JP2000283052A - Air compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the consumed electric power of an electric motor and increase the starting torque of the electric motor. SOLUTION: An electric motor 12, by which a compressor main body 7 is driven, is connected to the compressor main body 7 for compressing the air taken in from the outside. The electric motor 12, constituted by a reluctance motor, is connected to an electricity supply control device 20 constituted bv an inverter control part 31. A rotation detector 19 for detecting the rotation of the electric motor 12 is connected to the inverter control part 31. Thereby, the inverter control part 31 drives the electric motor 12 by the three phase electrification control at the start time of the electric motor 12 and drives the electric motor 12 by the two phase elecrification control, after the number of rotation of the electric motor 12 reaches the set number of rotation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air compressor suitably used for, for example, compressing air, and more particularly to an air compressor in which a compressor body is driven by an electric motor.

[0002]

2. Description of the Related Art Generally, an air compressor comprises an electric motor as a driving source, a compressor body which is driven by the electric motor and discharges compressed air to each of the storage tanks while compressing air sucked from outside. Is known (for example, JP-A-10-246185).

[0003] In this type of conventional air compressor, an electric motor drives a crankshaft of a compressor body to rotate, and a piston reciprocates in a cylinder in accordance with the rotation of the crankshaft. Is compressed in the compression chamber. The compressed air compressed in the compression chamber of the compressor body is discharged from the discharge chamber side to a tank via a pipe or the like, and stored in the tank.

[0004]

By the way, in the above-mentioned prior art, a condenser motor, an induction motor or the like is used as an electric motor for driving the compressor body. However, when a condenser motor is used as the electric motor, the electric motor rotates at a constant speed regardless of the load of the compressor body, so there are many areas where the power of the electric motor cannot be used effectively. Along with
There is a problem that electric power consumption of the electric motor is large.

[0005] Further, since the starting torque of the electric motor is insufficient, it is necessary to provide a load reducing device such as an unloader in the compressor body in order to reduce the load applied to the electric motor when starting the air compressor. there were.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide an air compressor capable of reducing the power consumption of an electric motor and increasing the starting torque of the electric motor. It is an object.

[0007]

According to a first aspect of the present invention, there is provided an air compressor including an electric motor including a three-phase stator coil and a rotor rotated by the stator coil. The compressor body is driven by rotation of the rotor of the electric motor and compresses air sucked from the outside, rotation detection means for detecting rotation of the electric motor, and the electric motor based on a detection signal from the rotation detection means. Motor control means for controlling power supply to the motor, the motor control means comprising: three-phase conduction control means for sequentially supplying power to all of the three-phase stator coils; Two-phase energization control means for selectively energizing the stator coils of
Selecting one of the three-phase energization control means and the two-phase energization control means according to a detection signal from the rotation detection means;
And energization control switching means for controlling energization to the electric motor by the selected energization control means.

[0008] With this configuration, it is possible to generate a large rotating torque with little fluctuation by the three-phase conduction control means, and to rotate the electric motor while reducing power consumption by the two-phase conduction control means. it can. Further, the energization control unit can select one of the three-phase energization control unit and the two-phase energization control unit in accordance with the rotational torque required for the electric motor. For this reason, the energization control switching means selects the three-phase energization control means when a large rotation torque is required, such as at the time of start-up, based on a detection signal from the rotation detection means. It is possible to select a two-phase energization control unit with low power.

According to a second aspect of the present invention, the energization control switching means selects the three-phase energization control when the electric motor is started at a low rotational speed, and the rotational speed reaches a set rotational speed after the electric motor is started. After that, the configuration is such that the two-phase conduction control means is selected.

Thus, the energization control switching means selects the three-phase energization control means when a large rotation torque is required, such as when the electric motor is started at a low rotational speed. Also, after the rotation speed reaches the set rotation speed after starting the electric motor,
A certain amount of rotational torque is generated in the electric motor.
For this reason, the energization control switching means selects the two-phase energization control means with low power consumption.

Further, the invention of claim 3 is that the three-phase conduction control means is configured to suppress the current of the power supply input to the motor control means to a predetermined first set current value or less.

Thus, the three-phase conduction control means suppresses the current of the power supply input to the motor control means to a predetermined second set current value or less, so that the three-phase conduction control means drives the electric motor. When this is the case, it is possible to prevent the value of the input current from the external power supply from becoming excessively large.

