JP4009949B2 - Air compressor and control method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an air compressor that generates compressed air used in an air tool such as an air nailer and a control method thereof.
[0002]
[Prior art]
In general, an air compressor used for a pneumatic tool rotates a crankshaft of a compressor main body by a motor, and reciprocates a piston in a cylinder according to the rotation of the crankshaft, thereby sucking air sucked from an intake valve. It is configured to compress. The compressed air formed in the compressor body is discharged from the exhaust valve through the pipe to the air tank and stored in this tank. The pneumatic tool performs operations such as nailing using compressed air stored in the tank.
[0003]
Since such an air compressor is often carried in a building site and used outdoors or in a crowded place, improvement is required from various viewpoints. As a result of investigating the situation in which the present inventors are used in the field, the requirements and technical issues required by the user can be organized into the following items.
[0004]
(1) Noise reduction Since the air compressor has a mechanism for converting the rotation of the motor into the reciprocating motion of the piston in the cylinder, it is inevitable that considerable noise is generated during the rotation of the motor. In addition, a nailing machine using compressed air from the air compressor generates an operating noise during operation, and therefore, a considerable noise is generated around the construction site in combination with the noise of the air compressor itself. In particular, there is a strong demand for reducing this noise as much as possible when used in an early morning or after the evening in a crowded place.
[0005]
(2) The site where the high-power and high-efficiency air compressor is used is not necessarily in a sufficient power environment, but rather large enough to supply a power supply voltage from another location using a long cord. May be used in an environment where a large amount of compressed air is consumed due to simultaneous use of a large number of pneumatic tools.
[0006]
For this reason, it may not be possible to generate a high power output from the air compressor. If the nail driver is used in a state where the output is insufficient, for example, a so-called nail floating phenomenon occurs, and the nail can be sufficiently driven into the workpiece. The problem of disappearing.
[0007]
Air compressors usually store 26-30 kg / cm ² of air in an air tank, but this air cannot be avoided little by little even when the tool is not used. There is also a problem that the efficiency is lowered.
[0008]
(3) Miniaturization and improvement in portability Some air compressors for pneumatic tools are rarely used as stationary types, but most are portable and are used by bringing them to the construction site. Therefore, it is required to be as small as possible and excellent in portability. Therefore, it must be avoided as much as possible to complicate the configuration of the compressed air generating section and the driving section for driving the compressed air generating section and impair portability.
[0009]
(4) Longer life The air compressor used for an air moving tool has a problem that its life is shorter than a compressor used for a refrigerator or an air conditioner. Since this is used in harsh environments, it may be unavoidable on one side, but it is possible to further extend the life by suppressing fluctuations in load as much as possible and suppressing the generation of useless compressed air. It is desired.
[0010]
(5) Suppression of temperature rise It is difficult to avoid the air compressor from becoming very hot due to the reciprocating motion of the piston in the cylinder and the current flowing through the motor that drives the piston. However, when the compressor is heated to a high temperature, the loss is increased, which can hinder high efficiency. Therefore, there is a strong demand to suppress the temperature rise of the air compressor as much as possible.
[0011]
[Problems to be solved by the invention]
Among several technical problems as described above, the present invention particularly aims to improve the above-mentioned problems of (1) low noise and (2) high power efficiency.
[0012]
Specifically, an object of the present invention is to provide an air compressor that is powerful and easy to use when the amount of air used is large and quiet when the amount of air used is small.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a tank unit for storing compressed air used in a pneumatic tool, a compressed air generating unit for generating compressed air and supplying the compressed air to the tank unit, and generating the compressed air. A drive unit having a motor for driving the unit, a control circuit unit for controlling the drive unit, and a pressure sensor for detecting the pressure of the compressed air in the tank unit, In the air compressor that controls the number of rotations of the motor at a predetermined number of rotations based on a detection signal from the pressure sensor, the control circuit unit is configured to control the value of the pressure P in the tank unit. And memory for storing table information representing the relationship between the value of the pressure change rate ΔP / ΔT of the tank pressure P at the predetermined time ΔT and the rotational speeds of the plurality of levels. And pressure change [Delta] P / [Delta] T value after searching the memory for selecting one of a rotational number of levels of a plurality of stages, an air compressor, characterized in that so as to drive the motor at a rotational speed that is selected.
