JPH0777088A - Speed control method for step motor - Google Patents

Abstract

PURPOSE:To improve durability through reduction of a maximum speed during first drive after making of a power source and to improve responsiveness through execution of drive at a further high drive speed by means of a motor load after grease is spread. CONSTITUTION:An accelerator pedal step-on amount signal outputted from an accelerator stroke sensor 23 is inputted to a CPU 18 to calculate the target step position of a step motor 4. A voltage value into which the voltage of a battery 21 is branched by a branch circuit 22 is A/D-converted and it is then decided whether a first decision flag is zero. When the first decision flag is zero, a maximum drive frequency corresponding to a current voltage value is set based on a drive map A. When the first decision flag is not zero, based on a drive map B stored in an ROM 13, a maximum drive frequency corresponding to a current voltage value is set. The drive map A has a maximum drive frequency reduced to a value lower than that of the drive map B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor speed control method for opening and closing a throttle valve of an engine.

[0002]

2. Description of the Related Art Conventionally, a speed control device for this type of stepping motor is disclosed in, for example, Japanese Patent Laid-Open No. 61-138850. This device follows the decrease in the battery voltage (power supply voltage) of the step motor and lowers the maximum drive speed for driving the stepping motor. This prevents out-of-step caused by a reduction in the driving force of the step motor. That is, conventionally, the maximum driving speed by the power supply voltage of the step motor is determined so that the maximum load can be driven in consideration of the low temperature of the throttle valve on the load side, the driving direction, and the like.

[0003]

By the way, when the step motor is driven for the first time after the ignition switch is turned on, the grease distribution in the step motor is not uniform, so that the load is large and the grease is not discharged after the second time. The load is small because it spreads over the entire axis. However, in the past, the maximum driving speed was determined according to the battery voltage (power supply voltage) so that the first driving can always be performed. Has not been used. Therefore, there is a problem that the responsiveness corresponding to the depression amount of the accelerator pedal is lacking.

The object of the present invention is to improve the durability of the step motor by reducing the maximum drive speed at least during the initial drive after the power is turned on, and increase the maximum drive speed thereafter, thereby increasing the motor load, etc. Therefore, it is possible to provide a step motor speed control method capable of improving responsiveness because the method can be driven at a higher drive speed.

[0005]

To achieve the above object, in the present invention, a drive target step position of a step motor for obtaining a throttle opening based on an accelerator pedal depression amount signal is calculated, and A method for controlling the speed of a throttle step motor, which controls the throttle opening by driving the step motor at a speed that does not exceed the maximum drive speed of the step motor that is set to prevent stepping of the step motor to a target step position. The maximum drive speed of the step motor is set so that the maximum drive speed when driving the step motor for the first time after the engine is started is higher than the maximum drive speed when driving the step motor after the second time after the engine is started. This is the summary.

[0006]

With the above structure, when the step motor is driven for the first time after the engine is started, the maximum drive speed is set higher than the maximum drive speed when the step motor is driven for the second time after the engine is started.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will now be described with reference to FIGS.
This will be described in detail with reference to FIG.

FIG. 2 shows the configuration of the throttle actuator. The throttle valve for adjusting the intake air amount of the engine is composed of a throttle body 1, a butterfly valve 2 and a rotatable shaft 3 to which the butterfly valve 2 is fixed. ing. The shaft 3 is rotatably supported by the throttle body 1 by a bearing (not shown).
A gear 4 is fixed to one end of the shaft 4, and is meshed with a gear 6 fixed to one end of a shaft 5 of the step motor 4. When a drive signal is output to the step motor 4, the step motor 4 performs a step operation, the shaft 5 is rotated in association with the movement, and the shaft 3 is rotated via the gears 6 and 7.
Is rotated. As a result, the butterfly valve 2 is rotated,
The cross-sectional area of the air passage of the throttle body 1 changes. The gears 6 and 7 are gears having a speed reduction ratio of ½, and when the shaft 5 of the step motor 4 rotates 180 degrees, the shaft 3 becomes 9
It is designed to rotate 0 degrees.

Next, a drive device for driving the step motor 4 will be described. FIG. 1 shows a block diagram of the drive unit. One-chip microcomputer 11 is RAM
12, ROM 13, input / output buffer 14, A / D converter 15, programmable timer 16, interrupt control circuit 17, and CPU 18.

