JP2003125599A - Indicating instrument for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an indicating instrument for vehicle in which the accuracy for deciding arrival of a pointer to a reset to zero position is enhanced by making a judgment based on a voltage being induced in the field winding of a stepping motor in the process for driving the pointer of the stepping motor to the reset to zero position and rotation of the stepping motor to a specified electrical angle, and repeating judgment based on the induced voltage in case of erroneous judgment. SOLUTION: A microcomputer 60 determines that a zero position is detected if a voltage induced in the field winding is not higher than a specified level when the field winding 32 or 33 of reset to zero voltage is interrupted from the rest to zero voltage during rotation of a stepping motor M based on the input to the field winding. A decision is made that the determination of zero position detection is correct if a decision is made that the phase angle of the reset to zero voltage advanced to an electrical angle corresponding to the zero level of the reset to zero voltage. Otherwise, determination of detection of the zero position and correctness thereof is repeated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle indicating instrument which employs a step motor as a pointer driving source.

[0002]

2. Description of the Related Art Conventionally, in this type of vehicle indicating instrument, a stepping motor and a reduction gear train driven by the stepping motor are arranged on the back side of a scale plate. Then, in the reduction gear train, when the input stage gear is driven by the step motor, the output stage gear decelerates and rotates the pointer along the surface of the dial through the pointer shaft. As a result, the indicating instrument gives an instruction for analog input with the pointer.

Here, when the pointer returns to the zero position (zero return position) of the scale on the scale board, the indicator instrument stops the rotation of the output stage gear by its stopper mechanism, and the pointer at the zero position. By stopping, the reference position of the pointer is set.

[0004]

By the way, in the above indicating instrument, in order to detect that the pointer has returned to the zero return position,
By using the induced voltage generated in the field winding of the step motor in the process of driving the step motor with an AC zero-reset voltage, when the induced voltage falls below a predetermined threshold voltage, the pointer will move to the zero-reset position. It is determined that it has reached.

However, even if the pointer has not actually reached the zero-reset position, for example, if there is noise on the field winding, it is also determined that this noise is below the threshold voltage, and the pointer is zero-reset. This causes a problem of erroneously determining that the position has been reached.

On the other hand, a predetermined rotation angle corresponding to the zero-reset position of the step motor is set in advance as an electrical angle, and the actual rotation angle of the step motor reaches the above-mentioned predetermined rotation angle in electrical angle. It is possible to judge that the pointer has reached the zero-reset position also when doing.

However, as described above, even if the predetermined rotation angle is also used in determining that the pointer has reached the zero-reset position, if the erroneous determination due to noise is a prerequisite as described above. Cannot, after all, eliminate the erroneous determination that the pointer has reached the zero-reset position.

In view of the above, the present invention provides a vehicle indicating instrument that uses a step motor as a drive source for a pointer to determine whether the pointer reaches the zero return position. In the process of driving to the zero-reset position, the induced voltage generated in the field winding of the step motor and the rotation of the step motor to a predetermined rotation angle are used. By repeating, it is intended to improve the accuracy of determining the arrival of the pointer at the zero-reset position.

[0009]

In order to solve the above-mentioned problems, the vehicle instrument according to the invention as defined in claim 1 is a scale portion in which an analog value is scaled in a substantially arc shape from a lower limit scale value to an upper limit scale value. A scale plate (10) having (10a), a pointer (50) supported so as to rotate along the surface of the scale plate, and a field winding that receives an AC drive signal and generates an AC magnetic flux. A step motor (M) including a stator (Ms) including (32, 33) and a magnet rotor (Mr) rotatably supported in the stator and rotating according to the AC magnetic flux; The deceleration gear means (G) that decelerates and rotates in response to the rotation, and rotates the pointer accordingly. When the pointer reaches the zero return position corresponding to the lower limit scale value of the analog value, the deceleration rotation of the deceleration gear means is stopped. Stopper and means (ST), a driving signal input means for inputting to the field winding of the drive signal in response to an input representative of the analog value (SV) (70,80,170),
Zero return signal input means (70, 80, 100, 13) for inputting an AC zero return signal to the field winding when returning the pointer to the zero return position.
1, 133, 133a, 134, 134a, 135, 1
35a).

