JP2015183768A - Method of driving actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of driving an actuator, which can assist the expansion/contraction driving of a cylinder rod so as to obtain target speed according to lever operation amount.SOLUTION: A method of driving a hydraulic actuator 40 having a cylinder rod 42 driven to expand/contract, includes: a step for detecting lever operation amount which drives the cylinder rod to expand/contract, and the actual speed of the cylinder rod 42 when the cylinder rod 42 is driven to expand/contract according to the lever operation amount; and an assist step for enhancing driving force for driving the cylinder rod 42 to expand/contract, and bringing the actual speed of the cylinder rod 42 closed to target speed, when the detected actual speed is lower than the target speed set in advance according to the lever operation amount.

Description

  The present invention relates to a method for driving an actuator such as a hydraulic cylinder used in a work machine such as a hydraulic excavator.

  Conventionally, when this type of actuator is used in a working machine such as a hydraulic excavator, the rod is expanded and contracted by the pressure oil supplied to the cylinder. A configuration is known in which the expansion and contraction of the rod is controlled only by the pressure oil supplied from the hydraulic pump driven by the hydraulic pump.

  Further, for example, Patent Document 1 discloses a conventional technique in which this type of actuator is provided with redundancy. In the actuator disclosed in Patent Document 1, in addition to the hydraulic pressure supplied from the hydraulic pump, a screw shaft is attached to the end of the rod so as to be extendable and retractable, and the rod can be expanded and contracted by rotating the screw shaft with an electric motor. It is set as the structure.

JP2007-1555075A

  The prior art disclosed in Patent Document 1 described above is merely an actuator using both hydraulic drive by pressure oil supplied from a hydraulic pump and electric drive by an electric motor, and the hydraulic pump is not driven due to some factor. In some cases, the actuator can be driven using an electric motor, and the hydraulic drive of the actuator by the hydraulic pump is assisted by the electric drive by the electric motor, for example, depending on the operation amount when operating the operation lever, etc. Thus, no consideration is given to the configuration for assisting the rod expansion / contraction drive when the actual expansion / contraction speed of the rod is lower than the preset target speed.

  The present invention has been made from the above-described prior art, and an object of the present invention is to provide an actuator driving method capable of assisting rod expansion and contraction driving so as to achieve a target speed corresponding to an operation amount.

  In order to achieve this object, the present invention is a method of driving an actuator having a rod that can be extended and contracted, and an operation amount for extending and retracting the rod, and the rod is extended and driven according to the operation amount. A detection step of detecting the actual speed of the rod at the time, and when the detected actual speed is lower than a target speed set in advance according to the operation amount, the driving force for extending and retracting the rod is increased, An assist step for bringing the actual speed of the rod closer to the target speed.

  The present invention configured as described above detects an operation amount for extending and retracting the rod of the actuator and an actual speed of the rod when the rod is expanded and contracted according to the operation amount. When the detected actual speed is lower than the target speed set in advance according to the operation amount, the driving force for extending and retracting the rod is increased to bring the actual speed of the rod closer to the target speed. For this reason, the expansion / contraction driving of the rod can be assisted so as to reach the target speed corresponding to the operation amount when the rod is expanded and contracted, and the actual speed of the rod can be brought close to the target speed.

  Further, the present invention is the above invention, wherein the rod is configured such that pressure oil corresponding to the operation amount is supplied from a hydraulic pump to be expanded and contracted, and can be expanded and contracted by an electric motor, and the assist step includes: When the detected actual speed of the rod is lower than the target speed, the driving force for driving the electric motor to drive the rod to extend and contract is increased.

  In the present invention configured as described above, the actual speed when the pressure oil according to the operation amount is supplied from the hydraulic pump to the actuator and the rod is driven to extend and contract is lower than the target speed set in advance according to the operation amount. In this case, the driving force for driving the electric motor to drive the rod to extend and contract is increased. For this reason, the rod's expansion / contraction drive can be assisted by an electric motor of a drive source different from this hydraulic pump so that the target speed according to the operation amount when the rod is driven to extend / contract by the hydraulic pump can be assisted. The speed of can be brought closer to the target speed more appropriately.

  Further, in the present invention according to the above-mentioned invention, the rod may be configured to be expanded and contracted when pressure oil corresponding to the operation amount is supplied from a hydraulic pump and is supplied from another hydraulic pump different from the hydraulic pump. The assist step is configured to drive the other hydraulic pump to drive the rod to extend and contract when the detected actual speed of the rod is lower than the target speed. It is characterized by enhancing.

  In the present invention configured as described above, the actual speed when the pressure oil corresponding to the operation amount is supplied from the hydraulic pump to the actuator and the rod is driven to extend and contract is greater than the target speed preset according to the operation amount. When it is low, the driving force for driving the rod to extend and contract is increased by driving another hydraulic pump different from the hydraulic pump that supplies pressure oil according to the operation amount. For this reason, the rod can be extended and retracted with another hydraulic pump, which is a drive source different from this hydraulic pump, so that the target speed according to the operation amount when the rod is driven to extend and contract with the hydraulic pump can be assisted. The actual speed of the rod can be brought closer to the target speed more appropriately.

  Further, the present invention is the above invention, wherein the assist step detects a discharge flow rate of the pressure oil discharged from the hydraulic pump, and when the detected discharge flow rate reaches a maximum discharge flow rate of the hydraulic pump, A driving force for extending and retracting the rod is increased.

  The present invention configured as described above detects the discharge flow rate of the pressure oil discharged from the hydraulic pump, and when the detected discharge flow rate reaches the maximum discharge flow rate of the hydraulic pump, the electric motor is driven to drive the rod. Increase the driving force to drive the telescope. Therefore, when the discharge flow rate of the hydraulic oil of the hydraulic pump that increases the necessity of assisting the rod expansion / contraction drive reaches the maximum discharge flow rate, the electric motor is driven to assist the rod expansion / contraction drive. Telescopic drive assist can be performed with a simpler configuration.

  According to the present invention, in the above invention, the assist step detects a discharge pressure of the pressure oil discharged from the hydraulic pump, and based on the detected discharge pressure, increases the driving force for driving the rod to extend and contract. It is characterized by increasing.

  The present invention configured as described above detects the discharge pressure of the pressure oil discharged from the hydraulic pump, and based on the detected discharge pressure, increases the rate of increasing the driving force for driving the rod to extend and contract. Increase the driving force to drive the telescope. Therefore, as the discharge pressure of the pressure oil discharged from the hydraulic pump increases, the ratio of increasing the driving force for extending and retracting the rod can be increased in correspondence with the increase in the assist amount of the rod expansion and contraction drive. The expansion / contraction drive assist can be performed more appropriately.

  Further, the present invention is the above invention, wherein the assist step detects a discharge pressure of the pressure oil discharged from the hydraulic pump, refers to an adjustment table based on the detected discharge pressure, and controls the other hydraulic pump. The driving force for driving the rod to extend and contract is enhanced.

  The present invention configured as described above detects the discharge pressure of the pressure oil discharged from the hydraulic pump, refers to the adjustment table based on the detected discharge pressure, and drives the other hydraulic pump to drive the rod to extend and contract. Increase the driving force. Therefore, since the assist amount by the other hydraulic pump can be adjusted in accordance with the discharge pressure of the hydraulic pump, the rod expansion / contraction drive assist can be more appropriately performed with a simple configuration.

  The present invention detects an operation amount for extending and retracting the actuator rod, and an actual speed of the rod when the rod is driven to extend and contract according to the operation amount. When the target speed is lower than the preset target speed according to the amount, the driving force for driving the rod to extend and contract is increased, and the actual speed of the rod is brought close to the target speed. Therefore, it is possible to assist the rod expansion / contraction drive so as to achieve the target speed corresponding to the operation amount when the rod is expanded / contracted, and the actual speed of the rod can be brought close to the target speed. Problems, configurations, and effects other than those described above will be made clear from the following description of embodiments.

1 is a schematic side view showing a hydraulic excavator in which an actuator according to a first embodiment of the present invention is used. It is a figure which shows the hydraulic circuit for driving the said actuator. It is the schematic which shows the said actuator. It is a graph which shows the pump maximum discharge amount line of the hydraulic pump which drives the said actuator. FIG. 3 is an explanatory diagram showing a driving method of the actuator, wherein (a) is a pump maximum discharge flow diagram, (b) is a graph showing lever operation amounts in time series, and (c) is a target cylinder speed / pump converted to flow rate. It is a graph which shows discharge flow volume and assist amount in time series. It is a flowchart which shows the drive method of the said actuator. It is the schematic which shows the actuator which concerns on 2nd Embodiment of this invention. It is the schematic which shows the actuator which concerns on 3rd Embodiment of this invention. It is the schematic which shows the actuator which concerns on 4th Embodiment of this invention. FIG. 3 is an explanatory diagram showing a driving method of the actuator, wherein (a) is a pump maximum discharge flow diagram, (b) is a graph showing lever operation amounts in time series, and (c) is a target cylinder speed / pump converted to flow rate. It is a graph which shows discharge flow volume and assist amount in time series. It is a graph which shows the assist adjustment gain table of the said actuator. It is a flowchart which shows the drive method of the said actuator. It is the schematic which shows the actuator which concerns on the 1st reference form relevant to this invention. It is a figure which shows the hydraulic circuit for driving the said actuator. It is a figure which shows the hydraulic circuit for driving the actuator which concerns on the 2nd reference form relevant to this invention.

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

[First Embodiment]
FIG. 1 is a schematic side view showing a hydraulic excavator provided with an actuator according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating a hydraulic circuit for driving the actuator. FIG. 3 is a schematic view showing the actuator. FIG. 4 is a graph showing a pump maximum discharge amount line of the hydraulic pump that drives the actuator. 5A and 5B are explanatory diagrams showing the driving method of the actuator, where FIG. 5A is a pump maximum discharge flow diagram, FIG. 5B is a graph showing lever operation amounts in time series, and FIG. 5C is a target cylinder speed converted to flow rate. It is a graph which shows time-sequentially the pump discharge flow rate and the assist amount. FIG. 6 is a flowchart showing a driving method of the actuator.

<Overall configuration>
As shown in FIG. 1, a hydraulic excavator 1 as a work machine according to a first embodiment of the present invention includes a lower traveling body having a pair of left and right traveling devices 2c and 2d driven by a pair of traveling motors 2a and 2b. 2 and an upper swing body 3 that is rotatably mounted on the lower traveling body 2 via a swing motor 3a. On the front side of the upper swing body 3, there is provided a cab 3 b in which an operation lever 4 is attached. An engine room 3 c is provided in the middle part of the upper swing body 3. A counterweight 3d is attached to the rear side of the engine chamber 3c, and a front work machine 5 capable of excavation work or the like is attached to the front side of the upper swing body 3 so as to be rotatable in the vertical direction. The front work machine 5 includes a boom 5a, one end of which is pivotally connected to the upper swing body 3 so as to be able to suppress wrinkles, and an arm 5b, which is pivotally connected to the tip of the boom 5a. The bucket 5d is rotatably connected to the tip of the arm 5b through a four-bar linkage mechanism 5c.

  The front work machine 5 includes a pair of boom cylinders 6 for supporting and driving the boom 5a up and down, an arm cylinder 7 for supporting and operating the arm 5b up and down, and a bucket 5d up and down. And a bucket cylinder 8 for movably supporting and operating. The boom cylinder 6 has an end on the cylinder tube 6a side on the base end side fixed to the front upper surface of the upper swing body 3 so as to be rotatable, and an end on the cylinder rod 6b side on the distal end side of the base end of the boom 5a. It is rotatably fixed to the side. The end of the cylinder tube 7a on the base end side of the arm cylinder 7 is fixed to the upper surface of the middle part of the boom 5a so that the arm cylinder 7 can rotate, and the end of the cylinder rod 7b on the front end side is the base end of the arm 5b. It is fixed to the part so that rotation is possible. Further, the bucket cylinder 8 has an end on the cylinder tube 8a side on the base end side fixed to the upper surface of the arm 5b so as to be rotatable, and an end on the cylinder rod 8b side on the distal end side rotated on the four-bar linkage mechanism 5c. It is attached as possible.

