JP2002084792A - Stepping motor drive method - Google Patents

Abstract

(57) [Summary] In a stepping motor driving method in which each winding set of a stepping motor having a plurality of winding sets is excited in a predetermined procedure according to a stepping pulse, in order to keep a driving torque constant. The configuration does not use a complicated and costly multi-voltage power supply. A high-side switch element and a low-side switch element have a current control function as well as an excitation step switching. That is, the power supply state of the power supply point is changed so that each winding current of the motor changes in a sinusoidal manner, and two or more power supply states separated by more than one full step in electrical angle are repeated. The configuration changes in accordance with the stepping pulse.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque control method for driving a stepping motor.

[0002]

2. Description of the Related Art Torque control in driving a five-phase stepping motor is performed by drive current control. Conventionally, drive current control is performed by converting a power supply voltage of a motor in the following manner.

FIG. 11 shows a conventional example of a five-phase stepping motor drive circuit. The switching element Ql, which is a component of the current control unit 1, is a P-type FET (field effect transistor), and the high-side switching elements Pl to P5 that supply a drive excitation current to the stepping motor 6 are P-type FETs. The low-side switch elements N1 to N5 are N-type FETs.

[0004] The + side of the motor power supply Vm is connected to the source of the switch element Ql, and one side is grounded. A signal SQl which is an output of the current control signal generator 11 is provided at the gate of the switch element Ql.
And the drain is connected to one end of the coil Ll. A capacitor Cl is connected to the other end of the coil Ll,
The other end of the capacitor C1 is connected to the sources of the switching elements N1 to N5. The + side of the condenser Cl is commonly connected to the sources of the switch elements P1 to P5. One side of the condenser Cl is commonly connected to the sources of the switch elements N1 to N5. The voltage between both ends of the condenser Cl is defined as VCl.
The drains of the switch elements Pl to P5 are connected to the switch elements Nl to
N5 are connected to the respective drains, and are connected to the power supply points A to O of the stepping motor.

[0005] The stepping motor 6 has five sets of excitation windings A, B,
It has C, D, and E, and the arrangement on the stator is A → B → C → D → E →
The windings A to E are annularly connected as shown below in the order of A. One end of the winding D and one end of the winding A are connected to form a feeding point A. The other end of the winding A and one end of the winding C are connected to form a feeding point A. The other end of the winding C and one end of the winding E are connected to form a feeding point c. The other end of the winding E and one end of the winding B are connected to form a feeding point d. The other end of the winding B and the other end of the winding D are connected to form a feeding point e.

[0006] The feeding point A is connected to the drains of the switching elements Pl and Nl.
To P5 and the drains of N2 to N5. The sources of the switch elements N1 to N5 are commonly connected to one end of the resistor R1 and are input to the current control signal generator 11. The other end of the resistor R1 is grounded. Resistance R1
Is the current flowing through i, and the voltage at both ends is VR1. The voltage Vref is input to the current control signal generator 11.

[0007] The excitation signal generator 2 receives a signal DIR and a signal MCLK. The signals SP10 to SP50 are output from the excitation signal generation unit 2, and are connected to the gates of the switch elements P1 to P5 via the voltage conversion unit 3 as signals SP1 to SP5, respectively. The voltage converter 3 receives the positive voltage of the capacitor Cl.
The signals SN1 to SN5 are output from the excitation signal generating unit 2 and connected to the gates of the switch elements N1 to N5.

[0008] [Current control operation] The current control signal generation unit 11
Voltage Vref corresponding to control target value of motor drive total current i
Is input, and the value is set according to the desired torque. The switching elements Pl to P5 and Nl are generated by the excitation signal generation unit 2.
N5 apply a voltage to the feeding points A to O in a predetermined order, whereby a current flows through the motor winding, and the total current i is the resistance Rl
To generate a voltage VRl. The VRl and the Vref are compared by the current control signal generator 11, and a signal SQl is generated based on the result. The signal SQl causes the source and drain of the switch element Ql to repeat the ON (conducting) state and the OFF (cutoff) state, thereby adjusting the current supplied from the motor drive power supply Vm to the coil L1.

