JP7616406B2 - Work equipment - Google Patents

Description

The present invention relates to a work machine such as an air compressor.

The work machine described in Patent Document 1 below operates on power supplied from an external AC power source such as a commercial power source. Due to limitations in the breaker capacity, there is an upper limit to the input power value from the AC power source.

JP 2018-155100 A

In the configuration of Patent Document 1, when the driving power of the motor increases and the input power from the AC power source approaches the upper limit, the driving power cannot be increased any further, leaving room for improvement in terms of workability. For this reason, it is assumed that assist control is performed to combine the power of the battery with the power of the AC power source, but because the optimal assist control differs depending on the remaining capacity of the battery, it is necessary to switch to an appropriate assist control.

In consideration of the above problems, the present invention aims to provide a work machine with improved workability.

One aspect of the present invention is a work machine.
A load section ;
a first power supply unit connected to the battery unit and configured to output power of the battery unit to the load unit ;
a second power supply unit electrically connected in parallel with the first power supply unit with respect to the load unit and connected to an external AC power supply, the second power supply unit outputting power of the AC power supply to the load unit ;
a control unit that performs assist control to control the first power supply unit and the second power supply unit so that electric powers output from the first power supply unit and the second power supply unit are combined and supplied to the load unit ,
The control unit limits the power output from the first power supply unit when the remaining capacity of the battery unit satisfies a power limiting condition .
Another aspect of the present invention is a work machine.
A load section;
a first power supply unit connected to the battery unit and configured to output power of the battery unit to the load unit;
a second power supply unit electrically connected in parallel with the first power supply unit with respect to the load unit and connected to an external AC power supply, the second power supply unit outputting power of the AC power supply to the load unit;
a control unit that performs assist control to control the first power supply unit and the second power supply unit so that electric powers output from the first power supply unit and the second power supply unit are combined and supplied to the load unit,
the battery unit includes a plurality of battery packs,
The control unit is
selecting one battery pack from the plurality of battery packs and causing the first power supply unit to supply power thereto;
When the remaining capacity of the selected battery pack falls to a switching remaining capacity that is greater than an assist stop remaining capacity at which the assist control is stopped, the battery pack that is caused to supply power to the first power supply unit is switched.
Another aspect of the present invention is a work machine.
A motor;
a first power supply unit connected to the battery unit and configured to output electric power from the battery unit to the motor;
a second power supply unit electrically connected in parallel with the first power supply unit with respect to the motor and connected to an external AC power supply, the second power supply unit outputting electric power from the AC power supply to the motor;
a control unit that performs assist control to control the first power supply unit and the second power supply unit so that electric powers output from the first power supply unit and the second power supply unit are combined and supplied to the motor,
The control unit limits the power output from the first power supply unit when the remaining capacity of the battery unit satisfies a power limiting condition.
Another aspect of the present invention is a work machine.
A motor;
a first power supply unit connected to the battery unit and configured to output electric power from the battery unit to the motor;
a second power supply unit electrically connected in parallel with the first power supply unit with respect to the motor and connected to an external AC power supply, the second power supply unit outputting electric power from the AC power supply to the motor;
a control unit that performs assist control to control the first power supply unit and the second power supply unit so that electric powers output from the first power supply unit and the second power supply unit are combined and supplied to the motor,
the battery unit includes a plurality of battery packs,
The control unit is
selecting one battery pack from the plurality of battery packs and causing the first power supply unit to supply power thereto;
When the remaining capacity of the selected battery pack falls to a switching remaining capacity that is larger than an assist stop remaining capacity at which the assist control is stopped, the battery pack that is caused to supply power to the first power supply unit is switched.

In addition, any combination of the above components, and conversions of the expressions of the present invention between methods, systems, etc., are also valid aspects of the present invention.

The present invention makes it possible to provide a work machine with improved workability.

1 is a perspective view showing an overall configuration of an air compressor 1 according to an embodiment of the present invention. The same front view. 3 is a cross-sectional plan view taken along the line AA in FIG. 2 . 4 is a perspective view showing a battery pack mounting portion 45 provided on the body cover 10 of the air compressor 1. FIG. FIG. 2 is an overall circuit block diagram of the air compressor 1. 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. FIG. 2 is an enlarged circuit block diagram of an auxiliary circuit section 300 that performs power assist using two battery packs 5A, 5B, and that includes an assist power supply section 50, out of the overall circuit block diagram. 3 is an enlarged circuit block diagram showing a portion of the auxiliary circuit section 300 including a charging section 70. FIG. 1A is a time chart showing an example of changes over time in the assist output voltage, the assist output current (assist output power), and the battery voltage in a current limiting variable mode in a first control example of the air compressor 1. FIG. 1B is a time chart showing an example of changes over time in the assist output voltage, the assist output current (assist output power), and the battery voltage in an operation of a comparative example. 6A is a time chart showing an example of changes over time in the assist output voltage, the assist output current (assist output power), and the battery voltage in a high current mode in the first control example of the air compressor 1. FIG. 6B is a time chart showing the operation of the same comparative example as FIG. 6A is a time chart showing an example of time changes in the assist output voltage, the assist output current (assist output power), and the battery voltage in a low current mode in the first control example of the air compressor 1. FIG. 6B is a time chart showing the operation of the same comparative example as FIG. 1A is a control flowchart of the current limiting variable mode of the air compressor 1. FIG. 1B is a control flowchart of the high current mode and the low current mode of the air compressor 1. 13 is a time chart showing a first example of changes in tank pressure and battery voltage over time in the second control example of the air compressor 1; 13 is a time chart showing a second example of changes in the tank pressure and the battery voltage over time in the second control example of the air compressor 1; 13 is a time chart showing a third example of changes in the tank pressure and the battery voltage over time in the second control example of the air compressor 1; 13 is a time chart showing a fourth example of changes in the tank pressure and the battery voltage over time in the second control example of the air compressor 1; 13A is a flowchart of assist control when the tank pressure increases, in the second control example of the air compressor 1. FIG. 13B is a flowchart of assist control when the tank pressure decreases, in the second control example of the air compressor 1. 5 is a graph showing an example of a waveform of an assist output current at a light load, a medium load, and a high load. 13 is a time chart showing an example of changes in assist output power and battery voltage over time in the third control example of the air compressor 1; 13 is a flowchart of assist control of the air compressor 1 in a third control example.

