JP3654145B2 - 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, a stopper is projected from the scale plate at the return zero position of the pointer, and when the pointer is driven by the step motor and returned to the return zero position, the pointer is engaged with the stopper. There is something to let you do.
[0003]
[Problems to be solved by the invention]
By the way, in the indicating instrument, for example, a cosine wave drive voltage corresponding to the input is applied to the step motor, thereby giving an instruction by rotating the pointer.
[0004]
However, when returning the pointer to the zero return position, a zero return voltage is forcibly applied to the step motor. For this reason, in addition to the cosine wave drive voltage for causing the pointer to perform a normal pointing operation, the indicator instrument requires a separate nulling voltage for forcibly returning the pointer to its nulling position. There is.
[0005]
On the other hand, the present inventors generate the cosine wave drive voltage applied to the step motor on the outer peripheral surface of the magnet rotor of the step motor based on the cosine wave magnetic field generated in the field winding of the step motor. I examined the change of magnetic flux density.
[0006]
The magnetic flux density on the outer peripheral surface of the magnet rotor generated based on the cosine wave magnetic field of the field winding changes in a cosine wave shape in synchronization with the cosine wave magnetic field, but the rate of change of the magnetic flux density is the peak of the magnetic flux density. Sometimes the minimum value of the cosine wave drive voltage is small because the change is small, and when the magnetic flux density is zero, it is the maximum because the change is through the zero level of the cosine wave drive voltage.
[0007]
Such a phenomenon of changing the magnetic flux density occurs during the normal pointing operation of the pointer, but when the pointer is engaged with the stopper at its return zero position, the magnet rotor also stops simultaneously with the stop of the pointer. The change in magnetic flux density is eliminated.
[0008]
From the above, during the normal pointing operation of the pointer, when the pointer does not engage with the stopper, the rate of change of the magnetic flux density alternately repeats the minimum and maximum phenomenon, but the pointer is at its zero return position. It can be seen that the rate of change of the magnetic flux density becomes zero when engaged with the stopper.
[0009]
Therefore, if the change state of the change rate of the magnetic flux density when the cosine wave drive voltage passes through the zero level is known using the cosine wave drive voltage applied to the step motor, the pointer is engaged with the stopper at the return zero position. It can be accurately determined whether or not the two have been matched.
[0010]
In view of the above, the present invention pays attention to the above, and in a vehicular indicating instrument using a step motor as a driving source for a pointer, when an AC signal for instructing the pointer to be operated is input to the step motor. Using the phenomenon that the AC signal causes a large change in magnetic flux density in the field winding of the step motor, it is possible to ensure that the pointer reaches the return zero position accurately without relying on the extra voltage for return zero. The purpose is to do.
[0011]
[Means for Solving the Problems]
Upon solving the above problems, in the vehicle indicating instrument according to the invention of claim 1, an analog value display unit comprising display arcuately analog value toward the upper limit value from the lower limit value, the lower limit of the analog value display unit A scale plate having a stopper provided at a position corresponding to the value, and a pointer that is supported so as to rotate along the surface of the scale plate and engages with the stopper at a zero return position that specifies the lower limit value And a stator having a field winding that generates an AC magnetic flux by the input of an AC signal, and a magnet rotor that is coaxially supported in the stator and rotates according to the AC magnetic flux, A step motor for rotating the pointer in accordance with rotation of the magnet rotor; and input means for inputting the AC signal to the field winding .
[0012]
In the vehicle indicating instrument, an AC signal is allowed to be input from the input means to the field winding, and when the AC signal passes through a zero level, the field winding is cut off from the AC signal, and the field generated when the AC signal is cut off. A determination means for determining whether or not the magnet rotor is stopped due to the engagement with the pointer stopper based on the induced voltage of the winding is provided.
[0013]
Thus, when an AC signal for instructing the pointer is input to the step motor, the AC signal uses a phenomenon that causes a large change in magnetic flux density in the field winding of the step motor. Therefore, it is possible to accurately secure the arrival of the zero return position, that is, the engagement of the pointer with the stopper.
The inventions according to claims 2 and 3 also have the same effects as the invention according to claim 1.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment 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.
[0016]
As shown in FIGS. 1 and 2, the indicating instrument includes an instrument panel 10. As shown in FIG. 1, the instrument panel 10 is provided with a scale plate 10a. The scale plate 10a has a circle from a lower limit value (vehicle speed zero km / h) to an upper limit value (vehicle speed 180 km / h). A vehicle speed display portion 11 that displays in an arc shape is formed.
