JP2012237423A - Hydraulic control apparatus for working - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress cavitation in a meter-in flow fluid passage and hunting of the rotation speed of a hydraulic actuator and to suppress the change in speed of a hydraulic actuator according to the weight of load.SOLUTION: The hydraulic control apparatus includes: a meter-in flow control device 62 which controls the flow rate of the meter-in fluid passage 30; a meter-out orifice 71 disposed at a meter-out fluid passage 40; a meter-out flow control device 72 which controls the flow rate of the meter-out fluid passage 40 to keep the inlet-outlet pressure difference of the meter-out orifice 71 constant; a back pressure valve 81 for generating a set back pressure Pbk at an upstream side position; and a regeneration fluid passage 50 branched from the meter-out fluid passage 40 at a position upstream of the back pressure valve 81 and merged with the meter-in fluid passage 30. A meter-out flow rate Qmo controlled by the meter-out flow control device 72 is controlled so as to make the meter-out flow rate Qmo be greater than the meter-in flow rate Qmi controlled by the meter-in flow control device 62.

Description

  The present invention relates to a working hydraulic control device that controls the operation of a hydraulic actuator.

  For example, as described in Patent Document 1, there is a working hydraulic control device that drives a hydraulic actuator. In this working hydraulic control device, the hydraulic actuator may be driven so that the load moves in the direction of falling weight. Patent Document 1 describes a hydraulic circuit for a lowering operation that drives a hydraulic motor (hydraulic actuator) so that a suspended load (load) moves in the lowering direction.

  In this working hydraulic control device, cavitation may occur when the suspended load is lowered. More specifically, when the suspended load is lowered, the rotational speed of the hydraulic motor may increase due to the weight of the suspended load. Due to this acceleration, the absorption flow rate of the hydraulic motor may exceed the supply flow rate from the hydraulic pump to the hydraulic motor. In this case, the pressure (meter-in pressure) in the oil passage (meter-in oil passage) on the hydraulic oil supply side of the hydraulic motor may decrease, and cavitation may occur in the meter-in oil passage. The cavitation may cause the hydraulic motor to stall (no braking force is generated in the hydraulic motor) and the suspended load may fall.

  Technology to provide an external pilot-type counter balance valve (hereinafter simply referred to as “counter balance valve”) in the hydraulic oil discharge side (meter-out oil passage) of the hydraulic motor in order to suppress cavitation in the meter-in oil passage (Counterbalance valve 11 in FIG. 1 of Patent Document 1). More specifically, the counter balance valve introduces meter-in pressure as a pilot pressure, and a set pressure P1 is set by a spring or the like. The counter balance valve opens when the meter-in pressure becomes higher than the set pressure P1, and closes when the meter-in pressure becomes lower than the set pressure P1. When the valve opening is closed, the meter-out oil passage is throttled, a braking force is generated in the hydraulic motor, the hydraulic motor is decelerated, and the absorption flow rate of the hydraulic motor is suppressed. As described above, the meter-in pressure is controlled by the counter balance valve so as not to become the set pressure P1 or less. As a result, cavitation in the meter-in oil passage is suppressed.

  Patent Document 2 describes a regeneration circuit for returning hydraulic oil from a meter-out oil passage to a meter-in oil passage (details will be described later).

JP 2000-310201 A JP 10-2670007 A

FIG. 16 shows a conventional working hydraulic control device 701. The above-described external pilot type counter balance valve 784 employs an unstable control system in which the measurement point (on the meter-in oil passage 30) and the control point (on the meter-out oil passage 40) are different. As a result, the rotational speed of the hydraulic motor 13 is easily hunted.
More specifically, it is assumed that the operation lever 16 is operated from the neutral position to the lowering position at time T0. In response to this operation, the hydraulic oil supplied from the direction switching valve 20 to the hydraulic motor 13 increases, and the meter-in pressure in the meter-in oil passage 30 increases. The counter balance valve 784 that has detected this increase in pressure shifts from a closed state to an open state. However, the counter balance valve 784 has a control method in which the position differs between the meter-in pressure measurement point (on the meter-in oil passage 30) and the valve control point (on the meter-out oil passage 40), that is, co-location in terms of control theory. ) Has not been taken (inherently unstable control method). Since the measurement point and the control point are different, a difference is likely to occur between the change in meter-in pressure and the operation timing of the counter balance valve 784. Due to this deviation, the opening degree of the counter balance valve 784 repeatedly opens and closes as shown in FIG. 17A, and the meter-in pressure also vibrates as shown in FIG. 17B. As a result, the rotational speed of the hydraulic motor 13 (see FIG. 16) may vibrate (hunt).

  As shown in FIG. 16, there is a technique in which a throttle 786 is provided in a pilot line 785 of a counter balance valve 784 in order to suppress the above-described hunting problem. The throttle 786 gradually opens the counter balance valve 784 when the meter-in pressure increases (the valve response is moderated, and the valve is damped in the direction of operation from the closed state to the open state). (See FIG. 18 (a)).

  In the technique provided with the above-described throttle 786, a throttle resistance is generated by the counter balance valve 784 until the counter balance valve 784 reaches an appropriate valve opening A1. Therefore, as shown in FIG. 18B, there is a problem that unnecessary boost pressure (see the hatched portion in FIG. 18B) is generated in the meter-in oil passage 30 and fuel consumption is deteriorated.

  Patent Document 1 describes a technique in which a flow rate adjusting valve (see reference numeral 18 in FIG. 1 of Patent Document 1) is provided in order to suppress the above-described hunting problem. The flow rate adjusting valve controls the flow rate of the meter-in oil passage in a direction in which the differential pressure between the meter-in oil passage and the meter-out oil passage is reduced.

The technique described in Patent Document 1 has a problem that the operating speed (winding speed) of the hydraulic motor changes depending on the mass of the suspended load (load).
More specifically, generally, when the load is lowered by the working hydraulic control device, a holding pressure corresponding to the mass of the load is generated in the meter-out oil passage. This holding pressure is higher when the load is higher than when the load is light. In the technique described in Patent Document 1, the higher the holding pressure, the more the valve opening degree of the flow rate adjusting valve described above operates in the opening direction. When the valve opening degree of the flow rate adjusting valve is opened, the flow rate of the meter-in oil passage (meter-in flow rate) increases, and the operating speed of the hydraulic motor increases. That is, the lowering speed is greater in the heavy load than in the light load. Therefore, the operating speed of the hydraulic motor changes depending on the load regardless of the same lever operation amount, resulting in poor operability.

  Patent Document 2 describes a reproduction circuit (for example, FIG. 5 of Patent Document 2). This circuit includes a throttle provided in the meter-out oil passage and a regenerative oil passage communicating the upstream of the throttle with the meter-in oil passage. Then, the flow rate of the meter-out oil passage (meter-out flow rate) is returned to the meter-in oil passage through the regeneration oil passage, thereby increasing the speed of the hydraulic actuator (attachment).

  When the regeneration circuit described in Patent Document 2 is applied to a circuit (such as described in Patent Document 1) in which a suspended load is unwound by, for example, a hydraulic motor, the regeneration oil path increases as the weight of the suspended load increases. Flow rate (regeneration flow rate) increases. Thus, the heavier the suspended load, the higher the unwinding speed, and there is a problem that safety and operability are impaired. In the technique described in Patent Document 2, the minimum pressure in the meter-in oil passage is not compensated. Therefore, there is a problem that cavitation occurs in the meter-in oil passage, the hydraulic motor stalls, and the suspended load falls.

  Therefore, the present invention can suppress cavitation in the meter-in oil passage, can suppress hunting of the rotational speed of the hydraulic actuator, can suppress deterioration of responsiveness and fuel consumption for suppressing hunting, and An object of the present invention is to provide a working hydraulic control device capable of suppressing a change in speed of a hydraulic actuator in accordance with the weight of a load.

  The working hydraulic control device of the present invention includes a hydraulic pump, a hydraulic actuator that is driven by pressure oil supplied from the hydraulic pump to move a load, and an operation unit that operates an operating speed of the hydraulic actuator, The hydraulic actuator is driven so that the load moves in the direction of falling weight. This working hydraulic control device is provided in a meter-in flow rate control means for controlling the flow rate of the meter-in oil path of the hydraulic actuator and a meter-out oil path of the hydraulic actuator, and has an opening degree according to the operation amount of the operating means. A meter-out throttle that changes, a meter-out flow controller that detects the differential pressure before and after the meter-out throttle, and controls the flow rate of the meter-out oil passage so as to maintain the differential pressure across the meter at a constant set differential pressure, and the meter-out A back pressure valve provided downstream of the throttle and downstream of the meter-out flow controller for generating a set back pressure upstream of the valve, and branched from the meter-out oil passage upstream of the back pressure valve And a regenerated oil path that merges with the meter-in oil path, and a flow path that is provided in the regenerated oil path and flows from the meter-out oil path to the meter-in oil path And a check valve through a pressure oil only. The meter-in flow rate control means controls a meter-in flow rate upstream of the junction with the regenerated oil passage in the meter-in oil passage. The meter-out flow controller controls a meter-out flow rate upstream of a branch point with the regenerated oil passage in the meter-out oil passage. The meter-out flow rate is controlled to be larger than the meter-in flow rate.

