JP3736419B2 - Indicators for vehicles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicular indicating instrument that employs a step motor as a driving source for a pointer.
[0002]
[Prior art]
Conventionally, in this type of vehicle indicating instrument, there is a type in which a step motor and a reduction gear train driven by the step motor are arranged on the back side of the dial. In the reduction gear train, when the input stage gear is driven by the step motor, the output stage gear rotates at a reduced speed and rotates the pointer along the surface of the dial plate via the pointer shaft. As a result, the indicating instrument issues an analog input instruction using the pointer.
[0003]
Here, when the pointer returns to the zero position (returning zero position) on the scale plate, the indicating instrument stops the rotation of the output gear by its stopper mechanism and stops the pointer at the returning zero position. Thus, the reference position of the pointer is set.
[0004]
[Problems to be solved by the invention]
By the way, in the above indicator, in order to detect that the pointer has returned to the zero return position, an induced voltage generated in the field winding of the step motor is used in the process of driving the step motor with an alternating zero return voltage. When the induced voltage becomes equal to or lower than the predetermined threshold voltage, it is determined that the pointer has reached the return zero position.
[0005]
However, if the pointer has not actually reached the zero return position, for example, if noise occurs in the field winding, it is determined that the noise is below the threshold voltage due to this noise, and the pointer reaches the zero return position. This causes a problem of misjudging it as having been done.
[0006]
In response to this, when a predetermined rotation angle corresponding to the zero return position of the step motor is set in advance as an electrical angle, and when the actual rotation angle of the step motor reaches the predetermined rotation angle as an electrical angle, It is also possible to determine that the pointer has reached the return zero position.
[0007]
However, even if the predetermined rotation angle is also used in determining that the pointer has reached the return zero position, as described above, if the erroneous determination due to noise is assumed as described above, after all, However, the erroneous determination that the pointer has reached the zero return position cannot be resolved.
[0008]
Therefore, in order to deal with the above-described problems, the present invention provides a vehicle indicator that uses a step motor as a drive source for a pointer. By using the induced voltage generated in the field winding of the stepping motor during the driving process and the rotation of the stepping motor to the predetermined rotation angle, and making an erroneous determination, repeat the determination based on the induced voltage. An object of the present invention is to improve the accuracy of determining whether or not the pointer reaches the return zero position.
[0009]
[Means for Solving the Problems]
In solving the above-described problem, the vehicle instrument according to the invention of claim 1 is:
A scale plate (10) having a scale portion (10a) graduated in a substantially arc shape from an analog value to a lower limit scale value to an upper limit scale value;
A pointer (50) supported to rotate along the surface of the dial,
A stator (Ms) having field windings (32, 33) that receive an AC drive signal and generate an AC magnetic flux, and a magnet that is rotatably supported in the stator and rotates according to the AC magnetic flux. A step motor (M) comprising a rotor (Mr);
Reduction gear means (G) that rotates at a reduced speed with the rotation of the magnet rotor and rotates the pointer in accordance with the rotation;
Stopper means (ST) for stopping the reduction rotation of the reduction gear means when the pointer reaches the return zero position corresponding to the lower limit scale value of the analog value;
Drive signal input means (70, 80, 170) for inputting a drive signal to the field winding according to an input (SV) representing an analog value;
And zero return signal input means (70, 80, 100, 131, 133, 133a, 134, 134a, 135, 135a) for inputting an alternating zero return signal to the field winding when returning the pointer to the zero return position. .
[0010]
Storage means (90) for preliminarily storing a predetermined electrical angle when the nulling signal advances to a phase angle corresponding to the zero level after the nulling signal is input to the field winding in the indicating instrument;
When the stepping motor rotates based on the input of the nulling signal to the field winding by the nulling signal input means, the field winding is shielded from the nulling signal, and the induced voltage of the field winding generated by this interruption is First determination means (132a to 132d, 133c to 133f, 134c to 134f, 135c to 135f) for determining that the zero position is detected when the voltage is equal to or lower than a predetermined low voltage indicating stoppage of the reduction gear means by the stopper means. When,
Along with the determination of the zero position detection by the first determination means, the phase angle of the null signal is either the predetermined electrical angle or the electrical angle corresponding to the zero level of the null signal before and after the electrical angle. Second determination means (240) for determining whether or not the vehicle has advanced;
When it is determined that the second determination means has advanced to one of the predetermined electrical angle and the electrical angle corresponding to the zero level of the null signal before and after the electrical angle, the first determination means detects the zero position. Third determination means (140) for determining that the determination of is correct,
When the third determination means determines that the detection of the zero position is not correct, the zero return signal input means inputs the null signal to the field winding and the first and second determination means determine. And a fourth determination means (150) for determining whether or not the specified number of times has been repeated.
