Construction machine

Abstract

Provided is a construction machine capable of charging an electricity storage device using regenerative power of an electric motor, and capable of suppressing deterioration of the electricity storage device. This excavator is provided with: a motor; the controller outputs a rotating speed instruction; an inverter that controls the rotational speed of the motor in accordance with a rotational speed command from the controller; and a power storage device that outputs drive power to the inverter when the motor accelerates and inputs regenerative power from the inverter when the motor decelerates. When the motor decelerates, the controller outputs a rotation speed command to the inverter such that the reduction rate of the rotation speed of the motor is equal to or less than a predetermined limit value.

Description

TECHNICAL FIELD

[0001] The present application relates to construction machines such as excavators. BACKGROUND

[0002] Patent Document 1 discloses an excavator as one of construction machines. The excavator of Patent Document 1 is provided with an electric storage device (for example, constituted by a lithium ion battery), an electric motor and a pilot pump driven by electric power of the electric storage device, a hydraulic pump driven by the electric motor, a hydraulic actuator, a control valve that controls flow of hydraulic oil from the hydraulic pump to the hydraulic actuator, and an operation device that operates the control valve. The operation device generates pilot pressure using discharge pressure of the pilot pump, and outputs the generated pilot pressure to operate the control valve.

[0003] The excavator of Patent Document 1 is provided with an on-off valve provided between the pilot pump and the operation device, and a cut-off lever that switches the on-off valve to a cut-off state and a communication state by up-down turning operation. In a case where the cut-off lever is operated upward to switch the on-off valve to a cut-off position, the operation device cannot generate pilot pressure, and the drive of the hydraulic actuator is prevented. On the other hand, in a case where the cut-off lever is operated downward to switch the on-off valve to a communication state, the operation device can generate pilot pressure, and the drive of the hydraulic actuator is allowed.

[0004] The excavator of Patent Document 1 is provided with a controller that, according to operation of the cut-off lever (in other words, switching of the on-off valve), makes the rotation speed of the electric motor variable by means of an inverter. The controller, in a case where the cut-off lever is operated to the lower side (in other words, in a case where the on-off valve is switched to a communication position), outputs a rotation speed command to the inverter in such a manner that the rotation speed of the electric motor becomes a target value. On the other hand, in a case where the cut-off lever is operated to the upper side (in other words, in a case where the on-off valve is switched to a cut-off position), outputs a rotation speed command to the inverter in such a manner that the rotation speed of the electric motor becomes zero (in other words, in such a manner that the electric motor is stopped).

[0005] PRIOR ART DOCUMENT

[0006] PATENT DOCUMENT

[0007] Patent Document 1: International Publication No. 2019-208370 SUMMARY

[0008] If the electric power regenerated at the time of stop and deceleration of the electric motor of the excavator described in the above-described Patent Document 1 is used to charge the electric storage device, energy saving can be achieved. However, the allowable value (upper limit value) of the charging current of the electric storage device is determined in accordance with the voltage and temperature of the electric storage device. Also, when the electric storage device is charged using the regenerated electric power of the electric motor, if a charging current exceeding the aforementioned allowable value is generated, the electric storage device is accelerated in deterioration.

[0009] The present invention provides a construction machine capable of charging a power storage device using regenerative electric power of an electric motor and suppressing degradation of the power storage device.

[0010] In order to achieve the above-mentioned purpose, the engineering machinery of the present invention comprises: an electric motor; a controller which outputs a speed instruction; an inverter which controls the speed of the electric motor according to the speed instruction from the controller; and a power storage device which outputs driving power to the inverter when the electric motor accelerates and inputs regenerative power from the inverter when the electric motor decelerates. In the engineering machinery, the controller outputs the speed instruction to the inverter when the electric motor decelerates in such a manner that the reduction rate of the speed of the electric motor becomes below a prescribed limit value.

[0011] Effects of the Invention

[0012] According to the present invention, the power storage device can be charged using the regenerative electric power of the electric motor, and degradation of the power storage device can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a side view showing the structure of an excavator in one embodiment of the present invention.

