operation pedal. The switching valve device includes an electromagnetic switching valve that is switched in response to a signal output from the indicating device, and the pressure detection unit that is provided downstream of the electromagnetic switching valve and is supplied via the electromagnetic switching valve. And a hydraulic pilot switching valve that is switched according to the control pilot pressure detected in step (1).

  In the invention described above, the attachment operating device includes an operation pedal that outputs a control pilot pressure corresponding to an operation amount, and a pressure detection unit that detects the control pilot pressure output from the operation pedal; A controller that outputs a signal corresponding to the control pilot pressure detected by the pressure detector, a signal output from the indicating device, and a control signal based on the signal output from the pressure sensor The switching valve device comprises an electromagnetic switching valve that is switched in response to the control signal output from the controller.

  In the present invention, since the switching valve device is arranged outside the control valve, the required flow rate becomes a large flow rate without the need for replacement or modification of the control valve and restriction of the pilot pressure for switching the directional switching valve for attachment. It can handle both attachments and attachments where the required flow rate is small. Thus, the present invention can be easily applied even to existing hydraulic drive devices. Thus, when applied to an existing hydraulic drive device, the present invention can reduce the installation cost and improve the efficiency of the installation work as compared with the prior art.

It is a side view which shows the mini excavator mentioned as an example of the construction machine made into the object of this invention. It is a hydraulic circuit diagram which shows the existing hydraulic drive apparatus with which the mini excavator shown in FIG. 1 is equipped. 1 is a hydraulic circuit diagram showing a first embodiment of a hydraulic drive device for a construction machine according to the present invention. It is a hydraulic circuit diagram which shows 2nd Embodiment of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a hydraulic drive device for a construction machine according to the present invention will be described with reference to the drawings.

  First, a mini excavator cited as an example of a construction machine provided with a hydraulic drive device according to the present invention will be described with reference to FIG. 1, and an existing hydraulic drive device provided in the mini excavator will be described with reference to FIG. explain.

  As shown in FIG. 1, the mini excavator includes a revolving body 300 and a traveling body 301 that constitute a vehicle body. In addition, a work device that performs soil excavation work, that is, a front work machine 302 is provided. The front work machine 302 includes a boom 306, an arm 307, and a bucket 308. The turning body 300 turns on the traveling body 301 by driving the turning motor 13. A swing post 303 is attached to the swivel body 300, and the above-described front work machine 302 is attached to the swing post 303 so as to be rotatable in the vertical direction. The front work machine 302 rotates the boom cylinder 18 that drives the boom 306, the arm cylinder 15 that drives the arm 307, and the bucket cylinder 19 that drives the bucket 308 by operating the operation lever devices 20 and 21. To do. A blade 304 that moves up and down by the expansion and contraction of the blade cylinder 12 is attached to the traveling body 301 and travels by driving the right traveling motor 16 and the left traveling motor 17.

  As shown in FIG. 2, the existing hydraulic drive device provided in the mini excavator shown in FIG. 1 includes an engine 1, a plurality of hydraulic pumps driven by the engine 1, such as a first hydraulic pump P <b> 1 and a second hydraulic pump. A hydraulic pump P2 and a third hydraulic pump P3 are provided. In addition, a pilot pump P4 driven by the engine 1 is provided in conjunction with these hydraulic pumps P1, P2, P3.

  Also, a plurality of actuators driven by pressure oil discharged from the first hydraulic pump P1, a plurality of actuators driven by pressure oil discharged from the second hydraulic pump P2, and a third hydraulic pump discharged And a plurality of actuators driven by pressure oil.

  The plurality of actuators driven by the pressure oil discharged from the first hydraulic pump P1 includes, for example, the left traveling motor 17, the boom cylinder 18, and the bucket cylinder 19 described above.

  The plurality of actuators driven by the pressure oil discharged from the second hydraulic pump P <b> 2 includes, for example, the right traveling motor 16 and the arm cylinder 15 described above.

  The plurality of actuators driven by the pressure oil discharged from the third hydraulic pump P3 includes, for example, the blade cylinder 12, the turning motor 13, and the swing cylinder 14 described above.

