Work Machine

Abstract

To provide a work machine capable of reducing vibration while improving performance and working efficiency.SOLUTION: An air compressor 1 includes a motor 14, a compression section 13 for compressing and discharging air by driving force of the motor 14, air tanks 12a, 12b for storing the air discharged from the compression section 13, and a main control section 40 for setting a target rotation speed of the motor 14 and detecting an actual rotation speed of the motor 14 so as to control the driving of the motor 14. The main control section 40 stops the driving of the motor 14 when the actual rotation speed of the motor 14 is lowered to a prescribed rotation speed threshold, and restarts the motor 14 when a tank inner pressure becomes lower than a first restart pressure after stopping the driving of the motor 14. The main control section 40 sets the first restart pressure on the basis of the tank inner pressure when the actual rotation speed of the motor 14 is lowered to the rotation speed threshold.SELECTED DRAWING: Figure 5B

Description

[Technical field]

[0001] The present invention relates to a working machine such as an air compressor. [Background technology]

[0002] In a compressor, which is an example of a work machine, air discharged from a compression section by the driving force of a motor is stored in a tank section. A control section controls the driving of the motor, drives the motor when the pressure of the air stored in the tank section is equal to or lower than a predetermined stop threshold, and stops the driving of the motor when the pressure exceeds the stop threshold. As the air in the tank section is consumed, the pressure decreases, and when the pressure falls below the restart threshold, the control section resumes driving the motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-68158 A Summary of the Invention [Problem to be solved by the invention]

[0004] When the AC power source is a temporary power source, when a cord reel is used, when the AC power source is shared with other devices, etc., the supply voltage from the AC power source may drop. In such a low-voltage situation, as the load on the motor increases, the motor's rotation speed drops. When high-pressure air is compressed in a state where the rotation speed is reduced, the rotation fluctuation becomes large and vibration increases. One possible solution to this problem is to lower the stop pressure according to the drop in input voltage, but because there are individual differences in motors and compression parts, it is necessary to lower the stop pressure with a margin, which results in a decrease in performance and work efficiency.

[0005] In view of the above problems, an object of the present invention is to provide a work machine that reduces vibration while improving performance and work efficiency. [Means for solving the problem]

[0006] One aspect of the present invention is a work machine. A motor; a compression unit that compresses and discharges air by the driving force of the motor; A tank section for storing the air discharged from the compression section; a control unit that sets a target rotation speed of the motor, detects an actual rotation speed of the motor, and controls driving of the motor; The control unit is While the motor is running When the actual rotation speed of the motor falls to a predetermined rotation speed threshold, the driving of the motor is stopped, and thereafter, when the pressure in the tank falls below a first restart pressure, the motor is restarted; The first restart pressure is set based on a first stop pressure, which is the pressure when the actual rotation speed of the motor drops to the rotation speed threshold value. death, When the first stop pressure is a first pressure value, the first restart pressure is set to a second pressure value, and when the first stop pressure is a third pressure value lower than the first pressure value, the first restart pressure is set to a fourth pressure value lower than the second pressure value. do. One aspect of the present invention is a work machine. A motor; a compression unit that compresses and discharges air by the driving force of the motor; A tank section for storing the air discharged from the compression section; a control unit that sets a target rotation speed of the motor, detects an actual rotation speed of the motor, and controls driving of the motor; The control unit is When the actual rotation speed of the motor falls to a predetermined rotation speed threshold while the motor is being driven, the motor is stopped from being driven, and when the pressure in the tank thereafter falls below a first restart pressure that is set based on a first stop pressure, which is the pressure when the actual rotation speed of the motor falls to the rotation speed threshold, the motor is restarted; When the actual rotation speed of the motor exceeds a predetermined rotation speed threshold, the motor is stopped when the pressure exceeds a preset second stop pressure, and then the motor is restarted when the pressure falls below a second restart pressure that is higher than the first restart pressure.

[0007] Any combination of the above components and conversion of the present invention between methods, systems, etc. are also valid aspects of the present invention. Effect of the Invention

[0008] According to the present invention, it is possible to provide a work machine that reduces vibration while improving performance and work efficiency. [Brief description of the drawings]

[0009] [Figure 1]1 is a perspective view showing an overall configuration of an air compressor 1 according to a first embodiment of the present invention. [Diagram 2] The same front view. [Diagram 3] Cross-sectional view taken along line AA in Figure 2. [Figure 4] 4 is a perspective view showing a battery pack mounting portion 45 provided on a body cover 10 of the air compressor 1. FIG. [Figure 5A] FIG. 2 is an overall circuit block diagram of the air compressor 1. [Figure 5B] FIG. 2 is an enlarged circuit block diagram of a main circuit section 200 that is inherent to the air compressor 1, out of the overall circuit block diagram. [Figure 5C] FIG. 2 is an enlarged circuit block diagram of an auxiliary circuit section 300 that performs power assist using two battery packs 5-A and 5-B, and that includes an assist power supply section 50, out of the overall circuit block diagram. [Figure 5D] 3 is an enlarged circuit block diagram showing a portion of the auxiliary circuit section 300 including a charging section 70. FIG. [Figure 6] 1 is a time chart showing the change over time in the input voltage (effective value) from the commercial AC power supply 39, the input current from the commercial AC power supply 39, the rotation speed of the motor 14, and the pressure in the air tanks 12a and 12b when the input voltage (effective value) from the commercial AC power supply 39 is 100 V, when the first half is 80 V and the second half is 90 V, and when the first half is 65 V and the second half is 80 V. [Figure 7] 3 is a control flowchart of the air compressor 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In the following, the same or equivalent components, members, etc. shown in each drawing are given the same reference numerals, and duplicated explanations are omitted as appropriate. The embodiments are illustrative and do not limit the invention. All features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0011] (Embodiment 1) An air compressor 1, which is one embodiment of a work machine, will be described in detail below with reference to the drawings. The air compressor 1 operates on a commercial AC power source (AC power source 100V) and has a power cord 2 and a plug (not shown) for connecting to a commercial power outlet. The air compressor 1 is capable of assisted operation using a battery power source, and has multiple (two in the illustrated case) battery pack mounting parts 45 on the outer surface of the main body cover (housing) 10, as shown in FIG. 4.

