JP6308859B2 - Hydraulic drive - Google Patents

Description

  The present invention relates to a hydraulic drive device for driving a work machine such as a hydraulic excavator, and more particularly to a closed circuit in which a single rod hydraulic cylinder and a first hydraulic oil control unit are connected in an annular manner through a flow path through which hydraulic oil flows. It is related with the hydraulic drive device which has.

  In recent years, in a working machine such as a hydraulic excavator, hydraulic fluid is directly sent from a hydraulic pump that is a pressure generation source to a single rod hydraulic cylinder that is a hydraulic actuator, and the single rod hydraulic cylinder is driven to perform predetermined work. There is known a so-called closed circuit hydraulic circuit in which the hydraulic oil after the operation is connected in a closed circuit shape so as to return directly to the single rod hydraulic cylinder. On the other hand, hydraulic fluid is sent from the hydraulic pump to the single-rod hydraulic cylinder through the throttle by the control valve for this closed circuit, and hydraulic fluid (return hydraulic fluid) that flows out from this single-rod hydraulic cylinder is used as hydraulic fluid. A hydraulic circuit called a so-called open circuit that discharges to a tank is also known. The closed circuit type hydraulic circuit has less pressure loss due to the throttle than the open circuit type hydraulic circuit, and the energy of the return hydraulic oil from the single rod hydraulic cylinder can be regenerated by the hydraulic pump. Excellent performance.

  Japanese Patent Application Laid-Open No. 2004-133620 discloses a conventional technique in which this type of closed circuit is combined. In this Patent Document 1, a first closed circuit in which a hydraulic pump is connected in a closed circuit shape is installed on a boom cylinder which is a single rod type hydraulic cylinder, and a separate hydraulic pump is installed on an arm cylinder. A second closed circuit connected in a closed circuit shape is provided. For the bucket cylinder, an open circuit with a separate hydraulic pump connected via a control valve is installed, and hydraulic fluid discharged from the open circuit hydraulic pump is supplied from the open circuit control valve. A distribution circuit that distributes to the boom cylinder and the arm cylinder is branched from the hydraulic pump side.

International Publication No. 2005/024246

  In the above-described closed circuit, when a single rod type hydraulic cylinder having different pressure receiving areas on the head side and the rod side is used, the flow rate of the hydraulic oil introduced or discharged to the head side and the operation to flow out or introduced from the rod side Since the oil flow rate is different, the hydraulic oil flow rate in the closed circuit becomes excessive or insufficient.

  In particular, in the conventional technique disclosed in Patent Document 1 described above, when one open circuit is provided in addition to a plurality of closed circuits such as the first and second closed circuits, and the one-rod hydraulic cylinder is driven to extend, The operation oil is additionally supplied from the open circuit connected to the head side, and the flow rate of the operation oil flowing through the closed circuit is adjusted to obtain a stable operation speed.

  In Patent Document 1, when the one-rod hydraulic cylinder is started to be extended, there is a time delay until the single-rod hydraulic cylinder is driven due to the influence of inertia, frictional resistance, hydraulic oil compression, and the like. In order to ensure the flow rate of the working oil (return oil) that returns from the single rod hydraulic cylinder to the hydraulic pump when this delay occurs, a charge pump is used. This charge pump requires a capacity to compensate the discharge flow rate of the hydraulic pump when the return oil flow rate immediately after the operation of the closed circuit hydraulic pump starts is insufficient, and therefore the capacity cannot be reduced. There is.

  The present invention has been made from the above-described prior art, and an object of the present invention is to provide a hydraulic drive device that can reduce the size of the charge pump and can eliminate the charge pump.

In order to achieve this object, the present invention provides a first hydraulic oil control unit capable of flowing hydraulic fluid in both directions, a piston, a head chamber into which hydraulic oil is introduced when the piston is extended, and the piston a first hydraulic cylinder having a rod chamber in which the working oil to the degenerate mode is introduced, prior Symbol a first hydraulic fluid control unit and the head chamber and the rod chamber is connected to the annular the flow path through which the hydraulic oil and closed circuit, the branch passage which is branched from the flow path of the first hydraulic fluid control unit connects the head chamber, branches the branch passage one end of which is connected to the hydraulic oil tank on the other side is connected A second hydraulic oil control unit that is provided in the flow channel, is provided in the branch flow channel, and controls the flow rate of the hydraulic oil between the branch channel and the hydraulic oil tank; and the hydraulic oil from the second hydraulic oil control unit a second hydraulic cylinder driven by the supply, the first film A bypass passage for bypassing the outflow Iruma oil controller, provided in the bypass passage, and a proportional valve for controlling the flow rate of the hydraulic fluid flowing through the bypass passage, said rod chamber and the first hydraulic oil control section And a pressure detection device provided in each of the flow paths connecting the head chamber, and a control device that controls the proportional valve based on the pressure detected by each pressure detection device,
The head chamber and the rod chamber have a predetermined pressure receiving area difference,
When the input signal for extending the first hydraulic cylinder is input, the control device is configured so that the speed of the extension operation of the first hydraulic cylinder becomes a predetermined target extension speed. And controlling the sum of the flow rate of the hydraulic oil supplied from the first hydraulic oil control unit and the flow rate of the hydraulic oil supplied from the second hydraulic oil control unit as the hydraulic flow rate to the head chamber, and the first The first hydraulic oil control unit and the second hydraulic oil so that the flow rate ratio supplied from the hydraulic oil control unit and the second hydraulic oil control unit is a flow rate ratio based on a pressure receiving area difference of the first hydraulic cylinder. Controlling the control unit, and controlling the proportional valve when the lower pressure value detected by the pressure detection device is equal to or lower than a predetermined pressure value, thereby connecting the bypass flow path to the high pressure side of the first hydraulic oil control unit this is the flow rate adjusting hydraulic oil flowing into the low-pressure side from It is characterized in.

In the present invention configured as described above, for example, when an operation signal for extending the first hydraulic cylinder is input, if the pressure on the inflow side of the first hydraulic oil control unit is equal to or lower than a predetermined pressure value, the bypass is performed. The flow rate of the hydraulic oil flowing from the high pressure side to the low pressure side of the first hydraulic oil control unit in the flow path is adjusted with a proportional valve. This prevents shortage of return hydraulic oil from the rod chamber of the first hydraulic cylinder due to inertia of the first hydraulic cylinder, frictional resistance, compression of hydraulic oil, etc. that occur at the start of the extension operation of the first hydraulic cylinder. be able to. Therefore, even with a configuration having a closed circuit, it is possible to reduce the size of a charge pump that has been conventionally used to compensate for the shortage of hydraulic oil, and thus to eliminate the charge pump. Moreover, since the proportional valve which can adjust the flow volume of hydraulic fluid is used, the control of the proportional valve by the control device can be facilitated. Therefore, it is possible to easily prevent a shortage of hydraulic fluid in the head chamber that occurs at the start of the extension operation of the first hydraulic cylinder.

According to the present invention , the return hydraulic oil from the rod chamber of the first hydraulic cylinder is insufficient due to the inertia of the first hydraulic cylinder, the frictional resistance, the compression of the hydraulic oil, etc. that occur at the start of the extension operation of the first hydraulic cylinder. Can be prevented. Therefore, even with a configuration having a closed circuit, it is possible to reduce the size of a charge pump that has been conventionally used to compensate for the shortage of hydraulic oil, and thus to eliminate the charge pump.

