JP2018044326A - Hydraulic drive unit for construction equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic drive unit for construction equipment, which is installed with a flow rate changeover device for attachments, which is superior in fit and versatility, highly reliable, capable of easily adjusting flow rate, applicable regardless the types of hydraulic circuits to be fit in, and furthermore improved in energy saving.SOLUTION: A maximum-flow cut-valve device 40 of a hydraulic drive unit for construction equipment in this invention comprises: throttling changeover valves 81a and 81b, which are switched to opening positions C and E to open both oil passages 50 and 51 when an electric switch 54 is set at the large flow side, while are switched to a throttling positions D and F to throttle oil passages on the pressure-oil supply side of the oil passages 50 and 51 when the aforesaid electric switch is set at the small flow side; and operation changeover valves 45a and 45b, which hold the aforesaid throttling changeover valves at the opening positions C and E, and by-bath valves 42a and 42b at the closed position when the electric switch 54 is set at the large flow side, while cancel the opened position of the aforesaid throttling changeover valves and the closed position of the aforesaid by-path valves when the aforesaid electric switch is set at the small flow side.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydraulic drive device for a construction machine, and in particular, an attachment flow rate switching valve capable of switching a flow rate of pressure oil for driving an attachment actuator mounted on a construction machine such as a hydraulic excavator according to the type of attachment. The present invention relates to a hydraulic drive device for a construction machine including the device.

  In a hydraulic excavator composed of an upper swing body and a lower traveling body, there are a number of hydraulic cylinders for rotating booms, arms, buckets, etc. constituting the working machine, and traveling motors for driving left and right crawler tracks. In general, two variable displacement hydraulic pumps are mounted to drive each actuator freely. In addition, a crusher, a hydraulic breaker, or the like may be attached as an attachment instead of a bucket that is normally attached as a working machine, and a crushing operation such as a structure or a rock mass may be performed. These attachments have different required flow rates because the hydraulic equipment used for each attachment is different. For example, when driving the crusher, a flow rate for two pumps is required, and when driving a hydraulic breaker, a flow rate for one pump may be used.

  On the other hand, each of the above attachments is often used by exchanging the attachment whenever necessary using one hydraulic excavator. Therefore, the hydraulic excavator is required to easily switch the flow rate supplied to the attachment so that it can be immediately applied to the attached attachment.

  In response to such a request, there is a technique described in Patent Document 1.

  In the technique described in Patent Document 1, in an attachment flow switching device for a construction machine disposed between an attachment control valve and an attachment actuator, the attachment actuator is an actuator that requires a large flow rate or a small flow rate. Depending on the required actuator, it is arranged between the operation means operated on either the large flow side or the small flow side, and between the attachment control valve and the attachment actuator, and the attachment actuator is operated by operating the operation means. The maximum flow cut valve device that switches the flow rate of the pressure oil supplied to the large flow rate and the small flow rate, and the maximum flow cut valve device supplies the flow rate of the pressure oil output from the attachment control valve to the attachment actuator. The oil path to be supplied and the maximum flow rate of pressurized oil flowing through this oil path And a valve switching means for disabling the function of the valve means when the operating means is operated to the large flow rate side and for enabling the function of the valve means when operated to the small flow rate side. The valve means has a throttle disposed in the oil passage and a spring that operates in the closing direction. When the differential pressure across the throttle is below a set value determined by the spring, the valve means is closed by the spring force, and the differential pressure across the throttle is It has a bypass valve that opens when the set value is exceeded and bypasses the pressure oil in the oil passage to the return circuit, and the operation switching means keeps the bypass valve closed when operated to the large flow rate side, When operated to the side, the closed state of the bypass valve is released.

Japanese Patent No. 4215164

  In the technique described in Patent Document 1, since the maximum flow cut valve device is arranged between the attachment control valve and the attachment actuator, the arrangement configuration is simple, easy to install, and excellent in versatility. . Moreover, since the hydraulic circuit configuration is simplified, the reliability of the hydraulic circuit is high, and the flow rate can be adjusted before (in advance) the maximum flow rate cut-off valve device is incorporated into the machine. Since the maximum flow cut-off valve device is arranged between the attachment control valve and the attachment actuator, it can be used regardless of the type of hydraulic circuit to be mounted.

  However, in the technique described in Patent Document 1, when the electrical switch is operated to the large flow rate side, the bypass valve is not operated to the open position using the differential pressure before and after the throttle, but the large amount is set via the throttle. Pressure oil is supplied to and discharged from an actuator that requires a flow rate. As a result, when driving an actuator that requires a large flow rate, the pump load increases due to the pressure loss caused by the throttle, and the energy saving performance is impaired.

  The object of the present invention has been made in view of the above-mentioned problems, and the object of the present invention is to make it easy to mount, excellent in versatility, highly reliable, easy to adjust the flow rate, and to select the type of hydraulic circuit to be mounted. The present invention is to provide a hydraulic drive device for a construction machine that can be used regardless of the condition and further includes an attachment flow rate switching device with improved energy saving performance.