The RAM 12 is for temporarily storing calculation results and data, and the ROM 13 stores a control program and the like. The input / output buffer 14 is for inputting / outputting signals between the microcomputer 11 and the outside, and the A / D converter 15 converts an analog signal from the outside into a digital signal. The interrupt control circuit 17 is a circuit for causing the CPU 18 to perform an interrupt process when an interrupt request is generated. CPU 18 is R as a storage means
Arithmetic processing is performed based on the control program stored in the OM 13.

The clock generator 19 supplies a reference clock pulse to the one-chip microcomputer 11 and serves as a reference timing signal for operation and a reference clock source for the programmable timer 16. The constant voltage power supply 20 stabilizes the power supply voltage from the battery 21 to 5V and supplies it to the one-chip microcomputer 11 and the clock generator 19. The voltage of the battery 21 is divided into 1/4 by the voltage dividing circuit 22 and input to the A / D converter 15. Also, A
An accelerator pedal depression amount signal from the accelerator stroke sensor 23 is input to the / D converter 15. The drive signal from the microcomputer 11 is output to the step motor 4 via the drive circuit 24. A voltage is applied to the step motor 4 from the battery 21.

FIG. 4 is an electrical equivalent circuit diagram of the drive circuit 24 and the step motor 4. In the step motor 4, four coils 26a to 26d are wound around a stator. The coils 26a and 26b, and the coils 26c and 29d are bifilar wound and connected in opposite phases to each other. The resistors 27a to 27h are resistors for determining the current values of the coils 26a to 26d, and the resistors 27a, 27c,
27e and 27g have the same resistance value and resistors 27b, 27d and 2
7f and 27h also have the same resistance value. The transistor 28a has a collector connected to one end of the resistor 27a and a base connected to the terminal 30a via the resistor 29a.
A diode 31a for absorbing the counter electromotive force of the coil 26a between the collector and the emitter of the transistor 28a to prevent the transistor 28a from being reverse biased.
Are connected. Similar connections are made between resistors 29b-29h and terminals 30b-30h and transistors 28b-29.
Diodes 31b to 31 are provided between the collector and the emitter of h.
h are connected to each other. The positive terminal of the battery 21 is connected to the terminal 32, and the negative terminal of the battery 21 is connected to the terminal 33.

The terminals 30a to 30h are connected to the input / output buffer 14 of the one-chip microcomputer 11, and
V or 0V is applied. For example, 5V at the terminal 30a
Is applied, the transistor 28a turns on and the resistor 2
A current flows through the coil 26a through the terminal 7a, while the terminal 3
When 0V is applied to 0a, the transistor 28a is cut off and no current flows through the coil 26a. By controlling the combination (excitation pattern) of the voltages applied to these terminals 30a to 30h by the one-chip microcomputer 11, the rotation of the step motor 4 is controlled.

FIG. 3 is a timing chart showing the relationship between the voltage waveform applied to the terminals 30a to 30h and the step position. This control sequence is generally referred to as "double 1-2 phase excitation", and by switching the excitation pattern according to this sequence, the shaft of the step motor 4 moves about 0.
It rotates by 45 degrees (that is, about 0.225 degrees for the shaft 3). This control sequence repeats the same state every 16 steps. The forward direction of this control sequence is the closing direction of the throttle valve.

For example, when the time for switching from step position 2 to step position 3 shown in FIG. 3 (that is, the cycle T) is changed, the rotation speed of the shaft 5 of the step motor 4 (hereinafter referred to as drive speed) changes, Therefore, the opening speed of the throttle valve changes. When the driving frequency is the reciprocal of the period T, the driving frequency is f = 1 / T, and the unit is p
ps (pulse per second). Here, when a load torque is applied to the shaft 5 of the step motor 4, the torque is rotated up to a certain torque in synchronization with the step switching, but when the torque exceeds the limit torque, the rotation cannot be performed in synchronization. This is called step-out, but the upper limit of the load torque that can rotate without causing step-out changes depending on the power supply voltage (battery voltage) and the drive frequency as shown in FIG. That is, it changes depending on the power supply voltage and the driving speed.

