JP2537286B2 - Meter drive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a meter driving device, and more particularly to a meter driving device for removing an abnormal indication of the meter when the driving power is turned on and off and driving the meter accurately.

[Prior Art] Conventionally, a meter for giving a predetermined angle azimuth to an indicator needle according to an input amount and visually displaying the input amount is well known, and in particular, a current according to the input amount is applied to two exciting coils orthogonal to each other. A cross-coil meter that generates a magnetic field and gives a torque to a magnet rotatably supported by the magnetic field to indicate the angular orientation is widely used in speedometers, tachometers, and the like of automobiles.

FIG. 3 shows a schematic configuration diagram of a drive device for driving the cross coil meter.

Detection pulse signals from the speed sensor and the rotation speed sensor are input to the cycle detection circuit 14. The cycle detection circuit 14 detects the cycle T of the input pulse signal by counting the number of pulses of the reference clock signal generated by the reference clock generator 16 and divided by the frequency divider 20 into an appropriate frequency. On the other hand, the detected analog signal sent from the fuel sensor or the like is converted into a digital signal by the A / D converter 10 and input to the control CPU 12 that controls the system.

The pulse signal whose period T has been detected by the period detection circuit 14 is input to the arithmetic processing block 18 which performs various arithmetic processes,
Based on the parameters in the memory 22 supplied from the control CPU 12, frequency calculation 1 / T, meter shake angle θ, sin, cos calculation and the like are performed. Then, the calculation result is supplied to the two pulse width modulation circuits (PWM) 24a and 24b for sin and cos for pulse width modulation, and is further supplied to the drivers 26a and 26b and the two exciting coils L _S orthogonal to each other. Also, L _C is excited to generate a magnetic field. Since the generated magnetic field gives an angle azimuth according to the input amount, a torque is applied to the magnet rotatably supported, and the pointer fixed to this magnet indicates the angle azimuth according to the input amount. .

[Problems to be Solved by the Invention] As described above, in the conventional meter driving device that drives the cross-coil meter, the pulse width-modulated current based on the output signal from the arithmetic processing block 18 is directly fed to the drivers 26a and 26b. However, there is a problem that the meter cannot be accurately instructed according to the input amount when the driving power of the drivers 26a and 26b is turned on and off.

The possible causes are as follows. That is,
When the ignition of the vehicle is turned off, the normal drivers 26a and 26b are in the OFF state of the applied voltage 0. This is because, unlike a logic system such as the control CPU 12, the drivers 26a and 26b, which are analog systems, consume a large amount of power when a current flows. When the vehicle ignition is turned on and the driving power for the drivers 26a and 26b is turned on, the driver 2
The voltage of a and 26b rises and the control CPU12 starts operating, but in this way the CPU does not receive the reference clock signal and the clock signal is input from the operation stop state (so-called sleep state) and the normal operation state In general, the input analog signal from the sensor is not always able to output deterministic data immediately when moving to, and therefore the CPU may malfunction and the data may become indeterminate. Then, since the drivers 26a and 26b drive the exciting coils by the uncertain value, there is a problem that the meter gives an inaccurate instruction that does not correspond to the input amount.

Further, even when the driver drive power supply is turned off, the voltage drops below the operating voltage, so that the drivers 26a and 26b cannot operate normally and the meter operates abnormally.

The present invention has been made in view of the above conventional problems,
An object of the present invention is to provide a meter driving device capable of preventing an abnormal operation of the meter when the driving power source is turned on and off and giving an accurate meter instruction according to an input amount.

[Means for Solving the Problem] In order to achieve the above object, the meter driving device of the present invention is a processing unit that calculates a current amount according to an input amount to be metered, and a current amount from the processing unit. A meter driving device for inputting a signal and driving the meter by energizing the meter indicating means according to the current amount signal, and performing a meter instruction according to the input amount. Is provided with an output control means for outputting an instruction permission signal when a predetermined time has elapsed from the time when the drive power of the drive means is turned on, and for stopping the output of the instruction permission signal when a predetermined time has passed after the power is turned off. A logic gate circuit for outputting the current amount signal to the drive means only when the output from the control means is an instruction permission signal, and the drive power supply is turned on,
The feature is that the abnormal meter indication at the time of OFF is removed.