In the indicating instrument, after the input of the zero-return signal to the field winding, the storage means (90) which stores beforehand a predetermined electrical angle when the zero-return signal advances to the phase angle corresponding to the zero level. ), And the field winding is interrupted from the zero signal during rotation of the step motor based on the input of the zero signal to the field winding by the zero signal input means, and First determination means (132a to 132) for determining zero position detection when the induced voltage becomes equal to or lower than a predetermined low voltage that represents the stop of the deceleration rotation of the reduction gear means by the stopper means.
d, 133c to 133f, 134c to 134f, 1
35c to 135f) and the detection of the zero position by the first determining means, the phase angle of the zero return signal corresponds to the predetermined electrical angle and the zero level of the zero return signal before and after the predetermined electrical angle. Second judging means (240) for judging whether or not the electric angle is reached, and the second judging means corresponds to the predetermined electric angle and the zero level of the zero return signal before and after the electric angle. When it is determined that the vehicle has proceeded to one of the corners, a third determination means (140) that determines that the determination of the zero position by the first determination means is correct and a determination of the zero position by the third determination means. When it is determined that the determination is not correct, it is determined whether or not the input of the zero return signal to the field winding by the zero return signal input means and the determination by the first and second determination means have been repeated a prescribed number of times. Means (150) and the fourth judgment hand There when it is determined that no repetition predetermined number of times, and repeating the determination by the input and the first and second determination means to the field winding of the zero-reset signal by zero reset signal input means again.

As described above, in determining the arrival of the pointer at the zero-reset position, the induced voltage generated in the field winding of the step motor and the electrical angle of the step motor during the process of driving the step motor to the zero-reset position. When the erroneous determination is made by utilizing the rotation to the predetermined rotation angle at, the determination by the induced voltage can be repeated to improve the accuracy of determining the arrival of the pointer at the zero-reset position.

According to a second aspect of the invention, in the first aspect of the invention, the third determining means inputs the zero return signal to the field winding by the zero return signal input means, and While the determinations by the first and second determining means are repeated a prescribed number of times, the second determining means has advanced to either the predetermined electrical angle or the electrical angle corresponding to the zero level of the zero-return signal before and after this electrical angle. When it is determined that the zero position has been detected, the fourth determination means inputs the zero return signal to the field winding by the zero return signal input means and the first and second determination means. After the determination by is repeated a prescribed number of times, the detection of the zero position is determined to be abnormal. Thereby, the function and effect of the invention described in claim 1 can be further improved.

The reference numerals in parentheses of the above-mentioned means indicate the correspondence with the specific means described in the embodiments described later.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of an indicating instrument for a passenger vehicle according to the present invention. The indicating instrument is provided as a vehicle speedometer on an instrument panel provided in a passenger compartment of the passenger vehicle.

As shown in FIGS. 1 and 2, this indicating instrument is provided with a graduation plate 10, and the graduation plate 10 is provided with a substantially arc-shaped graduation portion 10a. Here, the scale portion 10a is formed with a plurality of scales such that the vehicle speed is scaled from a lower limit scale value (vehicle speed 0 km / h) to an upper limit scale value (vehicle speed 180 km / h). The graduation plate 10 is attached to the opening 21a formed in the bottom wall 21 of the ring-shaped dial plate 20 from the back side thereof.

As shown in FIG. 1 or 2, the indicating instrument has a rotating inner unit 30, a wiring board 40 and a pointer 50. The rotating inner unit 30 includes an inner unit main body 30a and a pointer shaft 30b. The inner unit body 30a is a scale plate 1
It is assembled to the wiring board 40 from the back surface side at a position corresponding to 0. The inner unit main body 30a includes a two-phase step motor M (see FIGS. 3 to 5), a reduction gear train G (see FIG. 3), and a stopper mechanism ST (see FIG. 3) in a casing 30c (see FIG. 2). The internal unit main body 30a is supported coaxially with the output stage gear 34 (described later) of the reduction gear train G by the decelerated rotation of the reduction gear train G accompanying the rotation of the step motor M. Pointer shaft 30b
Rotate.

The casing 30c is supported by the wiring board 40 from the back side by the upper wall thereof. The pointer shaft 30b is rotatably supported by the upper wall and the lower wall of the casing 30c, and the pointer shaft 30b is supported by the upper wall of the casing 30c, the wiring board 40, and the through hole portion 11 of the scale 10. It extends rotatably through. The wiring board 40 is arranged on the back surface side of the graduation board 10 in parallel with it.

As shown in FIGS. 3 and 4, the step motor M includes a stator Ms and a magnet rotor Mr. The stator Ms is supported in parallel with the dial 10 in the casing 30c.
s includes a yoke 31 and both field windings 32 and 33. The yoke 31 includes pole-shaped magnetic poles 31a and 31b.
The magnetic pole 31a has a field winding 32 wound around it, and the magnetic pole 31b has a field winding 33 wound around it.

The magnet rotor Mr has a yoke 3
The magnet rotor Mr is coaxially supported by a rotary shaft 35a described later so as to form a magnetic circuit together with the yoke in the inner circumference of the magnet 1. A large number of S poles are alternately magnetized. Here, the magnet rotor Mr, with its N pole or S pole, faces the front end surfaces of the magnetic poles 31a, 31b of the yoke 31 and other magnetic poles with a narrow gap as the magnet rotor Mr rotates. However, the rotation of the magnet rotor Mr is performed by 1 / the number of magnetic poles of the magnet rotor. The rotary shaft 35a is rotatably supported on the upper and lower walls of the casing 30c in parallel with the pointer shaft 30b.

