JP4009950B2 - 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.
(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.
(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.
[0004]
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.
[0005]
Air compressors usually store 26-30 kg / cm ² of compressed air in an air tank, but this compressed air is unavoidably leaked even when the tool is not being used. In some cases, there is a problem that the efficiency is lowered.
(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.
(4) Longer life The air compressor used for an air tool has a problem that its life is shorter than that of a compressor used for a refrigerator, an air conditioner or the like. 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.
(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.
[0006]
[Problems to be solved by the invention]
Among several technical problems as described above, the present invention particularly aims to improve the above-described problems of low noise (1) and temperature rise (5).
[0007]
[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, A temperature sensor that detects the motor temperature of the drive unit in an air compressor that drives and controls the rotation speed of the motor at a predetermined number of rotation speed levels based on a detection signal from the pressure sensor; At least one of a voltage detection means for detecting the power supply voltage of the drive section and a current detection means for detecting a load current of the drive section is provided, and the control circuit section is configured to detect the value of the pressure P of the tank section and the predetermined time ΔT. In accordance with both of the pressure change rates ΔP / ΔT of the tank pressure P, one of the plurality of levels of rotation speed is selected, and at least the detected motor temperature, power supply voltage and load current are selected. When one is larger than a predetermined value, it has one feature that the level of the selected rotational speed is lowered by one step.
[0008]
Another feature of the present invention is that when a ripple indicating fluctuations in tank pressure within a time shorter than the predetermined time ΔT is smaller than a predetermined negative number, a predetermined rotational speed level is selected, and the ripple is a predetermined negative number. When the value is larger, the table is to select a rotation speed level by searching table information indicating a relationship between both the pressure P value and the pressure change rate ΔP / ΔT and the rotation speed level.
[0010]
Another feature of the present invention is that the motor is controlled in at least three stages of high speed, medium speed, and low speed.
Other features of the invention will be more clearly understood from the following description.
[0011]
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.
[0012]
(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.
[0013]
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.
[0014]
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.
[0015]
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.
[0016]
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.
[0017]
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.
[0018]
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.
[0019]
(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.
[0020]
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.
[0021]
(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.
[0022]
A voltage detector 311 for detecting the voltage across the power source 310 and a current detector 312 for detecting the load current are provided, and output signals from the detectors 311 and 312 are sent to the control unit 40 described later. Supplied. These detectors 311 and 312 are used for control in the case where the motor 33 is rotated at an extremely high speed for a very short time within a range where a breaker (not shown) of the power source 310 is not cut off. 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.
[0023]
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.
[0024]
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.
[0025]
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.
[0026]
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.
[0027]
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).
[0028]
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.
[0029]
(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.
[0030]
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).
[0031]
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.
[0032]
(5) Control Program FIG. 4 is a flow chart showing an embodiment of a program stored in the ROM 43 of the control circuit section 40 of the present invention.
In step 101 of FIG. 4, initialization is performed, and the rotation speed of the motor 33 is set to N2 (2400 rpm). Next, at step 104, the rotational speed data used for controlling the air compressor of the present invention is stored. 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. 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.
[0033]
In step 105, the pressure sensor 11 (FIG. 2) detects the pressure P (T) of the compressed air in the air tank 10A. The pressure P (T) is appropriately A / D converted in the control circuit unit 40 and stored in an area in the RAM 42.
[0034]
Next, in step 106, 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 107 and control is performed so as to stop the rotation of the motor 33. That is, in order to control as in the present embodiment is maintained the pressure in the air tank 10A in the range of 26~30kg / cm ^2, to stop the rotation of the motor 33 when it exceeds 30kg / cm ^2, compression The operation of the air generation unit 20 is stopped.
[0035]
When the pressure P in the air tank 10A does not exceed 30 kg / cm ² , the routine proceeds to step 112, where it is determined whether or not 5 seconds have elapsed since the time 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.
[0036]
In step 113, the control circuit unit 40 calculates the pressure change rate ΔP / ΔT. That is, in this embodiment, ΔT = 5 seconds, and the 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.