  In the present invention, cavitation in the meter-in oil passage can be suppressed, hunting of the rotational speed of the hydraulic actuator can be suppressed, responsiveness deterioration and fuel consumption deterioration for suppressing hunting can be suppressed, and load It can suppress that the speed of a hydraulic actuator changes according to the weight of the.

1 is a hydraulic circuit diagram showing a working hydraulic control device of a first embodiment. FIG. 2 is a hydraulic circuit diagram when the working hydraulic control device shown in FIG. 1 is lowered. It is a graph which shows the relationship between the opening area of the meter-in stop 61 and the meter-out stop 71, and the lever operation amount. It is a graph which shows the relationship between meter-in flow rate, meter-out flow rate, and lever operation amount. 6 is a graph showing the relationship between the opening area of the bleed-off stop 21a and meter-in stop 61 shown in FIG. 1 and the lever operation amount. It is a graph which shows the relationship between meter-in pressure and time. It is a graph which shows the relationship between fuel consumption and time. FIG. 3 is a diagram corresponding to FIG. 1 of a second embodiment. It is a graph which shows the relationship between the opening area of the direction switching valve 20 and the meter-out valve 271 shown in FIG. 8, and a lever operation amount. It is FIG. 1 equivalent drawing of 3rd Embodiment and 6th Embodiment. It is a graph which shows the relationship between the setting back pressure of the back pressure valve 81 shown in FIG. 10, and meter-in pressure. FIG. 6 is a diagram corresponding to FIG. 1 of a fourth embodiment. It is a graph which shows the relationship between the secondary pressure of the electromagnetic pressure reducing valve 493 shown in FIG. It is a modification of the relationship shown in FIG. FIG. 10 is a view corresponding to FIG. 1 of a fifth embodiment. It is a hydraulic circuit diagram which shows the conventional hydraulic control apparatus for work. It is explanatory drawing of the hunting in the conventional working hydraulic control apparatus shown in FIG. FIG. 17 is an explanatory diagram of boost pressure and the like in the conventional working hydraulic control device shown in FIG. 16.

(First embodiment)
The working hydraulic control apparatus 1 according to the first embodiment will be described with reference to FIGS.

  The working hydraulic control device 1 is a device for driving a hydraulic motor 13 (hydraulic actuator) as shown in FIG. The working hydraulic control device 1 drives the hydraulic motor 13 so that the suspended load 15 (load) moves in the direction of falling its own weight (in the lowering direction), or the suspended load 15 moves in the direction opposite to the direction of falling its own weight. In this way, the hydraulic motor 13 is driven (in the winding direction). The work hydraulic control device 1 is provided in a work machine such as a crane. The working hydraulic control device 1 includes an engine 11 (power source), a hydraulic pump 12 driven by the engine 11, a hydraulic motor 13 driven by pressure oil supplied from the hydraulic pump 12, a hydraulic pump 12, and a hydraulic pressure A direction switching valve 20 provided between the motor 13, a remote control valve 17 connected to the direction switching valve 20, and an operation lever 16 connected to the remote control valve 17 are provided. As shown in FIGS. 1 and 2, the working hydraulic control device 1 is provided in the regenerated oil path 50 that connects the meter-in oil path 30 and the meter-out oil path 40 of the hydraulic motor 13 and the meter-in oil path 30. The meter-in throttle 61 and the meter-in flow controller 62 (meter-in flow control means), the meter-out throttle 71 provided in the meter-out oil passage 40, the meter-out flow controller 72, and the back pressure valve 81 are provided.

  The engine 11 (power source) is a power source of the hydraulic pump 12, as shown in FIG. The power source of the hydraulic pump 12 may be, for example, an electric motor.

  The hydraulic pump 12 supplies pressure oil to the hydraulic motor 13 via the direction switching valve 20. The hydraulic pump 12 is, for example, a variable capacity type.

The hydraulic motor 13 (hydraulic actuator) is driven by the pressure oil supplied from the hydraulic pump 12 to move the suspended load 15 (load). A winch drum 14 is connected to the hydraulic motor 13. The suspended load 15 is suspended by a cable wound around the winch drum 14. When the hydraulic motor 13 is driven, the winch drum 14 is driven, and the suspended load 15 moves up and down via the cable.
The “hydraulic actuator” may be a hydraulic cylinder. Further, the “load” need not be the suspended load 15. Specifically, for example, the working hydraulic control device 1 may be a device that drives an attachment (load) (not shown) such as a boom by a hydraulic cylinder (not shown). In this case, the hydraulic cylinder lowers the attachment in its own weight lowering direction, or raises it in the opposite direction.

  The operation lever 16 (operation means) is means for operating (instructing) the operation speed (direction and magnitude of rotation) of the hydraulic motor 13. The operation lever 16 is a lever operated by an operator of the work hydraulic control device 1.

  The remote control valve 17 generates a pilot pressure according to the lever operation amount (operation amount) of the operation lever 16. The remote control valve 17 applies a pilot pressure to the pilot oil chamber of the direction switching valve 20 via the winding pilot line 27 and the lowering pilot line 28.

  The direction switching valve 20 is a valve that switches the direction of the pressure oil flowing from the hydraulic pump 12 to the hydraulic motor 13. The direction switching valve 20 is a valve (main spool) that controls the flow rate of the pressure oil flowing from the hydraulic pump 12 to the hydraulic motor 13 according to the lever operation amount of the operation lever 16 (in accordance with the pilot pressure). The direction switching valve 20 is disposed between the hydraulic pump 12 and the hydraulic motor 13 (inlet side) and between the hydraulic motor 13 (outlet side) and the tank Ta1. The direction switching valve 20 is connected to the tank Ta2 via the bleed-off flow path 26.

The direction switching valve 20 has three types of switching positions (positions). The direction switching valve 20 includes a neutral position 21, a winding position 22, and a lowering position 23.
Here, the piping 31 connecting the hydraulic pump 12 and the direction switching valve 20, the piping 32 connecting the direction switching valve 20 and the junction 52 (described later), and the junction 52 and the hydraulic motor 13 are connected. The piping is referred to as piping 33. Also, a pipe 41 connecting the hydraulic motor 13 and the direction switching valve 20, a pipe 42 connecting the direction switching valve 20 and a branch point 51 (described later), and a pipe connecting the branch point 51 and the tank Ta1. The pipe 43 is used.

  The neutral position 21 is a switching position when the hydraulic motor 13 is not driven. When the operation lever 16 is neutral (the lever operation amount is zero), the direction switching valve 20 is in the neutral position 21. At this time, the piping 31 and the piping 32 that connect the hydraulic pump 12 and the hydraulic motor 13 are blocked. At this time, the pressure oil flowing from the hydraulic pump 12 to the direction switching valve 20 returns to the tank Ta2 through the bleed-off flow path 26.

  The winding position 22 is a switching position when the hydraulic motor 13 is driven in the direction of winding the suspended load 15. When the hoist lever operation is given to the operation lever 16, the remote control valve 17 generates a pilot pressure in the hoist pilot line 27, and the switching position of the direction switching valve 20 becomes the hoist position 22. At this time, the pressure oil discharged from the hydraulic pump 12 is supplied to the hydraulic motor 13 via the pipes 31 and 41, and the hydraulic motor 13 is driven in the winding direction. The pressure oil discharged from the hydraulic motor 13 returns to the tank Ta1 via the pipes 33, 32, 42, and 43.

  The lowering position 23 is a switching position when the hydraulic motor 13 is driven in a direction to lower the suspended load 15. When the lowering lever operation is given to the operation lever 16, the remote control valve 17 generates a pilot pressure in the lowering pilot line 28, and the switching position of the direction switching valve 20 becomes the lowering position 23. At this time, the pressure oil discharged from the hydraulic pump 12 is supplied to the hydraulic motor 13 via the pipes 31, 32, and 33, and the hydraulic motor 13 is driven in the lowering direction. The pressure oil discharged from the hydraulic motor 13 returns to the tank Ta1 through the pipes 41, 42 and 43.