In the following, identical or equivalent components, parts, etc. shown in each drawing are given the same symbols, and duplicate 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.

This embodiment relates to an air compressor 1. The air compressor 1 is an example of a work machine (electrical equipment). The air compressor 1 operates on a commercial alternating current 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 as shown in Figure 4, has multiple (two in the illustrated case) battery pack mounting portions 45 on the outer surface of the main body cover (housing) 10.

A battery pack 5 can be detachably attached to each of the battery pack attachment sections 45 as a battery section. Although FIG. 4 shows a battery pack 5 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. In FIGS. 5A, 5C, and 5D, the two battery packs 5 are distinguished from each other as battery packs 5A and 5B. The rated voltage of battery packs 5A and 5B is not particularly limited, but is assumed to be 36V here. The battery pack 5 has a housing case and a secondary battery (secondary battery cell) provided in the housing case. The battery pack attachment section 45 has connection terminals that connect to the terminals of the battery pack 5.

Air compressor 1 comprises a main body cover 10, carrying handles 11 provided on both sides of main body cover 10, a pair of parallel-arranged air tanks 12a, 12b for storing compressed air, a compression section 13 (Fig. 3) that compresses air (gas) sucked in from the outside and supplies it to the air tanks 12a, 12b as tank sections, and a motor 14 (same) connected to compression section 13 and driving compression section 13. Motor 14 is an example of a load section.

The compression section 13 and the motor 14 are disposed above the pair of air tanks 12a, 12b so that the axial direction of the motor 14 is approximately perpendicular to the longitudinal direction of the air tanks 12a, 12b. The air tanks 12a, 12b are provided with legs 15 to prevent and protect them from direct contact with the ground. The motor 14 is, for example, a DC brushless motor. The inverter section 33 in Figures 5A and 5B, which supplies power to the motor 14, is controlled (for example, PWM control) by the main control section 40 (including a control circuit such as a CPU) to control the rotation speed of the motor 14, etc.

The user can use the operation panel (switch panel) 19 to turn the power of the air compressor 1 on and off (ON/OFF), start and stop the motor 14, switch operation modes, etc. The operation panel 19 displays the pressure of the air tanks 12a, 12b (also referred to as "tank pressure") and warnings such as overload.

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 arranged to face each other via the crankcase 16. The first-stage low-pressure side compression section 17 compresses external air (atmospheric pressure) sucked in through the inside of the crankcase 16, and sends the compressed air to the second-stage high-pressure side compression section 18 via the 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 it to the air tanks 12a, 12b, which are connected to each other, via the second-stage discharge pipe.

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

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

As shown in Figure 5A, the air compressor 1 has a motor 14 for rotating and driving the compression section 13 to send compressed air to the air tanks 12a and 12b. The air compressor 1 includes a main circuit section 200 for driving the motor 14 using a commercial AC power source 39, which is an external AC power source, and an auxiliary circuit section 300 for power assist using two battery packs 5A and 5B.

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 as a second power supply section, 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.

A noise filter 34 is inserted between the commercial AC power supply 39 and the rectifier unit 31. A smoothing capacitor 35 is connected to the rectified output side of the rectifier unit 31. The AC power from the AC power supply 39 is rectified by the rectifier unit 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 unit 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.

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 examples of an AC side power supply unit.

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.

The main control unit 40 receives as input 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 inside the tank. 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, for example by PWM control. The compression unit 13 is driven to rotate by the motor 14, and air discharged from the compression unit 13 is sent to the air tanks 12a, 12b.

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

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 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).

As shown in Figures 5A, 5C and 5D, the auxiliary circuit unit 300 has an assist power supply unit 50 as a first power supply unit for assisting the driving of the motor 14 with a battery power supply (DC power supply), a charging unit 70 for charging the battery packs 5A and 5B as battery power supplies, a sub-controller 80, a circuit power supply unit 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 unit 50 and the charging unit 70 in cooperation with the main control unit 40. The circuit power supply unit 110 supplies a stabilized DC voltage to the sub-controller 80, the communication circuit 100, etc. The communication circuit 100 constitutes an electrically insulated communication line between the main control unit 40 and the sub-controller 80. The auxiliary circuit unit 300 is stored, for example, in the storage case unit 20 in the main body cover 10 of Figure 3.

A battery pack 5A is connected to the connection terminal 45A of one battery pack mounting section 45, and a battery pack 5B is connected to the connection terminal 45B of the other battery pack mounting section 45. Battery voltage detection units 46A and 46B are provided to detect the battery pack voltages of the battery packs 5A and 5B connected to the connection terminals 45A and 45B, respectively. Battery voltage detection signals from the battery voltage detection units 46A and 46B are supplied to the sub-control unit 80. The sub-control unit 80 receives battery information acquisition signals from the battery packs 5A and 5B and acquires their battery information (battery temperature, etc.). The battery packs 5A and 5B each include a control unit 44A or 44B and can communicate with the sub-control unit 80. The main control unit 40, the sub-control unit 80, and the control units 44A and 44B of the battery packs 5A and 5B constitute the control unit of the air compressor 1. The control unit performs assist control to control the amount of boost of the assist power supply unit 50 and the AC side power supply boost circuit 32 so that the power output from each of the assist power supply unit 50 and the AC side power supply boost circuit 32 is combined and supplied to the motor 14.