  In order to achieve the above object, the present invention provides a hydraulic pump, an attachment control valve to which discharge oil of the hydraulic pump is supplied, an attachment actuator controlled by the attachment control valve, and the attachment actuator. According to whether the first actuator requiring a large flow rate or the second actuator requiring a small flow rate is operated on either the large flow rate side or the small flow rate side, the attachment control valve, and the attachment A maximum flow rate cut-off valve device that is disposed in first and second actuator lines that connect to the actuator for switching, and that switches the flow rate of pressure oil supplied to the attachment actuator by operating the operating device between a large flow rate and a small flow rate; In the hydraulic drive device for a construction machine equipped with The valve device is connected to the first and second actuator lines, respectively, and first and second oil passages on the pressure oil supply side or pressure oil discharge side according to the switching direction of the attachment control valve, and the first An open position that is disposed in the first and second oil passages and opens both the first and second oil passages; and a throttling position that restricts at least the oil passage on the pressure oil supply side of the first and second oil passages; A throttle switching valve device that can be switched between the first oil passage side and the first oil passage side in the throttle switching valve device when the first oil passage is on the pressure oil supply side. Is kept in the closed position by the force of the first spring when the first spring is less than the set value, the differential pressure on the first oil passage side in the throttle switching valve device exceeds the set value of the first spring And open a part of the pressure oil in the first oil passage to the second oil passage. And a second spring that operates in the closing direction, and when the second oil passage is on the pressure oil supply side, the front-rear differential pressure on the second oil passage side in the throttle switching valve device is When it is less than the set value of 2 springs, it is held in the closed position by the force of the second spring, and opens when the front-rear differential pressure on the second oil passage in the throttle switching valve device exceeds the set value of the second spring. A second bypass valve for bypassing part of the pressure oil in the second oil passage to the first oil passage; and when the operation device is operated to a large flow rate side, the throttle switching valve device is set to an open position, When the first and second bypass valves are held in the closed positions and the operating device is operated to the small flow rate side, the throttling switching of the oil passage that is at least the pressure oil supply side of the first and second oil passages Hold the valve device in the throttle position, and release the closed position of the first and second bypass valves. And an operation switching device.

  In the present invention configured as described above, the maximum flow rate cut valve device is arranged between the attachment control valve and the attachment actuator, as in the technique of Patent Document 1, so that the arrangement configuration is simple and mounted. Is easy and versatile. In addition, since the hydraulic circuit configuration is simplified, the reliability of the hydraulic circuit is high and the flow rate can be adjusted before the maximum flow rate cut-off valve device is installed in the machine (in advance). Since the maximum flow cut-off valve device is arranged between the attachment control valve and the attachment actuator, it can be used regardless of the type of hydraulic circuit to be mounted.

  In the present invention, the throttle that can be switched between an open position that opens both the first and second oil passages and a throttle position that restricts at least the oil passage on the pressure oil supply side of the first and second oil passages. Since the switching valve device is provided in the maximum flow cut valve device and the throttle switching valve device is held in the open position when the operating device is operated to the large flow rate side, the operating device is operated to the large flow rate side. When both the first and second oil passages are opened and the attachment control valve and the actuator for attachment that require a large flow rate are connected without a restriction, the actuator for driving the attachment actuator Energy loss can be reduced.

  According to the present invention, the attachment is easy to mount, excellent in versatility, highly reliable, easy to adjust the flow rate, can be applied regardless of the type of hydraulic circuit to be mounted, and further improves energy saving. It is possible to provide a hydraulic drive device for a construction machine provided with a flow rate switching device.

1 is a hydraulic circuit diagram illustrating a hydraulic drive device for a construction machine according to a first embodiment of the present invention. It is a hydraulic circuit diagram which shows the hydraulic drive apparatus of the construction machine which concerns on 2nd Example of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the member or element which has the same effect | action or function, and the overlapping description is abbreviate | omitted suitably.

  FIG. 1 is a hydraulic circuit diagram showing a first embodiment in which the present invention is applied to a hydraulic drive device of a hydraulic excavator.

  In FIG. 1, flow control valves 2 and 3 for driving actuators 60 (or 61) and 62 are connected to hydraulic pumps 1 and 5 as main pumps, respectively. The flow rate control valve 2 includes a spool that can pass the total flow rate of the main pumps 1 and 5, and is disposed in a junction circuit 11 of the main circuit 9 of the main pump 1 and the main circuit 10 of the main pump 5. The flow control valve 3 is arranged in the main circuit 10 of the main pump 5. As a result, the oil discharged from the two main pumps 1 and 5 is supplied to the flow control valve 2, and only the oil discharged from the one main pump 5 is supplied to the flow control valve 3.

  Each of the flow control valves 2 and 3 is a 6-port 3-position center bypass switching valve. The actuator ports of the flow control valve 2 are actuator lines 21a and 21b, a maximum flow cut valve device 40 (described later), and an actuator line 22a. 22b is connected to the actuator 60 (or 61), and the actuator port of the flow control valve 3 is connected to the actuator 62 via the actuator lines 23 and 24. The flow control valves 2 and 3 are hydraulic pilot switching type, and pilot pressure receiving portions 2a and 2b and 3a and 3b are provided at both ends thereof.