[0014] Figure 2 This is a diagram showing the configuration of a drive system of an excavator according to one embodiment of the present invention.

[0015] Figure 3 This is a diagram showing the configuration of a control system for an excavator according to one embodiment of the present invention.

[0016] Figure 4 This is a diagram showing the functional configuration of a controller in one embodiment of the present invention together with related devices.

[0017] Figure 5 This is a flowchart showing the processing procedure of the controller in one embodiment of the present invention.

[0018] Figure 6 It is a time chart showing changes in the rotation speed and current of the motor in one embodiment of the present invention and a comparative example. DETAILED DESCRIPTION

[0019] An embodiment of the present invention will be described with reference to the accompanying drawings.

[0020] Figure 1 It is a side view showing the structure of the excavator in this embodiment.

[0021] The excavator of this embodiment includes a traveling body 1, a vertically movable front portion ( Figure 1The left side of the shovel 2, the rotating body 3 provided on the upper side of the traveling body 1 so as to be rotatable in the left and right directions, and the front side of the rotating body 3 ( Figure 1 The working device 4 is connected to the left side of the vehicle. The traveling unit 1 travels by rotating the left and right traveling motors (not shown). The blade 2 moves by extending and retracting the blade cylinder (not shown). The rotating unit 3 rotates by rotating the rotating motor (not shown).

[0022] The working mechanism 4 includes a support column 5 rotatably connected to the front side of the rotating structure 3, a boom 6 rotatably connected to the support column 5, an arm 7 rotatably connected to the front end of the arm 6, and a bucket 8 rotatably connected to the front end of the arm 7. The support column 5 is rotated by extending and retracting a support cylinder (not shown). The boom 6 is rotated by extending and retracting a boom cylinder 9. The arm 7 is rotated by extending and retracting an arm cylinder 10. The bucket 8 is rotated by extending and retracting a bucket cylinder 11.

[0023] The revolving structure 3 includes a revolving frame 12 forming a basic structure, a roofed cab 13 provided on the upper side of the revolving frame 12, and a rear side ( Figure 1 The counterweight 14 is located on the right side of the cab 13. A locking lever 15 is provided at the entrance of the cab 13, which can be operated by the driver to the raised position (the position allowing the driver to board and disembark) and the lowered position (the position restricting the driver to board and disembark). Inside the cab 13, there is a driver's seat 16 for the driver to sit on, and a plurality of operating devices (details will be described later) and a speed setting device 17 (see the following). Figure 3 ).

[0024] The excavator of this embodiment includes a drive system that drives multiple hydraulic actuators (specifically, the left and right travel motors, blade cylinder, swing motor, support cylinder, boom cylinder 9, arm cylinder 10, and bucket cylinder 11) according to operations of multiple operating devices. Figure 2 It is a diagram showing a configuration related to the arm cylinder 10 in the configuration of the drive system of the excavator in this embodiment.

[0025] The drive system of this embodiment includes an electric motor 20, a hydraulic pump 21 and a pilot pump 22 driven by the electric motor 20, a control valve 23 that controls the flow (specifically, direction and flow rate) of hydraulic oil from the hydraulic pump 21 to the boom cylinder 10, and an operating device 24 that operates the control valve 23.

[0026] The operating device 24 includes an operating lever 25 that can be operated by the driver, a pilot valve 26A that reduces the discharge pressure of the pilot pump 22 to generate a pilot pressure according to the amount of operation of the operating lever 25 to one side, and a pilot valve 26B that generates a pilot pressure by reducing the discharge pressure of the pilot pump 22 according to the amount of operation of the operating lever 25 to the other side.

[0027] If the operator operates the lever 25 to one side, the pilot pressure generated by the pilot valve 26A according to the operation amount thereof is output to the pressure-receiving portion 27A of the control valve 23, and the control valve 23 is switched to the switching position on the right side as illustrated. Thus, the hydraulic oil ejected from the hydraulic pump 21 is supplied to the piston rod side of the arm cylinder 10, and the arm cylinder 10 is driven (contracted).