The assist power supply unit 50 includes a DC-DC converter for boosting 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 the 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. By providing a smoothing choke coil 63 on the output side of the rectifier unit 55 and forming a choke input type smoothing circuit with the choke coil 63 and the smoothing capacitor 56, it is possible to reduce pulsation in the output voltage of the assist power supply unit 50 even when the duty (hereinafter "duty") of the PWM control of the switching elements 52 and 53 is small. As a result, when a high assist output voltage is set, a voltage is applied to the smoothing capacitor 56 via the choke coil 63, which is advantageous in terms of the withstand voltage of the smoothing capacitor 56 (the withstand voltage can be lower than when there is no choke coil).

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 output current (also referred to as "assist output current") of the assist power supply unit 50 from the voltage drop across the current detection resistor 58, and feeds back the assist current detection signal to the assist power supply drive 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 5A and 5B, and the photocoupler is used in the following explanation 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 5A is connected, the battery voltage detection unit 46A, the charging unit 70, the connection terminal 45B to which the battery pack 5B is connected, the battery voltage detection unit 46B, the charging unit 70 and the assist power supply unit 50 are examples of a battery side power supply unit capable of adjusting the output voltage values of the battery pack 5A and the battery pack 5B.

The DC power of one or both of the battery packs 5A, 5B is supplied to the primary side of the step-up transformer 51 of the assist power supply unit 50. An assist voltage detection unit 60 is provided on the output side of the rectification unit 55 of the assist power supply unit 50 to detect the output voltage of the assist power supply unit 50 (also referred to as the "assist output voltage"), and an assist voltage control unit 61 is provided to control the assist output voltage. 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).

The sub-control unit 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 of the assist power supply 50 to the assist voltage control unit 61 via the photocoupler 64.

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.

Specifically, the assist power supply unit 50 receives an output current control signal and an output voltage control signal from the sub-controller 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, voltage variable control can be performed to increase or decrease 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 that increases or decreases the voltage supplied to the inverter 33. In addition, an assist power on/off signal is supplied from the sub-controller 80 to the assist power supply drive circuit 54 of the assist power supply unit 50. When the assist power on/off signal indicates "assist power on", the assist power supply drive circuit 54 is operated to enable switching, and when it indicates "assist power off", the operation of the assist power supply drive circuit 54 is stopped.

The charging unit 70 is a circuit for charging the battery packs 5A and 5B 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 has a rectifier 71 that receives the supply of AC power supply 39 through a 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 supply drive circuit 75 that drives the switching element 74 on and off, a diode 76 and a smoothing capacitor 77 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 5A and 5B. 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 unit 78 and the charging voltage control signal from the charging voltage control unit 79 are fed back to the charging power supply driving circuit 75 via a photocoupler 82 serving as a feedback circuit.

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 the photocoupler 85 that transmits the 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 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.

A relay 87A (first cutoff circuit) is provided to turn on/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 to turn on/off the connection between the connection terminal 45B of the other battery pack mounting portion 45 and the charging portion 70. In addition, a relay 87C is provided to turn on/off the connection between the connection terminal 45A and the assist power supply portion 50, and a relay 87D is provided to turn on/off the connection between the connection terminal 45B and the assist power supply portion 50. Relays 87A to 87D are each controlled to be turned on/off by a relay on/off signal from the sub-control portion 80.

The communication circuit 100 has two photocouplers 101 and 102, and forms 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.

Battery packs 5A and 5B are each provided with thermistors Th1 and Th2 as temperature detection units that detect the temperature of the internal secondary batteries. In addition, switching elements 52 and 53 of the assist power supply unit 50 are also provided with a thermistor Th3 for temperature detection. Temperature monitoring signals from thermistors Th1 to Th3 are output to the sub-controller 80, and the sub-controller 80 stops operation of the battery pack 5 or the assist power supply unit 50 whose temperature rise exceeds the allowable range.

In the operation panel unit 19 in Figure 5B, the 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 and stop operation. The charge button 193 is a switch that instructs the battery packs 5A, 5B to be allowed to charge or to stop charging. 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 with a battery pack and a mode that does not use power assist.

In the circuit configurations of Figures 5A to 5D, the air compressor 1 is used while connected to a commercial AC power source 39 (AC 100V). The main circuit section 200 receives power from the commercial AC power source 39, and is controlled by the main control section 40 based on the value of the AC side load current detection section 37 so that the input current from the commercial AC power source 39 is 15A or less. This is because the maximum rated current of an AC outlet is generally 15A.

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, it is set high when the load is light and low when the pressure inside the tank is increasing or a large amount of compressed air is being used.

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 5A and 5B by increasing the target rotation speed to maintain the AC load current value of 15A. At this time, the sub-control unit 80 can keep the rotation speed of the motor 14 within a certain range by applying restrictions on the supply current or power from the battery pack 5.

Note the following points here. 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, and especially when the assist voltage from the assist power supply unit 50 is too high, the boost voltage is controlled to be lowered. When 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, which ultimately leads to a reduction in the power assist time. In this case, the series diode 323A can be omitted if the assist output voltage (output voltage of the assist power supply unit 50) is controlled to be approximately the forward voltage drop of the series diode 82 (1V to 2V) higher.

On the other hand, when inserting the series diode 323A, 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 that occurs when the motor 14 is stopped, and a large product with high capacity and high voltage resistance 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.

Generally, when multiple battery packs are connected in parallel, reverse current prevention diodes 47A and 47B, shown by dotted lines in Figure 5C, are required to prevent reverse current between the battery packs. However, by alternately charging the battery packs 5A and 5B so that the potential difference between them is within a specified 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, diodes 47A and 47B may be omitted. This can eliminate the problems of output reduction caused by the resistance of diodes 47A and 47B and heat generation caused by diodes 47A and 47B.

Even if the potential difference between battery packs 5A and 5B exceeds a predetermined potential difference value (0.5 V) during power assist with battery packs 5A and 5B connected in parallel, assistance will continue until the voltage of one of the battery packs falls below the assist stop voltage V1.

