JP7365561B2 - blower - Google Patents

Description

The present invention relates to a blower.

2. Description of the Related Art Wiping off dust with a cloth or the like is a method for removing dust adhering to the surfaces of precision instruments and other electronic devices or on electronic circuit boards. However, there are problems in that the static electricity generated during wiping makes it difficult to remove the dust, and that when a damp cloth is used, there is a risk of malfunction of electronic equipment or electric shock due to short circuit.

Therefore, a spray-type air duster is known in which compressed gas is sealed in a can and dust is removed by spraying the compressed gas. Spray-type air dusters are small and lightweight, so they have the advantage of being easy to handle and use. On the other hand, it has the disadvantage of not being able to spray continuously and requiring you to carry a spare air duster with you in case you run out of gas. Furthermore, processing of empty cans is complicated.

In recent years, electric air dusters (an example of "blower") have become known that can solve the problems of spray-type air dusters.

Patent Document 1 discloses a blower in which a motor drives a compressor that generates compressed air. This blower is equipped with a variable resistor whose resistance value changes depending on the amount of pressure on the operating knob, and depending on the resistance value of this variable resistor, the power supply voltage to the motor that drives the valve for blowing out compressed air and the motor The rotation speed of the motor is configured to change.

Patent Document 2 discloses an electric air duster in which a motor drives a compressor that generates compressed air. This air duster is equipped with a crank mechanism that converts the rotational motion of the motor into linear reciprocating motion. Moreover, a compressor consists of a cylinder and a piston. Therefore, when the push button switch on the unit body is turned on, the motor rotates and the piston reciprocates accordingly, making it possible to blow out pulsating compressed air.

Utility Model Publication No. 06-057474 Utility Model Publication No. 06-077873

However, the inventors of the present application discovered that when the remaining capacity of the battery installed in an electric blower decreases, the number of rotations of the motor for driving the compressor decreases. We focused on the issue of the blower being unable to blow out a sufficient amount of air to perform the desired function. If the blower is no longer able to blow out a sufficient amount of air, it becomes difficult to perform its original function as a blower even if there is a remaining amount of battery power. Furthermore, if the output voltage of the battery is increased so that a sufficient number of rotations of the motor can be maintained even when the remaining capacity of the battery decreases, the problem of increasing the size of the battery will arise.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a blower that can suppress a reduction in compressed air blowing force even when the remaining battery capacity decreases.

A blower according to one aspect of the present disclosure blows out compressed air. A compressor for compressing air, a brushless motor for driving the compressor, a battery for applying a voltage for driving the brushless motor, and a system for determining the timing to apply the voltage for driving the brushless motor. It includes a switching element, a sensor that detects the rotation speed of the brushless motor, and a control element that controls the switching element so that the rotation speed of the brushless motor is constant based on a signal detected from the sensor. Note that the switching element is, for example, a FET. Further, the control element is, for example, a control circuit that sends a control signal to the gate of the FET.

Since such a blower includes a brushless motor, the number of revolutions can be easily detected using a sensor. For example, a Hall element can be used as the sensor. Further, the sensor may be configured from a circuit that detects a back electromotive force generated in the windings due to rotation of the rotor. Note that detecting the rotational speed of a brushless motor means not only calculating the rotational speed itself, but also acquiring information that indirectly indicates the rotational speed or rotational speed, such as information indicating changes in the position of the rotor. include. According to such a blower, by using the control element, it becomes possible to easily control the switching element so that the number of rotations becomes constant. The switching element can be composed of a transistor such as an IGBT, for example. By adopting the above configuration, even if the remaining battery capacity decreases, the rotation speed of the motor for driving the compressor is maintained, thereby suppressing a sudden decrease in the blowing force of compressed air. It becomes possible.

Note that the compressor may include a cylinder and a piston. The blower may also include a crank mechanism that converts rotational motion into linear reciprocating motion. By converting the rotary motion of the motor into linear reciprocating motion using the crank mechanism and operating the piston, it becomes possible to blow out compressed air intermittently while rotating the motor at a constant rotation speed. Moreover, even if the remaining battery capacity decreases, it is possible to maintain the rotational speed of the motor for driving the compressor. Therefore, even if the remaining capacity of the battery decreases, it is possible to maintain the peak value of the blowing force of the compressed air blown out from the blower.