[Operation] The meter driving device of the present invention has the above-mentioned configuration, and controls the permission or prohibition of the meter instruction on the CPU side. That is, the CPU does not output the instruction permission signal from the output control means to the logic gate circuit from the time when the driver drive power is turned on until the correct data can be supplied after a predetermined time elapses. Prohibit meter reading. Then, the CPU outputs the instruction permission signal from the output control means to the logic gate circuit only after normal operation processing becomes possible after a predetermined time has passed since the driver drive power was turned on.

Note that the CPU does not output the instruction permission signal until the predetermined time elapses after the driver drive power is turned on, so the meter is in the instruction prohibition state, in other words, the CPU outputs the instruction prohibition signal during this period. It is also possible to eliminate the abnormal meter indication when the drive power is turned on.

Further, even when the driver drive power is turned off, the CPU stops outputting the instruction permission signal and prohibits the meter instruction when the drive voltage drops after a predetermined time and the driver cannot operate normally.

In this way, the CPU does not output the instruction permission signal during the period when the data is indeterminate and the period when the driver cannot perform the normal operation, and the meter instruction is prohibited.
The meter error indication is removed.

[Embodiment] A preferred embodiment of a meter driving device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration block diagram of the present embodiment. Similar to the prior art, the detection pulse signals from the speed sensor and the rotation speed sensor (not shown) are input to the cycle detection circuit 14, generated by the reference clock generator 16 and divided by the frequency divider 20 to an appropriate frequency. The period T of the input pulse signal is detected by counting the number of pulses of the reference clock signal. Also, the detected analog signal sent from a fuel sensor (not shown)
It is converted into a digital signal by the A / D converter 10 and input to the control CPU 12 that controls the system.

The pulse signal whose period T has been detected by the period detection circuit 14 is input to the arithmetic processing block 18 which performs various arithmetic processes,
Based on the parameters in the memory 22 supplied from the control CPU 12, frequency calculation 1 / T, meter shake angle θ, sin, cos calculation and the like are performed. Then, the calculation result is supplied to the two pulse width modulation circuits (PWM) 24a and 24b for sin and cos for pulse width modulation, and is further supplied to the drivers 26a and 26b and the two exciting coils L _S orthogonal to each other. It is also configured to excite L _C to generate a magnetic field.

In this embodiment, four switching transistors are combined as the drivers 26a and 26b, and these switching transistors are sequentially turned on and off to generate two pulse width-modulated currents in the two exciting coils L _S and L _C which are orthogonal to each other. Is configured to energize.

Now, the characteristic of this embodiment is that the control CPU 1
An output control line 28 is provided as an output control means in 2, and the output from the pulse width modulation circuits 24a, 24b is output according to the output value of the control CPU 12 output via the output control line 28 from the driver 2a, That is, the logic gate circuits 30a and 30b for determining whether or not to supply to 26b are provided. The logic gate circuits 30a and 30b are composed of a plurality of AND gates and NAND gates, and are configured to receive signals from the output control line 28 and the pulse width modulation circuits 24a and 24b and output them to the drivers 26a and 26b.

The operation of this embodiment will be described below with reference to the timing chart of FIG. When the vehicle ignition is off, the system power supply voltage shown in FIG. 2 (a) is applied to the control CPU 12, the cycle detection circuit 14, etc., but the oscillation of the reference clock generator 16 is off. , The system and drivers 26a, 26b are in a stopped state.

When the vehicle ignition is turned on, the power supply voltage of the drivers 26a and 26b rises as shown in FIG. 2 (b), and the control CP
U12 detects this voltage rise and oscillates the reference clock oscillator 16 to start the operation. During this time, as shown in FIG. 2D, a 0 level signal is output to the output control line 28 as an instruction prohibition signal in order to prohibit the meter instruction. As described above, the logic gate circuit 30 connected to the output control line 28
a and 30b are composed of AND gates and NAND gates. Therefore, when the output control line 28 is at 0 level, the ground side transistors of the drivers 26a and 26b are turned off and the cross coils L _S and L _C are not energized. , The meter turns off.

