JPH0112560Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention is a stepping motor drive circuit that sequentially sets each mode of high speed mode, low speed mode, and hold mode, and forms a drive signal for rotating the stepping motor by a predetermined angle. Regarding.

2. Description of the Related Art Conventionally, a stepping motor is used as a drive device for quickly moving a moving body from a current position to a predetermined position and setting it at a predetermined position with high precision. In order to move the moving object in this way, the rotation angle of the stepping motor must be regulated with high precision. For this purpose, a sensor is provided to detect the rotation angle of the stepping motor.
The output signal of the sensor forms a drive signal for the stepping motor to set the stepping motor in high speed mode, low speed mode, or hold mode, and stops the stepping motor when it has rotated by a predetermined angle. Therefore, in order to quickly and accurately set a moving object in a predetermined position,
It is necessary to form drive signals for each mode with high precision.

An example of a device that uses such a stepping motor as a driving device is a printer. Below, we will take a type wheel of a printer as an example of a moving object.
A conventional drive circuit for forming a drive signal for a stepping motor that rotationally drives the type wheel will be described.

FIG. 1 is a schematic perspective view showing an example of a conventional type wheel drive mechanism, in which 1 is a type wheel;
2 and 3 are gears, 4 is a dividing plate, 5 is a sensor, and 6 is a stepping motor.

In the figure, when the stepping motor 6 rotates, this rotation is transmitted to the type wheel 1 via the gears 3 and 2. A large number of type arms having type are attached to the type wheel 1 in a petal shape, and the type is moved from the current position to a predetermined position where the desired type can be printed, that is, the printing position.
The stepping motor 6 rotates.

Further, a dividing plate 4 having a large number of notches is attached to the rotating shaft of the stepping motor 6, and a sensor 5 is provided opposite to this dividing plate 4. The sensor 5 is, for example, a photo sensor, and when the stepping motor 6 rotates, a pulse signal representing the rotational phase of the stepping motor 6 is obtained from the sensor 5 due to the cut in the dividing plate 4. Therefore, the rotation angle of the stepping motor can be known from this pulse signal, and thereby each mode of the stepping motor 6 can be set.

FIG. 2 is a block diagram showing an example of a conventional drive circuit that uses such pulse signals to form drive signals for each mode of the stepping motor 6, in which 7 is a drive circuit, 8 is a pulse count unit, and 9 is a drive circuit. Hold pulse pattern generator, 1
0 is a comparison unit, 11 is a pulse converter, and 12 is a drive amplifier, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In FIG. 2, a pulse signal from a sensor 5 is supplied to a pulse count unit 8 of a drive circuit 7 and a hold pulse pattern generation circuit 9.
The pulse count unit 8 counts the pulse signals and sequentially supplies the count value to the comparison unit 10.

The comparison unit 10 includes a stepping motor 6.
Numerical values corresponding to the rotation angle for each mode are set as reference values, and the comparison unit 10 compares these reference values with the count value from the pulse count unit 8 and generates a command signal for each mode.

On the other hand, the hold pulse pattern generator 9 is phase-synchronized with the pulse signal supplied from the sensor 5,
The stepping motor 6 generates a signal corresponding to a drive signal in the hold mode, that is, a hold pulse pattern. This hold pulse pattern is supplied to the pulse converter 11, converted based on the command signal from the comparison unit 10, amplified by the drive amplifier 12 as a drive signal, and supplied to the stepping motor 6.

FIG. 3 is a speed curve diagram showing an example of a method of driving the stepping motor 6. As shown in FIG. In this figure, the current position of the desired type to be printed on the type wheel 1 (FIG. 1) is taken as the reference position with an angle of 0, and the angle D is taken as the printing position.

For this type, the stepping motor 6 is accelerated in high speed mode H _i from angle 0 to angle A, decelerated in hold mode H _p from angle A to angle B, and slowed down from angle B to angle C. Set mode L _p , and then change angle C to angle D.
Until then, the hold mode is set to H _p and the speed is decelerated until the desired type is rotated by an angle D and then stopped.

This angle is also expressed by the count value of the pulse count unit 8, and the angles A, B, C
is also expressed by the reference value set in the comparison unit 10. By comparing these angles in the comparison unit 10, each mode of the stepping motor 6 can be commanded.

Although FIG. 3 shows an example of the method of driving the stepping motor 6, the order of the modes is generally set as shown below, and depending on the angle from the current position to the printing position, , low speed mode, and hold mode are set, and therefore, the reference value set in the comparison unit 10 differs depending on the required rotation angle of the stepping motor 6. However, the hold mode is always set at the end, and in this hold mode, each reference value is set so that the stepping motor 6 is decelerated and the desired type is stopped at the printing position.

FIG. 4 is a curve diagram showing the torque of the stepping motor 6 in each mode, where a is a torque curve in the hold mode, b is a torque curve in a low speed mode, and c is a torque curve in a high speed mode. This is the torque curve of Further, angle 0 is the current position of the type, and when the torque is positive, the stepping motor 6 attempts to rotate in the direction of arrow X. When the torque is negative, it tries to rotate in the direction of arrow Y in the opposite direction.

Therefore, when the stepping motor 6 is in the hold mode, the torque is zero at the current position, and when the stepping motor 6 deviates from this position, a torque in the opposite direction is generated to return it to the current position. Therefore, in FIG. 3, high speed mode H _i or low speed mode L _p
When switching from to hold mode _Hp , a torque is generated in the stepping motor 6 at each moment to maintain the state at that moment, and as a result, the stepping motor 6 is braked and decelerated.