If an attempt is made 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 relay 87C or 87D while current is flowing. From the perspective of preventing contact failure, it is advisable to stop the assist itself when the voltage of one of the battery packs falls below the assist stop voltage V1. The reason for this is that if an attempt is made to continue the assist until the voltage of both battery packs falls below the assist stop voltage 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.

The control unit of the air compressor 1 changes the content of the assist control depending on the remaining capacity of the battery packs 5A and 5B. This point is described in detail below.

(First control example) Figure 6 (A) is a time chart showing an example of the change over time of the assist output voltage, assist output current (assist output power), and battery voltage in the current limit variable mode of the air compressor 1. Here, the explanation is given assuming that assistance is performed by battery pack 5A alone, but similar control is also performed when assistance is performed by battery pack 5B alone, and when assistance is performed by both battery packs 5A and 5B.

In the current limit variable mode, the sub-controller 80 limits the power output from the assist power supply unit 50 when the remaining capacity of the battery pack 5A satisfies the power limit condition. More specifically, when the remaining capacity of the battery pack 5A decreases, the sub-controller 80 lowers the upper limit value of the assist output current. The remaining capacity of the battery pack 5A is detected by the output voltage (battery voltage) of the battery pack 5A. When the battery voltage is greater than the current limit voltage Va (33V), the sub-controller 80 allows the assist output current to be equal to or greater than the limit current. The limit current is any current between Ia (first assist current) and Ib (second assist current) shown in FIG. 6(A). When the battery voltage gradually decreases from a fully charged state and becomes smaller than the current limit voltage Va, the sub-controller 80 prohibits the assist output current from being equal to or greater than the limit current. In other words, the aforementioned power limit condition is that the remaining capacity of the battery pack 5A decreases to the current limit voltage Va.

In FIG. 6(A), the sub-control unit 80 starts assist control at time t0. In assist control, the target value of the assist output voltage is set to 370V. At time t0, the battery voltage is 39V, and the sub-control unit 80 sets the target value of the assist output current to Ia and the target value of the assist output power to Pa (first assist power). Until time t1, the assist output voltage is maintained at 370V, the assist output current to Ia, and the assist output power to Pa. After time t1, due to the drop in battery voltage, even if the assist power supply unit 50 is operated at maximum capacity, the assist output voltage, assist output current, and assist output power will drop from their target values as the battery voltage drops.

When the battery voltage drops to the current limit voltage Va at time t2, the sub-controller 80 temporarily stops the assist control and lowers the target value of the assist output current to Ib and the target value of the assist output power to Pb (second assist power). At time t2, the battery voltage recovers to 37V due to the stop of the assist output current. At the following time t3, the sub-controller 80 resumes the assist control with the target value of the assist output voltage set to 370V, the target value of the assist output current set to Ib, and the target value of the assist output power set to Pb. Note that since the voltage drop amount is reduced by limiting the output current, the battery voltage at t3 has recovered to above the current limit voltage Va, but the sub-controller 80 does not return the target value of the assist output current to Ia. In other words, once the target value of the assist current is set to Ib, the sub-controller 80 ignores the recovery of the battery voltage.

After assist control is resumed, the assist output voltage is maintained at 370 V, the assist output current is maintained at Ib, and the assist output power is maintained at Pb until time t4. After time t4, due to the drop in battery voltage, even if the assist power supply unit 50 is operated at maximum capacity, the assist output voltage, assist output current, and assist output power drop from the target values along with the drop in battery voltage. When the battery voltage drops to the assist stop voltage Vb (30 V) at time t5, the sub-control unit 80 stops assist control.

The first half of the assist control, in which the target value of the assist output current is Ia and the target value of the assist output power is Pa, can continue for about 2 minutes, for example. The second half of the assist control, in which the target value of the assist output current is Ib and the target value of the assist output power is Pb, can continue for about 5 minutes, for example.

Figure 6(B) is a time chart showing an example of the time changes of the assist output voltage, assist output current (assist output power), and battery voltage in the operation of the comparative example. In this comparative example, the sub-controller 80 sets the target value of the assist output voltage to 370V, the target value of the assist output current to Ia, and the target value of the assist output power to Pa, and does not change the target values of the assist output current and assist output power to Ia and Pa until the battery voltage drops to the assist stop voltage Vb (30V) at time t7 and assist control is stopped.

In this comparative example, the assist output voltage decreases after time t1, and at time t6, the assist output voltage decreases to the assist limit. The assist limit is a voltage at which the assist output current cannot be substantially supplied in relation to the output voltage of the AC side power supply boost circuit 32 (also written as "AC side output voltage"). Here, a method of combining the power output from the AC side power supply boost circuit 32 and the power output from the assist power supply unit 50 will be described in detail. The output voltages of the AC side power supply boost circuit 32 and the assist power supply unit 50 vary due to fluctuations in the motor load and the associated feedback control of the main control unit 40 and the sub control unit 80, so that the output voltage of the assist power supply unit 50 alternately exceeds and falls below the output voltage of the AC side power supply boost circuit 32. Of these, a current is generated from the assist power supply unit 50 to the motor 14 only during the period in which the output voltage of the assist power supply unit 50 exceeds the output voltage of the AC side power supply boost circuit 32. Therefore, the lower the output voltage of the assist power supply unit 50, the shorter the period in which the output voltage of the AC side power supply boost circuit 32 exceeds the output voltage of the AC side power supply boost circuit 32, and the smaller the assist output current that flows within a certain period of time. The operation of the assist power supply unit 50 below the assist limit is inefficient because the time during which the assist output voltage exceeds the AC side output voltage (the time during which the assist output current can be supplied) is short, and while the assist output current is small or cannot be output, power is consumed by the boost operation of the assist power supply unit 50. In this comparative example, the available assist time is limited to about three minutes, until the assist output voltage drops to the assist limit.