When the total current i is smaller than the target current, VRl <Vref
The signal SQl is changed so that the ON period of the switch element Ql is lengthened, and as a result, VCl increases and the total current i increases. When the total current i is larger than the target current, VRl> Vref, and the signal SQl is changed so that the ON period of the switching element Ql is shortened. As a result, VCl falls and the total current i decreases.
In this way, the total current i, ie, the drive current, is controlled to the target value by changing VCl, ie, the voltage applied to the motor.

[Rotary driving operation] The excitation signal generating unit 2 includes a signal DIR for determining a rotational direction and a signal M for determining a rotational speed as control signals for rotationally driving the stepping motor 6.
CLK is input. The excitation signal generation unit 2 generates control signals SP10 to 50 (SPl to 5) and SNl to 5 based on these two signals, and by using them, the switch element groups Pl to 5 and Nl to 5
Are operated in a predetermined procedure to excite the winding, and a rotor (not shown) is rotationally driven in a rotational direction according to the signal DIR at a speed according to the signal MCLK.

Each of the feeding points A to O is turned on (conducted) and turned off (cut off) with the + side of the capacitor Cl by the high-side switching elements P1 to P5, and the capacitors are turned on and off by the low-side switching elements N1 to N5. On / off with the minus side of Cl is performed.

In this embodiment, the operation of the P-type FETs of the switch elements P1 to P5 is a simple operation as described below for convenience of explanation. If the gate voltage is "sufficiently" lower than the source voltage, the source-drain is turned on. If there is no difference between the gate voltage and the source voltage, the source and the drain are turned off. However, the source voltage, that is, "VCl + VR"
l ”changes, the output signals PSPl to
The output signals SPl to SP5 of the voltage conversion unit 3 generated based on PSP5
Is converted with reference to “VCl + VRl”. In this example, the voltage is “(VCl + VRl) −10 volts” when on, and “VC” when off.
l + VRl ".

The N-type FETs of the switch elements N1 to N5 similarly operate as follows. If the gate voltage is "sufficiently" higher than the source voltage, the source-drain is turned on. If there is no difference between the gate voltage and the source voltage, the source and the drain are turned off. Voltage VRl across resistor Rl
Is sufficiently smaller than VCl and can be neglected. Therefore, the output signals SN1 to SN5 of the excitation signal generator 2 are set to 10 volts when on and 0 volt when off in this example.

[Excitation Drive Operation] FIG. 12 shows a four-phase excitation drive of the five-phase stepping motor. The feeding points A to A are indicated by vertices of a pentagon in FIG. 12, and the energized state is indicated by the following symbols. When the high-side switch elements Pl to P5 are on and the low-side switch elements Nl to N5 are off and are connected to the positive side of the capacitor Cl and almost VCl is given as a voltage, a circle is given. When the switch elements P1 to P5 are off and the switch elements N1 to N5 are on and connected to the minus side of the capacitor Cl and substantially zero volt is given as a voltage, ● is given. The direction of the current is positive in the clockwise direction in the figure (clockwise).

[0015] The excitation step proceeds in synchronization with the signal MCLK. signal
DIR is a signal that determines the direction of rotation. For example, when the signal DIR is "H"
, The excitation step proceeds in the order of (1) (2) (3)... (10) (1). Signal DIR is “L”
Then (1) (10) (9) ... (1) (10) ..., the direction of rotation is opposite to the case of "H", but both differ only in the direction of the excitation step, and power is supplied at each excitation step. Since the states are the same, only the case of "H" will be described below.

In the excitation step (1), (1a) the feed point A / I / O is connected to the + side,
(1b) Feeding point a is connected to the + side, and feeding point a, u, d
The state in which the o is connected to the-side is alternately repeated at a rate of 50% in time and sufficiently short in comparison with the cycle of the signal MCLK.