  Further, the direction switching valve 20 has a throttle function in which the valve opening degree changes in accordance with the lever operation amount of the operation lever 16. More specifically, as the lever operation amount of the operation lever 16 is larger, the amount of change (the spool stroke amount) from the neutral position 21 of the direction switching valve 20 becomes larger. As the amount of change increases, the flow rate of the pressure oil supplied from the hydraulic pump 12 to the pipe 32 (at the time of lowering) or the pipe 41 (at the time of hoisting) increases, and the rotational speed of the hydraulic motor 13 increases. Further, as the amount of change increases, the flow rate of the pressure oil that returns to the tank Ta2 via the bleed-off flow path 26 decreases.

  Here, the oil passage on the pressure oil supply side from the hydraulic pump 12 to the hydraulic motor 13 when the direction switching valve 20 is at the lowering position 23 is referred to as a “meter-in oil passage 30”. Specifically, the meter-in oil passage 30 includes a pipe 31, an oil path in the lowering position 23 of the direction switching valve 20, a pipe 32, and a pipe 33. The oil passage on the pressure oil discharge side from the hydraulic motor 13 to the tank Ta1 when the direction switching valve 20 is at the lowering position 23 is referred to as a “meter-out oil passage 40”. Specifically, the meter-out oil passage 40 includes a pipe 41, an oil path in the lowering position 23 of the direction switching valve 20, a pipe 42, and a pipe 43. The following description is based on the premise that the direction switching valve 20 is at the lowering position 23 (except for the second and later embodiments described later).

  Further, as described above, the direction switching valve 20 has a throttling function. That is, the direction switching valve 20 includes a meter-in throttle 61 (described later), a meter-out throttle 71 (described later), and a bleed-off throttle 21 a in the lowering position 23. The bleed-off throttle 21 a is a throttle that controls a flow rate that is bypassed to the tank Ta <b> 2 via the bleed-off flow path 26 among the flow rates discharged from the hydraulic pump 12.

  As shown in FIG. 2, the regenerated oil passage 50 branches from the meter-out oil passage 40 at a branch point 51 upstream of a back pressure valve 81 (described later), and joins the meter-in oil passage 30 at a junction 52. It is.

  The check valve 53 is a valve that is provided in the regenerated oil passage 50 and allows hydraulic oil to pass only in the direction of flowing from the meter-out oil passage 40 (branch point 51) to the meter-in oil passage 30 (confluence point 52). The check valve 53 prevents pressure oil from flowing from the meter-in oil passage 30 to the meter-out oil passage 40 without passing through the hydraulic motor 13.

(Meter-in side)
The meter-in throttle 61 is a throttle provided in the meter-in oil passage 30, and the valve opening (opening) changes according to the amount of lever operation of the operation lever 16 (see FIG. 1). Note that the meter-in throttle 61 may be provided separately from the direction switching valve 20 (see FIG. 1).

As shown in FIG. 2, the meter-in flow controller 62 (meter-in flow rate control means) detects the differential pressure across the meter-in throttle 61 (the differential pressure between the upstream side and the downstream side). The meter inflow controller 62 controls the flow rate of the meter-in oil passage 30 so that the differential pressure before and after is maintained at a constant set differential pressure ΔPmi. The meter inflow controller 62 controls the meter-in flow rate Qmi on the upstream side of the junction 52 with the regenerated oil passage 50 in the meter-in oil passage 30.
More specifically, the meter inflow controller 62 is provided on the upstream side of the junction 52. The meter inflow controller 62 is provided, for example, in the pipe 31 on the upstream side (or may be downstream) of the meter-in throttle 61, and is provided in parallel (or in series) with the meter-in oil passage 30. Pilot pressure is introduced into the meter inflow controller 62 from the upstream side and the downstream side of the meter-in throttle 61 via pilot lines 63 and 64. The set differential pressure ΔPmi of the meter inflow controller 62 is set by, for example, a spring force. The meter inflow controller 62 controls the valve opening so that the detected front-rear differential pressure matches the set differential pressure ΔPmi. The meter inflow controller 62 decreases the meter-in flow rate Qmi (increases the flow rate returning to the tank Ta3) when the detected differential pressure before and after increases. The meter inflow controller 62 increases the meter-in flow rate Qmi (decreases the flow rate returning to the tank Ta3) when the front-rear differential pressure is about to decrease.

(Meter-out side)
The meter-out throttle 71 is provided in the meter-out oil passage 40 of the hydraulic motor 13, and the valve opening (opening) changes according to the lever operation amount of the operation lever 16 (see FIG. 1). The meter-out throttle 71 may be provided separately from the direction switching valve 20 (see FIG. 1).

As shown in FIG. 2, the meter-out flow controller 72 detects the differential pressure across the meter-out throttle 71 and adjusts the flow rate of the meter-out oil passage 40 so as to maintain the differential pressure before and after the pressure at a constant set differential pressure ΔPmo. Control. The meter-out flow controller 72 controls the meter-out flow rate Qmo on the upstream side of the branch point 51 with the regenerated oil passage 50 in the meter-out oil passage 40.
More specifically, the meter-out flow controller 72 is provided upstream of the branch point 51. The meter-out flow controller 72 is provided, for example, on the downstream side (or upstream side) of the meter-out throttle 71, and is provided, for example, in series (or in parallel) with the meter-out oil passage 40. Pilot pressure is introduced into the meter-out flow controller 72 from the upstream side and the downstream side of the meter-out throttle 71 via pilot lines 73 and 74. The set differential pressure ΔPmo of the meter out flow controller 72 is set by, for example, a spring force. The meter-out flow controller 72 controls the valve opening so that the detected front-rear differential pressure matches the set differential pressure ΔPmo. The meter-out flow controller 72 decreases the meter-out flow rate Qmo (closes the valve opening) when the detected front-rear differential pressure increases, and increases the meter-out flow rate Qmo (the valve opening increases when the front-back differential pressure decreases). open).

  The back pressure valve 81 is a valve provided downstream of the meter-out throttle 71 and downstream of the meter-out flow controller 72, and generates a set back pressure Pbk (for example, a constant pressure P1) upstream of the back pressure valve 81. The set back pressure Pbk of the back pressure valve 81 is set by a spring force, for example, and is approximately the same as the set pressure P1 of the conventional external pilot type counter balance valve 784 (see FIG. 16) (about 1 MPa or the like). The back pressure valve 81 is a valve having the same structure as, for example, a relief valve. When the back pressure valve 81 has the same structure as the relief valve, when the pressure upstream of the back pressure valve 81 is less than the set back pressure Pbk, the back pressure valve 81 closes the valve opening (opening), and the detected pressure is the set back pressure Pbk. When it is larger, the back pressure valve 81 opens the valve opening.

  The back pressure valve 81 need not have the same structure as the relief valve. The back pressure valve 81 may be, for example, a throttle that gradually increases the valve opening (throttle opening) in accordance with an increase in the lever operation amount of the operation lever 16 (see FIG. 1). In this case, the opening area Abk of the back pressure valve 81 is set as [Equation 1]. Cv is a flow coefficient, ΔPbk is a differential pressure between the set back pressure Pbk of the back pressure valve 81 and the pressure of the tank Ta1 (eg, atmospheric pressure), and Qbk is a flow rate through the back pressure valve 81. The flow rate Qbk coincides with the meter-in flow rate Qmi from the flow rate balance if the amount of leakage (pressure oil leakage at the hydraulic motor 13 or the like) is ignored.

(Operation of the working hydraulic control device 1)
Next, the operation of the working hydraulic control device 1 will be described. The outline of this operation is as follows. The working hydraulic control device 1 has the same function as a conventional external pilot type counter balance valve 784 (see FIG. 16). That is, in order to prevent cavitation in the meter-in oil passage 30, the meter-in pressure Pmi (the pressure downstream from the meter-in throttle 61, the pressure at the inlet of the hydraulic motor 13, the pressure in the pipes 32 and 33) of the meter-in oil passage 30 is a predetermined pressure. It is controlled not to become less than. Therefore, the working hydraulic control device 1 operates as in the following (1) to (4). (1) The pressure upstream of the back pressure valve 81 is set to the set back pressure Pbk (= pressure P1) (the pressure is raised). (2) The meter-out flow rate Qmo is controlled to be larger than the meter-in flow rate Qmi. (3) Pressure oil flows from the meter-out oil passage 40 to the meter-in oil passage 30 via the regenerated oil passage 50. (4) As the meter-in pressure Pmi, the set back pressure Pbk of the back pressure valve 81 is ensured (the pressure raised by the back pressure valve 81 rides on the meter-in oil passage 30). Details will be described below.