  A control valve 2 is disposed between the first, second, and third hydraulic pumps P1, P2, and P3 and the plurality of actuators described above. In the control valve 2, a plurality of directional switching valves including a directional switching valve 6 which is an directional switching valve for attachment that controls an attachment actuator are incorporated.

  That is, each of the control valves 2 is connected to the first hydraulic pump P1 and controls the flow of pressure oil supplied to the left traveling motor 17, and the flow of pressure oil supplied to the boom cylinder 18. And a directional switching valve 11 for controlling the flow of pressure oil supplied to the bucket cylinder 19 are incorporated.

  The control valve 2 is connected to the second hydraulic pump 12, and controls the flow of pressure oil supplied to the right travel motor 16. The flow of pressure oil supplied to the arm cylinder 15. And a direction switching valve 6 which is an attachment direction switching valve for controlling the flow of pressure oil supplied to an attachment actuator (not shown). The direction switching valve 6 that is an attachment direction switching valve is also connected to the third hydraulic pump P3.

  Further, the control valve 2 is connected to a third hydraulic pump P3, and controls the direction switching valve 3 for controlling the flow of pressure oil supplied to the blade cylinder 12 and the flow of pressure oil supplied to the swing motor 13. A direction switching valve 4 to be controlled and a direction switching valve 5 to control the flow of pressure oil supplied to the swing cylinder 14 are also incorporated.

  Further, the existing hydraulic drive device shown in FIG. 2 outputs the pilot pressures a and b, thereby outputting the operation device for switching the direction switching valve 10 for controlling the boom cylinder 18 and the pilot pressures c and d. Thus, an operation lever device 20 including an operation device for switching the direction switching valve 11 for controlling the bucket cylinder 19 is provided.

  Further, an operation device for switching the direction switching valve 7 for controlling the arm cylinder 15 by outputting the pilot pressures e and f, and a direction switching for controlling the turning motor 13 by outputting the pilot pressures g and h. An operating lever device 21 for switching the valve 4 is provided.

  Further, an operation lever device 22 for switching the direction switching valve 3 for controlling the blade cylinder 12 by outputting pilot pressures o and p is provided.

  Further, the direction switching valve 8 for controlling the right traveling motor 16 is switched by outputting the pilot pressures i and j, and the direction switching for controlling the left traveling motor 17 by outputting the pilot pressures k and l. An operating device for switching the valve 9, for example, an operating pedal 23 is provided.

  Further, an operation device, for example, an operation pedal 24 is provided for switching the direction switching valve 5 for controlling the swing cylinder 14 by outputting the pilot pressures m and n.

  In addition, an operation device, for example, an operation pedal 25, for switching the direction switching valve 6 which is an attachment direction switching valve for controlling an attachment (not shown) by outputting pilot pressures q and r is provided. The operation pedal 25 constitutes an attachment operation device.

  Further, the existing hydraulic drive device shown in FIG. 2 includes a main relief valve 26 that regulates the discharge pressure of the first hydraulic pump P1, a main relief valve 27 that regulates the discharge pressure of the second hydraulic pump P2, and a third hydraulic pressure. And a main relief valve 28 that regulates the discharge pressure of the pump P3. The outlet sides of these main relief valves 26, 27, 28 are connected to the oil passage 31 in the control valve 2 and connected to the tank T.

  Also, a pilot that supplies pressure oil that generates the above-described pilot pressures a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r. A pilot relief valve 29 that regulates the discharge pressure of the pump P4 is provided.

  In the existing hydraulic drive device configured as described above, the pilot pressure a− based on the pressure oil discharged from the pilot pump P4 is obtained by operating the operation lever device 20-22 and the operation pedal 23-25. r is guided to the corresponding one of the directional control valves 3-11 included in the control valve 2, and the corresponding directional control valve is switched.

  The oil discharged from the first hydraulic pump P1 flows into the tank T via the direction switching valve 9-11 when the corresponding one of the operation lever device 20 and the operation pedal is neutral, but the operation lever device 20 and the operation pedal 23 When the corresponding one is operated, the corresponding one of the direction switching valves 9-11 is switched, and the corresponding actuator among the left traveling motor 17, the boom cylinder 18 and the bucket cylinder 19 can be operated.