It is the schematic which shows the hydraulic shovel carrying the hydraulic drive device which concerns on 1st Embodiment of this invention. It is the schematic which shows the structure of the said hydraulic drive device. FIG. 6 is a time chart showing the behavior of the hydraulic drive device during boom raising operation operation, where (a) shows the operation amount of the operation lever 48a, (b) shows the state of the switching valve 27, and (c) shows the second hydraulic pump 10; (D) is the flow rate of the first hydraulic pump 9, (e) is the pressure of the flow path 14, (f) is the flow rate of the proportional valve 49, (g) is the pressure of the head chamber 1a of the boom cylinder 1, ( h) is the operating speed of the boom cylinder, and (i) is the flow rate of the check valve 21b. FIG. 6 is a time chart showing the behavior of the hydraulic drive device during the boom lowering operation, where (a) is the operation amount of the operation lever 48a, (b) is the pressure of the flow path 14, (c) is the flow rate of the proportional valve 49, ( d) is the pressure in the head chamber 1a of the boom cylinder 1, and (e) is the operating speed of the boom cylinder. It is a time chart which shows the behavior at the time of boom raising operation | movement operation of the hydraulic drive device which concerns on 2nd Embodiment of this invention, (a) is the operation amount of the operation lever 48a, (b) is the state of the switching valve 27, (c). Is the state of the switching valve 39, (d) is the flow rate of the second hydraulic pump 10, (e) is the flow rate of the third hydraulic pump 11, (f) is the flow rate of the first hydraulic pump 9, and (g) is (H) is the flow rate of the proportional valve 49, (i) is the pressure of the head chamber 1a of the boom cylinder 1, (j) is the operating speed of the boom cylinder 1, and (k) is the flow rate of the check valve 21b. It is. It is the schematic which shows the structure of the hydraulic drive unit which concerns on 4th Embodiment of this invention. It is the schematic which shows the structure of the hydraulic drive unit which concerns on 5th Embodiment of this invention. 4 is a time chart showing the behavior during boom raising operation when the extension start control by the hydraulic drive device according to the present invention is not applied, where (a) is the operation amount of the operation lever 48a, and (b) is the state of the switching valve 27. (C) is the flow rate of the second hydraulic pump 10, (d) is the flow rate of the first hydraulic pump 9, (e) is the pressure of the flow path 14, and (f) is the pressure of the head chamber 1a of the boom cylinder 1. , (G) is the operating speed of the boom cylinder 1, and (h) is the flow rate of the check valve 21b.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic diagram showing a hydraulic excavator 100 equipped with a hydraulic drive device according to a first embodiment of the present invention. FIG. 2 is a schematic diagram showing the configuration of the hydraulic drive device 107. In the first embodiment, in the hydraulic drive device 107 included in the excavator 100 shown in FIG. 1, a closed circuit A and open circuits B and C are provided as shown in FIG. As the hydraulic pump 10, a hydraulic pump having a bi-tilt swash plate mechanism whose discharge direction can be changed is used.

  Furthermore, a proportional valve 49 is provided in a bypass flow path 49a that connects both discharge ports of the first hydraulic pump 9, and when the boom cylinder 1 that is a single rod type hydraulic cylinder having a pressure receiving area difference starts to be extended, first for the open circuit B The hydraulic oil is replenished from the hydraulic oil tank 18 to the head chamber 1 a of the boom cylinder 1 by the second hydraulic pump 10. At the same time, the first hydraulic pump 9 for the closed circuit A is driven to move the hydraulic oil from the rod chamber 1b to the head chamber 1a. At this time, the proportional valve 49 is opened when the pressure on the suction side of the first hydraulic pump 9 falls below a predetermined pressure until the boom cylinder 1 starts to operate. As a result, the suction pressure of the first hydraulic pump 9 does not become negative, the charge flow rate can be suppressed, and the hydraulic excavator 100 including the hydraulic drive device 107 that can reduce the size of the charge pump 12 is obtained.

<Configuration>
A hydraulic excavator 100 will be described as an example of a work machine equipped with the hydraulic drive device 107 according to the first embodiment of the present invention shown in FIG. As shown in FIG. 1, the excavator 100 has a lower traveling body 103 provided with traveling devices 105 a and 105 b that are crawler-type traveling hydraulic actuators on both sides in the left-right direction, and can turn on the lower traveling body 103. And an upper turning body 102 as a main body attached thereto. A cab 101 on which an operator gets on is provided on the upper swing body 102. The upper turning body 102 can turn with respect to the lower traveling body 103 via a turning device 106 which is a turning hydraulic actuator.

  For example, a base end portion of a front work machine 104 that is an operating device for performing excavation work or the like is rotatably attached to the front side of the upper swing body 102. Here, the front side refers to the front direction of the cab 101 (the left direction in FIG. 1). The front work machine 104 includes a boom 2 having a base end portion connected to the front side of the upper swing body 102 so as to be able to move up and down. The boom 2 operates via a boom cylinder 1 that is a single rod hydraulic cylinder that is extended and contracted by supplying hydraulic oil (pressure oil). In the boom cylinder 1, the distal end portion of the rod 1 c is connected to the upper swing body 102, and the proximal end portion of the cylinder tube 1 d is connected to the boom 2.

  As shown in FIG. 2, the boom cylinder 1 is located on the base end side of the cylinder tube 1d and introduces hydraulic oil to press the piston 1e attached to the base end portion of the rod 1c to give a load by the hydraulic pressure. And a head chamber 1a which is a first hydraulic oil chamber on the side of extending and moving the rod 1c. The boom cylinder 1 is located on the distal end side of the cylinder tube 1d and introduces hydraulic oil to press the piston 1e to apply a load due to the hydraulic pressure, and the second hydraulic oil chamber on the side where the rod 1c is retracted. As a rod chamber 1b.

  The base end portion of the arm 4 is connected to the tip end portion of the boom 2 so as to move up and down. The arm 4 operates via an arm cylinder 3 that is a single rod hydraulic cylinder. The arm cylinder 3 connects the tip of the rod 3 c to the arm 4, and connects the cylinder tube 3 d of the arm cylinder 3 to the boom 2. As shown in FIG. 2, the arm cylinder 3 is located on the base end side of the cylinder tube 3d and pushes the piston 3e attached to the base end portion of the rod 3c by introducing hydraulic oil, thereby extending the rod 3c. The head chamber 3a is provided. The arm cylinder 3 includes a rod chamber 3b that is positioned on the distal end side of the cylinder tube 3d and presses the piston 3e by introducing hydraulic oil to move the rod 3c in a contracted manner.

  The base end portion of the bucket 6 is connected to the distal end portion of the arm 4 so as to be able to move up and down. The bucket 6 operates via a bucket cylinder 5 that is a single rod hydraulic cylinder driven by the supplied hydraulic oil. In the bucket cylinder 5, the distal end portion of the rod 5 c is connected to the bucket 6, and the proximal end portion of the cylinder tube 5 d is connected to the arm 4. The bucket cylinder 5 includes a head chamber 5a that is positioned on the proximal end side of the cylinder tube 5d and that pushes the piston 5e attached to the proximal end portion of the rod 5c by introducing hydraulic oil to extend and move the rod 5c. Further, the bucket cylinder 5 includes a rod chamber 5b that is located on the distal end side of the cylinder tube 5d and presses the piston 5e by introducing hydraulic oil to move the rod 5c in a contracted manner.

A hydraulic drive device 107 shown in FIG. 2 is a drive device for driving the excavator 100. The hydraulic drive device 107 is used to drive the turning device 106 and the traveling devices 105 a and 105 b in addition to the boom cylinder 1, the arm cylinder 3, and the bucket cylinder 5 that constitute the front work machine 104. The swivel device 106 and the traveling devices 105a and 105b are hydraulic motors that are rotationally driven by the supply of hydraulic oil. In FIG. 2, only the boom cylinder 1, the arm cylinder 3 and the bucket cylinder 5 are shown, and other components such as a hydraulic actuator which does not have a pressure receiving area difference between the swing device 106 and the traveling devices 105a and 105b are shown. The description is omitted.

  The hydraulic drive device 107 drives the boom cylinder 1, the arm cylinder 3, and the bucket cylinder 5, which are hydraulic actuators, in response to operation of operation levers 48 a to 48 d as operation devices installed in the cab 101. Here, the expansion / contraction operation of the boom cylinder 1, the arm cylinder 3, and the bucket cylinder 5, that is, the operation direction and the operation speed are instructed by the operation direction and operation amount of the operation levers 48a to 48d.

  Further, as shown in FIG. 2, the hydraulic drive device 107 includes an engine 7 that is a power source. The engine 7 is composed of, for example, a predetermined gear and is connected to a power transmission device 8 for distributing power. The power transmission device 8 includes a first hydraulic pump 9 for driving the boom cylinder 1, a second hydraulic pump 10 for driving the arm cylinder 3, and a third liquid for driving the bucket cylinder 5. Charge pump 12 for replenishing hydraulic oil (pressure oil) when the pressure difference between the pressure pump 11 and the flow path 13 and the flow path 14 sandwiching the first hydraulic pressure pump 9 becomes a predetermined pressure or less. Are connected to each other.