(Ensure flow rate conditions and meter-in pressure)
The meter-out flow rate Qmo is controlled to be larger than the meter-in flow rate Qmi. That is, the meter out flow controller 72 and the meter in flow controller 62 are controlled so that Qmo> Qmi (specific operation will be described later).

  By the flow rate control (Qmo> Qmi), the flow rate of the pressure oil passing through the regenerated oil passage 50 (regenerated flow rate Qr) is ensured. More specifically, the flow rate absorbed by the hydraulic motor 13 and the flow rate discharged by the hydraulic motor 13 are the same except for leakage. Therefore, the regeneration flow rate Qr corresponding to the difference between the meter-out flow rate Qmo and the meter-in flow rate Qmi (Qmo-Qmi) flows from the meter-out oil passage 40 into the meter-in oil passage 30 through the regeneration oil passage 50 (the flow rate is Automatically balance).

  The meter-in pressure Pmi becomes the set back pressure Pbk (= pressure P1). More specifically, the pressure on the upstream side of the back pressure valve 81 by the action of the back pressure valve 81 is the set back pressure Pbk. Further, the pressure oil flows through the regeneration oil passage 50 (a regeneration flow rate Qr is ensured). Therefore, the meter-in pressure Pmi becomes the set back pressure Pbk of the back pressure valve 81. Thereby, cavitation in the meter-in oil passage 30 is suppressed.

(Flow control operation)
Next, the operation of controlling the meter-in flow rate Qmi and the meter-out flow rate Qmo will be further described. The meter-in flow rate Qmi is controlled so as to satisfy the equation shown in [Equation 2] and the meter-out flow rate Qmo is satisfied in [Equation 3].

  Cv in the above formula is a flow coefficient. ΔPmi is a differential pressure across the meter-in throttle 61 and a set differential pressure of the meter-in flow controller 62. ΔPmo is a differential pressure before and after the meter-out restrictor 71 and a set differential pressure of the meter-out flow controller 72. Ami is the opening area of the meter-in stop 61. Amo is the opening area of the meter-out stop 71. As shown in FIG. 3, the opening area Ami and the opening area Amo increase or decrease according to the lever operation amount of the operation lever 16. As a result, as shown in FIG. 4, the meter-in flow rate Qmi and the meter-out flow rate Qmo increase or decrease according to the lever operation amount of the operation lever 16. Specifically, the flow rate Qmi and the flow rate Qmo increase as the lever operation amount increases.

  In order to satisfy the above flow control condition (Qmo> Qmi), the opening area Ami of the meter-in throttle 61 and the opening area Amo of the meter-out throttle 71 may be adjusted (the valve opening may be adjusted). ). For example, when the set differential pressure ΔPmi (see [Equation 2]) and the set differential pressure ΔPmo (see [Equation 3]) are approximately the same, as shown in FIG. 3, the opening area Ami of the meter-in restrictor 61 is the meter-out restrictor. It is set to be smaller than the opening area Amo of 71. Specifically, a direction switching valve 20 (see FIG. 1) that satisfies the above conditions is used.

(Modification of control of meter-in flow rate Qmi)
The meter-in flow rate Qmi may be controlled as follows.

  For example, the meter-in flow rate Qmi may be controlled by controlling the discharge flow rate of the hydraulic pump 12 shown in FIG. More specifically, the hydraulic pump 12 is a variable displacement pump. And the capacity | capacitance of the hydraulic pump 12 is increased and the discharge flow volume of the hydraulic pump 12 is increased, so that the lever operation amount of the operation lever 16 (refer FIG. 1) becomes large. As a result, as shown in FIG. 4, the meter-in flow rate Qmi is controlled to increase as the lever operation amount increases.

  Further, for example, the meter-in flow rate Qmi may be controlled by controlling the bleed-off throttle 21a shown in FIG. More specifically, the bleed-off throttle 21a is controlled so that the pressure oil returning from the hydraulic pump 12 to the tank Ta2 decreases as the lever operation amount increases. Specifically, as shown in FIG. 5, the bleed-off stop 21a is controlled so that the opening area Abo of the bleed-off stop 21a decreases as the lever operation amount increases. Thus, the meter-in flow rate Qmi is controlled to increase as the lever operation amount increases.

(effect)
Next, the effect of the working hydraulic control device 1 shown in FIG. 1 will be described. The working hydraulic control device 1 includes a hydraulic pump 12, a hydraulic motor 13 (hydraulic actuator) that is driven by pressure oil supplied from the hydraulic pump 12 to move the suspended load 15 (load), and an operating speed of the hydraulic motor 13. An operation lever 16 (operation means) to be operated. The working hydraulic control device 1 drives the hydraulic motor 13 so that the suspended load 15 moves (lowers) in the direction of falling its own weight.

(Effect 1-1)
As shown in FIG. 2, the working hydraulic control device 1 includes a regenerated oil passage 50 and a check valve 53. The regenerated oil passage 50 branches from the meter-out oil passage 40 on the upstream side (the branch point 51) of the back pressure valve 81 and merges with the meter-in oil passage 30 (at the junction 52). The check valve 53 is provided in the regenerative oil passage 50 and allows pressure oil to pass only in the direction of flowing from the meter-out oil passage 40 to the meter-in oil passage 30.
With this configuration, pressure oil can flow from the meter-out oil passage 40 to the meter-in oil passage 30.

The working hydraulic control device 1 also includes meter-in flow control means (for example, a meter inflow controller 62) that controls the flow rate of the meter-in oil passage 30 of the hydraulic motor 13. The meter-in flow rate control means controls the meter-in flow rate Qmi upstream of the junction 52 with the regenerated oil passage 50 in the meter-in oil passage 30. The meter-out flow controller 72 controls the meter-out flow rate Qmo on the upstream side of the branch point 51 with the regenerated oil passage 50 in the meter-out oil passage 40. Then, the meter-out flow rate Qmo is controlled to be larger than the meter-in flow rate Qmi.
Therefore, the pressure oil surely flows from the meter-out oil passage 40 to the meter-in oil passage 30 through the regeneration oil passage 50 from the flow rate balance between the meter-in oil passage 30 and the meter-out oil passage 40 (a regeneration flow rate Qr is ensured). ).

Further, the working hydraulic control device 1 includes a back pressure valve 81. The back pressure valve 81 is provided downstream of the meter-out throttle 71 provided in the meter-out oil passage 40 and downstream of the meter-out flow controller 72. The back pressure valve 81 generates a set back pressure Pbk on the upstream side of the back pressure valve 81.
As described above, since the pressure oil flows from the meter-out oil passage 40 to the meter-in oil passage 30 via the regeneration oil passage 50, the pressure in the meter-in oil passage 30 (meter-in pressure Pmi) becomes the set back pressure Pbk of the back pressure valve 81. Become. That is, the minimum pressure in the meter-in oil passage 30 is compensated. Therefore, cavitation in the meter-in oil passage 30 can be suppressed. As a result, the problem that the hydraulic motor 13 stalls due to cavitation and the suspended load 15 falls can be suppressed.

(Effect 1-2)
The work hydraulic control device 1 includes a meter-out flow controller 72. The meter-out flow controller 72 detects the differential pressure across the meter-out throttle 71 and controls the flow rate Qmo of the meter-out oil passage 40 so as to maintain the differential pressure across the meter at a constant set differential pressure ΔPmo.
That is, the meter-out flow control 72 has the meter-out oil passage 40 at the measurement point and the control point (the collocation is taken in terms of control theory, and the measurement point and the control point are in agreement). Therefore, valve hunting or pressure hunting (see FIG. 17) due to the provision of the meter-out flow control 72 is suppressed.

  The back pressure valve 81 is provided in the meter-out oil passage 40 and generates a set back pressure Pbk on the upstream side of the back pressure valve 81. That is, the measurement point and control point of the back pressure valve 81 are the meter-out oil passage 40. Therefore, valve opening and pressure hunting (see FIG. 17) due to the provision of the back pressure valve 81 are suppressed.

  As described above, the working hydraulic control apparatus 1 can suppress cavitation in the meter-in oil passage 30 without using a valve that easily causes valve opening and pressure hunting (see FIG. 17). As a result, hunting of the rotational speed of the hydraulic motor 13 can be suppressed.

(Effect 1-3)
As described above, the working hydraulic control apparatus 1 can suppress the occurrence of valve opening and pressure hunting. Therefore, when the pressure in the meter-in oil passage 30 is increased, the valve provided in the meter-out oil passage 40 (the meter-out flow controller 72 and the back pressure valve 81) is hunted by taking a measure to loosen the response of the valve. There is no need to suppress this. Therefore, the deterioration of the responsiveness of the valve due to the above countermeasure can be suppressed, the generation of useless boost pressure (see FIG. 18B) due to the above countermeasure can be suppressed, and the deterioration of fuel consumption due to this useless boost pressure can be suppressed (see FIG. 7).