[0012] A battery pack 5 as a battery unit can be detachably attached to each of the battery pack attachment sections 45. Although FIG. 4 shows a state in which a battery pack 5 is attached to one battery pack attachment section 45, a battery pack 5 can be attached to each battery pack attachment section 45, and a total of two battery packs 5 can be used for assist. The battery pack 5 has a storage case and a secondary battery (secondary battery cell) provided in the storage case. The battery pack attachment section 45 has connection terminals that connect to the terminals of the battery pack 5.

[0013] The air compressor 1 comprises a body cover 10, carrying handles 11 provided on both sides of the body cover 10, a pair of parallel-arranged air tanks 12a, 12b as a tank section for storing compressed air, a compression section 13 (FIG. 3) that compresses air drawn in from the outside and supplies it to the air tanks 12a, 12b, and a motor 14 (FIG. 3) connected to the compression section 13 and driving the compression section 13. The motor 14 is an example of a load section.

[0014] The compression unit 13 and the motor 14 are disposed above the pair of air tanks 12a, 12b such that the axial direction of the motor 14 is substantially perpendicular to the longitudinal direction of the air tanks 12a, 12b. The air tanks 12a, 12b are provided with legs 15 for protection and prevention of direct contact with the ground. The motor 14 is, for example, a DC brushless motor. The inverter unit 33 shown in Figs. 5A and 5B, which supplies power to the motor 14, is controlled (for example, by PWM control) by a main control unit 40 (including a control circuit such as a CPU) to control the rotation speed and the like of the motor 14.

[0015] A user can turn the power of the air compressor 1 on and off, start and stop the motor 14, switch between operation modes, and so on, using the operation panel unit (switch panel) 19. The operation panel unit 19 also displays warnings about the pressure in the air tank and overloads, etc.

[0016] The compression section 13 is composed of a first-stage low-pressure side compression section 17 and a second-stage high-pressure side compression section 18. The first-stage low-pressure side compression section 17 and the second-stage high-pressure side compression section 18 are disposed so as to face each other via the crankcase 16. The first-stage low-pressure side compression section 17 compresses external air (atmospheric pressure) sucked through the inside of the crankcase 16, and sends the compressed air to the second-stage high-pressure side compression section 18 through a first-stage discharge pipe. The second-stage high-pressure side compression section 18 compresses the compressed air supplied from the first-stage low-pressure side compression section 17 to a maximum allowable pressure of, for example, 3.0 to 4.5 MPa, and supplies the compressed air to the air tanks 12a, 12b, which are connected to each other, through a second-stage discharge pipe.

[0017] The compressed air in the air tanks 12a and 12b is decompressed by the pressure reducing valves 24a and 24b and taken out via the couplers 27a and 27b. The pressure near the couplers 27a and 27b can be monitored by the pressure gauges 26a and 26b. A pneumatic tool such as a nail driver is connected to each of the couplers 27a and 27b via a hose (not shown).

[0018] The pressure on the output side of the pressure reducing valves 24a, 24b (the pressure supplied to the air tool) can be adjusted by the pressure adjusting members 23a, 23b. The pressure reducing valves 24a, 24b can suppress the pressure on the coupler 27a, 27b side to a constant value below the maximum pressure, regardless of the magnitude of the pressure on the inlet side of the compressed air to the air tanks 12a, 12b. In other words, the couplers 27a, 27b obtain compressed air with a constant pressure regardless of the pressure inside the air tanks 12a, 12b. A drain discharge device is provided to discharge the drain and compressed air accumulated inside the air tanks 12a, 12b to the outside.

[0019] 5A, air compressor 1 has motor 14 for rotating compression unit 13 to send compressed air to air tanks 12a and 12b. Air compressor 1 includes a main circuit unit 200 for driving motor 14 using commercial AC power supply 39, which is an external AC power supply, and an auxiliary circuit unit 300 for power assist using two battery packs 5-A and 5-B.

[0020] As shown in Figures 5A and 5B, the main circuit section 200 is provided with a rectifier section 31, an AC side power supply boost circuit 32, an inverter section 33, and a main control section 40 for controlling the inverter section 33 in order to drive the motor 14 by receiving supply of a commercial AC power supply 39 (AC 100V: for example, a maximum rated current of a socket is 15A) which is an external AC power supply.