[0028] If the operator operates the lever 25 to the other side, the pilot pressure generated by the pilot valve 26B according to the operation amount thereof is output to the pressure-receiving portion 27B of the control valve 23, and the control valve 23 is switched to the switching position on the left side as illustrated. Thus, the hydraulic oil ejected from the hydraulic pump 21 is supplied to the cylinder bottom side of the arm cylinder 10, and the arm cylinder 10 is driven (extended).

[0029] Further, the structure relating to the other hydraulic actuators (in detail, the travel motor, the boom cylinder, the swing motor, the boom cylinder 9, or the bucket cylinder 11) is substantially the same as that relating to the arm cylinder 10. That is, the corresponding control valve is switched according to the pilot pressure from the corresponding operating device, the hydraulic oil ejected from the hydraulic pump is supplied to the other hydraulic actuator, and the other hydraulic actuator is driven.

[0030] The drive system of the present embodiment has the lock device that switches between the lock state in which the drive of the hydraulic actuator is prohibited and the lock release state in which the drive of the hydraulic actuator is permitted, and the lock device is provided with the hydraulic control check valve 28 provided between all the operating devices and the pilot pump 22.

[0031] The hydraulic control check valve 28 is switched according to the operation of the lock lever 15 described above. For a detailed description, the lock switch 29 is provided in the lock lever 15. If the lock lever 15 is operated to the lock position (raised position), the lock switch 29 becomes the open state. Thus, the solenoid portion of the hydraulic control check valve 28 is not energized, and therefore the hydraulic control check valve 28 becomes the cut-off position on the right side as illustrated, and all the operating devices do not introduce the ejection pressure of the pilot pump 22. Therefore, all the operating devices cannot generate the pilot pressure, and the drive of all the hydraulic actuators is prohibited (lock state).

[0032] On the other hand, if the lock lever 15 is operated to the lock release position (lowered position), the lock switch 29 becomes the closed state. Thus, the solenoid portion of the hydraulic control check valve 28 is energized, and the hydraulic control check valve 28 is switched to the communication position on the left side as illustrated, and all the operating devices introduce the ejection pressure of the pilot pump 22. Therefore, all the operating devices can generate the pilot pressure, and the drive of all the hydraulic actuators is permitted (lock release state). Further, the lock switch 29 corresponds to the detector that detects the switching of the lock state and the lock release state of the lock device.

[0033] The excavator of the present embodiment has the control system that performs the drive control and the regeneration control of the electric motor 20.Figure 3 is a diagram showing the structure of the control system of the excavator in the present embodiment. Figure 4 is a block diagram showing the functional structure of the controller in the present embodiment together with the associated devices.

[0034] The control system of the present embodiment is provided with a controller 30 which inputs signals from a rotation speed setting device 17 and a lock switch 29, sets a rotation speed command based on these signals and outputs it, an inverter 31 which controls the rotation speed of the motor 20 according to the rotation speed command from the controller 30, and an electric storage device 32 which outputs driving power to the inverter 31 when the motor 20 is accelerated and inputs regenerative power from the inverter 31 when the motor 20 is decelerated. The electric storage device 32 is constituted by, for example, a lithium ion battery.

[0035] The rotation speed setting device 17 has, for example, a dial which can be operated by the driver and a potentiometer which outputs a signal corresponding to the operation position of the dial, in order to set the reference rotation speed of the motor 20 within a prescribed range (for example, 2400 to 1200 rpm).

[0036] The controller 30 has a processor which executes processing in accordance with a program, a memory which stores the program and data, and the like. As the greatest feature of the present embodiment, the controller 30 has a function of outputting the rotation speed command to the inverter 31 in such a way that the deceleration rate of the rotation speed of the motor 20 becomes equal to or lower than a prescribed limit value when the motor 20 is decelerated.