Further, the invention according to claim 4 is characterized in that the two-phase energization control means controls a current value of a power supply inputted to the motor control means to a predetermined second current value or less, The present invention is configured to include a rotation speed limiter that suppresses the rotation speed of the electric motor to a predetermined maximum rotation speed or less.

[0014] With this configuration, the current value limiting means suppresses the current of the power supply input to the motor control means to be equal to or less than the predetermined second set current value. When driving
It is possible to prevent the value of the input current from the external power supply from becoming excessively large. In addition, since the rotation speed limiting means suppresses the rotation speed of the electric motor to a predetermined maximum rotation speed or less, the compressor body is prevented from being damaged by rotating the electric motor at a rotation speed higher than necessary. Thus, durability and reliability can be improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a two-stage air compressor will be described in detail as an air compressor according to an embodiment of the present invention with reference to FIGS.

In FIG. 1, reference numerals 1 and 1 denote a pair of storage tanks (hereinafter referred to as tanks 1) which are separated to the left and right and extend in parallel with each other. Each of the tanks 1 has a substantially cylindrical shape using a metal tube or the like. And is connected by a lower frame 5 and an upper frame 6 described later. On both ends in the longitudinal direction of each tank 1, legs 2, 2,... Are attached at lower positions thereof, and transport handles 3, 3 are attached at upper positions.

A protective cover 4 for covering a compressor body 7, an electric motor 12, and the like, which will be described later, is provided on each tank 1 as shown in FIG. 1, and the protective cover 4 is removed as necessary. It has become so. 3 to 5 show a state in which the protective cover 4 is removed.

Reference numerals 5 and 5 denote lower frames which are located below the respective tanks 1 and connect the respective tanks 1 in the left-right direction. The lower frames 5 have high rigidity as shown in FIGS. It is made of a metal fitting or the like, and is fixed to each tank 1 by means of welding or the like at both ends in the longitudinal direction (front-back direction) of each tank 1.

Reference numerals 6 and 6 denote upper frames which are located above the respective tanks 1 and connect the respective tanks 1 in the left-right direction. For example, they are fixed to the tanks 1 by means of welding or the like at a distance in the longitudinal direction (front-back direction) of each tank 1. The upper frames 6, 6 support the compressor body 7 together with the electric motor 12 from below.

Reference numeral 7 denotes a compressor body mounted between the tanks 1 and mounted on the upper frame 6. The compressor body 7 comprises:
A first-stage compression mechanism 9 including a substantially cylindrical crankcase 8, a cylinder 9A and a cylinder head 9B provided to protrude in the radial direction of the crankcase 8, and an opposite side of the first-stage compression mechanism 9; And a second stage compression mechanism 10 composed of a cylinder 10A and a cylinder head 10B provided in the crankcase 8 as shown in FIG.

As shown in FIG. 3, the first stage compression mechanism 9 and the second stage compression mechanism 10 are provided so as to laterally protrude leftward and rightward, and pistons (in the cylinders 9A and 10A) are provided. (Not shown) is slidably inserted. Also,
The cylinder heads 9B and 10B include a suction valve, a discharge valve (both not shown) and the like, and these two compression mechanisms 9 and 10 are connected via a communication pipe 11.

As described above, the compressor body 7 according to the present embodiment is configured as a so-called horizontally opposed two-stage air compressor.

An electric motor 12 is provided between the tanks 1 and provided on the rear side of the crankcase 8. The electric motor 12 is, for example, an inverter-controlled synchronized Schrag-type reluctance motor. As shown, a motor case 13 disposed coaxially with the crankcase 8 and a motor case 13 disposed in the motor case 13, for example,
Stator 14 composed of phase stator coils U, V, W
And a rotor 15 provided on the inner peripheral side of the stator 14 and made of an iron-based material or the like, and a rotating shaft 16 fitted on the inner peripheral side of the rotor 15 and rotating together with the rotor 15.

Here, the rotary shaft 16 is provided so as to extend through the compressor body 7 and the motor case 13 of the electric motor 12 in the axial direction. The rear side is inserted into the rotor 15 of the electric motor 12. Both ends of the rotating shaft 16 protrude outward from the compressor body 7 and the motor case 13. The lower part of the motor case 13 and the lower part of the crankcase 8 partially enter between the tanks 1 and 1 to make the overall height of the air compressor as low as possible.

The electric motor 12 is connected to an external power supply via a power supply control device 20 described later. Thus, the electric motor 12 is rotationally driven by the power supply control device 20 by inverter control.