  The first to third hydraulic pumps 9 to 11 are used in closed circuits A to C to be described later, and it is necessary to control the driving of the boom cylinder 1, the arm cylinder 3 or the bucket linder 5 by changing the discharge direction of the hydraulic oil. Therefore, a bi-slanting swash plate mechanism (not shown) that can discharge hydraulic oil in both directions is provided. For this reason, the 1st thru | or 3rd hydraulic pumps 9-11 are equipped with a pair of inflow / outflow port which enables the inflow / outflow of the hydraulic fluid to both directions. The first to third hydraulic pumps 9 to 11 include regulators 9a to 11a for adjusting the tilt angle (tilt angle) of the bi-tilt swash plate constituting the bi-tilt swash plate mechanism. . The regulators 9a to 11a adjust the tilt angles of the swash plates of the corresponding first to third hydraulic pumps 9 to 11 in accordance with an operation signal output from the controller 47 as a control device, and the first to third It is a flow rate control part which controls the discharge direction and discharge flow rate of the hydraulic oil from the inflow / outflow port of any of the 3rd hydraulic pumps 9-11. The first to third hydraulic pumps 9 to 11 may be variable tilt mechanisms such as a tilt shaft mechanism and are not related to the swash plate mechanism.

  Here, the first hydraulic pump 9 is a closed circuit hydraulic pump as a first hydraulic oil control unit used as a closed circuit hydraulic oil inflow / outflow control unit connected to a closed circuit A described later. The second and third hydraulic pumps 10 and 11 are open circuit hydraulic pumps as second hydraulic oil control units used as open circuit hydraulic oil inflow / outflow control units connected to open circuits B and C, which will be described later. is there.

  The flow path 13 is connected to one outflow / inflow port of the first hydraulic pump 9, and the flow path 14 is connected to the other outflow / inflow port. The flow path 13 is connected to the head chamber 1 a of the boom cylinder 1 via the flow path 15, and the flow path 14 is connected to the rod chamber 1 b of the boom cylinder 1 via the flow path 16. Therefore, the first hydraulic pump 9 constitutes a closed circuit A connected to the boom cylinder 1 through the flow paths 13 to 16 in a ring shape, that is, in a closed circuit shape. The boom cylinder 1 is configured to expand and contract by supplying hydraulic oil from the first hydraulic pump 9, and the expansion and contraction direction depends on the supply direction of hydraulic oil.

Pressure sensors 17a and 17b are connected to the flow paths 13 and 14 as pressure detection devices for detecting the hydraulic pressure of the flow paths 13 and 14. The pressure sensors 17 a and 17 b measure the discharge pressure and suction pressure of the first hydraulic pump 9, and output the measured discharge pressure and suction pressure information to the controller 47. The flow paths 15 and 16 are reliefs for protecting the circuit by releasing the hydraulic oil to the hydraulic oil tank 18 when the hydraulic pressure (flow path pressure) of the flow paths 15 and 16 exceeds a predetermined pressure. The flushing valve 20 for discharging the surplus (surplus oil) of the hydraulic oil passing through the valves 19a and 19b and the flow paths 15 and 16 to the hydraulic oil tank 18 is connected. A relief valve 20 a for adjusting the discharge pressure from the flushing valve 20 to the hydraulic oil tank 18 is connected to the flow path connecting the flushing valve 20 and the hydraulic oil tank 18. The relief pressure P _r2 of the relief valve 20a is set to be equal to or higher than the relief pressure P _r1 of the charge relief valve 22 described later, that is, P _r2 ≧ P _r1 .

  Charging check valves 21 a and 21 b for supplying hydraulic oil discharged from the charge pump 12 to the flow paths 13 and 14 on the lower pressure side of the flow paths 13 and 14 are provided at the discharge port of the charge pump 12. Connected. The suction port of the charge pump 12 communicates with the hydraulic oil tank 18. A charge relief valve 22 for adjusting the discharge pressure (charge pressure) of the hydraulic oil discharged from the charge pump 12 is connected to the flow path between the charge pump 12 and the charge check valves 21a and 21b. .

  One inflow / outflow port of the second hydraulic pump 10 communicates with the hydraulic oil tank 18 through the flow path 23, and the other outflow / inflow port is connected to the switching valves 25 to 27 through the flow path 24. doing. The switching valves 25 to 27 are configured to switch between release and shut-off of the flow path in accordance with a command value from the controller 47, and are in a shut-off state when no operation signal is output from the controller 47. The controller 47 controls the switching valves 25 to 27 so as not to be in a conductive state that allows the hydraulic oil to pass through at the same time. The second hydraulic pump 10 is connected via a flow path 24 and a switching valve 25 to a proportional switching valve 30 that is a control valve. The proportional switching valve 30 is connected to the head chamber 3a and the rod chamber 3b of the arm cylinder 3 via flow paths 31 and 32, and the proportional switching valve 30 is communicated with the hydraulic oil tank 18 to constitute an open circuit B. . Therefore, the arm cylinder 3 is configured to expand and contract by supplying hydraulic oil from the proportional switching valve 30, and the expansion and contraction direction depends on the hydraulic oil supply direction.

  The first branch flow path 27 a connected to the switching valve 27 is connected to the branch path 15 a connected to the flow path 15 of the closed circuit A. The switching valve 27 is connected to the head chamber 1a of the boom cylinder 1 via the first branch flow path 27a and the branch path 15a. The second hydraulic pump 10 controls the flow rate of the hydraulic oil between the branch passage 15 a and the hydraulic oil tank 18 by controlling the switching valve 27, and the flow rate of the hydraulic oil flowing into and out of the head chamber 1 a of the boom cylinder 1. Can be adjusted. A relief valve that protects the flow path 24 by allowing the hydraulic oil in the flow path 24 to escape to the hydraulic oil tank 18 when the circuit pressure (working hydraulic pressure) of the flow path 24 exceeds a predetermined pressure. 28 is connected.

  The switching valve 25 is connected to the proportional switching valve 30 via a check valve 29. The proportional switching valve 30 is supplied to the arm cylinder 3 by connecting the check valve 29 to the flow path 31 or the flow path 32 and adjusting the opening degree of the proportional control valve 30 according to the command value from the controller 47. Adjust the hydraulic fluid flow rate. Counter balance valves 33 a and 33 b for suppressing the falling of the weight of the arm cylinder 3 are connected to the flow paths 31 and 32. The flow paths 31 and 32 are provided with relief valves 34a for releasing the hydraulic oil to the hydraulic oil tank 18 and protecting the circuit when the hydraulic pressure of the flow paths 31 and 32 exceeds a predetermined pressure. 34b is connected. The switching valve 26 is connected to a proportional switching valve 42 described later via a check valve 41.

  One inflow / outflow port of the third hydraulic pump 11 communicates with the hydraulic oil tank 18 through the flow path 35, and the other outflow / inflow port is connected to the switching valves 37 to 39 through the flow path 36. doing. The switching valves 37 to 39 are configured to switch between release and shut-off of the flow path according to a command value from the controller 47, and are in a shut-off state when no operation signal is output from the controller 47. The controller 47 controls the switching valves 37 to 39 so as not to be in a conductive state that allows the hydraulic oil to pass through at the same time. The third hydraulic pump 11 is connected to a proportional switching valve 42 that is a control valve via a flow path 36 and a switching valve 37. The proportional switching valve 42 is connected to the head chamber 5a and the rod chamber 5b of the bucket cylinder 5 via the flow path 43 and the flow path 44, and the proportional switching valve 42 is connected to the hydraulic oil tank 18 to form an open circuit C. ing. Therefore, the bucket cylinder 5 is configured to expand and contract by supplying hydraulic oil from the proportional switching valve 42, and the expansion and contraction direction depends on the supply direction of hydraulic oil.

  The second branch flow path 39 a connected to the switching valve 39 is connected to the branch path 15 a connected to the flow path 15 of the closed circuit A. The switching valve 39 is connected to the head chamber 1a of the boom cylinder 1 via the second branch channel 39a and the branch channel 15a. The third hydraulic pump 11 controls the flow rate of hydraulic oil flowing into and out of the head chamber 1a of the boom cylinder 1 by controlling the flow rate of hydraulic fluid between the branch passage 15a and the hydraulic oil tank 18 by controlling the switching valve 39. Adjustable. A relief valve 40 is connected to the flow path 36 to release the hydraulic oil in the flow path 36 to the hydraulic oil tank 18 and protect the flow path 36 when the circuit pressure of the flow path 36 exceeds a predetermined pressure. ing.