  The oil discharged from the second hydraulic pump P2 corresponds to the operation lever device 21, the operation pedal 23, and the directional switching valves 8 and 7 and the attachment directional switching valve when the operation pedal 25 is an attachment operation device. It flows into the tank T through the directional switching valve 6, and when any one of the operation lever device 21, the operation pedal 23, and the operation pedal 25 is operated, it corresponds to the direction switching valve 6-8. Are switched, and the right travel motor 16, the arm cylinder 15, and an actuator (not shown) corresponding to the actuator are operated.

  The oil discharged from the third hydraulic pump P3 corresponds to the operation lever device 21, the operation lever device 22, the operation pedal 24, and the operation pedal 25 which is an operation device for attachment. The tank T flows into the tank T through the direction switching valve 6 that is an attachment direction switching valve. When any one of the operation lever device 22, the operation pedal 24, and the operation pedal 25 is operated, the direction switching valve 3-6 Are switched to operate the corresponding actuator among the boom cylinder 12, the swing motor 13, the swing cylinder 14, and an attachment actuator (not shown).

  That is, in the existing hydraulic drive device shown in FIG. 2, instead of the bucket 308 included in the front work machine 302 described above, for example, when a crusher having a large required flow rate is attached as an attachment, By operating 25, the pressure oil of the second hydraulic pump P2 and the pressure oil of the third hydraulic pump P3 merge and are supplied to the direction switching valve 6 to drive the crusher.

  Next, a hydraulic drive device for a construction machine according to a first embodiment of the present invention will be described with reference to FIG. The first embodiment is applied to, for example, the mini excavator shown in FIG. 1 provided with the existing hydraulic drive device shown in FIG. 2 described above. Therefore, the basic configuration of the present embodiment is the same as that of the existing hydraulic drive device shown in FIG.

  That is, like the existing hydraulic drive apparatus shown in FIG. 2, this embodiment also uses the engine 1 and a plurality of hydraulic pumps driven by the engine 1, for example, the first hydraulic pump P 1, the second hydraulic pump P 2, and And a third hydraulic pump P3. In addition, a plurality of actuators including an attachment actuator (not shown), that is, a blade cylinder 12, a swing motor 13, a swing cylinder 14, an arm cylinder 15, a right travel motor 16, a left travel motor 17, a boom cylinder 18, and a bucket cylinder 19 are provided. ing.

  Also, a plurality of directional control valves 3-5 and 7 including a directional control valve 6 which is an attachment directional control valve for controlling the flow of pressure oil supplied to the above-mentioned plurality of actuators and controlling an attachment actuator (not shown). A control valve 2 containing -11 is provided.

  Further, an attachment operating device, that is, an operation pedal 25 for switching the corresponding direction switching valve among the plurality of direction switching valves 3-11 and switching the direction switching valve 6 serving as the attachment direction switching valve is included. A plurality of operation devices are provided. In addition to the operation pedal 25, the plurality of operation devices include an operation lever device 20-22 and operation pedals 23 and 24.

  Further, in the present embodiment, the flow rate supplied to the direction switching valve 6 that is the direction switching valve for attachment is a large flow rate that combines the pressure oils of a plurality of hydraulic pumps, for example, the pressure oil of the second hydraulic pump P2 and the third flow rate. The flow rate is switched between a large flow rate obtained by joining the pressure oils of the hydraulic pump P3 and a small flow rate corresponding to the single hydraulic pump among the plurality of hydraulic pumps P1-P3, that is, only the second hydraulic pump P2. A switching valve device 34 is provided.

  This switching valve device 34 is arranged outside the control valve 2 and is the above-mentioned single of the second hydraulic pump P2 and the third hydraulic pump P3 that supply a large flow rate to the direction switching valve 6 that is a direction switching valve for attachment. One hydraulic pump, that is, one that selectively enables supply of pressure oil to the control valve 2 of the third hydraulic pump P3 different from the second hydraulic pump P2 and discharge to the tank T. Yes.

  For example, as shown in FIG. 3, the switching valve device 34 is arranged in an oil passage 31B branched from an oil passage 31A for supplying the pressure oil of the third hydraulic pump P3 to the control valve 2 and communicating with the tank T. It is.