When it is determined that the fourth determination means has not been repeated a specified number of times, the input of the null signal to the field winding by the null return signal input means and the determination by the first and second determination means are repeated again. And
[0011]
As described above, when determining whether the pointer reaches the zero return position, the step motor is driven to the zero return position in the process of driving the field winding of the step motor and the electric angle of the step motor. When erroneous determination is made by using rotation to the rotation angle, the determination by the induced voltage can be repeated to improve the accuracy of determining whether or not the pointer reaches the return zero position.
[0012]
According to the invention described in claim 2, in the invention described in claim 1,
The third determination means is configured such that the second determination means repeats the predetermined electric power while the input of the null signal to the field winding by the null return signal input means and the determination by the first and second determination means are repeated a predetermined number of times. When it is determined that the angle has advanced to one of the electrical angles corresponding to the zero level of the null signal before and after the electrical angle, it is determined that the detection of the zero position is correct,
The fourth determination means determines that the detection of the zero position is abnormal after the zero return signal input to the field winding by the return zero signal input means and the determination by the first and second determination means are repeated a specified number of times. It is characterized by doing. Thereby, the effect of the invention of claim 1 can be further improved.
[0013]
In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a passenger car indicating instrument according to the present invention, and this indicating instrument is arranged as a vehicle speed meter on an instrument panel provided in a passenger compartment of the passenger car.
[0015]
As shown in FIGS. 1 and 2, the indicating instrument includes a scale plate 10, and the scale plate 10 has a substantially arc-shaped scale portion 10 a. Here, the scale part 10a has a plurality of scales and is formed so that the vehicle speed ranges from a lower limit scale value (vehicle speed zero km / h) to an upper limit scale value (vehicle speed 180 km / h). The scale plate 10 is provided on the opening 21a formed in the bottom wall 21 of the annular facing plate 20 from the back side.
[0016]
Further, as shown in FIG. 1 or FIG. 2, the indicating instrument includes 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 machine main body 30a is assembled to the wiring board 40 from the back side at a position corresponding to the scale board 10. The internal machine 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 coaxially supported by an output stage gear 34 (described later) of the reduction gear train G by the reduction rotation of the reduction gear train G accompanying the rotation of the step motor M. The pointer shaft 30b is rotated.
[0017]
The casing 30c is supported by the wiring board 40 from the back side thereof on the upper wall thereof. The pointer shaft 30b is rotatably supported by the upper wall and the lower wall of the casing 30c. The pointer shaft 30b is formed through the upper wall of the casing 30c, the wiring board 40, and the through hole portion 11 of the dial 10. It extends so that it can rotate. Further, the wiring board 40 is disposed in parallel to the back side of the scale board 10.
[0018]
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 scale plate 10 in the casing 30c. The stator Ms includes a yoke 31 and both field windings 32 and 33. The yoke 31 includes pole-shaped magnetic poles 31a and 31b and several other magnetic poles. A field winding 32 is wound around the magnetic pole 31a, and a field winding 33 is wound around the magnetic pole 31b. ing.
[0019]
Further, the magnet rotor Mr is coaxially supported on a rotating shaft 35a, which will be described later, so as to be located in the yoke 31 and form a magnetic circuit together with the yoke, and on the outer circumferential surface of the magnet rotor Mr, Along the circumferential direction, a large number of N poles and S poles are alternately magnetized. Here, as the magnet rotor Mr rotates, the magnetic poles 31a and 31b of the yoke 31 and the tip surfaces of the other magnetic poles of the yoke 31 face each other through a narrow gap with the N or S pole. However, the rotation of the magnet rotor Mr is made one by one for the number of magnetic poles of the magnet rotor. The rotating shaft 35a is supported on both the upper and lower walls of the casing 30c so as to be parallel to the pointer shaft 30b and to be rotatable.