  The actuators 60 and 61 are attachment actuators. For example, the actuator 60 is for a crusher, and the actuator 61 is for a breaker. The crusher and breaker can be exchanged as work implement attachments. The work machine attachment is attached to the tip of the work machine of the hydraulic excavator instead of the bucket. The crusher actuator 60 is an actuator that requires a large flow rate (for example, two pumps), and the breaker actuator 61 is an actuator that requires a smaller flow rate (for example, one pump).

  The actuator 62 is for an arm of a hydraulic excavator, for example.

  The main circuit 10 and the junction circuit 11 are also provided with flow control valves that drive actuators such as booms, swivels, and traveling of a hydraulic excavator, for example, but these are omitted.

  A pilot valve 14 that is operated by an attachment operation pedal 13 is provided. The pilot valve 14 generates an operation pilot pressure corresponding to the operation direction and the operation amount of the pedal 13 using the discharge pressure of the pilot pump 12 as a source pressure. The operation pilot pressure is sent to the pilot pressure receiving portions 2a and 2b at both ends of the flow control valve 2 via the pilot circuit 15 or 16. The discharge pressure of the pilot pump 12 is limited by the relief valve 17.

  The attachment flow rate switching device 100 is provided in the hydraulic drive device configured as described above. The attachment flow switching device 100 is operated according to whether the attachment actuator mounted on the hydraulic excavator is a crusher actuator 60 that requires a large flow rate or a breaker actuator 61 that requires a small flow rate. Arranged on actuator lines 21a, 21b and 22a, 22b that connect the electrical switch 54, the flow control valve 2 for attachment, and the actuator 60 (or 61) for attachment, and the actuator 60 ( Or the maximum flow cut valve device 40 which switches the flow volume of the pressure oil supplied to 61) to a large flow volume and a small flow volume is provided.

  The maximum flow cut valve device 40 is connected to the actuator lines 21a, 21b and 22a, 22b, respectively, and according to the switching direction of the flow control valve 2, oil passages 50, 51 on the pressure oil supply side or pressure oil discharge side, The throttle switching valve device 80 having throttle switching valves 81a and 81b disposed in the oil passages 50 and 51, the bypass lines 52 and 53 connecting the oil passage 50 and the oil passage 51, and the bypass lines 52 and 53, respectively. The bypass valve 42a, 42b, the operation switching valve 45a for operating the bypass valve 42a, 42b, and the operation switching valve 45b for operating the throttle switching valve device 80. The operation switching valves 45a, 45b are operated by an electric switch 54. Is done.

  The throttle switching valve 81a is disposed in the oil passage 50 and can be switched between the open position C and the throttle position D, and the operation pilot pressure (flow rate for attachment) generated in the pilot circuit 15 via the pressure signal lines 15a and 15b. An operation pilot pressure for switching the control valve 2 so that pressure oil is supplied to the actuator lines 21a and 22a) includes a pressure-receiving portion 83a that operates in the throttle direction and a spring 82a that operates in the opening direction. When the pilot pressure is equal to or lower than the tank pressure, it is held at the open position C by the force of the spring 82a, and when the operation pilot pressure becomes higher than the tank pressure, it switches to the throttle position D.

  The throttle switching valve 81b is disposed in the oil passage 51 and can be switched between the open position E and the throttle position F, and the operation pilot pressure (flow rate for attachment) generated in the pilot circuit 16 via the pressure signal lines 16a and 16b. An operation pilot pressure that switches the control valve 2 so that pressure oil is supplied to the actuator lines 21b and 22b) is provided with a pressure receiving portion 83b that operates in the throttle direction and a spring 82b that operates in the opening direction. When the pilot pressure is equal to or lower than the tank pressure, it is held at the open position E by the force of the spring 82b, and when the operation pilot pressure becomes larger than the tank pressure, it switches to the throttle position F.

  The bypass line 52 connects the upstream side of the throttle switching valve 81a when the oil path 50 is on the pressure oil supply side and the downstream side of the throttle switching valve 81b of the oil path 51. The upstream side of the throttle switching valve 81b at the pressure oil supply side and the downstream side of the throttle switching valve 81a in the oil passage 50 are connected.

  The bypass valves 42a and 42b are switching valves that operate between a closed position and an open position, and the bypass valves 42a and 42b include springs 43 and 44 that operate in the closing direction. The springs 43 and 44 are variable springs that can adjust a preset force (a set value of the spring strength). For example, the spring strength can be changed by inserting and removing a screw.

  The bypass valves 42a and 42b have pressure-receiving portions 71a and 71b that operate in the opening direction and pressure-receiving portions 72a and 72b that operate in the closing direction, respectively. The pressure-receiving portions 71a of the bypass valve 42a are connected via pressure signal lines 46a and 46b. Thus, the pressure on the upstream side of the throttle switching valve 81a is guided as a signal pressure, and the pressure on the downstream side of the throttle switching valve 81a is guided as a signal pressure to the pressure receiving portion 72a of the bypass valve 42a via the pressure signal line 46c. The pressure upstream of the throttle switching valve 81b is guided to the pressure receiving part 71b of the valve 42b via the pressure signal lines 47a and 47b, and the pressure receiving line 72c of the bypass valve 42b is throttled via the pressure signal line 47c. The pressure on the downstream side of the switching valve 81b is guided as a signal pressure.