[0037] As the functional structure, the controller 30 has a reference rotation speed operation section 33 which operates the reference rotation speed of the motor 20 based on the signal from the rotation speed setting device 17, a difference operation section 34 which operates the difference between the current rotation speed of the motor 20 and a prescribed lock state rotation speed, a selection section 35 which selects the smaller one of the difference operated in the difference operation section 34 and a prescribed limit value, an interpolated rotation speed operation section 36 which operates the interpolated rotation speed by subtracting the difference selected in the selection section 35 from the current rotation speed of the motor 20, and a rotation speed command setting section 37 which sets the rotation speed command based on the signal from the lock switch 29, the operation result of the reference rotation speed operation section 33 or the interpolated rotation speed operation section 36, and the like, and outputs the set rotation speed command to the inverter.

[0038] Next, the processing sequence of the controller 30 of the present embodiment will be described with reference to Figure 5 Figure 5 is a flowchart showing the processing sequence of the controller 30 in the present embodiment. Furthermore, Figure 5 The processing content shown in FIG. 8 is performed at regular intervals.

[0039] ​In step S1, the rotation speed command setting section 37 of the controller 30 determines whether the hydraulic control check valve 28 is in the communication position (in other words, whether the lock device is in the lock release state) based on the signal from the lock switch 29. In the case where the hydraulic control check valve 28 is in the communication position (in other words, the lock device is in the lock release state), the processing proceeds to step S2. In step S2, the rotation speed command setting section 37 sets the reference rotation speed calculated in the reference rotation speed calculation section 33 as the rotation speed command, and outputs it to the inverter 31.

[0040] In the case where the hydraulic control check valve 28 is in the shut-off position (in other words, the lock device is in the lock state) in step S1, the processing proceeds to step S3. In step S3, the rotation speed command setting section 37 acquires the current rotation speed of the motor 20 from the inverter 31, or acquires it as the previous rotation speed command, and determines whether the current rotation speed of the motor 20 is the prescribed lock state rotation speed. Immediately after the hydraulic control check valve 28 is switched from the communication state to the shut-off state (in other words, immediately after the lock device is switched from the lock release state to the lock state), the current rotation speed of the motor 20 is not the prescribed lock state rotation speed, so the processing proceeds to steps S4 to S6.

[0041] In step S4, the difference calculation section 34 of the controller 30 calculates the difference between the current rotation speed of the motor 20 and the prescribed lock state rotation speed (zero in this embodiment). Then, the processing proceeds to step S5, and the selection section 35 selects the smaller one of the difference calculated in the difference calculation section 34 and the prescribed limit value. The interpolation rotation speed calculation section 36 calculates the interpolation rotation speed by subtracting the difference or the limit value selected in the selection section 35 from the current rotation speed of the motor 20. Then, the processing proceeds to step S6, and the rotation speed command setting section 37 sets the interpolation rotation speed calculated in the interpolation rotation speed calculation section 36 as the rotation speed command, and outputs it to the inverter 31.

[0042] The processing of steps S4 to S6 is repeated until the current rotation speed of the motor 20 becomes the prescribed lock state rotation speed. That is, the controller 30 outputs the rotation speed command in such a manner that the reduction rate of the rotation speed command (and further the reduction rate of the rotation speed of the motor 20) is limited to be equal to or lower than the prescribed limit value, and the rotation speed command is reduced in stages until the rotation speed of the motor 20 becomes the prescribed lock state rotation speed. As a specific example, a case where the processing contents shown in FIG. 6 are assumed to be performed by the controller 30 every 1 second, the reference rotation speed is 1200 rpm, and the prescribed limit value is 500 rpm is described. Figure 5

[0043] ​After the lockup device has just switched from the lockup release state to the lockup state, the difference calculating section 34 calculates the difference between the current rotational speed of the motor 20 (1200 rpm) and the prescribed lockup state rotational speed (0 rpm). The selection section 35 selects the smaller one of the difference calculated in the difference calculating section 34 (1200 rpm) and the prescribed limit value (500 rpm). The interpolated rotational speed calculating section 36 calculates the interpolated rotational speed by subtracting the limit value selected in the selection section 35 (500 rpm) from the current rotational speed of the motor 20 (1200 rpm). The rotational speed command setting section 37 sets the interpolated rotational speed calculated in the interpolated rotational speed calculating section 36 (700 rpm) as the rotational speed command, and outputs it to the inverter 31.