[0020]
In the step motor M configured as described above, when a cosine wave driving voltage and a sine wave driving voltage having a phase of 90 degrees are applied to the corresponding field windings 32 and 33, the field windings 32 and 33 are respectively applied. The cosine wave and sine wave magnetic fluxes are generated in the corresponding magnetic poles 31 a and 31 b by the current flowing in the magnetic field, and the magnet rotor Mr forms a magnetic circuit between the yoke 31 and rotates normally. This normal rotation corresponds to the clockwise rotation shown in FIG.
[0021]
The reduction gear train G includes the above-described output stage gear 34, input stage gear 35, and both intermediate gears 36 and 37. These output stage gear 34, input stage gear 35, and both intermediate gears 36 and 37 are stepped. The reduction gear train G is meshed so as to give a reduction gear ratio that reduces the rotational speed of the motor M to a predetermined low speed.
[0022]
The stopper mechanism ST includes a strip plate stopper 38 and an L-shaped arm 39. The stopper 38 is formed to protrude from the surface of the output gear 34 at a position corresponding to a return zero position (described later) of the pointer 50. In other words, the stopper 38 is formed so as to project from the surface of the output 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 portion of the pointer shaft 30b.
[0023]
The arm 39 extends into the casing 30c from the lower wall thereof in parallel with the pointer shaft 30b. The arm 39 is located at the front end portion 39a just below the longitudinal direction of the pointer 50 when it is in the zero return position. It extends toward the surface of the output stage 34 in an L shape. Here, the clockwise end face 39b shown in FIG. 3 of the tip 39a of the arm 39 corresponds to the return zero position of the pointer 50. Thus, when the pointer 50 reaches the zero return position by the reverse rotation of the step motor M (rotation in the counterclockwise direction shown in FIG. 1), the stopper 38 is moved on the counterclockwise surface 38a shown in FIG. The arm 39 is engaged with the clockwise end surface 39b. In this embodiment, this locking is called locking of the stopper mechanism ST.
[0024]
The pointer 50 is supported by the tip end portion of the pointer shaft 30 b at the rotation base 51 and rotates along the surface of the dial 10. The pointer 50 is configured to rotate over the entire range of the arc-shaped scale portion 10 a of the scale 10, and the pointer 50 is located at its return position, that is, the arc-shaped scale portion 10 a of the scale plate 10. The vehicle stops at a position corresponding to the lower limit scale value (vehicle speed zero km / h).
[0025]
Next, an electric circuit configuration for the step motor M will be described with reference to FIG. The microcomputer 60 executes a computer program according to the flowcharts shown in FIGS. 6 to 10, and during this execution, both the drive devices 70, 80 are based on the detection output of the vehicle speed sensor SV and the data stored in the EEPROM 90 (described later). A process for driving the step motor M through the control, a process for determining whether the pointer 50 has reached the return zero 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 advance in the ROM of the microcomputer 60.
[0026]
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. The drive circuit 70a drives the field winding 32 via both changeover switches 70b and 70c under the control of the microcomputer 60. The drive circuit 70a is connected to both output terminals 61 and 62 of the microcomputer 60 at both input terminals.
[0027]
Both change-over switches 70b and 70c are controlled by the microcomputer 60, and the change-over switch 70b is provided with both fixed contacts 71 and 72 and a switching contact 73 that is switched to one of these fixed contacts 71 and 72. It is comprised by. In this change-over switch 70b, the input state of the switching contact 73 to the fixed contact 71 is referred to as a first input state, and the input state of the switching contact 73 to the fixed contact 72 is referred to as a second input state. The dissociated state from the contacts 71 and 72 is called an open state.
[0028]
The change-over switch 70c is composed of both fixed contacts 74, 75 and a change-over contact 76 that is switched to one of the change-over contacts 74, 75. In this change-over switch 70c, the input state of the switching contact 76 to the fixed contact 74 is referred to as a first input state, and the input state of the switching contact 76 to the fixed contact 75 is referred to as a second input state. The dissociated state from the contacts 74 and 75 is referred to as an open state.