[0021] A noise filter 34 is inserted between the commercial AC power supply 39 and the rectifier 31. A smoothing capacitor 35 is connected to the rectified output side of the rectifier 31. AC power from the AC power supply 39 is rectified by the rectifier 31, and the DC power smoothed by the smoothing capacitor 35 is supplied to the AC-side power supply boost circuit 32. A current detection resistor 36 is inserted in the connection line between the rectifier 31 and the AC-side power supply boost circuit 32. The AC-side load current detection unit 37 detects (monitors) the AC load current based on the voltage drop across the current detection resistor 36, and outputs an AC load current detection signal to the main control unit 40. An input voltage detection unit 65 is provided between the output terminals of the rectifier 31. The input voltage detection unit 65 detects (monitors) the voltage between the output terminals of the rectifier 31, and transmits it to the main control unit 40.

[0022] The AC-side power supply boost circuit 32 includes a boost circuit such as a DC-DC converter, and the boosted DC power is supplied to the motor 14 via the inverter unit 33. The rectifier unit 31, the AC-side power supply boost circuit 32, and the smoothing capacitor 35 are an example of an AC-side power supply unit.

[0023] In the illustrated example, the AC-side power supply boost circuit 32 is a chopper-type DC-DC converter having a choke coil 321, a switching element 322, a diode 323, and a capacitor 324, and has a boost voltage control unit 325 that controls the switching operation of the switching element 322. A boost voltage detection unit 38 is provided on the boost output side of the AC-side power supply boost circuit 32.

[0024] The main control unit 40 receives a boost voltage monitoring signal from the boost voltage detection unit 38, a rotation detection signal from a rotation sensor 41 that detects the rotation of the motor 14, and a pressure detection signal from a pressure sensor 42 that detects the pressure in the air tanks 12a, 12b. The main control unit 40 outputs a boost voltage control signal to the AC side power supply boost circuit 32 (boosted voltage control unit 325) and outputs an inverter control signal to the inverter unit 33, and supplies the DC power boosted by the AC side power supply boost circuit 32 to the motor 14 via the inverter unit 33, thereby controlling the rotation of the motor 14 by, for example, PWM control. The compression unit 13 is rotationally driven by the motor 14, and air discharged from the compression unit 13 is sent to the air tanks 12a, 12b.

[0025] The operation panel unit 19 has a display panel 191 that displays the pressure in the air tanks 12a, 12b and warnings such as overload, an operation button 192 that switches the power on and off, a charge button 193 that instructs charging of the battery packs 5-A, 5-B, a mode change button 194 that instructs switching between operation modes, and an assist button 195 that instructs power assist using the battery packs 5-A, 5-B, and is provided with a switch panel control unit 190 to control these. The switch panel control unit 190 is connected to the main control unit 40 via a communication circuit 197.

[0026] A circuit power supply unit 90 is provided to supply a stabilized DC voltage to the main control unit 40, the operation panel unit 19, the communication circuit 197, etc. The circuit power supply unit 90 uses the DC output of the rectifier unit 31 to supply a power supply voltage Vcc(A) to the main control unit 40, etc., and a power supply voltage Vcc(C) to the switch panel control unit 190, the communication circuit 197, etc. The circuit power supply unit 90 has a step-down transformer 91 having one primary winding and two secondary windings, a switching element 92 that switches the transformer primary side, a circuit power supply drive circuit 93 that outputs a drive signal to the switching element 92, and rectifying and smoothing circuits 94 and 95 that are provided on the two secondary windings, respectively. The DC output voltage of the rectifying and smoothing circuit 94 is supplied to the main control unit 40, etc. as Vcc(A), and the DC output voltage of the rectifying and smoothing circuit 95 is supplied to the switch panel control unit 190, the communication circuit 197, etc. as Vcc(C).

[0027] As shown in Fig. 5A, Fig. 5C and Fig. 5D, the auxiliary circuit section 300 has an assist power supply section 50 for assisting the driving of the motor 14 with a battery power supply (DC power supply), a charging section 70 for charging the battery packs 5-A and 5-B as battery power supplies, a sub-controller 80, a circuit power supply section 110 and a communication circuit 100. The sub-controller 80 includes a control circuit such as a CPU and controls the operation of the assist power supply section 50 and the charging section 70 in cooperation with the main control section 40. The circuit power supply section 110 supplies a stabilized DC voltage to the sub-controller 80 and the communication circuit 100. The communication circuit 100 constitutes an electrically insulated communication line between the main control section 40 and the sub-controller 80. The auxiliary circuit section 300 is housed, for example, in the storage case section 20 in the main body cover 10 of Fig. 3.

[0028] A battery pack 5-A is connected to a connection terminal 45A of one battery pack mounting section 45, and a battery pack 5-B is connected to a connection terminal 45B of the other battery pack mounting section 45. Battery voltage detection sections 46A and 46B are provided to detect the battery pack voltages of the battery packs 5-A and 5-B connected to the connection terminals 45A and 45B, respectively. Battery voltage detection signals from the battery voltage detection sections 46A and 46B are supplied to the sub-control section 80. The sub-control section 80 receives battery information acquisition signals from the battery packs 5-A and 5-B and acquires the battery information (battery temperature, etc.) of the battery packs 5-A and 5-B, respectively. The battery packs 5-A and 5-B include control sections 44A and 44B, respectively, and can communicate with the sub-control section 80. The main control section 40, the sub-control section 80, and the control sections 44A and 44B of the battery packs 5-A and 5-B constitute the control section of the air compressor 1.

