JP2552561B2 - Control method of induction motor for compressor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a compressor in which an induction motor and a compression element rotationally driven by a rotor of the induction motor are housed in the same case, and more particularly, A control method for controlling the drive torque of the induction motor to reduce vibration and noise of the compressor is provided.

(B) Conventional technology As a control method for such a compressor, Japanese Patent Laid-Open No. 60-602
There were some as described in Japanese Patent Publication No. 86. What is described in this publication is such that the motor output torque is output in synchronization with the change in the load torque applied during one rotation of the electric element that drives the compression element of the compressor.
That is, the load torque is always detected during one rotation of the motor, and the output of the motor is changed to match the load torque.

(C) Problems to be Solved by the Invention In the compressor control system configured as described above, it is necessary to constantly detect the rotational position of the compressor, and a large number of position detectors are required. However, there is a problem in that high accuracy is required, and that the control circuit is complicated because it is necessary to successively calculate and output the output of the motor. Further, when the signal from the position detector is interrupted, proper torque control may not be performed, abnormal vibration may occur, and the pipe may be damaged.

With respect to such a problem, the present invention provides a control system in which abnormal operation does not occur even when an abnormality occurs in the signal from the position detector.

(D) Means for Solving the Problems The present invention is directed to an induction motor in which an AC power whose frequency is arbitrarily set within a predetermined frequency range is supplied to control the rotation speed, and a rotor of the induction motor. The compression element that is driven to rotate by the above is housed in the same case, and the drive torque during one rotation of the induction motor is changed based on the signal detected corresponding to the rotation angle of the compression element. In the induction motor for a compressor, when the signal corresponding to the rotation angle of the compression element is not detected, the induction motor 1
The driving torque during rotation is made constant.

Further, an induction motor in which the alternating-current power whose frequency is arbitrarily set between a predetermined first frequency and a second frequency higher than this frequency is supplied to control the rotation speed, and the rotation of the induction motor. A compression element rotationally driven by the child is housed in the same case, and the drive torque during one rotation of the induction motor is changed based on the signal detected corresponding to the rotation angle of the compression element. In the induction motor for a compressor, when a signal corresponding to the rotation angle of the compression element is detected, it is set to enable the supply of AC power having a frequency equal to or higher than the first frequency, and the rotation angle of the compression element is changed. Third frequency (first frequency <third frequency <second frequency) if no corresponding signal is detected
It is possible to supply the alternating-current power having the above frequency and to keep the driving torque constant during one rotation of the induction motor.

(E) Action When the control system of the present invention is used, even if an abnormality occurs in the signal of the position detector that detects the rotational position of the compression element of the compressor, the compressor does not become abnormal operation and You can continue driving.

(F) Example An example of the present invention will be described below with reference to the drawings. First
The figure is a cross-sectional view of the compressor. In this figure, reference numeral 1 is a closed container in which a compression element 4 and a three-phase induction motor 3 are housed. The three-phase induction motor 3 is composed of a stator 5 around which a three-phase winding is wound, and a rotor 6 which is rotated by a magnetic field generated by the stator 5. The compression element 4 is connected to the shaft 13 of the rotor. The compression element 4 includes a crank portion 14 that rotates about a shaft 13 as a crankshaft 2, a roller 8 that rotates in the cylinder 7 by the crank portion 14, an upper bearing portion 10 and a lower bearing portion 11 that seal the opening of the cylinder 7.
It is composed of a cup muffler 12 attached to the upper bearing portion. A vane 9 is in contact with the roller 8 and divides the inside of the cylinder 7 into a high pressure chamber and a low pressure chamber. Balancers 16 and 17 are provided so as to dynamically or statically balance with the crank portion 14 of the crankshaft 2. A discharge pipe 18 is attached to the upper wall of the closed container 1.