  This effect will be described in more detail. In the conventional working hydraulic control device 701 shown in FIG. 16, a throttle 786 is provided in the pilot line 785 of the external pilot type counter balance valve 784 in order to suppress the above-described hunting. The working hydraulic control device 701 operates as follows. It is assumed that the meter-in pressure Pmi has increased at time T0. Specifically, for example, the operation lever 16 is operated from the neutral position to the lowered position at time T0. Then, the counter balance valve 784 opens the valve opening so that the meter-in pressure Pmi becomes the set pressure P1 of the counter balance valve 784. However, due to the action of the throttle 786, it takes a long time (time T0 to T1) until the valve opening of the counter balance valve 784 reaches an appropriate valve opening A1 (see FIG. 18A). During this time T0 to T1, pressure loss occurs in the counter balance valve 784 (throttle resistance is generated). Accordingly, as shown in FIG. 18B, the meter-in pressure Pmi is higher than the set pressure P1 of the counter balance valve 784 between times T0 and T1. That is, useless boost pressure is generated as shown by the diagonal lines in FIG. As a result, the fuel consumption of the working hydraulic control device 701 (see FIG. 16) may be deteriorated.

  On the other hand, the working hydraulic control device 1 of the present invention shown in FIG. 1 can suppress the above-described hunting, and therefore, a countermeasure such as a restriction 786 (see FIG. 16) is unnecessary. The working hydraulic control device 1 without such a measure operates as follows. Similarly to the above, it is assumed that the operation lever 16 is operated from the neutral position to the lowering position at time T0. Then, as shown in FIG. 6, the meter-in pressure Pmi is immediately controlled (almost immediately after time T0) such that the meter-in pressure Pmi becomes the set back pressure Pbk (= pressure P1) of the back pressure valve 81. Therefore, compared to the prior art, the meter-in pressure Pmi greatly decreases during the time T0 to T1. Here, the power required for driving the hydraulic pump 12 shown in FIG. 1 is proportional to the product of the pressure and the flow rate of the discharged oil. In the working hydraulic control device 1, the meter-in pressure Pmi is lower than that in the prior art. Therefore, the power necessary for driving the hydraulic pump 12 is also lower than that in the prior art, and the power of the engine 11 that drives the hydraulic pump 12 is also higher than that in the prior art. Also decreases. As a result, as shown in FIG. 7, the fuel consumption of the engine 11 can be significantly reduced as compared with the prior art (for example, it can be reduced to about half between times T0 to T1).

(Effect 1-4)
As shown in FIG. 2, the working hydraulic control device 1 includes a regenerated oil passage 50. Therefore, the meter-in flow rate Qmi and the regeneration flow rate Qr are supplied to the hydraulic motor 13. Therefore, compared with the case where the regeneration oil passage 50 is not provided, the flow rate discharged by the hydraulic pump 12 is reduced by the regeneration flow rate Qr. Therefore, the power required for driving the hydraulic pump 12 is reduced. Therefore, the fuel consumption of the engine 11 can be reduced (refer to the part after the time T1 in the graph shown in FIG. 7).

(Effect 1-5)
Further, the working hydraulic control device 1 includes a meter-out throttle 71 whose valve opening (opening) changes according to the lever operation amount of the operation lever 16. That is, if the lever operation amount of the operation lever 16 is the same, the valve opening degree of the meter-out throttle 71 (proportional to the opening area Amo of [Equation 3]) is the same. Further, the differential pressure across the meter-out throttle 71 is held at a constant set differential pressure ΔPmo (see [Equation 3]) by the meter-out flow controller 72. Therefore, if the lever operation amount of the operation lever 16 is the same, the meter-out flow rate Qmo (see [Equation 3]) is also the same. That is, if the lever operation amount is the same, the speed of the hydraulic motor 13 does not change even if the weight of the suspended load 15 shown in FIG. 1 changes. Therefore, the problem that the speed of the hydraulic motor 13 changes according to the weight of the suspended load 15 can be suppressed, and as a result, deterioration of operability and safety can be suppressed.

(Effect 2)
In addition, the working hydraulic control device 1 includes a meter-in throttle 61 provided in the meter-in oil passage 30. The “meter-in flow control means” includes a meter-in flow controller 62. The meter inflow controller 62 detects the differential pressure across the meter-in throttle 61 and controls the flow rate Qmi of the meter-in oil passage 30 so as to maintain the differential pressure before and after at a constant set differential pressure ΔPmo.
With this configuration, the meter-in flow rate Qmi can be reliably controlled.

(Second Embodiment)
The working hydraulic control apparatus 201 according to the second embodiment will be described with reference to FIGS.
In the working hydraulic control apparatus 1 shown in FIG. 1, the meter-out flow controller 72 and the back pressure valve 81 are provided on the downstream side of the direction switching valve 20. In the working hydraulic control device 1, the meter-out throttle 71 is a part of the direction switching valve 20.
In the working hydraulic control apparatus 201 shown in FIG. 8, a meter-out valve 271 (meter-out throttle), a meter-out flow controller 72, and a back pressure valve 81 are provided on the upstream side of the direction switching valve 20. In the work hydraulic control apparatus 201, the meter-out valve 271 has a function of a meter-out throttle 71 (see FIG. 1). A pipe connecting the hydraulic motor 13 and the direction switching valve 20 and provided with the meter-out valve 271, the meter-out flow controller 72, and the back pressure valve 81 is referred to as a pipe 241. The pipe 241 is provided with a bypass oil passage 255 for winding in parallel with the pipe 241. Hereinafter, the difference will be further described.

When the hoisting bypass oil passage 255 is hoisted (when the direction switching valve 20 is at the hoisting position 22), the meter-out valve 271, the meter-out flow controller 72, and the back pressure valve 81 (these valves are referred to as “valves 271, 72, and 81 ”) and an oil passage for supplying pressure oil from the hydraulic pump 12 to the hydraulic motor 13. The winding-up bypass oil passage 255 branches and merges from the pipe 241 at a branch point 256 and a junction point 257 before and after the valves 271, 72, and 81. A check valve 258 is provided in the winding-up bypass oil passage 255. A check valve 244 is provided between the branch point 256 and the back pressure valve 81 (on the pipe 241).
When the winding lever is operated by the operation lever 16, the pressure oil flows as follows. By the action of the check valves 244 and 258, pressure oil is supplied from the hydraulic pump 12 to the hydraulic motor 13 through the pipe 31 and the winding-up bypass oil passage 255. The pressure oil discharged from the hydraulic motor 13 returns to the tank Ta1 via the pipes 33, 32, and 43. In the following, description will be made on the premise of lowering.

  The meter-out valve 271 (meter-out throttle) is provided separately from the direction switching valve 20 and has the same function as the meter-out throttle 71 (see FIG. 2) described above. The pilot pressure generated by the remote control valve 17 valve acts on the meter-out valve 271 via the pilot line 228. The pilot line 228 branches from the lowering pilot line 28, for example. The meter-out valve 271 includes a lowering position 271a and a non-lowering position 271b.

(Operation of the working hydraulic control device 201)
The working hydraulic control device 201 operates as follows. When the lever operation amount of the operation lever 16 is zero, the direction switching valve 20 is in the neutral position 21 and the meter-out valve 271 is in the non-lowering position 271b. When a lowering lever operation is input by the operation lever 16, pilot pressure is generated in the lowering pilot line 28 and the pilot line 228. Then, the direction switching valve 20 is switched to the lowering position 23, and the meter-out valve 271 is switched to the lowering position 271a.

  FIG. 9 shows the relationship between the opening area of the meter-out valve 271 and the opening area of the direction switching valve 20 and the lever operation amount of the operation lever 16 (see FIG. 8). The meter-out valve 271 is controlled so that the valve opening degree increases as the lever operation amount increases (moves toward the lowering position 271a shown in FIG. 8). On the other hand, as shown in FIG. 9, the direction switching valve 20 is set to be fully opened as soon as the lowering lever operation is input. As a result, the meter-out flow rate Qmo at the time of lowering is controlled by the meter-out valve 271 instead of the direction switching valve 20 shown in FIG.

(Effect of 2nd Embodiment)
Next, the effect of the working hydraulic control device 201 will be described. In the working hydraulic control device 201, the meter-out valve 271 and the meter-out flow controller 72 are provided on the upstream side of the direction switching valve 20. Therefore, the distance between the meter-out valve 271 and the meter-out flow controller 72 and the hydraulic motor 13 can be made smaller than the distance between the direction switching valve 20 and the hydraulic motor 13. Therefore, the meter-out valve 271 and the meter-out flow controller 72 can be disposed in the immediate vicinity of the hydraulic motor 13. As a result, it is possible to suppress the deterioration of the response of the operation speed of the hydraulic motor 13.