[0017]
The indicating instrument also includes a pointer 20, a rotary inner unit 30, and a wiring board 40. The pointer 20 is supported by a tip end portion of a pointer shaft 31 described later at the rotation base portion 21 and is rotated along the surface of the dial 10a. The pointer 20 is configured to rotate over the entire range of the arcuate vehicle speed display portion 11 of the scale plate 10a. The pointer 20 is attached to the stopper 13 provided on the scale plate 10a at the return zero position. It is designed to engage. The stopper 13 protrudes toward the surface side of the scale plate 10a at the position shown in FIG. 1 (corresponding to the nulling position).
[0018]
The rotating inner unit 30 is assembled from the back side to the wiring board 40 provided on the back side of the instrument panel 10 at a position corresponding to the scale plate 10a. The rotating inner unit 30 includes a pointer shaft 31 and an inner unit main body 32. The internal unit main body 32 includes a two-phase step motor M (see FIGS. 3 and 4) and a reduction gear train (not shown), and the internal unit main body 32 is accompanied by the rotation of the step motor M. By the reduction rotation of the reduction gear train, the pointer shaft 31 supported coaxially with the output gear of the reduction gear train is rotated. The pointer shaft 31 extends through the wiring board 40 and the through hole 12 of the scale plate 10a so as to be rotatable.
[0019]
As shown in FIG. 3, the step motor M includes a stator 30a and a magnet rotor 30b. The stator 30a includes a yoke 33 and both field windings 34a and 34b. The yoke 33 includes pole-shaped magnetic poles 33a and 33b. A field winding 34a is wound around the magnetic pole 33a, and a field winding 34b is wound around the magnetic pole 33b.
[0020]
The magnet rotor 30b is supported in the yoke 33 so as to be coaxial and rotatable with the yoke 33. On the outer circumferential surface of the magnet rotor 30b, there are N and S poles along the circumferential direction. A plurality of magnets are alternately magnetized. As the magnet rotor 30b rotates, the outer surface of the magnet rotor 30b faces the tip surface of each of the magnetic poles 33a and 33b of the yoke 33 with a narrow gap on the N pole and / or S pole. It has become.
[0021]
In the step motor M configured as described above, when cosine-wave drive voltages (to be described later) having different phases are applied to the corresponding field windings 34a and 34b, the field windings 34a and 34b are applied to the field windings 34a and 34b. Cosine-shaped magnetic fluxes generated by the flowing current are generated with different phases (for example, 90 degrees) and flow through the yoke 33 and the magnetic poles of the magnet rotor 30b. Thereby, the magnet rotor 30b rotates.
[0022]
Next, an electric circuit configuration for the step motor M will be described with reference to FIG. The microcomputer 50 executes a computer program according to the flowchart shown in FIG. 5, and during this execution, performs a process of driving the step motor M via both drive circuits 60a and 60b in accordance with the detection output of the vehicle speed sensor S. . The microcomputer 50 is operated by being supplied with power from the battery Ba via the ignition switch IG. The computer program is stored in advance in the ROM of the microcomputer 50.
[0023]
The vehicle speed sensor S detects the vehicle speed of the passenger car. The drive circuits 60 a and 60 b apply cosine wave drive voltages having different phases to the field windings 34 a and 34 b of the step motor M under the control of the microcomputer 50. In the present embodiment, the field winding 34a is referred to as an A-phase field winding, and the field winding 34b is referred to as a B-phase field winding. Accordingly, the drive voltage to the field winding 34a is referred to as A-phase drive voltage, and the drive voltage to the field winding 34b is referred to as B-phase drive voltage.
[0024]
Here, the application of the drive voltage from the drive circuit 60 a to the field winding 34 a is performed via both changeover switches 70 and 80. Both changeover switches 70 and 80 are each composed of an analog switch that is controlled to be switched by the microcomputer 50. The changeover switch 70 is connected to the fixed contact 71 connected to the one-side output terminal 61 of the drive circuit 60a and the open state. And a switching contact 73 connected to one terminal of the field winding 34a. The changeover switch 80 is connected to the fixed contact 81 connected to the other output terminal 62 of the drive circuit 60a, the fixed contact 82 connected to the input port 51 of the microcomputer 50, and the other terminal of the field winding 34a. The switching contact 83 is provided.