[0044] After 1 second has elapsed, the difference calculating section 34 calculates the difference between the current rotational speed of the motor 20 (700 rpm) and the prescribed lockup state rotational speed (0 rpm). The selection section 35 selects the smaller one of the difference calculated in the difference calculating section 34 (700 rpm) and the prescribed limit value (500 rpm). The interpolated rotational speed calculating section 36 calculates the interpolated rotational speed by subtracting the limit value selected in the selection section 35 (500 rpm) from the current rotational speed of the motor 20 (700 rpm). The rotational speed command setting section 37 sets the interpolated rotational speed calculated in the interpolated rotational speed calculating section 36 (200 rpm) as the rotational speed command, and outputs it to the inverter 31.

[0045] After 1 second has elapsed, the difference calculating section 34 calculates the difference between the current rotational speed of the motor 20 (700 rpm) and the prescribed lockup state rotational speed (0 rpm). The selection section 35 selects the smaller one of the difference calculated in the difference calculating section 34 (700 rpm) and the prescribed limit value (500 rpm). The interpolated rotational speed calculating section 36 calculates the interpolated rotational speed by subtracting the limit value selected in the selection section 35 (500 rpm) from the current rotational speed of the motor 20 (700 rpm). The rotational speed command setting section 37 sets the interpolated rotational speed calculated in the interpolated rotational speed calculating section 36 (200 rpm) as the rotational speed command, and outputs it to the inverter 31.

[0046] If the current rotational speed of the motor 20 becomes the prescribed lockup state rotational speed in step S3, the processing proceeds to step S7. In step S7, the rotational speed command setting section 37 sets the lockup state rotational speed as the rotational speed command, and outputs it to the inverter 31.

[0047] Next, the use of Figure 6 The effects of the present embodiment will be described. Figure 6 is a time chart showing the changes in the rotational speed and the current of the motor in the present embodiment and the comparative example. Furthermore, in Figure 6In the present embodiment, the positive current indicates the driving current from the inverter 31 to the motor 20, and the negative current indicates the regenerative current from the motor 20 to the inverter 31.

[0048] The controller of the comparative example does not limit the reduction rate of the rotational speed command (and further the reduction rate of the rotational speed of the motor 20) to be below the prescribed limit value. That is, when the lock device is switched from the lock release state to the locked state (time t), the rotational speed command is immediately set to zero and output to the inverter 31. Therefore, as shown by the dashed line of FIG. 6, the rotational speed of the motor 20 sharply decreases, and in conjunction therewith, the regenerative current of the motor 20 momentarily significantly increases. Also, if the electric power is regenerated by the motor 20 to charge the electric storage device 32, the charging current of the electric storage device 32 exceeds the allowable value, resulting in accelerated deterioration of the electric storage device 32. Figure 6

[0049] On the other hand, the controller 30 of the present embodiment, when the lock device is switched from the lock release state to the locked state (time t), outputs the rotational speed command in such a manner that the reduction rate of the rotational speed command (and further the reduction rate of the rotational speed of the motor 20) is limited to be below the prescribed limit value and the rotational speed command is gradually reduced until the rotational speed of the motor 20 is zero. Therefore, as shown by the solid line of FIG. 6, the rotational speed of the motor 20 slowly decreases, and in conjunction therewith, the regenerative current of the motor 20 momentarily increases, but does not significantly increase or decrease. Also, if the electric power is regenerated by the motor 20 to charge the electric storage device 32, the charging current of the electric storage device 32 does not exceed the allowable value, preventing the deterioration of the electric storage device 32. Figure 6

[0050] Therefore, in the present embodiment, the electric storage device 32 can be charged using the regenerative electric power of the motor 20, and the deterioration of the electric storage device 32 can be suppressed.