[0029]
Here, 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 an A-phase winding 32. Along with this, the cosine wave drive voltage to the A phase winding 32 is also referred to as an A phase drive voltage. Both fixed contacts 72 and 75 are 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.
[0030]
The driving device 80 includes a driving 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. The drive circuit 80a is connected to both output terminals 63 and 64 of the microcomputer 60 at both input terminals.
[0031]
Both change-over switches 80b and 80c are switch-controlled by the microcomputer 60, and the change-over switch 80b is provided with both fixed contacts 81 and 82 and a switch contact 83 that is switched on to either one of these fixed contacts 81 or 82. It is comprised by. In this changeover switch 80b, the input state of the switching contact 83 to the fixed contact 81 is referred to as a first input state, and the input state of the switching contact 83 to the fixed contact 82 is referred to as a second input state. Dissociation from the contacts 81 and 82 is referred to as an open state.
[0032]
The change-over switch 80c includes both fixed contacts 84 and 85 and a change-over contact 86 that is switched to one of the both fixed contacts 84 and 85. In this change-over switch 80c, the input state of the switching contact 86 to the fixed contact 84 is referred to as a first input state, and the input state of the switching contact 86 to the fixed contact 85 is referred to as a second input state. Dissociation from the contacts 84 and 85 is referred to as an open state.
[0033]
Here, 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 a B-phase winding 33. Accordingly, the sinusoidal drive voltage to the B-phase winding 33 is also referred to as a B-phase drive voltage. Both fixed contacts 82 and 85 are 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.
[0034]
In the EEPROM 90, as described later, a criterion for determining whether the pointer 50 has reached the return zero position is written with reference data. In the present 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. 11 and 13, the electrical angle indicated by reference sign A is zero degrees, the electrical angle indicated by reference sign B is 90 degrees, the electrical angle indicated by reference sign C is 180 degrees, and the electrical angle indicated by reference sign D Is 270 degrees.
[0035]
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 and starts to execute the computer program according to the flowcharts of FIGS. It is assumed that the passenger car is in a running state with the ignition switch IG turned on.
[0036]
Accordingly, in step 100 of FIG. 6, a process for switching each of the changeover switches 70b, 70c, 80b, and 80c to the first input state is performed. As a result, the changeover switches 70b, 70c, 80b, and 80c are all switched to the first input state by the microcomputer 60. Therefore, both output terminals of the drive circuit 70a are connected to both ends of the A-phase winding 32 of the step motor M through both changeover switches 70b and 70c, and both output terminals of the drive circuit 80a are connected through both changeover switches 80b and 80c. It is connected to both ends of the B phase winding 33 of the step motor M.
[0037]
Thereafter, in the synchronization processing routine 110, the synchronization processing of the step motor M is performed as follows. That is, when the output processing of the A-phase and B-phase zero return voltages (cosine wave and sine wave voltages for reversing the stepping motor M) from the microcomputer 60 to the drive circuits 70a and 80a is performed. 70 a applies the A-phase nulling voltage to the A-phase winding 32 via both changeover switches 70 b and 70 c, and the drive circuit 80 a applies the B-phase nulling voltage to the B-phase winding 33.
[0038]
Accordingly, if the rotation angle of the step motor M is an electrical angle and is at the position indicated by the symbol a in FIG. 11 (zero scale position), the step motor M is turned to the electrical angle in the counterclockwise direction shown in FIG. Rotate 40 degrees. Next, when 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 stepping motor M moves to the zero scale position (see FIG. 11). Rotate clockwise toward the position indicated by symbol a). After that, when output processing of each zero-phase voltage of the A phase and the B phase from the microcomputer 60 to the respective 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). Thereafter, when the output processing of the A-phase and B-phase drive voltages from the microcomputer 60 to the drive circuits 70a and 80a is performed, the stepping motor M is only 273 degrees in electrical angle from the detection zero position C. That is, it rotates in the clockwise direction toward the position indicated by symbol b in FIG. Thereby, the synchronization process of the step motor M is completed.