[0015]
Another feature of the present invention is that the number of rotations of the motor is set in multiple stages such as 0, N, 2N, 3N,... NN (n is an arbitrary number), and one of them is selected by the control circuit unit. This is because the motor is controlled. Thus, by controlling in multiple stages, it is possible to improve the efficiency of generating compressed air compared to conventional on / off control.
Other features of the invention will be more clearly understood from the following description.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
As shown in the conceptual diagram of FIG. 1, an air compressor according to the present invention includes a tank unit 10 that stores compressed air, a compressed air generation unit 20 that generates compressed air, and a drive unit that drives the compressed air generation unit 20. 30 and a control circuit unit 40 for controlling the driving unit 30.
[0017]
(1) Tank unit 10
As shown in FIG. 2, the tank unit 10 has an air tank 10A for storing high-pressure compressed air, and high-pressure compressed air of, for example, 20 to 30 kg / cm ² is passed through a pipe 21 connected to the discharge port of the compression unit 20A. Supplied.
[0018]
The air tank 10A is usually provided with a plurality of compressed air outlets 18 and 19, and in this embodiment, an outlet 18 for taking out low-pressure compressed air and an outlet for taking out high-pressure compressed air. An example in which 19 is attached is shown. Of course, the present invention is not limited to this.
[0019]
The low-pressure compressed air outlet 18 is connected to the low-pressure coupler 14 via the pressure reducing valve 12. Regardless of the pressure of the compressed air on the inlet side of the pressure reducing valve 12, the maximum pressure of the compressed air on the outlet side is determined. In this embodiment, the maximum pressure is selected to a predetermined value in the range of 7 to 10 kg / cm ^2. Has been. Therefore, compressed air having a pressure equal to or lower than the maximum pressure can be obtained from the outlet side of the pressure reducing valve 12 regardless of the pressure of the air tank 10A.
[0020]
The compressed air on the output side of the pressure reducing valve 12 is supplied to the low pressure air tool 51 shown in FIG.
[0021]
On the other hand, the high-pressure compressed air outlet 19 is connected to the high-pressure coupler 15 via the pressure reducing valve 13. Regardless of the pressure of the compressed air on the inlet side, the pressure reducing valve 13 has a maximum pressure of the compressed air on the outlet side. In this embodiment, the maximum pressure is selected to be a predetermined value in the range of 10 to 30 kg / cm ^2. Has been. Accordingly, compressed air having a pressure equal to or lower than the maximum pressure is obtained from the outlet side of the pressure reducing valve 13. The compressed air on the output side of the pressure reducing valve 13 is supplied to the high-pressure air tool 52 shown in FIG.
[0022]
A low pressure pressure gauge 16 and a high pressure gauge 17 are attached to the pressure reducing valves 12 and 13, respectively, so that the pressure of the compressed air on the outlet side of the pressure reducing valves 12 and 13 can be monitored. Further, since the low pressure coupler 14 and the high pressure coupler 15 have different dimensions and are not compatible, the high pressure air tool 52 cannot be connected to the low pressure coupler 14, and the low pressure air is not connected to the high pressure coupler 15. The tool 51 is configured so that it cannot be connected. Such a configuration has already been filed in JP-A-4-296505 by the same applicant as the present invention.
[0023]
A pressure sensor 11 is attached to a part of the air tank 10A, and the pressure of the compressed air in the tank 10A is detected. This detection signal is supplied to the control unit 40 and used for controlling a motor described later. Further, a safety valve 10B is attached to a part of the air tank 10A, and when the pressure in the air tank 10A becomes abnormally high, a part of the air is released to the outside to ensure safety.
[0024]
(2) Compressed air generation unit 20
The compressed air generator 20 generates compressed air by reciprocating the piston in the cylinder and compressing the air drawn into the cylinder from the intake valve of the cylinder. Thus, the compressor itself is already known. is there. For example, in Japanese Patent Application Laid-Open No. 11-280653 filed by the same applicant as the present invention, the rotation of the motor is transmitted to the output shaft through a pinion provided at the tip of the rotor shaft and a gear meshing therewith. A mechanism for reciprocating a piston by movement is disclosed.