<Hydraulic drive>
Next, the excavator 1 is driven by a hydraulic drive device 11 shown in FIG. The hydraulic drive device 11 includes an engine 12 as a prime mover, first and second hydraulic pumps 13a and 13b that are fluid pressure pumps driven by the engine 12, a hydraulic oil tank 14, And a control valve device 16 connected to the discharge oil passages 15a and 15b of the first and second hydraulic pumps 13a and 13b. The engine 12, the first and second hydraulic pumps 13a, 13b, and the like are stored in the engine chamber 3c. The control valve device 16 is attached with left and right traveling motors 2a and 2b, a swing motor 3a, a pair of boom cylinders 6, an arm cylinder 7 and a bucket cylinder 8 which are hydraulic actuators.

  The control valve device 16 includes a first valve section 20 including center bypass type directional control valves 21, 22, 23, and 24, and a second valve section 30 including center bypass type directional control valves 31, 32, and 33. Have. Each directional control valve 21, 22, 23, 24 of the first valve section 20 has a three-position switching configuration, and the order shown in the figure on the center bypass line 17a connected to the discharge oil passage 15a of the first hydraulic pump 13a. Are connected in parallel. Further, the directional control valves 31, 32, 33 of the second valve section 30 have a three-position switching configuration, and the order shown in the drawing is on the center bypass line 17b connected to the discharge oil passage 15b of the second hydraulic pump 13b. Are connected in parallel.

  Here, in the second valve section 30, the main relief valve 18 for regulating the maximum discharge pressure of the first and second hydraulic pumps 13a, 13b is connected to the most upstream part of the center bypass lines 17a, 17b. The main relief valve 18 is pumped by the first and second hydraulic pumps 13a and 13b when one of the first and second hydraulic pumps 13a and 13b becomes equal to or higher than a predetermined pressure (maximum discharge pressure). The hydraulic oil (pressure oil) as the working fluid is to be released to the hydraulic oil tank 14.

  The direction control valve 21 of the first valve section 20 is a bucket direction control valve, and the actuator port side is connected to the bucket cylinder 8 through an oil passage, and controls the flow of hydraulic oil to the bucket cylinder 8. The direction control valve 22 is a first arm direction control valve, and the actuator port side is connected to the arm cylinder 7 through an oil passage, and controls the flow of hydraulic oil to the arm cylinder 7. Furthermore, the direction control valve 23 is a boom direction control valve, and the actuator port side is connected to each boom cylinder 6 through an oil passage, and controls the flow of hydraulic oil to the boom cylinder 6. The direction control valve 24 is a first travel direction control valve, and the actuator port side is connected to the travel motor 2a through an oil passage, and controls the flow of hydraulic oil to the travel motor 2a.

  On the other hand, the direction control valve 31 of the second valve section 30 is a turning direction control valve, and the actuator port side is connected to the turning motor 3a through an oil passage, and controls the flow of hydraulic oil to the turning motor 3a. The directional control valve 32 is a second arm directional control valve, and the actuator port side is connected to the arm cylinder 7 through an oil passage together with the first arm directional control valve 22. Control the flow. Further, the direction control valve 33 is a second traveling direction control valve, and the actuator port side is connected to the traveling motor 2b through an oil passage, and controls the flow of hydraulic oil to the traveling motor 2b.

  Here, the bucket direction control valve 21 and the boom direction control valve 23 are provided with a first operation lever 4a for controlling the switching position of the direction control valves 21 and 23 with the pilot signal pressure. That is, by operating the first operation lever 4a, the oil passages of the hydraulic oil supplied from the first and second hydraulic pumps 13a and 13b are switched, and the expansion / contraction driving of the bucket cylinder 8 and the boom cylinder 6 is controlled. Further, the first arm direction control valve 22, the turning direction control valve 31, and the second arm direction control valve 32 have a second control signal for controlling the switching position of the direction control valves 22, 31, 32 by the pilot signal pressure. An operation lever 4b is attached. That is, by the operation 4b of the second operation lever, the oil passages of the hydraulic oil supplied from the first and second hydraulic pumps 13a and 13b are switched, and the turning drive of the turning motor 3a and the expansion / contraction driving of the arm cylinder 7 are controlled. Is done.

  The first travel direction control valve 24 is provided with a third operation lever 4c for controlling the switching position of the direction control valve 24 with the pilot signal pressure. By operating the third operating lever 4c, the oil passage of the first traveling direction control valve 24 is switched, and the driving of the traveling motor 2a is controlled. Further, the second travel direction control valve 25 is provided with a fourth operation lever 4d for controlling the switching position of the direction control valve 25 with the pilot signal pressure. That is, the oil path of the second travel direction control valve 25 is switched by the operation of the fourth operation lever 4d, and the drive of the travel motor 2b is controlled. Here, the first to fourth operation levers 4a, 4b, 4c, 4d constitute the operation lever 4.

<Electric-hydraulic combined cylinder>
Next, the configuration of a hydraulic actuator such as the arm cylinder 7 attached to the hydraulic excavator 1 will be described.

  As shown in FIG. 3, the hydraulic actuator 40 is a combined electro-hydraulic cylinder, and a cylinder rod 42, which is an elongated cylindrical rod, is coaxial from the one end side of a cylinder tube 41, which is a hollow, substantially cylindrical cylinder. One end side of the cylinder rod 42 is included so as to be movable in the axial direction. A disc-shaped head 42a is attached to one end of the cylinder rod 42, and the head 42a bisects the space in the cylinder tube 41 along the axial direction. Here, a space surrounding the end surface of the head 42a in the cylinder tube 41 is a bottom chamber 41a, and a space surrounding the end surface on the opposite side of the head 42a and the cylinder tube 41 is a rod chamber 41b.

  The bottom chamber 41a and the rod chamber 41b are provided with ports 41c and 41d for supplying and discharging hydraulic oil in the bottom chamber 41a and the rod chamber 42b, respectively. The ports 41c and 41d are provided with the peripheral surface of the cylinder tube 41 opened, and the cylinder rod 42 is connected to the cylinder tube by supplying and discharging hydraulic oil from the ports 41c and 41d to the bottom chamber 41a and the rod chamber 41b. 41 is expanded and contracted. Furthermore, the distal end side of the cylinder rod 42 and the other end side of the cylinder tube 41 are respectively connected to the distal end side of the cylinder rod 42 and the proximal end side which is the other end side of the cylinder tube 41. Pin insertion portions 42b and 41e are provided at respective predetermined positions so as to be pivotably fastened via pins.

  Furthermore, an assist device 50 for assisting the expansion / contraction drive of the cylinder rod 42 of the hydraulic actuator 40 is attached to the hydraulic actuator 40. The assist device 50 includes an electric motor 51, and the electric motor 51 is attached to a side portion of the hydraulic actuator 40 near one end of the cylinder tube 41. The electric motor 51 assists the expansion / contraction drive of the hydraulic actuator 40 with the electric power when the electric motor 51 is driven. That is, the electric motor 51 uses a driving force when the electric motor 51 is driven to the cylinder rod 42 as a driving force different from the driving force to the cylinder rod 42 due to the supply and discharge of hydraulic oil from the hydraulic pump 13. The electric power assist is performed so that the speed of the expansion / contraction driving of the cylinder rod 42 becomes a target speed.

  Specifically, the electric motor 51 is attached with a proximal end side of a feed screw portion 52 which is a substantially cylindrical shaft having a helical thread groove 52a formed in the circumferential direction on the outer peripheral surface. The feed screw portion 52 can be rotationally driven in the circumferential direction by driving 51. The feed screw portion 52 is attached so that the axial direction of the feed screw portion 52 is aligned with the axial direction of the cylinder rod 42, and the feed screw portion 52 and the cylinder rod 42 are arranged in parallel. Has been. Further, the feed screw portion 52 is formed in a length dimension larger than the maximum protrusion amount of the cylinder rod 42 from one end side of the cylinder tube 41.

  On the other hand, a substantially cylindrical solenoid portion 53 having an axial direction along the radial direction of the cylinder rod 42 is provided at a position closer to the distal end on the proximal end side than the pin insertion portion 42 b of the cylinder rod 42. A projecting portion 54 as an elongated cylindrical engaging portion that protrudes in the radial direction of the cylinder rod 42 is attached to the solenoid portion 53 so as to be extendable and contractible. The amount of movement of the projection 54 in the axial direction is controlled by the electromagnetic force formed by the solenoid unit 53. Further, the projecting portion 54 is configured to project along the radial direction of the feed screw portion 52, and from the position where the tip portion of the projecting portion 54 is fitted into the thread groove 52 a of the feed screw portion 52, It moves away from the screw groove 52a to a position where the fitting into the screw groove 52a is completely released. Here, regarding the axial length of the feed screw portion 52 and the positional relationship between the projection portion 54 and the feed screw portion 52, the projection portion 54 is in each of the most contracted state and the most extended position. The screw thread 52 a of the feed screw portion 52 can be reliably fitted.

  Further, a power source 55 for supplying electric power to the electric motor 51 is attached to the electric motor 51. Between the power supply 55 and the electric motor 51, there is a voltage regulator 56 that controls the supply voltage to the electric motor 51, and a switch 57 that opens and closes the connection between the voltage regulator 56 and the power supply 55. It is attached. The voltage regulator 56 and the switch 57 are connected to a controller 58 as a control unit via signal lines 56a and 57a, respectively. The controller 58 controls the on / off of the switch 57 and the voltage regulator. The voltage adjustment by 56 is controlled. The controller 58 is connected to the solenoid unit 53 via a signal line 53a, and the controller 58 controls the extension / contraction drive of the projection 54 by the solenoid unit 53.

  The electric motor 51 is connected to the controller 58 via a signal line 51a. Furthermore, a lever operation amount detector 61 is connected to the controller 58 via a signal line 61a as a sensor for detecting the operation amount of the operation lever 4 for operating the hydraulic actuator 40. The controller 58 includes a pump discharge pressure detector 62 as a sensor for detecting the discharge pressure of the hydraulic oil discharged from the hydraulic pump 13 and a sensor for detecting the discharge flow rate of the hydraulic oil discharged from the hydraulic pump 13. Are connected to the pump discharge flow rate detector 63 via signal lines 62a and 63a, respectively. The pump discharge pressure detection unit 62 and the pump discharge flow rate detection unit 63 are attached to the discharge oil passage 15 of the hydraulic pump 13. Further, an engine speed detector 64 is connected to the controller 58 via a signal line 64a as a sensor for detecting the speed of the engine 12.

  The controller 58 has a cylinder speed detector 65 as a sensor for detecting the actual cylinder speed c, which is the actual speed of the cylinder rod 42 when the cylinder rod 42 of the hydraulic actuator 40 is driven to extend and contract. They are connected via a signal line 65a. The cylinder speed detection unit 65 is attached, for example, at a position near the pin insertion portion 42b of the cylinder rod 42 of the hydraulic actuator 40, and the actual cylinder speed with respect to the cylinder tube 41 when the cylinder rod 42 is driven to extend and contract. c is detected.

<Operating principle>
Next, the operation principle when the hydraulic actuator 40 is hydraulically driven by the hydraulic pump 13 will be described.