[0037]
Next, at step 114, 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. 6, 7, 8, and 9. When the current rotation speed N of the motor 33 is the initial value N2 (= 2400 rpm), the table of FIG. 6 is selected. When the current rotation speed N is N3 (= 3600 rpm), the table of FIG. 7 is selected. Similarly, when the rotation speed N is N1, the table of FIG. 8 is selected, and when N is N0, the table of FIG. 9 is selected. 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.
[0038]
Referring to FIG. 6 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 .
[0039]
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 is If the pressure P in the tank is 30 kg / cm ² when the pressure is −1 kg / cm ² / sec or more, 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 / sec, if the pressure P of the tank 10A is 26 kg / cm ² or more, the motor 33 is continuously operated at the rotation speed of N2, and the tank When the pressure P of 10 A falls below 26 kg / cm ² , it switches to N3. Further, when ΔP / ΔT is in the range of 0 to +0.1 kg / cm ² / sec, that is, when the supply is slightly higher than the consumption of compressed air, it continues if the pressure P in the tank 10A is 20 kg / cm ² or more. Drive at N2, and switch to N3 when lower than this.
[0040]
When the value of ΔP / ΔT is in the range of +0.1 to +0.15 kg / cm ² / sec, this indicates that the amount of compressed air in the tank 10A is increasing, so the tank pressure P is 10 kg. If it is more than / cm ^2, it will continue to rotate at N ² and switch to N 3 if it falls below 10 kg / cm ² . When ΔP / ΔT increases to +0.15 to +0.3 kg / cm ² / sec, an increase in the tank internal pressure P is predicted rapidly. Therefore, if the pressure in the tank is 10 kg / cm ² or more, the rotational speed of the motor is reduced. Control is performed so that the current N2 is reduced to N1.
[0041]
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, FIGS. As shown in FIG. 9, the transition is controlled so as to change according to different patterns.
[0042]
Returning to FIG. 4, in step 115, the selected determination table is searched from P (T + ΔT) and ΔP / ΔT to determine the rotation speed of the motor 33.
In step 116, it is determined whether or not the rotational speed N selected in step 115 is N3 (= 3600 rpm). If the determination is affirmative (YES), the process proceeds to the next step 121, and the temperature t of the motor 33 is measured. . That is, even if it is determined from the rotation speed transition determination table that the rotation speed of the motor 33 needs to be set to a high speed N3, it is determined whether or not N3 is finally selected according to the temperature of the motor 33. . The motor temperature t is usually measured by the temperature of the motor windings 331 to 333, but the present invention is not limited to this.
[0043]
Next, in step 122, it is determined whether or not the temperature t measured is greater than a predetermined value. In this embodiment, the predetermined value is set to 120 ° C., but the present invention is not limited to this. If the determination in step 122 is negative (NO), the temperature of the motor 33 is 120 ° C. or less, and it is determined that there is no problem even if the rotational speed of the motor is further increased, and the rotational speed N of the motor 33 is set to N3 (= 3600 rpm). ) (Step 123). On the other hand, when the determination in step 122 is affirmative (YES), it is determined that if the number of rotations of the motor 33 is further increased, the temperature of the motor 33 is excessively increased and the efficiency of the air compressor is decreased. N is set to medium speed N2 (= 2400 rpm).
[0044]
Thus, the present invention not only controls the rotational speed of the motor 33 in accordance with the pressure change in the tank, but also detects the motor temperature, particularly the motor winding temperature, and the rotational speed is controlled in accordance with this temperature. Therefore, the excessive temperature rise of the motor 33 can be prevented.
[0045]
Next, another embodiment of the control program for the air compressor of the present invention will be described with reference to FIG.
