JPH03270689A - air compressor - Google Patents

Abstract

PURPOSE:To prevent useless power consumption by interrupting provision of three-phase driving pulses to a driving means during an interval of reciprocal motion of piston in which the piston is subjected to inertia. CONSTITUTION:When a piston reaches a top dead center (crank angle pi), a top dead center sensor 4 outputs a detection signal which is fed to a CPU 14. The CPU 14 commands an inverter module (INV) 17 to interrupt provision of three-phase driving pulse. Consequently, the piston is subjected to inertia of itself or due to the motion of a pulley and moves from the top dead center toward a bottom dead center (crank angle 2pi). When the piston reaches the bottom dead center, the CPU 14 commands the INV 17 to start provision of the three-phase driving pulse. When the INV 17 resumes provision of the three- phase driving pulse, the piston moves from the bottom dead center toward the top dead center (crank angle 4pi) thus pressure feed the air.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application The present invention relates to an air compressor that pumps air by reciprocating movement of a piston.

``Prior Art'' Conventional air compressors include turbo-type air compressors, which pump air by the rotational motion of an impeller, and positive displacement air compressors, which pump air by reducing the volume of a displacement chamber. be.

Further, positive displacement air compressors include reciprocating air compressors that pump air through reciprocating motion of a piston, and rotary air compressors that pump air through rotational motion of a rotor.

Among these, reciprocating air compressors have a rotatable boot mounted on a crankshaft that causes a piston to reciprocate. On the other hand, a pulley is rotatably attached to the rotating shaft of the electric motor, and a belt is stretched between these pulleys. By supplying commercial frequency three-phase alternating current to the motor, the rotational motion of the motor's rotating shaft is converted into reciprocating motion of the piston via two pulleys, a belt, a crank, etc. Air is then pumped.

"Problem to be solved by invention" By the way, in the conventional reciprocating air compressor mentioned above,
During the reciprocating movement of the piston, the inertia force due to the movement of the piston and pulley acts during the period from top dead center to bottom dead center, so the full load output of the electric motor is not required.

However, in the past, the full load output of the motor was supplied even during this period, which resulted in wasted power consumption.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an air compressor that does not consume unnecessary power.

``Means for Solving the Problems'' The invention according to claim 1 provides an air compressor that converts the rotational motion of a rotating shaft of an electric motor into a reciprocating motion of a piston to pump air. a driving means for converting into a phase driving pulse and applying it to the electric motor; and a period during which an inertial force acts on the piston during the reciprocating movement of the piston;
The driving device is characterized in that the driving device includes a control device for stopping output of the three-phase driving pulses.

Second, the invention according to claim 2 is an air compressor that converts the rotational motion of a rotating shaft of an electric motor into a reciprocating motion of a piston to pump air, which converts three-phase alternating current into three-phase driving pulses of a predetermined frequency. a driving means for converting the torque and applying it to the electric motor; a torque detecting means for detecting the torque generated in the electric motor and outputting a torque detection signal; The present invention is characterized in that the drive means includes a control means for stopping the output of the three-phase drive pulses.

"Operation" According to the invention described in claim I, the drive means converts the three-phase alternating current into three-phase drive pulses of a predetermined frequency and applies the three-phase drive pulses to the electric motor. This converts the rotational movement of the rotating shaft of the electric motor into the reciprocating movement of the piston, and the air is then pumped. and,
The control means causes the drive means to stop outputting three-phase drive pulses during a period during which an inertial force acts on the piston during the reciprocation of the piston.

According to the second aspect of the invention, the driving means converts the three-phase alternating current into three-phase driving pulses of a predetermined frequency and applies the converted three-phase driving pulses to the motor. This converts the rotational motion of the rotating shaft of the electric motor into the reciprocating motion of the piston, which then pumps air. Further, the torque detection means detects the torque generated in the electric motor and outputs a torque detection signal.

When the torque detection signal is larger than a preset value, the control means causes the drive means to stop outputting the three-phase drive pulses.

