JP2789658B2 - Drive device for variable reluctance motor - Google Patents

Description

Description: Object of the Invention (Industrial Application Field) The present invention relates to a variable reluctance motor driving apparatus which appropriately excites a multi-phase excitation winding of a variable reluctance motor according to a rotation angle of a rotor thereof. More particularly, the present invention relates to a variable reluctance motor drive device that modulates an exciting current flowing in an exciting winding to control a torque generated in a rotor to a predetermined value.

(Prior art) Conventionally, as a driving device of a variable reluctance motor,
The following technologies are known.

In order to drive the variable reluctance motor, the excitation windings of each phase are sequentially excited for an excitation period corresponding to the rotation angle of the rotor. Further, in order to control the output torque to a predetermined value, it is necessary to perform a so-called current pattern control for controlling the excitation current flowing through the excitation winding to a predetermined pattern during the excitation period. Therefore, conventionally, FIG.
Excitation winding of each phase of variable reluctance motor as shown in
Transistors Tr1 and Tr as switching elements at both ends of SL
2, and a switching signal obtained by PWM-controlling a desired current pattern as shown in FIG. 4 (B) is input thereto. Also, in FIG. 1A, each transistor Tr1, Tr
Diodes D1 and D2 connected in parallel with 2 and the exciting coil SL
Are the transistors Tr1 and Tr2
Are for regenerating the electromagnetic energy stored in the exciting coil SL to the power supply when both are in the cutoff state.

By the above-described variable reluctance motor drive device, the effective value of the exciting current passed through the exciting winding SL of the variable reluctance motor matches the desired current pattern at every moment, and the output torque can be freely controlled. Becomes

(Problems to be Solved by the Invention) However, when a variable reluctance motor is actually driven by a conventional driving device, a problem that loud noise is generated from the variable reluctance motor has not been solved yet. There is a problem that is limited.

Originally, the variable reluctance motor rotates by the Maxwell stress acting on the rotor in a substantially radial direction. Therefore, compared to a rotating machine that generates a substantially circumferential force on a rotor by a rotating magnetic field, the operating sound during rotation is loud and is counted as one of the disadvantages.

In addition, in order to make the effective value of the exciting current coincide with a predetermined current pattern, the exciting current of the exciting winding SL repeats conduction and interruption at a large change rate as shown in FIG. 4 (B). Therefore, mechanical vibration is induced not only in the rotor but also in the exciting winding SL and the stator core around which the exciting winding SL is wound, so that so-called electromagnetic noise is generated. In particular, when the variable reluctance motor rotates at a low speed, the electromagnetic noise increases due to the following reasons. In the variable reluctance motor, the following relational expression holds between the power supply voltage v and the exciting current i of the exciting winding SL.

Here, L is the inductance [H] of the exciting coil SL,
θ is the rotation angle [rad] of the rotor, and ω is the rotation angular velocity [rad / sec] of the rotor. That is, the first term on the right side shows the back electromotive force based on the change in the current, and the second term on the right side shows the back electromotive force based on the change in the inductance L. As is apparent from this equation, at low speed rotation, the back electromotive force based on the change in the inductance L is small, and the exciting current i flowing through the exciting winding SL rises instantaneously when both the transistors Tr1 and Tr2 become conductive, and becomes large. It can be seen that the rate of change is shown. When both the transistors Tr1 and Tr2 are turned off, the capacitance C of the smoothing capacitor CC on the power supply side acts as a resonance circuit with respect to the inductance L of the exciting winding SL, and is stored in the exciting winding SL. The instantaneously absorbed electromagnetic energy is instantaneously absorbed as electrostatic energy of the smoothing capacitor CC, and the falling characteristic of the exciting current i becomes sharp.

For this reason, at low speed, the ripple of the exciting current i becomes extremely large, and the generation of electromagnetic noise increases. In general, electromagnetic noise can be ignored in a rotating machine at high speeds because wind noise and mechanical noise from bearings are large.However, at low speeds, electromagnetic noise is a problem because there is little other noise. Since a reluctance motor generates a large electromagnetic noise, it is strongly desired to solve this problem.

The present invention has been made to solve the above problems,
A drive device for a variable reluctance motor that performs a current pattern control that can adjust the generated torque of the variable reluctance motor to a desired value and that does not generate noise such as electromagnetic noise even at a low speed rotation and has a small operation sound. It is intended to provide.