In the step motor M constructed as described above, when the cosine-wave drive voltage and the sine-wave drive voltage for making the phases 90 degrees with each other are applied to the corresponding field windings 32 and 33, these field windings are applied. Currents flowing through 32 and 33 generate cosine wave-shaped and sine wave-shaped magnetic fluxes in the corresponding magnetic poles 31a and 31b, and the magnet rotor Mr forms a magnetic circuit with the yoke 31 and rotates normally. This forward rotation corresponds to the clockwise rotation in FIG.

The reduction gear train G is the output stage gear 3 described above.
4, the input stage gear 35 and both intermediate gears 36 and 37 are provided. The output stage gear 34, the input stage gear 35 and both intermediate gears 36 and 37 reduce the rotation speed of the step motor M to a predetermined low speed. The reduction gear train G is meshed with such a reduction ratio.

The stopper mechanism ST is a strip plate stopper 3
8 and an L-shaped arm 39. The stopper 38 is
At the position corresponding to the zero return position (described later) of the pointer 50,
It is formed so as to project on the surface of the output stage gear 34. In other words, the stopper 38 is formed on the surface of the output stage gear 34 in the radial direction from the pointer shaft 30b so as to correspond to the extending direction of the pointer 50 from the tip end portion of the pointer shaft 30b.

The arm 39 extends in the casing 30c from its lower wall in parallel with the pointer shaft 30b.
At the tip portion 39a thereof extends toward the surface of the output stage 34 in an L shape immediately below the pointer 50 in the longitudinal direction at the zeroing position. Here, the tip 39 of the arm 39
In FIG. 3A, the illustrated clockwise end face 39b corresponds to the zero-reset position of the pointer 50. As a result, when the pointer 50 reaches the zero-reset position due to the reverse rotation of the step motor M (rotation in the counterclockwise direction in FIG. 1), the stopper 38 moves to the position shown in FIG.
Is locked to the clockwise end surface 39b of the arm 39 by the counterclockwise surface 38a shown in the figure. In this embodiment, this locking is called locking of the stopper mechanism ST.

The pointer 50 is supported by the tip end of the pointer shaft 30b at its rotation base portion 51 so as to rotate along the surface of the dial 10. The pointer 50 is adapted to rotate over the entire range of the arc-shaped scale portion 10a of the dial 10, and the pointer 50 is at its zero position, that is, the arc-shaped scale portion 10a of the dial 10. The vehicle is stopped at a position corresponding to the lower limit scale value (vehicle speed of 0 km / h).

Next, an electric circuit configuration for the step motor M will be described with reference to FIG. The microcomputer 60 executes the computer program according to the flowcharts shown in FIGS. 6 to 10, and during this execution, the detection output of the vehicle speed sensor SV and the EEPROM 9 are executed.
Both drive devices 7 based on the stored data of 0 (described later)
The process of driving the step motor M via 0 and 80, the process of determining the arrival of the pointer 50 at the zero return position, and the like are performed. The microcomputer 60 operates by being supplied with power from the battery B via the ignition switch IG of the passenger car. The computer program is stored in the ROM of the microcomputer 60 in advance.

The vehicle speed sensor SV detects the vehicle speed of the passenger car. The drive device 70 includes a drive circuit 70a and both changeover switches 70b and 70c. Drive circuit 7
0a is under the control of the microcomputer 60,
The field winding 32 through both changeover switches 70b and 70c.
To drive. The drive circuit 70a has its both input terminals connected to both output terminals 61, 6 of the microcomputer 60.
Connected to 2.

The changeover switches 70b and 70c are controlled by the microcomputer 60. The changeover switch 70b has both fixed contacts 71 and 72.
And a switching contact 73 that is switched into either of the fixed contacts 71 and 72.
In the changeover switch 70b, the closing state of the switching contact 73 to the fixed contact 71 is referred to as a first closing state,
A closed state of the switching contact 73 to the fixed contact 72 is called a second closed state, and both fixed contacts 71 and 7 of the switching contact 73 are called.
The dissociated state from 2 is called an open state.

The changeover switch 70c has two fixed contacts 7
4 and 75, and a switching contact 76 which is switched into either of the switching contacts 74 and 75. In the changeover switch 70c, the closing state of the switching contact 76 to the fixed contact 74 is called a first closing state, and the closing state of the switching contact 76 to the fixed contact 75 is called a second closing state. The disengaged state from the contact points 74 and 75 is called an open state.