In the low speed mode, as shown in FIG. 4b, the torque curve is set so that it is maximum at the current position and decreases as the engine rotates. Therefore, if the torque curve is set as shown in FIG. 4b, the maximum torque will be generated as the motor rotates in the direction of the arrow X, and the torque will decrease as the motor rotates.

In the high-speed mode, a torque curve is set that is zero at the current position and increases as the motor rotates. In this case, in Fig. 3, the angle 0
When the high-speed mode H _i is set, the torque at this time is zero, so the stepping motor 6
cannot rotate, and if for some reason a rotational force is applied in the opposite direction to the desired direction, it will begin to rotate in that direction, making it extremely unstable. For this purpose, in practice, the low speed mode is once set and the high speed mode H _i is set after rotating in the desired direction.

The reason why the torque in high-speed mode is set in this way is that there is a delay in the rise of the supplied current due to the inductance component of the coil of the stepping motor 6.
For this reason, the force generated by the supply current generated in the stepping motor 6 is delayed, so the maximum torque point of the stepping motor 6 is shifted in consideration of this delay, and the maximum torque point of the stepping motor 6 is shifted. It improves efficiency by producing maximum power when

As described above, in order to form a drive signal for the stepping motor 6 in each mode, the hold pulse pattern generator 9 and the pulse converter 11
is provided.

The hold pulse pattern generator 9 generates a signal having the same phase as the drive signal of the stepping motor 6 in the hold mode, that is, a hold pulse pattern in synchronization with the pulse signal from the sensor 5. The pulse converter 11 is connected to the comparison unit 1
A drive signal is formed by shifting the phase of the hold pulse pattern according to each mode according to a command signal from 0. In the high speed mode, the hold pulse pattern is phase shifted by a predetermined amount, and in the low speed mode, the hold pulse pattern is shifted. The phase is shifted by another predetermined amount, and in the hold mode, the phase of the hold pulse pattern is kept unchanged.

FIG. 5 is a timing chart illustrating an example of the operation of the drive circuit 7 when the stepping motor 6 is 4-phase excited, where S is the output pulse signal of the sensor 5, H _A , H _B , H _C , H _D is the output signal (hold pulse pattern) of the hold pulse pattern generator 9, and C _A , C _B , C _C , and C _D are drive signals from the pulse converter 11, which are applied to each phase coil of the stepping motor 6. It is supplied.

Now, the rotation of the stepping motor 6 required for the sensor 5 to output one cycle of the pulse signal is 1 rotation.
A case will be described in which the stepping motor 6 rotates 19 steps in order to move the desired type on the type wheel 1 from the current position to the printing position. When starting the ping motor 6,
First, the low speed mode L _p is set, and when the stepping motor 6 starts rotating, the high speed mode H _i , the hold mode H _p , and the low speed mode L _p are sequentially set.
Finally, the stepping mode 6 shall be controlled so that the hold mode H _p is set and the above-mentioned type is set at the printing position, and the initial switching from the low speed mode L _p to the high speed mode H _{i is} 1. At the 8th step, switching from high-speed mode H _i to hold mode H _p is performed at the 8th step.
Switching from H _p to low speed mode L _p is the 12th step, and from this low speed mode L _p to hold mode
It is assumed that the switch to H _p is made at the 17th step, and when the switch is made at such a step, the desired type is set at the print position.

Now, the hold pulse pattern generator 9 shown in FIG. 2 generates four signals H _A , H _B , H _C , _HD which are phase synchronized with the pulse signal S from the sensor 5 . These signals have a period equal to four periods of the pulse signal S, that is, four steps, and have rising and falling edges alternately every two steps. The phases of these signals are sequentially different by π/2 radians, and the phases of the signals H _A , _HB , _HC , and _HD are advanced by π/2 radians in that order.

Now, let us assume that the high level of these signals is "1" and the low level is "0", and the signals H _A , H _B ,
Combination of levels of H _C and _HD (H _A , H _B , H _C ,
H _D ), (1, 1, 0, 0), (1, 0,
0,1), (0,0,1,1), (0,1,1,0)
The combination of levels changes step by step in this order, and is repeated every four steps. When a change pattern of such level combinations (partial patterns), that is, a pulse pattern, is generated from the hold pulse pattern generator 9, and the drive signal has such a pulse pattern, the stepping motor 6 is set to the hold mode. This pulse pattern is a hold pulse pattern.

The pulse converter 11 receives the signals H _A , H _B , H _C ,
_HD is phase shifted in high speed mode and low speed mode. The amount of phase shift in high speed mode is π radians (2 steps), and the amount of phase shift in low speed mode is 3π/
2 radians (3 steps). This means that
In high-speed mode, this is nothing more than converting the partial pattern of the hold pulse pattern as follows. That is, (1,1,0,0)→(0,0,1,1) (1,0,0,1)→(0,1,1,0) (0,0,1,1)→ (1,1,0,0) (0,1,1,0)→(1,0,0,1) Therefore, in the hold mode, the voltage is supplied to the first phase coil of the stepping motor 6. The signal (i.e., coil signal) C _A is the signal H _A , the second phase coil signal C _B is the signal H _B , the third phase coil signal C _C is the signal H _C , and the fourth phase coil signal C _D is the signal Assuming H _D , in high-speed mode, the coil signal C _A is changed to the signal H _C
In this case, the coil signal C _B can be changed to the signal _HD , the coil signal C _C can be changed to the signal H _A , and the coil signal C _D can be changed to the signal H _B. This results in the torque curve of FIG. 4c, which is the torque curve of FIG. 4a shifted to the right by π radians.