When the excitation step proceeds to (2) in synchronization with the rise of the signal MCLK, (2a) the feeding point A / I / O is connected to the + side, and the feeding point D is connected to one side. State (2b) The feed points A and A are connected to the + side, and the feed points U and D
The state in which the o is connected to the-side is alternately repeated at a rate of 50% in time and sufficiently short in comparison with the cycle of the signal MCLK. Hereinafter, similarly, the process proceeds to the excitation step (10) and returns to the step (1) again.

[0018] This excitation method has advantages in that a voltage is applied to both ends of the winding in each step, the current changes quickly, and the motor can be driven to rotate at a higher speed.

FIG. 13 shows an electric vector, that is, a torque vector in the excitation step. Depending on the direction of the winding currents of the windings A to E, the directions of the vectors generated independently by the windings are reversed, so that the total number of vectors generated by the windings alone becomes 10, and the angle between the adjacent vectors, that is, Electrical angle is 360
Degree divided by 10 = 36 degrees.

In the excitation step (1a), a current flows in the winding B in the negative direction, and a current flows in the winding C in the positive direction. In the excitation step (1b), a current flows through the winding A in the positive direction, and a current flows through the winding D in the negative direction. Since (1a) and (1b) have the same ratio,
The magnitude of the torque vector generated by each winding in this state is 1
Then, the combined vector of step (1) is Tl == TA−T
B + TC-TD, and the size | Tl | ≒ 3.08. Similarly, the resultant vector T2 of the excitation step (2) is as shown in FIG. 13, and the electrical angle changes by 36 degrees as the excitation step advances. The above is the so-called full-step drive in which the number of excitation phases is always four, but the micro-step drive in which the unit of the rotation angle (electrical angle) is made finer than the full step will be described below.

FIG. 14 shows the excitation steps of the four-divided microstep in a time series. Let t be the excitation step cycle. In the following, the step position indicates a full step position by an integer part, a division number by a denominator of a fraction, and a micro step position by a numerator. In step (1), steps (1a) and (1b) are repeated at an equal rate, that is, at a time of 4t / 8. In step (1 1/4), step (1)
And (2) repeat at a ratio of 3: 1. That is, (1a) is 3t /
8, (2a) is repeated at t / 8, (1b) is repeated at 3t / 8, and (2b) is repeated at time of t / 8. In step (12/4), steps (1) and (2) are repeated at a ratio of 2: 2. That is, (1a) (2a) (1
b) (2b) is repeated at a time of 2t / 8 each. Hereinafter, the process is repeated as shown in the figure. In step (2), steps (2a) and (2
b) only, each of which is repeated at a time of 4t / 8.

At this time, the vector between steps (1) and (2) is internally divided into four as shown in FIG. That is, the composite vector Tl of the step (1 1/4)
In l / 4, steps (1) and (2) are repeated at a ratio of 3: 1, so that the vector is internally divided into 1: 3. Similarly, the vector of the subsequent microstep advances the internal dividing point between the vectors of the full step as shown in FIG.
The rotation angle (electrical angle) per cycle is subdivided into a quarter of the full step. However, as is clear from FIG. 15, the generated torque has a maximum value of about 3.08 at the full step position and a minimum value of about 2.93 at the half step position which is the middle point, and the torque varies depending on the position. As the division number is subdivided, the electrical angle per one step of the step pulse is also subdivided, and the stepwise rotation of the stepping motor can be approximated to a pseudo continuous rotation state. However, even if the number of divisions is subdivided, the above-described torque fluctuation remains unchanged. In this example, the switching elements are all configured using FETs, but there are also those using a bipolar transistor.