Reference numeral 17 denotes an intake fan serving as a first cooling fan provided at the front end of the rotary shaft 16 at the front side of the compressor body 7. Reference numeral 18 denotes a rotary shaft 16 at the rear side of the electric motor 12. 2 shows an exhaust fan as a second cooling fan provided on the rear end side of FIG. The intake fan 17 and the exhaust fan 18 allow the cooling air to flow from the front side of the compressor main body 7 to the rear side of the electric motor 12 and the cooling air flow from the front side to the rear side of the power supply control device 20 described later. Is to be distributed.

Reference numeral 19 denotes a rotation detector as rotation detection means provided at the rear end of the motor case 13 for detecting the rotation position of the electric motor 12. And a Hall element for detecting magnetic flux generated by the magnet (both not shown). And the rotation detector 19
Is connected to the inverter control unit 31 of the power supply control device 20 via a wire, and outputs a rotation detection signal corresponding to the rotation position of the rotating shaft 16 to the inverter control unit 31.

Reference numeral 20 denotes a power supply control device as a motor control means for controlling the power supply to the electric motor 12 by an inverter. The power supply control device 20 includes a circuit casing 21 described later and a power supply section as shown in FIGS. 23, and an inverter control unit 31. The power supply control device 20 is located between the tanks 1 and 1 below the compressor body 7 and the electric motor 12.

Reference numeral 21 denotes a substantially box-shaped circuit casing. The circuit casing 21 is formed, for example, by pressing a thin metal plate, and is located between the tanks 1 and 1 and extends in the front-rear direction. And provided above the lower portion 23A at the center of the box portion 21A in the front-rear direction.
1A and a lid 21B defining an accommodation space for accommodating a smoothing circuit 26 and the like to be described later. Both ends in the front-rear direction of the box portion 21A are fixed to the lower frame 5 by bolts 22 and the like.

Reference numeral 23 denotes a power supply unit for supplying drive power to the electric motor 12. The power supply unit 23 is located at a middle portion in the longitudinal direction of each tank 1 and has a box portion 21 A of the circuit casing 21.
Attached to.

The power supply unit 23 includes a power cable 24
Connected to an external commercial power supply, etc.
A rectifier 25 composed of a bridge circuit composed of a diode for rectifying a single-phase AC voltage, a smoothing circuit 26 composed of a plurality of capacitors 26A connected to the rectifier 25 for smoothing the rectified voltage and outputting a DC voltage; Circuit 26
Inverter control unit 3 provided between the motor and the electric motor 12
By opening and closing in response to the control signal from the control signal 1, the DC voltage by the smoothing circuit 26 is pulse-modulated and output to the electric motor 12 as a pseudo AC voltage having a variable frequency, for example, from six power transistors 27 A. And a transistor circuit 27.

A reactor 28 composed of a coil or the like is connected between the power cable 24 and the rectifier 25, and the reactor 28 is attached to the front end of the box 21A. The reactor 28 prevents a current containing many harmonic components from flowing toward an external commercial power supply when converting a single-phase AC voltage to a DC voltage, and improves the power factor. . Also, the transistor circuit 27
It is attached to the heat radiating plate 29 and is located below the electric motor 12 and near the exhaust fan 18.

Numeral 30 denotes a current detector provided between the power supply cable 24 of the power supply unit 23 and the rectifier 25. The current detector 30 is connected to the inverter control unit 31 and receives an electric motor 12 from an external commercial power supply. And outputs a current detection signal corresponding to the current value supplied to the switch.

Reference numeral 31 denotes an inverter control unit provided on the rear end face side of the circuit casing 21 for controlling the electric motor 12 by inverter. The inverter control unit 31 is constituted by a microcomputer or the like. The output side is connected to the current detector 30 and the like.
3 transistor circuits 27 and the like. Also,
The inverter control unit 31 includes a storage device 31A such as a memory as shown in FIG. 6, and the storage device 31A stores a program shown in FIG.

The inverter control unit 31 switches between three-phase conduction control and two-phase conduction control based on a detection signal from the rotation detector 19, and opens and closes each power transistor 27A of the transistor circuit 27. The frequency of the current and voltage supplied to the stator 14 of the electric motor 12 is changed to control the number of revolutions of the electric motor 12 and the like.

Here, the drive control processing of the electric motor 12 by the inverter control unit 31 will be described with reference to FIG.