Similarly, in the low speed mode, the partial pattern of the hold pulse pattern is converted as follows. That is, (1,1,0,0)→(1,0,0,1) (1,0,0,1)→(0,0,1,1) (0,0,1,1)→ (0,1,1,0) (0,1,1,0)→(1,1,0,0) Therefore, in this case, the coil signal C _A becomes the signal H _B , and the coil signal C _B to signal H _C , coil signal C _C to signal H _D , and coil signal C _D to signal H _A
And it is sufficient. This results in the torque curve shown in FIG. 4b being shifted from the torque curve shown in FIG. 4a to the right by π/2 radians.

The pulse count unit 8 is a subtraction circuit that subtracts 1 for each pulse of the pulse signal from the sensor 5, and is initially set to a value of 19.

Therefore, when the stepping motor 6 is started, the value 19 from the pulse count unit 8 is supplied to the comparator unit 10, and a command signal for the low speed mode _Lp is supplied to the pulse converter 11. Based on this command signal, the pulse converter 11 converts the supplied hold pulse pattern as described above, and generates a drive signal corresponding to the low speed mode L _p . This drive signal is amplified by a drive amplifier 12 and supplied to the stepping motor 6 as a coil signal.

Therefore, the stepping motor 6 rotates at a low speed,
A pulse signal is obtained from the sensor 5. When the pulse count unit 8 reaches a count value of 18 (first step), the comparison unit 10 detects this and gives a command signal for the high speed mode _Hi to the pulse converter 11. The pulse converter 11 converts the hold pulse pattern as described above based on this command signal, and the stepping motor 6 switches to the high speed mode H _i
It rotates at an accelerated pace.

Next, when the count value of pulse count unit 8 reaches 11 at the 8th step, comparison unit 10
emits a command signal for hold mode H _p , and pulse converter 11 generates a drive signal with the same pulse pattern as the hold pulse pattern. For this purpose, the stepping motor 6 is in the hold mode H _p
As a result, the brake is applied and the rotation is decelerated.

Furthermore, when the count value of pulse count unit 8 reaches 7 at the 12th step, comparison unit 1
0 issues a command signal for the low speed mode _Lp , the pulse converter 11 converts the hold pulse pattern as described above, and the stepping motor 6 rotates at a low speed.

Then, when the count value of the pulse count unit becomes 2 at the 17th step, the comparison unit 10
A command signal for hold mode H _p is generated from
The stepping motor 6 decelerates and stops when the desired character comes to the printing position.

In this way, the stepping motor 6 is controlled and the desired type is set at the printing position, but in order to set the position accurately,
The rotation speed of the stepping motor 6 in each mode must be accurate. For example, if the type at the current position (angle 0) is accurately set to the printing position at angle D by passing through the speed curve shown in FIG. 3, then the high speed mode H _i ,
Even if at least one of the speeds changes slightly in the low speed mode L _p , the type will not stop at angle D, and even if the brake action in the hold mode H _p is slightly out of order, the type will deviate from the printing position. and stop.

As described above, in the method of controlling a stepping motor using this conventional drive circuit, the accuracy of the rotational speed of the stepping motor in each mode is a very important point.

However, in order to be able to control such a stepping motor, the stepping motor must be designed so that the desired speed characteristics can be obtained with high accuracy, and the stepping motor must be designed so that the desired speed characteristics can be obtained with high accuracy. The mode selection and mode switching point (number of steps) are set according to the speed characteristics of the stepping motor, but the design value and the actual value do not necessarily match, and some errors inevitably occur. As a result, the accuracy of setting the position of the printed characters is low.

Furthermore, even if the speed characteristics and mode switching points of a stepping motor can be set with high precision during manufacturing, the speed characteristics of a stepping motor will depend on the surrounding environment such as temperature and humidity. Since it changes over time and is accompanied by aging, the accuracy of setting the position of printed characters deteriorates.

The above can be said not only for setting the position of type in a printer, but also for devices that use stepping motors to move moving objects in general. It was practically impossible to do well.

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned prior art,
Setting the position of a moving object using a stepping motor,
To provide a stepping motor drive circuit capable of always performing high precision driving.

In order to achieve this objective, the present invention creates a braking action on the stepping motor in the hold mode, which is the final mode of the stepping motor, in accordance with the rotational speed of the stepping motor at the start of the hold mode. It is characterized by the fact that it allows

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 6 is a block diagram showing an embodiment of the stepping motor drive circuit according to the present invention, in which 13 is a fall detector, 14 is a pulse interval detector, 15 is a time/speed converter, and 16 is an AND gate, 17 is an OR circuit, 18, 19, 20, 21 are registers, 22, 23, 24 are comparators, 25, 2
6, 27 are arithmetic units, 28, 29, 30 are registers, 31 are comparators, 32 are registers, 33, 3
4, 35, 36 are comparators, 37, 38 are programmable delay circuits, 39, 40 are AND gates, 4
1 is an OR circuit, 42, 43, 44 are inverters,
45 is a memory, 46 is a control unit, and 47 is an amplifier, and parts corresponding to those in FIG. 2 are given the same reference numerals, and some explanations will be omitted.

In FIG. 6, the pulse signal S from the sensor 5
is amplified by an amplifier 47 and supplied to the fall detector 13 of the drive circuit 7 according to the present invention. The falling edge detector 13 generates a pulse signal that coincides with the falling edge of the supplied pulse signal S, that is, a falling pulse signal a, and this falling pulse signal a is sent to the pulse interval detector 14 and the pulse count unit. 8 and an AND gate 16.