"Embodiment" Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic front view showing the external configuration of an air compressor according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the electrical configuration of FIG. The main body of the machine, 2 is an air tank, and 3 is a T5 booby which is provided inside the air compressor main body 1 and is rotatably attached to a crankshaft for reciprocating the piston.

Further, reference numeral 4 denotes a top dead center detection sensor that detects that the pulley 3 has reached the top dead center and outputs a detection signal.
It consists of a magnet 5 attached to the peripheral edge of the air compressor body 1, and a Hall element 6 attached to a position facing the magnet 5 of the air compressor main body l.

Furthermore, 7 is a three-phase induction motor, 8 is a pulley rotatably attached to the rotating shaft of the motor 7, 9 is a belt stretched between pulley 3 and pulley 8, and 10 is shown in FIG. 4(a). A power supply that supplies three-phase alternating current at a commercial frequency (50 Hz) shown in FIG. A sensor 13 is a torque converter that detects the torque generated on the rotating shaft of the electric motor 7.

Here, FIG. 3 shows a more detailed block diagram of FIG. 2. In this figure, parts corresponding to those in FIGS. 1 and 2 are given the same reference numerals, and their explanations will be omitted. In FIG. 3, 14 is a CPU (central processing unit) that controls each part, 15 is a converter module that converts input three-phase AC to DC of a predetermined voltage, and 16 is a voltage/frequency control circuit, which is connected to CPU 4. The output control signal is inputted to control the DC voltage and frequency output from the converter module 15.

Reference numeral 17 is an inverter module, which inputs the DC output from the converter module 15 to drive the electric motor 7.
Outputs three-phase drive pulses to drive the. 18 is an A/D converter that converts the respective output signals of the top dead center detection sensor 4 and the current sensor I2 into digital data; 19 is a feedback that inputs the output data of the A/D converter 18 and outputs a feedback signal It is a circuit.

In such a configuration, first, when a three-phase AC at a commercial frequency is supplied from the power supply IO to the control circuit 11, the three-phase AC is converted into DC at a predetermined voltage in the converter module 15, and is then supplied to the inverter module 17. is input. At this time, the DC voltage and frequency output from the controller module 15 are controlled by a voltage/frequency control circuit 16 that receives a control signal output from the CPU 14.

Next, in the inverter module 17, the DC output from the converter module 15 is converted into three-phase drive pulses that drive the electric motor 7, and outputted.
can be added to. Here, an example of the waveform of the line voltage Vu-v of the drive pulse is shown in FIG. 4(c).

As a result, the rotating shaft of the electric motor 7 rotates, and this rotational motion is transmitted via the pulley 8, belt 9, pulley 3, crank (not shown), etc., and the piston (not shown) moves from the bottom dead center (crank angle 0). Move toward top dead center (crank angle π). As a result, air is pumped. here,
The relationship between the reciprocating motion of the piston and the angle of the crank is shown in FIG. 4(b).

Then, when the piston reaches the top dead center (crank angle π), the top dead center detection sensor 4 outputs a detection signal. This detection signal is converted into digital data by the A/D converter I8, and is input to the foot check circuit 19.
This becomes a foot check signal and is input to the CPU I4.

As a result, the CPU 4 controls the inverter module 17.
command to stop the output of three-phase drive pulses. Therefore, as shown in FIG. 4(c), the inverter module 17 no longer outputs three-phase drive pulses, so the piston (not shown) is driven upward by the inertial force caused by the movement of the piston itself and the bobbin. It moves from the point (crank angle π) toward the bottom dead center (crank angle 2π).

When the piston reaches the bottom dead center (crank angle 2π), the CPU 14 instructs the inverter module I7 to start outputting three-phase drive pulses. Therefore, the inverter module 17 again outputs three-phase drive pulses as shown in FIG. 4(c).

As a result, the rotating shaft of the electric @ 7 rotates, and this rotational motion is transmitted via the pulley 8, belt 9, pulley 3, crank (not shown), etc., and the piston (not shown) moves to the bottom dead center (crank angle 2π). The engine moves toward top dead center (crank angle 4π), and air is pumped out.