First, when the air compressor is operated, a program stored in the storage device 31A of the inverter control unit 31 is operated. In step 1, the power cable 24 is connected to an external power source, and whether or not the main power source is ON is determined. Is determined.

If the determination in step 1 is "NO", the process waits until the main power supply is turned on. On the other hand, when it is determined “YES” in step 1, the process proceeds to step 2 to start the three-phase energization control process.

At this time, the inverter control unit 31 uses the rotation detection signal from the rotation detector 19 to
Of the rotor 15 is recognized. The inverter control unit 31 supplies power to the stator coils V and W from the stator coil U, supplies power to the stator coils W and U from the stator coil V, and outputs the current from the stator coil W to the stator coil U according to the rotational position of the rotor 15. , V are sequentially repeated to gradually increase the rotation speed of the rotor 15.

Next, in step 3, the power supply control device 2 is supplied from an external power supply in response to the current detection signal from the current detector 30.
The current value I input to the power supply unit 23 of 0 is, for example, 15 A as a first set current value set according to the withstand voltage value of the stator coils U, V, W, the power transistor 27A, and the like.
It is determined whether the current value is equal to or less than the set current value I0.

If it is determined "NO" in step 3, the current value I input to the power supply unit 23 exceeds the set current value I0, and the process proceeds to step 4 to determine the current value I
Is set to be equal to or less than the set current value I0.
The current supplied to V and W is limited.

On the other hand, if it is determined "YES" in step 3, the current value I is equal to or less than the set current value I0, and the process proceeds to step 5 where the rotational speed N of the rotor 15 is reduced to the load of the compressor body 7. It is determined whether or not the fluctuation of the torque becomes small and the rotational speed is equal to or higher than a set rotational speed N0 of, for example, about 500 to 800 rpm, which can be driven by inertia.

If "NO" is determined in step 5, since the electric motor 12 has not reached the set number of revolutions N0, it is determined that the electric motor 12 is still in the starting state.
Repeat up to 4. On the other hand, if "YES" is determined in step 5, since the electric motor 12 has reached the set number of revolutions N0, the compressor body 7 is stopped by the inertia even if the rotational torque of the electric motor 12 slightly varies. Since the drive can be performed without any trouble, the process proceeds to step 6 to start the two-phase energization control process.

At this time, the inverter control unit 31 uses the rotation detection signal from the rotation detector 19 to
Of the rotor 15 is recognized. Then, the inverter control unit 31 performs energization from the stator coil U to the stator coil V, energization from the stator coil V to the stator coil W, and energization from the stator coil W to the stator coil U in accordance with the rotational position of the rotor 15. The rotation is sequentially repeated, and the rotation speed of the rotor 15 is gradually increased.

Next, in step 7, the current value I input to the power supply unit 23 according to the current detection signal from the current detector 30 depends on the withstand voltage value of the stator coils U, V, W, the power transistor 27A and the like. It is determined whether or not the set second current value is equal to or less than a set current value I0 of, for example, about 15 A.

If the determination in step 7 is "NO", the current value I input to the power supply unit 23 exceeds the set current value I0, and the process proceeds to step 8 to determine the current value I
Is set to be equal to or less than the set current value I0.
The current supplied to V and W is limited.

On the other hand, if "YES" is determined in step 7, the current value I is equal to or less than the set current value I0. For example, 2 is set in advance in consideration of
It is determined whether the rotation speed is equal to or less than the maximum rotation speed N1 of about 200 to 2300 rpm.

When the determination at step 9 is "NO", the rotational speed N of the electric motor 12 is increased to the maximum rotational speed N1.
Is exceeded, the routine proceeds to step 10, the rotational speed N is suppressed to the maximum rotational speed N1 or less, and the processing of steps 6 to 8 is repeated.

On the other hand, if "YES" is determined in the step 9, the process proceeds to a step 11, and it is determined whether or not the main power is off. When it is determined “NO” in step 11, the air compressor is in the driving state,
Steps 6 to 10 are repeated. On the other hand, if "YES" is determined in the step 11, the process proceeds to the end and the driving of the electric motor 12 is stopped.

The air compressor according to the present embodiment has the above-described configuration. Next, the operation of the air compressor will be described.