The field winding 32 of the step motor M is connected between the switching contacts 73 and 76. In the present embodiment, the field winding 32 is also referred to as the A-phase winding 32. Along with this, the cosine-wave drive voltage to the A-phase winding 32 is also referred to as the A-phase drive voltage. Also, both fixed contacts 72, 75
Is connected to both output terminals 65 and 66 of the microcomputer 60, and both fixed contacts 71 and 74 are connected to both output terminals of the drive circuit 70a.

The drive unit 80 includes a drive circuit 80a and both changeover switches 80b and 80c. The drive circuit 80a drives the field winding 33 via both changeover switches 80b and 80c under the control of the microcomputer 60. It should be noted that the drive circuit 80a has its both input terminals connected to both output terminals 6 of the microcomputer 60.
3 and 64 are connected.

The changeover switches 80b and 80c are controlled by the microcomputer 60, and the changeover switch 80b has both fixed contacts 81 and 82.
And a switching contact 83 which is switched into either of the fixed contacts 81 and 82.
In the changeover switch 80b, the closed state of the changeover contact 83 to the fixed contact 81 is called the first closed state,
The closed state of the switching contact 83 to the fixed contact 82 is called a second closed state, and both fixed contacts 81 and 8 of the switching contact 83 are called.
The dissociation from 2 is called an open state.

The changeover switch 80c has two fixed contacts 8
4, 85, and a switching contact 86 which is switched into either of the fixed contacts 84, 85. In the changeover switch 80c, the closing state of the switching contact 86 to the fixed contact 84 is referred to as a first closing state, and the closing state of the switching contact 86 to the fixed contact 85 is referred to as a second closing state. Dissociation from the contact points 84 and 85 is called an open state.

The field winding 33 of the step motor M is connected between the switching contacts 83 and 86. In the present embodiment, the field winding 33 is also referred to as the B-phase winding 33. Accordingly, the sinusoidal drive voltage applied to the B-phase winding 33 is also referred to as the B-phase drive voltage. Also, both fixed contacts 82, 85
Is connected to both output terminals 67 and 68 of the microcomputer 60, and both fixed contacts 81 and 84 are connected to both output terminals of the drive circuit 80a.

In the EEPROM 90, a judgment standard for judging the arrival of the pointer 50 at the zero-reset position is written with reference data as will be described later. In this embodiment,
The reference data is data representing a predetermined electrical angle (an electrical angle indicated by a symbol C in FIGS. 11 and 13) corresponding to a predetermined rotation angle of the step motor M. Note that FIG. 11 and FIG.
, The electrical angle indicated by the symbol A is zero degrees, the electrical angle indicated by the symbol B is 90 degrees, and the electrical angle indicated by the symbol C is 18 degrees.
It is 0 degree, and the electrical angle indicated by the symbol D is 270 degrees.

In the present embodiment configured as described above, when the ignition switch IG is turned on, the microcomputer 60 is powered by the battery B to operate, and executes the computer program according to the flowcharts of FIGS. 6 to 10. Start. The passenger vehicle is assumed to be in a traveling state with the ignition switch IG turned on.

Therefore, in step 100 of FIG. 6, each of the changeover switches 70b, 70c, 80b, 80.
Processing for switching both c to the first input state is performed. Thereby, the changeover switches 70b, 70c, 80
Both b and 80c are switched to the first input state by the microcomputer 60. Therefore, both output terminals of the drive circuit 70a are connected to the two selector switches 70b, 7b.
0c is connected to both ends of the A-phase winding 32 of the step motor M, and both output terminals of the drive circuit 80a are connected to both ends of the B-phase winding 33 of the step motor M through both changeover switches 80b and 80c.

After that, in the synchronization processing routine 110, the synchronization processing of the step motor M is performed as follows. That is, from the microcomputer 60 to each drive circuit 7
Zero return voltage of A phase and B phase to 0a, 80a (each voltage of cosine wave and sine wave that reverses the step motor M)
When the output processing is performed, the drive circuit 70a applies the A-phase zero-return voltage to the A-phase winding 32 through the two switches 70b and 70c, and the drive circuit 80a outputs the B-phase zero-return voltage to the B-phase. It is applied to the winding 33.

Accordingly, assuming that the rotation angle of the step motor M reaches the position (zero scale position) indicated by the symbol a in FIG. 11 in electrical angle, the step motor M moves counterclockwise in FIG. It rotates by 40 degrees at an electrical angle. Then, from the microcomputer 60 to each drive circuit 70a,
When the output processing of each of the A-phase and B-phase drive voltages to 80a is performed, the step motor M moves clockwise toward the zero scale position (the position indicated by symbol a in FIG. 11) as shown in FIG. Rotate to. After that, when the output processing of each zero-reset voltage of the A phase and the B phase from the microcomputer 60 to each of the drive circuits 70a and 80a is performed again, the step motor M detects zero in the counterclockwise direction shown in FIG. Rotate toward position C (corresponding to electrical angle C). After that, when the output processing of each of the A-phase and B-phase drive voltages from the microcomputer 60 to each of the drive circuits 70a and 80a is performed, the step motor M causes only 273 degrees in electrical angle from the detection zero position C. That is, it rotates clockwise toward the position indicated by the symbol b in FIG. As a result, the synchronization process of the step motor M ends.

