JP7639564B2 - Work Machine - Google Patents

Description

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

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, driving the motor when the pressure of the air stored in the tank section is equal to or lower than a predetermined stop threshold, and stopping 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.

JP 2013-68158 A

When the AC power supply is a temporary power supply, when a cord reel is used, or when the AC power supply is shared with other equipment, the voltage supplied from the AC power supply may drop. In such low-voltage conditions, 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 fluctuations become large and vibration increases. One possible solution to this problem is to lower the stop pressure in response 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 of error, which results in a decrease in performance and work efficiency.

In view of the above problems, the present invention aims to provide a work machine that reduces vibration while improving performance and work efficiency.

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 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 ;
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 .
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.

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

The present invention provides a work machine that reduces vibration while improving performance and work efficiency.

1 is a perspective view showing an overall configuration of an air compressor 1 according to a first 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 5-A and 5-B, the circuit block diagram showing a portion including 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. 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, 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. 3 is a control flowchart of the air compressor 1.

In the following, identical or equivalent components, parts, etc. shown in each drawing are given the same reference numerals, and duplicated explanations are omitted as appropriate. The embodiments do not limit the invention but are merely examples. All of the features and combinations thereof described in the embodiments are not necessarily essential to the invention.

(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 a plurality of battery pack mounting portions 45 (two in the illustrated example) on the outer surface of the main body cover (housing) 10, as shown in FIG. 4.

A battery pack 5 can be detachably attached to each battery pack attachment section 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. The battery pack 5 has a storage case and a secondary battery (secondary battery cell) provided within the storage case. The battery pack attachment section 45 has connection terminals that connect to the terminals of the battery pack 5.

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

The compression unit 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 unit 33 in Figures 5A and 5B, which supplies power to the motor 14, is controlled (for example, PWM control) by the main control unit 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 between operating modes, etc. The operation panel 19 also displays warnings about the pressure inside the air tank and overloads, etc.

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 and 12b, which are connected to each other, via the second-stage discharge pipe.

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

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 provide 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.

As shown in FIG. 5A, the air compressor 1 has a motor 14 for rotating the compression section 13 to send compressed air to the air tanks 12a and 12b. The air compressor 1 has 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 5-A and 5-B.

As shown in Figures 5A and 5B, the main circuit section 200 includes 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 a 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 31. A smoothing capacitor 35 is connected to the rectified output side of the rectifier 31. The 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.

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.

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 a boost voltage monitoring signal from the boost voltage detection unit 38, a rotation detection signal from the rotation sensor 41 that detects the rotation of the motor 14, and a pressure detection signal from the pressure sensor 42 that detects the pressure in the air tanks 12a and 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, for example, by PWM control. The compression unit 13 is driven to rotate by the motor 14, and the air discharged from the compression unit 13 is sent to the air tanks 12a and 12b.

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 switch button 194 that instructs switching between operation modes, and an assist button 195 that instructs power assistance 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.

The 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 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 5-A and 5-B as battery power supplies, a sub-control unit 80, a circuit power supply unit 110, and a communication circuit 100. The sub-control unit 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-control unit 80, the communication circuit 100, and the like. The communication circuit 100 constitutes an electrically insulated communication line between the main control unit 40 and the sub-control unit 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.

The battery pack 5-A is connected to the connection terminal 45A of one battery pack mounting section 45, and the battery pack 5-B 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 5-A and 5-B 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-controller 80. The sub-controller 80 receives battery information acquisition signals from the battery packs 5-A and 5-B and acquires their battery information (battery temperature, etc.). The battery packs 5-A and 5-B include control units 44A and 44B, respectively, and can communicate with the sub-controller 80. The main control unit 40, the sub-controller 80, and the control units 44A and 44B of the battery packs 5-A and 5-B constitute the control unit of the air compressor 1.

The assist power supply unit 50 includes a boost DC-DC converter as a boost circuit. The assist power supply unit 50 has switching elements (e.g., MOSFETs) 52, 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, 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.

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 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 5-A and 5-B, 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 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 examples of battery-side power supplies capable of adjusting the output voltage values of the battery packs 5-A and 5-B.

The DC power of one or both of the battery packs 5-A, 5-B 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 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 is provided. 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-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 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 smoothing capacitor 56 on the output side. 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 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 has a rectifier 71 that receives the supply of the AC power source 39 through 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 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 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 unit 78 and the charging voltage control signal from the charging voltage control unit 79 are fed back to the charging power supply drive circuit 75 via a photocoupler 82 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, which 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 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 and off the connection between the connection terminal 45A of one battery pack mounting section 45 and the charging section 70, and a relay 87B (second cutoff circuit) is provided to turn on and off the connection between the connection terminal 45B of the other battery pack mounting section 45 and the charging section 70. A relay 87C is provided to turn on and off the connection between the connection terminal 45A and the assist power supply section 50, and a relay 87D is provided to turn on and off the connection between the connection terminal 45B and the assist power supply section 50. Relays 87A to 87D are each controlled to turn on and off by a relay on/off signal from the sub-controller 80.

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.