[0039]
In the present embodiment, the detection zero position refers to any of the electrical angles A, B, C, and D (that is, any of the electrical angles at which the level of the zero voltage of the A phase or the B phase becomes zero). Here, the detection zero position corresponds to the electrical angle C. The zero scale position is stored in advance in the ROM of the microcomputer 60. The zero scale position is a position determined by a value that takes into account an offset angle of every 30 degrees with respect to the detected zero position. Here, it corresponds to the position indicated by symbol a in FIG.
[0040]
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 the output processing of the A-phase and B-phase feedback voltages to the drive circuits 70a and 80a, the step motor M is synchronized with the drive by the drive circuits 70a and 80a. It rotates counterclockwise from the rotation angle at the end of the conversion process (see symbol b in FIGS. 11 and 13) (see FIG. 13). This means that acceleration processing for the step motor M is performed.
[0041]
When the step motor M is rotated to the rotation angle B beyond the rotation angles D and A in FIG. 13 by this acceleration process, the acceleration by the rotation of the acceleration section of the step motor M is completed. Determined.
[0042]
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. 7, the microcomputer 60 performs an output process of each zero-phase voltage of the A phase and the B phase to the respective drive circuits 70a and 80a. Along with this, the step motor M rotates counterclockwise from the rotation end angle of the acceleration section (see symbol B in FIG. 13). Accordingly, if step motor M rotates 45 degrees in electrical angle, it is determined as YES in step 132.
[0043]
Then, in the next step 132a, a switching process is performed in which the changeover switch 70c is set to the second on state and the changeover switch 70b is opened. For this reason, 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 input state, the step motor M further rotates counterclockwise.
[0044]
Thus, when the step motor M rotates 45 degrees in electrical angle, a determination of YES is made in step 132b, and an induced voltage generated at this stage from the A-phase winding 32 is input to the microcomputer 60 in step 132c. . This induced voltage corresponds to a voltage resulting from the opening of one end of the A-phase winding 32 by the changeover switch 70b in step 132a. Accordingly, in step 132d, it is determined whether or not the input induced voltage in step 132c is equal to or lower than a predetermined threshold voltage Vth. In the present embodiment, the threshold voltage Vth is set to a predetermined low voltage close to zero voltage.
[0045]
Here, the reason why the predetermined low voltage is adopted as the threshold voltage Vth will be described. The level of the A-phase return zero voltage changes in a cosine wave shape with the change in the phase of the A-phase return zero voltage, and becomes zero at a phase corresponding to a quarter period (90 degrees in electrical angle). It changes from positive to negative or from negative to positive before and after. Therefore, since the magnetic flux density corresponding to the A-phase return zero voltage resulting from this change also changes, the rate of change of the magnetic flux density is large. Therefore, the voltage (induced voltage) induced in the field winding 32 is greatly changed due to the magnetic flux density having the large change rate.
[0046]
On the other hand, the level of the A-phase return zero voltage is almost equal to the extreme value before and after the phase corresponding to the peak. Accordingly, since the magnetic flux density corresponding to the A-phase return 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 with this small change rate is very small.
[0047]
When the stopper mechanism ST is locked by the pointer 50 reaching the return zero position, the rotation of the step motor M in the counterclockwise direction is stopped. Accordingly, since the magnet rotor Mr does not cut the magnetic flux corresponding to the A-phase return zero voltage, the induced voltage of the field winding 32 at this time is zero.
[0048]
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, the determination can be made with good accuracy and timing. Therefore, in the present embodiment, the predetermined low voltage close to the zero level of the A-phase return zero voltage that generates a magnetic flux density with a large change rate is adopted as the threshold voltage Vth that is the determination criterion in step 132d.
[0049]
If the input induced voltage in step 132c is equal to or lower than the threshold voltage Vth, the determination in step 132d is YES, and in step 136 (see FIG. 10), it is determined that the zero position is detected. The zero position is held as an output for a certain period.
[0050]
On the other hand, if the determination in step 132d is NO, in step 133 of FIG. 8, a process of switching both the changeover switches 70b and 70c to the first on state is performed. Accordingly, the drive circuit 70a switches both the changeover switches 70b and 70c to the first on state.