[0025]
As a result, in both the changeover switches 70 and 80, the switching contact 73 is input to the fixed contact 71 (hereinafter referred to as a first input state) and the switching contact 83 is input to the fixed contact 81 (hereinafter referred to as the first input state). The drive circuit 60a applies the output voltage to the field winding 34a. When the switching contact 73 is switched to the fixed contact 72 (hereinafter referred to as a second charging state) and the switching contact 83 is switched to the fixed contact 82 (hereinafter referred to as a second charging state), the field winding is performed. The line 34a is cut off from the output voltage of the drive circuit 60a, and the terminal voltage of the field winding 34a at this time is input to the input port 51 of the microcomputer 50 through the switching contact 83 and the fixed contact 82 of the changeover switch 80. Is done.
[0026]
In the present embodiment configured as described above, it is assumed that the passenger car is in a traveling state with the ignition switch IG turned on. Then, when the microcomputer 50 is operated by being powered by the battery Ba when the ignition switch IG is turned on, the microcomputer 50 starts executing the computer program according to the flowchart of FIG.
[0027]
Accordingly, in step 100, processing for switching both the changeover switches 70 and 80 to the first input state is performed. As a result, both the changeover switches 70 and 80 are switched to the first input state by the microcomputer 50 to connect the drive circuit 60a to the field winding 34a.
[0028]
Next, in step 110, output processing of the cosine wave drive voltages of the A phase and the B phase to the drive circuits 60a and 60b is performed. Along with this, the drive circuit 60a applies the A-phase drive voltage from the microcomputer 50 to the field winding 34a via both the changeover switches 70 and 80, and the drive circuit 60b receives the B-phase drive from the microcomputer 50. A voltage is applied to the field winding 34b.
[0029]
Therefore, a current based on the A phase driving voltage flows through the field winding 34a to generate a cosine wave-shaped magnetic flux, and a current based on the B phase driving voltage flows through the field winding 34b to generate a cosine wave-shaped magnetic flux. Occur. These two magnetic fluxes pass through the magnet rotor 30b while changing at different levels according to the change in the phase. Therefore, the magnet rotor 30b rotates. Accordingly, the turning inner unit 30 turns the pointer 20 via the pointer shaft 31 as the magnet rotor 30b rotates. The relationship between the rotation angle of the pointer 20 and the phase of each driving voltage of the A phase and the B phase is uniquely determined.
[0030]
In such a state, it is determined in step 120 whether or not the A-phase drive voltage is at a zero level. If the A-phase drive voltage is not zero level, the determination in step 120 is NO, and in step 121, the output processing of both drive voltages in step 110 is continued. For this reason, both drive circuits 60a and 60b rotate the step motor M according to the phase difference based on both the A-phase and B-phase drive voltages from the microcomputer 50. Accordingly, the rotation of the pointer 20 is continued.
[0031]
On the other hand, when the determination in step 120 is YES, since the A-phase drive voltage is at the zero level, in step 122, both changeover switches 70 and 80 are switched to the second on state. Therefore, both changeover switches 70 and 80 are switched to the second input state by the microcomputer 50.
[0032]
As a result, the field winding 34a is brought into an open state by inserting the switching contact 73 into the fixed contact 72 at one terminal thereof, and is connected to the fixed contact 82 of the switching contact 83 at the other terminal. When input, it is connected to the input port 51 of the microcomputer 50. In addition, when the changeover switches 70 and 80 are switched to the second input state, an induced voltage generated in accordance with the rotation of the magnet rotor 30b in the field winding 34a is input to the microcomputer 50 through the input port 51 in step 123. Is done.
[0033]
Accordingly, in step 130, it is determined whether or not the induced voltage in step 123 is equal to or lower than the threshold voltage. In the present embodiment, the threshold voltage is set to almost zero voltage.
[0034]
Here, the reason why the A-phase driving voltage is zero level as the determination criterion in step 120 and the threshold voltage in step 130 is set to substantially zero voltage will be described.