(Extension operation)
First, when the hydraulic actuator 40 is extended only by hydraulic pressure, the operation lever 4 is operated while the engine 12 is driven, the oil path between the hydraulic pump 13 and the bottom chamber 41a of the hydraulic actuator 40, and the rod chamber. Each of the oil passages between 41b and the hydraulic oil tank 14 are communicated with each other by a direction control valve (not shown), and the hydraulic oil discharged from the hydraulic pump 13 is supplied to the bottom chamber 41a, and the inside of the rod chamber 41b. The hydraulic oil is discharged to the hydraulic oil tank 14.

  Here, the area (pressure receiving area) of the head 41a on the side of the bottom chamber 41a that receives hydraulic pressure of the hydraulic oil is “A”, and the area of the head 41a on the side of receiving pressure of the hydraulic oil on the side of the rod chamber 41b (pressure receiving area). ) Is “B”. When the hydraulic pressure on the bottom chamber 41a side is “pa”, the hydraulic pressure on the rod chamber 41b side is “pb”, and the load force acting in the contraction direction of the cylinder rod 42 is “F1”, the cylinder rod 42 is The extending force is “A × pa”, and the force for contracting the cylinder rod 42 is “B × pb + F1”.

  For this reason, the drive of the hydraulic pump 13 is controlled so that the force “A × pa” for extending the cylinder rod 42 exceeds the force “B × pb + F1” for contracting the cylinder rod 42. The cylinder rod 42 extends by increasing the hydraulic pressure “pa” on the bottom chamber 41a side by the discharged hydraulic oil.

(Reduction operation)
On the other hand, when the hydraulic actuator 40 is contracted only by the hydraulic pressure, the operation lever 4 is operated, the oil passage between the hydraulic pump 13 and the rod chamber 41b of the hydraulic actuator 40, the bottom chamber 41a, the hydraulic oil tank 14, Are connected to each other by a directional control valve (not shown), the hydraulic oil discharged from the hydraulic pump 13 is supplied to the rod chamber 41b, and the hydraulic oil in the bottom chamber 41a is supplied to the hydraulic oil tank. 14 to be discharged.

  In this case, when the load force acting in the extending direction of the cylinder rod 42 is “F2”, the force for expanding the cylinder rod 42 is “B × pb”, and the force for expanding the cylinder rod 42 is “A”. Xpa + F2 ". For this reason, the hydraulic pump 13 is controlled so that the force “B × pb” for contracting the cylinder rod 42 exceeds the force “A × pa + F2” for extending the cylinder rod 42, and discharged from the hydraulic pump 13. The cylinder rod 42 is contracted by increasing the hydraulic pressure “pb” on the rod chamber 41b side by the hydraulic oil.

(Electric drive assist)
Next, when the electric motor 51 assists the electric drive in the expansion / contraction drive of the hydraulic actuator 40, first, the solenoid portion 53 moves the projection portion 54 in the direction in which the projection portion 54 projects in accordance with a command from the controller 58. The portion 54 is fitted into the thread groove 52 a of the feed screw portion 52, and the expansion and contraction operation of the cylinder rod 42 can be assisted by the rotational drive of the feed screw portion 52.

  In this state, the switch 57 is closed according to a command from the controller 58 so that the electric motor 51 can be driven. Then, the output voltage of the voltage regulator 56 is controlled by a target voltage command from the controller 58, and the voltage value and application time, that is, the assist amount output to the electric motor 51 are controlled along with the rotation direction of the electric motor 51. .

  In the case where the electric actuator is not assisted in the expansion / contraction drive of the hydraulic actuator 40, the projection 54 is moved by the solenoid 53 in the direction of the solenoid 53, that is, in the sinking direction according to a command from the controller 58. The fitting of the feed screw portion 52 to the screw groove 52a is released.

(Flow characteristics)
Next, the flow characteristics of the hydraulic pump 13 when the hydraulic actuator 40 is driven to extend and contract by the hydraulic pump 13 will be described.

  FIG. 4 is a PQ diagram showing the maximum discharge flow rate line (pump characteristics) of the hydraulic pump 13, and shows the case where the engine 12 has rotational speeds of Na, Nb and Nc (Na <Nb <Nc). Then, as shown in FIG. 4, as the pump discharge pressure of the hydraulic pump 13 increases, the curve portion A in which the pump discharge flow rate of the hydraulic pump 13 gradually decreases, the higher the rotation speed, There is a tendency to shift to a higher pump discharge pressure side.

  That is, in FIG. 4, the hydraulic oil discharged from the hydraulic pump 13 has a pump discharge flow rate equal to or lower than the maximum discharge amount line referenced from the rotation speed of the hydraulic pump 13 and the pump discharge pressure when discharged. It means that there is no margin in the output of the hydraulic pump 13 as the flow rate approaches the pump maximum discharge flow rate corresponding to the pump discharge pressure at that time.

(Driving method)
Next, a method for driving the hydraulic actuator 40 will be described with reference to FIG.

  As shown in FIG. 5, this drive method increases the operation amount of the hydraulic actuator 40 in the discharge pressure region of the curve portion A where the pump maximum discharge flow rate of the hydraulic pump 13 decreases in accordance with the pump discharge pressure. Assist by raising. Here, FIG. 5 (a) shows a pump maximum discharge flow diagram, FIG. 5 (b) shows a lever operation amount of the operation lever 4 in time series, and FIG. 5 (c) shows a target converted into a flow rate. The cylinder speed, pump discharge flow rate, and assist amount are shown in time series. Times t1 and t2 in FIGS. 5B and 5C indicate arbitrary times, and time passes in the order of time t1 and time t2. Time t2 indicates the time when the pump discharge amount reaches the pump maximum discharge flow rate at that time. From the viewpoint of simplifying the description, the pump discharge pressure from time t1 to time t2 is constant.

  In this driving method, when the pump discharge flow rate of the hydraulic pump 13 reaches the pump maximum discharge flow rate at that time, the expansion / contraction drive of the hydraulic actuator 40 is assisted. That is, when the pump maximum discharge flow rate line of the hydraulic pump 13 is the curve 1 in FIG. 5C, the time after the time t2 when the assist of the expansion / contraction driving of the hydraulic actuator 40 is started is the curve 1 By driving the hydraulic actuator 40 along the curve 2 that is the total flow rate with the assist amount, the actual cylinder speed a of the hydraulic actuator 40 can be set to the target cylinder speed c.

(Assist control)
Next, an assist method for assisting with the electric motor 51 when the hydraulic actuator 40 is driven to extend and contract with the hydraulic pump 13 will be described with reference to FIG.

  First, a predetermined operating lever 4 is operated by an operator who operates the hydraulic excavator 1 to cause the cylinder rod 42 of the hydraulic actuator 40 of any one of the boom cylinder 6, the arm cylinder 7 and the bucket cylinder 8 to be extended and retracted. Then, the lever operation amount detector 61 determines whether the operation target actuator operated by the operation lever 4 is the hydraulic actuator 40 that can be electrically assisted by the electric motor 51 (step 1).

  If it is determined in step 1 that the operation target actuator is the hydraulic actuator 40 that can be electrically assisted (step 2), the switch 57 is closed by an instruction from the controller 58, and is turned off. (Step 3). On the other hand, when it is determined in step 1 that the operation target actuator is not the hydraulic actuator 40 that can be electrically assisted, the assist control of the hydraulic actuator 40 ends.

  Next, the lever operation amount of the operation lever 4 is detected by the lever operation amount detector 61 (step 4). The detected value of the lever operation amount of the operation lever 4 detected by the lever operation amount detector 61 is related to the target cylinder speed a of the target hydraulic actuator 40 based on the lever operation amount of the operation lever 4. The flow rate is converted and compared with reference to a reference table (not shown) set in advance, and a target cylinder speed a, which is a reference value targeted by the current hydraulic actuator 40, is calculated (step 5).

  Thereafter, the cylinder speed detector 65 measures and detects the actual cylinder speed c, which is the actual speed of the cylinder rod 42 of the hydraulic actuator 40 (step 6), and then calculates the target cylinder calculated in step 5 A deviation amount e (e = ac) between the speed a and the actual cylinder speed c is calculated (step 7). Here, the actual cylinder speed c is the number of rotations of the electric motor 51 when the cylinder rod 42 of the hydraulic actuator 40 is driven to extend and contract in a state where the protrusion 54 is fitted in the thread groove 52a of the feed screw portion 52. It can also be calculated from

  Then, it is determined whether this deviation amount e is positive (e> 0), that is, whether the actual cylinder speed c is lower than the target cylinder speed a (step 8). If this deviation amount e is determined to be positive, Proceed to step 9. On the other hand, when it is determined that the deviation amount e is not positive (e ≦ 0), the assist control of the hydraulic actuator 40 ends. If the deviation amount e is determined to be positive, the target voltage V1 of the electric motor 51 is calculated by multiplying the deviation amount e and a predetermined constant gain g (step 9).

  Here, the gain g is different for each specification of the hydraulic actuator 40, and is a predetermined table determined in advance so as to be the optimum target voltage V1 when the hydraulic actuator 40 is electrically driven and assisted. As for the target voltage V1, when the target voltage V1 is output to the electric motor 51, the driving force for driving the cylinder rod 42 of the hydraulic actuator 40 is used to extend the cylinder rod 42. The voltage can be increased by the load force F1 acting in the contracting direction of 42 or the load force F2 acting in the extending direction of the cylinder rod 42 when the cylinder rod 42 is contracted. The

  Thereafter, the pump discharge pressure detecting unit 62 detects the pump discharge pressure that is the pressure of the hydraulic oil discharged from the hydraulic pump 13, and the pump discharge flow rate detecting unit 63 detects the hydraulic oil discharged from the hydraulic pump 13. The pump discharge flow rate, which is the flow rate, is detected, and the engine speed detector 64 detects the engine speed (step 10).

  For example, as shown in FIG. 4, in the pump maximum discharge flow rate diagram of the hydraulic pump 13 with respect to a plurality of revolutions of the engine 12, refer to the flow diagram at the number of revolutions closest to the current number of revolutions of the engine 12. Then, the pump maximum discharge flow rate of the hydraulic pump 13 is calculated (step 11). In step 11, the pump maximum discharge flow rate is calculated by complementing the flow rates referenced from the two pump maximum discharge flow lines closest to the current rotational speed of the engine 12 and the plurality of pump maximum discharge flow lines. You can also

  Thereafter, it is determined whether or not the pump discharge flow rate detected by the pump discharge flow rate detection unit 63 has reached the calculated maximum pump discharge flow rate at the present time (step 12). If it is determined in step 12 that the current pump discharge flow rate of the hydraulic pump 13 detected by the pump discharge flow rate detection unit 63 has reached the maximum pump discharge flow rate, the target voltage for driving the electric motor 51 is determined. The maximum value is limited to V1 (step 13).

  This maximum value restriction is performed so that an abnormal voltage is not applied to the electric motor 51. On the other hand, if it is determined in step 12 that the current pump discharge flow rate of the hydraulic pump 13 detected by the pump discharge flow rate detection unit 63 has not reached the pump maximum discharge flow rate, the assist control of the hydraulic actuator 40 is performed. End.

  Thereafter, it is determined whether or not the target voltage V1 is 0 or more (V1> 0) (step 14). When the target voltage V1 is 0 or more, the solenoid unit 53 is driven by a command from the controller 58 to project the projection. 54 is protruded and fitted into the thread groove 52a of the feed screw portion 52 (step 15). In this state, the final target voltage V that has been adjusted to the target voltage V1 by the voltage regulator 56 in accordance with a command from the controller 58 is output to the electric motor 51 (step 16).