[0051]
Thus, after the processing in step 133, in step 133a, output continuation processing of each zero-phase voltage of the A phase and the B phase is performed. Accordingly, the step motor M is driven by the drive circuits 70a and 80a under the first input state of the changeover switches 70b, 70c, 80b and 80c, and exceeds the rotation angle corresponding to the electrical angle C. Rotates counterclockwise.
[0052]
As a result, when the step motor M rotates 45 degrees counterclockwise with an electrical angle, the determination in step 133b becomes YES. Then, in the next step 133c, a switching process for setting the changeover switch 80b to the second on state and the changeover switch 80c to the open state is performed. For this reason, 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, since both the changeover switches 70b and 70c are maintained in the first input state, the step motor M further rotates counterclockwise.
[0053]
When the further counterclockwise rotation of the step motor M reaches 45 degrees, a determination of YES is made in step 133d, and in step 133e, the induced voltage generated at this stage from the B-phase winding 33 is a microcomputer. 60. This induced voltage corresponds to a voltage resulting from opening of one end of the B-phase winding 33 by the changeover switch 80c in step 133c.
[0054]
Accordingly, in step 133f, it is determined whether or not the input induced voltage in step 133e is equal to or lower than the threshold voltage Vth. This threshold voltage Vth is the same as the threshold voltage Vth that is the criterion in step 132d. The threshold voltage Vth is the same as the induced voltage generated in the B-phase winding 33 and the induced voltage generated in the A-phase winding 32. The same applies.
[0055]
Here, if the input induced voltage in step 133e is equal to or lower than the threshold voltage Vth, the determination in step 133f is YES, and in step 136, it is determined that the zero position is detected as described above. The position is held as an output for a certain period.
[0056]
On the other hand, when 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 on state is performed. Accordingly, the drive circuit 80a switches both change-over switches 80b and 80c to the first on state.
[0057]
Thus, after the processing in step 134, the output continuation processing of each zero-phase voltage of the A phase and the B phase is performed in step 134a. Accordingly, the step motor M is driven by the drive circuits 70a and 80a under the first input state of the changeover switches 70b, 70c, 80b and 80c, and exceeds the rotation angle corresponding to the electrical angle D. Furthermore, it rotates counterclockwise.
[0058]
Thereby, when the rotation of the stepping motor M in the counterclockwise direction reaches 45 degrees, the determination in step 134b becomes YES. Then, in the next step 134c, a switching process is performed in which the changeover switch 70b is set to the second on 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 the changeover switches 80b and 80c are maintained in the first input state, the step motor M further rotates counterclockwise.
[0059]
Thus, when the rotation of the stepping motor M in the counterclockwise direction reaches 45 degrees, a determination of YES is made in step 134d, and in step 134e, the induced voltage generated at this stage from the A-phase winding 32 is the microcomputer 60. Is input. This induced voltage corresponds to a voltage resulting from opening of one end of the A-phase winding 32 by the changeover switch 70c in step 134c.
[0060]
Therefore, in step 134f, it is determined whether or not the input induced voltage in step 134e is equal to or lower than the threshold voltage Vth. Here, if the input induced voltage in step 134e is equal to or lower than the threshold voltage Vth, the determination in step 134f is YES, and in step 136, it is determined that the zero position is detected in the same manner as described above. Is held as an output for a certain period.
[0061]
On the other hand, when the determination in step 134f is NO, in step 135 of FIG. 10, a process of switching both the changeover switches 70b and 70c to the first on state is performed. Accordingly, the drive circuit 70a switches both the changeover switches 70b and 70c to the first on state.
[0062]
Thus, after the processing in step 135, in step 135a, output continuation processing of each zero-phase voltage of the A phase and the B phase is performed. Accordingly, the step motor M is driven by the drive circuits 70a and 80a under the first input state of the changeover switches 70b, 70c, 80b and 80c, and exceeds the rotation angle corresponding to the electrical angle A. Furthermore, it rotates counterclockwise.