  That is, when the oil passage 50 is on the pressure oil supply side, the differential pressure across the throttle switching valve 81a acts in the valve opening direction on the pressure receiving portions 71a and 72a of the bypass valve 42a, and the pressure receiving portions 71b and 71b of the bypass valve 42b. In 72b, when the oil passage 51 is on the pressure oil supply side, the differential pressure across the throttle switching valve 81b acts in the valve opening direction.

  The operation switching valve 45a is disposed in pressure signal lines 46a, 46b and 47a, 47b, respectively, which lead the pressure upstream of the throttle switching valves 81a, 81b to the pressure receiving portions 71a, 71b of the bypass valves 42a, 42b as signal pressures. A closed position A where the signal lines 46a and 46b are non-conductive and the pressure signal lines 47a and 47b are non-conductive, and an open position B where the pressure signal lines 46a and 46b are conductive and the pressure signal lines 47a and 47b are conductive. Can be switched between. Further, the operation switching valve 45a has a solenoid driving unit 45c. When the electric switch 54 is OFF (when operated to a large flow rate side), the solenoid driving unit 45c is de-energized, and the operation switching valve 45a is in the closed position A. When the electric switch 54 is turned on (operated to the small flow rate side), the solenoid drive unit 45c is excited, the operation switching valve 45a is switched to the open position B, and the throttle switching valve 84 in the oil passages 50, 51 is switched. The upstream pressure acts on the pressure receiving portions 71a and 71b. When the electrical switch 54 is OFF, it is when the electrical switch 54 is operated to the large flow rate side, and when the electrical switch 54 is ON, it is when the electrical switch 54 is operated to the small flow rate side.

  As described above, the operation switching valve 45a holds the bypass valves 42a and 42b in the closed position when the electric switch 54 is operated to the large flow rate side, and the bypass valves 42a and 42b when the electric switch 54 is operated to the small flow rate side. Functions as an operation switching device for releasing the holding of the closed position.

  The operation switching valve 45b is an operation pilot pressure (operation pilot pressure generated in the pilot circuit 15) for switching the attachment flow control valve 2 so that pressure oil is supplied to the actuator lines 21a and 22a, and an attachment flow control valve. 2 is a pressure signal line that guides an operation pilot pressure (operation pilot pressure generated in the pilot circuit 16) to the pressure receiving portions 83a and 83b of the throttle switching valves 81a and 81b. 15a, 15b and 16a, 16b, a closed position G in which the pressure signal lines 15a, 15b are non-conductive and the pressure signal lines 16a, 16b are non-conductive, and the pressure signal lines 15a, 15b are conductive and pressure signals Cut between line 16a, 16b and open position H that conducts Possible it is. Further, the operation switching valve 45b has a solenoid driving unit 45d that operates in the opening direction, and when the electric switch 54 is OFF (when operated to the large flow rate side), the solenoid driving unit 45d is de-energized, and the operation switching valve 45b is operated. 45b is in the closed position G, and when the electric switch 54 is turned on (operated to the small flow rate side), the solenoid drive unit 45d is excited, the operation switching valve 45b is switched to the open position H, and the pilot circuits 15, 16 The operating pilot pressure generated in step 1 acts on the pressure receiving portions 71a and 71b.

  Thus, the operation switching valve 45b holds the throttle switching valves 81a and 81b at the open positions C and E when the electric switch 54 is operated to the large flow rate side, and the throttle when the electric switch 54 is operated to the small flow rate side. It functions as an operation switching device that releases the holding of the open positions C and E of the switching valves 81a and 81b.

  Next, the function and operation of the attachment flow switching device 100 including the maximum flow cut valve device 40 will be described.

  For example, when a crusher is attached as a work machine attachment of a hydraulic excavator, that is, when the actuator of the attached work machine attachment is an actuator 60 that requires a large flow rate, the electric switch 54 is kept OFF (to the large flow rate side). In operation), the solenoid drive portions 45c and 45d of the operation switching valves 45a and 45b are de-energized. In this case, the operation switching valves 45a and 45b are in the closed positions A and G, respectively, the pressure signal lines 46a and 46b are turned off, the pressure signal lines 47a and 47b are turned off, and the pressure signal lines 15a and 15b are turned off. The pressure signal lines 16a and 16b are made non-conductive. As a result, the throttle switching valves 81a and 81b are in the open positions C and E, respectively, and the bypass valves 42a and 42b are in the illustrated closed positions.