[0023]

In the prior art, the high-side voltage is changed relatively to the low-side voltage by the current control unit so that a desired driving torque is obtained. It is necessary to use components having a sufficient withstand voltage and a large current capacity for the switch element Ql, the coil Ll, the capacitor Cl, and the like, which are components of the current control unit, and the cost of the unit becomes extremely high. For example, in the case of a drive circuit having a drive power supply voltage of 40 volts and a motor drive current of a maximum of 3 amps, the cost of this part may occupy almost half of the entire drive circuit. In the case where the drive current, that is, the generated torque is controlled to be constant, the required energy increases as the rotation speed increases. That is, in the conventional example, the higher the rotation speed, the higher the high-side voltage, and the lower the rotation speed, the lower the high-side voltage.

Here, looking at an application example of the document reading apparatus which is a component of the copying machine, after a reading period, a reading member (such as a reading sensor) is driven at a high speed to return to a reference position at a high speed. Between them, the high-side voltage is the highest.
On the other hand, in the reading period, the rotation speed is as slow as several tenths to several tenths as compared with the high-speed rotation period, so that the high-side voltage is very low. Therefore, a state in which a high withstand voltage and a large current capacity are required is for a short period of time, resulting in a very wasteful configuration and high cost in terms of circuit use efficiency.

Further, as described above, if the driving speed is low, the high-side voltage also decreases, and the gate signal voltage when the high-side switch element is turned on approaches the low-side voltage or becomes lower than the low-side voltage accordingly. You need to lower the voltage. For this reason, for example, the voltage conversion unit 3 in the conventional example must have a complicated configuration using a multi-voltage power supply, so that the entire driving circuit becomes more complicated and the overall cost becomes higher.

[0026]

In order to solve the above-mentioned problems, the high-side switch element and the low-side switch element are provided with a current control function as well as an excitation step switching. That is, the power supply state of the power supply point is changed so that each winding current of the motor changes in a sinusoidal manner, and two or more power supply states separated by more than one full step in electrical angle are repeated. The configuration changes in accordance with the stepping pulse.

[0027]

FIG. 1 shows an embodiment of the present invention. Fig. 11 of the conventional example
The same reference numerals are given to the components corresponding to, and the description of the parts having the same configuration is omitted. The + side of the motor power supply Vm is the + side of the condenser Cl and the high side switch element Pl.
Connected directly to ~ 5 sources. Offset signal generator 1
In 01, the negative voltage of the capacitor Cl and the voltage Vref corresponding to the motor drive torque target value are input, and the signal OFS is output. The excitation signal generator 2A also receives the signal OFS in addition to the signal MCLK and the signal DIR, and the switch element control signals SPl to SP5.
And SNl to 5 are output. The signal SPl is supplied to the voltage converter 3A.
~ 5 and Vm which is the high side voltage are input and the signal SPl ~
5 is output.

[Excitation drive operation] Although the details will be described later, the step in which one of the five feeding points is connected to the high side or the low side at a time rate of 100% corresponds to the full step of the conventional example. Let the step state be represented by an integer corresponding to the example. Hereinafter, it is assumed that the value corresponding to the number of microstep divisions in the conventional example is sufficiently large, and that changes between full steps can be handled continuously.

FIG. 2 shows the PWM state of the feeding point, the feeding state of the winding, the winding current, and the feeding current. The horizontal axis is the excitation step, which is approximately
Steps for the second rotation are shown as step 11, and step 10 for the second rotation is shown as step 20 to step 21.

FIG. 2 (a) shows the PWM states of the five power supply points A to E by "high-side ON time ratio / low-side ON time ratio". Here, only the waveform of the thin line will be described, and the thick line will be described later. For example, looking at the feeding point a, in Step 1, the connection is made to the + side with a time ratio of 100% (+1.0), and in Step 6, the connection is made to the − side with a time ratio of 100% (−1.0).
1.0). During that time, the sine wave changes as shown in Fig. 2 (a), and the same applies thereafter.
Rotation = changes in a sinusoidal waveform with a period of 10 steps. The same applies to other feeding points, where the phase difference between adjacent feeding points is 72 degrees (= 360
It changes like a sine wave of degree ÷ 5).