First, power is supplied to the electric motor 12 to
When the motor 6 is driven to rotate, the electric motor 12 is driven by three-phase conduction control, and the first-stage compression mechanism 9 and the second-stage compression mechanism 10 operate. At this time, the piston connected via the connecting rod reciprocates in the cylinders 9A and 10A,
Compressed air is supplied from the stage compression mechanism 9 to the second stage compression mechanism 10 via the communication pipe 11. Then, the second-stage compression mechanism 10 further pressurizes the compressed air by the first-stage compression mechanism 9 and discharges the compressed air toward each tank 1. Thereby, the compressed air is stored in the tank 1.

FIG. 9 shows the load torque required for driving the compressor body 7 and the rotation torque generated by the electric motor 12 when the air compressor is started from a stopped state. At this time, during one rotation of the rotor 15, when the piston of the first stage compression mechanism 9 reaches the top dead center position as indicated by the characteristic line a shown by the one-dot chain line in FIG. When the piston of the mechanism 10 reaches the top dead center position, the load torque increases.

Here, when the electric motor 12 is driven by the two-phase energization control, the rotational torque fluctuates greatly as shown by a characteristic line b shown by a dotted line in FIG. For this reason, when the load torque of the compressor main body 7 is maximized in a state where the rotational torque is minimized, the rotational torque of the electric motor 12 is insufficient, and the air compressor stops.

However, in this embodiment, the electric motor 1
2 is driven by the three-phase energization control, the rotational torque thereof is almost always larger than the load torque as indicated by a characteristic line c shown by a solid line in FIG. For this reason, the air compressor starts smoothly without stopping.

Next, when the rotation speed N of the electric motor 12 rises above the set rotation speed N0, the inverter control unit 31
The control method of the electric motor 12 is switched from three-phase conduction control to two-phase conduction control.

FIG. 10 shows the load torque of the compressor body 7 and the rotation torque generated by the electric motor 12 when the electric motor 12 is driven at substantially the maximum rotation speed N1. At this time, while the rotor 15 makes one rotation, FIG.
When the piston of the first stage compression mechanism 9 reaches the top dead center position and when the piston of the second stage compression mechanism 10 reaches the top dead center position, as indicated by a characteristic line d indicated by a dashed line in FIG. Although the load torque increases, the fluctuation range of the load torque decreases.

At this time, since the electric motor 12 is driven by the two-phase conduction control, for example, the stator coils U,
When the energized phase is switched, such as when energization between V is switched to energization between stator coils V and W, the current flowing through each of stator coils U, V and W temporarily decreases. As a result, the rotational torque of the electric motor 12 fluctuates as indicated by a characteristic line e shown by a solid line in FIG. 10, but the inertia force of the rotor 15 and the like acts, so that the fluctuation width is reduced. In addition, an inertia force acts on a piston and the like of the compressor body 7.
Therefore, the load torque of the compressor body 7 is
Even when the rotation torque of the air compressor becomes larger, the air compressor can continue to be driven without stopping.

In the three-phase energization control, the electric motor 12 is driven by passing current through all the stator coils U, V, W of each phase.
The current flowing through W increases, and copper loss and iron loss of the motor winding increase. On the other hand, in the two-phase energization control, the rotation detector 19
The three-phase stator coils U, V,
A two-phase stator coil is selected from W, and the selected two-phase stator coil is energized to obtain a necessary rotational torque. Therefore, the three-phase stator coils U, V,
One-phase stator coil of W is temporarily de-energized. Accordingly, the stator coils U, V,
Since the current flowing in W decreases, copper loss and iron loss of the motor windings decrease as a result.

Thus, according to the present embodiment, one of the three-phase energization control and the two-phase energization control is selected based on the detection signal from the rotation detector 19, so that the three-phase energization control has a large variation with little variation. Rotational torque can be generated, and the electric motor 12 can be rotated while reducing power consumption by reducing copper loss and iron loss of the motor winding by the two-phase conduction control.

When the electric motor 12 is started with the rotation speed N being low, the three-phase energization control is selected.
After the rotation speed reaches 00 rpm, the two-phase conduction control is selected. Therefore, the three-phase conduction control is selected when the electric motor 12 requiring a large rotation torque is started, and after a certain amount of rotation torque is generated in the electric motor 12 or the like. , Low power consumption 2
Phase conduction control can be selected.

In the three-phase energization control, the current value supplied to the power supply unit 23 is suppressed to a set current value I0 of, for example, about 15 A or less by limiting the current supplied to the stator coils U, V, and W. At the start of driving the electric motor 12 by the three-phase conduction control, it is possible to prevent the current value I input from the external power supply from becoming excessively large. This prevents overcurrent from flowing through the stator coils U, V, W, the power transistor 27A, etc.
The durability and reliability of the stator 14, the transistor circuit 27, and the like can be improved.