When the output level of the comparator 33 is low level (hereinafter referred to as
(referred to as "L"), the AND gate 16 is in a conductive state by the inverter 44, and the falling pulse signal a is transmitted to the AND gate 16 and the OR circuit 17.
The signal is supplied to the hold pulse pattern generator 9 via the hold pulse pattern generator 9. For this purpose, the hold pulse pattern generator 9 generates a hold pulse pattern H that is phase synchronized with the falling pulse signal a, and therefore the pulse signal S from the sensor 5, and the pulse converter 11 converts this hold pulse pattern into A drive signal C is generated by performing processing according to each mode. The stepping motor 6 is controlled by the drive signal C, and the above operation is similar to the conventional drive circuit shown in FIG.

The pulse interval detector 14 measures the time interval between each pulse of the falling pulse signal a, and the time/speed converter 15 calculates each step of the stepping motor 6 from the time interval detected by the pulse interval detector 14. Detect the average rotational speed for each rotation. Therefore, the pulse interval detector 14 and the time/speed converter 15 constitute a speed detection unit.

Comparators 33, 34, 35, 36 correspond to comparison unit 10 of FIG. The comparator 34 compares the count value M of the pulse count unit 8 with the register 2.
Compare the value N ₁ stored in 9 and find that M>N ₁
At this time, a high-speed command signal h _i of high level (hereinafter referred to as "H") is generated. The comparator 35 receives the count value M of the pulse count unit 8 and the register 2.
Numeric value N ₁ stored in 9 and register 30
A numerical value N ₂ stored in is supplied, and N ₁ ≧M>
When _N2 , a hold command signal _hp of "H" is generated. The comparator 36 is connected to the pulse counting unit 8
The count value M is compared with the numerical value N ₂ stored in the register 30, and when N ₂ ≧M, a low speed command signal l _p of “H” is generated. Furthermore, the comparator 33
is for setting the hold mode which is the final mode of the stepping motor 6, and a certain reference value is set, and when the count value M of the pulse count unit 8 becomes equal to this reference value. , generates an "H" output signal f, which becomes the hold command signal h _p .

The high speed command signal h _i from the comparator 34 is supplied to the pulse converter 11 through the AND gate 39, and puts the pulse converter 11 into the high speed mode. Comparator 35
The hold command signal h _p from the pulse converter 11 is supplied to the pulse converter 11 through the OR circuit, and the pulse converter 11 is placed in the hold mode. The low-speed command signal l _p from the comparator 36 is supplied to the pulse converter 11 through the AND gate 40 to put the pulse converter 11 into the low-speed mode, and is inverted by the inverter 43 to turn the AND gate 39 into a cutoff state. This is because the numerical values stored in the registers 29 and 30 are set as described later, so that the low speed mode is prioritized over the high speed mode. Furthermore, the "H" output signal f of the comparator 33 passes through the OR circuit 41 to put the pulse converter 11 into the hold mode, and is inverted by the inverter 42 to cut off the AND gate 40. This is because the hold mode set by the output signal f of the comparator 33 is given priority over the low speed mode based on the numerical values similarly stored in the registers 29 and 30.

Here, this embodiment will be described with reference to control of the type wheel 1 (FIG. 1) of a printer, and assuming that the stepping motor 6 exhibits the speed curve shown in FIG. 3. However, this is applicable not only to type wheels but also to drive control of general moving bodies. Although not shown in FIG. 3, it goes without saying that a low speed mode L _p is provided as the first stage mode before the high speed mode H _i .

Therefore, the pulse count unit 8 calculates the angle D
The number of steps when the stepping motor 6 rotates by the amount shown in FIG. 3 is preset, and counts down by one for each pulse of the falling pulse signal a. The pulse count unit 8 is also provided with a flip-flop circuit, for example, and when one falling pulse is supplied, the pulse count unit 8 detects that it has counted down by one, and performs high-speed counting as described below. A command signal indicating the start of mode H _i is generated.

On the other hand, the register 29 stores a numerical value (hereinafter referred to as the value of angle A) equal to the count value of the pulse count unit 8 when the stepping motor 6 rotates through the angle A (FIG. 3). The register 30 contains a value larger than the number of steps preset in the pulse count unit 8 (hereinafter referred to as the initial step value) and a value when the stepping motor 6 is at an angle B.
(FIG. 3) A numerical value (hereinafter referred to as the value of angle B) equal to the count value of the pulse count unit when the rotation is performed is selectively stored. The exchange of these initial stage values and the value of angle B in the register 30 is performed based on the above-mentioned command signal generated from the pulse counter unit 8, and this command signal indicates that the count value of the pulse counter unit 8 is This occurs when a count value corresponding to the boundary between the low speed mode and the high speed mode, which is the first stage mode of No. 6, is reached.

The preset value of the pulse count unit 8 and the numerical values stored in the registers 29 and 30 are stored in advance in the memory 45, and under the control of the control unit 46, these numerical values are read out and stored in the pulse counter. 8 and registers 29 and 30,
When one operation of the stepping motor 6 is completed, the values stored in the registers 29 and 30 are returned to the memory 45. Further, the above command signal generated by the pulse count unit 8 is supplied to the control unit 46, and changes the numerical value stored in the register 30 from the initial value to the value of the angle B.

A reference value is set in the comparator 33, which is equal to the count value of the pulse count unit 8 when the stepping motor 6 rotates by an angle C (FIG. 3). Here, the number of steps in the final hold mode H _p period shown in FIG. 3 is determined by one operation of the stepping motor 6, that is, setting the desired type on the type wheel 1 (FIG. 1) at the printing position. The reference value of the comparator 33 can be kept constant by providing the pulse count unit 8 with a countdown function.