In contrast, according to the current limit variable mode of Fig. 6(A), the assist output voltage is secured by lowering the target values of the assist output current and assist output power in response to the drop in battery voltage before the assist output voltage drops to near the assist limit, and the assist possible time can be extended to, for example, about 7 minutes. The target values of the assist output current and assist output power are not limited to two stages, and may be three or more stages in response to the drop in battery voltage.

In the air compressor 1, in addition to the variable current limiting mode, the user may be able to select at least one of the high current mode and the low current mode described below as the driving mode on the operation panel unit 19. This allows for suitable response to different usages by each user, improving operability.

Figure 7 (A) is a time chart showing an example of the time change of the assist output voltage, assist output current (assist output power), and battery voltage in the high current mode of the air compressor 1. In the high current mode, the assist output current is always allowed to be equal to or greater than the limit current (from the start to the stop of assist control) regardless of the remaining capacity of the battery pack 5A. The sub-controller 80 fixes the target value of the assist output current to Ia and the target value of the assist output power to Pa. When the battery voltage drops to the current limit voltage Va at time t2, the sub-controller 80 stops the assist control. In the high current mode, although the assist possible time is short, unlike the comparative example shown in Figure 7 (B) (the same comparative example as Figure 6 (B)), inefficient operation when the assist output voltage is near the assist limit is suppressed, and the power of the battery pack 5A can be effectively used.

Figure 8 (A) is a time chart showing an example of the time change of the assist output voltage, assist output current (assist output power), and battery voltage in the low current mode of the air compressor 1. In the low current mode, the assist output current is always prohibited from exceeding the limit current (from the start to the stop of assist control) regardless of the remaining capacity of the battery pack 5A. The sub-controller 80 fixes the target value of the assist output current to Ib and the target value of the assist output power to Pb. Until time t8, the assist output voltage is maintained at 370V, the assist output current is maintained at Ib, and the assist output power is maintained at Pb. After time t8, even if the assist power supply unit 50 is operated at maximum capacity, the assist output voltage, assist output current, and assist output power decrease from the target values along with the decrease in the battery voltage due to the decrease in the battery voltage. When the battery voltage decreases to the assist stop voltage Vb (30V) at time t9, the sub-controller 80 stops the assist control. In the low current mode, compared to the variable current limiting mode, the high power assist in the first half is not provided, but the available assist time can be increased by, for example, up to about 10 minutes.

(Second control example) Figures 10 to 13 show four examples of the change over time in the pressure inside the tank and the battery voltage of the air compressor 1. Figures 10 and 11 explain the case where assistance is provided by battery pack 5A alone, but similar control is also applied when assistance is provided by battery pack 5B alone, and when assistance is provided by both battery packs 5A and 5B. In Figures 12 and 13, "battery 1" refers to one of battery packs 5A and 5B, and "battery 2" refers to the other of battery packs 5A and 5B.

In Figure 10, operation of the air compressor 1 begins at time t10. At time t10, the battery voltage is lower than the early assist start voltage V2. Therefore, the sub-control unit 80 sets the rising assist start pressure (the tank pressure that is the threshold for starting assist control) when the pressure inside the tank is rising to P1, and also sets the rising assist start load corresponding to this.

Between time t10 and time t11, the motor 14 is driven only by the output power of the AC power supply boost circuit 32, and assist control is not performed. Between time t10 and time t11, the slope of the increase in the tank pressure becomes gentler as the load increases due to the increase in the tank pressure.

When the pressure inside the tank rises and reaches P1 at time t11, the load on the motor 14 changes from less than the rising assist start load to greater than or equal to the rising assist start load, and the sub-control unit 80 starts assist control (output from the assist power supply unit 50). The load on the motor 14 can be derived from the sum of the AC load current and the assist output current, and the pressure inside the tank. The start of assist control increases the slope of the rise in the pressure inside the tank.

When the pressure inside the tank reaches the rising assist stop pressure P3 at time t12, the load on the motor 14 becomes equal to or greater than the rising assist stop load, and the sub-control unit 80 stops the assist control. By stopping the assist control, the slope of the increase in the pressure inside the tank becomes smaller. Since the assist output current is stopped at time t12, the battery voltage recovers.

From time t12 to t13, the motor 14 is driven only by the output power of the AC power supply boost circuit 32, and the pressure inside the tank rises. At time t13, air consumption by the pneumatic tool connected to the air compressor 1 begins, and the pressure inside the tank begins to decrease.

When the pressure inside the tank decreases and reaches the descent assist start pressure P4 at time t14, the load on the motor 14 drops from above the descent assist start load to below the descent assist start load, and the sub-control unit 80 starts assist control. With the start of assist control, the downward slope of the pressure inside the tank becomes smaller.

When the battery voltage drops to the assist stop voltage V1 at time t15, the sub-control unit 80 stops the assist control. The halt of the assist control causes the downward slope of the pressure inside the tank to become steeper. When the pressure inside the tank drops to the work stop pressure (pressure at which work is impossible) P6 at time t16, the supply of compressed air from the air compressor 1 to the pneumatic tool is stopped.

In Figure 11, operation of the air compressor 1 begins at time t20. At time t20, the battery voltage is lower than the early assist start voltage V2. Therefore, the sub-control unit 80 sets the rising assist start pressure when the pressure inside the tank is rising to P2 (P2 > P1), and also sets the rising assist start load corresponding to this.

Between time t20 and time t21, the motor 14 is driven only by the output power of the AC power supply boost circuit 32, and assist control is not performed. Between time t20 and time t21, the slope of the increase in the tank pressure becomes gentler as the load increases due to the increase in the tank pressure.

When the pressure inside the tank rises and reaches P2 at time t21, the load on the motor 14 changes from less than the rising assist start load to greater than or equal to the rising assist start load, and the sub-control unit 80 starts assist control. With the start of assist control, the slope of the rise in the pressure inside the tank becomes larger.