FIG. 2B shows the power supply state of the windings A to E by the difference between the PWM states of the power supply points at both ends of the windings. Here, only the waveform of the thin line will be described, and the thick line will be described later. For example, feeding points at both ends of the winding A are A and A, and a state in which A is connected to the high side and A is connected to the low side is defined as a + direction. In step 1, a is "+1.0" and a is "+0.31", so the power supply state is "+0.69".
Becomes Since the feed point change is sinusoidal,
It becomes a sinusoidal wave with a step cycle. The same applies to other windings, and the phase difference between adjacent windings in the order of windings A, C, E, B, and D becomes a sine wave of 72 degrees.

FIG. 2C shows the winding current. Here, only the thin line waveform will be described, and the thick line will be described later. Since the change speed of the winding current is affected by the time constant at the time of forming the charging / discharging circuit due to the inductance L of the winding and the characteristics of the switching element, it is not easy to represent the actual waveform. Therefore,
Here, the influence of the time constant can be ignored because the rotation speed is low and the current change is slow, and when the winding current is proportional to the power supply state, that is, when the power supply state is “+1.0”, the winding current is set to “+1”. .0 ". (Even if the rotation speed is high and the relationship between the feeding state and the winding current becomes complicated, the description below is essentially the same.) Therefore, the winding current is reduced by 10 steps as in the feeding state. , Winding A, C, E
-The phase difference between adjacent windings in the order of B and D becomes a sine wave of 72 degrees.

FIG. 2 (d) shows the feed point current corresponding to FIG. 2 (c), which is the difference between the corresponding winding currents. Here, only the thin line waveform will be described, and the thick line will be described later. For example, at the feeding point A, the winding current of the winding A is equal to the winding current of the winding D, at step 1, it is "+1.38", at step 6, it is "-1.38". The shout becomes a 72 degree sine wave. As described above, in the present invention, the PWM change at the feeding point has a sine wave shape, so that the feeding point current and the winding current all have a sine wave shape.

[Current Control Operation] In the present invention, as described above, based on the fact that the PWM change at the feeding point is a sinusoidal change, current control is performed by combining different excitation steps. The details will be described below. First, FIG. 3 (i) shows a time change of the excitation state in a case where “the combination of the excitation steps is the same”. This means "repeat only excitation step 1" in Fig. 2.
State. FIG. 4 shows a torque vector Sl of “excitation step 1” in FIG. 3 (i). As shown in FIG. 2 (a), the PWM state at the feed point is a = + 1.0, b = + 0.31, c = −0.81, d = −0.81, and e = + 0.31, so | Sl | ≒ 2.94.

Hereinafter, similarly, the excitation step 2, the step 3,...
Are formed as shown in the drawing. As apparent from FIG. 2, the five winding currents change in a so-called “five-phase sine wave (AC)” state, and therefore the torque vectors Sl... (S5
The size of the torque vector between the positions corresponding to the full steps is the same as well as the magnitude of the torque vector (not shown hereafter).

Next, as a case of “combination of excitation steps is different” in FIG. 3 (ii), the excitation step 1 of FIG. 2 is combined with the excitation step 5 which is 4 full steps away from it.
The case where these are repeated alternately will be described. Note that the cycle T of the excitation step period is equal to (i) and (ii) as shown, and the signal MCLK does not change within the range shown.

As shown in FIG. 5, the torque vector is S15 generated by a combined vector of Sl and S5. in this case,
Compared to the case where step 1 is repeated with a period of T in (i), (i
In step i), step 1 and step 5 form a set and are repeated at a period of 2T. Therefore, S15 is half of the combined vector of the torque vector Sl of step 1 and the torque vector of step 5, and | S15 | ≒ 0.91, | Sl | ≒ 2.94 in (i).