Note that, after the brushless motor is started, the control element may be configured to have a period in which the switching element is controlled so that the duty ratio becomes a predetermined value.

According to such a configuration, it is possible to suppress a situation in which the blowing force is insufficient due to an insufficient number of revolutions of the brushless motor when the brushless motor is started. The duty ratio is the ratio of the total time that a switching element is turned on to one cycle. Note that setting the duty ratio to a predetermined value includes a case where the on/off time ratio of a switching element is varied at a predetermined value, such as in PWM control. The period during which the switching element is controlled so that the duty ratio becomes a predetermined value may be a period of one second or less from the start of the brushless motor. Preferably, the period may be 0.5 seconds or less from activation of the brushless motor. During this period, the duty ratio can be set to, for example, 50% or more, preferably 70% or more. After the period has elapsed, the control element may be configured to control the switching element based on the signal detected from the sensor so that the number of rotations of the brushless motor is constant. At this time, the duty ratio of the switching element varies depending on the rotation speed of the brushless motor. Furthermore, when the remaining battery capacity decreases, the duty ratio of the switching element may be controlled to increase so that the number of rotations of the brushless motor remains constant. In other words, the blower has two periods: a first period in which the rotation speed of the brushless motor varies and the duty ratio of the switching element is set to a predetermined value, and a second period in which the rotation speed of the brushless motor is kept constant and the duty ratio of the switching element varies. and a third period in which the rotation speed of the brushless motor is kept constant and the duty ratio of the switching element is increased from the duty ratio in the second period. Moreover, it is preferable that the duty ratio in the first period is configured to be larger than the maximum value of the duty ratio in the second period.

The control element is configured to be able to control the switching element such that the brushless motor operates in a first operation mode in which the brushless motor rotates at a constant speed at a first rotation speed, and the switching element rotates at a second rotation speed lower than the first rotation speed. The switching element can be configured to be controllable so as to operate in a second operating mode in which the switching element rotates at a constant speed.

The blower further includes a switch for selecting a plurality of operation modes in which the air volume or air volume variation pattern of the blown air is different, and the control element operates the switching element based on the operation mode selected by the switch. It may be configured to be controllable.

According to such a blower, it is possible to blow out air with different air volumes or patterns of air volume fluctuations depending on the purpose of use or manner of use. Here, the air volume or the pattern of air volume fluctuation can be expressed, for example, as a waveform with the time axis as the horizontal axis and the air volume as the vertical axis. When the operating mode is different, air with different waveforms will be blown out from the blower.

Perspective view of blower 10 Cross-sectional view of blower 10 Circuit diagram of control unit 28 Flowchart showing how the blower 10 operates Graph showing changes in duty ratio Waveform showing the change in air volume of a blower according to a comparative example

Embodiments of the present invention will be described below with reference to the drawings. The following embodiments are illustrative for explaining the present invention, and are not intended to limit the present invention only to the embodiments. For convenience, the blowing direction of the compressed air of the blower 10 (the extending direction of the nozzle 31) is defined as the front, the opposite direction is defined as the rear, and the main body 11 is perpendicular to the front and rear, with the grip part 12 as a reference. The direction in which the battery 20 exists is referred to as the upper side, and the direction in which the battery 20 exists with respect to the grip portion 12 is referred to as the lower side.

FIG. 1 is a perspective view of a blower 10 according to the first embodiment, and FIG. 2 is a cross-sectional view of the blower 10. The blower 10 is a portable air duster that can blow away dust and the like attached to ticket gates, ticket vending machines, switchboards, personal computers, and other machines or tools by blowing compressed air onto them.

The blower 10 includes a grip section 12 and a main body section 11. The grip portion 12 is a portion that is held by the user of the blower 10 during use, and is provided, for example, so as to protrude downward from the main body portion 11. A battery attachment part 21 to which a battery 20 can be detachably attached is provided at the lower end 12E of the grip part 12. The grip section 12 includes a trigger 13 for the user to start the blower 10, a DC brushless motor 24 (FIG. 3) for driving the main body section 11, and a sensor for detecting the rotation speed of the DC brushless motor 24. 26 (FIG. 3), a control section 28 (FIG. 3) for controlling the voltage applied to the DC brushless motor 24 from the battery 20, a switch for setting the operation mode of the blower 10, and a front section of the blower 10. It is equipped with an LED 23 (FIG. 1) for irradiating.