The shaft 5 of the step motor 4 is subjected to rotational torque and friction torque due to the air flow,
The maximum value is 0.1 Nm (Newton meter). Therefore, when the drive frequency is set to 3000 pps at the maximum, when the battery voltage becomes about 11 V or less, the step motor 4 loses step and becomes uncontrollable. However, in this embodiment, the upper limit of the drive frequency can be controlled by the drive map A and the drive map B stored in the ROM 13 as shown in FIGS. I am trying. The driving frequency and the driving speed are in a proportional relationship.

The drive map A of FIG. 6A is a map used when the step motor 4 is driven for the first time after the ignition switch is turned on. The drive map B of FIG. 6B is a map used when the step motor 4 is driven after the ignition switch is turned on for the second time and thereafter. The drive map A is set so that the maximum drive frequency is smaller than that of the drive map B. That is, when the step motor 4 is driven for the first time after the ignition switch is turned on, the grease of the bearing that supports the shaft 3 of the step motor 4 is not uniform, and as a result, the load at the time of rotation increases, so the maximum drive frequency Is set small. And
The smaller the maximum drive frequency, the slower the maximum drive speed of the step motor 4, and the higher the maximum drive frequency, the faster the maximum drive speed of the step motor 4.

Next, the operation control procedure of the step motor 4 configured as described above will be described. 7 to 10
Shows a flowchart showing the operation control procedure of the drive device of the step motor 4. 7 is a main processing routine, and FIG. 8 is an interrupt processing routine. The main processing routine is always executed, and when the interrupt control circuit 17 makes an interrupt, the interrupt processing routine is executed.

In the main processing routine, first, the accelerator pedal depression amount signal output from the accelerator stroke sensor 23 in step 101 is A / D converted by the A / D converter 15.
D converted. In step 102, the converted digital signal is fetched by the CPU 18 to calculate the target step position of the step motor 4 which determines the target throttle valve opening, and stores this value in the RAM 12. The relationship between the throttle valve opening and the step position is that the valve is fully closed at 0 step and the valve is fully opened at 360 step. Next step 10
In 3, the voltage value obtained by dividing the voltage of the battery 21 by the voltage dividing circuit 22 is A / D converted.

In step 104, it is determined whether the initial determination flag is 0. That is, it is determined whether or not it is the first drive after the ignition switch is turned on. The initial determination flag is reset to 0 when the ignition switch is turned on and the apparatus is initialized before entering the main processing routine. Therefore, first, the process proceeds to step 105. RO in step 105
Based on the drive map A stored in M13, the maximum drive frequency corresponding to the voltage value at that time is set, and step 1
In 07, the initial determination flag is set to 1 and the process proceeds to step 101. From the next time onward, the main processing routine proceeds to steps 101 to 104, NO is determined in step 104, and ROM 1 is determined in step 106.
Based on the drive map B stored in 3, the maximum drive frequency corresponding to the voltage value at that time is set, and step 101
Return to. Therefore, the main processing routine executes the above-mentioned step 1 based on the accelerator pedal depression amount signal which arrives every moment.
01 to step 107 are repeatedly executed.

Therefore, the maximum drive frequency with respect to the battery voltage is calculated by the drive maps A and B shown in FIG. 6 (a) or 6 (b). Then, the driving of the step motor 4 is executed by an interrupt processing routine.

Next, a case where the main processing routine is temporarily suspended and the interrupt processing routine is performed will be described. When an interrupt processing request is issued from the interrupt control circuit 17 shown in FIG. 1 to the CPU 18, the CPU 18 suspends the main processing routine and shifts to the interrupt processing routine. This interrupt processing request is generated when the count overflow signal from the programmable timer 16 is input to the interrupt control circuit. The programmable timer 16 keeps counting up at αμs as a count clock, and generates a count overflow signal when the value exceeds a predetermined value.

In the interrupt processing routine, first in step 201, the timer initial value is obtained from the drive frequency stored in the RAM 12 by referring to the table stored in the ROM 13. In the table, the timer initial value is set corresponding to each drive frequency such that the timer initial value increases as the drive frequency increases.
Next, the timer initial value obtained in step 202 is set in the programmable timer 16, and the timer 16 starts counting up from this set value. For example, if the set value is 125, counting up is started from 125, and when a predetermined value (256 in this embodiment) is exceeded, an overflow signal is generated and an interrupt processing request is generated.

