JPH0815325A - Cross coil meter - Google Patents

Abstract

PURPOSE:To sustain a desired conduction amount for a cross coil meter regardless of the temperature fluctuation. CONSTITUTION:Coefficients for correcting the fluctuation in the resistance of coil Ls, Lc due to the temperature are stored in a memory 24. A temperature sensor 50 detects the temperature of a cross coil meter 30 and the output from a microcomputor 20 is corrected by the correction coefficients read out from the memory 24. Current supply to the cross coil meter 30 is controlled based on a corrected command value thus feeding a desired current to the cross coil meter 30 regardless of the temperature fluctuation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cross coil meter used for displaying a vehicle speed of an automobile, and more particularly to a cross coil meter for supplying a predetermined pulse train to the cross coil to control an energization amount.

[0002]

2. Description of the Related Art Conventionally, there is a meter for displaying an analog value of a measured value measured by various sensors. For example, a meter for an analog display such as a speedometer or a tachometer is often used in an instrument panel of an automobile. .

[0003] Speedometers, tachometers, and the like have a wide range in which the needle can swing and move quickly. As a driving mechanism suitable for such a meter, there is a cross coil meter that controls the position of the pointer by controlling the amount of current supplied to two orthogonal coils.

In this cross coil meter, as shown in FIG. 7, a magnet M fixed to a needle is arranged in a magnetic field formed by two coils Ls and Lc which are orthogonal to each other. Then, the energization amount to the coils Ls and Lc is controlled, the turning position of the magnet M is determined, and the needle is swung. For example, if only the coil Ls is energized, the magnet M is oriented vertically, and if only the coil Lc is energized, the magnet M is oriented horizontally. By controlling the ratio of the amount of energization to both coils Ls, Lc, the magnet is inclined. Turn around. Also, by reversing the direction of the current, the direction of the magnet M will be 180 ° different. Then, the coil Ls,
By controlling the amount of electricity supplied to Lc, the needle is rotated 360 °
Can be shaken in the range.

In such a cross coil meter, the amount of current must be changed in the range of 0 to 100%. A PWM (pulse width modulation) control method is suitable for such a wide range of energization amount control, and PWM control is used for controlling the drive current of the cross coil meter.

[0006]

Here, the PWM control is for controlling the duty ratio of a pulse of a predetermined voltage, and for controlling the amount of current to the coil on the assumption that the voltage is constant. Is. Further, in the cross coil meter, since the position of the magnet (meter indication value) is determined by the ratio of the amount of electricity supplied to the two coils, the meter indication value does not change even if the voltage changes. That is, when the voltage changes, the energization amount to both coils changes, but the ratio between the two does not change, and the instruction value does not change. However, there is a problem that the needle easily shakes due to vibration or the like when the energization amount decreases. Further, when the voltage is increased, the amount of current increases, which causes a problem such as heat generation. Therefore, even in the cross coil meter, there is a demand to maintain the amount of electricity supplied to the coil to a predetermined value.

When a cross coil meter actually mounted on an automobile was investigated, it was found that the amount of current was reduced and the needle was easily shaken in some cases in use.
As a result of research on this point, in use,
It was found that the temperature of the cross coil meter was changed, the resistance value of the cross coil was changed accordingly, and the current amount was changed.

The present invention has been made based on such recognition, and an object of the present invention is to provide a cross coil meter capable of maintaining a desired amount of electricity to the cross coil meter.