FIG. 2 is a II-II sectional view of the compressor shown in FIG. In this figure, 19 is a discharge port, 20 is a suction port, and sections 21 and 22 in the cylinder 7 are a high pressure chamber and a low pressure chamber, respectively. The roller 8 rotates in the direction of the solid line arrow in FIG. 2, and the contact position at which the roller 8 contacts the cylinder 7 is displayed as a rotation angle of 360 degrees. In the state shown in FIG. 2, the rotation position of the roller 8, that is, the crankshaft 2 (shaft 13) is at a position of 180 degrees.

FIG. 3 is a sectional view of essential parts showing a state in which a position detector for detecting the rotational position of the compression element 4 is attached to the compressor shown in FIG. Since the compression element 4 rotates simultaneously with the rotor 6 via the crankshaft 2 (the shaft 13 of the rotor 6), the compression element 4 will actually be detected if the rotation angle of the rotor 6 is detected.
The rotation angle of can be detected. The position detector comprises a magnet 23 adhered to a disk 22 and a magnetic detector (Hall element) 24. The disk 22 is attached to the shaft 13 by bolts 25 so that the center of rotation is aligned. This magnet 23 and Hall element 24
With respect to the positional relationship with, the Hall element 24 detects magnetism and changes the output when the rotation angle shown in FIG. 2 is "0" degree. Therefore, the compression element 4 (rotor) can obtain an output for each rotation angle of "0". The hall element 24 is a bottomed pipe 27 from the discharge pipe 18 side of the closed container 1 of the compressor.
Is provided at the bottom of the pipe 27. The pipe 27 is welded to the closed container 1 so that the high pressure gas inside the compressor does not leak. Incidentally, reference numeral 26 is a balancer for correcting the weight balance generated by attaching the magnet 23.

FIG. 4 is a control circuit diagram for controlling the operation of the compressor shown in FIGS. In this figure, 27 to 29 are stator windings of the induction motor 5, which are star-connected. By energizing the stator windings 27 to 29 with three-phase alternating current, the magnet 23 attached to the disk 22 of the rotor 5 rotates. Therefore, the rotation of the rotor 5 (compression element) changes the output of the Hall element 24, and the position detection circuit 30 converts this change into a signal and outputs it to the control unit 31. Reference numerals 32 to 37 denote switching elements for ON / OFF operation, which are connected in a three-phase bridge shape, and the DC power supplied from the DC power supply 39 to the three-phase fixed windings 27 to 29 is the three-phase AC power. Converted to and output. These switching elements (transistor element, FE
32 to 37 semiconductor switching devices such as T devices and GTO devices
Each of them is connected to a diode that forms a circulating circuit for discharging accumulated charge or circulating current generated in the stator windings 27 to 29. The DC power supply 39 may be either AC power rectified and smoothed or DC power from a battery. The ON / OFF operation of the switching elements 32 to 37 is controlled by a signal from the control unit 31 via the base drive circuit 38. This controller mainly consists of CPU, RAM, ROM, I
Speed command circuit 40
The frequency is calculated based on the speed signal from, and the ON / OFF operation of the switching elements 32-37 is controlled so that the AC power of this frequency is supplied to the stator windings 27-29.

The switching signals given to the switching elements 32-37 will be described below. FIG. 5 is an explanatory diagram for obtaining a switching signal based on the PWM theory. In this figure, 50, 51, and 52 are sin waves, which are 120 ° out of phase with each other. Reference numeral 53 is a triangular wave, and the outputs obtained by comparing the magnitudes of these sin waves 50 to 52 and the triangular wave 53 are the switching signals of the switching elements 32, 34, 36. The switching signals of the switching elements 33, 35, 37 are switching elements.
The switching signals of the switching elements 32, 34 and 36 are inverted. By using these 6 kinds of switching signals, the stator windings 27 to 28 of the induction motor
It is possible to supply three-phase AC power having the same frequency as the waves 51 to 52. Therefore, when the frequencies of these sin waves 51 to 52 are changed, the frequency of the AC power supplied to the stator windings 27 to 29 can be changed at the same time. Also sin wave 50 ~ 52
The output of the AC power supplied to the stator lines 27 to 29 (the voltage when the sine wave is replaced) can be changed by changing the amplitude ratio of the triangular wave 53 and the triangular wave 53. The same applies to switching signals based on PAM theory.