  More specifically, the piping length between the hydraulic motor 13 and the direction switching valve 20 is often long due to the arrangement of the devices. Therefore, when the meter-out throttle 71 and the meter-out flow controller 72 are provided in the direction switching valve 20 or on the downstream side of the direction switching valve 20 as in the working hydraulic control device 1 shown in FIG. The length of the piping between the outflow controller 72 and the hydraulic motor 13 may be long. As a result, the operation lever 16 may be operated by a lowering lever, the flow rate may be controlled by the meter-out throttle 71 and the meter-out flow controller 72, and the rotational speed of the hydraulic motor 13 may be controlled. is there. On the other hand, in the working hydraulic control apparatus 201 shown in FIG. 8, the pipe length connecting the meter-out throttle 71, the meter-out flow controller 72, and the hydraulic motor 13 can be shortened, so that deterioration of the responsiveness is suppressed. it can.

(Third embodiment)
The working hydraulic control device 301 according to the third embodiment will be described with reference to FIGS. 10 to 11 (the safety ensuring pressure control valve 682 in FIG. 10 will be described in the sixth embodiment). In the working hydraulic control apparatus 1 shown in FIG. 1, the set back pressure Pbk of the back pressure valve 81 is set to a constant pressure P1. In the working hydraulic control device 301 shown in FIG. 10, as shown in FIG. 11, the set back pressure Pbk is made smaller than the pressure P1 in a predetermined case (control is performed so that the valve opening of the back pressure valve 81 is opened). Hereinafter, the difference will be described.

  First, a winding circuit will be described. As shown in FIG. 10, the oil passage on the pressure oil supply side from the hydraulic pump 12 to the hydraulic motor 13 when the direction switching valve 20 is at the winding position 22 is referred to as a “roll-up meter-in oil passage 330”. Specifically, the pipe 31, the oil passage in the winding position 22 of the direction switching valve 20, and the pipe 41 are set as a meter-in oil path 330 for winding. In addition, the direction switching valve 20 includes a hoisting meter-in throttle 365 in the hoisting position 22. The hoisting meter-in throttle 365 changes the valve opening according to the amount of lever operation of the operating lever 16, similarly to the lowering meter-in throttle 61.

A pilot line 364 is connected to the back pressure valve 81.
At the time of lowering, the meter-in pressure Pmi acts as a pilot pressure on the back pressure valve 81 via the pilot line 364. The pilot line 364 branches from the meter-in oil passage 30 in the lowering position 23 of the direction switching valve 20 and downstream of the meter-in throttle 61.
At the time of winding, the meter-in pressure Pmi ′ at the time of winding acts on the back pressure valve 81 as a pilot pressure via the pilot line 364. The meter-in pressure Pmi ′ at the time of winding is the pressure of the hoisting meter-in oil passage 330 downstream from the hoisting meter-in throttle 365 (pressure at the inlet of the hydraulic motor 13 at the time of hoisting, pressure of the pipe 41 at the time of hoisting). The pilot line 364 branches off from the hoisting meter-in oil passage 330 in the hoisting position 22 of the direction switching valve 20 and downstream of the hoisting meter-in throttle 365.

(Operation of Working Hydraulic Control Device 301)
(When unloaded, etc.)
Next, the operation of the working hydraulic control device 301 will be described.
When the meter-in pressure Pmi increases at the time of lowering, the valve opening degree of the back pressure valve 81 is controlled to be opened (set back pressure Pbk is decreased). Details will be described below.

At the time of normal lowering (at the time of lowering with load), the meter-in pressure Pmi becomes the set back pressure Pbk (= pressure P1) of the back pressure valve 81 as described above. That is, when the load is lowered, the meter-in pressure Pmi is always constant and does not increase.
On the other hand, when the hydraulic motor 13 is driven in the lowering direction in the state where there is no suspended load 15 (empty hook) (when no load is being lowered), the meter-in pressure Pmi may increase. More specifically, when unloaded, the weight of the suspended load 15 does not act on the hydraulic motor 13, so that no holding pressure is generated in the meter-out oil passage 40. Further, since the hydraulic motor 13 is driven, the meter-in pressure Pmi becomes larger than the meter-out pressure Pmo. Therefore, pressure oil does not flow through the regenerated oil passage 50 due to the action of the check valve 53 of the regenerated oil passage 50. Accordingly, the meter-in pressure Pmi is at least the maximum value (= pressure P1) of the set back pressure Pbk of the back pressure valve 81 (the meter-in pressure Pmi is equal to or higher than the pressure on the upstream side of the meter-out flow controller 72 and the upstream side of the meter-out throttle 71 Or more). The meter-in pressure Pmi increases or decreases according to the discharge pressure of the hydraulic motor 13 and the operation of the meter-in throttle 61.
Not only when the suspended load 15 is unwound but also when the suspended load 15 that is so light that no holding pressure is generated in the meter-out oil passage 40 is similarly lowered when the meter-in pressure Pmi increases. There is.

  When the meter-in pressure Pmi increases, the valve opening degree of the back pressure valve 81 is controlled to open. More specifically, when the meter-in pressure Pmi increases, the increased meter-in pressure Pmi acts on the back pressure valve 81 as a pilot pressure via the pilot line 364. Then, for example, the set back pressure Pbk of the back pressure valve 81 is lowered by pushing back a spring that sets the set back pressure Pbk of the back pressure valve 81. FIG. 11 shows the relationship between the set back pressure Pbk of the back pressure valve 81 and the meter-in pressure Pmi. As shown in FIG. 11, the set back pressure Pbk of the back pressure valve 81 is set to decrease (proportionally decrease) as the meter-in pressure Pmi increases. The relationship between the set back pressure Pbk and the meter-in pressure Pmi may be changed as appropriate.

(When winding up)
At the time of winding up (as shown in FIG. 10, instead of driving the hydraulic motor 13 so that the suspended load 15 moves in the direction in which the weight is dropped, the hydraulic motor 13 is moved in the direction opposite to the direction in which the weight is dropped. In the case of driving), the valve opening degree of the back pressure valve 81 is controlled to be opened. Details will be described below.

  At the time of winding, the working hydraulic control device 301 operates as follows. It is assumed that the winding lever is operated with the operation lever 16. Then, according to the operation of the hydraulic pump 12 and the hoisting meter-in throttle 365, the pressure of the pipe 41 of the hoisting meter-in oil passage 330 (the meter-in pressure Pmi 'at the time of hoisting) increases. The meter-in pressure Pmi ′ at the time of winding acts on the back pressure valve 81 via the pilot line 364 as a pilot pressure. Then, the back pressure valve 81 is controlled to open as in the case of unloading with no load. The relationship between the meter-in pressure Pmi ′ at the time of winding and the set back pressure Pbk is set, for example, in the same manner as the relationship between the meter-in pressure Pmi at the time of no-load lowering and the set back pressure Pbk (see FIG. 11) (different settings). As good). Further, when the pressure oil does not pass through the back pressure valve 81 at the time of winding up as in the working hydraulic control device 201 shown in FIG. 8, it is not necessary to reduce the set back pressure Pbk of the back pressure valve 81 at the time of winding up.

(Effect 3)
Next, the effect of the working hydraulic control device 301 shown in FIG. 10 will be described. When the pressure in the meter-in oil passage 30 rises during lowering (case a), or when raising (instead of driving the hydraulic motor 13 so that the suspended load 15 moves in the direction in which the weight falls) When the hydraulic motor 13 is driven so that the suspended load 15 moves in the reverse direction (case b), the pressure upstream and downstream of the hydraulic motor 13 is sufficiently high, so that the problem of cavitation does not occur.
In the case of (Case a) or (Case b), the working hydraulic control device 301 performs control so that the valve opening (opening) of the back pressure valve 81 is opened. Therefore, the pressure upstream and downstream of the hydraulic motor 13 can be reduced. Therefore, it is possible to suppress the upstream and downstream pressures of the hydraulic motor 13 from increasing due to the pressure loss of the back pressure valve 81. As a result, it is possible to suppress the power of the hydraulic pump 12 from increasing and the fuel consumption of the engine 11 from deteriorating.

  The above effect will be further described. At the time of lowering the load, the hydraulic motor 13 is turned freely by the weight of the suspended load 15, the meter-in pressure Pmi is lowered, and the above cavitation problem may occur. On the other hand, at the time of winding (case b), the hydraulic motor 13 is driven in the winding direction, so that the pressure before and after the hydraulic motor 13 becomes sufficiently high. Therefore, the above cavitation problem does not occur during winding. Further, as described above, the problem of cavitation in the meter-in oil passage 30 does not occur even during unloading or the like (case a).