  As a result, when the electric motor 51 supplied with the target voltage V1 is driven and the feed screw portion 52 is rotationally driven in a predetermined direction with a predetermined torque, the electric screw 51 is fitted in the thread groove 52a of the feed screw portion 52. The protruding portion 54 is pushed by the thread groove 52a by the circumferential rotation of the feed screw portion 52, and gradually moves in the axial direction of the cylinder rod 42 of the hydraulic actuator 40. Therefore, the hydraulic drive of the hydraulic actuator 40 is electrically assisted, and the driving force when the cylinder rod 42 is driven to extend and contract by the hydraulic pump 13 can be increased by the electric power of the electric motor 51. The actual cylinder speed c can be brought close to the target cylinder speed a.

  Furthermore, after the target voltage V is output to the electric motor 51 in step 16 and the electric power assisting of the expansion / contraction drive of the cylinder rod 42 of the hydraulic actuator 40 is performed, the process returns to step 4 to detect the lever operation amount of the operation lever 4 again. Then, the electric assist control from step 4 to step 16 is repeated. That is, when the operation of the operation lever 4 is stopped and returned to the neutral position, the lever operation amount detected in step 4 becomes 0 and the target voltage V becomes 0, so that the assist control of the hydraulic actuator 40 ends. Become.

<Effect>
Here, in the case of the hydraulic actuator 40 driven only by supply and discharge of the hydraulic oil supplied from the hydraulic pump 13, the driving force of the hydraulic actuator 40 is controlled by the hydraulic oil pressure, and the cylinder of the hydraulic actuator 40 is controlled. The speed at which the cylinder rod 42 is expanded and contracted is controlled by the flow rate of the hydraulic oil supplied to the tube 41. The hydraulic pump 13 is connected to the engine 12 that is a driving force generation source, and hydraulic oil discharged from the hydraulic pump 13 is supplied to the hydraulic actuator 40. The pump output of the hydraulic pump 13 is determined by the product of the pump discharge pressure of the hydraulic oil discharged from the hydraulic pump 13 and the pump discharge flow rate, and depends on the output of the engine 12.

  For this reason, it is necessary to change the pump discharge flow rate according to the pump discharge pressure of the hydraulic pump 13 so as not to exceed the maximum output of the engine 12. In particular, when the hydraulic actuator 40 is used in the excavator 1, from the viewpoint of workability of the front work machine 5, a constant pump discharge flow rate is maintained from 0 to a predetermined pressure of the pump discharge pressure of the hydraulic pump 13. Although it is possible, the pump discharge flow rate is generally reduced in proportion to the pump discharge pressure above a predetermined pressure. For this reason, at the time of a high load operation in which the pump discharge pressure is equal to or higher than a predetermined pressure, the speed at which the cylinder rod 42 of the hydraulic actuator 40 is expanded and contracted becomes slow, and the operation speed is reduced.

  Therefore, in the first embodiment described above, the cylinder rod when the cylinder rod 42 is driven to extend and contract with the lever operation amount of the operation lever 4 and the hydraulic oil discharged from the hydraulic pump 13 according to the lever operation amount. The actual cylinder speed c of 42 is detected. When the actual cylinder speed c is lower than a preset target cylinder speed a corresponding to the amount of lever operation by operating the operation lever 4, the electric motor 51 is driven. The feed screw 52 is rotated to push the projection 54 of the cylinder rod 42 to increase the driving force when the cylinder rod 42 is driven to extend and contract, and the actual cylinder speed c of the cylinder rod 42 approaches the target cylinder speed a. ing.

  As a result, the hydraulic actuator 40 is supplied and discharged with hydraulic oil so that the expansion / contraction drive of the hydraulic actuator 40 reaches the target cylinder speed a determined according to the operation amount when the operation lever 4 is operated. A driving force is applied to the cylinder rod 42 of the hydraulic actuator 40 by an assist device 50 using an electric motor 51 of a power source different from that of the hydraulic pump 13 that drives the rod 42 to expand and contract, thereby enhancing the expansion and contraction driving of the cylinder rod 42. Can assist. Therefore, the actual cylinder speed c when the cylinder rod 42 is driven to extend and contract by the hydraulic pump 13 can be brought closer to the target cylinder speed a more appropriately. Therefore, the cylinder rod 42 of the hydraulic actuator 40 is driven to extend and contract during high pump load work where the pump discharge pressure increases and the pump discharge flow rate decreases due to the increase in the work load due to the pump output of the hydraulic pump 13. It is possible to suppress a decrease in the actual cylinder speed c when the operation is performed, and to prevent a decrease in work speed.

  Further, when the actual cylinder speed c of the cylinder rod 42 of the hydraulic actuator 40 is lower than the target cylinder speed a, the pump discharge flow rate of the hydraulic pump 13 is detected, and the detected pump discharge flow rate is the pump flow rate of the hydraulic pump 13. Only when the maximum discharge flow rate has been reached, the electric motor 51 is driven to assist the expansion and contraction drive of the cylinder rod 42, and the drive force of the cylinder rod 42 is increased.

  Therefore, the electric motor 51 is driven to assist the expansion / contraction drive of the cylinder rod 42 only when the pump discharge flow rate of the hydraulic pump 13 that increases the necessity of assisting the expansion / contraction drive of the cylinder rod 42 reaches the maximum pump discharge flow rate. Therefore, the extension / contraction drive assist of the cylinder rod 42 can be reliably performed with a simpler configuration. In the case where the hydraulic actuator 40 is used in the hydraulic excavator 1 and the pump discharge pressure is higher than a predetermined pressure from the viewpoint of the pump output of the hydraulic pump 13, the pump discharge flow rate is decreased in proportion to the pump discharge pressure. Even if it exists, pump discharge pressure falls by reaching the pump maximum discharge flow rate. Therefore, when the pump maximum discharge flow rate is reached, the electric motor 51 is driven to assist the expansion / contraction drive of the cylinder rod 42, whereby the expansion / contraction drive assist of the cylinder rod 42 can be appropriately performed.

  Here, as an assist device 50 for assisting the expansion and contraction driving of the cylinder rod 42, a projection 54 attached to the cylinder rod 42 is fitted in a thread groove 52a provided on the outer periphery of the feed screw portion 52. The feed screw portion 52 is rotationally driven by the electric motor 51. As a result, by the rotational driving of the feed screw portion 52, the projection 54 fitted in the screw groove 52a of the feed screw portion 52 is pushed by the screw groove 52a, and the cylinder rod 42 to which the projection 54 is attached is attached. A driving force different from the driving force by supplying and discharging the hydraulic oil from the hydraulic pump 13 can be applied, and the cylinder rod 42 can be gradually moved in the axial direction.

  Therefore, the driving force when the cylinder rod 42 is extended and contracted by supplying and discharging the hydraulic oil from the hydraulic pump 13 can be increased by the electric power from the electric motor 51, and the actual cylinder speed c of the cylinder rod 42 is set as a target. Since the cylinder speed a can be approached, the expansion and contraction drive of the cylinder rod 42 by supplying and discharging the hydraulic oil from the hydraulic pump 13 can be reliably assisted with a simple configuration.

[Second Embodiment]
FIG. 7 is a schematic view showing an actuator according to the second embodiment of the present invention. The second embodiment is different from the first embodiment described above in the first embodiment in which the feed screw portion 52 is rotationally driven by the electric motor 51, and the protruding portion is formed by the screw groove 52 a of the feed screw portion 52. In the second embodiment, the endless chain 71 is driven to rotate by the electric motor 51 with respect to the assist device 50 configured to increase the driving force of the cylinder rod 42 of the hydraulic actuator 40 by pushing 54. The assist device 50 </ b> A increases the driving force of the cylinder rod 42 of the hydraulic actuator 40 by pushing the portion 54. In the second embodiment, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals.

  As shown in FIG. 7, the assist device 50 </ b> A has a drive sprocket 72 that is a drive wheel attached to an output shaft 51 b that is a drive shaft of the electric motor 51. The drive sprocket 72 has a rotation axis orthogonal to the expansion / contraction direction of the cylinder rod 42 and rotates toward the expansion / contraction direction of the cylinder rod 42. A driven sprocket 73 as a freewheel is attached to a position at a predetermined distance from the driving sprocket 72 toward the tip of the cylinder rod 42. Similar to the driving sprocket 72, the driven sprocket 73 has a rotation axis orthogonal to the expansion / contraction direction of the cylinder rod 42, and rotates in the expansion / contraction direction of the cylinder rod 42.

  Further, an endless chain 71 is wound between the driving sprocket 72 and the driven sprocket 73, and the chain 71 is rotationally driven by the rotation of the driving sprocket 72. On the outer peripheral side of the chain 71, locking teeth 71a as engaging portions are provided at equal intervals in the circumferential direction of the chain 71. A cylinder rod is connected to any locking tooth 71a of the chain 71. The protrusion 54 attached to 42 is fitted and locked to increase the driving force when the cylinder rod 42 is driven to extend and contract.

  As described above, in the second embodiment, the assist device 50A that assists the expansion and contraction drive of the cylinder rod 42 of the hydraulic actuator 40 is attached to the cylinder rod 42 on one of the engagement teeth 71a on the outer periphery of the chain 71. The chain 71 is rotationally driven by the electric motor 51 in a state where the protrusions 54 are fitted and locked. As a result, when the chain 71 is rotationally driven, the projection 54 is pushed by the locking teeth 71a of the chain 71, and hydraulic oil is supplied from the hydraulic pump 13 to the cylinder rod 42 to which the projection 54 is attached. A driving force different from the driving force due to exhaust can be applied.

  Therefore, as in the first embodiment, the driving force when the cylinder rod 42 is extended and contracted by supplying and discharging the hydraulic oil from the hydraulic pump 13 can be increased by the electric power from the electric motor 51. The actual cylinder speed c of 42 can be brought close to the target cylinder speed a. Therefore, the expansion and contraction drive of the cylinder rod 42 by supplying and discharging the hydraulic oil from the hydraulic pump 13 can be reliably assisted with a relatively simple configuration using the chain 71.

[Third Embodiment]
FIG. 8 is a schematic view showing an actuator according to the third embodiment of the present invention. The third embodiment is different from the first embodiment described above in the first embodiment in which the feed screw portion 52 is rotationally driven by the electric motor 51, and the protruding portion is formed by the screw groove 52a of the feed screw portion 52. In the third embodiment, the drive gear 81 is driven to rotate by the electric motor 51, and the drive gear 81 is driven in a flat plate form with respect to the assist device 50 that pushes 54 to increase the drive force of the cylinder rod 42 of the hydraulic actuator 40. The assist device 50B is configured to increase the driving force of the cylinder rod 42 by moving the member 82. In the third embodiment, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals.

  As shown in FIG. 8, the assist device 50 </ b> B has a drive gear 81 attached to a drive shaft 51 a of an electric motor 51. The drive gear 81 has a plurality of gears 81a formed at equal intervals on the outer peripheral surface. The drive gear 81 is attached with a substantially flat drive member 82 having a longitudinal direction along the longitudinal direction of the cylinder rod 42 of the hydraulic actuator 40. The drive member 82 is attached so as to be movable along the expansion / contraction direction of the cylinder rod 42, and a fixed piece 82 a bent toward the thickness direction of the drive member 82 is provided at the distal end side of the drive member 82. The fixing piece 82 a is provided and locked inside the pin insertion portion 42 b of the cylinder rod 42.

  Further, on one side surface of the drive member 82 facing the drive gear 81 side, a gear-shaped portion 82b that can mesh with each gear 81a of the drive gear 81 is provided. The gear-shaped portion 82b is provided on one side opposite to the side on which the fixed piece 82a of the driving member 82 is provided, and a plurality of gears are equally spaced from one end side to the other end side of the one side surface. 82c is formed. The gear 81 a of the drive gear 81 is engaged with the gear-shaped portion 82 b of the drive member 82. Therefore, when the drive gear 81 is rotated by the electric motor 51, the gear shape portion 82 b of the drive member 82 is expanded and contracted in the expansion / contraction direction of the cylinder rod 42 with the rotation of the drive gear 81. Therefore, the driving force when the cylinder rod 42 is driven to extend and contract can be increased.