[0029] The assist power supply unit 50 includes a DC-DC boost converter as a boost circuit. The assist power supply unit 50 has switching elements (e.g., MOSFETs) 52 and 53 connected in a push-pull manner to the primary side of a boost transformer 51, an assist power supply drive circuit 54 that alternately switches the switching elements 52 and 53, a rectifier unit 55 connected to the secondary side of the boost transformer 51, a choke coil 63, a smoothing capacitor 56, and an assist current control unit 57.

[0030] A current detection resistor 58 is inserted in the connection line between the rectifier 55 and the inverter 33. The assist current control unit 57 detects (monitors) the assist current from the voltage drop across the current detection resistor 58, and feeds back the assist current detection signal to the assist power supply driving circuit 54 via a photocoupler 59 as a feedback circuit. The photocoupler 59 is used here to electrically insulate the main circuit unit 200 electrically connected to the AC power supply 39 from the auxiliary circuit unit 300 electrically connected to the battery packs 5-A and 5-B, and the photocoupler is used in the following description for the same reason. The step-up transformer 51 is an example of a step-up circuit. The connection terminal 45A to which the battery pack 5-A is connected, the battery voltage detection unit 46A, the charging unit 70, the connection terminal 45B to which the battery pack 5-B is connected, the battery voltage detection unit 46B, the charging unit 70, and the assist power supply unit 50 are an example of a battery-side power supply unit capable of adjusting the output voltage values ​​of the battery packs 5-A and 5-B.

[0031] The DC power of one or both of the battery packs 5-A, 5-B is supplied to the primary side of a step-up transformer 51 of the assist power supply unit 50. An assist voltage detection unit 60 for detecting the output voltage of the assist power supply unit 50 is provided on the output side of the rectification unit 55 of the assist power supply unit 50, and an assist voltage control unit 61 for controlling the output voltage of the assist power supply unit 50. The DC output power of the assist power supply unit 50 is supplied to the inverter unit 33 via a series diode 82 (combined with the DC output power of the AC side power supply step-up circuit 32).

[0032] The sub-controller 80 outputs an output current control signal to the assist current control unit 57 of the assist power supply unit 50 via the photocoupler 62 , and outputs an output voltage control signal for the assist power supply 50 to the assist voltage control unit 61 via the photocoupler 64 .

[0033] The output terminal of the assist power supply unit 50 is connected in parallel to the output terminal of the AC power supply boost circuit 32 via a series diode 82. In other words, the AC power supply boost circuit 32 and the assist power supply unit 50 are electrically connected in parallel to the motor 14.

[0034] Specifically, the assist power supply unit 50 receives an output current control signal and an output voltage control signal from the sub-control unit 80 to control the drive signal of the assist power supply drive circuit 54, and by changing the duty when alternately switching the switching elements 52, 53, it is possible to perform voltage variable control for increasing or decreasing the DC voltage across the output side smoothing capacitor 56. In other words, the assist power supply unit 50 can drive the motor 14 with PAM control for increasing or decreasing the voltage supplied to the inverter 33. Also, an assist power supply on / off signal is supplied from the sub-control unit 80 to the assist power supply drive circuit 54 of the assist power supply unit 50. When the assist power supply on / off signal instructs "assist power on", the assist power supply drive circuit 54 is operated to enable switching, and when it instructs "assist power off", the operation of the assist power supply drive circuit 54 is stopped.

[0035] The charging unit 70 is a circuit for charging the battery packs 5-A and 5-B mounted in the battery pack mounting section 45. The charging unit 70 includes a configuration of a step-down DC-DC converter. The charging unit 70 includes a rectifier 71 that receives the supply of the AC power source 39 via the noise filter 35, a smoothing capacitor 72, a step-down transformer 73, a switching element 74 that switches the primary side of the transformer, a charging power source drive circuit 75 that drives the switching element 74 on and off, a diode 76 and a smoothing capacitor 77 that serve as a rectifying and smoothing circuit that rectifies and smoothes the secondary side output of the transformer 73, a charging current control unit 78, and a charging voltage control unit 79. A current detection resistor 81 is inserted in the connection line between the rectifying and smoothing circuit on the secondary side of the transformer 73 and the battery packs 5-A and 5-B. The charging current control unit 78 detects (monitors) the charging current from the voltage drop across the current detection resistor 81. The charging current detection signal from the charging current control section 78 and the charging voltage control signal from the charging voltage control section 79 are fed back to the charging power supply driving circuit 75 via a photocoupler 82 serving as a feedback circuit.

[0036] The circuit power supply unit 110 uses the DC output of the rectifier 71 of the charging unit 70 to supply a power supply voltage Vcc(B) to the sub-controller 80 and the like, and also supplies power to a photocoupler 85 that transmits a charging power on / off signal. The circuit power supply unit 110 has a step-down transformer 111 having one primary winding and two secondary windings, a switching element 112 that switches the transformer primary side, a circuit power supply drive circuit 113 that outputs a drive signal to the switching element 112, and rectifying and smoothing circuits 114 and 115 that are provided on the two secondary windings, respectively. The DC output voltage of the rectifying and smoothing circuit 114 is supplied as Vcc(B) to the sub-controller 80, the photocoupler 82, and the like. The DC output voltage of the rectifying and smoothing circuit 115 is supplied to the photocoupler 85. The photocoupler 85 transmits the charging power on / off signal of the sub-controller 80 to the charging power supply drive circuit 75. When the charging power on / off signal indicates "charging power on", the charging power drive circuit 75 is operated to switch the switching element 74, and when the charging power on / off signal indicates "charging power off", the operation of the charging power drive circuit 75 is stopped.