FIG. 6 shows a state where the excitation step advances in full step units due to the rising edge of the signal MCLK. Figure
6 (i) corresponds to FIG. 3 (i). After the rising edge of the signal MCLK, the excitation step proceeds from 1 to 2, and the signal MC
Step 2 is repeated until the next rising edge of LK comes. FIG. 6 (ii) corresponds to FIG. 3 (ii), and the signal MCLK
After the rising edge of, the repetition of the excitation step changes from "Step 1 and Step 5" to "Step 2 and Step
6 ”, and repeat the combination of“ Step 2 and Step 6 ”until the next rising edge of the signal MCLK comes. Here, an example of a full step is shown, but the same applies to a micro step. For example, when the number of divisions is 4, go from “Step 1 and Step 5” to “Step 1 1/4 and Step 5 1/4” become.

As is apparent from FIG. 5, the magnitude of the combined torque vector, that is, the generated torque (drive current) can be changed by changing the difference between the two types of steps (hereinafter, referred to as an offset amount).

In FIG. 5, the electrical angle formed by the two types of vectors is θ (θ is 0
And 180 degrees or less), the magnitude of the resultant vector is cos when the offset is 0 (the combination of the excitation steps is the same), that is, when θ = 0 degrees.
(Θ / 2) times.

FIG. 7 shows the correspondence between the offset amount and the magnitude of the torque vector. If the offset amount is 0, the magnitude of the vector will be the theoretical maximum value of about 2.94, and if the offset amount 5, that is, the directions of the two types of vectors are reversed, the magnitude of the torque vector will be 0, that is, the minimum, during which the torque vector will be As in a sinusoidal wave. Therefore, the generated torque can always be controlled to an arbitrary value from the maximum value according to the power supply voltage or the motor characteristics to 0, that is, a desired value.

[0042] In the case of "Step 1 and Step 5" shown in FIG. 5, that is, when the offset amount is 4, the PWM state of the feeding point, the winding feeding state, the winding current, and the feeding current are superimposed on FIG. . The time of "Step 1 and Step 5" in Fig. 4 (ii) is (i)
Corresponding to the position of step 1. The bold lines in FIG. 2A show the PWM states of the five feeding points A to E in comparison with the offset amount 0 (thin line). While the amplitude of the offset amount 0 is soil 1.0, the offset amount 4 is about 0.31. Except for the amplitude, it has the same sine wave shape as when the offset amount is 0. The bold line in FIG. 2B shows the power supply state of the windings A to E in comparison with the offset amount 0 (solid line). As in (a), only the amplitude changes in a similar manner without changing the period according to the offset amount. The amplitude is about 1.1 with an offset of 0.
At 8 the offset amount is about 0.36 on soil. The thick lines in FIG. 2 (c) show the winding currents of the windings A to E in comparison with the offset amount 0 (thin line). Similarly to the power supply state, the winding current similarly changes only the amplitude without changing the cycle according to the offset amount. The thick line in FIG. 2 (d) is a feed point current corresponding to the thick line in (c).

Therefore, the offset signal generator 101 of FIG. 1 operates as follows and controls the torque. When the total current i is smaller than the voltage corresponding to the torque target value (VRl <Vref)
Outputs a signal OFS that "decreases the amount of offset". When the total current i is larger than the voltage corresponding to the torque target value (VRl> Vref), the signal OFS outputs a value "increase the offset amount". In response to the signal OFS, the excitation signal generation unit 2A outputs the signals SP10 to SP50 and SN1 to SP5 in which the above-described offset amount is changed as described above, and controls the current. Although illustration is omitted, in the waveform at the time of offset shown in each of FIGS. 2A and 2B, only the amplitude changes according to the offset amount according to the offset amount, and the waveform itself has a similar shape to the waveform of offset 0. That is, even if the offset amount is changed, only the winding current, that is, the generated torque changes, and the other rotation characteristics (such as uneven rotation) are not affected by the offset amount.

Here, for comparison, the change of the winding current is not sinusoidal, and the two states are mixed in a time-division manner at the time of microstepping and the ratio thereof is changed linearly as described in the section of the conventional example. FIG. 8 shows the case where FIGS. 14 and 15) are applied to the above-described offset method, in the same manner as in FIG.