Note that the comparator 31 is set to a reference value of zero, and by comparing this reference value with the count value M of the pulse count unit 8, it detects that this count value M has become zero and issues a movement end signal. occurs.

Next, a description will be given of means for correcting errors in type wheel drive control that are caused by errors in the speed characteristics of the stepping motor 6 and errors in the braking action, which constitute the essential part of the present invention.

As shown in _FIG . 3, the function of this correction means is as follows _: This adjusts the braking action in the hold mode H _p , which is the final mode, and performs homing control so that the desired type can be accurately set at the printing position even if there is an error in the speed or braking action mentioned above. . The adjustment of the brake action is performed during the printing operation currently being executed, but the adjusted brake action is used in the final hold mode of the next printing operation with the same number of steps. That is, this correction means has a learning function that sets the optimum braking action in the final hold mode for the next printing operation with the same number of steps for each printing operation.

Therefore, assuming that the stepping motor 6 is designed to rotate according to the speed curve shown in FIG.
When becomes 2, it generates an "H" output signal f, which causes the hold mode H _p (hereinafter, the period of this hold mode H _p is referred to as the homing period F).
is set, but at the same time, this output signal f is inverted by the inverter 44 to turn off the AND gate 16. At the same time, the output signal f is supplied to the programmable delay circuit 37, and as shown in FIG. 7, a delayed signal _d1 delayed by the time _T1 is obtained. This delay signal d ₁ is supplied to the OR circuit 17 and the programmable delay circuit 38, and from the programmable delay circuit 38, as shown in FIG.
A delayed signal d ₂ that is further delayed by a time T ₂ is obtained and supplied to the OR circuit 17 . Therefore, during this homing period F, the hold pulse generator 9 receives the delayed signal supplied via the OR circuit 17.
A hold pulse pattern is obtained by synchronizing the phase with the rising edges of d ₁ and d ₂ and the signals H _A , H _B , H _C , _HD with the phases shown in FIG _{. B} , C _C and C _D are obtained from the pulse converter 11.

The delay amount of the programmable delay circuit 37 is set by the numerical value (hereinafter referred to as delay value) _D1 stored in the register 28, and the delay amount of the programmable delay circuit 38 is set by the numerical value (hereinafter referred to as delay value) stored in the register 18. (hereinafter referred to as the delay value) is set by _D2 . The delay value D ₂ is a constant value that varies depending on the number of steps required to move the type on the type wheel 1 (Fig. 1) to the printing position, whereas the delay value D ₁ is the count value of the pulse count unit 8. It is adjusted according to the rotational speed of the stepping motor 6 when M is zero.

That is, the time/speed converter 15 outputs a numerical value representing the rotational speed of the stepping motor 6 (hereinafter referred to as the actual speed value R), and the register 19 stores the value when the count value M of the pulse count unit 8 is zero. Designed rotational speed of stepping motor 6
Numeric value representing Vo (hereinafter referred to as reference speed value Ro)
is stored, and when the comparator 31 detects that the count value M has become zero, this reference speed value
Ro and the actual speed value R are supplied to a comparator 22.
When the comparator 31 detects that the count value M of the pulse count unit 8 has become zero, the comparator 22 operates for a short period of time, and Ro>R, Ro=R,
Determine whether Ro<R. This determination result is supplied to the arithmetic unit 25, and as its output value, -1 when Ro>R, 0 when Ro=R, and +1 when Ro<R, is supplied to the register 28. The register 28 adds this output value to the stored delay value D ₁ and corrects it as a new delay value D ₁ to be used next time. As a result, when the braking action is strong, the actual speed value R when the count value M is zero becomes small, and the desired type stops before the printing position, so the programmable delay circuit 37 The delay amount is shortened to weaken the brake action. Conversely, if the braking action is weak, the actual speed value R when the count value M is zero will increase, and the desired printed character will stop after passing the printing position, so the delay of the programmable delay circuit 37 will increase. Increase the amount so that the brake action becomes stronger.

The reference speed value Ro stored in the register 19 is
A value that ensures that when the actual speed value R from the time/speed converter 15 is equal to this reference speed value Ro when the count value M of the pulse count unit 8 is zero, the type always stops accurately at the printing position. , which is a constant value depending on the number of steps required to move the type to the printing position.

In this way, the programmable delay circuit 37
The braking action of the stepping motor 6 during the homing period F is adjusted so that the type is accurately stopped at the printing position.

The delay values D ₂ and D ₁ of the registers 18 and 28 and the reference speed value Ro of the register 19 are normally stored in the memory 45, and the values corresponding to the number of steps required to move the type to the printing position are read out and respectively The modified delay value D ₁ stored in registers 18, 19, 28 is stored again in memory 45 when the operation for that character is completed.

Note that when the comparator 31 detects that the count value M is zero, the programmable delay circuit 38 is reset. Due to this reset, the output level of the programmable delay circuit 38, which was at "L" immediately before this reset, is inverted to "H".
Therefore, this output level is determined by the rise of the delay signal _d1 from the programmable delay circuit 37.
Either it is delayed by T ₂ and inverted from "L" to "H", or it is inverted from "L" to "H" by the output signal of the comparator 31, and this inversion of the output level is caused by the count value M is never later than the point when becomes zero.

This is because if the phase of the hold pulse pattern H is changed after the count value M becomes zero, the torque will not become zero when the count value M is zero, but a large torque in the opposite direction will be generated, and the operation will be interrupted. This is to prevent errors from occurring.