[0037] A relay 87A (first cutoff circuit) is provided for turning on and off the connection between the connection terminal 45A of one battery pack mounting portion 45 and the charging portion 70, and a relay 87B (second cutoff circuit) is provided for turning on and off the connection between the connection terminal 45B of the other battery pack mounting portion 45 and the charging portion 70. A relay 87C is provided for turning on and off the connection between the connection terminal 45A and the assist power supply portion 50, and a relay 87D is provided for turning on and off the connection between the connection terminal 45B and the assist power supply portion 50. The relays 87A to 87D are each controlled to be turned on and off by a relay on / off signal from the sub-control portion 80.

[0038] The communication circuit 100 has two photocouplers 101 and 102, and constitutes an electrically insulated communication line between the main control unit 40 and the sub-control unit 80. The photocoupler 101 transmits information signals from the main control unit 40 to the sub-control unit 80, and the photocoupler 102 transmits information signals from the sub-control unit 80 to the main control unit 40.

[0039] The battery packs 5-A and 5-B are provided with thermistors Th1 and Th2, respectively, as temperature detectors for detecting the temperature of the internal secondary batteries. A thermistor Th3 for temperature detection is also provided in the switching elements 52 and 53 of the assist power supply unit 50. Temperature monitoring signals from thermistors Th1 to Th3 are output to the sub-controller 80, and the sub-controller 80 stops the operation of the battery packs 5 and the assist power supply unit 50 whose temperature rise exceeds the allowable range.

[0040] In the operation panel unit 19 of FIG. 5B, a display panel 191 is a display unit that displays various information from the main control unit 40. The operation button 192 is a switch that instructs the air compressor 1 to start or stop operation. The charge button 193 is a switch that instructs the air compressor 1 to permit or stop charging the battery packs 5-A, 5-B. The mode switching button 194 is a switch that switches between the operation modes of the air compressor 1, which will be described later. The assist button 195 is a switch that switches between a mode that uses power assist in combination with a battery pack (hereinafter referred to as the "assist combined mode") and a mode that does not use power assist (hereinafter referred to as the "non-assist mode").

[0041] 5A to 5D, the air compressor 1 is used while connected to a commercial AC power supply 39 (AC 100V). Since the main circuit section 200 receives power from the commercial AC power supply 39, the main control section 40 controls the input current from the commercial AC power supply 39 to be 15A or less based on the value of the AC side load current detection section 37. This is because the maximum rated current of an AC outlet is generally 15A.

[0042] During normal operation, the main control unit 40 lowers the target rotation speed of the motor 14 when the AC load current value is about to exceed 15 A. The target rotation speed also varies depending on the load on the inverter unit 33 and the pressure inside the air tanks 12a and 12b. Specifically, the target rotation speed is set high when the load is light, and low when the pressure inside the tank is increasing or the amount of compressed air used is large.

[0043] During power assist by operating the assist power supply unit 50, the AC current value drops when the target rotation speed is reached, so the main control unit 40 can supply the insufficient power from one or both of the battery packs 5-A and 5-B by increasing the target rotation speed so as to maintain the AC load current value of 15 A. At this time, the sub-control unit 80 can keep the rotation speed of the motor 14 within a certain range by applying a restriction on the supply current or power from the battery pack 5.

[0044] Here, please note the following points. The AC side power supply boost circuit 32 performs feedback control so that the boost voltage reaches a target value, but when the series diode 323A is not inserted, particularly when the assist voltage from the assist power supply unit 50 is too high, the boost voltage is controlled to be lowered. If the boost voltage drops, the current supply from the commercial AC power supply 39 drops, causing the current supply from the battery pack 5 to become excessive, resulting in a reduction in the power assist time. In this case, if the assist voltage (output voltage of the assist power supply unit 50) is controlled to be approximately the forward voltage drop (1V to 2V) of the series diode 82, the series diode 323A can be omitted.

[0045] On the other hand, when the series diode 323A is inserted, it is necessary to provide a voltage junction electrolytic capacitor 324A at the point where the boost voltage and the assist voltage are connected. This is to absorb the surge energy generated when the motor 14 is stopped, and a large-capacity, high-voltage-resistant capacitor is used. However, when the series diode 323A is omitted as described above, it can be substituted by the electrolytic capacitor 324 of the AC-side power supply boost circuit 32, so the voltage junction electrolytic capacitor can also be omitted. This not only reduces the area on the board and the cost of electronic components, but also improves efficiency reduction due to diode loss and voltage drop.

[0046] Generally, when multiple battery packs are connected in parallel, reverse current prevention diodes 47A and 47B, indicated by dotted lines in FIG. 5C, are required to prevent reverse current between the battery packs. However, by alternately charging the battery packs 5-A and 5-B so that the potential difference between the battery packs is within a predetermined potential difference value (e.g., 0.5 V), it is possible to practically suppress the reverse current between the battery packs to the charging current level. For this reason, the diodes 47A and 47B may be omitted. This can solve the problems of output reduction caused by the resistance of the diodes 47A and 47B and heat generation caused by the diodes 47A and 47B.

[0047] Even if the potential difference between battery packs 5-A and 5-B exceeds a predetermined potential difference value (0.5 V) during power assist with battery packs 5-A and 5-B connected in parallel, the assist continues until the voltage of one of the battery packs falls below a predetermined voltage value V1, which is the first threshold voltage.