FIG. 8A shows the PWM state of the five feeding points A to E. Offset 0 for thin lines, offset 4 for thick lines
Is the case. For example, looking at the feed point a, offset 0
In the case of (thin line), it is “+1.0” in steps 1 and 2, becomes “0” in step 3, and changes linearly between steps 2 and 3. In the same manner, a substantially trapezoidal change as a whole, in which the change is linear, is performed at each feeding point. On the other hand, at offset 4 (thick line)
As shown in the figure, a triangular change is a partially mixed complex change, and does not have a similar waveform when the offset is zero.

FIG. 8 (b) shows the power supply state of the windings A to E by the difference between the PWM states of the power supply points at both ends of the windings. The thin line indicates the case of offset 0, and the thick line indicates the case of offset 4. For example, in the case of the winding A, when the offset is 0 (black line), the trapezoid changes continuously. The same applies to other windings. On the other hand, at the offset 4 (gray line), as shown in the figure, a complicated change occurs in which the power supply “0” period occurs between the trapezoidal shapes, and the waveform does not become analogous at the offset 0.

FIG. 8C shows the winding current, and the thin line indicates the offset.
In the case of 0, the bold line is the case of offset 4. even here,
As in FIG. 2 of the embodiment, the winding current is proportional to the power supply state, and when the power supply state is “+1.0”, the winding current is also “+1.0”, that is, when the proportionality constant is 1. As with the change in the power supply state, the winding current is offset 0 (offset 4) (thick line).
(Thin line) does not have a similar shape, and is completely different from the relationship that only the amplitude changes according to the offset amount and the waveform itself becomes a similar shape to the waveform of offset 0 as in the embodiment.

FIG. 8D shows the feeding point current corresponding to FIG. 8C. The thin line shows the case of offset 0, and the thick line shows the case of offset 4. Similarly to the change in the winding current, the supply current at the offset 4 (thick line) does not have a similar shape to the offset 0 (thin line), and is completely different. FIGS. 9 and 10 show current waveforms at the feeding point when the inventors actually control the current driving of the five-phase stepping motor by the above-described method. The stepping motor is of the ring connection type shown as a conventional example, has 500 full steps per rotation of the motor shaft, and has a drive current (feed point current) standard of 3 amps pp. The standard rotation speed of this motor is 1.8 revolutions per second, but as described above, the motor was driven at about 0.22 revolutions per second as an example of a very low speed.

FIG. 9 shows a case where the driving is performed with the sinusoidal change shown in FIG. 2, and the current waveform at the feeding point is almost sinusoidal. FIG. 10 shows a case where driving is performed by the trapezoidal waveform change shown in FIG. 8, and the current waveform at the feeding point has a shape similar to the trapezoidal waveform shown in FIG.
It turns out that it is close to a theoretical value. It is sufficiently clear from the above that normal control cannot be performed when the trapezoidal drive is applied to the offset method.Thus, a detailed description will be omitted. When the amount is close to 5 full steps, a state in which the rotation operation is performed intermittently appears, and the torque control itself is not performed normally.

From the above, in the offset method of the present invention, the condition for normal torque control is that the change in winding current is sinusoidal, that is, the change in PWM at the feeding point is sinusoidal. Become. In the present invention, since the motor power supply voltage, that is, the high-side voltage is constant at Vm (the voltage VRl is very small), the voltages of the signals SP1 to SP5, which are the outputs of the voltage conversion unit 3A, are represented by " Vm−10 volts ”, and when off, it is fixed to“ Vm ”. That is, the output of the voltage conversion unit 3A does not need to use a multiple power supply like the voltage conversion unit 3 of the conventional example, and can be constituted by a very simple circuit of a single power supply.

The micro-step described in the conventional example is
As shown in FIGS. 14 and 15, two states 「1 full step apart and adjacent to each other’ are combined in a time-division manner, and the ratio is changed to change the direction of the torque vector. The purpose and operation of the present invention are completely different from those of the present invention.