On the other hand, in step 203, the RAM 12
The excitation pattern shown in FIG. 3 stored in the ROM 13 is obtained from the current step position stored in the. For example, if the current step position is 8 shown in FIG. 3, the terminal voltages of the terminals 30a to 30h shown in FIG. 4 are 0, 0,
5, 5, 0, 0, 0, 0 (V). Next step 20
In step 4, the excitation pattern is output from the input / output buffer 14 to the drive circuit 24. As a result, a new excitation pattern is obtained and the shaft 5 of the step motor 4 rotates one step (about 0.45 degrees). If the current step position is the same as the previous step position, the step motor 4
Does not rotate.

Next, in step 300, the next step position is calculated from the current step position stored in the RAM 12 and the target step position obtained in step 102 (that is, this step position is executed next time by this interrupt processing routine). The "current step position" at the time) is calculated. Details of this step 300 will be described later. After this step 300, this interrupt processing routine ends. When this interrupt processing routine ends, the suspended main processing routine is restarted.

As described above, when the count value of the timer 16 reaches the predetermined value, the count value returns to the set value, and when the count value reaches the predetermined value again, the overflow signal is generated again, and the interrupt control circuit 17 requests interrupt processing again. Is issued and the process proceeds to the interrupt processing routine again. Therefore, in the cycle T at which the interrupt processing is started, the set value (timer initial value) set in the timer 16 in step 202 is set to Ti.
If m, then T = (256−Tim) × α + T0. In the above equation, T0 represents a loss time from the occurrence of the timer overflow to the execution of the interrupt processing routine and the next timer setting. Since the excitation pattern at each step position is output in step 204 based on this cycle T, T in FIG. 3 becomes this value, and the reciprocal thereof becomes the drive frequency of the step motor 4.

Next, regarding step 300, FIG. 9 and FIG.
It will be described according to the flowchart of No. 0. Step 302
Then, the target step position stored in the RAM 12 is compared with the current step position based on the excitation patterns output in steps 203 and 204. When the target step position is equal to the current step position, the current drive frequency is checked next in step 303, and if the current drive frequency is the lowest drive frequency stored in the ROM 13 in advance, the process ends. That is, the next step position is the same as the present step position, and the step motor 4 is stopped. When the current drive frequency is not the lowest drive frequency stored in the ROM 13 in advance, the drive frequency is decreased by a predetermined value in step 304 and the RAM 1 is set as the next drive frequency.
Store in 2. Then, in step 305, the current step position is changed by one step (increase or decrease) so that the step motor 4 rotates in the same direction as the current rotation direction of the step motor 4,
The next step position is stored in the RAM 12 and the process ends. That is, if the rotation direction flag is set in the opening direction of the throttle valve, it is increased by one step, and if it is set in the closing direction, it is decreased by one step.

On the other hand, if the current step position and the target step position are not equal in step 302, it is determined in step 306 whether the target step position seen from the current step position is the same as the current rotation direction (determined by the rotation direction flag). To determine. If the rotation directions are opposite, it is determined in step 313 whether the drive frequency is the lowest drive frequency. If it is determined that the drive frequency is the lowest drive frequency, the rotation direction flag is inverted in step 314, and the process ends. That is, it stops and changes only the rotation direction flag. If it is determined in step 313 that the drive frequency is not the minimum drive frequency, the process proceeds to step 304 to reduce the drive frequency by a predetermined value.

On the other hand, when it is determined in step 306 that the current rotation direction is the same as the rotation direction of the target step position, the difference between the target step position and the current step position is calculated in step 307, and the ROM 13 is stored in the ROM 13 based on the difference. The target drive frequency is obtained from the stored table. Since the current rotation direction is the same as or opposite to the target step position, the difference is obtained as an absolute value, and the difference value on the table is also set as an absolute value. In step 308, the target drive frequency is compared with the current drive frequency. If the current drive frequency is equal to or higher than the target drive frequency, the process proceeds to step 304 to lower the drive frequency by a predetermined value.