  The switching valve 37 is connected to the proportional switching valve 42 via the check valve 41. The proportional switching valve 42 is supplied to the bucket cylinder 5 by connecting the check valve 41 to the flow path 43 or the flow path 44 in accordance with a command value from the controller 47 and adjusting the opening degree of the proportional control valve 42. Adjust the hydraulic fluid flow rate. Counter balance valves 45a and 45b are connected to the flow paths 43 and 44 for suppressing the falling of the weight of the bucket cylinder 5 by its own weight. The flow paths 43 and 44 are provided with relief valves 46a for protecting the circuit by escaping the hydraulic oil to the hydraulic oil tank 18 when the hydraulic pressure of the flow paths 43 and 44 exceeds a predetermined pressure. 46b is connected. The switching valve 38 is connected to the proportional switching valve 30 via the check valve 29.

  Further, a proportional valve 49 serving as a flow rate adjusting unit is connected to a bypass channel 49a that connects the channel 13 and the channel 14 of the closed circuit A and bypasses the channel. The bypass flow path 49 a is a regeneration flow path that connects between the flow in and out of the first hydraulic pump 9. The proportional valve 49 adjusts the opening degree of the valve in accordance with a command from the controller 47, and the bypass flows from the high pressure side flow paths 13, 14 of the flow paths 13, 14 to the low pressure side flow paths 14, 13. The flow rate of the hydraulic oil in the flow path 49a is adjusted.

  The controller 47 includes command values for the expansion and contraction directions and speeds of the boom cylinder 1, the arm cylinder 3 and the bucket cylinder 5 from the operation levers 48a to 48d, and command values for the rotation direction and the rotation speed of the turning device 106 and the traveling devices 105a and 105b. And the regulators 9a to 11a of the first to third hydraulic pumps 9 to 11, the switching valves 25 to 27, 37 to 39, the proportional switching valves 30, 42, and the like based on various sensor information in the hydraulic drive device 107. The proportional valve 49 is controlled. The operation levers 48 a to 48 c give the controller 47 the command values for the expansion / contraction direction and speed of the boom cylinder 1, arm cylinder 3 or bucket cylinder 5. Note that the operation lever 48 d gives a command value for the rotation direction and rotation speed of the turning device 106 to the controller 47. The controller 47 also includes an operation lever (not shown) that gives the controller 47 command values for the rotation direction and the rotation speed of the traveling devices 105a and 105b.

  Further, pressure information detected by the pressure sensors 17a and 17b is input to the controller 47. The controller 47 controls the opening of the proportional valve 49 when the detected values of the pressure sensors 17a and 17b on the low pressure value side are equal to or lower than a predetermined pressure value, so that the first hydraulic pump 9 is controlled at the time of starting to extend a predetermined flow rate of hydraulic fluid from the high-pressure side flow paths 13 and 14 connected to 9 to the low-pressure side flow paths 14 and 13. Therefore, when the pressure of the flow path 14 on the inflow side of the first hydraulic pump 9 is equal to or lower than a predetermined pressure value by the pressure sensors 17a and 17b, the controller 47, and the proportional valve 49, the high pressure side via the bypass flow path 49a. The flow rate adjusting unit 60 is configured to allow the hydraulic oil to pass from the flow path 13 to the low pressure side flow path 14.

  Furthermore, as the extension start control, when the operation lever 48a operates the rod 1c of the boom cylinder 1 in the extending direction and the operation signal is input to the controller 47, the first hydraulic pump on the closed circuit A side is operated. 9 is a target for the head chamber 1a that is required for the sum of the hydraulic fluid flow supplied by the hydraulic fluid flow 9 to be supplied by the second hydraulic pump 10 on the open circuit B side to obtain a predetermined target extension speed. The flow rate ratio between the flow rate of hydraulic fluid supplied by the first hydraulic pump 9 and the flow rate of hydraulic fluid supplied by the second hydraulic pump 10 is a flow rate ratio based on the pressure receiving area difference of the boom cylinder 1. The first and second hydraulic pumps 9 and 10 are controlled so that At the same time, when the detected value of the pressure sensor 17a, 17b on the low pressure value side is equal to or lower than a predetermined pressure value, the opening of the proportional valve 49 is controlled and the first hydraulic pump 9 is controlled. The hydraulic oil of a predetermined flow rate is passed from the connected high-pressure side flow paths 13 and 14 to the low-pressure side flow paths 14 and 13, and the supply amount of the hydraulic oil from the second hydraulic pump 10 on the open circuit B side is proportional to the proportional valve. The amount of hydraulic oil passing through 49 increases as much as the flow rate.

<Action>
Next, the operation of the hydraulic drive device 107 according to the first embodiment (when extension start control is applied) will be described.

(Non-operation)
When not in operation, the controller 47 controls each of the first to third hydraulic pumps 9 to 11 to the minimum tilt angle via the regulators 9a to 11a, and the switching valves 25 to 27, 37 to 39 are proportional. All of the switching valves 30 and 42 and the proportional valve 49 are closed, and the boom cylinder 1, the arm cylinder 3 and the bucket cylinder 5 are held in a stopped state, respectively.

(When boom is raised alone)
FIGS. 3A and 3B are time charts showing the behavior of the hydraulic drive device 105 during the boom raising operation. FIG. 3A shows the operation amount of the operation lever 48a, FIG. 3B shows the state of the switching valve 27, and FIG. (D) is the flow rate of the first hydraulic pump 9, (e) is the pressure of the flow path 14, (f) is the flow rate of the proportional valve 49, and (g) is the pressure of the head chamber of the boom cylinder. , (H) is the operating speed of the boom cylinder, and (i) is the flow rate of the check valve 21b. That is, FIG. 3 shows the behavior of each element during the extension operation of the boom cylinder 1 when the extension start time control according to the present invention is applied.

  The operation amount of the operation lever 48 a shown in FIG. 3A and the pressure of the flow path 14 shown in FIG. 3E, that is, the pressure value detected by the pressure sensor 17 b are input values to the controller 47. 3 (b), the flow rate of the second hydraulic pump 10 shown in FIG. 3 (c), the flow rate of the first hydraulic pump 9 shown in FIG. 3 (d), and FIG. The flow rate of the proportional valve 49 shown in (f) is a control target controlled by the controller 47. The pressure in the head chamber 1a of the boom cylinder 1 shown in FIG. 3 (g), the operating speed of the boom cylinder 1 shown in FIG. 3 (h), and the flow rate of the check valve 21b shown in FIG. It is an element affected by

When boom raising operation procedure, over time t1 to t4, when changing the operation amount of the operation lever 48a to 0 to X _1, at time t4, to the operation amount _{X 1} of the operating lever 48a, the controller 47, the first liquid as the sum of the discharge flow rate _{Q op1} discharge flow rate _{Q cp1} the second hydraulic pump 10 of the pressure pump 9 becomes equal to the target hydraulic fluid flow rate based on the operation amount _{X 1,} these _{Q cp1} and _{Q op1} regulator 9a, 10a Control with. At the same time, the controller 47 determines the area ratio A _a1 : A _a2 of the pressure receiving area A _a1 of the head chamber 1 a of the boom cylinder 1 and the pressure receiving area A _a2 of the rod chamber ₁ b, the first and second hydraulic pumps 9, 10, and flow ratio of 2 hydraulic pump _{10 (Q cp1 + Q op1)} : as the _{Q cp1} becomes _equal, determines the _{Q cp1} and _{Q op1.} When the operation speed of the boom cylinder 1 is in the steady region, the controller 47 maintains the ratio of the discharge flow rate of the first hydraulic pump 9 and the discharge flow rate of the second hydraulic pump 10 at Q _cp1 : Q _op1. The regulators 9a and 10a are controlled.

  Specifically, when the operation lever 48a is operated in the direction in which the boom cylinder 1 is extended at time t1, the controller 47 controls the regulators 9a and 10a of the first and second hydraulic pumps 9 and 10. The swash plates of the first and second hydraulic pumps 9 and 10 are tilted. At time t1, the controller 47 simultaneously controls the switching valve 27 to open and allow the hydraulic oil to pass through, simultaneously with the discharge of the hydraulic oil from the first and second hydraulic pumps 9 and 10.