Means for Solving the Problems To solve the above problems, the means according to the present invention is connected in series to both ends of an exciting winding of a variable reluctance motor, and is connected to the exciting winding and a power source based on a switching signal. A switching element that cuts off the connection with, or permits excitation by energization in only one direction, and one of the switching elements connected in series at both ends of the excitation winding and one of the switching elements that are connected in parallel to the excitation winding. A diode having conductivity in the direction opposite to the current flowing direction of the switching element; and the other of the switching elements connected in series to both ends of the excitation winding and the excitation winding connected in parallel to the other excitation element. A diode having conductivity in a direction opposite to the direction, and an excitation period of the excitation winding according to a rotation angle of a rotor of the variable reluctance motor. And controlling the operation of switching elements provided at both ends of the exciting winding during the exciting period to adjust the exciting current of the exciting winding, and to set the rotating torque generated in the rotor to a predetermined value. A timing control circuit, the drive device for a variable reluctance motor comprising: wherein the excitation timing control circuit controls operation of a switching element during the excitation period, and when the rotation speed of the rotor is equal to or higher than a predetermined value, The switching elements provided at both ends of the excitation winding are simultaneously turned off or turned on, and when the rotation speed of the rotor is less than a predetermined value, one of the switching elements provided at both ends of the excitation winding is always turned on. The gist is that the other switching element is appropriately turned off or turned on.

(Operation) The excitation timing control circuit in the drive device of the present invention has an operation of appropriately changing the switching timing of the switching element according to the rotation speed of the rotor.

That is, when the rotation speed of the rotor is equal to or higher than the predetermined value, the control of the operation of the switching elements connected in series to both ends of the excitation winding during the excitation period is simultaneously cut off or turned on. For this reason, the exciting winding is in the excited state when both the switching elements are in the conductive state, and is in the regenerative state when both are in the cutoff state.

Further, when the rotation speed of the rotor is less than a predetermined value,
One switching element connected in series to both ends of the exciting winding is made conductive during the excitation period, and the other is appropriately cut off or made conductive. For this reason, the exciting winding is in an excited state when the other switching element is in a conductive state, and is in a reflux state via one of the switching elements in a conductive state when the other switching element is in a cutoff state. Therefore, at the time of low-speed rotation, the electromagnetic energy accumulated in the exciting winding is gradually consumed by the resistance in the return path, and the rate of change of the current is kept small.

Hereinafter, the present invention will be described more specifically with reference to examples.

(Embodiment) FIG. 1 is a block diagram showing a circuit configuration of a driving device of a variable reluctance motor 10 according to an embodiment. For simplicity, the control system shown in the figure shows only a part that controls the excitation current of the one-phase excitation winding 12, and the control system describes only the current feedback loop, and other position and velocity feedback The loop is omitted. So in practice,
The control system shown in FIG. 1 with a position and speed feedback loop added is provided by the number corresponding to the number of phases of the exciting windings of the variable reluctance motor 10.

As illustrated, transistors 14 and 16 are connected in series as switching elements between both ends of the exciting winding 12 of the variable reluctance motor 10 and the power supply. A diode 18 is provided in parallel with the exciting winding 12 and the transistor 14,
A diode 20 is connected in parallel with the exciting winding 12 and the transistor 16. These transistors 14, 16 and diode 1
The current supplied to the exciting winding 12 is controlled by 8, 20.In order to detect what kind of exciting current is actually flowing, a current detection is applied to the connection line between the transistor 14 and the exciting winding 12. The coil 22 is mounted. Further, in order to detect how the variable reluctance motor 10 is actually rotated by such an exciting current, the output shaft of the variable reluctance motor 10 has an encoder 24 for detecting a rotation direction and a rotation angle, and a rotor. And a pole pulse sensor 26 for detecting a phase relationship between the stator and the stator.

In order to control the conduction state of the transistors 14 and 16 at a predetermined timing, the base of each transistor is connected to the transistor drive circuits 30 and 32. Here, when a timing signal described later is input to the transistor drive circuits 30 and 32, the transistor 1
It generates a base signal that makes the 4 and 16 conductive, and is composed of a TTL circuit or the like.

In this embodiment, the following various circuits are used as circuits for generating the timing signal.

First, the current pattern generation circuit 40 receives the torque command T and the positive and negative signals TS of the torque from a speed control system (not shown), and the current rotation state of the variable reluctance motor 10 is controlled by the encoder 24 and the pole pulse sensor 26. Detect from output signal. Then, based on the information, a current pattern (see FIG. 2 (a)) required to generate a target torque with a phase adapted to the angular position of the rotor is determined, and a predetermined rotation of the rotor is determined. The current pattern signal is output in synchronization with the angle.