  As described above, in the third embodiment, as the assist device 50B, the drive gear 81 is meshed with the gear-shaped portion 82b of the drive member 82 fixed to the cylinder rod 42, and this drive gear 81 is engaged with the electric motor 51. To rotate. As a result, due to the rotational drive of the drive gear 81, the gear shape portion 82b of the drive member 82 is pushed by the gear 81a of the drive gear 81, and the hydraulic pump 13 moves against the cylinder rod 42 to which the drive member 82 is fixed. A driving force different from the driving force due to the supply and discharge of the hydraulic oil can be applied.

Therefore, as in the first embodiment, the driving force when the cylinder rod 42 is extended and contracted by supplying and discharging the hydraulic oil from the hydraulic pump 13 can be increased by the electric power from the electric motor 51. The actual cylinder speed c of 42 can be brought close to the target cylinder speed a. Therefore, the expansion and contraction drive of the cylinder rod 42 by supplying and discharging the hydraulic oil from the hydraulic pump 13 can be reliably assisted with a relatively simple configuration using the drive gear 81.
In any of the first to third embodiments, the rotational speed of the electric motor 51 and the speed of the cylinder rod 42 are in a proportional relationship. Therefore, the cylinder speed detector 65 is omitted and the electric motor 51 is omitted. The speed of the cylinder rod 42 may be calculated from the number of rotations. Thereby, the configuration of the embodiment can be further simplified.

[Fourth Embodiment]
FIG. 9 is a schematic view showing an actuator according to the fourth embodiment of the present invention. 10A and 10B are explanatory diagrams showing the driving method of the actuator, where FIG. 10A is a pump maximum discharge flow diagram, FIG. 10B is a graph showing lever operation amounts in time series, and FIG. 10C is a target cylinder speed converted to flow rate. It is a graph which shows time-sequentially the pump discharge flow rate and the assist amount. FIG. 11 is a graph showing an assist adjustment gain table of the actuator. FIG. 12 is a flowchart showing a driving method of the actuator.

  The fourth embodiment differs from the first embodiment described above in that the first embodiment mechanically applies the rotational drive of the electric motor 51 to the cylinder rod 42 of the hydraulic actuator 40, and the driving force of the cylinder rod 42. In the fourth embodiment, an assist pump 91 that is a hydraulic pump different from the hydraulic pump 13 that drives the hydraulic actuator 40 is driven by the electric motor 51, and The assist device 50C increases the driving force of the cylinder rod 42 by supplying and discharging the discharged hydraulic oil. In the fourth embodiment, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals.

  As shown in FIG. 9, the assist device 50 </ b> C includes an assist pump 91 for assisting that is another fluid pressure pump different from the hydraulic pump 13. The assist pump 91 is supplied with the output of the electric motor 51 and is driven by the electric motor 51. The discharge flow path 91 a of the assist pump 91 is connected to the direction control valve 94 via a check valve 92 and a relief valve 93. Here, the check valve 92 is a backflow prevention valve that prevents backflow of the hydraulic oil discharged from the assist pump 91. Further, the relief valve 93 regulates the maximum discharge pressure of the hydraulic oil discharged from the assist pump 91. Specifically, when the pump discharge pressure of the assist pump 91 becomes larger than the pump maximum discharge pressure of the assist pump 91, the relief valve 93 uses a part of the hydraulic oil discharged from the assist pump 91 as the hydraulic oil. It escapes to the tank 14, and makes this pump discharge pressure below the maximum discharge pressure.

  Furthermore, the direction control valve 94 is connected to the ports 41c and 41d of the bottom chamber 41a and the rod chamber 41b of the hydraulic actuator 40 through an oil passage on the actuator port side, and controls the flow of hydraulic oil to the hydraulic actuator 40. Therefore, the direction control valve 94 switches the hydraulic oil discharged from the assist pump 91 to the bottom chamber 41a or the rod chamber 41b of the hydraulic actuator 40. The directional control valve 94 is connected to switching driving force generators 95 and 96 for switching and driving the directional control valve 94 via signal lines 95a and 96a, respectively. These switching driving force generation devices 95 and 96 are connected to the controller 58 via signal lines 95b and 96b, respectively, and in response to commands from the controller 58 via the signal lines 95b and 96b, these switching driving force generation devices 95 and 96, respectively. , 96 are appropriately driven, and the directional control valve 94 is controlled to be switched by a fixed capacity hydraulic oil output from the switching driving force generators 95, 96.

(Hydraulic drive assist)
Next, the operation principle when assisting the hydraulic actuator 40 with the assist pump 91 will be described.

  In the case of assisting the hydraulic drive of the hydraulic actuator 40 with the assist pump 91, the switch 57 is closed by a command from the controller 58 so that the electric motor 51 can be driven. Then, the output voltage of the voltage regulator 56 is controlled by a target voltage command from the controller 58, and the voltage value and application time, that is, the assist amount output to the electric motor 51 are controlled along with the rotation direction of the electric motor 51. .

  At this time, simultaneously with the control of the electric motor 51 by the controller 58, a command from the controller 58 is transmitted to the switching driving force control devices 95 and 96. In this case, for example, when the switching position of the direction control valve 95 is moved to a position where the assist pump 91 and the bottom chamber 41a of the hydraulic actuator 40 communicate with each other, that is, the cylinder rod 42 of the hydraulic actuator 40 is hydraulically assisted in the extending direction. In this case, the switching driving force control device 95 on the side that can be driven to the switching position that can communicate with the bottom chamber 41a of the directional control valve 94 is driven by the controller 58, and the switching driving force generation device 95 is driven. The switching position of the direction control valve 94 is controlled by the driving force generated in this way.

  In contrast, for example, when the switching position of the direction switching valve 94 is moved to a position where the assist pump 91 and the rod chamber 41b of the hydraulic actuator 40 communicate with each other, that is, the cylinder rod 42 of the hydraulic actuator 40 is hydraulically assisted in the contraction direction. In this case, the switching driving force control device 96 on the side that can be driven to the switching position where the direction control valve 94 can communicate with the rod chamber 41b is driven by the controller 58, and this switching driving force generation device 96 is driven. The switching position of the method control valve 94 is controlled by the driving force generated in step (b).

(Driving method)
Next, a method for driving the hydraulic actuator 40 will be described.

  First, in the first embodiment, when the pump discharge flow rate of the hydraulic pump 13 reaches the pump maximum discharge flow rate at that time, the expansion / contraction drive of the hydraulic actuator 40 is assisted. For this reason, the cylinder speed of the hydraulic actuator 40 becomes the curve 1 from time 0 to t2, and the behavior of the curve 2 after time t2. Therefore, the larger the deviation between the target cylinder speed a and the actual cylinder speed c until the time t2 when the pump discharge flow rate of the hydraulic pump 13 reaches the maximum pump discharge flow rate at that time, the larger the cylinder of the hydraulic actuator 40 is. The actual cylinder speed c before and after the assist of the expansion and contraction driving of the rod 42 is started varies greatly.

  Therefore, in the second embodiment, the cylinder rod 42 is controlled while suppressing fluctuations in the cylinder speed of the cylinder rod 42 of the hydraulic actuator 40 before and after the pump discharge flow rate of the hydraulic pump 13 reaches the pump maximum discharge flow rate at that time. Is assisted until the cylinder speed reaches the target cylinder speed a from the actual cylinder speed c.

  Specifically, in the second embodiment, as shown in FIG. 10, a discharge pressure region in which the pump maximum discharge flow rate of the hydraulic pump 13 decreases according to the pump discharge pressure of the hydraulic pump 13 (from time t1 to time). Also during t2), the operation amount of the hydraulic actuator 40 is increased to increase the driving force to assist. Here, FIG. 10 (a) shows a pump maximum discharge flow diagram, FIG. 10 (b) shows the lever operation amount of the operation lever 4 in time series, and FIG. 10 (c) shows the target converted to flow rate. Cylinder speed, pump discharge flow rate, and assist amount are shown in time series.

  Then, as shown by curve 3 in FIG. 10C, the hydraulic actuator 13 is controlled while suppressing fluctuations in the cylinder speed of the hydraulic actuator 40 before and after the pump discharge flow rate of the hydraulic pump 13 reaches the maximum pump discharge flow rate at that time. The actual cylinder speed c of the 40 cylinder rods 42 is assisted to the target cylinder speed a. Specifically, it is not determined whether the pump discharge flow rate of the hydraulic pump 13 has reached the maximum pump discharge flow rate at that time, and the assist control is not performed, but the pump discharge flow rate of the hydraulic pump 13 and the pump maximum flow rate at that time are not controlled. The assist amount adjustment gain i set in advance based on the relationship with the discharge flow rate is referred to. The assist adjustment gain i is multiplied by the target adjustment voltage i calculated by the same method as in the first embodiment described above. The target voltage V2 is set, and the electric motor 61 is driven with the target voltage V2, and the hydraulic actuator 40 is gradually assist-controlled.

  Here, as the assist adjustment gain i, for example, as shown in FIG. 11, the horizontal axis represents the ratio (flow rate ratio) between the pump discharge flow rate of the hydraulic pump 13 and the pump maximum discharge flow rate corresponding to the pump discharge pressure at that time. FIG. 10 is an adjustment table with a preset gain as a vertical axis. The assist adjustment gain i increases the rate of increasing the driving force for extending and retracting the cylinder rod 42 of the hydraulic actuator 40 based on the pump discharge pressure of the hydraulic pump 13. The flow rate ratio of the hydraulic pump 13 is calculated based on the pump discharge pressure because the pump maximum discharge flow rate of the hydraulic pump 13 changes according to the pump discharge pressure.

  At this time, by setting the assist adjustment gain i closer to 1 as the ratio of the pump discharge flow rate to the pump maximum discharge flow rate approaches 1, the hydraulic actuator increases as the pump discharge flow rate approaches the maximum pump discharge flow at that time. It is possible to gradually assist 40 expansion / contraction driving. The assist adjustment gain i is set to 0 when the pump discharge pressure of the hydraulic pump becomes the relief pressure.

(Assist control)
Specifically, as shown in FIG. 12, the assist method when the hydraulic actuator 40 is extended and contracted by the hydraulic pump 13 is the same as that in the first embodiment, as shown in FIG. After the target voltage V1 is calculated in step 9, the pump discharge pressure is detected by the pump discharge pressure detector 62 (step 21). Thereafter, a flow rate ratio corresponding to the pump discharge pressure is calculated based on the pump discharge pressure of the hydraulic pump 13, and the assist amount adjustment gain i based on the calculated flow rate ratio is referred to (step 22). The adjustment gain i is multiplied by the target voltage V1 to obtain the target voltage V2 (step 23).

  Thereafter, the maximum value is limited to the target voltage V2 as in step 13 of the first embodiment (step 24). When the target voltage V2 is 0 or more (step 25), a command from the controller 58 is issued. Then, one of the switching driving force generators 95 and 96 is driven, and the directional control valve 94 is switched and controlled by the fixed capacity hydraulic oil output from one of these switching driving force generators 95 and 96, and then the controller 58 The final target voltage V adjusted to the target voltage V2 by the voltage regulator 56 is output to the electric motor 51 by the command from (step 26).

  Here, in step 25, since the assist adjustment gain i is 0 when the pump discharge pressure of the hydraulic pump 13 is the relief pressure, the pump discharge pressure of the hydraulic pump 13 is determined by determining whether V2 is 0 or more. It is determined whether or not the pressure reaches the relief pressure. If it is determined in step 25 that the target voltage V2 is smaller than 0, the assist control of the hydraulic actuator 40 ends.