The grip portion 12 is formed, for example, in a columnar shape extending in the vertical direction so that the user can easily grip it. When the trigger 13 is pressed by the user, the battery 20 and the DC brushless motor 24 are brought into conduction, and the blower 10 is activated. The trigger 13 is provided so as to be exposed on the front-facing surface of the grip portion 12, and is biased forward by a biasing member such as a spring, for example.

As shown in FIGS. 2 and 3, the DC brushless motor 24 includes, for example, a rotor 24R and a stator 24S having three-phase windings 24A to 24C. By causing three-phase alternating current to flow through the three-phase windings 24A to 24C and generating a rotating magnetic field, the rotor 24R having permanent magnets can be rotated. As shown in FIG. 2, the DC brushless motor 24 is installed in an area of the internal space of the grip section 12 that is closer to the main body section 11 than the battery 20. Further, the rotation axis of the rotor 24R of the DC brushless motor 24 is provided, for example, in parallel to the extending direction (vertical direction) of the grip portion 12.

The sensor 26 (FIG. 3) detects the rotation speed of the DC brushless motor 24. The sensor 26 can be configured, for example, from two or more Hall ICs that are provided around the rotor 24R and detect the magnetic field generated by the rotor 24R. Information indicating the rotation speed of the rotor 24R can be acquired based on the phase difference between the magnetic fields detected by each Hall IC. However, the rotation speed of the DC brushless motor 24 can be determined by means other than the Hall IC, such as a detection circuit that detects the rotation speed of the DC brushless motor 24 based on the back electromotive force generated in the three-phase windings 24A to 24C. It's okay.

The control unit 28 controls the timing of applying the DC voltage output from the battery 20 to the windings 24A to 24C of the DC brushless motor 24. The control unit 28 is mounted on the printed wiring board 28P and the printed wiring board 28P, and is configured to determine the timing of applying the DC voltage applied from the battery 20 to the three-phase windings 24A to 24C of the DC brushless motor 24. It includes switching elements 28A to 28F and a control circuit 28M (an example of a "control element") that is mounted on a printed wiring board 28P and controls the switching elements 28A to 28F. The configuration and operation of the control section 28 will be detailed later.

As shown in FIG. 2, the printed wiring board 28P of the control section 28 is installed in a region of the internal space of the grip section 12 that is closer to the battery 20 than the main body section 11. For example, it is provided in a region directly above the battery 20, which corresponds to the lower end 12E of the grip portion 12. Further, the printed wiring board 28P is provided so that its normal line is parallel to the extending direction (vertical direction) of the grip portion 12. As a result of this configuration, the distance between the DC brushless motor 24 and the printed wiring board 28P (the center position of the rotor of the DC brushless motor 24 and the surface of the printed wiring board 28P in the extending direction (vertical direction) of the grip portion 12) ) is larger than half of the total length of the internal space within the grip portion 12 in the same direction. In addition, there are no components serving as a heat source in the gap between the DC brushless motor 24 and the printed wiring board 28P, except for signal lines connecting the three-phase windings 24A to 24C and the output terminals of the control section 28. Therefore, the area of the internal space of the grip section 12 (the area of the casing of the grip section 12) in a cross section perpendicular to the extension direction (vertical direction) of the grip section 12 covers an area of more than half of the total length of the grip section 12 in the extending direction. The ratio of the area occupied by the heat source component of the grip portion 12 to the area (surrounded by the inner wall surface of the body) is smaller than 50%. With this configuration, it is possible to prevent heat generated in the switching elements 28A to 28F on the printed wiring board 28P from being transmitted to the DC brushless motor 24 and deteriorating the braking of the DC brushless motor 24. become.