The switching patterns of the switching elements 32 to 37 (ON / OFF of the switching elements) thus obtained are stored in the ROM of the control unit 31. CPU turns this pattern on / off
The signals are sequentially read and output to the switching elements 32-37. As a storage form in this ROM, the entire pattern or a part of the pattern may be stored and combined at the time of reading.
Further, the pattern may be decomposed and stored into the time when the ON signal is output and the time when the OFF signal is output, or the pattern for one cycle is decomposed at every predetermined phase angle and within the predetermined angle.
It may be stored after being decomposed into ON time and OFF time.

Further, the switching signal of the switching element may be calculated and obtained from the magnitude of the sin wave and the triangular wave at the designated phase angle. At this time, the specified phase angle is changed from 0 ° to 360 ° to obtain a switching signal for one cycle.

FIG. 6 is a diagram of three-phase AC voltage waveforms (equivalently replaced by sin waves) 61-63 obtained by turning ON / OFF the switching elements 32-37. Each voltage waveform has a phase of 12
It is offset by 0 °. In this control method, this output voltage is not always continuously supplied to the stator windings 27 to 28, but is synchronized with the signal from the position detector every time the rotation angle of the compression element becomes 0 °. The supply to the stator windings 27 to 29 is started from the position of the phase angle of 0 ° shown in FIG. Therefore, when the rotation angle of the compression element is 0 °, the voltage supplied to the stator winding is always the voltage when the phase angle is 0 ° shown in FIG. 67 is a waveform showing the relationship of the drive torque required when the compression element is driven. There is torque fluctuation during one rotation of the compression element, and this torque fluctuation causes vibration of the compressor. Therefore, the output of the induction motor is increased to match the drive torque. Since the rotation angle that requires a large torque during one rotation of the compression element is limited to around 200 °, the voltage applied to the stator winding is higher than usual when the compression element is at this rotation angle. do it. The output of the position detector matches the rotation angle of 0 ° of the compression element with the phase angle of 0 ° of the voltage pattern. Therefore, since the rotation angle of the compression element and the phase angle of the pattern of the voltage supplied to the stator winding match (ignoring the slip of the induction motor), the phase angles of the voltage waveforms 61 to 63 shown in FIG. This voltage fluctuation can be dealt with by increasing the voltage around 200 ° higher than usual.

The voltage waveforms shown at 64-66 in FIG. 6 take this torque fluctuation into consideration. That is, the voltage waveforms 64 to 66 increase the output torque of the motor by increasing the voltage and frequency (frequency within one cycle of this pattern, that is, the angular velocity of the phase) when the phase angle is around 200 °, and increasing the output torque of the motor. The output torque of the electric motor is reduced by reducing the voltage and the frequency when the angle is near 0 °. The voltage and frequency of the voltage pattern are set so that the output continuously changes between the phase angle where the output of the electric motor increases and the phase angle where the output decreases.

Therefore, these voltage waveforms 64-66 represent the stator windings 27-29.
The data for obtaining the switching signal supplied to the control unit 31 is stored in the ROM of the control unit 31. This voltage waveform 64-6
The amplitude of 6 is set according to the change of the actual driving torque of the compression element.

By supplying the switching signals thus obtained to the switching elements 32 to 37, the output of the induction motor is increased and the torque is increased to suppress the vibration of the compressor when the compression element requires a large torque. Can be controlled.

The switching signal for obtaining the voltage waveforms 61 to 63 shown in FIG. 6 is calculated if the frequency f, the output voltage V, and the phase Ph at which the switching signal is desired to be obtained are determined.
It should be noted that f is equal to the frequency signal given from the speed command circuit, and the basic value of V is determined based on the value of f such that V / f = constant value. The operating efficiency of the compressor is set to be good at each frequency. A switching signal for obtaining one cycle of AC power is output by changing the Ph value from 0 to 360 °. Actually, the value of Ph is advanced by ΔPh, and the same switching signal is maintained during this ΔPh. If the advance amount ΔPh of Ph is increased, the resolution in one cycle becomes worse, and if this value is made smaller, the resolution becomes better, but due to the relationship between the switching time that the switching element can respond and the processing capacity of the control unit 31, the The optimum value of ΔPh is set in advance.