In the present embodiment, the detected zero position is any one of the electrical angles A, B, C, D (that is, each electrical angle at which the zero-zero voltage level of the A phase or the B phase is zero). ), Where the detected zero position corresponds to the electrical angle C. The zero scale position is stored in the ROM of the microcomputer 60 in advance.
It is a position determined by taking into account offset angles every 30 degrees with reference to the above-mentioned detected zero position, and corresponds to the position indicated by the symbol a in FIG. 11 here.

When the synchronization processing is completed in this way,
In the next acceleration processing routine 120, the acceleration processing of the step motor M is performed as follows. That is, when the microcomputer 60 performs output processing of each zero-reset voltage of the A phase and the B phase to each of the drive circuits 70a and 80a,
The step motor M rotates counterclockwise from the rotation angle at the end of the synchronization process (see reference numeral b in FIGS. 11 and 13) under the drive of the drive circuits 70a and 80a (see FIG. 1).
3). This means that the acceleration process for the step motor M is performed.

When the step motor M rotates to the rotation angle B over the respective rotation angles D and A in FIG. 13 by this acceleration processing, the acceleration due to the rotation of the acceleration section of the step motor M ends, so that the process proceeds to step 121. Is determined to be YES.

When the acceleration processing of the step motor M is completed in this way, the processing of the zero position detection processing routine 130 is performed as follows according to the flowcharts shown in FIGS. First, in step 131 of FIG.
Each drive circuit 70a, 8 by the microcomputer 60
Output processing of each zero-return voltage of the A phase and the B phase to 0a is performed. Along with this, the step motor M rotates counterclockwise from the rotation end angle (see symbol B in FIG. 13) of the acceleration section. Along with this, when the step motor M rotates 45 degrees in electrical angle, YES is determined in step 132.

Then, in the next step 132a,
A switching process is performed in which the changeover switch 70c is in the second closing state and the changeover switch 70b is in the open state. Therefore, the A-phase winding 32 is opened at one end by the changeover switch 70b and is connected at the other end to the output terminal 66 of the microcomputer 60 by the changeover switch 70c. In this state, since both the changeover switches 80b and 80c are maintained in the first closing state, the step motor M further rotates counterclockwise.

As a result, when the step motor M rotates 45 degrees in electrical angle, YES is obtained in step 132b.
Then, in step 132c, the induced voltage generated at the present stage from the A-phase winding 32 is input to the microcomputer 60. This induced voltage is
At 2a, one end of the A-phase winding 32 has a changeover switch 70b.
It is equivalent to the voltage caused by being released by. Then, in step 132d, it is determined whether or not the input induced voltage in step 132c is equal to or lower than the predetermined threshold voltage Vth. In this embodiment, the threshold voltage Vth is set to a predetermined low voltage close to zero voltage.

Here, the reason why the predetermined low voltage is adopted as the threshold voltage Vth will be described. The level of the A-phase zero-zero voltage changes like a cosine wave as the phase of the A-phase zero-zero voltage changes, and is a quarter cycle (electrical angle of 90 degrees).
Becomes zero at the phase corresponding to, and changes from positive to negative or from negative to positive before and after that phase. Therefore, since the magnetic flux density corresponding to the A-phase zero-zero voltage caused by this change also changes, the change rate of the magnetic flux density is large. Therefore, the voltage (induced voltage) induced in the field winding 32 due to the magnetic flux density having the large rate of change greatly changes.

On the other hand, the level of the A-phase zero-zero voltage is almost equal to the extreme value before and after the phase corresponding to the peak time. Therefore, since the magnetic flux density corresponding to the A-phase zero-zero voltage at this time hardly changes, the rate of change of the magnetic flux density is very small. Therefore, the voltage (induced voltage) induced in the field winding 32 due to the magnetic flux density having the small change rate is also very small.

When the stopper mechanism ST is locked by the pointer 50 reaching the zero return position, the step motor M
Counterclockwise rotation stops. Therefore, the magnet rotor Mr does not cut the magnetic flux corresponding to the A-phase zero-zero voltage, and the induced voltage of the field winding 32 at this time is zero.

From the above, in order to determine that the stopper mechanism S is locked, if the rate of change of the magnetic flux density is large, it can be determined accurately and in good timing.
Therefore, in this embodiment, the predetermined low voltage close to the zero level of the A-phase zero-zero voltage that produces a magnetic flux density with a large rate of change is adopted as the threshold voltage Vth that is the determination criterion in step 132d.