  As described above, the electric motor 51 to which the target voltage V2 is supplied is driven to drive the assist pump 91, and the supply of hydraulic oil discharged from the assist pump 91 causes the hydraulic oil to be supplied to the cylinder rod 42 of the hydraulic actuator 40. The supply / discharge flow rate can be increased. Accordingly, the hydraulic drive of the hydraulic actuator 40 is hydraulically assisted, and the driving force for driving the cylinder rod 42 of the hydraulic actuator 40 to extend and contract by the hydraulic pump 13 is an assist pump 91 having a power source different from that of the hydraulic pump 13. The actual cylinder speed c of the cylinder rod 42 can be brought close to the target cylinder speed a.

<Effect>
Here, in the first embodiment, the hydraulic actuator 40 is assisted when the pump discharge flow rate of the hydraulic pump 13 reaches the maximum pump discharge flow rate at that time. The behavior is that the curve 1 from 0 to the time t2 and the curve 2 after the time t2 are connected. In this case, the larger the deviation amount e between the target cylinder speed a and the actual cylinder speed c is reached by the time t2 when the pump discharge flow rate of the hydraulic pump 13 reaches the maximum pump discharge flow rate at that time, the greater the displacement of the hydraulic actuator 40. The actual cylinder speed c greatly fluctuates before and after the assist.

  On the other hand, in the case of the above-described fourth embodiment, the maximum pump discharge flow rate of the hydraulic pump 13 decreases according to the pump discharge pressure of the hydraulic pump 13 as shown by the curve 3 in FIG. In the discharge pressure range to be performed, specifically, from time t1 to time t2, the operation amount of the hydraulic actuator 40 is increased to assist the driving force to increase. As a result, fluctuations in the cylinder speed of the hydraulic actuator 40 before and after the pump discharge flow rate of the hydraulic pump 13 reaches the maximum pump discharge flow rate at that time can be suppressed, and the speed of the cylinder rod 42 of the hydraulic actuator 40 can be reduced. Thus, the target cylinder speed a can be approached more smoothly.

  Therefore, as the pump discharge pressure of the hydraulic pump 13 becomes higher, the rate of increasing the driving force for driving the cylinder rod 42 to expand and contract is increased in response to the increase of the assist amount for the expansion and contraction driving of the cylinder rod 42 of the hydraulic actuator 40. it can. That is, as the pump discharge flow rate of the hydraulic pump 13 approaches the pump maximum discharge flow rate, the expansion / contraction drive of the cylinder rod 42 of the hydraulic actuator 40 can be gradually assisted, and the expansion / contraction drive assist of the cylinder rod 42 is performed more appropriately. Can do.

  Further, based on the pump discharge pressure of the hydraulic pump 13, the assist amount adjustment gain i with respect to the ratio (flow ratio) between the pump discharge flow rate of the hydraulic pump 13 and the pump maximum discharge flow rate at that time is referred to. A target voltage V2 is obtained by multiplying the adjustment voltage i by the target voltage V1. For this reason, it is only necessary to detect the pump discharge pressure of the hydraulic pump 13 in step 21, and it is not necessary to detect the pump discharge flow rate of the hydraulic pump 13 and the rotational speed of the engine 12 as in the first embodiment. Therefore, the assist control of the hydraulic actuator 40 can be realized with a simpler configuration.

  Further, the electric motor 51 is driven by an assist pump 91 that is different from the hydraulic pump 13 that drives the hydraulic actuator 40, and hydraulic oil is supplied and discharged from the assist pump 91 to the bottom chamber 41 a and the rod chamber 41 b of the hydraulic actuator 40. The cylinder rod 42 of the hydraulic actuator 40 is assisted to extend and contract. As a result, a driving force different from the driving force applied to the cylinder rod 42 by the hydraulic pump 13 can be applied to the cylinder rod 42 by the assist pump 91.

  Therefore, the expansion / contraction drive of the cylinder rod 42 by supplying / discharging the hydraulic oil from the hydraulic pump 13 can be assisted by using the assist pump 91. Therefore, as the assist pump 91, for example, a hydraulic pump mounted for attachment, etc. By diverting a hydraulic pump or the like for driving the hydraulic actuator (not shown), it is possible to assist the expansion and contraction drive of the cylinder rod 42 of the hydraulic actuator 40 using the existing hydraulic pump mounted on the hydraulic excavator 1. . That is, when the hydraulic actuator 40 is used as the boom cylinder 6 or the bucket cylinder 8 and the boom cylinder 6 or the bucket cylinder 8 is driven by the first hydraulic pump 13a as shown in FIG. 2, the swing motor 3a is driven. The second hydraulic pump 13b can also be used as the assist pump 91.

[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 embodiments, the assist control of the hydraulic actuator 40 such as the arm cylinder 7 of the excavator 1 has been described. For example, a hydraulic actuator having a large load fluctuation other than the arm cylinder 7 of the excavator 1, and other wheel loaders. It can also be used as assist control for various hydraulic actuators used in work machines such as cranes.

  Further, the command from the controller 58 is transmitted via the signal lines 56a, 57a, 95b, 96b, etc., but the signal from the controller 58 is wirelessly transmitted without passing through these signal lines 56a, 57a, 95b, 96b, etc. It can also be set as the structure transmitted by. Further, the electric motor 51 is not driven by the power supply 55 mounted on the hydraulic excavator 1, but, for example, in an electrically driven hydraulic excavator for underground work, the electric motor 51 is driven by electric power supplied from the outside. It can also be set as the structure to make. As the power source 55 for driving the electric motor 51, an existing one mounted for starting the engine of the hydraulic excavator 1 can be used.

  In the first embodiment, the protrusion 52 attached to the cylinder rod 42 of the hydraulic actuator 40 is moved by the electromagnetic force formed by the solenoid 53. Alternatively, the hydraulic fluid can be moved by the hydraulic pressure of the hydraulic oil supplied from the hydraulic pump 13 or the like.

  Furthermore, the power supply 55, the voltage regulator 56, the switch 57, the controller 58, the lever operation amount detection unit 61, the pump discharge pressure detection unit 62, the pump discharge flow rate detection unit 63, the engine rotation number detection unit 64, and the assist device 50 are configured. The cylinder speed detection unit 65 may be provided outside the vehicle body of the hydraulic excavator 1 instead of being provided in the vehicle body such as the upper swing body 3 of the hydraulic excavator 1.

  Further, when the pump discharge flow rate detection unit 63 cannot detect the pump discharge flow rate of the hydraulic pump 13, the product of the hydraulic pump 13 volume and the rotational speed of the hydraulic pump 13 determines the hydraulic pump 13. The pump discharge flow rate can also be calculated. Furthermore, the pump discharge flow rate of the hydraulic pump 13 can be calculated based on the signal pressure for controlling the pump volume of the hydraulic pump 13 and the rotational speed of the engine 12.

[First Reference Form]
Next, a first reference embodiment of the hydraulic actuator related to the present invention will be described.

  FIG. 13 is a schematic view showing an actuator according to a first reference embodiment related to the present invention. FIG. 14 is a diagram illustrating a hydraulic circuit for driving the actuator. The first embodiment differs from the first embodiment described above in that the first embodiment is directed to an assist device 50 that assists the electric motor 51 to drive the hydraulic actuator 40 in the extending direction and the contracting direction. The first reference form is an assist device 50D that assists the electric motor 51 only to drive the hydraulic actuator 40 in the contracting direction. In the first reference embodiment, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals.

  The assist device 50D includes an electric motor 51, and a drive gear 81 is attached to an output shaft 51b of the electric motor 51. On the other hand, the cylinder rod 42 of the hydraulic actuator 40 includes a feed screw portion 101 in which a spiral thread groove 101a is formed on the outer peripheral surface, and a spherical joint and a spherical joint on the tip side that is one end side in the longitudinal direction of the feed screw portion 101. A spherical ball-shaped portion 102 is provided. The ball-shaped portion 102 is attached with a piston 103 serving as a head slidably inserted into the cylinder tube 41. The piston 103 is provided with a concave arc-shaped receiving portion 103a into which the ball-shaped portion 120 of the cylinder rod 42 is swingably and rotatably fitted. The ball-shaped portion 102 is swung and rotated on the receiving portion 103a. It is fitted and mounted movably. The piston 103 bisects the space in the cylinder tube 41 along the axial direction, and the space surrounding the end surface of the piston 103 in the cylinder tube 41 serves as the bottom chamber 41a. The receiving portion 103a side of the piston 103 A space surrounding the end surface of the cylinder tube 41 and the cylinder tube 41 is a rod chamber 41b.

  Further, the opening 41f on the rod chamber 41b side of the cylinder tube 41 is provided with a ball screw portion 104 that closes the opening 41f. At the center of the ball screw portion 104, there is provided an insertion hole 104b in which a screw groove 104a with which the screw groove 101a of the feed screw portion 101 of the cylinder rod 42 is engaged is formed in a spiral shape on the inner peripheral surface. In a state where the screw groove 101a of the feed screw portion 101 is fitted and screwed into the screw groove 104a of the insertion hole 104b, the feed screw portion 101 is inserted and attached to the insertion hole 104b. Therefore, the feed screw portion 101 rotates the feed screw portion 101 in the axial direction so that the screw groove 101a of the feed screw portion 101 is pushed by the screw groove 104a of the ball screw portion 104, and the feed screw portion 101 is The cylinder tube 41 is expanded and contracted along the axial direction.

  Further, a disc-shaped flange 105 having a larger outer diameter than the feed screw portion 101 of the cylinder rod 42 is concentric with the proximal end portion of the cylinder rod 42 opposite to the side where the ball-shaped portion 102 is provided. It is provided in the shape. The flange portion 105 is fitted in a space portion 106a provided in the bearing member 106 having the pin insertion portion 42b so as to be rotatable in the circumferential direction and is retained. Further, a disc-like drive gear 107 having a gear 107a formed on the outer peripheral surface is concentrically attached and fixed at a position near the flange portion 105 of the feed screw portion 101 of the cylinder rod 42.

  An electric motor 51 is attached to one side surface of the bearing member 106. The electric motor 51 is attached by engaging the gear 81a of the drive gear 81 attached to the output shaft 51b of the electric motor 51 while facing the gear 107a of the drive gear 107 of the cylinder rod 42. That is, the electric motor 51 is driven to rotate the drive gear 81 by driving the electric motor 51, whereby the drive gear 107 is rotationally driven by the drive gear 81. 42 is rotated, and the rotation of the cylinder rod 42 pushes the thread groove 101a of the feed screw portion 101 of the cylinder rod 42 into the thread groove 104 of the ball screw portion 104 of the cylinder tube 41, thereby rotating the feed screw portion 101. The cylinder tube 41 is moved in the axial direction.

  Therefore, by rotating the cylinder rod 42 in the circumferential direction by screwing the ball screw portion 104 of the cylinder tube 41 and the feed screw portion 101 of the cylinder rod 42, the cylinder rod 42 is moved in the axial direction with respect to the cylinder tube 41. Can move. When the cylinder rod 42 of the hydraulic actuator 40 is extended, the hydraulic oil discharged from the hydraulic pump 13 is sent to the bottom chamber 41a, and the cylinder rod 42 is rotated in the circumferential direction by the pressure driving force of the hydraulic pump 13. It can be extended and driven. When the cylinder rod 42 is contracted, the electric motor 51 is driven, and the cylinder rod 42 is rotated counterclockwise as viewed from above by the electric power driving force of the electric motor 51. It can be driven to contract while rotating in the circumferential direction. At this time, the piston 103 and the bearing member 106 are fitted between the ball-shaped portion 102 of the cylinder rod 42 and the receiving portion 103a of the piston 103, and between the flange portion 105 of the cylinder rod 42 and the space portion 106a of the shaft-shaped member 106. By fitting, the ball slides and follows between the ball-shaped portion 102 and the receiving portion 103a and between the flange portion 105 and the space portion 106a without receiving the rotational force of the cylinder rod 42.