The switch sets the operating mode of the blower 10. The operation modes include, for example, a normal operation mode, a quiet operation mode, and a high power operation mode. Here, as shown in FIG. 6, for example, the operation mode is represented by a waveform with the time axis as the horizontal axis and the amount of air blown from the blower 10 as the vertical axis. In the normal operation mode, pulsation occurs in which peaks of instantaneous increase in air volume occur at regular intervals. In the silent operation mode, pulsations occur that have a waveform with a smaller peak value of air volume and a longer cycle (lower rotational speed) than in the normal operation mode. On the other hand, in the high power operation mode, compared to the normal operation mode, pulsations occur in a waveform with a larger peak value of air volume and a shorter cycle (higher rotational speed). Note that the trigger 13 and the switch may be constructed from the same component, and the switch may be constructed such that, for example, the operating mode is changed each time the trigger 13 is pressed. As described above, by including the DC brushless motor 24, the blower 10 can operate in a plurality of operation modes in which rotation is maintained at different rotational speeds.

The LED 23 (FIG. 1) illuminates the front of the blower 10. Here, the LED 23 is provided so as to have directivity in a direction parallel to the direction in which the nozzle 31 extends. Therefore, by checking the area illuminated by the LED 23, the user can easily blow compressed air to a desired target area. In particular, when it is desired to blow out compressed air toward dust, etc. located deep inside an obstacle, the angle of the nozzle 31 is maintained after confirming that the LED 23 illuminates the target area located deep inside the obstacle. By blowing out compressed air from the nozzle 31, it is possible to prevent the compressed air from being blocked by obstacles and to blow out the compressed air to the target area.

The main body part 11 is a part that compresses and blows out air. In the present embodiment, the main body 11 includes a crank mechanism 34 (an example of a "transmission mechanism") that engages with the output shaft of the DC brushless motor 24 and converts the rotational motion of the DC brushless motor 24 into reciprocating linear motion; A compressor 35 includes a piston 36 for compressing air by engaging with a crank mechanism 34 and moving in a reciprocating straight line, and a cylinder 38 for accommodating the piston 36, and for blowing out the compressed air in the cylinder 38 in a predetermined direction. A nozzle 31 is provided.

As shown in FIG. 2, the crank mechanism 34 includes, for example, a first gear 34A (motor gear) that is connected to the output shaft of the DC brushless motor 24, coaxially with the output shaft, and rotates integrally with the output shaft; A second gear 34B (crank gear) that meshes with 34A is provided. The second gear 34B is connected to a crank arm 34D that rotates coaxially with the second gear 34B via a crank journal 34C. A crank pin 34E is inserted into the crank arm 34D at a position eccentric from the center. One end of the connecting rod 34F is fixed to a crank pin 34E inserted through the crank arm 34D. Therefore, the end of the connecting rod 34F is swingably supported by the crank arm 34D. The other end of the connecting rod 34F is connected to the piston 36. The moving direction of the piston 36 is restricted to a linear direction by a guide groove or the like. With this configuration, the crank mechanism 34 converts the rotational motion of the DC brushless motor 24 into reciprocating linear motion. Furthermore, the grip portion 12 is provided to extend perpendicularly from the main body portion 11, and the rotation axis of the rotor 24R of the DC brushless motor 24 is provided to be parallel to the extending direction (vertical direction) of the grip portion 12. In addition, since the piston 36 is configured to move back and forth in a straight line in the extending direction (front-back direction) of the main body 11, it is possible to suppress losses due to movement conversion and realize a well-balanced product configuration.

The compressor 35 includes a piston 36 and a cylinder 38. By being connected to the other end of the connecting rod 34F, the piston 36 moves in a reciprocating straight line within the cylinder 38 at the same rotation period as the DC brushless motor 24. The cylinder 38 is provided with an intake port that functions as a suction valve that opens only in the direction from the outside into the compression chamber, and a discharge port that functions as a discharge valve that opens only in the direction from the compression chamber to the outside. While the piston 36 is moving rearward toward the bottom dead center, air is taken into the compression chamber from the space behind the piston 36 through the intake port. On the other hand, while the piston 36 is moving forward toward the top dead center, the volume of the compression chamber decreases, so air is compressed, and when the pressure inside the compression chamber increases, compressed air is discharged from the discharge port. be done.