[0025]
When the piston reciprocates in the cylinder, the air drawn from the intake valve provided in the cylinder head is compressed. When the piston reaches a predetermined pressure, compressed air is obtained from the exhaust valve provided in the cylinder head. This compressed air is supplied to the aforementioned air tank 10A through the pipe 21 of FIG.
[0026]
(3) Drive unit 30
The driving unit 30 generates a driving force for reciprocating the above-described piston, and includes a motor 33, a motor driving circuit 32, and a power circuit 31 as shown in FIG. The power supply circuit 31 includes a rectifier circuit 313 for rectifying the voltage of the AC power supply 310 of 100 V and a smoothing / boosting / constant voltage circuit 314 for smoothing and boosting the rectified voltage to obtain a constant voltage.
[0027]
Further, if necessary, a voltage detector 311 for detecting the voltage at both ends of the power supply 310 and a current detector 312 for detecting the current flowing through the power supply 310 are provided, and output signals of the detectors 311 and 312 are described later. It is supplied to the control unit 40. These detectors 311 and 312 are used, for example, for control in the case where the motor 33 is rotated at an extremely high speed for a very short time within a range in which a breaker (not shown) of the power source 310 is not cut off. Detailed control is omitted because it is not directly related to the control. The control unit 40 is also involved in obtaining a constant voltage by the constant voltage circuit 314, but the configuration of the constant voltage circuit itself is known and will not be described in detail here.
[0028]
The motor drive circuit 32 includes switching transistors 321 to 326 for generating a U-phase, V-phase, and W-phase pulse voltage from a DC voltage. On / off of each of the transistors 321 to 326 is controlled by the control unit 40. The number of rotations of the motor is controlled by controlling the frequency of the pulse signal supplied to each of the transistors 321 to 326.
[0029]
As an example, the rotational speed N of the motor 33 is set in multiple stages to an arbitrary number n times the reference value N, such as 0 rpm, 1200 rpm, 2400 rpm, and 3600 rpm, and is driven at a rotational speed selected from these. To be controlled.
[0030]
A diode is connected in parallel to each of the switching transistors 321 to 326 in order to prevent the transistors 321 to 326 from being destroyed by a counter electromotive force generated in the stator 33A of the motor 33.
[0031]
Next, the motor 33 includes a stator 33A and a rotor 33B. U-phase, V-phase, and W-phase windings 331, 332, and 333 are formed on the stator 33A, and a rotating magnetic field is formed by current flowing through the windings 331 to 333.
[0032]
In this embodiment, the rotor 33B is composed of a permanent magnet, and is rotated by a rotating magnetic field formed by a current flowing through the windings 331 to 333 of the stator 33A. The rotational force of the rotor 33B becomes a driving force for operating the piston of the aforementioned pressure air generating unit 20 (FIG. 1).
[0033]
The motor 33 is provided with a temperature detection circuit 334 for detecting the temperature of the winding of the stator 33 </ b> A, and the detection signal is supplied to the control unit 40. Further, a rotation speed detection circuit 335 for detecting the rotation speed of the rotor 33B is provided as necessary, and the detection signal is supplied to the control unit 40.
[0034]
(4) Control circuit unit 40
As shown in FIG. 1, the control circuit section 40 includes a central processing unit (hereinafter abbreviated as CPU) 41, a random access memory (hereinafter abbreviated as RAM) 42, and a read only memory (hereinafter abbreviated as ROM) 43.
[0035]
The detection signal of the pressure sensor 11 and the detection signal of the temperature detection circuit 334 are supplied to the CPU 41 via interface circuits (hereinafter abbreviated as I / F circuits) 44 and 45. A command signal from the CPU is supplied to the motor drive circuit 32 of the drive unit 30 via the I / F circuit 45 to control the switching transistors 321 to 326 (FIG. 3).
[0036]
The ROM 43 stores a motor control program as shown in FIG. 4, and the RAM 42 is used to temporarily store data and calculation results necessary for executing the program.
[0037]
(5) Control Program FIG. 4 shows a flowchart of a program stored in the ROM 43 of the control circuit unit 40 of the present invention.