As described above (Case a) and (Case b), the circuit pressure rises due to the back pressure valve 81 when the valve opening of the back pressure valve 81 is closed, even though the problem of cavitation does not occur. Specifically, the pressure in the meter-in oil passage 30 and the meter-out oil passage 40 rises at the time of lowering. At the time of winding, the pressure in the pipes 31, 41, 33, 32, 42, and 43 increases. As a result, the power of the hydraulic pump 12 increases and the fuel consumption of the engine 11 deteriorates.
On the other hand, the working hydraulic control device 301 controls to open the valve opening of the back pressure valve 81 when the cavitation problem does not occur, so that deterioration of fuel consumption can be suppressed.

(Fourth embodiment)
A working hydraulic control device 401 according to the fourth embodiment will be described with reference to FIGS. Differences from the working hydraulic control apparatus 1 shown in FIG. 1 are as follows. The working hydraulic control device 401 shown in FIG. 12 decreases the valve opening degree of the meter-out throttle 71 when the rotational speed of the engine 11 or the like decreases. The working hydraulic control device 401 includes a controller 491 that inputs and outputs various signals. An engine speed sensor 492, an electromagnetic pressure reducing valve 493, and a pilot pressure sensor 494 are connected to the controller 491. Hereinafter, the difference will be further described.

  The engine speed sensor 492 detects the speed of the engine 11 (power source of the hydraulic pump 12). A sensor (not shown) for detecting the rotation speed of the hydraulic pump 12 may be provided.

  The electromagnetic pressure reducing valve 493 is a valve that is provided on the lowering pilot line 28 and reduces the lowering pilot pressure generated by the remote control valve 17. The “lowering pilot pressure” is a pilot pressure on the lowering pilot line 28 closer to the remote control valve 17 (primary side) than the electromagnetic pressure reducing valve 493.

  The pilot pressure sensor 494 is a sensor that detects the lowered pilot pressure generated by the remote control valve 17.

(Operation of the working hydraulic control device 401)
In the working hydraulic control device 401, when the rotational speed of the engine 11 or the hydraulic pump 12 that is the power source of the hydraulic pump 12 decreases, the valve opening of the meter-out throttle 71 (proportional to the opening area Amo of [Equation 3]). Decrease. As a result, the meter-out flow rate Qmo (see [Equation 3]) decreases, and the speed of the hydraulic motor 13 decreases. Details will be described below.

  When the rotational speed of the engine 11 detected by the engine rotational speed sensor 492 decreases or when the rotational speed of the hydraulic pump 12 decreases, the working hydraulic control device 401 operates as follows. The controller 491 controls the secondary pressure (pressure on the direction switching valve 20 side) of the electromagnetic pressure reducing valve 493 to be lower than the lowering pilot pressure detected by the pilot pressure sensor 494. Then, the direction switching valve 20 approaches the neutral position 21 side. That is, the valve opening of the meter-out throttle 71 is reduced (the valve opening of the meter-in throttle 61 is also reduced). That is, the work hydraulic control device 401 operates in the same manner as when the operation lever 16 is returned to the neutral side (the amount of lever operation is reduced). As a result, the speed of the hydraulic motor 13 decreases. On the contrary, when the rotation speed of the engine 11 increases, the valve opening degree of the meter-out throttle 71 is increased and the speed of the hydraulic motor 13 is increased.

FIG. 13 shows the relationship between the lowering pilot pressure and the secondary pressure of the electromagnetic pressure reducing valve 493. The controller 491 shown in FIG. 12 performs control so that the amount of pressure reduction by the electromagnetic pressure reducing valve 493 increases (decelerates proportionally) as the lowering pilot pressure increases.
FIG. 14 shows a modification of the relationship between the lowering pilot pressure and the secondary pressure of the electromagnetic pressure reducing valve 493. The controller 491 shown in FIG. 12 sets the secondary pressure of the electromagnetic pressure reducing valve 493 to a constant pressure when the lowering pilot pressure is equal to or higher than a predetermined value. When the lowering pilot pressure is less than a predetermined value, the electromagnetic pressure reducing valve 493 does not perform pressure reduction. The relationship between the lowering pilot pressure and the secondary pressure of the electromagnetic pressure reducing valve 493 may be changed as appropriate.

(Effect 4-1)
Next, the effect of the working hydraulic control device 401 shown in FIG. 12 will be described. In the working hydraulic control device 401, when the rotational speed of the engine 11 of the hydraulic pump 12 or the hydraulic pump 12 decreases, the valve opening of the meter-out throttle 71 (proportional to the opening area Amo of [Equation 3]). ). As a result, the flow rate Qmo (see [Equation 3]) of the meter-out oil passage 40 decreases, and the speed of the hydraulic motor 13 decreases. Therefore, the operability of the operation of driving the hydraulic motor 13 at a low speed by reducing the rotational speed of the engine 11 or the hydraulic pump 12 is improved.

  This effect will be described in more detail. In the conventional hydraulic control apparatus for work, there is a case where the suspended load 15 is finely manipulated by reducing the rotational speed of the engine 11 to reduce the lowering speed of the hydraulic motor 13. However, in the working hydraulic control apparatus 1 shown in FIG. 1, even if the rotational speed of the engine 11 is decreased, the lowering speed of the hydraulic motor 13 is not decreased. That is, even if the number of revolutions of the engine 11 decreases and the discharge amount (= meter-in flow rate Qmi) of the hydraulic pump 12 decreases, the shortage of the meter-in flow rate Qmi with respect to the meter-out flow rate Qmo is compensated by the regeneration flow rate Qr. The motor 13 does not decelerate (the hydraulic motor 13 is rotated only by the weight of the suspended load 15). Therefore, the fine operability of the suspended load 15 may be deteriorated. On the other hand, in the working hydraulic control device 401 shown in FIG. 12, since the speed of the hydraulic motor 13 is reduced when the rotational speed of the engine 11 is reduced, the problem of deterioration in fine operability can be solved. The suspended load 15 can be finely operated with the same feeling as the apparatus.

(Fifth embodiment)
A working hydraulic control apparatus 501 according to a fifth embodiment will be described with reference to FIG.
In the working hydraulic control device 401 shown in FIG. 12, the meter-out flow rate Qmo is decreased by decreasing the valve opening degree of the meter-out throttle 71 when the rotational speed of the engine 11 or the like decreases. In the working hydraulic control device 501 shown in FIG. 15, when the rotational speed of the engine 11 or the like is decreased, the meter-out is reduced by reducing the differential pressure across the meter-out throttle 71 (= the set differential pressure ΔPmo of the meter-out flow controller 72). Reduce the flow rate Qmo.
In the working hydraulic control device 401 shown in FIG. 12, an electromagnetic pressure reducing valve 493 is provided in the lowering pilot line 28. In the working hydraulic control device 501 shown in FIG. 15, an electromagnetic pressure reducing valve 593 is provided on a pilot line 575 that connects the pilot hydraulic power source 595 and the meter-out flow controller 72. Hereinafter, the difference will be further described.

  The electromagnetic pressure reducing valve 593 controls the set differential pressure ΔPmo of the meter-out flow control 72. The electromagnetic pressure reducing valve 593 causes the secondary pressure of the electromagnetic pressure reducing valve 593 to act on, for example, the spring chamber side of the meter-out flow controller 72. Then, the controller 491 controls the secondary pressure of the electromagnetic pressure reducing valve 593. This is equivalent to controlling the set differential pressure ΔPmo of the meter-out flow controller 72 (controlling the spring force).

(Operation of the working hydraulic control device 501)
(Effect 4-2)
In the working hydraulic control device 501 shown in FIG. 15, when the rotational speed of the engine 11 or the hydraulic pump 12 as the power source of the hydraulic pump 12 decreases, the set differential pressure ΔPmo (see [Equation 3]) of the meter-out flow controller 72 is obtained. Decrease. As a result, the flow rate Qmo (see [Equation 3]) of the meter-out oil passage 40 decreases, and the speed of the hydraulic motor 13 decreases. Therefore, the operability of the operation of driving the hydraulic motor 13 at a low speed by reducing the number of revolutions of the engine 11 or the hydraulic pump 12 is improved (refer to Effect 4-1 for details).

(Sixth embodiment)
A working hydraulic control apparatus 601 according to the sixth embodiment will be described with reference to FIG. The difference from the working hydraulic control device 1 of FIG. 1 is that a pressure control valve 682 for ensuring safety is provided in the meter-out oil passage 40 as shown in FIG. The working hydraulic control device 601 includes a winding-up bypass oil passage 655. Hereinafter, the difference will be described.