The nozzle 31 blows compressed air forward. The nozzle 31 is provided to communicate with the discharge port. Therefore, when the piston 36 moves forward and reaches near the top dead center, the pressure inside the compression chamber increases and the compressed air discharged from the discharge port passes through the inside of the nozzle 31 and is blown out from the tip of the nozzle 31 forward.

The battery 20 is a DC power source that supplies power to drive the DC brushless motor 24 of the blower 10 and the like. The battery 20 is composed of, for example, a lithium ion battery capable of outputting a predetermined DC voltage. By attaching the battery 20, the blower 10 can be carried and used. However, the blower 10 may be configured such that the battery is housed within the housing of the blower 10. In this case, the blower 10 may be configured to be able to charge the battery.

FIG. 3 is a circuit diagram of the control section 28 for controlling the DC brushless motor 24. As shown in FIG. The control unit 28 includes a power supply terminal 28V and a ground terminal 28G connected to the output terminal of the battery 20, a power supply line 28L1 and a ground line 28L2 connected to the power supply terminal 28V and the ground terminal 28G, and a power supply line 28L1 and a ground line 28L2. An inverter circuit 28I is provided between the two. The inverter circuit 28I has six switching elements 28A to 28F connected in a three-phase bridge, such as FETs (Field Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors), and connected in parallel to these switching elements 28A to 28F, respectively. It consists of a freewheeling diode and a freewheeling diode. Three output terminals of this inverter circuit 28I are connected to three-phase windings 24A to 24C of the DC brushless motor 24, respectively.

The control unit 28 further includes a storage element, such as a ROM, in which firmware (an example of a "computer program") for controlling the DC brushless motor 24 is recorded, and a processor for executing the firmware. The control circuit 28M includes a driver that generates a control signal for PWM controlling the switching elements 28A to 28F. The control circuit 28M generates a control signal for PWM control (pulse width modulation control) of the switching elements 28A to 28F based on the flowchart shown in FIG. ).

FIG. 4 is a flowchart showing a method of operating the blower 10 according to this embodiment. Further, FIG. 5 is a graph showing changes in the duty ratio of the DC brushless motor 24. As shown in FIG.

As shown in FIG. 4, the blower 10 is started by the user pulling the trigger 13 (step S1). When the blower 10 is started, the control unit 28 sets the duty ratio set in the firmware stored in the storage element as the initial duty ratio (step S2), and starts drive control of the DC brushless motor 24 (step S3). ). Specifically, the control unit 28 reads firmware recorded in the storage element and causes the processor of the control unit 28 to execute the firmware, thereby generating a control signal for PWM controlling the switching elements 28A to 28F. The initial duty ratio is, for example, 72%. Therefore, the total time during which the switching elements 28A to 28F are turned on corresponds to 72% of one cycle. A control circuit 28M included in the control unit 28 generates a PWM signal for rotating the DC brushless motor 24 so as to satisfy the initial duty ratio for a predetermined period after startup, and applies it to the control terminals of the switching elements 28A to 28F. do.

Furthermore, the control unit 28 starts measuring the rotation speed of the DC brushless motor 24 (step S4). Measurement of the current rotational speed of the DC brushless motor 24 consists of the following substeps. First, the measurement timer included in the control unit 28 starts counting (substep SS1). Further, the Hall IC included in the sensor 26 is configured to output a detection signal that detects switching of the magnetic field (substep SS2). The counter included in the control unit 28 counts up the detection signal output from the Hall IC (substep SS3). The control unit 28 determines whether the DC brushless motor 24 has rotated once based on the count value of the counter (substep SS4). The control unit 28 determines whether the DC brushless motor 24 has rotated once by comparing the count value with a predetermined numerical value determined based on the number of permanent magnets included in the rotor 24R, for example. If the count value has not reached a value corresponding to one revolution of the DC brushless motor 24 (NO), sub-step SS2 and sub-step SS3 are executed again.

On the other hand, if the count value of the counter is equal to the value corresponding to one revolution of the DC brushless motor 24 (YES), the control unit 28 determines that the DC brushless motor 24 has made one revolution, and sets the measurement timer at that point. The timer count value of is obtained (substep SS5).