As described above, the influence of the speed error of the stepping motor 6 and the brake action error can be prevented, and the printing position of the _characters can be set _accurately . Yako's hold mode H _p and the following low speed mode
By correcting the switching point of L _p according to the speed error of the stepping motor 6 and the error of the brake action, the position setting accuracy of the print position of the type in the next printing operation of the same number of steps can be further improved. I can do it.

For this purpose, the angle A stored in the register 29
and the value of the angle B stored in the register 30 are not constant, but are modified in accordance with the rotational speed of the stepping motor 6 detected by the time/speed converter 15.

That is, the register 20 contains the high-speed mode H _i
A numerical value representing the designed rotational speed V _A of the stepping motor 6 that should occur at the time of switching between and the next hold mode H _p (hereinafter referred to as reference speed value R _A )
is stored in the register 21, and the value representing the designed rotational speed _VB of the stepping motor 6 that should occur at the time of switching between the hold mode _Hp and the next low speed mode _Lp (hereinafter referred to as the reference speed) is stored in the register 21. The value _RB ) is stored.

The reference speed value R _A and the actual speed value R of the register 20 are supplied to the comparator 23, and when the output signal (hold command signal h _p ) of the comparator 35 is supplied,
It operates for a short period of time near its rise point, and R _A
>R, R _A =R, R _A <R is determined. This determination result is supplied to the arithmetic unit 26, and its output value is supplied to the register 29 as +1 when R _A >R, 0 when R _A =R, and -1 when R _A <R. The register 29 adds this output value to the stored value of angle A and corrects it as a new value of angle A to be used next time. By adding this output value, the stepping motor 6
_If the rotational speed _of
It is advanced by one step so that the actual speed value R at the time of switching from the high speed mode H _i to the hold mode H _p becomes equal to the reference speed value R _A .

In addition, the reference speed value R _B of the register 21 and the time
The actual speed value R from the speed converter 15 is connected to the comparator 24.
is supplied to The comparator 24 operates for a short period of time near the rising edge of the output signal of the comparator 36 (low-speed command signal l _p ), and determines whether R _B > R, R _B = R, or R _B < R. . This judgment result is calculated by computing unit 2.
When R _B >R, -1 when R _B =R, and 0 when R _B <R, +1 is supplied to the register 30 as its output value. The register 30 adds this output value to the stored value of angle B and corrects it as a new value of angle B to be used next time. As a result, when the braking action of the stepping motor 6 is large in the hold mode H _p following the high speed mode H _i (that is, when the deceleration effect is large), the hold mode H _p is changed to the low speed mode.
The angle B (FIG. 3) for switching to L _p is advanced by one step; conversely, when the braking action is small, angle B is delayed by one step, switching from the hold mode H _p to the low speed mode L _p . The actual speed value R at the time of the change is made equal to the reference speed R _B.

Note that the calculation units 26 and 27 are connected to the registers 29 and 30.
The timing for supplying the above output values to the respective modes is after at least one step has elapsed since the comparators 35 and 36 commanded the respective modes. This is to prevent the comparators 34, 35, and 36 from making erroneous decisions even if the reference speed values R _A and R _B in the registers 29 and 30 are corrected, respectively.

As is clear from the above explanation, register 2
The reference speed values R _A and R _B stored at 0 and 21 are constant values that vary depending on the number of steps required to move the type on the type wheel 1 (FIG. 1) to the printing position, and are stored in the memory 45. Once the number of steps representing the difference between the current position of the type and the printing position is determined, the reference speed value corresponding to this number of steps is determined.
R _A and R _B are read from the memory 45 and stored in the registers 20 and 21.

Note that writing of the corrected numerical values stored in the registers 28, 29, and 30 into the memory 45 is performed by the control unit 46, which operates after a certain period of time after the movement end signal is supplied from the comparator 31. .

The register 32 stores a value that determines the rotational direction of the stepping motor 6 (hereinafter referred to as rotational direction value), and controls the hold pulse pattern generator 9 to generate a hold pulse pattern H corresponding to the rotational direction.

As described above, the memory 45 stores the preset values of the pulse count unit 8, registers 18, 19, 20, 21, 28, 2, classified by the number of steps it takes for the type to reach the printing position.
9 and 30 are memorized, and when a device (not shown) detects the required number of steps of printing, the control unit 46 reads out the preset values and numerical values corresponding to this number of steps. The signal is output and sent to the pulse count unit 8 and the respective registers. When the printing operation is completed, the corrected values in the registers 28, 29, and 30 are returned and stored at the corresponding addresses in the memory 45, respectively. Further, the rotational direction value to be stored in the register 32 is also stored at a predetermined address in the memory 45.

The memory 45 is a ROM (read-only memory)
Consists of RAM (Random Access Memory).
The ROM contains preset values of the pulse count unit 8 set in the design and registers 18, 19,
Numerical values stored in registers 20, 21, 28, 29, and 30 are classified and written according to the number of steps it takes for the type to reach the printing position, and the rotational direction value to be stored in register 32 is also written. It is.

The RAM stores the above numerical values read from the ROM, and after printing is completed, registers 28, 29,
Store the revised numbers from 30.

When the printer is powered on, the control unit 46 reads out each numerical value written in the ROM and writes it to a predetermined address in the RAM. Next, when the number of steps to the print position for the desired type is detected, the numerical value at each address corresponding to this number of steps is read from the RAM and sent to the pulse count unit 8 and each register.

When the printing of the desired type is completed, the revised numerical values are read from the registers 28, 29, and 30.
Sent to RAM and written to original address.
When performing a printing operation with the same number of steps again, the revised numerical values are read out from the RAM and stored in the registers 28, 29, and 30, respectively.