The battery packs 5-A and 5-B are each provided with thermistors Th1 and Th2 as temperature detectors that detect the temperature of the internal secondary batteries. The 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 FIG. 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 5-A and 5-B 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 (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").

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, if the AC load current value is about to exceed 15 A, the main control unit 40 lowers the target rotation speed of the motor 14. 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 increases the target rotation speed to maintain the AC load current value of 15A, thereby making it possible to supply insufficient power from one or both of the battery packs 5-A and 5-B. 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.

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, the series diode 323A can be omitted 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) higher than the series diode 82.

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-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 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.

In general, 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 5-A and 5-B so that the potential difference between them is within a specified potential difference value (for example, 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 solve 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 5-A and 5-B exceeds a predetermined potential difference value (0.5V) during power assist with battery packs 5-A and 5-B connected in parallel, the assist will continue until the voltage of one of the battery packs falls below a predetermined voltage value V1, which is the first threshold voltage.

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 viewpoint of preventing contact failure, it is advisable to stop the assist itself when the voltage of one of the battery packs falls below a specified voltage value 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 specified 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.

Figure 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 mentioned above, the tank pressure is detected by the pressure sensor 42, and the detection signal is input to the main control unit 40.

When the motor 14 is driven at time t0, i.e., the air compressor 1 starts operating, 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 the lower the AC input voltage. This is because the lower the AC input voltage, the more the AC input current needs to be increased to compensate for the power.

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.

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 the previously set stop pressure (target pressure) P1 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).

When the AC input voltage is 100V, at time t5, the pressure inside the tank reaches a stop pressure P1 as the second stop pressure, and the motor 14 stops. Whether the AC input voltage is 65V, 80V, or 100V, the pressure inside the tank remains 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 the rotation speed threshold value, and are values that are dynamically determined according to the operating environment such as the AC input voltage.

In FIG. 6, it is assumed that when the AC input voltage in the first half is 65 V, the usage state of the commercial AC power supply 39 by other devices changes during the period from time t5 to t6, causing the AC input voltage to rise 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.

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 load on the motor 14 when restarting increases, increasing the possibility of the motor 14 breaking down. On the other hand, if ΔA is too large, the motor 14 is stopped for a long 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 long time, resulting in poor work efficiency. In addition, the tank pressure also drops significantly, so it takes a long time 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 ΔA lower than pressures P2 and P4, respectively, are examples of the first restart pressure. Pressure P2, which is ΔA lower than pressure P1, is an example of the second restart pressure. After the motor 14 is restarted at time t7, the pressure inside the tank rises again over time.

When the AC input voltage is 100V, 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 90V, 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 80V, at time t10, the motor rotation speed drops to the rotation speed threshold, and the motor 14 stops.

Figure 7 is a control flowchart for the air compressor 1. This flowchart is for the case where the assist combined mode is selected by the assist button 195. In mode 1 (yes in S1), the main control unit 40 sets the stop pressure to Poff1 and the restart pressure to Pon1 (S2). In 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 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 Figure 6.

When 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. When 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 when the motor rotation speed is equal to or lower than the rotation speed threshold (yes in S9), checks the AC input voltage using a signal from the input voltage detection unit 65 (S10).

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 communicates with the sub-control unit 80 to check whether power assistance (hereinafter also referred to as "assisted operation") is being performed using the battery packs 5-A and 5-B (S12).

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

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 acquires the current tank pressure Pv (S15) and sets the stop pressure to Pv and the restart pressure to Pv-ΔA (S16).

If the pressure inside the tank 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 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 pressure Pv), and the determination in S17 is yes.

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), it returns to S1 and restarts the motor 14 by setting the stop pressure and restart pressure according to the operating mode (modes 1 to 3) (S1 to S6, S8).

This embodiment can achieve the following effects:

(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 cause vibration and noise, the vibration and noise will increase in an individual that is likely to cause 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 the 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 tank pressure that can be reached 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 the motor 14 is determined depending on whether the rotation speed is below the threshold value, so that when the AC input voltage decreases, the air compressor 1 can be operated until just before the vibration and noise become significantly large.

(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 pressure in the tank when the motor rotation speed drops to the rotation speed threshold, and restarts the motor 14 when the pressure in the tank drops to the restart pressure. Therefore, compared to a case where a fixed restart pressure is used regardless of the pressure in the tank 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 stop time of the motor 14 is not too long or the drop in the pressure in the tank is not excessive, the restart pressure can be appropriately set so that the restart pressure is not too high, and so that the stop time of the motor 14 is not too long or the drop in the pressure in the tank is not excessive. In a specific case where a fixed restart pressure is used, it is considered that the restart pressure is set low for an individual that is prone to vibration and noise (because if the restart pressure is set high for an individual that is not prone to vibration and noise, the vibration and noise will be 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 pressure inside the tank also drops significantly, so it takes a longer time for the pressure inside the tank 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 is the stop pressure 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.

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

The difference between the pressure inside the tank when the motor 14 is stopped (stop pressure) and the pressure inside the tank when the motor 14 is subsequently restarted (restart pressure) does not have to be a fixed value. For example, the restart pressure may be an internal tank pressure that is a predetermined percentage lower than the stop 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.

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