Next, the control unit 28 calculates the rotation speed based on the acquired timer count value. Specifically, the control unit 28 obtains the time (in minutes) required for one rotation of the DC brushless motor 24 based on the timer count value of the measurement timer, and calculates the reciprocal of the time. The rotation speed of the DC brushless motor 24 is obtained (substep SS6). Next, the control unit 28 resets the measurement timer and starts counting the timer (substep SS7).

The control unit 28 can measure the rotation speed of the DC brushless motor 24 in real time by repeatedly executing the above substeps. Note that the current rotational speed measurement process in step S4 may be performed continuously after starting the motor drive in step S3, or may be performed at predetermined intervals (for example, every 100 microseconds to several seconds).

After the rotation of the DC brushless motor 24 is started in step S3, for example, 0.5 seconds have elapsed, the control unit 28 shifts to PI control to keep the rotation speed constant (step S5). Specifically, the control unit 28 changes the initial duty ratio that was fixed in step S2, and resets the duty ratio so that the target rotation speed is achieved. The control circuit 28M generates a PWM signal for rotating the DC brushless motor 24 so as to satisfy the changed duty ratio, and supplies it to the switching elements 28A to 28F. By employing PI control, it becomes possible to stably bring the rotation speed of the DC brushless motor 24 close to the target value. However, this does not preclude controlling the rotational speed to approach the target rotational speed using other control methods.

Next, the control unit 28 determines whether or not the trigger 13 is released from being pressed (step S6). If it is determined that the trigger 13 has been released (YES), the control unit 28 stops supplying the PWM signal and stops driving the DC brushless motor 24 (step S8).

On the other hand, if the control unit 28 determines that the trigger 13 has not been released (NO), the control unit 28 determines whether a preset event such as an error has occurred (step S7 ). If it is determined that an error has occurred (YES), the drive of the DC brushless motor 24 is stopped. On the other hand, if the control unit 28 determines that an event such as an error has not occurred (NO), the control unit 28 measures the rotational speed of the DC brushless motor 24 again (step S4).

The transition of the duty ratio in the control method for the blower 10 as described above will be explained using the drawings. FIG. 5 shows a change in the duty ratio when the trigger 13 of the blower 10 is continued to be depressed when the battery 20 has sufficient remaining power. In FIG. 5, the horizontal axis represents time and the vertical axis represents duty ratio.

As shown in the figure, the duty ratio is kept constant from the time when the trigger 13 is pressed and the DC brushless motor 24 starts rotating (time 0) until time T1. In this embodiment, time T1 is 0.5 seconds. Further, the initial duty ratio is set to be higher than the duty ratio when the time T1 is exceeded and the control is shifted to PI control, and is set to, for example, 72%. Between time 0 and time T1, the rotation speed of the DC brushless motor 24 is not controlled. Therefore, the rotation speed of the DC brushless motor 24 fluctuates.

Next, from time T1 to time T2, the control unit 28 controls the switching elements 28A to 28F so that the rotation speed of the DC brushless motor 24 is constant. From time T1 to time T2, the duty ratio is not necessarily constant and varies as shown in the figure. On the other hand, the rotation speed of the DC brushless motor 24 remains constant. Further, as described above, the initial duty ratio is set to be larger than the duty ratio immediately after shifting to PI control. Time T2 varies depending on the remaining amount of battery 20. For example, if the battery 20 has sufficient remaining power, time T2 will be a long period of time.

Even after time T2, the control unit 28 controls the switching elements 28A to 28F so that the rotational speed of the DC brushless motor 24 remains constant. However, since the remaining capacity of the battery 20 decreases, the duty ratio gradually increases in order to keep the rotational speed of the DC brushless motor 24 constant. Therefore, after time T2, the duty ratio becomes larger than the initial duty ratio of 72%.

As described above, the blower 10 operates between time 0 and time T1, when the rotation speed of the DC brushless motor 24 fluctuates and the duty ratios of the switching elements 28A to 28F are set to predetermined values, and the rotation speed of the DC brushless motor 24. is kept constant and the duty ratios of the switching elements 28A to 28F vary from time T1 to time T2, and the rotational speed of the DC brushless motor 24 is kept constant and the duty ratios of the switching elements 28A to 28F vary from time T1 to time T2. It has a period after time T2 that is higher than the duty ratio of T2. Furthermore, the period after time T2 further includes a period in which the duty ratio is higher than from time 0 to time T1. Further, after time T2, the duty ratio may be configured to gradually increase (however, the duty ratio may temporarily include a constant period). The reason for controlling the blower 10 as described above will be explained below.