[0046]
First, in step 101, initial setting is performed, and the rotational speed N of the motor 33 is set to N2 = 2400 rpm, as in FIG. In this embodiment, there are two types of sampling periods ΔT for taking the signal detected by the pressure sensor 11 of the pressure tank 10A into the control circuit unit 40, the short period ΔT1 is 0.05 seconds, and the long period ΔT2 is 5 seconds. That is, as i = 0, 1, 2, 3,... 100, a change in the tank internal pressure is detected once every 0.05 seconds from the difference between P (i−1) and P (i), and P (i = 0 ) And P (i = 100), a pressure change is detected once every 5 seconds. In this embodiment, the short cycle is set to 0.05 seconds, but this is set to detect a ripple in the tank pressure that occurs when a nailing machine or the like that consumes a large amount of air is activated at one time. It is a matter of course that the present invention is not necessarily limited to this numerical value because it is a period that depends on the pneumatic tool used. Similarly, the long period of 5 seconds is a period set for detecting a change in pressure in the tank due to the use state of the pneumatic tool, and is merely an example and is not limited to this value.
[0047]
Next, the routine proceeds to step 104 where the rotational speed data used for controlling the air compressor of the present invention is stored. In this embodiment, the rotation speed N of the motor 33 is controlled in four stages of N0 (= 0 rpm), N1 (1200 rpm), N2 (2400 rpm), and N3 (3600 rpm), so that the values of N0, N1, N2, and N3 are respectively It is stored in an appropriate area of the RAM 42. Although it is easy to set the speed of the motor 33 in more stages, it is desirable that the speed of the motor 33 is at least three stages.
[0048]
Next, in step 105, the pressure P (i) of the compressed air in the tank 10A is measured and stored. In step 106, it is determined whether or not the measured pressure P (i) is greater than 30 kg / cm ^{2. If} the determination is affirmative (YES), the process proceeds to step 107 and the rotational speed N of the motor 33 is set to N0 (0 rpm). Set to. The pressure in the tank 10A shows an example of controlling to maintain a ^{20kg / cm 2 ~30kg / cm 2} , thus the pressure within the tank is stopped the rotation of the motor 33 exceeds 30kg / cm ² in other words, the present embodiment It is done.
[0049]
When the determination in step 106 is negative (NO), the process proceeds to step 108, (i + 1) is substituted for (i), and in step 109, the tank internal pressure P (i) is measured, and the value is the previous P (i -1) and stored. Further, in step 110, the CPU 41 calculates the pressure change rate ΔP1 / ΔT1 (= (P (i) −P (i−1) /0.05) in the short period ΔT1.
[0050]
Further, in step 111, it is determined whether or not the above-mentioned short cycle pressure change rate ΔP1 / ΔT1 is smaller than a predetermined value. This determination is to determine whether or not the pneumatic tool connected to the pressure tank 10A is operating in a manner that consumes a large amount of air in a short time such as continuous nailing. In this embodiment, a predetermined value is set. It is set as -1. When nailing continuously, the pressure in the tank pulsates and the ripple of pressure change increases. When the decrease in ΔP1 in ΔT1 is larger than (−1) (that is, ΔP1 / ΔT1 <−1), it is determined from the magnitude of the ripple, and it is determined that the pneumatic tool is used in a manner such as continuous nailing. Proceed to 125.
[0051]
In step 125, the voltage (V) of the power supply 310 in the power supply circuit 31 (FIG. 3) is detected by the detector 311. In step 126, it is determined whether or not the value is smaller than a predetermined value. In this embodiment, the predetermined value is set to 90V. That is, when the amount of air consumed by the air tool is large, it is desirable to immediately increase the number of rotations of the motor 33 to increase the amount of compressed air generated. For example, another air tool is connected to the tank 10A and used. In this case, the load becomes large and a breaker (not shown) of the power supply circuit 31 (FIG. 3) may be activated. In order to avoid this, whether or not the magnitude of the power supply voltage V is smaller than a predetermined value (90V). This is determined in step 126. If the determination in step 126 is affirmative (YES), that is, that the power supply voltage, which is normally 100 V, is reduced to 90 V or less, it is determined that the load on the power supply 310 is considerably large due to the use of another pneumatic tool or the like. Thus, the rotational speed N of the motor 33 is maintained at N2 (= 2400 rpm).