In this case, the RAM addresses to which the numerical values stored in registers 28, 29, and 30 are written are made different depending on the number of movement steps of the type to the printing position, and the other values are written regardless of the number of movement steps. A common address is used, and each time the number of movement steps changes, the preset value of the pulse count unit 8 and the registers 18, 19, 2 are changed.
The numerical values stored in 0 and 21 may be read from the ROM and written to the above-mentioned common address in the RAM. In addition, the RAM includes registers 28,
The preset values of the pulse count unit 8 and the values of the registers 18, 19, 20, 21, and 32 are directly read from the ROM and stored in the pulse count unit and registers 18 to 32, respectively. 32 may be supplied.

The control unit 46 controls the series of operations described above, but also resets the pulse count unit 8 and each register immediately after the power is turned on and before starting each printing operation.

Next, the operation of this embodiment will be explained assuming that the number of steps required for printing is 19. In this case, as in the prior art described above, as shown in FIG. 5, the first step changes from the low speed mode L _p to the high speed mode H _i , and the eighth step changes from the high speed mode H _i to the hold mode H _p .
It is assumed that the hold mode H _p is switched to the low speed mode L _p at the 12th step, and further to the hold mode H _p in which homing control is performed at the 17th step.

Now, when a device (not shown) determines that the number of steps required to move the type is 19, the control unit 46 reads out each numerical value corresponding to this number of steps from the memory 45, and presets the value 19 in the pulse counter 8. and at the same time register 1
Predetermined delay values D ₂ and D ₁ are stored in registers 8 and 28.
9, 20, 21 are predetermined reference speed values Ro, R _A , R _B
However, the value 11 is stored in the register 29, the value 20, which is larger than the preset value 19 of the pulse count unit 8, is stored in the register 30, and the value for setting the rotation direction of the stepping motor 6 is stored in the register 32. be done.

In this state, the hold pulse pattern generator 9 generates the hold pulse pattern H, the comparator 33 compares the count value M of the pulse count unit 8 with the reference value 2, and the comparator 34 compares the count value M with the register 29. The number N stored in ₁
(=11), and the comparator 35 outputs the count value M
is the numerical value N ₁ (=11) stored in register 29
and the numerical value N ₂ (=20) stored in register 30
Comparator 3
6 compares the count value M and the numerical value N ₂ (=20) stored in the register 30.

Here, since the count value M is 19, N ₂ (=20)>M (=19)> _N1 (=11)>2, and as mentioned earlier, the outputs of the comparators 33 and 35 The level is "L" and the output levels of the comparators 34 and 36 are "H". Therefore, and gate 1
6 and 40 are in a conductive state, and the AND gate 39 is in a cutoff state, so that the falling pulse signal a from the falling detector 13 can be supplied to the hold pulse pattern generator 9, and the “H” level of the comparator 36 is The output signal is supplied to the pulse converter 11 as a low speed command signal l _p . For this purpose, the pulse converter 11 converts the hold pulse pattern H to generate a low-speed drive signal C, and the stepping motor 6 rotates at a low speed to set the low-speed mode _Lp .

When the stepping motor 6 rotates one step and the falling edge detector 13 generates one falling pulse, the count value M of the pulse count unit 8 is
It becomes 18. At the same time, the pulse count unit 8 sends a command signal to the control unit 46, which causes the control unit 46 to return the value 20 stored in the register 30 to the memory 45, and further read out the value 7 from the memory 45. Store in register 30. Therefore, the number N ₂ is 7.

Therefore, M>N ₁ (=11)>N ₂ (=7)>2, and the output level of the comparator 36, which was "H", becomes "L" and the AND gate 39 becomes conductive. For this purpose, the "H" output signal of the comparator 34 is supplied to the pulse converter 11 as a high-speed command signal h _i . As a result, the high speed mode H _i is set and the stepping motor 6 is accelerated and rotates at a high speed.

Along with the high-speed rotation of the stepping motor 6, a falling pulse signal a is generated from the falling detector 13, and is supplied to the hold pulse pattern generator 9, as well as to the speed detection unit and the time/speed converter 15. The actual speed value R is generated from .

Then, the pulse count unit 8 subtracts the value by 1 each time a falling pulse is supplied, and when N ₁ (=11) ≧ M > N ₂ (= 7) > 2, it is determined that the pulse count is "H" until now. The output level of the comparator 34 becomes "L", and the output level of the comparator 35 becomes "L" instead.
The output level becomes "H". As a result, the hold command signal h _p is supplied to the pulse converter 11 and the hold mode H _p is set, and the stepping motor 6 is braked by the reverse torque and rotates at a reduced speed.

At the same time as the output level of the comparator 35 rises, the comparator 23 operates and compares the reference speed value R _A stored in the register 20 with the actual speed value R. Based on this comparison result, the arithmetic unit 26 generates an added value of +1, 0, or -1, and registers this added value after at least one step of the hold mode H _p has elapsed. 29 to modify the value stored there (11 in this case).

As the stepping motor 6 decelerates, the pulse count unit 8 further subtracts, and when N ₁ (=11)>N ₂ (=7)≧M>2, the comparator 35, which had been at “H”, The output level of the comparator 36 becomes "L", and instead, the output level of the comparator 36, which was previously "L", becomes "H".
Therefore, the low speed mode L _p is set, and the stepping motor 6 rotates at a low speed.