(Driving method)
Next, a method for driving the hydraulic actuator 40 will be described.

  First, when the cylinder rod 42 of the hydraulic actuator 40 is extended, the controller 58 opens the switch 57 to turn it off, and at the same time, the hydraulic oil supplied from the hydraulic pump 13 is supplied to the cylinder tube via the port 41c. The piston 103 of the cylinder rod 42 is pushed by the hydraulic pressure supplied to the bottom chamber 41a, and the driving force in the extending direction is generated in the cylinder rod 42.

  Then, the cylinder rod 42 rotates in the circumferential direction toward the direction in which the cylinder rod 42 extends, and the cylinder screw 41 rotates with respect to the ball screw portion 104 of the cylinder tube 41 by the feed screw portion 101 of the cylinder rod 42. The thread groove 101a of the feed screw portion 101 is pushed by the thread groove 104a of the ball screw portion 104 toward the direction in which the rod 42 extends, and the cylinder rod 42 gradually extends. At this time, since the switch 57 is in an OFF state, an electrical load caused by driving the electric motor 51 can be minimized.

  On the other hand, when the cylinder rod 42 of the hydraulic actuator 40 is contracted, the controller 58 closes the switch 57 to turn it on and drives the electric motor 51 at the same time as a switching valve (not shown). Thus, the communication destination of the bottom chamber 41 a of the cylinder tube 41 is switched to the hydraulic oil tank 14, and the hydraulic oil in the bottom chamber 41 a is pushed out by the piston 103 and can be discharged to the hydraulic oil tank 14.

  Then, by driving the electric motor 51, the cylinder rod 42 rotates in the circumferential direction in the direction in which the cylinder rod 42 contracts via the drive gear 107, and the cylinder tube formed by the feed screw portion 101 of the cylinder rod 42. 41, the screw groove 101a of the feed screw portion 101 is pushed by the screw groove 104a of the ball screw portion 104 in the direction in which the cylinder rod 42 is contracted, and the cylinder rod 42 is moved. It gradually shrinks.

(Hydraulic drive)
Furthermore, when this hydraulic actuator 40 is used as the boom cylinder 6, arm cylinder 7, and bucket cylinder 8 of the hydraulic excavator 1, these hydraulic actuators 40 are driven by a hydraulic drive device 11 </ b> D shown in FIG. 14. The directional control valves 21, 22, 23, and 32 of the hydraulic drive device 11 </ b> D have a two-position switching structure, and between the bottom chamber 41 a of the boom cylinder 6 and the hydraulic oil tank 14, Discharge valves 108a, 108b, and 108c are attached between the bottom chamber 41a and the hydraulic oil tank 14 and between the bottom chamber 41a of the bucket cylinder 8 and the hydraulic oil tank 14, respectively. Each of these discharge valves 108a, 108b, 108c is a switching valve whose switching position is a two-position switching configuration.

  The discharge valve 108a is connected to the first operating lever 4a through a signal pressure oil passage 109a. The first operation lever 4a is connected to the boom direction control valve 23 through a signal pressure oil passage 109b. Therefore, the signal pressure of the boom lowering command for driving the boom 5a to be lowered in response to the operation of the first operation lever 4a is sent to the discharge valve 108a via the signal pressure oil passage 109a, and the switching position of the discharge valve 108a. Is driven to an opening position where the bottom chamber 41a of the boom cylinder 6 communicates with the hydraulic oil tank. Also, a boom raising command signal pressure for driving the boom 5a to be raised in response to the operation of the first operating lever 4a is sent to the boom direction control valve 23 via the signal pressure oil passage 109b. The switching position of the directional control valve 23 is driven to a driving position where the bottom chamber 41a of the boom cylinder 6 communicates with the discharge oil passage 15a of the first hydraulic pump 13a.

  Next, the discharge valve 108b is connected to the second operation lever 4b via a signal pressure oil passage 109c. The second operation lever 4b is connected to each of the first and second arm direction control valves 22 and 32 via a signal pressure oil passage 109d. Therefore, the signal pressure of the arm dump command for driving the arm 5b in the dumping direction to push the arm 5b to the opposite side to the cab 3b side by operating the second operation lever 4b to the discharge valve 108b through the signal pressure oil passage 109c. The switching position of the discharge valve 108b is driven to an opening position where the bottom chamber 41a of the arm cylinder 7 communicates with the hydraulic oil tank 14. Further, the signal pressure of the arm cloud command for driving the arm 5b in the cloud direction to draw the arm 5b toward the cab 3b by operating the second operation lever 4b is for the first and second arms via the signal pressure oil passage 109d. The directional control valves 22 and 32 are sent to the first and second arm directional control valves 22 and 32, and the bottom chamber 41a of the arm cylinder 7 is discharged from the first or second hydraulic pumps 13a and 13b. It drives to the drive position connected to oil path 15a, 15b.

  Further, the discharge valve 108c is connected to the first operation lever 4a via a signal pressure oil passage 109e. The first operation lever 4a is connected to the bucket direction control valve 21 through a signal pressure oil passage 109f. Therefore, the signal pressure of the bucket dump command for driving the bucket 5d in the dumping direction to push the bucket 5d to the opposite side to the cab 3b side by operating the first operation lever 4a is applied to the discharge valve 108c via the signal pressure oil passage 109e. The switching position of the discharge valve 108c is driven to an opening position where the bottom chamber 41a of the bucket cylinder 8 communicates with the hydraulic oil tank 14. In addition, the signal pressure of the bucket cloud command for driving the bucket 5d in the cloud direction to draw the bucket 5d toward the cab 3b by operating the first operation lever 4a to the bucket direction control valve 21 via the signal pressure oil passage 109f. The switching position of the bucket directional control valve 21 is driven to a driving position where the bottom chamber 41a of the bucket cylinder 8 communicates with the discharge oil passage 15a of the first hydraulic pump 13a.

  On the other hand, pressure detectors 110a, 110b, and 110c are attached to the signal pressure oil passages 109a, 109c, and 109e, respectively. These pressure detectors 110a, 110b, and 110c are signal pressure sensors that detect the presence or absence of signal pressure supplied to the signal pressure oil passages 109a, 109c, and 109e. When signal pressure is detected in these signal pressure oil passages 109a, 109c, and 109e, the switch 57 is turned on by a command from the controller 58 to drive the electric motor 51 and detect these signal pressures. The cylinder rod 42 of the boom cylinder 6, the arm cylinder 7 and the bucket cylinder 8 connected to the signal pressure oil passages 109a, 109c and 109e is rotated in the direction in which the cylinder rod 42 contracts. Thus, the cylinder rod 42 is driven to contract.

(Drive control)
Next, a case where the hydraulic actuator 40 is used as the bucket cylinder 8 will be described as an example of drive control of the hydraulic drive device 11D.

  First, when operating the bucket 5d of the hydraulic excavator 1 in the dumping direction, the first operation lever 4a is operated, and the signal pressure output by the operation of the first operation lever 4a is changed to the signal pressure oil passage 109e. The switching position of the discharge valve 108c is driven to an opening position where the bottom chamber 41a of the bucket cylinder 8 communicates with the hydraulic oil tank 14. At this time, since the signal pressure output from the first operating lever 4a and supplied to the bucket direction control valve 21 through the signal pressure oil passage 109f is not generated, the bucket direction control valve is pressed by an elastic body, for example. 21 is a neutral position where the bottom chamber 41a of the bucket cylinder 8 is not communicated with the discharge oil passage 13c of the first hydraulic tank 13a.

  Then, the supply of the signal pressure to the signal pressure oil passage 109e is detected by the pressure detector 110c, and it is determined that the controller 58 dumps the bucket 5d by the detection of the signal pressure by the pressure detector 110c. The switch 57 is turned on by a command from the controller 58, and the electric motor 51 is driven. Here, based on the magnitude of the signal pressure detected by the pressure detector 110c, voltage adjustment is performed by the voltage regulator 56 according to a command from the controller 58, and the voltage adjusted by the voltage regulator 56 is electrically driven. Applied to the motor 51, the driving force of the electric motor 51 is controlled.

  By driving the electric motor 51, the cylinder rod 42 is rotated in the direction in which the cylinder rod 42 is contracted. At this time, the hydraulic oil in the bottom chamber 41a of the hydraulic actuator 40 is discharged to the hydraulic oil tank 14 through the discharge valve 108c along with the contraction operation of the cylinder rod 42, whereby the bucket cylinder 8 5d can be electrically driven in the dump direction.

  On the other hand, when the bucket 5d of the hydraulic excavator 1 is operated in the cloud direction, the first operation lever 4a is operated, and the signal pressure output by the operation of the first operation lever 4a is changed to the signal pressure oil path. 109 f is sent to the bucket direction control valve 21, and the switching position of the bucket direction control valve 21 is driven to a drive position where the bottom chamber 41 a of the bucket cylinder 8 communicates with the discharge oil passage 15 a of the first hydraulic tank 13 a. Is done. At this time, since the signal pressure output from the first operating lever 4a and supplied to the discharge valve 108c via the signal pressure oil passage 109e is not generated, the switching position of the discharge valve 108c is set by, for example, pressing by an elastic body. The closed position is such that the bottom chamber 41 a of the bucket cylinder 8 does not communicate with the hydraulic oil tank 14.

  As a result, the hydraulic oil supplied to the bottom chamber 41a is not discharged to the hydraulic oil tank 14 via the discharge valve 108c, so that the hydraulic oil discharged from the first hydraulic tank 13a is supplied to the bottom chamber 41a. The piston 103 in the bottom chamber 41a is pressed by the hydraulic pressure of the hydraulic oil, and the cylinder rod 42 is rotated in the direction in which the cylinder rod 42 extends. At this time, as the cylinder rod 42 rotates, the flange portion 105 of the cylinder rod 42 idles in the space portion 106a of the bearing member 106, and the drive gear 81 of the electric motor 51 also idles. 8, the bucket 5d can be hydraulically driven in the cloud direction.

(Function and effect)
Here, the boom cylinder 6, the arm cylinder 7 and the bucket cylinder 8 of the general hydraulic excavator 1 are for controlling the expansion / contraction force only by the hydraulic oil pressure. Occurrence of pressure loss in the hydraulic circuit due to hydraulic oil supply / discharge control is inevitable. Particularly when a plurality of hydraulic actuators 40 are driven at the same time, the hydraulic oil is preferentially given to the hydraulic actuator 40 having a smaller driving load. In some cases, a pressure loss is intentionally generated so that is not supplied.

  On the other hand, when it is considered that pressure loss of hydraulic oil is completely eliminated, it is conceivable that the hydraulic actuator 40 is driven by electric power other than hydraulic pressure, for example. However, particularly in the case of the boom cylinder 6, arm cylinder 7 or bucket cylinder 8 of the hydraulic excavator 1, the cylinder rod 42 of the hydraulic actuator 40 is extended in the extending direction due to the pressure receiving area of the piston 103 of the hydraulic actuator 40. When driving, the hydraulic actuator 49 requires the electric motor 51 to increase in size and output because the hydraulic actuator 49 is driven by the electric motor 51. An increase is considered.