[0048] If it is attempted to stop the assist of only one of the battery packs 5 during the power assist period, the discharge current of the other battery pack 5 will become excessive at the same time as the stop, so it is necessary to reduce the current value, for example by lowering the target rotation speed of the motor 14. To actually stop it, it is necessary to turn off the relay 87C or 87D while it is energized. From the viewpoint of preventing contact failure, it is preferable to stop the assist itself when the voltage of one of the battery packs falls below the predetermined voltage value V1. The reason for this is that if the assist is continued until the voltage of both battery packs falls below the predetermined voltage value V1, the current consumption of the battery pack 5 that dropped first will increase, accelerating the voltage drop and heat generation, and slowing down the recharge and re-assist cycle.

[0049] FIG. 6 is a time chart showing the time changes of the AC input voltage, the effective value of the input current from the commercial AC power source 39 (hereinafter also referred to as "AC input current"), the rotation speed of the motor 14 (hereinafter also referred to as "motor rotation speed"), and the pressure in the air tanks 12a and 12b (hereinafter also referred to as "tank pressure") in the cases where the effective value of the input voltage from the commercial AC power source 39 (hereinafter also referred to as "AC input voltage") is 100V, where the first half (before time t5) is 80V and the second half (after time t6) is 90V, and where the first half is 65V and the second half is 80V. This time chart is for the case where the non-assist mode is selected by the assist button 195. It is assumed that the air in the air tanks 12a and 12b (hereinafter "tank air") is not consumed except during the period from time t6 to t7. As described above, the tank pressure is detected by the pressure sensor 42, and the detection signal is input to the main control unit 40.

[0050] When the motor 14 is driven at time t0, that is, when the air compressor 1 starts to operate, the pressure inside the tank increases over time. As the pressure inside the tank increases, the load on the motor 14 also increases, and the AC input current increases in order to maintain the motor rotation speed at a constant target rotation speed. The rate at which the AC input current increases increases as the AC input voltage decreases. This is because the lower the AC input voltage, the more the AC input current needs to be increased to compensate for the power loss.

[0051] When the AC input voltage is 65V, the AC input current is 15A at time t1. When the AC input voltage is 80V, the AC input current is 15A at time t2. 15A is an example of a current threshold (upper limit) set so that a breaker or the like does not trip. After the AC input current reaches 15A, the motor speed is reduced as the pressure inside the tank increases so that the AC input current does not increase any more, that is, so that the input power from the commercial AC power source 39 (hereinafter also referred to as "AC input power") does not increase any more. In other words, around the time when the AC input current reaches 15A, the motor speed is shifted from constant speed control, which maintains the motor speed at a constant target speed, to low power control, which makes the target speed variable and keeps the AC input power constant.

[0052] When the AC input voltage is 65V, at time t3, the motor rotation speed drops to the rotation speed threshold value when the tank pressure is P4. The pressure P4 at this time is an example of the first stop pressure. When the AC input voltage is 80V, at time t4, the motor rotation speed drops to the rotation speed threshold value when the tank pressure is P2. The pressure P2 at this time is an example of the first stop pressure. The rotation speed threshold value is, for example, a rotation speed at which the rotation fluctuation becomes large and the vibration increases significantly if the motor rotation speed drops further, and is determined in advance. When the motor rotation speed drops to the rotation speed threshold value, the motor 14 stops even if the tank pressure has not reached a stop pressure (target pressure) P1 set in advance in order to prevent an increase in vibration (time t3 when the AC input voltage is 65V, time t4 when the AC input voltage is 80V).

[0053] When the AC input voltage is 100V, at time t5, the pressure in the tank reaches a stop pressure P1 as the second stop pressure, and the motor 14 stops. When the AC input voltage is any of 65V, 80V, and 100V, the pressure in the tank is constant after the motor 14 stops until consumption of the air in the tank starts at time t6. The stop pressure P1 as the second stop pressure is a preset value (static value), whereas the pressures P2 and P4 as the first stop pressures are pressures when the motor rotation speed drops to a rotation speed threshold value, and are values ​​that are dynamically determined according to the operating environment such as the AC input voltage.

[0054] 6, it is assumed that when the AC input voltage in the first half is 65 V, the usage state of commercial AC power supply 39 by other devices changes during the period from time t5 to t6, and the AC input voltage rises to 80 V. Similarly, it is assumed that when the AC input voltage in the first half is 80 V, the AC input voltage rises to 90 V during the period from time t5 to t6.

[0055] During the period from time t6 to t7, the air in the tank is consumed, and at time t7, the pressure in the tank drops by ΔA (the pressure in the tank drops to the restart pressure), and the motor 14 restarts. ΔA is determined in advance so that the motor 14 is not restarted or stopped too frequently, and so that the motor 14 is not stopped for too long or the tank pressure drops too much. Specifically, if ΔA is too small, the motor 14 restarts immediately after stopping, making the operation of the air compressor 1 feel jerky and impairing workability, and the motor 14 is more likely to break down because of the increased load when restarting the motor 14. On the other hand, if ΔA is too large, the motor 14 is stopped for a longer period of time and the restart time is delayed, so the compression section 13 does not send compressed air to the air tanks 12a and 12b for a longer period of time, resulting in poor work efficiency. In addition, the tank pressure also drops significantly, so it takes longer for the tank pressure to return to a high pressure close to the stop pressure, resulting in poor work efficiency. Pressures P3 and P5, which are lower than pressures P2 and P4 by ΔA, are examples of the first restart pressure. Pressure P2, which is lower than pressure P1 by ΔA, is an example of the second restart pressure. After the motor 14 is restarted at time t7, the tank pressure rises again over time.