[0051] Further, in the above-described one embodiment, a case where the operation device has a pilot valve that generates a pilot pressure corresponding to the operation amount of the operation lever and outputs the same to the pressure-receiving portion of the control valve, and the lock device is the hydraulic control check valve 28 provided on the primary side of the pilot valve, is described as an example, but is not limited thereto. Alternatively, the operation device can have a potentiometer that generates an operation signal corresponding to the operation amount of the operation lever and outputs the same to the solenoid portion of the control valve, and the lock device can be a relay provided on the primary side of the potentiometer.

[0052] In addition, in the above-described one embodiment, a case where the controller 30 stops the motor 20 when the lock device is switched from the lock release state to the locked state (i.e., the prescribed locked state rotational speed is zero) is described as an example, but is not limited thereto. Alternatively, the controller 30 can decelerate the motor 20 when the lock device is switched from the lock release state to the locked state. That is, the prescribed locked state rotational speed can be a value smaller than the reference rotational speed and greater than zero. ​​

[0053] Further, in the above-described one embodiment, the case where the controller 30 limits the reduction rate of the rotational speed command to be equal to or lower than the prescribed limit value when the lock device is switched from the lock release state to the lock state and the rotational speed command is reduced has been described as an example, but the present application is not limited thereto. The controller 30 can limit the reduction rate of the rotational speed command to be equal to or lower than the prescribed limit value when the rotational speed command is reduced in accordance with the operation of the drive / stop switch. Alternatively, the controller 30 can limit the reduction rate of the rotational speed command to be equal to or lower than the prescribed limit value when the rotational speed command is reduced in accordance with the operation of the rotational speed setting device 17.

[0054] Further, the above-described excavator has been described as an example of the application target of the present application, but the present application is not limited thereto and can be applied to other construction machines.

[0055] Explanation of Reference Signs

[0056] 9 boom cylinder

[0057] 10 stick cylinder

[0058] 11 bucket cylinder

[0059] 20 electric motor

[0060] 21 hydraulic pump

[0061] 28 hydraulic control check valve (lock device)

[0062] 30 controller

[0063] 31 inverter

[0064] 32 electric power storage device

Claims

1. A construction machine, comprising: an electric motor; a controller that outputs a rotational speed command; an inverter that controls a rotational speed of the electric motor based on the rotational speed command from the controller; and an electric storage device that outputs driving electric power to the inverter when the electric motor is accelerated and inputs regenerative electric power from the inverter when the electric motor is decelerated, the construction machine characterized in that the controller outputs the rotational speed command to the inverter in such a manner that a rate of decrease in the rotational speed of the electric motor becomes equal to or lower than a prescribed limit value when the electric motor is decelerated. comprising: a hydraulic pump that is driven by the electric motor; a hydraulic actuator that is driven by hydraulic oil ejected from the hydraulic pump; and a lock device that is switched between a locked state in which driving of the hydraulic actuator is prohibited and a locked release state in which driving of the hydraulic actuator is permitted, the controller outputs the rotational speed command in such a manner that the rate of decrease in the rotational speed of the electric motor is limited to be equal to or lower than the prescribed limit value and the rotational speed command is decreased in stages when the lock device is switched from the locked release state to the locked state.

3. The construction machine according to claim 2, characterized in that the controller outputs the rotational speed command in such a manner that the rate of decrease in the rotational speed of the electric motor is limited to be equal to or lower than the prescribed limit value and the rotational speed command is decreased in stages until the rotational speed of the electric motor becomes zero when the lock device is switched from the locked release state to the locked state. ​ ​ ​ ​ 2. A working machine according to claim 1, characterised in that ​ ​ ​ ​ ​ ​ ​

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