FIG. 6 is an example of a waveform pattern showing air volume fluctuations, with the time axis as the horizontal axis and the vertical axis as the blowing force (an example of "air volume") of air blown out from the nozzle of the blower according to the comparative example. As shown in the figure, the blower according to the comparative example generates pulsation in which peaks of instantaneous increase in air volume occur at regular intervals. The peak value of the air volume is approximately 60 to 70 g. Additionally, the frequency of the blower is approximately 50 Hz (6/0. 130 seconds), and the rotation speed of the motor is 15,000 RPM. Note that the gear ratio between the first gear 34A (motor gear) and the second gear 34B is, for example, 5:1.

The inventors of the present application paid attention to the fact that the blower according to the comparative example blows out the first weak pulse of compressed air around the time of 0.03 seconds. Since the blowing force of this pulse is less than 30 g, it has less than half the blowing force of the other pulses. On the other hand, spray-type air dusters can blow out air with the greatest force immediately after pressing the button. For this reason, users who are accustomed to using spray-type air dusters may feel that the blowing force is insufficient when using the blower according to the comparative example, since the first pulse that blows out has only a weak blowing force. be. Furthermore, similar to a spray-type air duster, when you press the trigger for a moment to blow away the dust you are aiming for, there is a possibility that you will not be able to blow off the dust as expected. Furthermore, if the angle of the nozzle fluctuates as a result of blowing out a weak pulse, it becomes difficult to blow out a strong pulse of air toward the target dust or the like.

As a result of trial and error, the inventors of the present application purposefully equipped a portable blower with a brushless motor to realize constant rotation speed control, and also for a very short period of time from the start of operation (for example, when the brushless motor rotates only 10 revolutions). ), the duty ratio is maintained at a constant value without constant rotation speed control, and the duty ratio at that time is higher than the duty ratio when shifting to constant rotation speed control. I came up with the idea of setting it to a value.

As described above, the blower 10 according to the present embodiment can suppress a reduction in the blowing force of compressed air even when the remaining battery capacity decreases. Moreover, it becomes possible to suppress a reduction in the blowing force of compressed air immediately after the start of driving.

The present invention can be modified in various ways without departing from the gist thereof. For example, some components of an embodiment may be removed or replaced with other known configurations within the ordinary creative ability of those skilled in the art.

10 blower, 11 main unit, 12 grip unit, 13 trigger, 20 battery, 24 DC brushless motor, 24A to 24C three-phase winding, 24R rotor, 24S stator, 26 sensor, 28 control unit, 28A to 28F switching element , 28I inverter circuit, 28M control circuit, 28P printed wiring board, 31 nozzle, 34 crank mechanism, 35 compressor, 36 piston, 38 cylinder

Claims (4)

A blower that blows out compressed air where peaks of instantaneous increase in air volume occur periodically ,
A compressor comprising a piston for compressing air and a cylinder accommodating the piston ;
a brushless motor for driving the compressor;
a battery for applying voltage to drive the brushless motor;
a switching element for determining the timing of applying a voltage to drive the brushless motor;
a sensor that detects the rotation speed of the brushless motor;
a control element that controls the switching element so that the rotation speed of the brushless motor is constant based on a signal detected from the sensor;
Equipped with
The control element maintains a predetermined duty ratio higher than the duty ratio at the time of transition to the constant rotation speed control for a predetermined period from the start of driving the brushless motor.
Blower. The control element is configured to be able to control the switching element so as to operate in a first operation mode in which the brushless motor rotates at a first rotation speed, and a second operation mode in which the brushless motor rotates at a second rotation speed. The switching element is configured to be controllable to operate in a driving mode;
A blower according to claim 1 . Further comprising a switch for selecting a plurality of operation modes in which the air volume or air volume variation pattern of air blown from the blower is different,
The control element is configured to be able to control the switching element based on the operation mode selected by the switch.
The blower according to claim 1 or 2 . configured to blow out compressed air having the first peak during the predetermined period;
The blower according to any one of claims 1 to 3..

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