[0056] When the AC input voltage is 100 V, at time t8, the pressure inside the tank reaches the stop pressure P1, and the motor 14 stops. When the AC input voltage in the latter half is 90 V, at time t9, the pressure inside the tank reaches the stop pressure P1, and the motor 14 stops. When the AC input voltage in the latter half is 80 V, at time t10, the motor rotation speed drops to the rotation speed threshold value, and the motor 14 stops.

[0057] FIG. 7 is a control flowchart of the air compressor 1. This flowchart is for the case where the assist combined mode is selected by the assist button 195. In the case of mode 1 (yes in S1), the main control unit 40 sets the stop pressure to Poff1 and the restart pressure to Pon1 (S2). In the case of mode 2 (no in S1, yes in S3), the main control unit 40 sets the stop pressure to Poff2 and the restart pressure to Pon2 (S4). In the case of mode 3 (no in S1, no in S3), the main control unit 40 sets the stop pressure to Poff3 and the restart pressure to Pon3 (S5). Modes 1 to 3 are operation modes that are set in advance by the mode switching button 194. Any of the stop pressures Poff1 to Poff3 corresponds to the tank pressure P1 in FIG. 6.

[0058] If the power is turned off by the operation button 192 (no in S6), the main control unit 40 stops the motor 14 (S7) and returns to S1. If the power is turned on by the operation button 192 (yes in S6), the main control unit 40 starts the motor 14 (S8). The main control unit 40 monitors the motor rotation speed (actual rotation speed) using a rotation detection signal from the rotation sensor 41, and if the motor rotation speed is equal to or lower than the rotation speed threshold value (yes in S9), checks the AC input voltage using a signal from the input voltage detection unit 65 (S10).

[0059] If the AC input voltage is not greater than the threshold voltage Va (no in S10), the main control unit 40 determines that the power supply is in a bad state, stops the motor 14, and displays an error on the display panel 191 (S11). If the AC input voltage is greater than the threshold voltage Va (yes in S10), the main control unit 40 checks, through communication with the sub-control unit 80, whether or not power assistance using the battery packs 5-A, 5-B (hereinafter also referred to as "assisted operation") is being performed (S12).

[0060] If the main control unit 40 is not performing assisted operation (no in S12), it communicates with the sub-control unit 80 to check whether assisted operation is possible (S13). If assisted operation is possible (yes in S13), the main control unit 40 instructs the sub-control unit 80 to start assisted operation, activates assisted operation (S14), and returns to S9.

[0061] If assisted operation is being performed in S12 (yes in S12), or if assisted operation is not possible in S13 (no in S13), the main control unit 40 obtains the current tank pressure Pv (S15) and sets the stop pressure to Pv and the restart pressure to Pv-ΔA (S16).

[0062] If the tank internal pressure is equal to or higher than the stop pressure (yes in S17), the main control unit 40 stops the motor 14 (S18). In the case of a process flow from no in S9 to S17, the stop pressure determined in S17 is the stop pressure set in any one of S2, S4, and S5. In the case of a process flow from S16 to S17, the stop pressure determined in S17 is the stop pressure set in S16 (the current tank internal pressure Pv), and the determination in S17 is yes.

[0063] The main control unit 40 continues stopping the motor 14 (S18) until the pressure inside the tank falls below the restart pressure (no in S19), and when the pressure inside the tank falls below the restart pressure (yes in S19), returns to S1 and sets the stop pressure and restart pressure according to the operating mode (modes 1 to 3) and restarts the motor 14 (S1 to S6, S8).

[0064] According to this embodiment, the following effects can be obtained.

[0065] (1) The main control unit 40 stops driving the motor 14 when the motor rotation speed drops to the rotation speed threshold. This makes it possible to suppress the increase in vibration and noise caused by driving the motor 14 at a rotation speed lower than the rotation speed threshold. For comparison, consider a case where the stop pressure is reduced in response to a drop in the AC input voltage, regardless of the motor rotation speed. In this case, the amount of reduction in the stop pressure is increased with a margin in order to accommodate the load on the motor 14, which varies depending on the individual differences of the air compressor 1. In this case, when the AC input voltage drops, it is difficult to operate the air compressor 1 until just before the vibration and noise become significantly large. Specifically, if the amount of reduction in the stop pressure is reduced (the stop pressure after the reduction is increased) for an individual that is unlikely to generate vibration and noise, the vibration and noise will increase in an individual that is likely to generate vibration and noise, even if the tank pressure is below the stop pressure. Conversely, if the reduction in the stop pressure is increased (the stop pressure after reduction is reduced) for an individual that is prone to vibration and noise, in an individual that is not prone to vibration and noise, the tank pressure will exceed the stop pressure and the motor will stop even if the tank pressure is sufficiently lower than the value at which vibration and noise become significantly large, so the achievable tank pressure will be lower than the pressure that can be achieved without significantly increasing vibration and noise.In this regard, according to the present embodiment, whether or not to stop motor 14 is determined depending on whether the rotation speed is equal to or lower than the rotation speed threshold, so that air compressor 1 can be operated until just before vibration and noise become significantly large when the AC input voltage decreases.