  Therefore, as in the first reference embodiment, the hydraulic actuator 40 used as the boom cylinder 5, arm cylinder 6, and bucket cylinder 8 of the hydraulic excavator 1 is driven in the extension direction, and the hydraulic actuator 40 is contracted. The driving in the direction is electric driving, and the driving of the electric motor 51 drives the cylinder rod 42 in the contracting direction. As a result, since the hydraulic actuator 40 is driven in the extending direction, the hydraulic circuit for supplying and discharging the hydraulic oil cannot be completely eliminated. By making the driving in the contracting direction that does not require a driving force electric driving, it is possible to reduce the pressure loss of the hydraulic oil, and to increase the size and output of the electric motor 51.

  Further, by adopting the hydraulic actuator 40 having the above-described configuration, the switching positions of the directional control valves 21, 22, 23, and 32 that control the driving of the hydraulic actuator 40 are set, and the bottom chamber 41a of the hydraulic actuator 40 is connected to the hydraulic pump 13. A two-position switching structure between a drive position for communicating with the discharge oil passage 15 and a neutral position where the bottom chamber 41a of the hydraulic actuator 40 is not communicated with the discharge oil passage 15 of the hydraulic pump 13 can be achieved. Therefore, a driving position for communicating the rod chamber 41a of the hydraulic actuator 40 with the discharge oil passage 15 of the hydraulic pump 13, which is conventionally required as a switching position of the directional control valves 21, 22, 23, 32, is not necessary. These directional control valves 21, 22, 23, and 32 can be simplified from the three-position switching structure to the two-position switching structure, and can be reduced in size. Further, since a related oil passage for communicating the rod chamber 41a of the hydraulic actuator 40, which has been conventionally required, with the discharge oil passage 15 of the hydraulic pump 13 is unnecessary, the hydraulic pressure of the hydraulic drive device 11D that drives the hydraulic actuator 40 is eliminated. The circuit configuration can be simplified.

In the first reference embodiment, the electric motor 51 is used for electric drive only when the cylinder rod 42 of the hydraulic actuator 40 is contracted. However, the cylinder rod 42 of the hydraulic actuator 40 is hydraulically operated. When the hydraulic oil discharged from the pump 13 is extended, the electric motor 51 is driven in the reverse direction, and the cylinder rod 42 is rotated in the direction in which the cylinder rod 42 extends, whereby the cylinder rod 42 is driven to extend. The driving force at the time of performing can be increased, and the assist control in the first and fourth embodiments is possible.
[Second Reference Form]
Next, a second reference embodiment of the hydraulic actuator related to the present invention will be described.

  FIG. 15 is a diagram showing a hydraulic circuit for driving the actuator according to the second embodiment related to the present invention. The second reference embodiment differs from the first reference embodiment described above in terms of the opening characteristics of the boom direction control valve 23, the first and second arm direction control valves 22, 32, and the bucket direction control valve 21. The hydraulic drive device 11E is provided with signal pressure controllers 201a, 201b, and 201c that are the same and control the signal pressure supplied to these directional control valves 21, 22, 23, and 32. In the second reference embodiment, the same or corresponding parts as those in the first reference embodiment are denoted by the same reference numerals.

  The signal pressure controller 201a controls the signal pressure supplied to the boom direction control valve 23, and is connected to the boom direction control valve 23 via the signal pressure oil passage 109b. The signal pressure controller 201b controls the signal pressure supplied to the first and second arm direction control valves 22 and 32, and the first and second arm direction control valves via the signal oil passage 109d. 22 and 32. Further, the signal pressure controller 201c controls the signal pressure supplied to the bucket direction control valve 21, and is connected to the bucket direction control valve 21 via a signal oil passage 109f.

  Each of these signal pressure controllers 201a, 201b, and 201c is connected to a controller 202 as a control unit, and controls signal pressures output from these signal pressure controllers 201a, 201b, and 201c according to commands from the controller 202. To do. Further, the controller 202 includes a pressure detector 203a that detects a signal pressure during an operation of lowering the boom 5a, a pressure detector 203b that detects a signal pressure during a cloud operation that pulls the arm 5b, and a cloud operation that pulls the bucket 5d. A pressure detector 203c for detecting the signal pressure of the hour is connected to each.

  The pressure detector 203a is connected to the first operation lever 4a, and detects the signal pressure output from the first operation lever 4a when the first operation lever 4a is operated in the boom lowering direction. The pressure detector 203b is connected to the second operation lever 4b, and detects the signal pressure output from the second operation lever 4b when the second operation lever 4b is operated in the direction of clouding the arm 5b. . Further, the pressure detector 203c is connected to the first operation lever 4a, and when the first operation lever 4a is operated in a direction to cloud the bucket 5d, the signal pressure output from the first operation lever 4a is obtained. To detect. Then, the controller 202 controls the corresponding signal pressure controllers 201a, 201b, and 201c based on the signal pressures detected by the pressure detectors 203a, 203b, and 203c, and the signal pressure controllers 201a, 201b, The signal pressure output from 201c is controlled.

<Effect>
As described above, in the second reference embodiment, for example, when the hydraulic actuator 40 is used as the bucket cylinder 8, the first operation lever 4a is operated, and the first operation lever 4a is operated in a direction to cloud the bucket 5d. When this occurs, the signal pressure output from the first operating lever 4a is detected by the pressure detector 203c. Based on the signal pressure detected by the pressure detector 203c, the controller 202 controls the signal pressure output from the signal pressure controller 201c. Thereafter, the signal pressure output from the signal pressure controller 201c is supplied to the bucket direction control valve 21 via the signal pressure oil passage 109f, and the switching position of the bucket direction control valve 21 is set to the bucket cylinder 8 The bottom chamber 41a is driven to a driving position for communicating with the discharge oil passage 15a of the first hydraulic pump 13a. Therefore, the hydraulic oil discharged from the first hydraulic pump 13a is supplied to the bottom chamber 41a, the piston 103 is pushed by the hydraulic pressure of this hydraulic oil, the cylinder rod 42 is driven to extend, and the bucket 5d is driven in the cloud direction. Is done.

  Therefore, the signal pressure output from the first or second operation lever 4a or 4b is determined only by the operation amount of the first or second operation lever 4a or 4b. Furthermore, even when the opening ratio of any one of the directional control valves 21, 22, 23, 32 does not reach the target opening ratio, the signal pressure output from the first or second operation lever 4a, 4b is detected. In addition to the pressure detectors 203a, 203b, and 203c, the signal pressure supplied to the directional control valves 21, 22, 23, and 32 is controlled based on the signal pressures detected by the pressure detectors 203a, 203b, and 203c. By using the signal pressure controllers 201a, 201b, and 201c, the directional control valves 21, 22, 23, and 32 can be controlled more accurately. At the same time, the opening characteristics of the directional control valves 21, 22, 23 and 32 for controlling the boom cylinder 6, the arm cylinder 7 and the bucket cylinder 8 can be made the same, and the directional control valves 21, 22, 23 and 32 have the same configuration. Therefore, the configuration of the hydraulic drive device 11E can be further simplified.

DESCRIPTION OF SYMBOLS 1 Hydraulic excavator 2 Lower traveling body 2a, 2b Traveling motor 2c, 2d Traveling apparatus 3 Upper revolving body 3a Turning motor 3b Operation room 3c Engine room 3d Counterweight 4 Operation lever 4a 1st operation lever 4b 2nd operation lever 4c 3rd operation Lever 4d Fourth operation lever 5 Front work machine 5a Boom 5b Arm 5c Four-bar linkage mechanism 5d Bucket 6 Boom cylinder 6a Cylinder tube 6b Cylinder rod 7 Arm cylinder 7a Cylinder tube 7b Cylinder rod 8 Bucket cylinder 8a Cylinder tube 8b Cylinder rod 11, 11D, 11E Hydraulic drive device 12 Engine 13 Hydraulic pump 13a First hydraulic pump 13b Second hydraulic pump 14 Hydraulic oil tank 15 Discharge oil passage 15a, 15b Discharge oil passage 16 Control valve Devices 17a, 17b Center bypass line 18 Main relief valve 20 First valve section 21 Bucket direction control valve 22 First arm direction control valve 23 Boom direction control valve 24 First travel direction control valve 30 Second valve section 31 Direction control valve for turning 32 Direction control valve for second arm 33 Direction control valve for second traveling 40 Hydraulic actuator 41 Cylinder tube 41a Bottom chamber 41b Rod chamber 41c, 41d Port 41e Pin insertion portion 41f Opening portion 42 Cylinder rod 42a Head 42b Pin insertion part 50, 50A, 50B, 50C Assist device 51 Electric motor 51a Signal line 51b Output shaft 52a Screw groove 52 Feed screw part 53 Solenoid part 53a Signal line 54 Projection part 55 Power supply 56 Voltage regulator 56a Signal line 57 H 57a Signal line 58 Controller 61 Lever operation amount detection unit 61a Signal line 62 Pump discharge pressure detection unit 62a Signal line 63 Pump discharge flow rate detection unit 63a Signal line 64 Engine speed detection unit 64a Signal line 65 Cylinder speed detection unit 65a Signal Wire 71 Chain 71a Locking tooth 72 Drive sprocket 73 Driven sprocket 81 Drive gear 81a Gear 82 Drive member 82a Fixed piece 82b Gear shape part 82c Gear 91 Assist pump 91a Discharge flow path 92 Check valve 93 Relief valve 94 Directional control valve 95 , 96 Switching drive force generator 95a, 96a Signal line 95b, 96b Signal line 101 Feed screw part 101a Screw groove 102 Ball-shaped part 103 Piston 103a Receiving part 104 Ball screw part 104a Screw groove 104b Insertion hole 105鍔 portion 106 bearing member 106a space portion 107 drive gear 107a gear 108a, 108b, 108c discharge valve 109a, 109b, 109c, 109d, 109e, 109f signal pressure oil passage 110a, 110b, 110c pressure detector 201a, 201b, 201c signal pressure Controller 202 Controller 203a, 203b, 203c Pressure detector

Claims (6)

A method for driving an actuator having a rod that can be extended and retracted,
A detection step of detecting an operation amount for extending and retracting the rod, and an actual speed of the rod when the rod is extended and driven according to the operation amount;
An assisting step for increasing the driving force for driving the rod to extend and contract when the detected actual speed is lower than a target speed set in advance according to the operation amount, and bringing the actual speed of the rod closer to the target speed; ,
An actuator driving method comprising: The method for driving an actuator according to claim 1,
The rod is configured such that pressure oil corresponding to the operation amount is supplied from a hydraulic pump to be expanded and contracted and can be expanded and contracted by an electric motor,
The driving method of an actuator characterized in that the assist step increases a driving force for driving the electric motor to extend and contract the rod when the detected actual speed of the rod is lower than the target speed. The method for driving an actuator according to claim 1,
The rod is configured such that pressure oil corresponding to the operation amount is supplied from a hydraulic pump to be expanded and contracted, and can be expanded and contracted by pressure oil supplied from another hydraulic pump different from the hydraulic pump,
In the assist step, when the detected actual speed of the rod is lower than the target speed, the driving force for driving the other hydraulic pump to drive the rod to extend and contract is increased. Method. The actuator driving method according to claim 2, wherein
The assist step detects a discharge flow rate of the pressure oil discharged from the hydraulic pump, and when the detected discharge flow rate reaches the maximum discharge flow rate of the hydraulic pump, a driving force for extending and retracting the rod is generated. An actuator driving method characterized by comprising the steps of: The actuator driving method according to claim 2, wherein
The assist step detects the discharge pressure of the pressure oil discharged from the hydraulic pump, and based on the detected discharge pressure, increases the rate of increasing the driving force for driving the rod to extend and contract. Driving method. In the actuator drive method according to claim 3,
The assist step detects a discharge pressure of the pressure oil discharged from the hydraulic pump, refers to an adjustment table based on the detected discharge pressure, and drives the other hydraulic pump to drive the rod to extend and contract. An actuator driving method characterized by increasing driving force.