By repeating the operations described above, compressed air is efficiently pumped.

Note that during the above-described operation, the current sensor 12 detects the current fluctuation of the three-phase drive pulses supplied from the control circuit 11 to the motor 7, and the current fluctuation detection signal is
/D converter 18 converts it into digital data,
The signal is input to the feedback circuit 19, becomes a feedback signal, and is input to the CPU 14.

On the other hand, the torque generated in the electric motor 7 is detected by the torque converter 13, and the torque detection signal is sent to the CPU 14.
is input.

Therefore, the CPU 14 uses the input feedback signal and torque detection signal to control the inverter module 1.
The pulse waveform of the drive pulse output from 7 is controlled.

Note that in the above-described embodiment, the top dead center detection sensor 4
We have shown an example in which the output signal of the piston is used to stop the drive pulse between the top dead center and the bottom dead center of the reciprocating movement of the piston.
The torque required by the air compressor is set in advance, and when the torque generated in the electric motor 7 detected by the torque converter 13 becomes larger than the set required torque, the torque is output from the inverter module 17. The output of the drive pulse may be stopped or limited.

Furthermore, in the embodiment described above, an example was shown in which both the current sensor 12 and the torque converter I3 were provided, but the torque fluctuation of the electric motor 7 and the current fluctuation detected by the current sensor 12 are almost the same. Therefore, either one of these may be provided.

Further, in the embodiment described above, an example was shown in which the drive pulses were pulses at regular intervals, but the width of the electric drive pulses may be varied. That is, the electric motor 7 is controlled by pulse width modulation 1 (PWM (Pulse Width
It may also be controlled by Modulation). Further, as described above, by stopping the output of pulses during the period from the top dead center to the bottom dead center of the piston, even more efficient control can be performed.

In addition, in the embodiment described above, a three-phase induction motor was used as the motor 7, but any motor can be used as long as it can be driven by three-phase pulse drive signals output from the control circuit II. You may also use

"Effects of the Invention" As explained above, according to the present invention, there is no need for wasted power consumption, so there is an effect that power consumption can be significantly suppressed.

[Brief explanation of drawings]

FIG. 1 is a schematic front view showing the external configuration of an air compressor according to an embodiment of the present invention, FIG. 2 is a block diagram showing the electrical configuration of FIG. 1, and FIG. 3 is a three-phase AC line voltage V
FIG. 4(b) is a diagram showing an example of the relationship between the reciprocating motion of the piston of the air compressor l and the angle of the crank, and FIG. 4(c) is a diagram showing an example of the waveform of U-V. It is a figure which shows an example of the waveform of the i-interval voltage Vv-1 of the drive pulse output from. 1st vA l...Air compressor body, 2...Air tank, 3°8...Pulley, 4...Top dead center detection sensor, 5. ...Magnet, 6...
...Hall element, 7...Electric motor, 9...
・Belt, 10...Power supply, II...Control circuit, 12...Current sensor, 13...Torque converter, 14...CPU (control means)
, 15...Converter module (driving means)
, I6... Voltage/frequency control circuit, 17...
...Inverter module (driving means), 18...
...A/D converter, 19...feedback circuit. Figure 2

Claims (2)

[Claims] (1) In an air compressor that converts the rotational motion of a rotating shaft of an electric motor into a reciprocating motion of a piston to pump air, a drive that converts three-phase alternating current into three-phase drive pulses of a predetermined frequency and applies them to the electric motor. An air compressor comprising: a control means for causing the drive means to stop outputting the three-phase drive pulses during a period when an inertial force acts on the piston during reciprocating motion of the piston. (2) In an air compressor that converts the rotational motion of a rotating shaft of an electric motor into a reciprocating motion of a piston to pump air, a drive that converts three-phase alternating current into three-phase drive pulses of a predetermined frequency and applies them to the electric motor. means; torque detection means for detecting torque generated in the electric motor and outputting a torque detection signal; and when the torque detection signal is larger than a preset value, the three-phase drive pulse is applied to the drive means. An air compressor comprising: a control means for stopping the output of the air compressor.