[0066] (2) After the motor rotation speed drops to the rotation speed threshold and the driving of the motor 14 is stopped, the main control unit 40 sets the restart pressure based on the tank pressure when the motor rotation speed drops to the rotation speed threshold, and restarts the motor 14 when the tank pressure drops to the restart pressure. Therefore, compared to a case where a fixed restart pressure is used regardless of the tank pressure when the motor rotation speed drops to the rotation speed threshold, the restart pressure can be appropriately set so that the frequency of restarting and stopping the motor 14 is not too high, and so that the motor 14 is not stopped for too long or the tank pressure does not drop too much, compared to a case where a fixed restart pressure is used. In a specific example where a fixed restart pressure is used, it is considered that the restart pressure is set low in accordance with an individual that is prone to vibration and noise (because if the restart pressure is set high in accordance with an individual that is not prone to vibration and noise, the vibration and noise will become significantly larger in the individual that is prone to vibration and noise). In this assumption, in an individual that is unlikely to generate vibration or noise, the restart pressure is set lower than the appropriate value for that individual, so the motor 14 is stopped for a longer period of time, the restart time is delayed, and the compression section 13 does not send compressed air to the air tanks 12a, 12b for a longer period of time, resulting in poor work efficiency. In addition, the tank pressure also drops significantly, so it takes a longer time for the tank pressure to return to a high pressure close to the stop pressure, resulting in poor work efficiency. In this regard, according to the present embodiment, not only the stop pressure is arbitrarily determined in accordance with the individual differences of the motor 14, but the restart pressure is also arbitrarily determined in accordance with the individual differences of the motor 14, so the restart pressure can be set to an appropriate value, resulting in good work efficiency.

[0067] Although the present invention has been described above using the embodiment as an example, it will be understood by those skilled in the art that various modifications are possible to the components and processes of the embodiment within the scope of the claims. Modifications will be mentioned below.

[0068] The difference between the tank pressure (stop pressure) when the motor 14 is stopped and the tank pressure (restart pressure) when the motor 14 is subsequently restarted does not have to be a fixed value. For example, the tank pressure that is a predetermined percentage lower than the stop pressure may be set as the restart pressure. The difference between the stop pressure and the restart pressure when the motor rotation speed falls below the threshold rotation speed may be different from the difference between the stop pressure and the restart pressure when the motor rotation speed does not fall below the threshold rotation speed. [Explanation of symbols]

[0069] 1...air compressor, 5,5-A,5-B...battery pack, 10...main body cover, 12a,12b...air tank, 13...compression section, 14...motor, 19...operation panel section, 20...storage case section, 31...rectification section, 32...AC side power supply boost circuit, 33...inverter section, 37...AC side load current detection section, 38...boosted voltage detection section, 40...main control section, 45...battery pack mounting section, 46A,46B...battery voltage detection section, 50...assist power supply section, 57...assist current control section, 60...assist voltage detection section, 65...input voltage detection section, 70...charging section, 80...sub-control section, 87A-87D...relay, 90,110...circuit power supply section, 100...communication circuit, 200...main body circuit section, 300...auxiliary circuit section.

Claims

1. A motor; a compression unit that compresses and discharges air by the driving force of the motor; A tank section for storing the air discharged from the compression section; a control unit that sets a target rotation speed of the motor, detects an actual rotation speed of the motor, and controls driving of the motor; The control unit is When the actual rotation speed of the motor falls to a predetermined rotation speed threshold while the motor is being driven, the motor is stopped from being driven, and thereafter, when the pressure in the tank falls below a first restart pressure, the motor is restarted; The first restart pressure is set based on a first stop pressure, which is the pressure when the actual rotation speed of the motor is reduced to the rotation speed threshold value; A work machine wherein, when the first stop pressure is a first pressure value, the first restart pressure is set to a second pressure value, and, when the first stop pressure is a third pressure value lower than the first pressure value, the first restart pressure is set to a fourth pressure value lower than the second pressure value.

2. 2. The work machine according to claim 1, wherein the control unit sets the second pressure value to a value that is a predetermined amount smaller than the first pressure value, and sets the fourth pressure value to a value that is the predetermined amount smaller than the third pressure value.

3. The work machine according to claim 1 or 2, wherein the control unit controls driving of the motor so that a current supplied from an external power supply does not exceed a predetermined current threshold.

4. The control unit is When the actual rotation speed of the motor exceeds a predetermined rotation speed threshold, stopping the motor when the pressure exceeds a second stop pressure set in advance; The work machine according to claim 1 , further comprising: a motor restarting mechanism configured to restart the motor when the pressure falls below a second restart pressure after the drive of the motor is stopped.

5. A motor, a compression unit that compresses and discharges air by the driving force of the motor; A tank section for storing the air discharged from the compression section; a control unit that sets a target rotation speed of the motor, detects an actual rotation speed of the motor, and controls driving of the motor; The control unit is When the actual rotation speed of the motor falls to a predetermined rotation speed threshold while the motor is being driven, the motor is stopped from being driven, and when the pressure in the tank thereafter falls below a first restart pressure that is set based on a first stop pressure, which is the pressure when the actual rotation speed of the motor falls to the rotation speed threshold, the motor is restarted; A work machine in which, when the actual rotation speed of the motor exceeds a predetermined rotation speed threshold, the motor is stopped when the pressure exceeds a preset second stop pressure, and the motor is then restarted when the pressure falls below a second restart pressure that is higher than the first restart pressure.

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