In step 100 of FIG. 4, initial setting is performed, and the rotation speed of the motor 33 is set to N2 (2400 rpm). Next, in step 101, when the rotation speed is changed in step 109 described later, the changed rotation speed is retrieved from the table stored in the RAM of the control circuit unit 40, and the setting value is changed. Is done. In the present embodiment, an example is shown in which the rotational speed N of the motor 33 is controlled in four stages, that is, N0, N1, N2, and N3, and N = 0 rpm, N1 = 1200 rpm, N2 = 2400 rpm, and N3 = 3600 rpm, respectively. It can be controlled at each speed. Of course, the present invention is not limited to such an example, and the rotational speed N can be controlled in multiple stages, and the values of N0, N1, N2, and N3 can be arbitrarily set.
[0038]
In step 102, the pressure P (t) of the compressed air in the air tank 10A is detected by the pressure sensor 11 (FIG. 2). The pressure P (t) is appropriately A / D converted in the control circuit unit 40 and stored in an area in the RAM 42.
[0039]
Next, in step 103, it is determined whether or not the pressure P in the tank 10A has exceeded 30 kg / cm ^2. If so, the routine proceeds to step 104 where control is performed to stop the rotation of the motor 33. That is, in order to control so as to maintain the pressure of the air tank 10A in the range of 26~30kg / cm ² in the present embodiment, by stopping the rotation of the motor 33 when it exceeds 30kg / cm ^2, compression The operation of the air generation unit 20 is stopped.
[0040]
If the pressure P in the air tank 10A does not exceed 30 kg / cm ² , the routine proceeds to step 105, where it is determined whether or not 5 seconds have elapsed from when P (t) was measured (ΔT = 5 seconds). Is called. This is not only to detect the pressure in the air tank 10A but also to detect the pressure change rate ΔP / ΔT. If ΔT = 5 seconds has elapsed, the pressure P (t + ΔT) in the tank 10A is detected again, and the value is stored in the RAM 42 of the control circuit unit 40.
[0041]
In step 107, the control circuit unit 40 calculates the pressure change rate ΔP / ΔT. That is, in this embodiment, ΔT = 5 seconds, a difference ΔP = P (t + ΔT) −P (t) between the pressure P (t) in the tank at a certain time t and the pressure P (t + ΔT) in the tank after ΔT is obtained. Next, ΔP / ΔT is calculated. Usually, since the pressure change in the tank 10A is gradual, ΔT = 5 seconds in this embodiment, but the value of ΔT is appropriately selected according to the mounting location and sensitivity of the pressure sensor 11.
[0042]
Next, at step 108, a rotation speed transition table is selected. The RAM 42 of the control circuit unit 40 stores in advance four types of rotation speed transition determination tables as shown in FIGS. 5, 6, 7, and 8. When the current rotation speed N of the motor 33 is the initial value N2 (= 2400 rpm), the table of FIG. 5 is selected. When the current rotation speed N is N3 (= 3600 rpm), the table of FIG. 6 is selected. Similarly, the table of FIG. 7 is selected when the rotational speed N is N1, and the table of FIG. 8 is selected when N is N0. In each of these tables, the vertical axis represents the pressure P in the tank, and the horizontal axis represents the pressure change rate ΔP / ΔT of the tank pressure, and is used to determine the rotation speed of the motor 33 from these values.
[0043]
Referring to FIG. 5 as an example, first, when the pressure P in the tank exceeds 30 kg / cm ² , the rotational speed is set to N0 regardless of the value of ΔP / ΔT. That is, the motor is stopped. This is natural because the pressure in the tank is always controlled to be kept in the range of 26 kg / cm ² to 30 kg / cm ² .
[0044]
The fact that the pressure change rate ΔP / ΔT is negative means that more compressed air is consumed than the compressed air supplied to the tank 10A. Therefore, the current rotational speed N2 of the motor 33 (= 2400 rpm). Is controlled to switch to a higher rotational speed N3 (= 3600 rpm). In particular, when the pneumatic tools 51 and 52 (FIG. 1) are in full operation, the amount of compressed air consumed is large and the pressure in the tank 10A may decrease rapidly. In this example, ΔP / ΔT When -1 kg / cm ² or more, if the pressure P in the tank is 30 kg / cm ² , the rotational speed is immediately switched to N3. However, when the pressure change rate ΔP / ΔT is relatively small, 0 to −1 kg / cm ² , if the pressure P of the tank 10A is 26 kg / cm ² or more, the motor 33 is continuously operated at the rotational speed of N2, and the tank 10A Switch to N3 when pressure P falls below 26 kg / cm ² . Further, when ΔP / ΔT is in the range of 0 to +1 kg / cm ² , that is, when the supply is slightly higher than the consumption of compressed air, if the pressure P in the tank 10A is 20 kg / cm ² or more, the operation is continued at N2. When it falls below this, it switches to N3.