  In the present embodiment, the switching valve device 34 has a large flow rate in which the pressure oil of the second hydraulic pump P2 and the pressure oil of the third hydraulic pump P3 are merged, and a small flow rate of only the pressure oil in the second hydraulic pump P2. An indicating device that outputs a signal that can supply any flow rate is provided. This indicating device comprises a flow rate switch 33 having an indicating position H for a large flow rate and an indicating position L for a small flow rate.

  Further, the present embodiment includes a pressure detection unit that outputs, that is, detects the control pilot pressure S output from the operation pedal 25. This pressure detection part consists of the shuttle valve 37, for example.

  The switching valve device 34 is an electromagnetic switching valve 34a that is switched in response to a signal output from the flow rate switching switch 33, and a shuttle valve 37 that is disposed downstream of the electromagnetic switching valve 34a and is supplied via the electromagnetic switching valve 34a. And a hydraulic pilot switching valve 34b that is switched in accordance with the control pilot pressure S detected in step (b).

When the flow rate switch 33 is switched to the indicated position L, the electromagnetic switching valve 34a is switched to the switching position II.
The control pilot pressure S is supplied to the control unit of the downstream hydraulic pilot switching valve 34b. When switched to the designated position H, the position is switched to the switching position I, and the supply of the control pilot pressure S to the control unit of the hydraulic pilot switching valve 34b is blocked.

  When the control pilot pressure S is applied via the electromagnetic switching valve 34a, the hydraulic pilot switching valve 34b is switched to the switching position III and connects the oil passage 31A and the oil passage 31B. As a result, the oil passage 31A communicates with the tank T via the oil passage 31B, and the supply of the pressure oil of the third hydraulic pump P3 to the control valve 2 is blocked. The hydraulic pilot switching valve 34b is switched to the switching position IV when the control pilot pressure S is not applied, and disconnects the connection between the oil passage 31A and the oil passage 31B. Thereby, supply of the pressure oil of the third hydraulic pump P3 to the control valve 2 is allowed.

  In the hydraulic drive device according to the first embodiment configured as described above, when an attachment that requires a large flow rate, such as a crusher, is attached instead of the bucket 308 shown in FIG. When the operating pedal 25 is operated in this state, the electromagnetic switching valve 34a of the switching valve device 34 is held at the switching position I, and the hydraulic pilot switching valve 34b is accordingly switched to the switching position IV. Retained. As a result, the connection between the oil passage 31A and the oil passage 31B is cut off as described above, and the pressure oil of the second hydraulic pump P2 is provided in the direction switching valve 6 that is the attachment direction switching valve built in the control valve 2. And a large flow rate that is combined with the pressure oil of the third hydraulic pump P3 is supplied. Therefore, the attachment actuator (not shown) is driven by this large flow rate, and a desired operation by the corresponding crusher having a large required flow rate can be realized.

  In addition, when an attachment that requires a small flow rate, for example, a breaker, is mounted instead of the bucket 308 shown in FIG. 1, the pointing device 33 is switched to the pointing position L, and the operation pedal 25 is operated in this state. Then, the electromagnetic switching valve 34a of the switching valve device 34 is switched to the switching position II, and the hydraulic pilot switching valve 34b is switched to the switching position III by the control pilot pressure S supplied accordingly. As a result, as described above, the oil passage 31A and the oil passage 31B are connected, and the oil passage 31A communicates with the tank T through the oil passage 31B, and supplies the pressure oil of the third hydraulic pump P3 to the control valve 2. That is, the supply to the direction switching valve 6 is blocked. Accordingly, a small flow rate of only the pressure oil of the second hydraulic pump P2 is supplied to the direction switching valve 6, and an attachment actuator (not shown) is driven by this small flow rate. As a result, it is possible to realize a desired work by a corresponding breaker having a small required flow rate.

  Thus, the switching valve device 34 according to the present embodiment for switching the flow rate supplied to the direction switching valve 6 that is the attachment direction switching valve to either the large flow rate or the small flow rate is disposed outside the control valve 2. Therefore, the control valve 2 can be provided without the need to replace or modify the control valve 2 and without the restriction of the pilot pressure for switching the direction switching valve 6. Even in the existing hydraulic drive device shown in FIG. Can be easily applied. In addition, when applied to the existing hydraulic drive device shown in FIG. 2, the control cost is not required to be replaced or modified, and the pilot pressure is not limited, so that the installation cost can be reduced. The efficiency of installation work can be improved.