[0035]
The level of the A phase driving voltage changes in a cosine wave shape with the change in the phase of the A phase driving voltage. The level of the A-phase driving voltage becomes zero at a phase corresponding to a quarter cycle, and changes from positive to negative before and after the phase. Accordingly, since the magnetic flux density corresponding to the A-phase driving voltage due to this change also changes, the rate of change of the magnetic flux density is large (see the position of the rotation angle 90 degrees of the magnet rotor 30b in FIG. 6). Therefore, the voltage (induced voltage) induced in the field winding 34a due to the magnetic flux density having a large change rate greatly changes (see FIG. 7).
[0036]
On the other hand, the level of the A-phase drive voltage is substantially maintained at an extreme value before and after the phase corresponding to the peak (see the position of the rotation angle of the magnet rotor 30b of 180 degrees). Accordingly, since the magnetic flux density corresponding to the A-phase driving voltage at this time hardly changes, the rate of change of the magnetic flux density is very small (see FIG. 6). Therefore, the voltage (induced voltage) induced in the field winding 34a due to the magnetic flux density with such a small change rate is also very small.
[0037]
When the pointer 20 is engaged with the stopper 13 at the return zero position, the rotation of the magnet rotor 30b is stopped. Accordingly, since the magnet rotor 30b does not cut the magnetic flux corresponding to the A-phase drive voltage, the induced voltage of the field winding 34a at this time is zero.
[0038]
As described above, in order to determine that the pointer 20 is engaged with the stopper 13, it is possible to determine with high accuracy and timing by using the case where the change rate of the magnetic flux density is large. Therefore, in this embodiment, the zero level of the A-phase driving voltage that generates a magnetic flux density with a large change rate is adopted as the determination criterion in step 120, and the threshold voltage is set to substantially zero voltage.
[0039]
If the induced voltage of the field winding 34a is higher than the threshold voltage, the pointer 20 is not engaged with the stopper 13 and the step motor M is rotating, so that the induced voltage is the rate of change in magnetic flux density. This corresponds to a voltage in a large state. Therefore, the determination in step 130 is NO.
[0040]
On the other hand, if the induced voltage of the field winding 34a is equal to or lower than the threshold voltage, the induced voltage is originally a voltage that should generate a magnetic flux density with a large change rate, but is equal to or lower than the threshold voltage. The magnet rotor 30b is stopped by the engagement of the pointer 20 with the stopper 13. Therefore, it is determined in step 131 that the pointer 20 is engaged with the stopper 13.
[0041]
In this case, as described above, immediately after determining that the A-phase driving voltage is zero level in step 120, it is determined in step 130 whether or not the induced voltage of the field winding 34a is equal to or lower than the threshold voltage. The determination of NO or YES can be made with good accuracy and timing. Therefore, it is possible to accurately determine whether or not the pointer 20 has reached the return zero position, in other words, whether or not the pointer 20 is engaged with the stopper 13. As a result, the engagement of the pointer 20 with the stopper 13 can be ensured with high accuracy.
[0042]
As described above, when the determination in step 130 is NO, in step 140, the process of switching both the changeover switches 70 and 80 to the first on state is performed. Along with this, the application of the A-phase drive voltage from the drive circuit 60a to the field winding 34a is substantially in phase with the phase at the time when the changeover switches 70 and 80 are switched to the second on state in step 122. Done. For this reason, the step motor M rotates normally without stepping out.
[0043]
Further, after the processing in step 131, it is determined in step 150 whether or not the ignition switch IG is turned off. Here, if the ignition switch IG is on, the determination in step 150 is NO, and the same processing in step 140 as described above is performed. Also in this case, the application of the A-phase drive voltage from the drive circuit 60a to the field winding 34a is substantially in phase with the phase at the time of switching the two switches 70 and 80 to the second on state in step 122. Done. For this reason, the step motor M rotates normally without stepping out. Note that if the determination in step 150 is YES, the processing of the microcomputer 50 ends. At this time, both drive voltages 60a and 60b end their outputs.
[0044]
In the implementation of the present invention, the drive voltage applied to the field winding of the step motor M is not limited to the cosine wave voltage, but may be an AC voltage such as a sine wave voltage, a trapezoidal wave voltage, a triangular wave voltage, or an AC current. Any AC signal may be used.
[0045]
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.
[0046]
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 view of the indicating instrument of FIG.
FIG. 3 is a schematic cross-sectional view of a step motor built in the rotary inner unit of FIG. 2;
4 is an electric circuit configuration diagram for the step motor of FIG. 3; FIG.