FIG. 7 is a vibration waveform diagram in which the actual vibration state of the compressor is measured. This vibration waveform 71 is measured on the outer circumference of the compressor (first
Attach the acceleration sensor to the upper part of the stator 5)
It is a mangle obtained from the output of this sensor. The angle in this figure corresponds to the rotational position of the crank portion 14 shown in FIG. As you can see from this figure, the crank part 14 of the compression element
The amplitude of vibration increases at 130 ° and 270 °. Note that this section corresponds to the compression process in the compression element.

This vibration waveform 73 is when the AC power obtained by using the voltage waveform as shown by 73 is supplied to the stator winding of the compressor. It should be noted that since only the phases differ with respect to the other phases of the three phases, the description thereof is omitted. This voltage waveform 73 can be expressed by the following equation.

V = V ₀ sin θ (1) Therefore, it is sufficient to correct the equation (1) such that the driving torque increases between 130 ° and 270 °. That is, the drive torque is increased by increasing the amplitude of the equation (1) in this section.

The following example is a case where this correction is performed by approximation of a sin wave. 130 ° in the section where the driving torque needs to be increased
Since it is 270 °, a sin wave 72 having a peak at the center of this section, that is, at a position of 200 ° is set. This sin wave 72
The sin wave 73 has the same period (frequency) and its function can be expressed as V = A sin (θ + 110 °) (2). A is the amplitude of the sine wave 53. Therefore, in order to obtain the driving torque required by the compression element, the sine wave is a combination of equation (1) and equation (2), and is represented by the following equation (3).

V = (V ₀ sin θ) + (A sin (θ + 110 °)) = V ₀ (1 + A / V ₀ ) (sin θ + sin (θ + 110 °)) (3) A / V value is derived from 0.05 to 0.2 It is arbitrarily selected according to the frequency applied to the electric motor.

If a switching signal is obtained from the sine wave obtained by the equation (3) and the triangular wave shown in FIG. 5, a large driving torque can be obtained during the compression process of the compression element. At this time, the voltage applied to the induction motor (effective voltage after being converted into a sin wave) changes during one rotation of the compressor. Therefore, the condition of "V / f = constant value" described above is not satisfied, and the operating efficiency of the compressor decreases. In order to prevent this decrease in efficiency, the value of f may be changed. That is, during one rotation of the compressor, the value of f, that is, the frequency is changed according to the change in voltage. Similar to the voltage correction, this frequency change is also corrected so that the correction peak comes when the angle is 200 °. At this time, the correction on the plus side is made larger than the correction on the minus side.

In this embodiment, the correction is performed by the approximation of the sin wave, but it is not limited to this. For example, (sin) ² waves (in this case, used instead of the equation (1)) may be set according to the torque characteristic of the compression element.

FIG. 8 is a flow chart (fixing the output frequency) showing the operation when the correction is performed by using the equation (3).

First, in step S1, it is determined whether or not there is a 0 ° signal. That is, the rotation angle of the compression element becomes 0 °, and the position detector 24
It is determined whether or not there is a signal from. When there is a signal, the process proceeds to step S2, where θ = 0 and the rotation angle of the compression element is 0 ° and the phase angle of the output voltage pattern is 0 °.
If there is no signal in step S1, step S3
Proceed to. In this step S3, the value of θ is advanced by Δθ. The smaller the value of Δθ, the better the resolution of the output voltage to the stator winding. However, if it is too small, the switching speed of the switching element cannot catch up and control becomes impossible. In this embodiment, Δθ = 1.
It is not limited to this if the switching speed of the switching element catches up. Then, it progresses to step S4. In this step S4, the sine wave at the phase angle θ (Equation (3) above)
Calculate the value of the corrected sine wave). At this time, the value of θ is further corrected by ± according to θ. That is, the phase angle is advanced to increase or decrease the angular velocity (frequency) near this phase angle. Next, in step S5, the switching element is turned on / off based on the sin value and the triangular wave value obtained in step S4.
Get the OFF signal. In step S6, this ON / OFF signal is maintained for a predetermined time. This maintenance time × 360 (from Δθ = 1) is the time of one cycle, that is, the frequency of the AC power supplied to the induction motor.