  FIG. 4 is a hydraulic circuit diagram showing a second embodiment of the present invention.

  The hydraulic drive device according to the second embodiment shown in FIG. 2 includes a pressure sensor 36 that outputs a signal corresponding to the control pilot pressure S detected by the shuttle valve 37 that is a pressure detection unit, and a flow rate switching that is an indication device. And a controller 38 that outputs a control signal based on a signal output from the switch 33 and a signal output from the pressure sensor 36. The switching valve device 34 includes an electromagnetic switching valve 35 that is switched according to a control signal output from the controller 38.

  The electromagnetic switching valve 35 has a switching position VI for cutting off the connection between the oil passage 31A and the oil passage 31B, and a switching position V for connecting the oil passage 31a and the oil passage 31B.

  The controller 38 detects that the signal corresponding to the indicated position H is output from the flow rate switch 33, the operation pedal 25 is operated, and the control pilot pressure S is output from the shuttle valve 37 by the pressure sensor 36. Sometimes, the electromagnetic switching valve 35 is controlled so as to keep the electromagnetic switching valve 35 of the switching valve device 34 at the switching position VI. At this time, the connection between the oil passage 31A and the oil passage 31B is interrupted. Further, the controller 38 outputs a signal corresponding to the indicated position L from the flow path selector switch 33, the operation pedal 25 is operated at the same time, and the control pilot pressure S is output from the shuttle valve 37 by the pressure sensor 36. When detected, the electromagnetic switching valve 35 is controlled so as to keep the electromagnetic switching valve 35 of the switching valve device 34 at the switching position V. At this time, the oil passage 31A and the oil passage 31B are connected, and the oil passage 31A communicates with the tank T via the oil passage 31B.

  Further, when the operation pedal 25 is not operated and the control pilot pressure S output from the shuttle valve 37 is not detected by the pressure sensor 36, the controller 38 keeps the electromagnetic switching valve 35 of the switching valve device 34 at the switching position VI. The electromagnetic switching valve 35 is controlled. Therefore, at this time, as described above, the connection between the oil passage 31A and the oil passage 31B is cut off.

  About the other structure of the above structure, it is equivalent to 1st Embodiment mentioned above.

  In the hydraulic drive device according to the second embodiment configured as described above, when an attachment that requires a large flow rate, for example, a crusher, is attached instead of the bucket 308 shown in FIG. When the operation pedal 25 is operated in this state, the controller 38 holds the electromagnetic switching valve 35 of the switching valve device 34 at the switching position VI. As a result, the connection between the oil passage 31A and the oil passage 31B is cut off, and the pressure oil of the second hydraulic pump P2 and the third hydraulic pump are provided in the direction switching valve 6 which is a directional switching valve for attachment built in the control valve 2. A large flow rate of P3 pressure oil is supplied. Therefore, the attachment actuator (not shown) is driven by this large flow rate, and a desired operation by the corresponding crusher having a large required flow rate can be realized.

  Further, when an attachment that requires a small flow rate, for example, a breaker, is mounted instead of the bucket 308 shown in FIG. 1, the pointing device 33 is switched to the pointing position L, and the operation pedal 25 is operated in this state. The electromagnetic switching valve 35 of the switching valve device 34 is switched to the switching position V by the control signal output from the controller 38. As a result, the oil passage 31A and the oil passage 31B are connected as described above, and the oil passage 31A communicates with the tank T via the oil passage 31B, and supplies the hydraulic oil to the control valve 2 of the third hydraulic pump 3. That is, the supply to the direction switching valve 6 is blocked. Accordingly, a small flow rate of only the pressure oil of the second hydraulic pump P2 is supplied to the direction switching valve 6, and an attachment actuator (not shown) is driven by this small flow rate. As a result, it is possible to realize a desired work by a corresponding breaker having a small required flow rate.

  The electromagnetic switching valve 35 is switched only when the operation pedal 25 is operated, and is not switched when the operation pedal 35 is not operated. Therefore, the swing, turning, and blade operations driven by the third hydraulic pump P3 are normally performed. Can be done on the street.