When the pressure inside the tank reaches the rising assist stop pressure P3 at time t22, the load on the motor 14 becomes equal to or greater than the rising assist stop load, and the sub-control unit 80 stops the assist control. By stopping the assist control, the slope of the rise in the pressure inside the tank becomes smaller. Since the assist output current is stopped at time t22, the battery voltage recovers.

From time t22 to t23, the motor 14 is driven only by the output power of the AC power supply boost circuit 32, and the pressure inside the tank rises. At time t23, air consumption by the pneumatic tool connected to the air compressor 1 begins, and the pressure inside the tank begins to decrease.

When the pressure inside the tank decreases and reaches the descent assist start pressure P4 at time t24, the load on the motor 14 drops from above the descent assist start load to below the descent assist start load, and the sub-control unit 80 starts assist control. The descent assist start pressure P4 and the descent assist start load are the same regardless of the battery voltage, and are the same as in Figure 10. The start of assist control reduces the slope of the decrease in the pressure inside the tank.

When the pressure inside the tank drops to the descent assist stop pressure P5 at time t25, the sub-control unit 80 stops the assist control. Stopping the assist control increases the rate at which the pressure inside the tank drops. When the pressure inside the tank drops to the work stop pressure (pressure at which work is impossible) P6 at time t26, the supply of compressed air from the air compressor 1 to the pneumatic tool is stopped. Note that the work stop pressure P6 may be greater than the descent assist stop pressure P5.

In FIG. 12, the operation from time t30 to t36 is the same as the operation from time t20 to t26 in FIG. 11. However, when the assist control starts at time t34, the sub-controller 80 performs assist using only the battery pack with the larger remaining capacity (higher output voltage) (battery 2 in FIG. 12). In this way, when the pressure inside the tank is decreasing, if the battery pack with the higher battery voltage is used first, the battery voltage will drop before the pressure inside the tank drops to the light load region, so that assist control can be suppressed from being performed in the light load region when the battery voltage is high. . As a variant, assist may be performed using only the battery pack with the smaller remaining capacity (lower output voltage) (battery 1 in FIG. 12).

In Figure 13, at time t40, the voltages of battery packs 5A and 5B are equal and both are greater than the early assist start voltage V2. The pressure inside the tank reaches the target value and operation of air compressor 1 is stopped. At time t41, air consumption by the pneumatic tool connected to air compressor 1 begins, and the pressure inside the tank starts to drop. In response, motor 14 starts to be driven only by the output power of AC side power supply boost circuit 32, but because the amount of air consumed is greater, the pressure inside the tank drops.

When the pressure inside the tank decreases and reaches the descent assist start pressure P4 at time t42, the load on the motor 14 drops from above the descent assist start load to below the descent assist start load, and the sub-controller 80 starts assist control of only one of the battery packs 5A, 5B (battery 1 in Figure 13). With the start of assist control, the downward slope of the pressure inside the tank becomes smaller.

At time t43, the output voltage of the battery pack used for assist drops to the battery switching judgment voltage V3, and the sub-control unit 80 switches the battery pack used for assist because the pressure inside the tank at that time is below the battery switching judgment pressure P7.

When the pressure inside the tank drops to the descending assist stop pressure P5 at time t44, the sub-control unit 80 stops the assist control. Stopping the assist control increases the rate at which the pressure inside the tank drops. When the pressure inside the tank drops to the work stop pressure P6 at time t45, the supply of compressed air from the air compressor 1 to the pneumatic tool is stopped.

Figure 14 (A) is a flowchart of assist control when the pressure inside the tank of the air compressor 1 rises. The sub-controller 80 waits until the pressure inside the tank exceeds P1 (No in S21). When the pressure inside the tank exceeds P1 (Yes in S21), the sub-controller 80 proceeds to check the battery voltage (S22). If the battery voltage is lower than the early assist start voltage V2 (Yes in S22), the sub-controller 80 starts assist control (S24). If the battery voltage is equal to or higher than the early assist start voltage V2 (No in S22), the sub-controller 80 waits until the pressure inside the tank rises to P2 (No in S23). When the pressure inside the tank exceeds P2 (Yes in S23), the sub-controller 80 starts assist control (S24).

In this way, when the remaining capacity of the battery pack 5A satisfies the power limiting condition, the sub-controller 80 limits the power output from the assist power supply unit 50. In other words, when the battery voltage (remaining battery capacity) decreases, the sub-controller 80 decreases the rising assist start load. Specifically, when the battery voltage is lower than the early assist start voltage V2, the sub-controller 80 decreases (sets smaller) the rising assist start pressure at which assist control is started, and decreases (sets smaller) the rising assist start load, compared to when the battery voltage is higher than the early assist start voltage V2. In other words, when the remaining capacity of the battery pack 5A is higher than the early assist start voltage V2, the sub-controller 80 prohibits output from the assist power supply unit 50 in a state where the rising assist start pressure is less than P2. This is because, when the battery voltage is high, if assist control is started in a light load state where the tank pressure is low, the duty is reduced and the peak current is increased, and power efficiency is reduced due to heat generation of the switching elements 52 and 53 (see FIG. 15). Specifically, for example, due to a delay in feedback of the assist output current by the photocoupler 59, there is a timing when a large current must be outputted while the duty is small, and at that time the peak current becomes high (for example, it may exceed 100 A), and power loss increases. In the second control example, when the battery voltage is equal to or higher than the early assist start voltage V2, the assist is performed in the region where the duty is large, by setting the rising assist start pressure to P2 (>P1), and the efficiency decrease can be suppressed. However, since the time required for the pressure in the tank to increase is extended, the user may be able to switch between the rising assist start pressure being set to P1 regardless of the battery voltage and the rising speed of the pressure in the tank being taken, or the power efficiency being taken by the control of FIG. 14(A) on the operation panel unit 19. The rising assist start pressure is not limited to the two types P1 and P2, and may be selected between P1 and P2 according to the battery voltage.