  When the flow control valve 2 is operated by operating the pedal 13 for operating the attachment in such a state, the bypass valves 42a and 42b are in the illustrated closed position as described above. The total flow rate of the flow rate that has passed through the flow rate control valve 2 is supplied to the actuator 60 via the actuator line 21a or 21b, the oil passage 50 or 51 of the maximum flow rate cut valve device 40, and the throttle switching valve 81a or 81b. The That is, in this case, the pressure oil from the main pumps 1 and 5 merges and is supplied to the actuator 60 as in the conventional case.

  For example, when a breaker is attached as a work machine attachment of a hydraulic excavator, that is, when the actuator of the attached work machine attachment is an actuator 61 that requires a small flow rate, the worker turns on the electric switch 54 (small flow rate side). To excite the solenoid drive portions 45c and 45d of the operation switching valves 45a and 45b. In this case, the operation switching valves 45a and 45b are respectively switched to the open positions B and H, the pressure signal lines 46a and 46b are conducted, the pressure signal lines 47a and 47b are conducted, and the pressure signal lines 15a and 15b are conducted. The pressure signal lines 16a and 16b are conducted. As a result, the throttle switching valves 81a and 81b can be switched by the pressure generated in the pilot circuits 15 and 16 according to the operation of the pedal 13, and the pressure receiving portions 71a and 72a and 71b and 72b of the bypass valves 42a and 42b are switched. The differential pressure across the throttle switching valves 81a and 81b acts.

  When the flow control valve 2 is operated by operating the attachment pedal 13 in such a state, when the actuator line 21a is on the pressure oil supply side, the operating pilot pressure generated in the pilot circuit 15 is the pressure signal. Acting on the pressure receiving portion 83a of the throttle switching valve 81a via the line 15a, the operation switching valve 45b and the pressure signal line 15b, the throttle switching valve 81a switches to the throttle position D, and the pressure receiving portions 71a and 72a of the bypass valve 42a The differential pressure across the throttle switching valve 81a acts. The bypass valve 42a is held in the closed position by the force of the spring 43 when the differential pressure across the throttle switching valve 81a is less than or equal to the set value of the spring 43, and the differential pressure across the throttle switching valve 81a exceeds the preset value of the spring 43. Then, a part (excess flow rate) of the pressure oil in the oil passage 50 on the pressure oil supply side is bypassed to the oil passage 51 on the pressure oil discharge side. At this time, since the pilot pilot pressure is not generated in the pilot circuit 16, the throttle switching valve 81b is held at the open position E.

  The same applies to the case where the actuator line 21b is on the pressure oil supply side, and the operation pilot pressure generated in the pilot circuit 16 is supplied to the throttle switching valve 81b via the pressure signal line 16a, the operation switching valve 45b and the pressure signal line 16b. Acting on the pressure receiving portion 83b, the throttle switching valve 81b is switched to the throttle position F, and the differential pressure across the throttle switching valve 81b acts on the pressure receiving portions 71b and 72b of the bypass valve 42b. The bypass valve 42b is held in the closed position by the force of the spring 44 when the differential pressure across the throttle switching valve 81b is less than or equal to the set value of the spring 44, and the differential pressure across the throttle switching valve 81b exceeds the set value of the spring 44. Then, a part (excess flow) of the pressure oil in the oil passage 51 on the pressure oil supply side is bypassed to the oil passage 50 on the pressure oil discharge side. At this time, since the operation pilot pressure is not generated in the pilot circuit 15, the throttle switching valve 81a is held at the open position C.

The throttle switching valves 81a and 81b are throttled by switching to the throttle positions D and F, respectively. The opening areas of the throttle switching valves 81a and 81b are Aa and Ab, respectively, and the differential pressure across the throttle switching valves 81a and 81b is ΔPa, respectively. , ΔPb, and passing flow rates of the throttle switching valves 81a, 81b as Qa, Qb, respectively,
Qa = constant × Aa × √ΔPa
Qb = constant × Ab × √ΔPb
Therefore, the flow rate of Qa or more than Qb does not flow through the actuator line 21a or 21b, the oil passage 50 or 51, and the actuator line 22a or 22b. That is, only the flow rates Qa and Qb are supplied to the actuator 61 from the main pumps 1 and 5.

  According to the present embodiment, the following effects can be obtained.

  (1) The flow rate switching accompanying the replacement of the crusher actuator 60 that requires a large flow rate and the breaker actuator 61 that requires a small flow rate, which are operated by the same flow control valve 2, is an operating device. This can be done very easily by operating the electrical switch 54.

  (2) Since the maximum flow cut valve device 40 is arranged between the attachment flow control valve 2 and the attachment actuator 60 or 61, the arrangement configuration is simple and easy to wear, and retrofit Is easy and versatile.

  (3) Since the hydraulic circuit configuration is simplified, the reliability of the hydraulic circuit is high, and inspection and maintenance man-hours and manufacturing costs are reduced.

  (4) Since the maximum flow cut valve device 40 includes the bypass valves 42a and 42b, the flow rate can be arbitrarily adjusted by adjusting the strength of the springs 43 and 44.

  (5) Since the flow rate adjustment can be performed before (in advance) the maximum flow rate cut valve device 40 is incorporated in the machine, the flow rate adjustment operation is easy. Further, since the flow rate can be finely adjusted in advance, it is excellent in versatility.