  Also in the second embodiment configured as described above, since the switching valve device 34 is arranged outside the control valve 2, the pilot pressure for switching the direction switching valve 6 is not required without replacing or modifying the control valve 2. It can be provided without requiring control, and an effect equivalent to that of the first embodiment can be obtained.

DESCRIPTION OF SYMBOLS 1 Engine 2 Control valve 3 Directional switching valve 4 Directional switching valve 5 Directional switching valve 6 Directional switching valve 7 Directional switching valve 8 Directional switching valve 9 Directional switching valve 10 Directional switching valve 11 Directional switching valve 20 Operation lever apparatus 21 Operation lever apparatus 22 Operation lever device 23 Operation pedal 24 Operation pedal 25 Operation pedal 31A Oil passage 31B Oil passage 33 Flow rate switch (indicator)
34 switching valve device 34a electromagnetic switching valve 34b hydraulic pilot switching valve 35 electromagnetic switching valve 36 pressure sensor 37 shuttle valve (pressure detector)
P1 First hydraulic pump P2 Second hydraulic pump P3 Third hydraulic pump T Tank S Control pilot pressure 300 Revolving body (vehicle body)
301 Running body (car body)
302 Front working machine (working device)

Claims (5)

Provided in a construction machine having a vehicle body and a work device attached to the vehicle body;
An engine, a plurality of hydraulic pumps driven by the engine, a plurality of actuators driven by pressure oil discharged from these hydraulic pumps, including an actuator for attachment, and a pressure oil supplied to the plurality of actuators A control valve having a plurality of directional control valves including an attachment directional control valve for controlling the flow and controlling the attachment actuator, and each of the directional control valves is operated for switching, and the directional control valve for the attachment A hydraulic drive device for a construction machine comprising a plurality of operation devices including an attachment operation device for switching between
The flow rate supplied to the attachment direction switching valve is a small flow rate corresponding to a large flow rate obtained by merging the pressure oils of the plurality of hydraulic pumps and a pressure oil of only a single hydraulic pump among the plurality of hydraulic pumps It has a switching valve device that switches to either flow rate,
The switching valve device is arranged outside the control valve, and the hydraulic oil of a hydraulic pump different from the single hydraulic pump among the plurality of hydraulic pumps that supplies the large flow rate to the attachment direction switching valve. A hydraulic drive device for a construction machine, characterized in that it can selectively supply either to the control valve or to discharge to the tank. The hydraulic drive device for a construction machine according to claim 1,
The plurality of hydraulic pumps includes a first hydraulic pump, a second hydraulic pump, and a third hydraulic pump,
In the switching valve device, the flow rate supplied to the attachment direction switching valve is a large flow rate obtained by merging the pressure oil of the second hydraulic pump and the pressure oil of the third hydraulic pump, and only the second hydraulic pump. A hydraulic drive device for a construction machine, comprising a switching valve device for switching to one of small flow rates corresponding to pressure oil. The hydraulic drive device for a construction machine according to claim 1 or 2,
A hydraulic drive device for a construction machine, comprising: an instruction device that outputs a signal that instructs the switching valve device to supply either the large flow rate or the small flow rate. The hydraulic drive device for a construction machine according to claim 3,
The attachment operating device includes an operation pedal that outputs a control pilot pressure corresponding to an operation amount,
A pressure detection unit for detecting the control pilot pressure output from the operation pedal;
The switching valve device is detected by an electromagnetic switching valve that is switched in response to a signal output from the indicating device, and a pressure detection unit that is provided downstream of the electromagnetic switching valve and is supplied via the electromagnetic switching valve. And a hydraulic pilot switching valve that is switched according to the control pilot pressure. The hydraulic drive device for a construction machine according to claim 3,
The attachment operating device includes an operation pedal that outputs a control pilot pressure corresponding to an operation amount,
A pressure detection unit that detects the control pilot pressure output from the operation pedal, a pressure sensor that outputs a signal corresponding to the control pilot pressure detected by the pressure detection unit, and a signal output from the indicating device And a controller that outputs a control signal based on a signal output from the pressure sensor,
The hydraulic drive device for a construction machine, wherein the switching valve device comprises an electromagnetic switching valve that is switched according to the control signal output from the controller.

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