In this flowchart, the ON / OFF signal was calculated for each cycle. However, this signal is calculated in advance, and the data for obtaining the calculated signal is stored in the ROM, and one cycle is performed in accordance with the 0 ° signal. The minutes may be continuously output.

FIG. 9 is a vibration waveform diagram showing changes in the vibration waveform when the torque control according to the above-mentioned flowchart is performed.
(Amplitude measurement is the same as in Fig. 7) In this figure, the section without torque control is when the output calculated using the waveform diagram 61 in Fig. 6 is supplied to the induction motor, and the section with torque control is shown. Then, the output calculated using the waveform diagram 64 of FIG. 6 is supplied to the induction motor. As can be seen from this figure, the vibration is smaller when the torque control is performed. Since the control is switched on and off during the operation of the compressor, a transient section occurs before the vibration becomes small.

FIG. 10 is a flow chart showing a use operation when the torque control described above is actually used. For example, in the case where a compressor is installed in an air conditioner and the rotation speed of the compressor is changed to obtain an appropriate compressor capacity, it can be obtained by comparing the room temperature and the set temperature of the room to be conditioned. The number of revolutions of the compressor is calculated from the data, and AC power having a frequency matching this number of revolutions is supplied to the compressor. In such a case, first, the operation start process of the compressor is performed in step S101. Next, in step S102, a compressor starting process is performed. When the frequency of the AC power applied to the compressor (calculation result from the above data) is set, if the compressor is suddenly started at this frequency, a large starting current may flow into the switching elements and destroy these switching elements. There is a low frequency fs (several hertz) to start the compressor start. During the frequency increasing process, when the condition of step S103 is not satisfied, the process proceeds to step S104. In this step S104, a waveform based on the usual PWM theory is supplied to the compressor to make the driving torque constant during one rotation of the compression element. That is, the AC power that is not subjected to the torque correction as described above is supplied to the compressor. When the frequency rises above f, the process proceeds to step S105,
It is determined whether or not the signal from the position detector is normally supplied. When the signal is not normally supplied, steps S106 and S107 are performed. That is, the frequency f
When f is not f ≧ f ′ _R , the value of f is set to f ′ _R and then the process proceeds to step S104 to perform the operation with the normal PWM waveform. When the position detection signal is detected in step S108, the process proceeds to step S108, and it is determined whether the set frequency f is f ≧ f _R. When this condition is satisfied, the routine proceeds to step S104, and the operation with the normal PWM waveform is performed as described above. When the condition of step S108 is not satisfied, the routine proceeds to step S109, and the torque control operation as described above is performed.

11 and 12 are explanatory diagrams showing the frequency range during operation according to the flowchart shown in FIG. FIG. 11 shows the time when the position detection signal is normally obtained, and FIG. 12 shows the time when the position detection signal is not normally obtained. A relationship of _{0 ≦ fs ≦ f T ≦ f} 'R ≦ fmax in these figures. That is, when the position detection signal is normally obtained, the torque control operation is performed at the set frequency between the frequency f _T and the frequency f _R, and when the set frequency is between the frequency f _R and the frequency fmax, the normal PWM waveform is used. Drive. The frequency f _'R and frequency fma when the position detection signal is not obtained properly
Normal PWM waveform operation is performed between x and x. Incidentally, the set frequency is 'when the _R below the set frequency f' f is increased to _R.

By performing the control as described above, when the signal from the position detector is abnormal, the operation is performed by the normal PWM waveform and the operation of the compressor is maintained.