  (6) Since the bypass valves 42a and 42b are switched between a large flow rate and a small flow rate, the secular change due to mechanical contact wear is small, and the set flow rate hardly changes.

  (7) Since the maximum flow cut valve device 40 is disposed between the attachment flow control valve 2 and the attachment actuator 60 or 61, it can be used regardless of the type of hydraulic circuit to be mounted. Both open center hydraulic circuits using center bypass type control valves, which are more commonly used as hydraulic circuits for construction machinery, and load sensing hydraulic circuits using control valves with pressure compensation valves can be used. But it is versatile.

  (8) When the electric switch 54 is operated to the large flow rate side, the throttle switching valves 81a and 81b are held at the open positions C and E, whereby both the oil passages 50 and 51 are opened, and the attachment Since the flow rate control valve 2 and the attachment actuator 60 that requires a large flow rate are connected without a throttle, energy loss when driving the attachment actuator 60 can be reduced.

  (9) When the electric switch 54 is operated to the small flow rate side, the oil passage on the pressure oil discharge side of the oil passages 50 and 51 is opened, and generation of unnecessary back pressure is suppressed. It is possible to reduce energy loss when driving the required actuator 61 for attachment.

  FIG. 2 is a hydraulic circuit diagram showing a second embodiment in which the present invention is applied to a hydraulic drive device of a hydraulic excavator. Differences from the first embodiment (shown in FIG. 1) will be described below.

  In FIG. 2, the maximum flow cut valve device 40A in this embodiment is disposed in the oil passages 50 and 51 in place of the throttle switching valve device 80 having the throttle switching valves 81a and 81b disposed in the oil passages 50 and 51, respectively. A throttle switching valve device 80A having the throttle switching valve 84 is provided. Thus, by configuring the throttle switching valve device 80A with the single throttle switching valve 84, the maximum flow cut valve device 40A can be simplified as compared with the first embodiment.

  The throttle switching valve 84 has a spring 85 that operates in the opening direction, and can be switched between an open position I that opens both of the oil passages 50 and 51 and a throttle position J on the right side of the drawing that throttles both of the oil passages 50 and 51. is there. In addition, a solenoid driving unit 86 is provided for the throttle switching valve 84, and when the electric switch 54 is OFF (when operated to the large flow rate side), the solenoid driving unit 86 is not excited, and the throttle switching is performed. The valve 84 is in the open position I, and when the electric switch 54 is turned on (operated to the small flow rate side), the solenoid drive unit 86 is excited and the throttle switching valve 84 is switched to the throttle position J.

  As described above, the solenoid drive unit 86 holds the throttle switching valve 84 at the open position I when the electric switch 54 is operated to the large flow rate side, and the throttle switching valve 84 of the throttle switching valve 84 when the electric switch 54 is operated to the small flow rate side. It functions as an operation switching device that releases the holding of the open position I.

  The pressure receiving portion 71a of the bypass valve 42a is guided to the pressure upstream of the throttle switching valve 84 in the oil passage 50 as a signal pressure via the pressure signal lines 46a and 46b. The pressure signal line is connected to the pressure receiving portion 72a of the bypass valve 42a. The pressure on the downstream side of the throttle switching valve 84 in the oil passage 50 is guided as a signal pressure through 46c, and the throttle switching valve 84 in the oil passage 51 is connected to the pressure receiving portion 71b of the bypass valve 42b via the pressure signal lines 47a and 47b. The pressure on the upstream side of the throttle valve 84 in the oil passage 51 is guided to the pressure receiving portion 72b of the bypass valve 42b as the signal pressure via the pressure signal line 47c.

  The operation switching valve 45a is connected to pressure signal lines 46a, 46b and 47a, 47b respectively leading to pressure receiving portions 71a, 71b of the bypass valves 42a, 42b using the pressure upstream of the throttle switching valve 84 in the oil passages 50, 51 as a signal pressure. Has been placed. When the electric switch 54 is turned on (operated to the small flow rate side), the solenoid drive unit 45c is excited, the operation switching valve 45a is switched to the open position B, and the upstream side of the throttle switching valve 84 in the oil passages 50 and 51. Acts on the pressure receiving portions 71a and 71b, respectively.

  Next, the function and operation of the attachment flow switching device 100A provided with the maximum flow cut valve device 40A in the present embodiment will be described focusing on differences from the first embodiment.

  In the first embodiment, when the electric switch 54 is operated to the large flow rate side, the solenoid drive unit 45d of the operation switching valve 45b is de-energized, the operation switching valve 45b is held at the closed position G, and the pilot circuit 15 , 16 does not act on the pressure receiving portions 83a, 83b of the throttle switching valves 81a, 81b, and the throttle switching valves 81a, 81b are held at the open positions C, E, respectively. Both 51 are opened.

  On the other hand, in this embodiment, when the electric switch 54 is operated to the large flow rate side, the solenoid drive unit 86 provided for the throttle switching valve 84 is de-energized, and the throttle switching valve 84 is in the open position. By being held at I, both the oil passages 50 and 51 are opened.