  The hoisting bypass oil passage 655 is an oil passage for supplying pressure oil from the hydraulic pump 12 to the hydraulic motor 13 without passing through the safety ensuring pressure control valve 682 during hoisting. A check valve 658 is provided in the winding-up bypass oil passage 655.

  The safety ensuring pressure control valve 682 is a safety device that closes the valve opening (opening) in an emergency such as when the meter-in oil passage 30 is damaged. The safety ensuring pressure control valve 682 is provided on the upstream side of the branch point 51 with the regenerated oil passage 50 in the meter-out oil passage 40. The safety ensuring pressure control valve 682 closes the valve opening when the meter-in pressure Pmi is lower than the set pressure P3 of the safety ensuring pressure control valve 682. The meter-in pressure Pmi acts as a pilot pressure on the safety control pressure control valve 682 via the pilot line 683. In other words, focusing only on the safety ensuring pressure control valve 682, the safety ensuring pressure control valve 682 has the same configuration as the conventional external pilot type counter balance valve 784 (see FIG. 16). The pilot line 683 is not provided with the conventional diaphragm 786 (see FIG. 16). That is, the safety ensuring pressure control valve 682 immediately opens the valve opening when the meter-in pressure Pmi becomes lower than the set pressure P3.

  The set pressure P3 (cracking set pressure) of the safety ensuring pressure control valve 682 is (slightly) higher than the set back pressure Pbk (= pressure P1 or the like) of the back pressure valve 81. When the set back pressure Pbk is variable (see FIG. 11), the set pressure P3 is set higher than the pressure P1 that is the maximum value of the set back pressure Pbk.

(Operation of Working Hydraulic Control Device 601)
Under normal conditions, the safety ensuring pressure control valve 682 is in an open state. More specifically, as described above, when the lowering operation is performed with the operation lever 16, the meter-in pressure Pmi immediately becomes the set back pressure Pbk of the back pressure valve 81. This set back pressure Pbk is larger than the set pressure P3. Therefore, the safety ensuring pressure control valve 682 is always open (fully opened) during the lowering operation. That is, during a normal lowering operation, the safety ensuring pressure control valve 682 does not perform the same operation as the conventional external pilot type counter balance valve 784 (FIG. 16).

  In an emergency such as when the meter-in oil passage 30 is ruptured, the meter-in pressure Pmi can be equal to or lower than the set back pressure Pbk of the back pressure valve 81. At this time, when the meter-in pressure Pmi becomes equal to or lower than the set pressure P3 of the safety ensuring pressure control valve 682, the safety ensuring pressure control valve 682 closes the valve opening. Then, the meter-out flow rate Qmo decreases (becomes zero). As a result, the hydraulic motor 13 decelerates (emergency stop).

(Effect 5)
Next, the effect of the working hydraulic control device 501 shown in FIG. 15 will be described. The working hydraulic control device 501 includes a safety ensuring pressure control valve 682 provided on the upstream side of the branch point 51 with the regenerated oil passage 50 in the meter-out oil passage 40. The safety ensuring pressure control valve 682 closes the valve opening when the pressure in the meter-in oil passage 30 (more specifically, the meter-in pressure Pmi) is lower than the set pressure P3 of the safety ensuring pressure control valve 682. The set back pressure Pbk of the back pressure valve 81 is higher than the set pressure P3 of the safety ensuring pressure control valve 682.
Therefore, when the pressure in the meter-in oil passage 30 (meter-in pressure Pmi) becomes lower than the set pressure P3 of the safety ensuring pressure control valve 682 in the event of an emergency or failure such as when the meter-in oil passage 30 is damaged, the pressure control for ensuring safety is performed. The valve 682 closes the valve opening. Then, the flow rate of the meter-out oil passage 40 decreases, and the hydraulic motor 13 decelerates (or stops). As a result, it is possible to improve the safety at the time of emergency or failure.

  The safety ensuring pressure control valve 682 is provided on the upstream side of the branch point 51 with the regenerated oil passage 50 in the meter-out oil passage 40. Therefore, when the safety ensuring pressure control valve 682 closes the valve opening, the pressure oil does not flow into the regenerated oil passage 50. Therefore, the hydraulic motor 13 is surely decelerated.

(Other variations)
The working hydraulic control device 1 and the like can be variously modified.
For example, the arrangement of components in the circuit shown in FIG. 1 and the like and the connection of pipes may be as shown in the figure or may be changed as appropriate. For example, in FIG. 1, the pilot lines 64 and 73 are shown to branch from the meter-in oil passage 30 and the meter-out oil passage 40 in the direction switching valve 20, but the pilot lines 64 or 73 are connected to the direction switching valve 20. You may branch outside.

  Further, for example, in each of the above-described embodiments, the pressure oil supplied from the hydraulic pump 12 to the hydraulic motor 13 returns to the tank Ta1. However, the pressure oil discharged from the hydraulic motor 13 may be supplied to another hydraulic actuator or the like (not shown). Specifically, for example, a circuit in which the pressure oil supplied from the hydraulic pump 12 to the main winding motor (hydraulic motor 13) is further supplied to the auxiliary winding motor (not shown) and then returned to the tank Ta1 ( Series circuit).

1, 201, 301, 401, 501, 601 Working hydraulic control device 11 Engine (power source)
12 Hydraulic pump (meter-in flow control means)
13 Hydraulic motor (hydraulic actuator)
15 Suspended load (load)
16 Operation lever (operation means)
21a Bleed-off throttle (meter-in flow control means)
30 Meter-in oil passage 40 Meter-out oil passage 50 Reclaimed oil passage 51 Branch point 52 Junction point 53 Check valve 61 Meter-in throttle 62 Meter-in flow controller (meter-in flow control means)
71 Meter-out throttle 72 Meter-out flow controller 81 Back pressure valve 271 Meter-out valve (meter-out throttle)
682 Pressure control valve for ensuring safety

Claims (5)

A hydraulic pump;
A hydraulic actuator driven by pressure oil supplied from the hydraulic pump to move a load;
Operating means for operating the operating speed of the hydraulic actuator,
A working hydraulic control device for driving the hydraulic actuator so that the load moves in the direction of falling weight;
Meter-in flow rate control means for controlling the flow rate of the meter-in oil passage of the hydraulic actuator;
A meter-out throttle that is provided in a meter-out oil passage of the hydraulic actuator, and whose opening degree changes according to an operation amount of the operation means;
A meter-out flow controller that detects the differential pressure across the meter-out throttle and controls the flow rate of the meter-out oil passage so as to maintain the differential pressure across the meter at a constant set differential pressure;
A back pressure valve that is provided downstream of the meter-out throttle and downstream of the meter-out flow controller, and generates a set back pressure upstream of the valve;
A regeneration oil passage that branches from the meter-out oil passage on the upstream side of the back pressure valve and merges with the meter-in oil passage;
A check valve that is provided in the regenerated oil passage, and passes pressure oil only in the direction of flowing from the meter-out oil passage to the meter-in oil passage;
With
The meter-in flow rate control means controls the meter-in flow rate on the upstream side of the junction with the regenerated oil passage in the meter-in oil passage,
The meter-out flow controller controls a meter-out flow rate upstream of a branch point with the regenerated oil passage among the meter-out oil passages,
A working hydraulic control device that is controlled such that the meter-out flow rate is greater than the meter-in flow rate. A meter-in throttle provided in the meter-in oil passage,
The meter-in flow rate control unit includes a meter-in flow controller that detects a differential pressure across the meter-in throttle and controls the flow rate of the meter-in oil path so as to maintain the differential pressure across the meter at a constant set differential pressure. The working hydraulic control device according to 1. When the pressure in the meter-in oil passage increases, or
Instead of driving the hydraulic actuator so that the load moves in its own weight falling direction, when driving the hydraulic actuator so that the load moves in the direction opposite to its own weight falling direction,
The working hydraulic control device according to claim 1, wherein the working pressure control device controls the opening of the back pressure valve to open. When the power source of the hydraulic pump or the rotational speed of the hydraulic pump decreases,
The working hydraulic control device according to any one of claims 1 to 3, wherein the opening degree of the meter-out throttle is decreased, or the set differential pressure of the meter-out flow controller is decreased. A pressure control valve for ensuring safety provided on the upstream side of the branch point with the regenerated oil path in the meter-out oil path;
The safety ensuring pressure control valve closes the opening when the pressure in the meter-in oil passage is lower than the set pressure of the safety ensuring pressure control valve,
The working hydraulic control device according to any one of claims 1 to 4, wherein the set back pressure of the back pressure valve is higher than the set pressure of the safety ensuring pressure control valve.

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