In order to pass the exciting current conforming to the current pattern to the exciting winding 12, it is necessary to perform PWM control on the connection between the voltage source having the constant voltage Vp and the exciting winding 12. Therefore, the current pattern signal output from the current pattern generation circuit 40 is PW
Input to the M circuit 42. At this time, in order to improve the control accuracy of the excitation current, the current pattern signal and the current detection coil 22 are used.
And then compares the result with the proportional / integral controller (PI
After the responsiveness is improved through the controller 44, the signal is input to the intended PWM circuit 42. With this PWM circuit 42,
As shown in FIG. 2 (a), a comparison is made between the target current pattern of the excitation current and the triangular wave carrier for PWM. A signal is obtained. The conduction timing signal thus created is input to the above-described transistor drive circuit 32 for the transistor 16 and a signal selection circuit 46 described below.

On the other hand, in another system different from the conduction timing signal,
A firing timing signal, which is another timing signal, is created. The circuit that generates this firing timing signal is the firing timing generating circuit 48 shown in the figure. The ignition timing generation circuit 48 receives the detection signal of the encoder 24, the pole pulse sensor 26, and the positive / negative signal TS of the target torque as shown in the figure, and generates the ignition timing signal suitable for the rotation angle of the rotor. I do. The firing timing signal is a pulse signal that brings the transistor 14 into the conductive state during the period with the same phase as the conductive timing signal as shown in FIG. 2 (c). Then, this firing timing signal is also input to the signal selection circuit 46 in the same manner as the conduction timing signal.

In the signal selection circuit 46, the conduction timing signal and the ignition timing signal, which are the two types of timing signals having the above relationship, are input, and one of the timing signals is selected based on the detection signal of the encoder 24 to be used for the transistor 14. To the transistor drive circuit 30 of FIG. The selection is based on the rotation speed ω of the output shaft detected from the output signal of the encoder 24.
r is compared with a predetermined comparison reference speed ωc, and when ωr ≧ ωc, a conduction timing signal is selected and output to the transistor drive circuit 30, and ωr <
When it is ωc, a firing timing signal is output. The comparison reference speed ωc is determined in consideration of the triangular wave carrier frequency of the PWM circuit 42, the time constant of the exciting winding 12, and the like.

According to the variable reluctance motor driving apparatus of the present embodiment configured as described above, the following exciting current flows during the exciting period of the exciting winding 12, and noise during low-speed rotation can be reduced.

That is, the rotation speed ωr of the output shaft becomes the comparison reference speed ωc
In the case of the low-speed rotation of less than, the ignition timing signal shown in FIG. 2C is input to the transistor drive circuit 30 by the operation of the signal selection circuit 46. The conduction timing signal shown in FIG. 2B is input to one of the transistor driving circuits 32. Therefore, during the period when both of these timing signals make the transistors 14 and 16 conductive, “power → transistor 14 → exciting winding 12 → transistor 16”
A closed circuit of "ground" is formed, an exciting current shown by a dotted line in FIG. 3 flows, and magnetic energy is accumulated in the exciting winding 12.

In addition, during a period in which the transistor 16 that operates based on the conduction timing signal is turned off, “transistor 14 → excitation winding 1
A closed circuit of “2 → diode 18 → transistor 14” is formed, and a current shown by a chain line in FIG. 3 flows. That is,
During this period, the electromagnetic energy stored in the exciting winding 12 returns through the return path, and is gradually reduced to thermal energy by the resistance of the transistor 14 and the diode 18 and decreases.

Then, after the above-described two modes are repeated during the excitation period, the excitation of the excitation winding 12 is terminated, and both timing signals command a transistor cutoff state, the magnetic energy stored in the excitation winding 12 becomes As shown by a two-dot chain line in FIG. 3, "diode 20 → excitation winding 12 → diode 1
It is regenerated to the power supply through the route of 8 ". At this time, the electromagnetic energy of the exciting winding 12 is instantaneously converted into electrostatic energy by the resonance action of the inductance component of the exciting winding 12 and a capacitance component such as a smoothing capacitor connected to the power supply system. Decreases quickly.

Therefore, if the exciting current flowing through the exciting winding 12 at this time is illustrated, as shown in FIG. 2D, the rate of change at the time of the current falling during the exciting period is small, and the waveform has a small amount of ripple. Therefore, the electromagnetic energy stored in the excitation winding 12 becomes stable with a small rate of change over time, and the electromagnetic noise is reduced. Further, since the torque generated in the rotor is stabilized, the generation of other mechanical sounds is also suppressed, and the operation noise of the variable reluctance motor 10 is extremely low.