  Further, in the first embodiment, when the electric switch 54 is operated to the small flow rate side, the solenoid drive unit 45d of the operation switching valve 45b is excited, the operation switching valve 45b is switched to the open position H, and the pilot circuit The operating pilot pressure generated at 15 and 16 acts on the pressure receiving portions of the throttle switching valves 81a and 81b on 83a and 83b, respectively, and the throttle switching valve 81a or 81b disposed in the oil passage 50 or 51 on the pressure oil supply side While switching to the throttle position D or F, the throttle switching valve 81a or 81b disposed in the oil passage 50 or 51 on the pressure oil discharge side is held at the open position C or E, so that it becomes the pressure oil supply side. The oil passage 50 or 51 is throttled, while the oil passage 51 or 50 on the pressure oil discharge side is opened.

  On the other hand, in this embodiment, when the electric switch 54 is operated to the small flow rate side, the solenoid drive unit 86 provided for the throttle switching valve 84 is excited, and the throttle switching valve 84 is set to the throttle position J. Is switched to both the oil passage 50 or 51 on the pressure oil supply side and the oil passage 51 or 50 on the pressure oil discharge side.

  According to this embodiment, the effects (1) to (7) of the first embodiment can be obtained, and the throttle switching valve 84 is held in the open position I when the electric switch 54 is operated to the large flow rate side. As a result, both of the oil passages 50 and 51 are opened, and the attachment flow control valve 2 and the attachment actuator 60 that requires a large flow rate are connected without passing through the throttle. It becomes possible to reduce the energy loss when driving.

  As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to an above-described Example, Various modifications are included.

  For example, in the above-described embodiment, the configuration in which the discharge oils of the two hydraulic pumps 1 and 5 are merged and supplied to the flow control valve 2 is shown. However, the discharge oil of three or more hydraulic pumps is merged to control the flow rate. It is good also as a structure supplied to the valve 2.

  In the second embodiment (shown in FIG. 2), the throttle switching valve 84 is provided with the solenoid drive unit 86. However, the throttle switching valve 84 is a hydraulic switching valve, and the hydraulic switching valve operates in the throttle direction. It is good also as a structure which guide | induces the primary pressure of the pilot pump 12 to a pressure receiving part via an electromagnetic pressure reducing valve. In this case, the solenoid driving portion of the electromagnetic switching valve is provided for the throttle switching valve 84 in the same manner as the solenoid driving portion 86 provided for the throttle switching valve 84, and when the electric switch 54 is operated to the large flow rate side. When the throttle switching valve 84 is held in the open position I and the electric switch 54 is operated to the small flow rate side, it functions as an operation switching device that releases the holding of the open position I of the throttle switching valve 84.

  The above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. It is also possible to add a part of the configuration of another embodiment to the configuration of a certain embodiment, and delete a part of the configuration of a certain embodiment or replace it with a part of another embodiment. Is possible.

  DESCRIPTION OF SYMBOLS 1,5 ... Main pump, 2 ... Flow control valve (control valve for attachment), 3 ... Flow control valve, 2a, 2b, 3a, 3b ... Pilot pressure receiving part, 9, 10 ... Main circuit, 11 ... Merging circuit, 12 ... Pilot pump, 13 ... Pedal, 14 ... Pilot valve, 15, 16 ... Pilot circuit, 17 ... Relief valve, 21a, 21b, 22a, 22b ... Actuator line, 40, 40A ... Maximum flow cut valve device, 41a, 41b ... Throttle valve, 42a, 42b ... Bypass valve, 43, 44 ... Spring, 45a, 45b ... Operation switching valve (operation switching device), 45c, 45d ... Solenoid drive, 46a, 46b, 46c, 47a, 47b, 47c ... Pressure Signal line, 50, 51 ... Oil passage, 52, 53 ... Bypass line, 54 ... Electric switch (operating device), 60 ... Actuator for crusher 61 ... Actuator for breaker, 62 ... Actuator, 71a, 71b, 72a, 72b ... Pressure receiving part, 80, 80A ... Throttle switching valve device, 81a, 81b ... Throttle switching valve, 82a, 82b ... Spring, 83a, 83b DESCRIPTION OF SYMBOLS ... Pressure receiving part, 84 ... Restriction switching valve, 85 ... Spring, 86 ... Solenoid drive part (operation switching device), 100, 100A ... Flow rate switching device for attachment.