However, if the input induced voltage in step 132c is less than or equal to the threshold voltage Vth, step 132d.
The determination is YES, and in step 136 (see FIG. 10), it is determined that the zero position has been detected, and the zero position related to this detection is held as an output for a certain period.

On the other hand, if the determination in step 132d is no, in step 133 of FIG. 8, both the changeover switches 70b and 70c are switched to the first closing state. Accordingly, the drive circuit 70a
Switches both changeover switches 70b and 70c to the first closing state.

After the processing in step 133, however, in step 133a, the output continuation processing of the zero-zero voltage of each of the A phase and the B phase is performed. Along with this, the step motor M causes the changeover switches 70b, 70c, 80b, 8
Under the first turn-on state of 0c, both drive circuits 70a, 80a
Is driven by and exceeds the rotation angle corresponding to the electrical angle C to rotate in the counterclockwise direction.

Accordingly, when the step motor M rotates 45 degrees counterclockwise in electrical angle, the determination in step 133b becomes YES. Then, next step 13
In 3c, a switching process is performed in which the changeover switch 80b is set to the second closing state and the changeover switch 80c is opened. Therefore, the B-phase winding 33 is opened at one end by the changeover switch 80c and is connected at the other end to the output terminal 67 of the microcomputer 60 by the changeover switch 80b. In this state, both changeover switches 70b and 70c are maintained in the first closing state, so that the step motor M further rotates counterclockwise.

When the further rotation of the step motor M in the counterclockwise direction reaches 45 degrees, step 133
If YES is determined in step d, step 133e
At, the induced voltage generated at the current stage from the B-phase winding 33 is input to the microcomputer 60. This induced voltage corresponds to the voltage resulting from the one end of the B-phase winding 33 being opened by the changeover switch 80c in step 133c.

Therefore, in step 133f, it is determined whether or not the input induced voltage in step 133e is less than or equal to the threshold voltage Vth. This threshold voltage Vth is the same as the threshold voltage Vth which is the determination reference in step 132d, and is different between the induced voltage generated in the B-phase winding 33 and the induced voltage generated in the A-phase winding 32. The same applies.

Here, if the input induced voltage in step 133e is less than or equal to the threshold voltage Vth, the determination in step 133f is YES, and in step 136, it is determined to be the zero position detection as in the above, and this detection is performed. The zero position related to is held as the output for a certain period.

On the other hand, if the determination in step 133f is no, in step 134 of FIG. 9, a process of switching both the changeover switches 80b and 80c to the first closed state is performed. Accordingly, the drive circuit 80a
Switches both selector switches 80b, 80c to the first closing state.

After the processing in step 134, however, in step 134a, the output continuation processing of each zero-reset voltage of the A phase and the B phase is performed. Along with this, the step motor M causes the changeover switches 70b, 70c, 80b, 8
Under the first turn-on state of 0c, both drive circuits 70a, 80a
Is driven by and exceeds the rotation angle corresponding to the electrical angle D, and further rotates counterclockwise.

As a result, when the counterclockwise rotation of the step motor M reaches 45 degrees, the determination in step 134b becomes YES. Then, the next step 134
In c, a switching process is performed in which the changeover switch 70b is set to the second closing state and the changeover switch 70c is opened. Therefore, the A-phase winding 32 is opened at one end by the changeover switch 70c, and is connected at the other end to the output terminal 65 of the microcomputer 60 by the changeover switch 70b. In this state,
Since both changeover switches 80b and 80c are maintained in the first closing state, the step motor M further rotates in the counterclockwise direction.

As a result, when the counterclockwise rotation of the step motor M reaches 45 degrees, YES is determined in the step 134d, and the induced voltage generated from the A-phase winding 32 at the present stage is determined in the step 134e. It is input to the microcomputer 60. This induced voltage corresponds to the voltage resulting from the opening of one end of the A-phase winding 32 by the changeover switch 70c in step 134c.

Therefore, in step 134f, it is determined whether or not the input induced voltage in step 134e is less than or equal to the threshold voltage Vth. Here, if the input induced voltage in step 134e is not more than the threshold voltage Vth, step 1
The determination in 34f is YES, and in step 136, it is determined that the zero position has been detected, and the zero position detected by this detection is held as the output for a certain period of time, as described above.

On the other hand, if the determination in step 134f is no, in step 135 of FIG. 10, both the changeover switches 70b and 70c are switched to the first closing state. Accordingly, the drive circuit 70a
Switches both changeover switches 70b and 70c to the first closing state.