[0063]
Accordingly, when the rotation of the step motor M in the counterclockwise direction reaches 45 degrees, the determination in step 135b is YES. Then, in the next step 135c, a switching process is performed in which the changeover switch 80c is set to the second on state and the changeover switch 80b is opened. For this reason, 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 the changeover switches 70b and 70c are maintained in the first input state, the step motor M further rotates counterclockwise.
[0064]
Thus, when the step motor M rotates 45 degrees in electrical angle, a determination of YES is made in step 135d, and the induced voltage generated at the present stage from the B-phase winding 33 is input to the microcomputer 60 in step 135e. . This induced voltage corresponds to a voltage resulting from opening of one end of the B-phase winding 33 by the changeover switch 80b in step 135c.
[0065]
Accordingly, in step 135f, it is determined whether or not the input induced voltage in step 135e is equal to or lower than the threshold voltage Vth. Here, if the input induced voltage in step 135e is equal to or lower than the threshold voltage Vth, the determination in step 135f is YES, and in step 136, as described above, it is determined that the zero position is detected, and this zero position is constant. Held as period output. On the other hand, if the determination in step 135f is no, the processing after step 131 in FIG. 7 is performed again.
[0066]
When the processing of the zero position detection processing routine 130 is completed as described above, the computer program proceeds to step 140 in FIG. In step 140, whether the detected zero position is correct is determined as follows. In the present embodiment, the electrical angle C is stored in advance in the EEPROM 90 for determination by the step motor 140. The detected zero position is correct when it corresponds to the electrical angle C or the electrical angle B or D before and after the electrical angle C.
[0067]
Therefore, if the detected zero position does not correspond to the electrical angle C already stored in the EEPROM 90 or the electrical angle B or D before and after that in step 140, the determination in step 140 is NO. On the other hand, 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, it is determined as YES.
[0068]
As described above, when the determination in step 140 is NO, 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 times has been retried means whether or not the processing of Step 100 to Step 140 has been tried a specified number of times (for example, several times). At this stage, since the processing from step 100 to step 140 has been completed only once, the determination at step 150 is NO. Accordingly, the processing from step 100 to step 140 is repeated in the same manner as described above. Such a repetition is repeated until the specified number of times is reached under the determination of NO in step 140.
[0069]
Thus, if the determination in step 140 is YES before the determination in step 150 is YES, the processing in step 141 is performed in the same manner as described above. On the other hand, if the determination in step 150 becomes YES before the determination in step 140 becomes YES, in step 151, the zero position detected in the zero position detection processing routine 130 is determined to be abnormal.
[0070]
When the processing of step 141 or step 151 ends as described above, it is determined again in step 160 whether the detected zero position is correct. If YES is determined in this step 160, the normal processing routine 170 performs a process of turning the pointer 50 by the turning inner unit 30 in accordance with the detection output of the vehicle speed sensor SV. Thereby, the vehicle speed of the passenger car is instructed by the pointer 50.
[0071]
As described above, in this embodiment, when the zero position detection processing routine 130 determines that the induced voltage is equal to or lower than the threshold voltage Vth in any of the steps 132d, 133f, 134f, and 135f, the zero position detection is determined. When the detected zero position corresponds to the electrical angle C or the electrical angle B or D before and after that, it is determined that the detection zero position, in other words, the detection of the zero position is correct, and is not correct. Each time, the processing of steps 100 to 140 is repeated a prescribed number of times. As a result, the accuracy with which the pointer 50 reaches the return zero position is improved without being affected by noise or the like.
[0072]
In the implementation of the present invention, the drive voltage or the null voltage applied to each field winding of the step motor M is not limited to the cosine wave voltage, but is an AC voltage such as a sine wave voltage, a trapezoidal wave voltage, or a triangular wave voltage. Or an AC signal such as an AC current.
[0073]
In implementing the present invention, the indicating instrument is not limited to indicating the vehicle speed, and may indicate an analog value such as the engine speed of the passenger car and the remaining amount of fuel.
[0074]
In implementing 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.
[0075]
Further, in carrying out the present invention, the present invention may be applied to various indicating instruments for various vehicles such as buses, trucks, and motorcycles, and other various indicating instruments, without being limited to the indicating instrument for passenger cars.
[Brief description of the drawings]
FIG. 1 is a front view showing an embodiment of a passenger car indicating instrument 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 step motor and a stopper mechanism built in the pointer of FIG.