At the same time that the output level of the comparator 36 becomes "H", the comparator 24 operates to compare the reference speed value R _B stored in the register 21 with the actual speed value R. Then, similarly to the register 29, depending on these differences, after at least one step in the low speed mode L _p has passed, the numerical value N ₂ stored in the register 30 is changed.
(In this case, 7) is corrected by adding +1, 0, or -1.

When the stepping motor 6 further rotates and 2≧M, the output level of the comparator 33, which was previously “L”, becomes “H”, and the “H” output signal is passed through the OR circuit 41 as a hold command signal. It is supplied to the pulse converter 11 as h _p , and also turns off the AND gate 40. As a result, the hold mode H _p is set and the stepping motor 6
rotates at a reduced speed. At the same time, the output signal f is inverted by the inverter 44 to cut off the AND gate 16, thereby blocking the passage of the falling pulse signal a.

Furthermore, the output signal f of "H" is transmitted to the register 28.
The signal is supplied to the programmable delay circuit 37 with a delay amount T ₁ (FIG. 7) corresponding to the delay value D ₁ stored in the delay signal D _{1 , and is supplied to the hold pulse pattern generator 9 through the OR circuit 17 as a delay signal d 1} . Further, this delay signal d ₁ is supplied to a programmable delay circuit 38 with a delay amount T ₂ (FIG. 7) according to the delay value D ₂ stored in the register 18, and the delay signal d 1 is
It is supplied to the hold pulse pattern generator 9 through the OR circuit 17 as d ₂ . As a result, the hold pulse pattern generator 9 outputs delayed signals d ₁ ,
A hold pulse pattern whose phase is synchronized with the rising edge of _d2 is obtained.

Therefore, a reverse torque is generated in the stepping motor 6 according to the delay amount of the programmable delay circuits 37 and 38, and the brake is applied to decelerate and finally stop.

When the comparator 31 detects that the count value M of the pulse count unit 8 has become zero, the comparator 22 operates to compare the reference speed value Ro stored in the register 19 with the actual speed value R. do. The arithmetic unit 25 calculates +1,
Either 0 or -1 is generated, and the delay value _D1 stored in the register 28 is modified with this value.

When the printing operation is completed, the control unit 46
The corrected values stored in the registers 28, 29, and 30 are returned to the memory 45 and prepared as numerical values for the next printing of the same step number 19.

By the way, it is not preferable to print using the numerical values written in the ROM of the memory 45 that should be stored in the registers 28, 29, and 30 as they are because there is a large possibility that an error will occur. Therefore, in order to eliminate this error, after turning on the power, the printer is put into a test run state for a predetermined period of time, and the printer is operated a predetermined number of times for each movement step number, and the delay value D ₁ to be stored in the register 28 is set in the registers 29 and 30. The numbers N ₁ and N ₂ to be stored are respectively modified so that these modified numbers are used for the first printing operation of each movement step.

As explained above, according to the present invention, even if an error occurs in the rotational speed of the stepping motor, the braking action in the hold mode, which is the final mode, is adjusted so that the rotational speed in the hold mode is a specified value. As a result, the accuracy of the rotational angle of the stepping motor is improved, and it is possible to provide a stepping motor drive circuit with excellent functions without the drawbacks of the prior art described above.

[Brief explanation of drawings]

Fig. 1 is a schematic perspective view showing an example of a type wheel drive mechanism in a printer, Fig. 2 is a block diagram showing an example of a conventional stepping motor drive circuit, and Fig. 3 is an example of a stepping motor driving method. Figures 4a, b, and c are curve diagrams showing the torque in each mode of the stepping motor. Figure 5 explains the operation of the drive circuit in Figure 2 for the four-phase excitation stepping motor. FIG. 6 is a block diagram showing an embodiment of the stepping motor drive circuit according to the present invention, and FIG. 7 is a timing chart for explaining the operation of the drive circuit of FIG. 6 during the homing period. be. 5...Sensor, 6...Stepping motor, 7
...Drive circuit, 8...Pulse count unit, 9...Hold pulse pattern generator, 11
...Pulse converter, 14...Pulse interval detector,
15... Time/speed converter, 16... AND gate, 17... OR circuit, 18, 19... Register, 22... Comparator, 25... Arithmetic unit, 28...
Registers, 31, 33... Comparators, 37, 38...
...Programmable delay circuit, 44...Inverter.

Claims (1)

[Scope of utility model registration request] A pulse signal from a sensor that detects the rotational phase of the stepping motor is supplied to a hold pulse pattern generator to generate a hold pulse pattern phase-synchronized with the pulse signal, and the hold pulse pattern is converted and processed to perform the stepping motor. A stepping motor drive circuit configured to form drive signals for each mode of the motor includes a pulse count unit that counts pulse signals from the sensor, and a final mode of the stepping motor based on the count number of the pulse count unit. a first comparator for detecting the start point of the hold mode, a first delay device for delaying the output signal of the first comparator, and a second delay device for delaying the output signal of the first delay device. a switching device for supplying the output signals of the first and second delay devices to the hold pulse pattern generator in place of the pulse signal according to the output signal of the first comparator; a second comparator for detecting the end point of the hold mode from the count number of the counting unit; and an actual speed value representing the rotational speed of the stepping motor at the time the second comparator detects the end of the hold mode. a third comparator that compares the speed with a preset reference speed value;
a register storing a delay value that determines the amount of delay of the delay device and is corrected according to the comparison result of the third comparator; The hold pulse pattern from the generator is phase-synchronized with the output signals of the first and second delay devices, and the actual speed value of the stepping motor at the end of the hold mode becomes the reference speed value. A stepping motor drive circuit characterized in that it is configured as follows.