[0009]

SUMMARY OF THE INVENTION The present invention is a cross coil meter for controlling the amount of electricity to the cross coil and giving an instruction according to the input value, and supplying a current according to the input value to the cross coil. Current command value generating means for generating a current command value for controlling the temperature, a temperature sensor for detecting the ambient temperature of the cross coil, and the current command value generating means according to the ambient temperature of the cross coil detected by the temperature sensor. Correction value storage means for storing a correction value for correcting the current command value generated by the correction value storage means, correction means for correcting the pulse command value based on the correction value stored in the correction value storage means, and Pulse train generating means for generating a pulse train to be supplied to the cross coil according to the pulse command value, and to obtain a predetermined drive current regardless of the temperature change of the cross coil. . Further, the pulse train generating means changes the generated pulse width per repeating cycle according to the input value while keeping the repeating cycle constant, and the correction value means changes the generated pulse width per repeating cycle according to the correction value. It is characterized by changing. Further, the pulse train generating means changes the number of generated pulses per predetermined time while keeping the pulse width of each pulse constant according to the input value, and the correction value means changes the number of generated pulses according to the correction value. It is characterized in that the above-mentioned predetermined time period that defines the above is changed. Further, the present invention is characterized in that the input value is a value regarding a vehicle speed obtained by a vehicle speed sensor of an automobile, and the vehicle speed is displayed by energizing a cross coil.

[0010]

As described above, according to the present invention, the amount of current supplied to the coil is controlled according to the temperature of the cross coil detected by the temperature sensor. Therefore, it is possible to compensate for a change in current amount due to a change in resistance value of the cross coil due to a change in temperature, and it is possible to supply a desired current. Therefore, it is possible to prevent the force for holding the needle at a predetermined position from being reduced, and it is possible to prevent an unnecessarily large amount of current from flowing through the coil to cause heat generation.

Further, the current amount can be controlled with a simple structure by changing the number of pulses in the repeating cycle and controlling the current supplied to the cross coil.

Further, by controlling the current supplied to the cross coil by changing the number of pulses in the repeating period, the current amount can be controlled with a simple structure.

Further, with the cross coil meter having such a structure, it is possible to provide a suitable vehicle speed meter capable of giving a stable indication even for vibration of the vehicle.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an example of a cross coil meter applied to a speed meter of an automobile. The vehicle speed sensor 10 generates a vehicle speed pulse according to the number of rotations of the tire, and the vehicle speed pulse is supplied to the microcomputer 20. The speed meter is, for example, as shown in FIG. 2, and the speed and the meter indicating position (angle of the magnet) are associated with each other on a one-to-one basis. Therefore, the meter indication position, that is, the magnet angle is determined according to the vehicle speed pulse. On the other hand, the cross coil meter 30 is composed of two orthogonal coils Ls and Lc and the magnet M, as in the conventional example, and the angle of the magnet M is determined by controlling the amount of electricity supplied to the sine coil Ls and the cosine coil Lc. It That is, as shown in FIG. 3, the angle of the magnet is determined by controlling the amount of current to the sine coil Ls and the cosine coil Lc. For example, when the angle is 0 °, the energization amount to the sine coil Ls is 0 and the energization amount to the cosine coil Lc is 1. Similarly, when the angle is 45 °, both the sine coil Ls and the cosine coil Lc are energized by 1 / √2, and the angle (meter indication value) is determined by the energized amount.

The microcomputer 20 counts the vehicle speed pulse from the vehicle speed sensor 10 and calculates the vehicle speed from the count value of a predetermined time. Then, the meter indicating angle is calculated based on the correspondence shown in FIG. The correspondence between the vehicle speed and the meter indicating angle may be stored in a memory in advance as a table. And the sine coil Ls corresponding to the meter indicated angle
Also, the amount of electricity supplied to the cosine coil Lc is calculated based on FIG. 3, and this is used as a current command value to generate the sine PWM generator 4
0 and the cosine PWM generator 42 respectively. The calculation of the energization amount (current command value) may be performed by sine and cosine calculations, or the correspondence may be stored as a table.

Sine PWM generator 40 and cosine P
The WM generator 42 generates a pulse train (PWM output voltage waveform) as shown in FIG. 4 according to the current command value supplied from the microcomputer 20. The example shown is a meter indicating angle 4
5 ° is shown, and as shown in FIG. 3, a current of 1 / √2 is applied to the sine coil Ls and the cosine coil Lc. Therefore, the sine PWM generator 40 and the cosine PWM generator 42 control the pulse width for each repetition period. That is, in this example, a state in which a high level of 1024 units is present during one repeating cycle is set to the current amount 1 and a unit of high level 0 corresponds to the current amount 0. Therefore, if the indicated angle is 45 °, 1024 × 1 / √2
There is a high level of = 724 units in one cycle. In addition,
In this example, one cycle is set to 20 msec. Also, such PWM generators 40, 42 can be easily formed by gating the pulses from the oscillator.