[0052]
When the voltage of the power supply 310 is 90 V or higher, the process proceeds to step 127, and the current I flowing through the power supply circuit 31 is detected by the current detector 312. Then, in step 128, it is determined whether or not the current I measured is larger than a predetermined value. In this embodiment, the predetermined value is set to 30A. If this determination is affirmative (YES), it is determined that there is a possibility that the breaker of the power supply 310 may be disconnected if the rotational speed N of the motor 33 is increased beyond the current level. Maintain N2 (= 2400 rpm).
[0053]
When the determination at step 128 is negative (NO), the routine proceeds to step 129, where the winding temperature t of the stator 331 in the motor 33 is measured, and further at step 130, it is determined whether this winding temperature t is greater than a predetermined value. The In this embodiment, the predetermined value is set to 120 ° C. If the number of rotations of the motor 33 is further increased while the temperature t of the motor winding is 120 ° C. or higher, the temperature of the motor 33 will rise excessively, which may hinder the operation of the motor, and compression will occur due to excessive temperature rise. Since the compressed air generation efficiency of the air generation unit 20 may be significantly reduced, when the determination in step 130 is affirmative (YES), the process again proceeds to step 132, and the rotational speed N of the motor 33 is maintained at N2 (= 2400 rpm). .
[0054]
If the determination in step 130 is negative (NO), the process proceeds to step 131, where the rotational speed N of the motor 33 is set to N3 (= 3600 rpm).
[0055]
Next, in step 133, i = 0 is set again, and in step 134, it is determined whether or not the internal pressure P (i) of the tank 10A is greater than 30 kg / cm ² . If this determination is affirmative (YES), the process returns to step 107 to stop the rotation of the motor 33. If the determination in step 134 is negative (NO), a calculation is performed in step 135 to replace i + 1 with i, and in step 136 it is determined whether i has reached 100, that is, whether 5 seconds have elapsed. If this determination is affirmative (YES), i = 0 is set (step 102), and the process returns to step 104. The above steps 134 to 136 are for controlling so as to maintain the same rotational speed for 5 seconds since the user feels uncomfortable when the rotational speed of the motor 33 is switched every 0.05 seconds.
[0056]
On the other hand, if the determination in step 111 is negative (NO), that is, if the pressure change rate in the tank in a short time (0.05 seconds) is smaller than the predetermined value, the process proceeds to step 112, and the time is ΔT2 seconds (= It is determined whether or not 5 seconds have elapsed. If this determination is negative (NO), the process returns to step 106, but if affirmative (YES), the process proceeds to step 113, and the pressure change rate ΔP2 / ΔT2 (= (P (i = 100)) over a long period (5 seconds). -P (i = 0)) / 5) is calculated.
[0057]
Next, at step 114, a rotation speed transition table is selected. Steps 114 to 116 are the same as those in the embodiment of FIG. As a result, when the selected rotation speed N is N3 (= 3600 rpm) (step 116), the power supply voltage V is 90 V or more, the load current I is 30 A or less, and the motor winding is determined in the next steps 117 to 122. It is determined whether the line temperature t is 120 ° C. or less. Since the functions of Steps 117 to 122 are the same as those of Steps 125 to 130 described above, a detailed description thereof will be omitted. In short, however, the operation of the power breaker (not shown) is prevented and the overheating of the motor 33 is prevented. It is a flow for.
[0058]
As a result of the determination in steps 117 to 122, if it is determined that the breaker is not cut or the temperature of the motor 33 does not rise excessively even if the rotational speed N of the motor 33 is switched to the maximum speed of 3600 rpm, the process proceeds to step 123. The motor speed is set to N = N3 (= 3600 rpm). However, if the condition is not satisfied, the routine proceeds to step 124 where the rotational speed N of the motor 33 is maintained at N2. That is, in the present invention, when the pressure change rate for a short time (0.05 seconds) is large and when the pressure change rate for a long time (5 seconds) is large, it is predicted that the air consumption will increase, and the rotation speed of the motor 33 However, if the load on the motor 33 is already very heavy and the breaker may be disconnected or the motor winding temperature may increase excessively, the control is performed to maintain the motor at N2.