  That is, at time t1 to t2, the controller 47 starts discharging the hydraulic oil from the second hydraulic pump 10, but due to the influence of the inertia of the boom cylinder 1, the frictional resistance, the compressibility of the hydraulic oil, etc., the head chamber 1a There is a time delay before the pressure increases. As a result, a time delay occurs until the actual operating speed of the boom cylinder 1 reaches the operating speed corresponding to the flow rate of the hydraulic oil discharged from the first and second hydraulic pumps 9 and 10. At this time, the discharge flow rate of the second hydraulic pump 10 may be increased with respect to the input of the operation lever 48a in consideration of the inertia of the boom cylinder 1, the frictional resistance, the compressibility of the hydraulic oil, and the like. That is, the discharge flow rate of the second hydraulic pump 10 is slightly increased with respect to the command value based on the operation amount of the operation lever 48a over a predetermined predetermined time, thereby compressing the hydraulic oil. The operation delay due to can be reduced.

When the actual operating speed of the boom cylinder 1 is slower than the operating speed calculated from the total discharge flow rate of the first and second hydraulic pumps 9 and 10, the outflow flow rate Q _Br from the rod chamber 1b of the boom cylinder 1 (Not shown) is less than the suction flow rate Q _cp sucked into the first hydraulic pump 9. Therefore, since the hydraulic oil in the flow paths 14 and 16 expands and the hydraulic pressure (pressure) passing through the flow paths 14 and 16 decreases, the pressure in the flow paths 14 and 16 decreases to _Pr4 at time t2. To do. Further, at time t2, when the controller 47 detects that the pressure value detected by the low-pressure side pressure sensor 17b is equal to or lower than _Pr4 , the controller 47 opens the proportional valve 49, and the pressure detected by the pressure sensor 17b. Is supplied from the flow path 13 to the flow path 14.

When the pressure in the flow path 14 decreases to _Pr3 at time t3, the hydraulic fluid flow rate of the proportional valve 49 becomes the maximum _Qcp1 . At time t1 to t2, the pressure of the passage 14 when lower than set discharge pressure _{P r2} of the charge pump 12, a charge pump 12 through a check valve 21b is hydraulic oil flows into the channel 14 for discharging. When the pressure in the flow path 14 decreases to _Pr3 at time t3, the flow rate of the check valve 21b becomes _Qc2 . At time t <b> 3 to t <b> 4, the controller 47 opens the proportional valve 49 to allow the hydraulic oil to pass, and the pressure of the flow path 14 increases due to the flow of the hydraulic oil from the flow path 13 to the flow path 14.

At time t5, when the operating pressure of the flow path 14 reaches _Pr4 based on the detection value of the pressure sensor 17b, the controller 47 closes and shuts off the proportional valve 49 and sets the flow rate of the flow path 14 to zero. . At time t6, the pressure in the flow path 14 reaches the _{P r1,} the flow rate of the check valve 21b becomes zero. In time t7, the the pressure of the head chamber 1a of the boom cylinder 1 reaches _{P bh2,} increased operating speed of the boom cylinder 1, an increase in the outflow flow rate _{Q Br} from the rod chamber 1b of the boom cylinder 1, the passage 14 Increases to _Pr2 . At time t8, the actual operating speed of the boom cylinder 1 reaches the target speed _Vb1 .

(Boom lowering only operation)
FIG. 4 is a time chart showing the behavior of the hydraulic drive device 107 during the boom lowering operation. (A) is the operation amount of the operation lever 48a, (b) is the pressure in the flow path 14, and (c) is the proportional valve 49. (D) is the pressure in the head chamber 1 a of the boom cylinder 1, and (e) is the operating speed of the boom cylinder 1. The parameters shown in FIGS. 4A to 4E are the parameters shown in FIGS. 3A, 3E to 3H.

During boom-down operation procedure, over time t1 to t2, when changing the operating amount of the operating lever 48a to 0 _{to-X 1,} at time t2, to the operation amount -X ₁ of the operation lever 48a, the controller 47 is bypassed The opening degree of the proportional valve 49 is controlled so that the flow rate of hydraulic oil passing through the flow path 49a is (Q _cp1 + Q _op1 ). That is, at time t1, when the operation lever 48a is operated in a direction in which the boom cylinder 1 is contracted, the controller 47 controls the opening degree of the proportional valve 49 to flow hydraulic oil from the flow path 13 to the flow path 14.

At time t1 to t2, when the hydraulic oil starts to flow from the flow path 13 to the flow path 14 by the proportional valve 49, the pressure in the head chamber 1a of the boom cylinder 1 decreases and the pressure in the flow path 14 increases. . Here, at time t2, the flow rate Q _Bh (not shown) of hydraulic fluid flowing out from the head chamber 1a of the boom cylinder 1 is equal to the flow rate of hydraulic fluid passing through the proportional valve 49 (Q _cp1 + Q _op1 ). Become. On the other hand, the inflow flow rate _QBr (not shown) of the hydraulic oil flowing into the rod chamber 1b of the boom cylinder 1 becomes _Qcp1 due to the influence of the pressure receiving area difference described above.

Thus, _{Q op1} of flow rate of the hydraulic oil passing through the proportional valve 49 _(Q cp1 ₊ Q _op1) becomes surplus. The surplus Q _op1 returns to the hydraulic oil tank 18 via the flushing valve 20 shown in FIG. At this time, the discharge pressure of the hydraulic oil from the flushing valve becomes _Pr2 by the relief valve 20a provided on the flow path connecting the flushing valve 20 and the hydraulic oil tank 18. As a result, as shown in FIG. 5, at time t2, the actual operating speed of the pressure of the passage 14 _{P r2,} and the boom cylinder 1 reaches the target velocity _{-V b1.}

<When there is no control at the start of expansion>
Next, the operation when the extension start control by the hydraulic drive device 107 according to the first embodiment is not applied will be described.

  FIG. 8 is a time chart showing the behavior at the time of boom raising operation when the extension start control by the hydraulic drive device 107 according to the present invention is not applied, where (a) is the operation amount of the operation lever 48a, (b) is The state of the switching valve 27, (c) is the flow rate of the second hydraulic pump 10, (d) is the flow rate of the first hydraulic pressure pump 9, (e) is the pressure of the flow path 14, and (f) is the boom cylinder 1. The pressure in the head chamber 1a, (g) is the operating speed of the boom cylinder 1, and (h) is the flow rate of the check valve 21b. The parameters shown in FIGS. 8A to 8G are the same as the parameters shown in FIGS. 3A to 3G.

When boom raising operation operation, as shown in FIG. 8, over the time t1 to t3, changes the operation amount of the operation lever 48a from 0 to _{X 1.} At this time, when the operation lever 48a is operated in the direction in which the boom cylinder 1 is extended at time t1, the controller 47 controls the regulator 9a of the first hydraulic pump 9 so that the first hydraulic pump 9 Defeat the swash plate. Then, the controller 47 controls the regulator 9a so that the discharge flow rate of the first hydraulic pump 9 becomes the maximum discharge flow rate Q _{cp1 at} time t2.

When the operation amount of the operation lever 48a increases from time t2 to time t3, the controller 47 controls the regulator 10a of the second hydraulic pump 10 to tilt the swash plate of the second hydraulic pump 10, and the second The hydraulic oil is discharged from the hydraulic pump 10. At time t3, when the operation amount of the operation lever 48a reaches _{X 1,} controller 47, discharge flow rate of the second hydraulic pump 10 to control the regulator 10a so that the maximum discharge flow rate _{Q op1.} At time t2, the controller 47 controls the switching valve 27 to allow the hydraulic oil to pass through at the same time as the hydraulic oil is discharged from the second hydraulic pump 10.

  That is, at time t1 to t3, the controller 47 starts discharging the hydraulic oil from the first and second hydraulic pumps 9 and 10, but the inertia of the boom cylinder 1, the friction resistance, the compressibility of the hydraulic oil, etc. Due to the influence, a time delay occurs until the pressure of the head chamber 1a of the boom cylinder 1 increases. Thereby, there is a time delay until the actual operation speed of the boom cylinder 1 becomes the operation speed according to the discharge flow rate from the first and second hydraulic pumps 9 and 10.

When the actual operating speed of the boom cylinder 1 is slower than the operating speed calculated from the total discharge flow rate of the first and second hydraulic pumps 9 and 10, the outflow flow rate Q _Br from the rod chamber 1b of the boom cylinder 1 However, since the suction flow rate Q _cp of the first hydraulic pump 9 is smaller, the hydraulic oil in the flow paths 14 and 16 expands, resulting in a pressure drop. For this reason, at the time t2, the pressure of the flow paths 14 and 16 falls to the pressure value _Pr3 .