In the present invention, as shown in FIG. 3, since two types of states are repeated, the cycle unit of the PWM change is 2T, and the current change due to the PWM operation is smaller than the change cycle T of the conventional example. The frequency of the sound generated by delicately vibrating the coil etc. is reduced by half, and it appears that the sound becomes audible.
However, if the frequency considered to be generated is higher than the audible frequency range, that is, if T is set to, for example, about 30 microseconds, the frequency becomes about 16 kHz, and it is easy to make the generated sound inaudible. As is clear from what has been described so far, the PWM cycle does not need to be “changed for current control”, so that there is no problem in current control even in this case.

In this embodiment, the description has been made of the stepping motor having the five-phase ring connection. However, in principle, the present invention is not limited to the "five-phase", "ring connection", and "stepping motor". As long as the motor is driven by supplying a current from a power supply point corresponding to the motor and changing the amount in the time axis direction, the present invention can be widely applied to not only a rotary motor but also a linear motor.

[0054]

As described above, according to the present invention,
Circuit that converts motor power supply voltage (conventional current controller
1) The switch element (Pl ~ 5
And Nl to 5) also perform current control, eliminating the need for large components such as the switching element Ql, coil Ll, and capacitor Cl, which are the components of the motor power supply voltage conversion unit, and further reducing the magnitude of torque. And the voltage on the high side is constant, so the voltage converter that generates the operation signal for the high side switch element can be a simple configuration with a single power supply,
The cost can be drastically reduced as compared with the conventional method, and the entire drive circuit can be further reduced in size.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a change over time in a power supply state, a current, and the like according to the first embodiment.

FIG. 3 is a timing chart of the first embodiment.

FIG. 4 is a diagram illustrating a torque vector according to the first embodiment.

FIG. 5 is a diagram illustrating a combined torque vector according to the first embodiment.

FIG. 6 is a diagram illustrating a progress state of the first embodiment.

FIG. 7 is a diagram illustrating an offset amount and a magnitude of a torque vector.

FIG. 8 is a diagram illustrating a change over time in a power supply state, a current, and the like in a conventional example.

FIG. 9 is a diagram showing a time change of a supply current with a sine wave change.

FIG. 10 is a diagram showing a change over time in a supply current with a trapezoidal wave change.

FIG. 11 is a circuit diagram of a conventional example.

FIG. 12 is a diagram for explaining a method of exciting a five-phase stepping motor.

FIG. 13 is a diagram showing a torque vector of a conventional example.

FIG. 14 is a timing chart of a micro step.

FIG. 15 is a diagram showing a torque vector of a micro step.

[Explanation of symbols]

 1 Current control unit 2, 2A Excitation signal generation unit 3, 3A Voltage conversion unit 6 Stepping motor 11 Current control signal generation unit 101 Offset signal generation unit Pl to P5 Nl to N5 QI Switch element Ll Coil Cl Capacitor Rl Resistance Vm Motor power supply

Claims (4)

[Claims] In a stepping motor driving method for exciting each winding set of a stepping motor having a plurality of winding sets in a predetermined procedure according to a stepping pulse, a feeding point is provided so that each winding current is changed in a sine wave shape. The power supply state is changed to include one type of power supply state in electrical angle, and two or more types of power supply states separated by more than one full step in electrical angle are asynchronous with the stepping pulse with a cycle shorter than the stepping pulse cycle A stepping motor driving method, wherein the two or more power supply states are changed together according to a stepping pulse. 2. The stepping motor driving method according to claim 1, wherein the windings of the stepping motor are connected in a ring shape. 3. The stepping motor driving method according to claim 1, wherein the winding sets of the stepping motor, that is, the feeding points are five points. 4. The method according to claim 1, wherein a total current flowing through the stepping motor is detected, and the two or more power supply states are switched according to a difference between a total current flowing through the winding of the stepping motor and a target current. Item 4. The stepping motor driving method according to item 1.