Then, after a predetermined time has elapsed, the detection signal from the sensor is input, sin, cos calculation, etc. are performed, and after the calculation result is set in the pulse width modulation circuits 24a, 24b, the control CPU 12
Outputs a 1-level signal as an instruction permission signal to the output control line 28. Then, the logic gate circuits 30a and 30b supply signals to the drivers 26a and 26b in accordance with the signals from the pulse width modulation circuits 24a and 24b, and energize the exciting coils L _S and L _C to drive the meter.

When the vehicle ignition is turned off, the driver 2
Although the power supply voltage of 6a and 26b decreases and normal operation cannot be performed, the control CPU 12 detects this voltage decrease and outputs the 0 level signal to the output control line 28 again to turn off the meter drive.
To prevent abnormal output. That is, even if the driver drive power is turned off, the analog driver does not immediately stop its operation, but the drive voltage gradually decreases as shown in FIG. Then, during that time, data is continuously supplied on the CPU 12 side, but the drivers 26a and 26b cannot operate normally because of the low voltage, and an abnormality is indicated. So CP
U12 monitors the driver voltage, and outputs the output control line when the driver drive voltage drops below the specified voltage after the drive power is turned off.
The 0 level signal is output to 28 to forcibly turn off the driver to prevent abnormal operation.

Even if the driver drive power is turned off, since the system power is supplied to the CPU 12 as described above, the CPU 12 operates normally and can output the 0 level signal deterministically to the output control line 28 and force the driver. After being turned off, the CPU 12 shifts from the normal operation state to the operation stop state (sleep state).

As described above, in this embodiment, the output control line 28 for permitting or prohibiting the output by the digital signals of 0 level and 1 level and the logic gate circuits 30a and 30b composed of a plurality of AND gates and NAND gates are newly provided. Driver 26
When the drive power for a and 26b is turned on, the pulse width modulation circuit 2
The CPU prohibits output until accurate data is set in 4a and 24b, and when the drive power is off, the CPU prohibits output when the voltage reaches a value at which the drivers 26a and 26b cannot operate normally. , It is possible to remove the abnormal output of the meter by cutting off the signal supply to the driver when the driver power is turned on and off.

[Effects of the Invention] As described above, according to the meter driving device of the present invention, it is possible to eliminate an abnormal meter instruction when the driver driving power supply is turned on and off and to give a highly reliable meter instruction.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an embodiment of a meter driving device according to the present invention, FIG. 2 is a timing chart diagram showing the operation of the same embodiment, and FIG. 3 is a configuration block diagram of a conventional meter driving device. . 10 …… A / D converter 12 …… Control CPU 14 …… Cycle detection circuit 16 …… Reference clock generator 18 …… Computation processing block 24 …… Pulse width modulation circuit 26 …… Driver 28 …… Output control line 30 ...... Logic gate circuit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masakazu Kobayashi 2-1910 Nisshin-cho, Omiya-shi, Saitama Kanto Seiki Co., Ltd. (72) Masanori Narita 2-1910 Nisshin-cho, Omiya-shi, Saitama Kanto Within Seiki Co., Ltd. (56) References: Showa 58-63568 (JP, U)

Claims (1)

(57) [Claims] 1. A processing means for calculating a current amount according to an input amount to be indicated by a meter, and a current amount signal from the processing means is inputted, and the meter indicating means is energized according to the current amount signal to supply a meter. A meter driving device for driving a meter according to an input amount, the driving means driving the driving means, and outputting an instruction permission signal when a predetermined time has passed after the processing means turns on the driving power of the driving means. In addition, an output control means is provided for stopping the output of the instruction permission signal when a predetermined time has elapsed since the driving power was turned off, and the current amount signal is driven only when the output from the output control means is the instruction permission signal. A meter driving device, which is equipped with a logic gate circuit for outputting to a means, and removes an abnormal meter indication when the driving power is turned on and off.