Then, such a pulse train has a sine P
From the WM generator 40 and the cosine PWM generator 42,
It is supplied to the drivers 44 and 46. Driver 44,
Reference numeral 46 includes a plurality of transistors, and supplies a current to the coils Ls and Lc of the cross coil meter 30 by turning on a predetermined transistor. Therefore, by supplying the supplied pulse train to the base of the transistor to be turned on, the time for which the transistor is turned on is controlled, and the average amount of current supplied to the corresponding coils Ls and Lc is controlled. As a result, the designated angle of the cross coil meter 30 is controlled to a predetermined angle, and the speed is displayed according to the detection value of the vehicle speed sensor 10.

In this embodiment, the temperature sensor 50 is attached near the cross coil meter 30, for example, in the meter case. The amount of current supplied to the cross coil meter 30 is corrected according to the temperature detected by the temperature sensor 50. Then, with this correction, the coils Ls,
Even if the resistance value of Lc changes with temperature, the current flowing therethrough becomes a predetermined value. The temperature sensor 50 may be any one as long as it can output the detected temperature as an electric signal.

The temperature detected by the temperature sensor 50 is supplied to the microcomputer 20. Microcomputer 20
Has a CPU 22 for performing calculations and the like, and a memory 24 for storing a temperature-dependent correction coefficient as a table. The CPU 22 has the PWM calculated as described above.
The energization amount instruction value to be supplied to the generators 40 and 42 is corrected by the correction coefficient from the memory 24 and then supplied to the PWM generators 40 and 42.

Here, the table stored in the memory 24 is as shown in FIG. 5, and the correction coefficient data k1 to k14 (numerical data) are stored according to the temperature. In this example, if the detected temperature is in the range of 0 to 10 ° C., the CPU 22 reads k which is the content of address 9.
9 is read out, this correction coefficient k9 is multiplied by the energization amount instruction value, and this is supplied to the PWM generators 40 and 42.

The correction coefficient is determined by the coils Ls and Lc.
This is obtained by investigating the amount of current flowing here by changing the temperature of. Therefore, by this correction, the amount of current flowing through the coils Ls and Lc can be maintained at a predetermined value regardless of the temperature. For example, the maximum value of the correction coefficient is set to 1, and the current amount required at the temperature at which the resistance is maximum is made to correspond to the above current value 1 (1024 units). Then, if the value of the correction coefficient k4 at 55 ° C. is 0.9,
The current command value is multiplied by 0.9, and this is multiplied by the PWM generator 4
Supply 0, 42. For example, if the indicated angle is 45 °, the output pulse width per cycle from the PWM generators 40 and 42 when there is no correction is 724 units, but the output pulse width is 652 units due to the correction. It is possible to prevent the current flowing through the coils Ls and Lc from being reduced by such a reduction in the pulse width, and the resistance value from changing due to the influence of temperature so that the current amount in the coils Ls and Lc is not a predetermined value. You can

Therefore, even if the temperature of the cross coil meter 30 changes, the driving current is maintained at a predetermined value and a predetermined driving force can be obtained. The correction described above is performed for the currents supplied to both the pair of coils Ls and Lc, and therefore does not affect the instruction value.

Further, in this embodiment, the CPU 22, P
The WM generators 40 and 42 and the drivers 44 and 46 are formed in one IC. Further, the memory 24 needs to retain its stored contents even when the power is turned off,
A non-volatile memory such as an EEPROM is used. The memory 24 is externally attached to the IC.