Further, by limiting the current supplied to the stator coils U, V, W in the two-phase energization control, the current value I input to the power supply unit 23 is suppressed to a set current value I0 of about 15 A or less, for example. Since the number of revolutions N of the electric motor 12 is set to be equal to or less than the maximum number of revolutions N1 of about 2200 to 2300 rpm, the current value I inputted from the external power supply can be prevented from becoming excessively large, and the stator 14 can be prevented. Thus, the durability and reliability of the transistor circuit 27 and the like can be improved. Further, since the rotation speed N of the electric motor 12 is suppressed to the maximum rotation speed N1 or less,
By preventing the compressor main body 7 and the like from being damaged by rotating the electric motor 12 at an unnecessarily high rotation speed N,
Durability and reliability can be improved.

When the compressor body 7 is in a light load state in the two-phase energization control, the stator coils U,
Since the current consumed by V, W, etc. decreases, the electric motor 12 can be driven to rotate at approximately the maximum rotation speed N1. On the other hand, when the compressor body 7 is in a heavy load state in the two-phase energization control, the electric current consumed by the stator coils U, V, W, etc. increases, so that the electric motor 12 is driven to rotate at the set current value I0. be able to. For this reason, the drive of the electric motor 12 can be switched according to the load state of the compressor main body 7, so that the electric motor 12 can be switched as compared with the case where an induction motor that rotates at a constant rotation speed is used as the electric motor 12, for example. Power loss can be reduced and the output can be used effectively for the compression operation. Thereby, the discharge amount of the compressed air at the time of low pressure can be improved.

In this embodiment, steps 2 to 4 in FIG. 8 show a specific example of the three-phase energization control means, and the set current value I0 in steps 3 and 4 is a specific example of the first set current value. Is shown.

Step 5 shows a specific example of the energization control switching means, and the set rotational speed N0 in Step 5 shows a specific example of the set rotational speed.

On the other hand, steps 6 to 11 show specific examples of the two-phase energization control means, steps 7 and 8 show specific examples of the current value limiting means, and steps 9 and 10 show specific examples of the rotation speed limiting means. ing. Then, the set current value I0 in Steps 7 and 8 indicates the second set current value.
The maximum rotation speed N1 at 10 is a specific example of the maximum rotation speed.

In the embodiment, the first and second set current values are set to the same set current value I0. However, the first set current value of the three-phase energization control means and the two The second set current value of the energization control means may be set to a different value.

Further, in the present embodiment, the compressor body 7 comprises a horizontally opposed two-stage air compressor as the compressor body.
However, the present invention is not limited to this. For example, one or three or more stages of air compressors may be used as the compressor main body, and the arrangement of cylinders may be V-shaped or the like. Other forms are also possible.

[0069]

As described above in detail, according to the first aspect of the present invention, the energization control switching means switches one of the three-phase energization control means and the two-phase energization control means according to a detection signal from the rotation detector. With this selection, the three-phase energization control means can generate a large rotation torque with little fluctuation, and the two-phase energization control means can rotate the electric motor while reducing power consumption.

According to the second aspect of the present invention, the three-phase energizing control is selected when the electric motor rotates at a low rotational speed, and the two-phase energizing control is performed after the electric motor reaches the set rotational speed. Is selected, the three-phase energization control is selected when the electric motor requiring a large rotational torque is started, and the two-phase energization control means that consumes less power is started after the electric motor or the like starts operating after a certain amount of rotational torque is generated. You can choose.

According to the third aspect of the present invention, the three-phase conduction control means suppresses the current of the power supply input to the motor control means to a set current value or less, so that the three-phase conduction control means drives the electric motor. At the time of startup, it is possible to prevent the current value input from the external power supply from becoming excessively large. Thus, overcurrent does not flow through the stator coil and the like, and the durability and reliability of the stator and the like can be improved.

Further, according to the invention of claim 4, the two-phase energization control means controls the current of the power supply input to the motor control means to a value equal to or less than the set current value, and the electric motor rotates at the maximum rotational speed. Since the number of rotations is limited to the number or less, the current value input from the external power supply can be prevented from becoming excessively large. Also,
Since the number of rotations of the electric motor is suppressed to the maximum number of rotations or less, it is possible to prevent the compressor body and the like from being damaged by driving the electric motor at an unnecessarily high number of rotations, thereby improving durability and reliability. Can be.