After the processing in step 135, however, in step 135a, the output continuation processing of each zero-reset voltage of the A phase and the B phase is performed. Along with this, the step motor M causes the changeover switches 70b, 70c, 80b, 8
Under the first turn-on state of 0c, both drive circuits 70a, 80a
Is driven by and exceeds the rotation angle corresponding to the electrical angle A, and further rotates in the counterclockwise direction.

As a result, when the rotation of the step motor M in the counterclockwise direction reaches 45 degrees, the determination in step 135b becomes YES. Then, the next step 135
In c, a switching process is performed in which the changeover switch 80c is set to the second closing state and the changeover switch 80b is opened. Therefore, the B-phase winding 33 is opened at one end by the changeover switch 80b and is connected at the other end to the output terminal 68 of the microcomputer 60 by the changeover switch 80c. In this state,
Since both changeover switches 70b and 70c are maintained in the first closing state, the step motor M further rotates in the counterclockwise direction.

As a result, when the step motor M rotates 45 degrees in electrical angle, YES is obtained in step 135d.
Then, in step 135e, the induced voltage generated at this stage from the B-phase winding 33 is input to the microcomputer 60. This induced voltage is
At 5c, one end of the B-phase winding 33 has a changeover switch 80b.
It is equivalent to the voltage caused by being released by.

Therefore, in step 135f, it is determined whether or not the input induced voltage in step 135e is less than or equal to the threshold voltage Vth. Here, if the input induced voltage in step 135e is less than or equal to the threshold voltage Vth, step 1
The determination in step 35f is YES, and in step 136, similarly to the above, it is determined that the zero position is detected, and this zero position is held as an output for a certain period. On the other hand, step 1
When the determination in 35f is NO, the processes after step 131 in FIG. 7 are performed again.

When the processing of the zero position detection processing routine 130 is completed as described above, the computer program proceeds to step 140 of FIG. This step 140
Then, it is determined as follows whether or not the detected zero position is correct. In the present embodiment, the step motor 1
The electrical angle C is stored in advance in the EEPROM 90 for the determination at 40. When the detected zero position corresponds to the electrical angle C or the electrical angle B or D before and after the electrical angle C,
To be correct.

Then, in step 140, the detected zero position is the electrical angle C stored in the EEPROM 90.
Alternatively, if it does not correspond to the electrical angle B or D before and after that, the determination in step 140 is NO. On the other hand, the detected zero position is the electrical angle C or the electrical angle B or D before and after it.
When it corresponds to, YES is determined.

As described above, the determination in step 140 is N
When it becomes O, it is determined in step 150 whether or not the specified number of retries has been completed. Here, whether or not the specified number of retries has been completed means whether or not the processes of steps 100 to 140 have been tried a specified number of times (for example, several times). At this stage, the processing of steps 100 to 140 has been completed only once, so the determination in step 150 is NO. Along with this, the processes of steps 100 to 140 are repeated as described above. Then, such repetition is performed until the specified number of times is reached under the judgment of NO in step 140.

Therefore, the determination in step 150 is YE.
If the determination in step 140 is YES before S is reached, the process of step 141 is performed as described above. On the other hand, if the determination in step 150 is YES before the determination in step 140 is YES, step 1
At 51, the zero position detected by the zero position detection processing routine 130 is determined to be abnormal.

When the processing of step 141 or step 151 is completed as described above, it is determined again in step 160 whether the detected zero position is correct. When YES is determined in this step 160, processing for rotating the pointer 50 by the rotating inner unit 30 is performed in the normal processing routine 170 according to the detection output of the vehicle speed sensor SV. As a result, the vehicle speed of the passenger car is indicated by the pointer 50.

As described above, in the present embodiment, each step 13 in the zero position detection processing routine 130 is executed.
When it is determined that the induced voltage is less than or equal to the threshold voltage Vth in any of 2d, 133f, 134f, and 135f, it is determined that the zero position is detected, and the detected zero position corresponds to the electrical angle C or the electrical angle B or D before or after the electrical angle C. At this time, it is determined that the determination of the detected zero position, in other words, the detection of the zero position is correct, and each time it is determined that the detection is not correct, the processes of steps 100 to 140 are repeated a prescribed number of times. This improves the accuracy with which the pointer 50 reaches the zero-reset position without being affected by noise or the like.

In carrying out the present invention, the drive voltage or the zero-return voltage applied to each field winding of the step motor M is not limited to the cosine wave voltage, but the sine wave voltage, the trapezoidal wave voltage, the triangular wave voltage, etc. Any AC signal such as AC voltage or AC current may be used.

In carrying out the present invention, the indicating instrument is not limited to indicating the vehicle speed, but may be an analog value such as the number of revolutions of the engine of the passenger car or the remaining amount of fuel.

Further, in carrying out the present invention, the present invention may be applied not only to an indicating instrument having a step motor M as a drive source but also to a cross coil type indicating instrument.