Next, in the above-described embodiment, the PWM generators 40 and 42 change the pulse width within the repetition period to control the amount of current to the cross coil meter 30, but the control method is different. Format is also acceptable.

For example, the number of pulses in the repetition period may be changed according to the energization amount instruction value, or the repetition period may be changed. That is, in the case of controlling the number of pulses within the repetition period, as shown in FIG. 6A, when the repetition period is B and the width of one pulse is A, the number of pulses is changed according to the current command value. Change n. As a result, the energization amount nA / B is changed. In this case, the correction coefficient k is multiplied by knA / B.

Further, in the case of the control of the repetition period, FIG.
As shown in (B), the repetition cycle T is changed according to the energization amount instruction value. That is, the repetition cycle T is corrected to T / k by the correction coefficient k. As a result, the number of pulses in the repeating cycle is the same, but the amount of electricity per unit time (for example, 1 second) is changed by changing the repeating cycle.

In the above example, the pulses are arranged from the beginning of the repeating cycle, but the pulses may be arranged in any way as long as the number of pulses in the repeating cycle becomes a predetermined number.

[0028]

As described above, according to the present invention,
The amount of current supplied to the coil is controlled according to the temperature of the cross coil detected by the temperature sensor. Therefore, it is possible to compensate for a change in current amount due to a change in resistance value of the cross coil due to a change in temperature, and it is possible to supply a desired current. Therefore, it is possible to prevent the force for holding the needle at a predetermined position from being reduced, and it is possible to prevent an unnecessarily large amount of current from flowing through the coil to cause heat generation.

Further, by changing the pulse width within the repetition period and controlling the current supplied to the cross coil, the current amount can be controlled with a simple structure.

Further, by controlling the current supplied to the cross coil by changing the number of pulses in the repeating cycle, the current amount can be controlled with a simple structure.

Further, with the cross coil meter having such a configuration, it is possible to provide a suitable vehicle speed meter capable of giving a stable indication even for vibration of the vehicle.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment.

FIG. 2 is a diagram showing a speedometer.

FIG. 3 is a diagram showing a relationship between a meter indication angle and a coil current.

FIG. 4 is a diagram showing an example of a PWM output voltage waveform.

FIG. 5 is a diagram showing a table regarding a relationship between temperature and a correction coefficient.

FIG. 6 is a diagram showing an example of an output voltage waveform of another control method.

FIG. 7 is a diagram showing a configuration of a cross coil meter.

[Explanation of symbols]

 10 vehicle speed sensor 20 microcomputer 22 CPU 24 memory 30 cross coil meter 50 temperature sensor

Claims (4)

[Claims] 1. A cross coil meter for controlling an amount of electricity to a cross coil and giving an instruction according to an input value, wherein a current command value for supplying a current according to the input value to the cross coil is generated. Current command value generating means, a temperature sensor for detecting the ambient temperature of the cross coil, and a current command value generated by the current command value generating means according to the ambient temperature of the cross coil detected by the temperature sensor. A correction value storage means for storing a correction value for correction, a correction means for correcting the current command value based on the correction value stored in the correction value storage means, and a cross coil according to the corrected pulse command value. And a pulse train generating means for generating a pulse train to be supplied to the cross coil meter, wherein a predetermined drive current is obtained regardless of temperature change of the cross coil. 2. The apparatus according to claim 1, wherein the pulse train generating means changes the generated pulse width per repeating cycle with a constant repeating cycle according to an input value, and the correction value means corrects the pulse width. A cross coil meter characterized in that the pulse width generated per repetitive cycle is changed according to the value. 3. The apparatus according to claim 1, wherein the pulse train generating means changes the number of generated pulses per predetermined time period while keeping the pulse width of each pulse constant according to the input value, A means for changing the above-mentioned predetermined time that defines the number of generated pulses according to a correction value. 4. The device according to claim 1, wherein the input value is a value regarding a vehicle speed obtained by a vehicle speed sensor of the vehicle, and the vehicle speed is displayed by energizing a cross coil. Characteristic vehicle speed meter.