FIG. 13 is a flowchart showing another embodiment of the flowchart of FIG. This flowchart and the
The difference from the flowchart shown in FIG. 10 is that after starting the compressor at the frequency fs in step S132, the process proceeds to step S133, and it is determined whether or not the position detection signal is normally supplied to start the torque control. It is in. That is, the torque control is started at the same time when the start of the compressor is completed.

(G) Effect of the Invention As described above, the present invention detects a signal corresponding to the rotation angle of the compression element and changes the drive torque of the induction motor during one rotation based on this signal. In the induction motor, when the signal corresponding to the rotation angle of the compression element is not detected, the driving torque during one rotation of the induction motor is kept constant and the operation of the compressor is continued.

Therefore, the torque control operation due to the abnormal signal disappears,
It is possible to prevent abnormal vibration of the compressor and damage to the connecting pipe due to this abnormal operation.

Further, when the signal corresponding to the rotation angle of the compression element is normally obtained, it is set to enable the supply of AC power having a frequency higher than the first frequency, and the signal corresponding to the rotation angle for compression is detected. If not, the AC power of a frequency higher than the third frequency (first frequency <third frequency <second frequency) is enabled, and the drive torque during one rotation of the induction motor is constant. By doing so, it is possible to increase the set frequency to a frequency at which vibration does not occur so much even when torque control is not performed during abnormal conditions, and to maintain low vibration operation during abnormal conditions.

[Brief description of drawings]

FIG. 1 is a sectional view of a compressor using the control system of the present invention, FIG. 2 is a sectional view taken along the line II-II of the compressor shown in FIG. 1, and FIG. 3 is located at the compressor shown in FIG. FIG. 4 is a cross-sectional view of a main part showing a state in which a detector is attached, FIG. 4 is a control circuit diagram of the compressor shown in FIG. 1, FIG. 5 is an explanatory diagram showing ON / OFF signals of switching elements, and FIG. Voltage waveform diagram of three-phase AC obtained by turning ON / OFF the switching element, Fig. 7 is a vibration waveform diagram in which the actual vibration state of the compressor is measured, and Fig. 8 is a flow chart showing the generation of ON / OFF signals. FIG. 9 is a vibration waveform diagram when the control system of the present invention is used, FIG. 10 is a flow chart showing a use operation when torque control is actually used, and FIG. 11 is a frequency when a position detection signal is normally obtained. 12 is an explanatory view showing the frequency range, FIG. 12 is an explanatory view showing the frequency range when the position detection signal is not normally obtained, and FIG. 7 is a flowchart showing another embodiment using torque control. 1 ... Compressor, 3 ... Induction motor, 4 ... Compression element, 6
...... Rotor, 23 …… Magnet, 24 …… Hall element, 27
〜29 …… stator winding, 31 …… control unit, 32-37 …… switching element.

Claims (2)

(57) [Claims] Claim: What is claimed is: 1. An induction motor in which an alternating-current power having a frequency arbitrarily set within a predetermined frequency range is supplied to control the rotation speed, and a compression element rotationally driven by a rotor of the induction motor. In an induction motor for a compressor, which is housed in the same case and configured to change the drive torque during one rotation of the induction motor based on a signal detected corresponding to the rotation angle of the compression element, A method for controlling an induction motor for a compressor, wherein a drive torque during one rotation of the induction motor is made constant when a signal corresponding to the rotation angle is not detected. 2. An induction motor in which a rotational frequency is controlled by supplying AC power having a frequency arbitrarily set between a predetermined first frequency and a second frequency higher than the predetermined frequency,
A compression element that is rotationally driven by the rotor of this induction motor is housed in the same case, and the drive torque during one rotation of the induction motor is based on the signal detected corresponding to the rotation angle of the compression element. In the induction motor for a compressor configured to change, when a signal corresponding to the rotation angle of the compression element is detected, it is set to enable supply of AC power having a frequency equal to or higher than a first frequency, and the compression is performed. When a signal corresponding to the rotation angle of the element is not detected, supply of AC power having a frequency equal to or higher than the third frequency series (having a relationship of first frequency series <third frequency <second frequency) And a drive torque during one revolution of the induction motor are made constant, and a method for controlling an induction motor for a compressor.