14(A), when both battery packs 5A and 5B are installed and have different output voltages, the output voltage of the battery pack with the lower output voltage may be used to determine the battery voltage in S22. If the output voltage of the battery pack with the lower output voltage is lower than the early assist start voltage V2, the sub-control unit 80 may start assist control for that battery pack alone.

Figure 14 (B) is a flowchart of assist control when the pressure inside the tank of the air compressor 1 drops. The sub-controller 80 waits until the output voltage (battery voltage 1) of one of the battery packs used for assist control is less than V3 and the battery voltage is less than the battery switching judgment voltage V3 (No in S31). When the battery voltage is less than the battery switching judgment voltage V3 (Yes in S31), the sub-controller 80 proceeds to check the pressure inside the tank (S32). When the pressure inside the tank is less than the battery switching judgment pressure P7, the sub-controller 80 switches the battery pack used for assist control and performs assist control (S34). When the pressure inside the tank is equal to or greater than the battery switching judgment pressure P7 (No in S32), the sub-controller 80 continues assist control until the voltage of the battery pack currently used for assist control drops to the assist stop voltage V1 (S33), and then switches the battery pack used for assist control and performs assist control (S34).

According to the control of FIG. 14(B), when the pressure inside the tank is decreasing, it is possible to prevent the battery pack used for assist control in the light load region from switching to a battery pack with a large remaining capacity. In this regard, when the output voltage of a battery pack not used for assist control is lower than the early assist start voltage V2, the control of FIG. 14(B) (branching at S32) is not performed, and assist control is continued until the voltage of the battery pack currently used for assist control drops to the assist stop voltage V1. In addition, the battery switching judgment pressure P7 may be calculated from the slope of the decrease in the pressure inside the tank and dynamically determined.

(Third control example) The third control example is based on the premise that one battery pack is selected from battery packs 5A and 5B to be used for assist control and is supplied with power to the assist power supply unit 50. When the remaining capacity of the selected battery pack falls to a switching remaining capacity that is greater than the assist stop remaining capacity at which assist control is stopped, the sub-control unit 80 switches the battery pack that supplies power to the assist power supply unit 50. Since the remaining capacity of a battery pack is approximately proportional to the assist output power, the sub-control unit 80 indirectly detects the remaining capacity of the battery pack by detecting the output value of the assist output power.

FIG. 16 is a time chart showing an example of the time change of the assist output power and the battery voltage in the third control example of the air compressor 1. At time t50, the sub-controller 80 selects the battery 1, which is one of the battery packs 5A and 5B, and starts the assist control. When the sub-controller 80 detects that the assist output power has dropped to _PLOW at time t51 (the remaining capacity of the battery 1 has dropped to the switching remaining capacity), it temporarily stops the assist control, and at time t52, it selects the battery 2, which is the other of the battery packs 5A and 5B, and resumes the assist control. When the sub-controller 80 detects that the assist output power has dropped to _PLOW at time t53 (the remaining capacity of the battery 2 has dropped to the switching remaining capacity), it temporarily stops the assist control, and at time t54, it selects the battery 1 and resumes the assist control.

When the voltage of battery 1 drops to the assist stop voltage _VLOW at time t55 (when the remaining capacity of battery 1 drops to the assist stop remaining capacity), the sub-controller 80 temporarily stops the assist control, and at time t56 selects battery 2 and resumes the assist control. When the voltage of battery 2 drops to the assist stop voltage _VLOW at time t57 (when the remaining capacity of battery 2 drops to the assist stop remaining capacity), the sub-controller 80 stops the assist control.

FIG. 17 is a flowchart of the assist control of the air compressor 1 in the third control example. The sub-controller 80 operates the motor 14 (S41), sets the battery 1 as the battery pack used for the assist control (S42), and starts the assist control (S43). The sub-controller 80 continues the assist control by the battery 1 until the assist output power becomes less than _PLOW (No in S44). When the assist output power becomes less than _PLOW (Yes in S44), the sub-controller 80 stops the assist control (S45), sets the battery 2 as the battery pack used for the assist control (S46), and starts the assist control (S47). The sub-controller 80 continues the assist control by the battery 2 until the assist output power becomes less than _PLOW (No in S48). When the assist output power becomes less than _PLOW (Yes in S48), the sub-controller 80 stops the assist control (S49), sets the battery 1 as the battery pack used for the assist control (S50), and starts the assist control (S51).

The sub-controller 80 continues the assist control by the battery 1 until the voltage of the battery 1 becomes less than the assist stop voltage _VLOW (No in S52). When the voltage of the battery 1 becomes less than the assist stop voltage _VLOW (Yes in S52), the sub-controller 80 stops the assist control (S53), sets the battery 2 as the battery pack to be used for the assist control (S54), and starts the assist control (S55). The sub-controller 80 continues the assist control by the battery 2 until the voltage of the battery 2 becomes less than the assist stop voltage _VLOW (No in S56). When the voltage of the battery 2 becomes less than the assist stop voltage _VLOW (Yes in S56), the sub-controller 80 starts the assist control (S57).

According to the third control example, in a configuration in which multiple battery packs are switched for use in assist control, when a drop in assist output power is detected, the battery pack selection is switched, allowing preferential use of the section where the maximum assist power can be output, improving convenience. Note that the final stop of assist is determined by voltage because the reason for stopping assist is to avoid over-discharge.

According to this embodiment, by changing the content of the assist control according to the remaining capacity of battery packs 5A and 5B as described above, it becomes possible to switch the assist control appropriately, thereby improving workability.

The present invention has been described above using an embodiment as an example, but it will be understood by those skilled in the art that various modifications are possible to each component and each processing process of the embodiment within the scope of the claims. Modifications will be discussed below.