Since the drive of the electric motor can be switched between a drive at a constant rotation speed and a drive at a constant current value in accordance with the load state of the compressor body, an induction motor for rotating the electric motor at a constant rotation speed is provided. As compared with the case where a motor is used, the power loss of the electric motor can be reduced and the output can be used effectively for the compression operation. Thereby, the discharge amount of the compressed air at the time of low pressure can be improved.

[Brief description of the drawings]

FIG. 1 is a front view showing a tank-integrated two-stage air compressor according to an embodiment of the present invention.

FIG. 2 is a plan view showing the air compressor according to the embodiment of the present invention.

FIG. 3 is a plan view showing the air compressor in a state where a protective cover in FIG. 2 is removed.

FIG. 4 is a right side view of FIG. 3 showing the air compressor with a protective cover removed.

FIG. 5 is a cross-sectional view showing a power supply control device and the like of the air compressor as viewed from the direction indicated by arrows VV in FIG. 4;

FIG. 6 is an electric circuit diagram showing a power supply control device according to the embodiment.

FIG. 7 is an electric circuit diagram showing a transistor circuit, a stator coil, and the like according to the embodiment.

FIG. 8 is a flowchart illustrating a drive control process of the electric motor by the inverter control unit according to the embodiment;

FIG. 9 is a characteristic diagram showing the rotational torque of the electric motor when the load torque of the compressor body at the time of starting the electric motor, three-phase energization control, and two-phase energization control.

FIG. 10 is a characteristic diagram showing the load torque of the compressor body when the electric motor rotates near the maximum rotation speed and the rotational torque of the electric motor when two-phase energization control is performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Storage tank 7 Compressor main body 12 Electric motor 14 Stator 15 Rotor 16 Rotation axis 19 Rotation detector (rotation detection means) 20 Power supply control device (motor control means) 23 Power supply part 30 Current detector 31 Inverter control part 31A Storage device U , V, W Stator coil

Continued on the front page (72) Inventor Meiji Odagiri 1116 Koizono, Ayase-shi, Kanagawa Prefecture Tokiko Corporation Sagami Plant (72) Inventor Toshio Inoue 1116 Koizono, Ayase-shi, Kanagawa Prefecture Tokiko Corporation Sagami Plant (72) Inventor Abe Tadashi No. 2, Aichi-cho, Kasugai-shi, Aichi Prefecture Aichi-E Mason Electric Co., Ltd. (72) Inventor Takashi Dari In Aichi-machi, Aichi-cho, Aichi Prefecture Aichi-E Mason Electric Co., Ltd. (72) Inventor Kanbun Takahashi Aichi Prefecture 2nd Aichi-cho, Kasugai-shi Aichi-E Mason Electric Co., Ltd. F-term (reference) BB07 BB09 CC05 FF07 HH01

Claims (4)

[Claims] An electric motor comprising a three-phase stator coil and a rotor rotated by the stator coil;
The compressor body is driven by rotation of the rotor of the electric motor and compresses air sucked from the outside, rotation detection means for detecting rotation of the electric motor, and the electric motor based on a detection signal from the rotation detection means. Motor control means for controlling power supply to the motor, the motor control means comprising: three-phase power supply control means for sequentially supplying power to all of the three-phase stator coils; And two-phase energization control means for selectively energizing the stator coil of any of the above, and selecting one of the three-phase energization control means and the two-phase energization control means based on a detection signal from the rotation detection means. And an energization control switching means for controlling energization of the electric motor by the energization control means. 2. The energization control switching means selects the three-phase energization control when the electric motor is started at a low rotation speed,
2. The air compressor according to claim 1, wherein the two-phase energization control unit is selected after a rotation speed reaches a set rotation speed after the start of the electric motor. 3. 3. The air according to claim 1, wherein the three-phase conduction control means is configured to suppress a current of a power supply input to the motor control means to a predetermined first set current value or less. Compressor. 4. The electric motor according to claim 2, wherein the two-phase energization control means includes: a current value limiting means for suppressing a current of a power supply input to the motor control means to be equal to or less than a second predetermined current value; 4. The air compressor according to claim 1, further comprising a rotation speed limiting means for suppressing the rotation speed to a predetermined maximum rotation speed or less.