[0059]
【The invention's effect】
As is apparent from the above description, the present invention is an air compressor that controls the number of rotations of a motor in multiple stages according to the pressure in the tank. Since the motor is rotated at high speed, it is possible to prevent the motor temperature from rising excessively and the efficiency from decreasing.
[0060]
It also has a detection circuit that detects the power supply voltage and load current of the motor power supply circuit. When the power supply voltage is lower than the predetermined value and the load current is higher than the predetermined value, the motor is not rotated at high speed. It is possible to prevent the line temperature from rising excessively and the power breaker from operating.
[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 air compressor of the present invention.
FIG. 4 is a flowchart showing an embodiment of a program used for controlling the air compressor of the present invention.
FIG. 5 is a flowchart showing another embodiment of a program used for controlling the air compressor of the present invention.
FIG. 6 is an explanatory diagram of a rotation speed transition table used for controlling the air compressor of the present invention.
FIG. 7 is an explanatory diagram of a rotation speed transition table used for controlling the air compressor of the present invention.
FIG. 8 is an explanatory diagram of a rotation speed transition table used for controlling the air compressor of the present invention.
FIG. 9 is an explanatory diagram of a rotation speed transition table used for controlling the air 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 (5)

A tank unit for storing compressed air used for a pneumatic tool, a compressed air generating unit for generating compressed air and supplying the compressed air to the tank unit, and a driving unit having a motor for driving the compressed air generating 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, the control circuit unit based on a detection signal from the pressure sensor, In an air compressor that drives and controls the number of rotations of the motor at a predetermined number of levels of rotation, a temperature sensor that detects a motor temperature of the driving unit, and a voltage detection that detects a power supply voltage of the driving unit And at least one of current detection means for detecting the load current of the drive unit, and the control circuit unit is configured to control the value of the pressure P of the tank unit and the rate of change ΔP of the tank pressure P at a predetermined time ΔT. Depending on the value of / ΔT, one of the rotational speeds at the above-mentioned multiple levels is selected, and if at least one of the detected motor temperature, power supply voltage and load current is greater than a predetermined value, it is selected. An air compressor characterized by lowering the rotation speed level by one step. In Claim 1, when the ripple which shows the fluctuation | variation of the tank pressure in the time shorter than the said predetermined time (DELTA) T is smaller than a predetermined negative number, a predetermined rotation speed level is selected and the said ripple is larger than a predetermined negative number. The air is characterized in that the rotation speed level is selected by searching table information indicating the relationship between both the pressure P value and the pressure change rate ΔP / ΔT value with the rotation speed level. Compressor. 2. The air compressor according to claim 1, wherein the control circuit unit controls the motor in at least three stages of high speed, medium speed, and low speed. 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 temperature sensor for detecting the motor temperature of the drive unit, the control circuit unit for controlling the drive unit, and a pressure sensor for detecting the pressure of the compressed air in the tank unit, At least one of a voltage detection means for detecting a power supply voltage and a current detection means for detecting a load current of the drive unit is provided, and the control circuit unit previously sets the rotation speed of the motor based on a detection signal from the pressure sensor. In the control method of an air compressor that performs drive control at a predetermined number of levels of rotational speeds, the control circuit section changes the value of the tank section pressure P and the tank pressure P during a predetermined time ΔT. A first step of selecting one of the rotational speeds of the plurality of levels according to both the values of the ratio ΔP / ΔT, and at least one of the detected motor temperature, power supply voltage, and load current is a predetermined value If larger, a second step of lowering the selected rotational speed level by one step and a third step of driving the motor at the rotational speed determined by the second step are provided. Control method of air compressor. In claim 4, when the ripple indicating the fluctuation of the tank pressure within a time shorter than the predetermined time ΔT is smaller than a predetermined negative number, a predetermined rotational speed level is selected, and the ripple is larger than the predetermined negative number. The air is characterized in that the rotation speed level is selected by searching table information indicating the relationship between both the value of the pressure P and the value of the pressure change rate ΔP / ΔT and the rotation speed level. Compressor control method.

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