When the rotation speed ωr of the output shaft is equal to or higher than the comparison reference speed ωc, the conduction timing signal is input to the transistor driving circuit 30 by the operation of the signal selection circuit 46, and both the transistors 14 and 16 are driven by the conduction timing signal. .
That is, the same control as that of the conventional variable reluctance motor driving device can be executed.

In the above description, the triangular wave carrier frequency of the PWM circuit 42 is set to be very low to make the waveform of the exciting current easy to understand, and the waveform is rough. Actually, since the triangular wave carrier frequency of the PWM circuit 42 can be increased to several tens of times as shown in the figure, the waveform of the exciting current shown in FIG. It will be more effective.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment at all, and may be embodied in various forms without departing from the gist thereof. For example, in the above embodiment, when the rotation speed ωr of the output shaft is lower than the comparison reference speed ωc, the transistor 14 is operated based on the ignition timing signal to create the reflux mode shown by the dashed line in FIG. For this reason, the fall characteristic of the exciting current becomes gentle, but the effective value of the exciting current becomes larger than the target current pattern created by the current pattern generating circuit 40. Therefore, when the ignition timing signal is selected by the signal selection circuit 46,
Various improvements may be made, such as reducing the current pattern created by the current pattern generation circuit 40 in advance.

Further, as is clear from FIG. 1, the transistor whose timing signal can be switched by the signal selection circuit 46 is not limited to the transistor 14, but may be the transistor 16.

Further, in order to properly adjust the falling characteristic of the exciting current in the reflux mode shown by the one-dot chain line in FIG.
A resistor may be connected in series, or a plurality of diodes may be connected in series to change the electric resistance value of the reflux circuit.

Effects of the Invention As described above in detail with reference to the embodiments, the variable reluctance motor driving device of the present invention always keeps one switching element directly connected to both ends of the exciting winding at the time of low-speed rotation of the rotor, In this case, the excitation state of the excitation winding is controlled by appropriately switching off or conducting the switching element.

Therefore, the ripple of the exciting current can be reduced during the low-speed rotation of the variable reluctance motor, and the electromagnetic noise generated from the exciting winding and the stator core can be efficiently reduced.

Further, since the torque generated in the rotor is stabilized, radial vibration generated in the rotor can be prevented, mechanical noise can be suppressed, and the operating noise of the variable reluctance motor can be extremely reduced.

[Brief description of the drawings]

FIG. 1 is an electric circuit block diagram of a variable reluctance motor driving apparatus according to an embodiment of the present invention, FIG. 2 is a current waveform of each part in the embodiment, and FIG. 3 flows through an exciting winding in the embodiment. 4A and 4B are explanatory diagrams of an electric circuit of a conventional variable reluctance motor driving device and current waveforms of respective parts. 10 Variable reluctance motor, 12 Excitation winding 14, 16 Transistor 18, 20 Diode, 22 Current detection coil 24 Encoder, 26 Pole pulse sensor 30, 32 Transistor drive Circuit 40: Current pattern generation circuit, 42: PWM circuit 44: Proportional / integral controller 46: Signal selection circuit 48: Firing timing generation circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02P 5/05 H02P 7/05

Claims (1)

(57) [Claims] A switching element connected in series to both ends of an exciting winding of a variable reluctance motor, for disconnecting the exciting winding and a power supply based on a switching signal, or for permitting excitation by energization in only one direction; A diode connected in parallel to one of the switching elements connected in series to both ends of the excitation winding and the excitation winding, and having a conductivity in a direction opposite to a conduction direction of the one switching element; A diode connected in parallel to the other of the switching elements connected in series to the excitation winding and having conductivity in a direction opposite to a current-carrying direction of the other switching element; and a rotation angle of a rotor of the variable reluctance motor. The excitation period of the excitation winding is determined in accordance with the following formula, and a switch provided at both ends of the excitation winding during the excitation period is determined. An excitation timing control circuit that controls the operation of an element to adjust an excitation current of the excitation winding and sets a rotation torque generated in the rotor to a predetermined value.A driving device for a variable reluctance motor, comprising: The control circuit controls the operation of the switching element during the excitation period, and when the rotation speed of the rotor is equal to or higher than a predetermined value, simultaneously sets the switching elements provided at both ends of the excitation winding to a cutoff or conduction state, When the rotation speed of the rotor is less than a predetermined value, one of the switching elements provided at both ends of the excitation winding is always in a conductive state, and the other switching element is appropriately turned off or in a conductive state. Drive device for variable reluctance motor.