On the other hand, when the current drive frequency is less than the target drive frequency in step 308, the current drive frequency is compared with the target drive frequency in step 309, and the current drive frequency is smaller than the target drive frequency by a predetermined value a. Or not. If it is determined that the predetermined value a is smaller than the target drive frequency, the current drive frequency is compared with the maximum drive frequency stored in the RAM 12 in step 315. If the current drive frequency is higher than the maximum drive frequency in step 315, the process proceeds to step 304 to lower the drive frequency by a predetermined value.

On the other hand, if it is determined that the current drive frequency is less than or equal to the maximum drive frequency, step 30 is performed to change the step position by one step in the same direction as the current rotation direction.
Go to 5. That is, the same drive frequency is used next time. If it is determined in step 309 that the current drive frequency is not smaller than the predetermined value a, in step 310 the current drive frequency is compared with the maximum drive frequency. If they are equal in step 310, the process proceeds to step 304 to change the current step position by one step in the same direction as the current rotation direction without changing the drive frequency. Step 31
If it is determined that they are not equal to each other and that the current drive frequency is higher than the maximum drive frequency in step 311, the process proceeds to step 304. If it is determined in step 311 that the current drive frequency is lower than the maximum drive frequency, the drive frequency is increased by a predetermined value and stored in the RAM 12, and the process proceeds to step 305.

As described above, in this embodiment, since the maximum driving frequency is lowered when the battery voltage drops,
The driving frequency will also decrease. Further, when the step motor 4 is driven for the first time after the ignition switch is turned on, the maximum drive frequency is calculated by the drive map A in which the maximum drive frequency is smaller than the drive map B. Therefore, the load applied to the step motor 4 does not increase even if the grease is driven at the maximum drive frequency when the grease distribution in the step motor 4 is non-uniform during the initial drive. Therefore, the durability of the step motor 4 can be improved.

Further, since the grease spreads over the entire shaft and the load is reduced from the second time onward, the maximum driving frequency is raised, so that the responsiveness according to the depression amount of the accelerator pedal can be improved.

The present invention is not limited to the above-described embodiment. For example, in the above-mentioned embodiment, the drive map A is referred only at the time of the first drive, but at least at the time of the first drive, the following several times are followed. The drive map A may be referred to during driving.

[0035]

As described above in detail, according to the present invention, the durability is improved because the maximum driving speed is small at least during the first driving after the power is turned on. After the grease has spread, it can be driven at a higher driving speed due to a motor load or the like, so that an excellent effect that the response can be improved is exhibited.

[Brief description of drawings]

FIG. 1 is an electric block diagram of a drive device for driving a step motor according to an embodiment of the present invention.

FIG. 2 is a front view of a step motor.

FIG. 3 is a timing chart showing a relationship between an applied voltage and a step position.

FIG. 4 is an electric circuit diagram of a step motor and a drive circuit.

FIG. 5 is a graph showing the relationship between load torque and drive frequency.

6A is a drive map A of the maximum drive frequency and the battery voltage, and FIG. 6B is a drive map B of the maximum drive frequency and the battery voltage.

FIG. 7 is a flow chart showing an operation control procedure of a drive device.

FIG. 8 is a flowchart showing an interrupt routine.

FIG. 9: Step 300 in the interrupt processing routine processing
2 is a detailed flowchart of FIG.

FIG. 10 is a detailed flowchart of step 300 in the interrupt processing routine processing.

[Explanation of symbols]

1 ... Throttle body, 3 ... Shaft, 4 ... Step motor, 5 ... Shaft, 11 ... One-chip microcomputer, 12 ... RAM, 13 ... RO as storage means
M, 18 ... CPU, 21 ... Battery, 22 ... Voltage dividing circuit.

Claims (1)

[Claims] 1. A driving target step position of a step motor for obtaining a throttle opening based on an accelerator pedal depression amount signal is calculated, and a step motor of a step motor determined to prevent step-out of the step motor is moved to the target step position. A method of controlling the speed of a throttle step motor for controlling a throttle opening by driving the step motor at a speed that does not exceed the maximum drive speed, wherein the maximum drive speed of the step motor is the first to drive the step motor after engine startup. The method of controlling the speed of a step motor is characterized in that the maximum drive speed for the step motor is set to be higher than the maximum drive speed for driving the step motor after the second engine start.