Claims (3)

A hydraulic pump;
An attachment control valve to which the oil discharged from the hydraulic pump is supplied;
An attachment actuator controlled by the attachment control valve;
An operating device operated on either the large flow rate side or the small flow rate side according to whether the attachment actuator is a first actuator requiring a large flow rate or a second actuator requiring a small flow rate;
Disposed in first and second actuator lines connecting the attachment control valve and the attachment actuator, the flow rate of the pressure oil supplied to the attachment actuator by operation of the operation device is a large flow rate and a small flow rate. In a hydraulic drive system for construction machinery with a maximum flow cut valve device that switches to
The maximum flow cut valve device is
First and second oil passages connected to the first and second actuator lines, respectively, on the pressure oil supply side or pressure oil discharge side according to the switching direction of the attachment control valve;
A throttle that is arranged in the first and second oil passages and that restricts an open position that opens both the first and second oil passages and an oil passage that is at least a pressure oil supply side of the first and second oil passages. A throttle switching valve device switchable to a position;
When the first oil passage is on the pressure oil supply side, the differential pressure on the first oil passage side in the throttle switching valve device is less than or equal to the set value of the first spring. Is held in the closed position by the force of the first spring, and opens when the front-rear differential pressure on the first oil passage side in the throttle switching valve device exceeds the set value of the first spring. A first bypass valve that bypasses part of the oil to the second oil passage;
When the second oil passage is on the pressure oil supply side, the differential pressure on the second oil passage side in the throttle switching valve device is less than or equal to the set value of the second spring. Is held in the closed position by the force of the second spring, and opens when the front-rear differential pressure on the second oil passage side in the throttle switching valve device exceeds the set value of the second spring. A second bypass valve that bypasses part of the oil to the first oil passage;
When the operating device is operated to the large flow rate side, the throttle switching valve device is held in the open position, the first and second bypass valves are held in the closed position, and the operating device is operated to the small flow rate side. Is an operation of holding the throttle switching valve device of the oil passage on the pressure oil supply side at least in the first and second oil passages in the throttle position and releasing the holding of the closed positions of the first and second bypass valves. A hydraulic drive device for a construction machine, comprising: a switching device. The hydraulic drive device for a construction machine according to claim 1,
The throttle switching valve device is disposed in the first oil passage, and is switchable between an open position and a throttle position, and includes a first pressure receiving portion that operates in the throttle direction and a third spring that operates in the open direction. A second throttle switch disposed in the second oil passage, which is switchable between an open position and a throttle position, and which is provided with a second pressure receiving part that operates in the throttle direction and a fourth spring that operates in the open direction. And a valve
The first bypass valve has a third pressure receiving portion that operates in an opening direction and a fourth pressure receiving portion that operates in a closing direction, and a pressure downstream of the first throttle switching valve is a signal in the fourth pressure receiving portion. Led as pressure,
The second bypass valve has a fifth pressure receiving portion that operates in the opening direction and a sixth pressure receiving portion that operates in the closing direction, and the pressure on the downstream side of the second throttle switching valve is a signal in the sixth pressure receiving portion. Led as pressure,
The operation switching device includes third and fourth oils respectively leading to the third and fifth pressure receiving portions of the first and second bypass valves using the upstream pressure of the first and second throttle switching valves as a signal pressure. When the operating device is operated on the large flow rate side, it is in the closed position, and when the operating device is operated on the small flow rate side, it switches to the open position, and the first and second oil paths Pressure oil is applied to the first actuator line through the first operation switching valve that causes the pressure on the upstream side of the first and second throttle switching valves to act on the third and fifth pressure receiving portions, respectively, and the attachment control valve. The first attachment operation pilot pressure that switches to be supplied and the second attachment operation pilot pressure that switches the attachment control valve to supply pressure oil to the second actuator line Arranged in the fifth and sixth oil passages respectively leading to the first pressure receiving portion of the first throttle switching valve and the second pressure receiving portion of the second throttle switching valve, and when the operating device is operated at a large flow rate, it is in the closed position. And a second operation switching valve that switches to an open position when the operation device is operated to the small flow rate side and causes the first and second attachment operation pilot pressures to act on the first and second pressure receiving portions, respectively. A hydraulic drive device for a construction machine, comprising: The hydraulic drive device for a construction machine according to claim 1,
The throttle switching valve device is disposed in the first and second oil passages, and an open position for opening both the first and second oil passages and a throttle position for restricting both the first and second oil passages. And a third throttle switching valve having a fifth spring that operates in the opening direction,
The first bypass valve includes a third pressure receiving portion that operates in an opening direction and a fourth pressure receiving portion that operates in a closing direction, and the fourth pressure receiving portion includes a third pressure switching valve in the first oil passage. The downstream pressure is guided as signal pressure,
The second bypass valve includes a fifth pressure receiving portion that operates in an opening direction and a sixth pressure receiving portion that operates in a closing direction, and the sixth pressure receiving portion includes a third pressure-reducing valve in the second oil passage. The downstream pressure is guided as signal pressure,
The operation switching device guides the pressure on the upstream side of the third throttle switching valve in the first and second oil passages as a signal pressure to the third and fifth pressure receiving portions of the first and second bypass valves, respectively. Arranged in the third and fourth oil passages, when the operating device is operated to the large flow rate side, it is in the closed position, and when the operating device is operated to the small flow rate side, it switches to the open position, A first operation switching valve for causing the pressure on the upstream side of the third throttle switching valve in the first and second oil passages to act on the third and fifth pressure receiving portions, respectively, and the third throttle switching valve; A hydraulic drive device for a construction machine, comprising: a solenoid drive unit that switches the third throttle switching valve to a throttle position when the operating device is operated to a large flow rate side.

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