Further, in carrying out the present invention, the present invention is not limited to passenger car indicating instruments, but may be applied to various indicating instruments for various vehicles such as buses, trucks and motorcycles, and various indicating instruments. .

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of an indicating instrument for a passenger car according to the present invention.

FIG. 2 is a partial cross-sectional side view of the indicating instrument of FIG.

FIG. 3 is a perspective view of a pointer, a step motor and a stopper mechanism built in the rotary internal unit of FIG.

FIG. 4 is a plan view of the step motor of FIG.

FIG. 5 is an electric circuit configuration diagram of an indicating instrument.

6 is a flowchart showing the operation of the microcomputer of FIG.

7 is a part of a flowchart showing a zero position detection processing routine of FIG.

8 is a part of a flowchart showing a zero position detection processing routine of FIG.

9 is a part of a flowchart showing a zero position detection processing routine of FIG.

10 is a part of a flowchart showing a zero position detection processing routine of FIG.

FIG. 11 is a diagram showing a process of step motor synchronization processing.

FIG. 12 is a diagram for determining the zero scale position of the step motor.

FIG. 13 is a diagram showing a process of acceleration processing of a step motor.

[Explanation of symbols]

10 ... Scale plate, 10a ... Scale part, 32, 33 ... Field winding, 50 ... Pointer, 60 ... Microcomputer, 70,
80 ... Drive device, 90 ... EEPROM, G ... Reduction gear train, M ... Step motor, Mr ... Magnet rotor, M
s ... Stator, ST ... Stopper mechanism, SV ... Vehicle speed sensor.

Claims (2)

[Claims] 1. A scale portion (10) in which an analog value is scaled in a substantially arc shape from a lower limit scale value to an upper limit scale value.
a) having a scale), a pointer (50) supported so as to rotate along the surface of the scale, and a field winding (a) for generating an AC magnetic flux by inputting an AC drive signal. 32, 33) and a step motor (M) including a stator (Ms) and a magnet rotor (Mr) that is rotatably supported in the stator and that rotates according to the AC magnetic flux. Deceleration gear means (G) for decelerating rotation along with the rotation and rotating the pointer accordingly, and of the deceleration gear means when the pointer reaches a zero return position corresponding to the lower limit scale value of the analog value. Stopper means (ST) for stopping decelerated rotation, and drive signal input means (70, for inputting the drive signal to the field winding in accordance with the input (SV) representing the analog value.
80, 170), and zero return signal input means (70, 80, 70) for inputting an alternating zero return signal to the field winding when returning the pointer to the zero return position.
100, 131, 133, 133a, 134, 134
a, 135, 135a), a predetermined electric power when the zero return signal advances to a phase angle corresponding to the zero level after the zero return signal is input to the field winding. A storage unit (90) for storing an angle in advance; and the field winding during the rotation of the step motor based on the input of the zero return signal to the field winding by the zero return signal input unit. It is determined that the zero position is detected when the voltage induced by the field winding is cut off from a signal and becomes equal to or lower than a predetermined low voltage indicating the stop of the deceleration rotation of the reduction gear means by the stopper means. First determining means (132a to 132d, 133c to 133f, 13
4c to 134f, 135c to 135f) and the determination of the zero position by the first determining means, the phase angle of the zero return signal is the predetermined electrical angle and the zero return before and after the predetermined electrical angle. Second judging means (240) for judging whether or not the electric angle corresponding to the zero level of the signal has been reached, and the second judging means for determining the predetermined electric angle and the zeroing point before and after the predetermined electric angle. Third determination means (140) for determining that the determination of the zero position by the first determination means is correct when it is determined that the electrical angle has advanced to any one of the electrical angles corresponding to the zero level of the signal; When the determination means determines that the determination of the detection of the zero position is incorrect, the zero return signal input means inputs the zero return signal to the field winding and the first and second
And a fourth determination means (150) for determining whether or not the determination by the determination means has been repeated a specified number of times, and when the fourth determination means determines that the specified number of times has not been repeated, the zero-zero signal input means is used. A vehicle indicating instrument characterized in that the input of the zero-return signal to the field winding and the determination by the first and second determination means are repeated again. 2. The third determination means is configured such that while the zero return signal input means inputs the zero return signal into the field winding and the first and second determination means repeats the specified number of times. When it is determined that the second determination means has advanced to either the predetermined electrical angle or the electrical angle corresponding to the zero level of the zero-reset signal before and after this electrical angle, it is determined that the zero position is detected. Is determined to be correct, and the fourth determination means inputs the zero-zero signal to the field winding by the zero-zero signal input means and the first and second
After the judgment by the judgment means is repeated the specified number of times,
The vehicle indicating instrument according to claim 1, wherein the detection of the zero position is determined to be abnormal.