FIG. 5 is a flowchart showing the operation of the microcomputer of FIG. 4;
FIG. 6 is a timing chart showing the magnetic flux density generated in the step motor and the rate of change in relation to the rotational position of the magnet rotor.
FIG. 7 is a timing chart showing the induced voltage of the field winding when the A-phase drive voltage passes through the zero level during rotation of the magnet rotor.
[Explanation of symbols]
10a, 10b ... Scale plate, 11 ... Vehicle speed display, 13 ... Stopper,
20 ... pointer, 30a ... stator, 30b ... magnet rotor,
34a, 34b ... field winding, 50 ... microcomputer,
60a, 60b ... drive circuit, 70, 80 ... changeover switch,
M: Step motor.

Claims (3)

A scale plate having an analog value display unit that displays an analog value in an arc shape from a lower limit value to an upper limit value, and a stopper provided at a position corresponding to the lower limit value of the analog value display unit,
A pointer that is supported so as to rotate along the surface of the scale plate and that engages the stopper at a null position that specifies the lower limit value;
A stator having a field winding that generates an AC magnetic flux by the input of an AC signal;
A stepper motor that is rotatably supported coaxially in the stator and rotates according to the alternating magnetic flux, and that rotates the pointer as the magnet rotor rotates;
In a vehicle indicating instrument comprising input means for inputting the AC signal to the field winding,
Allowing the input of the AC signal from the input means to the field winding, and shutting off the field winding from the AC signal when the AC signal passes through a zero level, and the field generated when the AC signal is cut off. An indicator for a vehicle, comprising: determination means for determining whether or not the magnet rotor is stopped when the pointer is engaged with the stopper based on an induced voltage of a winding. A scale plate having an analog value display unit that displays an analog value in an arc shape from a lower limit value to an upper limit value, and a stopper provided at a position corresponding to the lower limit value of the analog value display unit,
A pointer that is supported so as to rotate along the surface of the scale plate and that engages the stopper at a null position that specifies the lower limit value;
A stator provided with a field winding for generating an AC magnetic flux by the input of an AC signal; and a magnet rotor that is rotatably supported coaxially in the stator and rotates according to the AC magnetic flux. a step motor for rotating the pointer with the rotary,
In a vehicle indicating instrument comprising input means for inputting the AC signal to the field winding,
A change-over switch having a first closing state that allows the input of the AC signal from the input means to the field winding, and a second closing state that blocks the field winding from the AC signal;
First determination means for determining when the AC signal passes through a zero level when the changeover switch is in the first input state;
When it is determined by the first determination means that the AC signal passes through a zero level, a change control means for changing the changeover switch to the second input state;
Means for inputting an induced voltage of the field winding generated when the changeover switch is switched to the second input state by the changeover control means;
A vehicle indicating instrument comprising: a second determination unit configured to determine whether or not the magnet rotor is stopped when the pointer is engaged with the stopper based on the input induced voltage. A scale plate having an analog display that displays an analog straight line in an arc shape from the lower limit value to the upper limit value, a stopper provided at a position corresponding to the lower limit value of the analog value display portion, and a surface of the scale plate A pointer that is supported so as to rotate along and that engages with the stopper in a nulling position that specifies the lower limit straight;
A stator provided with a field winding for generating an AC magnetic flux by the input of an AC signal; and a magnet rotor that is rotatably supported coaxially in the stator and rotates according to the AC magnetic flux. A stepping motor that rotates the pointer with rotation of
A drive circuit for applying a drive voltage to the field winding;
A changeover switch having a first input state that allows input of the drive voltage to the field winding, and a second input state that blocks the field winding from the AC signal;
A microcomputer for controlling the driving of the step motor by outputting the driving voltage to the driving circuit;
The microcomputer is
Means for controlling the changeover switch to the first input state and outputting a drive voltage for rotating the magnet rotor to the drive circuit;
Means for determining whether the drive voltage is at a zero level;
Means for controlling the changeover switch to the second on state when it is determined that the drive voltage is at a zero level;
Means for inputting an induced voltage of the field winding generated when the changeover switch is switched to the second input state;
Means for determining whether or not the input induced voltage is equal to or less than a threshold voltage, and determining whether or not the magnet rotor is stopped when the pointer is engaged with the stopper when the voltage is equal to or less than the threshold voltage. A vehicle indicating instrument characterized by comprising.

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