Furthermore, supplies at time t1 to t2, the pressure of the passage 14 is lower than the set discharge pressure _{P r1} of the charge pump 12, a hydraulic oil charge pump 12 is discharged from the check valve 21b into the channel 14. At time t2, the flow rate of the check valve 21b becomes _Qc1 . At time t2, the difference between the target speed of the boom cylinder 1 calculated from the total discharge flow rate of the first and second hydraulic pumps 9 and 10 and the actual operating speed of the boom cylinder 1 is large. outflow rate _{Q Br} from the rod chamber 1b is significantly less than the suction flow rate _{Q cp} first hydraulic pump 9 sucks. For this reason, at time t2, the suction flow rate of the first hydraulic pump 9 must be secured by the flow rate of the check valve 21b, and the flow rate Q _c1 of the check valve 21b is equal to the discharge flow rate Q of the first hydraulic pump 9. It becomes almost the same amount as _cp1 .

When the pressure in the head chamber 1a of the boom cylinder 1 reaches _Pbh2 at time t4, the force generated in the boom cylinder 1 is stabilized and the operating speed of the boom cylinder 1 is increased. This increases the outflow rate Q _Br from the rod chamber 1b of the boom cylinder 1, the pressure of the passage 14 is increased, the flow rate of the check valve 21b decreases. When the pressure in the flow path 14 becomes equal to or higher than the pressure value P _{r1 at} time t5, the flow rate of the check valve 21b becomes zero. Finally, the actual operating speed of the boom cylinder 1 becomes the target speed _Vb1 , and the pressure in the flow path 14 is also stabilized at _Pr1 .

<Effect>
As described above, when the extension start control by the hydraulic drive device 107 according to the first embodiment of the present invention is not applied, immediately after the operation of the boom cylinder 1 starts, the inertia of the boom cylinder 1, the friction resistance, and the hydraulic oil due to the influence of compression, etc., and an outlet flow rate _{Q Br} of the hydraulic oil flowing out from the rod chamber 1b of the boom cylinder 1, the _{Q cp} relative relationship _{Q Br} and suction flow rate _{Q cp} first hydraulic pump 9 sucks Significantly less, Q _Br > Q _cp . Therefore, since the suction flow rate Q _cp of the first hydraulic pump 9 must be supplied from the charge pump 12, the charge pump 12 that can discharge the same volume as the first hydraulic pump 9 is required. In other words, when the boom cylinder 1 starts to extend, the pressure on the suction side of the first hydraulic pump 9 is reduced to a certain level or higher using the charge pump 12 until the boom cylinder 1 starts operating. Therefore, the charge pump 12 having the same capacity as that of the first hydraulic pump 9 is required, and the charge pump 12 is increased in size.

On the other hand, when the extension start control by the hydraulic drive device 107 according to the first embodiment of the present invention is applied, the flow path 14 on the suction side of the first hydraulic pump 9 immediately after the operation of the boom cylinder 1 is started. When the pressure decreases, the controller 47 opens the proportional valve 49 based on the value detected by the pressure sensor 17b to flow hydraulic oil from the flow path 13 to the flow path 14, and the first hydraulic pump 9 The suction flow rate Q _cp to be sucked is secured from the flow path 13. Therefore, compared with the case where the above-described extension start control is not applied, the flow rate of hydraulic oil supplied from the charge pump 12 to the suction side of the first hydraulic pump 9 via the flow path 14 can be greatly reduced.

  Therefore, even when the boom cylinder 1 is driven by the closed circuit A, the hydraulic fluid in the head chamber 1a is insufficient due to the opening / closing control of the proportional valve 49 by the controller based on the pressure sensor 17b. Can be prevented. For this reason, it is possible to reduce the size of the charge pump 12 conventionally used to make up for the shortage of hydraulic oil, to make the charge pump 12 with a smaller discharge capacity, and thus to eliminate the charge pump 1.

Further, at the time of boom raising operation, the sum of the discharge flow rate Q _cp1 of the first hydraulic pump 9 and the discharge flow rate Q _op1 of the second hydraulic pump 10 becomes the target hydraulic oil flow rate based on the operation amount X ₁ . These Q _cp1 and Q _op1 are controlled by the regulators 9a and 10a, and at the same time, the area ratio A _a1 : A _a2 of the pressure receiving area A _a1 of the head chamber 1 a of the boom cylinder 1 and the pressure receiving area A _a2 of the rod chamber ₁ b, and the first Further, Q _cp1 and Q _op1 are determined so that the flow rate ratio (Q _cp1 + Q _op1 ): Q _cp1 between the second hydraulic pumps 9 and 10 and the second hydraulic pump 10 becomes equal. As a result, it is possible to ensure a balance between the flow rate of hydraulic oil introduced into the head chamber 1a of the boom cylinder 1 and the flow rate of hydraulic oil flowing out from the rod chamber 1b, and efficiently eliminates the shortage of hydraulic fluid based on the pressure receiving area difference of the boom cylinder 1. Can be resolved. Therefore, the extension operation of the boom cylinder 1 can be made smooth and the operability can be improved.

Further, when the boom lowering operation is performed, the controller 47 controls the opening degree of the proportional valve 49 so that the flow rate of the hydraulic oil passing through the bypass passage 49a becomes (Q _cp1 + Q _op1 ). As a result, the pressure in the flow path 14 increases as the pressure in the head chamber 1a of the boom cylinder 1 decreases, and the outflow rate Q _Bh of the hydraulic oil flowing out from the head chamber 1a of the boom cylinder 1 passes through the proportional valve 49. flow rate equal to _(Q cp1 ₊ Q _op1) next to the hydraulic oil, inlet flow _{Q Br} of hydraulic oil flowing into the rod chamber 1b of the boom cylinder 1, the _{Q cp1} by the effect of the pressure receiving area difference of the boom cylinder 1. Therefore, the boom lowering operation can be performed without consuming energy for driving the first and second hydraulic pumps 9 and 10 by controlling the opening degree of the proportional valve 49 during the boom lowering operation.

[Second Embodiment]
5A and 5B are time charts showing the behavior of the hydraulic drive device 107 according to the second embodiment of the present invention during the boom raising operation. FIG. 5A is an operation amount of the operation lever 48a, and FIG. (C) is the state of the switching valve 39, (d) is the flow rate of the second hydraulic pump 10, (e) is the flow rate of the third hydraulic pump 11, and (f) is the flow rate of the first hydraulic pump 9. (G) is the pressure of the flow path 14, (h) is the flow rate of the proportional valve 49, (i) is the pressure of the head chamber 1a of the boom cylinder 1, (j) is the operating speed of the boom cylinder 1, and (k) is This is the flow rate of the check valve 21b.

  The second embodiment differs from the first embodiment described above in that the first embodiment uses only the second hydraulic pump 10 at the start of the boom raising single operation, whereas the second embodiment The second and third hydraulic pumps 10 and 11 are respectively used for starting the boom raising single operation. In the second embodiment, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals.

(When boom is raised alone)
The parameters shown in FIGS. 5A to 5K are the parameters shown in FIGS. 3A to 3G, the state of the switching valve 39 shown in FIG. 5C, and the parameters shown in FIG. The flow rate of the third hydraulic pump 11 shown in e) is added. The operation of the switching valve 39 shown in FIG. 5C and the flow rate of the third hydraulic pump 11 shown in FIG. 5E are controlled objects controlled by the controller 47.

When boom raising operation procedure, over time t1 to t3, when changing the operation amount of the operation lever 48a to 0 to X _1, at time t4, to the operation amount _{X 1} of the operating lever 48a, the controller 47, the first liquid The regulators 9a and 10a are controlled so that the discharge flow rate of the pressure pump 9 is Q _cp1 and the discharge flow rate of the second hydraulic pump 10 is Q _op1 . At the same time, the controller 47 has an area ratio A _a1 : A _a2 of the pressure receiving area A _a1 of the head chamber 1 a of the boom cylinder 1 and the pressure receiving area A _a2 of the rod chamber ₁ b, the first and second hydraulic pumps 9, 10, and flow ratio of 2 hydraulic pump _{10 (Q cp1 + Q op1)} : as the _{Q cp1} becomes _equal, determines the _{Q cp1} and _{Q op1.} When the operation speed of the boom cylinder 1 is in the steady region, the controller 47 maintains the ratio of the discharge flow rate of the first hydraulic pump 9 and the discharge flow rate of the second hydraulic pump 10 at Q _cp1 : Q _op1. The regulators 9a and 10a are controlled.