4 is a plan view of the step motor of FIG. 3;
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. 6;
8 is a part of a flowchart showing a zero position detection processing routine of FIG. 6;
9 is a part of a flowchart showing a zero position detection processing routine of FIG. 6;
10 is a part of a flowchart showing a zero position detection processing routine of FIG. 6;
FIG. 11 is a diagram illustrating a step motor synchronization process;
FIG. 12 is a diagram for determining a zero scale position of a step motor.
FIG. 13 is a diagram illustrating a process of acceleration processing of a step motor.
[Explanation of symbols]
10 ... Scale plate, 10a ... Scale unit, 32, 33 ... Field winding, 50 ... Pointer,
60 ... Microcomputer, 70, 80 ... Drive device,
90 ... EEPROM, G ... reduction gear train, M ... step motor,
Mr: Magnet rotor, Ms: Stator, ST: Stopper mechanism,
SV: Vehicle speed sensor.

Claims (2)

A scale plate (10) having a scale portion (10a) graduated in a substantially arc shape from an analog value to a lower limit scale value to an upper limit scale value;
A pointer (50) supported to rotate along the surface of the dial,
A stator (Ms) having field windings (32, 33) that receive an AC drive signal and generate an AC magnetic flux, and a magnet that is rotatably supported in the stator and rotates according to the AC magnetic flux. A step motor (M) comprising a rotor (Mr);
Reduction gear means (G) that rotates at a reduced speed with the rotation of the magnet rotor and rotates the pointer in accordance with the rotation;
Stopper means (ST) for stopping the reduction rotation of the reduction gear means when the pointer reaches a return zero position corresponding to the lower limit scale value of the analog value;
Drive signal input means (70, 80, 170) for inputting the drive signal to the field winding in accordance with an input (SV) representing the analog value;
Zero return signal input means (70, 80, 100, 131, 133, 133a, 134, 134a, 135, 135a) for inputting an alternating zero return signal to the field winding when returning the pointer to the return zero position. In a vehicle indicating instrument comprising:
Storage means (90) for preliminarily storing a predetermined electrical angle when the nulling signal advances to a phase angle corresponding to the zero level after the nulling signal is input to the field winding;
The field winding is cut off from the nulling signal during the rotation of the step motor based on the nulling signal input to the field winding by the nulling signal input means. First determination means (132a to 132d, 133c to 133f) for determining that the zero position is detected when the induced voltage of the magnetic winding becomes equal to or lower than a predetermined low voltage indicating the stop of the reduction gear rotation of the reduction gear means by the stopper means. , 134c to 134f, 135c to 135f),
Along with the determination of the detection of the zero position by the first determination means, the phase angle of the null signal is an electric angle corresponding to the predetermined electric angle and the zero level of the null signal before and after the electric angle. Second determination means (240) for determining whether or not the vehicle has advanced to either
When it is determined that the second determination means has advanced to either the predetermined electrical angle or an electrical angle corresponding to the zero level of the null signal before and after the electrical angle, the zero determination by the first determination means Third determination means (140) for determining that detection is correct;
When the third determination means determines that the determination of the detection of the zero position is not correct, the zero return signal input to the field winding by the return zero signal input means and the first and second Fourth determination means (150) for determining whether or not the determination by the determination means has been repeated a specified number of times,
When it is determined that the fourth determination means has not repeated the specified number of times, the return zero signal input to the field winding by the return zero signal input means and the determination by the first and second determination means are performed. A vehicle indicating instrument characterized by repeating again. The third determination means may perform the second determination while the input of the null signal to the field winding by the null signal input means and the determination by the first and second determination means are repeated the specified number of times. When it is determined that the means has advanced to either the predetermined electrical angle or an electrical angle corresponding to the zero level of the null signal before and after the electrical angle, it is determined that the determination of detection of the zero position is correct. ,
The fourth determination unit is configured to input the zero return signal to the field winding by the zero return signal input unit and repeat the determination by the first and second determination units the predetermined number of times, The vehicular indicating instrument according to claim 1, wherein the position detection is determined to be abnormal.

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