[0045]
When the value of ΔP / ΔT is in the range of +0.1 to +0.15 kg / cm ² , it indicates that the amount of compressed air in the tank 10A is increasing, so the tank pressure P is 10 kg / cm. If it is ² or more, it continues to rotate at N2, and when it falls below 10 kg / cm ^2, it switches to N3. When [Delta] P / [Delta] T becomes large as + 0.15~ + 0.3kg / cm ^2, rapidly because increased tank pressure P is expected of the motor if the pressure in the tank 10 kg / cm ² or more rotational speed to the current Control is performed so as to decrease from N2 to N1.
[0046]
The above description is a case where the rotational speed of the motor 33 currently in operation is N2, and the transition is made to N0, N3, and N1 from now on. However, when the current rotational speed is N3, N1, and N0, FIG. As shown in FIG. 8, the transition is controlled so as to change according to different patterns.
[0047]
Returning to FIG. 4, in step 109, the selected determination table is searched from P (t + ΔT) and ΔP / ΔT to determine the rotation speed of the motor 33. This rotational speed is stored in the RAM 42 in step 101 and used for controlling the motor 33.
(6) Operation Next, the operation of the apparatus of the present invention will be described.
FIG. 9 shows a change curve of the pressure P in the tank when there is no transition of the rotational speed. This is a state in which, for example, a pneumatic tool is not used at all, and a curve a shows changes when the motor 33 is rotated at 3600 rpm, b is 2400 rpm, and c is 1200 rpm. When the set value of the rotational speed is 2400 rpm, the motor is first switched on, the pressure in the tank rises according to the curve b, reaches 30 kg / cm ² after about 3 minutes, and the motor operation stops. If left as it is, the compressed air in the pressure tank gradually decreases due to air leakage and decreases. When the pressure decreases to 26 kg / cm ^{2, the} motor starts operating again. Motor Likewise 30kg / cm ² in the case of the curve a and c are turned off, the on-off control operation such that on at 26 kg / cm ^2.
[0048]
10 to 13 are diagrams for explaining the transition of the rotational speed when the rotational speed is controlled in multiple stages according to the present invention. FIG. 10 shows a case where the rotational speed N of the motor is changed from a state where it is operated at 3600 rpm to another rotational speed. Similarly, FIGS. 11, 12 and 13 show that the rotational speed N is changed from 2400 rpm, 1200 rpm and 0 rpm to other speeds, respectively. The case where it changes to rotation speed is shown.
[0049]
Referring to FIG. 11 as an example, when the pressure P in the tank changes as shown by curve a in 5 seconds of time T, that is, when it reaches 30 kg / cm ² , N2 (2400 rpm) is changed to N0 (0 rpm). Switch. On the other hand, when the pressure in the tank gradually increases as shown by the curve b and the amount of air consumption is extremely small, the pressure P is reduced because the pressure is switched from N2 to N1 (1200 rpm).
[0050]
Further, as shown by the curve c, the change in the pressure in the tank for 5 seconds is extremely small, and when the amount of air consumption is small, the rotation speed at N2 is maintained, so that the change in the pressure P is kept very small.
[0051]
Furthermore, as shown by curve d, when the amount of air consumed in 5 seconds is large and the pressure P in the tank suddenly drops, it is switched from N2 to N3 (3600 rpm), so the degree of decrease in pressure P is reduced more than before. The The other FIGS. 10, 12, and 13 will not be described in detail. However, since the rotation speed is changed according to the air consumption for 5 seconds, that is, the pressure change rate, in the same manner as described above, the air consumption varies with time. Even when the pressure is large, it is possible to suppress a rapid increase and decrease in the pressure in the tank.