  Specifically, when the operation lever 48a is operated in the direction in which the boom cylinder 1 is extended at time t1, the controller 47 controls the regulators 9a and 10a of the first and second hydraulic pumps 9 and 10, respectively. The swash plates of the first and second hydraulic pumps 9 and 10 are tilted. At time t1, the controller 47 simultaneously controls the switching valve 27 to open and allow the hydraulic oil to pass through, simultaneously with the discharge of the hydraulic oil from the first and second hydraulic pumps 9 and 10.

  At time t1 to t2, the controller 47 starts discharging the hydraulic oil from the second hydraulic pump 10, but due to the effects of the inertia of the boom cylinder 1, the frictional resistance, the compressibility of the hydraulic oil, and the like, There is a time delay before the pressure rises. As a result, a time delay occurs until the actual operating speed of the boom cylinder 1 becomes the operating speed corresponding to the flow rate of hydraulic oil discharged from the second hydraulic pump 10. At this time, the discharge flow rate of the second hydraulic pump 10 may be increased with respect to the input of the operation lever 48a in consideration of the inertia of the boom cylinder 1, the frictional resistance, the compressibility of the hydraulic oil, and the like. That is, the discharge flow rate of the second hydraulic pump 10 is slightly increased with respect to the command value based on the operation amount of the operation lever 48a over a predetermined predetermined time, thereby compressing the hydraulic oil. The operation delay due to can be reduced.

When the actual operation speed of the boom cylinder 1 is slower than the operation speed calculated from the total discharge flow rate of the first and second hydraulic pumps 9 and 10, the outflow rate Q _Br of the rod chamber 1b of the boom cylinder 1 is The suction flow rate Q _cp of the first hydraulic pump 9 is smaller. Therefore, since the hydraulic oil in the flow paths 14 and 16 expands and the pressure decreases, the pressure of the flow paths 14 and 16 decreases to _Pr4 at time t2. Further, at time t2, when the pressure sensor 17b on the low pressure side detects a pressure value equal to or lower than _Pr4 , the controller 47 controls the opening degree of the proportional valve 49 to open, and the pressure detected by the pressure sensor 17b. Is supplied from the flow path 13 to the flow path 14. At the same time, the controller 47 controls the regulator 11 a of the third hydraulic pump 11 to tilt the swash plate of the third hydraulic pump 11. At time t2, the controller 47 controls the regulator 11a of the third hydraulic pump 11 so that the discharge flow rate of the hydraulic oil discharged from the third hydraulic pump 11 is the same as the flow rate of the hydraulic oil passing through the proportional valve 49. Simultaneously with the control, the opening degree of the switching valve 39 is controlled to open the hydraulic oil.

When the pressure in the flow path 14 decreases to _Pr3 at time t3, the controller 47 sets the flow rate of the proportional valve 49 to the maximum Q _cp1 and the discharge flow rate of the third hydraulic pump 11 to Q _cp1 . At time t1 to t2, the pressure of the passage 14 when lower than set discharge pressure _{P r2} of the charge pump 12, flows into the hydraulic fluid charge pump 12 is discharged through the check valve 21b into the channel 14. When the pressure in the flow path 14 decreases to _Pr3 at time t3, the flow rate of the check valve 21b becomes _Qc3 . At time t <b> 3 to t <b> 4, the controller 47 opens the proportional valve 49 to allow the hydraulic oil to pass, and the pressure of the flow path 14 increases due to the flow of the hydraulic oil from the flow path 13 to the flow path 14.

At time t4, when the operating pressure of the flow path 14 reaches _Pr4 based on the detection value of the pressure sensor 17b, the controller 47 closes and shuts off the proportional valve 49 and sets the flow rate of the flow path 14 to zero. . At time t4 to t5, the pressure in the flow path 14 reaches the _{P r1,} the flow rate of the check valve 21b becomes zero. When the flow rate of the third hydraulic pump 11 becomes 0 at the time t5 at the time t5, the controller 47 closes the switching valve 39 to shut off the supply of hydraulic oil from the second branch flow path 39a. At time t5 to t6, the pressure in the head chamber 1a of the boom cylinder 1 reaches _{P bh2,} increased operating speed of the boom cylinder 1, an increase in the outflow flow rate _{Q Br} from the rod chamber 1b of the boom cylinder 1, a flow The pressure in the path 14 rises to _Pr2 . At time t6, the actual operating speed of the boom cylinder 1 reaches the target speed _Vb1 .

As described above, according to the second embodiment of the present invention, the hydraulic fluid flow rate supplied from the flow path 13 to the flow path 14 via the proportional valve 49 at time t2 to t5 is changed to the third hydraulic pump 11. Since the time required for raising the pressure of the head chamber 1a of the boom cylinder 1 to _Pbh2 can be shortened compared to the first embodiment, the operation of the boom cylinder 1 with respect to the operation amount of the operation lever 48a is reduced. Speed responsiveness can be further improved.

[Third embodiment]
The third embodiment differs from the first embodiment described above in that the first embodiment controls the flow rates of the first and second hydraulic pumps 9 and 10 based on the pressure receiving area ratio of the boom cylinder 1. In contrast, in the third embodiment, the flow rates of the first and second hydraulic pumps 9 and 10 are controlled substantially based on the pressure receiving area ratio of the boom cylinder 1. In the third embodiment, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals.

Specifically, when the discharge flow rate Q _cp of the hydraulic oil discharged from the first hydraulic pump 9 is larger than Q _cp1 , the pressure receiving area A _a1 of the head chamber 1a of the boom cylinder 1 and the pressure receiving area A _a2 of the rod chamber 1b are set. to _{a a2, (Q cp + Q} op1):: area ratio _a a1 of the _{Q cp,} decreases the ratio of _(Q cp ₊ Q _op1). (Q _cp + Q _op1 ) is the flow rate of hydraulic fluid flowing into the head chamber 1a of the boom cylinder 1, and the flow rate of hydraulic fluid flowing out from the rod chamber 1b decreases as this ratio decreases. Therefore, in order to secure the suction flow rate Q _cp of the hydraulic oil sucked by the first hydraulic pump 9, it is necessary to replenish a predetermined amount of hydraulic oil from the check valve 21b.

For this reason, the flow rate of the check valve 21b increases as shown by the dotted line in FIG. 3 (i) with respect to the ideal flow rate shown by the solid line in FIG. 3 (i). Further, even after time t7 when the pressure in the flow path 14 is stabilized, the flow rate of the hydraulic oil flowing out from the rod chamber 1b of the boom cylinder 1 is smaller than the suction flow rate _Qcp of the first hydraulic pump 9, so that a constant flow rate is obtained. Is supplied to the flow path 14 from the check valve 21b.

On the other hand, when the discharge flow rate Qop of the hydraulic oil discharged by the second hydraulic pump 10 is larger than Qop1, the area ratio Aa1: Aa2 of the pressure receiving area Aa1 of the head chamber 1a of the boom cylinder 1 and the pressure receiving area Aa2 of the rod chamber 1b is set. against, (Qcp1 + Qop): of Qcp1, the size ratio of (Qcp1 + Qop) Kunar. (Qcp1 + Qop) is a flow rate of hydraulic fluid flowing into the head chamber 1a of the boom cylinder 1, and when this ratio increases, the flow rate of hydraulic fluid flowing out from the rod chamber 1b increases. Therefore, the excess hydraulic oil is discharged from the flushing valve 20 to the hydraulic oil tank 18 through the relief valve 20a with respect to the suction flow rate Qcp1 of the hydraulic oil sucked by the first hydraulic pump 9. As a result, the flow rate of the check valve 21b is smaller than the ideal flow rate indicated by the solid line in FIG. 3 (i), as indicated by the one-dot chain line in FIG. 3 (i).

That is, either when the discharge flow rate Q _cp of the hydraulic oil discharged from the first hydraulic pump 9 is higher than Q _cp1 or when the discharge flow rate Q _op of the hydraulic oil discharged from the second hydraulic pump 10 is higher than Q _op1. However, since the flow rate of hydraulic oil supplied from the charge pump 12 to the suction side of the first hydraulic pump 9 via the flow path 14 can be reduced, the charge pump 12 can be reduced in size, and the charge pump 12 having a smaller discharge capacity can be obtained. As a result, the charge pump 12 can be eliminated.

[Fourth Embodiment]
FIG. 6 is a schematic diagram showing a configuration of a hydraulic drive apparatus 107A according to the fourth embodiment of the present invention. The fourth embodiment differs from the first embodiment described above in that the first embodiment is hydraulically driven using the proportional valve 49, whereas the fourth embodiment is hydraulically driven using the switching valve 51. The apparatus 107A is used. In the fourth embodiment, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals.