Although the first to third control examples have been described as independent controls, the above-mentioned effects can be achieved even if only one of the control examples is implemented. In addition, a plurality of operation modes corresponding to each of the first to third control examples may be provided, and the user may select any operation mode using the operation panel unit 19. Of course, the control contents of the first to third control examples described as independent controls may all be implemented at the discretion of the control unit. The number of battery packs that can be attached to the air compressor 1 is not limited to two as exemplified in the embodiment, but is arbitrary. The assist output voltage, battery voltage, time, etc., exemplified as specific numerical values in the embodiment, do not limit the scope of the invention in any way, and can be changed arbitrarily to suit the required specifications.

1...air compressor, 5, 5A, 5B...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, 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 (13)

A load section ;
a first power supply unit connected to the battery unit and configured to output power of the battery unit to the load unit ;
a second power supply unit electrically connected in parallel with the first power supply unit with respect to the load unit and connected to an external AC power supply, the second power supply unit outputting power of the AC power supply to the load unit ;
a control unit that performs assist control to control the first power supply unit and the second power supply unit so that electric powers output from the first power supply unit and the second power supply unit are combined and supplied to the load unit ,
The control unit limits the power output from the first power supply unit when the remaining capacity of the battery unit satisfies a power limiting condition . the first power supply unit boosts a DC output voltage output from the battery unit and outputs the boosted voltage to the load unit ;
the second power supply unit boosts an output voltage output from the AC power supply and outputs the boosted output voltage to the load unit ;
2. The work machine according to claim 1, wherein, as the assist control, the control unit controls the amount of boost of the first power supply unit and the second power supply unit so that the power output from each of the first power supply unit and the second power supply unit is combined and supplied to the load unit . The work machine according to claim 1 , wherein the control unit reduces an upper limit value of the output current of the first power supply unit when a remaining capacity of the battery unit decreases. The control unit is
when the output voltage of the battery unit is greater than a current limit voltage, the output current of the first power supply unit is allowed to be equal to or greater than a limit current;
4. The work machine according to claim 3 , wherein when the output voltage of the battery unit is lower than the current limit voltage, the output current of the first power supply unit is prohibited from becoming equal to or higher than the limit current. The control unit has a drive mode as
a current limit variable mode in which the content of the assist control is changed depending on the remaining capacity of the battery unit;
a high current mode in which the output current of the first power supply unit is always allowed to be equal to or higher than the limited current regardless of the remaining capacity of the battery unit;
5. The work machine according to claim 4 , wherein a low current mode is selectable in which the output current of the first power supply unit is always prohibited from becoming equal to or higher than the limited current regardless of a remaining capacity of the battery unit. The work machine according to claim 5 , wherein the control unit stops the output of the first power supply unit when the output voltage of the battery unit drops to the current limit voltage in the high current mode. The control unit is
When the load applied to the load unit changes from less than the ascent assist start load to equal to or greater than the ascent assist start load, an output from the first power supply unit is started.
The work machine according to claim 1 , wherein the ascent-time assist start load is reduced when the remaining capacity of the battery unit decreases. The control unit is
The work machine according to claim 7 , wherein when the output voltage of the battery unit is smaller than an early assist start voltage, the ascending assist start load is reduced more than when the output voltage of the battery unit is greater than the early assist start voltage. The control unit is
When the load becomes equal to or greater than the ascent assist stop load, the output from the first power supply unit is stopped,
When the load becomes less than the descent-time assist start load from equal to or greater than the descent-time assist start load, an output from the first power supply unit is started.
9. The work machine according to claim 7 , wherein the descent-time assist start load is common regardless of the remaining capacity of the battery unit. A load section;
a first power supply unit connected to the battery unit and configured to output power of the battery unit to the load unit;
a second power supply unit electrically connected in parallel with the first power supply unit with respect to the load unit and connected to an external AC power supply, the second power supply unit outputting power of the AC power supply to the load unit;
a control unit that performs assist control to control the first power supply unit and the second power supply unit so that electric powers output from the first power supply unit and the second power supply unit are combined and supplied to the load unit,
the battery unit includes a plurality of battery packs,
The control unit is
selecting one battery pack from the plurality of battery packs and causing the first power supply unit to supply power thereto;
When the remaining capacity of the selected battery pack falls to a switching remaining capacity that is greater than an assist stop remaining capacity at which the assist control is stopped, the work machine switches the battery pack that supplies power to the first power supply unit. a compression section driven by the load section to compress a gas;
The work machine according to claim 1 , further comprising: a tank portion that stores the gas compressed by the compression portion. A motor;
a first power supply unit connected to the battery unit and configured to output electric power from the battery unit to the motor;
a second power supply unit electrically connected in parallel with the first power supply unit with respect to the motor and connected to an external AC power supply, the second power supply unit outputting electric power from the AC power supply to the motor;
a control unit that performs assist control to control the first power supply unit and the second power supply unit so that electric powers output from the first power supply unit and the second power supply unit are combined and supplied to the motor,
The control unit limits the power output from the first power supply unit when the remaining capacity of the battery unit satisfies a power limiting condition. A motor;
a first power supply unit connected to the battery unit and configured to output electric power from the battery unit to the motor;
a second power supply unit electrically connected in parallel with the first power supply unit with respect to the motor and connected to an external AC power supply, the second power supply unit outputting electric power from the AC power supply to the motor;
a control unit that performs assist control to control the first power supply unit and the second power supply unit so that electric powers output from the first power supply unit and the second power supply unit are combined and supplied to the motor,
the battery unit includes a plurality of battery packs,
The control unit is
selecting one battery pack from the plurality of battery packs and causing the first power supply unit to supply power thereto;
When the remaining capacity of the selected battery pack falls to a switching remaining capacity that is greater than an assist stop remaining capacity at which the assist control is stopped, the work machine switches the battery pack that supplies power to the first power supply unit.

Images