[0052]
【The invention's effect】
As is apparent from the above description, the air compressor according to the present invention determines the number of rotations of the motor set in multiple stages from both the magnitude of the pressure of the compressed air in the pressure tank and the rate of change of the compressed air. Since the motor is controlled according to the number of rotations, the motor operation is controlled not only by maintaining the tank pressure within a predetermined range but also by predicting the air consumption according to the load of the air compressor. it can. Therefore, it is possible to provide an air compressor that is easy to use without extremely reducing the pressure in the tank. In addition, since compressed air can be efficiently generated according to the state of the load, the time during which the motor can be operated at a low rotational speed is increased, and it is possible to provide an air compressor that is quieter than conventional ones. .
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing an embodiment of an air compressor according to the present invention.
FIG. 2 is a top view showing an embodiment of an air compressor according to the present invention.
FIG. 3 is a circuit diagram showing an embodiment of a motor drive circuit in the compressor of the present invention.
FIG. 4 is a flowchart showing an embodiment of a program used for controlling the compressor of the present invention.
FIG. 5 is an explanatory diagram of a rotation speed transition determination table used for controlling the compressor of the present invention.
FIG. 6 is an explanatory diagram of a rotation speed transition determination table used for controlling the compressor of the present invention.
FIG. 7 is an explanatory diagram of a rotation speed transition determination table used for controlling the compressor of the present invention.
FIG. 8 is an explanatory diagram of a rotation speed transition determination table used for controlling the compressor of the present invention.
FIG. 9 is a pressure change curve diagram for explaining the operation of a conventional compressor.
FIG. 10 is a pressure change curve diagram for explaining the operation of the compressor of the present invention.
FIG. 11 is a pressure change curve diagram for explaining the operation of the compressor of the present invention.
FIG. 12 is a pressure change curve diagram for explaining the operation of the compressor of the present invention.
FIG. 13 is a pressure change curve diagram for explaining the operation of the compressor of the present invention.
[Explanation of symbols]
10: tank part, 10A: pressure tank, 10B: safety valve, 11: pressure sensor, 12, 13: pressure reducing valve, 14, 15: coupler, 16, 17: pressure gauge, 18, 19: outlet, 20: compressed air Generation unit, 21: pipe, 30: drive unit, 31: power supply circuit, 32: motor control circuit, 33: motor, 33A: stator, 33B: rotor, 311: voltage detector, 312: current detector, 334: temperature Detection circuit, 335: Rotation speed detection circuit, 40: Control circuit unit, 41: CPU, 42: RAM, 43: ROM, 44, 45: I / F circuit

Claims (3)

A tank section for storing compressed air used in a pneumatic tool; a compressed air generating section for generating and supplying compressed air to the tank section; and a driving section having a motor for driving the compressed air generating section. A control circuit unit for controlling the drive unit, and a pressure sensor for detecting the pressure of the compressed air in the tank unit, the control circuit unit based on a detection signal from the pressure sensor In the air compressor for driving and controlling the rotation speed of the motor at a plurality of predetermined levels of rotation speed, the control circuit section includes a value of the tank section pressure P and a change in the tank pressure P during a predetermined time ΔT. A memory for storing table information representing the relationship between both values of the rate ΔP / ΔT and the number of rotations at the plurality of levels, and the memory from the values of the pressure P and the pressure change rate ΔP / ΔT Search for An air compressor characterized in that one is selected from a plurality of stages of rotation speeds, and the motor is driven at the selected rotation speeds. In claim 1, the number of rotations of the motor is set in multiple stages such as 0, N, 2N, 3N,. An air compressor characterized by that. A tank section for storing compressed air used in a pneumatic tool; a compressed air generating section for generating and supplying compressed air to the tank section; and a driving section having a motor for driving the compressed air generating section. In the method of controlling an air compressor having a control circuit unit for controlling the drive unit, the value of the pressure P of the compressed air in the tank unit and the value of the pressure change rate ΔP / ΔT at a predetermined time ΔT, A step of previously storing in a memory the relationship between the motor rotational speed levels determined in advance in a plurality of levels, a step of detecting the pressure P of the compressed air in the tank section, and a pressure at a predetermined time ΔT of the pressure P Calculating a change rate ΔP / ΔT, searching the memory from both the pressure P of the tank section and the pressure change rate ΔP / ΔT, and selecting a motor rotation speed level; And a step of driving the motor at a selected number of revolutions.

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