Specifically, the hydraulic drive device 107 </ b> A according to the fourth embodiment has a switching valve 51 connected on a bypass channel 49 a that connects the channels 13 and 14. The switching valve 51 functions as a flow rate adjusting unit 60 that drives the pressure in the flow path 14 on the suction side of the first hydraulic pump 9 as the pilot pressure (communication pressure) during the boom cylinder 1 extension operation. Specifically, the switching valve 51 adjusts the pilot pressure so as to communicate when the pressure in the flow path 14 becomes equal to or lower than _Pr4 . A throttle is provided on the communication side of the switching valve 51. The restrictor is designed to have an opening area that passes through the maximum discharge flow rate of the first hydraulic pump 9 at an arbitrary predetermined pressure P _VC . The pressure P _VC is determined based on the difference between the pressure P _{bh in} the head chamber 1a and the pilot pressure P _r4 of the switching valve 51 when the boom cylinder 1 starts to extend.

  As a result, the discharge flow rate of the first hydraulic pump 9 can be returned to the suction-side flow path 14 via the switching valve 51 until the boom cylinder 1 is extended, and the second hydraulic pressure is increased. The discharge flow rate discharged by the pump 10 can be sent to the head chamber 1 a of the boom cylinder 1. Therefore, since the switching valve 51 is configured to open and close based on the pressure in the flow path 14, electrical control by the controller 47 is eliminated compared to the proportional valve 49 of the hydraulic drive device 107 according to the first embodiment. Therefore, the control by the controller 47 can be further simplified.

[Fifth Embodiment]
FIG. 7 is a schematic diagram showing a configuration of a hydraulic drive device 107B according to the fifth exemplary embodiment of the present invention. The fifth embodiment differs from the first embodiment described above in that the first embodiment is a hydraulic drive device 107 using the charge pump 12 and the fifth embodiment is a hydraulic drive device not using the charge pump 12. 107B. In the fourth embodiment, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals.

  Specifically, in the hydraulic drive device 107B according to the fourth embodiment, an accumulator 50 as a pressure accumulator is connected on the flow path from the flushing valve 20 to the charge check valves 21a and 21b. The accumulator 50 is connected on the flow path between the relief valves 19a and 19b and the charge check valves 21a and 21b, and the relief valve 20a on the flow path between the charge check valves 21a and 21b and the hydraulic oil tank 18. Is connected.

As a result, it is possible to prevent the low pressure side flow paths 13 and 14 from becoming the set pressure set by the relief valve 20a among the flow paths 13 and 14, and immediately after the operation of the boom cylinder 1 starts, the first liquid When the pressure of the flow path 14 on the suction side of the pressure pump 9 decreases, the controller 47 opens the proportional valve 49 based on the detection value of the pressure sensor 17b, and the hydraulic oil flows from the flow path 13 into the flow path 14. Thus, the suction flow rate Q _cp sucked into the first hydraulic pump 9 can be secured from the flow path 13. Therefore, when the flow path 14 becomes a low pressure, the hydraulic oil stored in the accumulator 50 can be supplied to the suction side of the first hydraulic pump 9, and therefore the charge pump 12 can be eliminated.

[Others]
In addition, this invention is not limited to embodiment mentioned above, Various deformation | transformation aspects are included. For example, the above-described embodiments have been described in order to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to those having all the configurations described.

  In each of the above-described embodiments, the case where the hydraulic drive devices 107 to 107B are mounted on the hydraulic excavator 1 has been described as an example. The hydraulic drive devices 107 to 107B according to the present invention can be used in a work machine other than the hydraulic excavator 100 as long as the work machine includes at least one or more single rod hydraulic cylinders that can be driven by the hydraulic excavator 100. Further, the extension start control according to the present invention may be applied to the arm cylinder 3 and the bucket cylinder 5 other than the boom cylinder 1.

  Further, as the second and third hydraulic pumps 10 and 11, hydraulic pumps having a bi-tilt swash plate mechanism capable of controlling the discharge direction and the discharge flow rate are used. You may use the hydraulic pump provided with the unilateral swash plate mechanism which can discharge hydraulic oil only to one direction which goes to.

  In addition, each of the first to third hydraulic pumps 9 to 11 is connected to one engine 7 via the power transmission device 8, but a plurality of these first to third hydraulic pumps 9 to 11 are used. Fixed-capacity hydraulic pumps are prepared, and electric motors capable of controlling the rotation direction and the number of rotations are connected to these fixed-capacity hydraulic pumps. The hydraulic oil discharge direction and the discharge flow rate may be controlled by the rotation direction and the rotation speed of the hydraulic pump.

  Furthermore, in each said embodiment, although the switching valves 25-27, 37-39 and the proportional switching valves 30 and 42 were shown by the direct control by the signal which the controller 47 output, it does not concern to this, For example, a controller The signal from 47 may be controlled by a hydraulic signal converted using an electromagnetic pressure reducing valve or the like, or may be controlled by a hydraulic circuit.

  Further, although the conduction start timing of passing through the hydraulic oil of the proportional valve 49 is controlled based on the pressure value detected by the pressure sensor 17b, the first and second hydraulic pumps 9 and 10 are driven using, for example, a timer. The proportional valve 49 may be driven after an arbitrary time has elapsed since the start of the operation.

1 Boom cylinder (single rod hydraulic cylinder)
1a Head chamber 1b Rod chamber 1e Piston 3 Arm cylinder (hydraulic actuator)
5 Bucket cylinder (hydraulic actuator)
9 1st hydraulic pump (1st hydraulic oil control part)
10 Second hydraulic pump (second hydraulic oil control unit)
11 Third hydraulic pump (second hydraulic oil control unit)
13 to 16 Flow path 15a Branch path 17a, 17b Pressure sensor (pressure detection device)
18 Hydraulic oil tank 27a First branch flow path 39a Second branch flow path 47 Controller (control device)
48a to 48d Operation lever 49 Proportional valve (valve device)
49a Bypass passage 51 Switching valve 60 Flow rate adjusting unit 100 Hydraulic excavator 107, 107A, 107B Hydraulic drive device A Closed circuit B, C Open circuit

Claims (1)

A first hydraulic oil control unit capable of flowing hydraulic oil in both directions; a piston; a head chamber into which hydraulic oil is introduced when the piston is extended; and a rod chamber into which the hydraulic oil is introduced when the piston is retracted. a first hydraulic cylinder having, before Symbol a first hydraulic fluid control unit and the head chamber and the rod chamber and the closed circuit that is connected to the annular the flow path through which the hydraulic fluid, a first hydraulic fluid control unit a branch passage which is branched from the flow path which connects the head chamber, the branch passage and the branch passage other end of which is connected to one end side connected hydraulic oil tank is provided in the branch flow path, a second hydraulic fluid control unit for controlling the flow rate of the hydraulic fluid between the hydraulic fluid tank and the branch passage, and a second hydraulic cylinder driven by the supply of hydraulic fluid from the second hydraulic fluid control unit , A bypass valve for bypassing the flow of the first hydraulic oil control unit. And path channel, provided in the bypass passage, a flow for connecting the proportional valve for controlling the flow rate of the hydraulic fluid flowing through the bypass passage, and said rod chamber and the head chamber and the first hydraulic oil control section A pressure detection device provided in each of the passages, and a control device that controls the proportional valve based on the pressure detected by each pressure detection device,
The head chamber and the rod chamber have a predetermined pressure receiving area difference,
When the input signal for extending the first hydraulic cylinder is input, the control device is configured so that the speed of the extension operation of the first hydraulic cylinder becomes a predetermined target extension speed. And controlling the sum of the flow rate of the hydraulic oil supplied from the first hydraulic oil control unit and the flow rate of the hydraulic oil supplied from the second hydraulic oil control unit as the hydraulic flow rate to the head chamber, and the first The first hydraulic oil control unit and the second hydraulic oil so that the flow rate ratio supplied from the hydraulic oil control unit and the second hydraulic oil control unit is a flow rate ratio based on a pressure receiving area difference of the first hydraulic cylinder. Controlling the control unit, and controlling the proportional valve when the lower pressure value detected by the pressure detection device is equal to or lower than a predetermined pressure value, thereby connecting the bypass flow path to the high pressure side of the first hydraulic oil control unit this is the flow rate adjusting hydraulic oil flowing into the low-pressure side from Hydraulic drive system according to claim.