JPH0243148B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary of the Invention] Focusing on the fact that the pointer deflection angle changes by changing the amount of current applied to each cross coil by changing the duty of the square wave, the duty determination data corresponding to the digital data was created. Prepared in advance, select duty determination data corresponding to the input digital data, generate a rectangular wave whose duty is determined by the selected duty determination data, and apply it to each cross coil during different levels of the rectangular wave. A current is applied to each of them to display a predetermined display based on information input in digital format.

[Industrial application field]

The present invention relates to a drive device for a cross-coil type meter.

[Prior art and problems to be solved by the invention]

Traditionally, the information displayed on this type of instrument is
For example, the input is in the form of an analog voltage value generated by changing the resistance value in response to a change in the amount of liquid, and the deflection angle of the pointer changes as the analog voltage value changes.

The deflection angle of the pointer is determined by the direction of the composite vector of the magnetic field generated by each coil by passing current through a pair of coils arranged in an intersecting manner. In addition, the proportion of current flowing through each coil is directly changed using analog signals from sensors and other sources.

By the way, recently, in certain types of vehicles, various signal data generated inside the vehicle are collectively collected and processed as digital data on the on-board computer, and related to this, Most of the displays are digital.

However, even in vehicles where the digital processing of signal data has progressed in this way, many users desire that the display be performed by an analog meter with a pointer. In such cases, it is possible to deal with this by separately incorporating a circuit system that generates and processes analog signal data for display without using digital data for display. In addition to wasting the circuit to form, this has caused many problems such as the circuit becoming complicated and increasing the cost.

[Means for solving problems]

The present invention has been made in view of the problems of the conventional ones mentioned above.
It is an object of the present invention to provide a driving device for a cross-coil type instrument that can drive the cross-coil type meter using display information in which sensor signals have already been processed and converted into digital data. , determines the data input terminal to which the information displayed by the pointer deflection angle of the cross-coil type instrument is input in the form of digital data, and the duty of the square wave necessary to generate the pointer deflection angle corresponding to each digital data. storage means for storing duty determination data; means for taking in digital data input to the data input terminal and selecting duty determination data corresponding to the digital data from the storage means; Variable duty square wave generation means generates a duty square wave according to duty determination data, and a current is passed through one of the cross coils at one level of the square wave generated by the variable duty square wave generation means, and driver means for causing current to flow through the other of the cross coils at a level.

[Effect]

One of the cross coils is energized at one level of the rectangular wave generated by the variable duty rectangular wave generating means, and the other is energized at the other level of the rectangular wave. Since the duty determination data for the digital data to be displayed at the corner is determined by the duty determination data prepared in advance in the storage means, when the digital data is input, the duty required to display the data corresponding to the data is determined. The variable duty rectangular wave generating means generates a rectangular wave having a predetermined display.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a circuit block diagram of a drive device for a cross-coil type meter according to the present invention, and 1 is a data input terminal for inputting digital data containing information such as liquid volume.
A central processing unit (CPU) consisting of a microcomputer that receives data from the IN, processes digital data according to a predetermined program, and outputs data that determines the duty of the square wave. 2 is
This is a variable duty rectangular wave generation circuit that generates a rectangular wave with a duty according to the digital data based on the duty determination data outputted by processing the digital data by the CPU 1. 3a and 3b are cross coils disposed orthogonally to each other constituting the cross coil type meter 3, and one end of each cross coil 3a, 3b is connected to the + power source. 4a and 4b are drivers that receive the rectangular wave generated by the variable duty rectangular wave generation circuit 2 and send current to the cross coils 3a and 3b, respectively, and the output of each driver 4a and 4b is connected to the other end of the cross coils 3a and 3b. each connected. The driver 4a includes an amplifier _4a1 that noninverts and amplifies the rectangular wave from the variable duty rectangular wave generation circuit 2, and a switching transistor _4a2 that turns on when the output of the amplifier _4a1 is at H level, and generates a variable duty rectangular wave. The output of generation circuit 2 is H
A current is passed through the cross coil 3a during the level period. On the other hand, the driver 4b includes an amplifier _4b1 that inverts and amplifies the rectangular wave from the variable duty rectangular wave generation circuit 2, and a switching transistor _{4b2 that} turns on when the output of the amplifier 4b1 is at H level. A current is passed through the cross coil 3b while the output of the wave generating circuit 2 is at L level.

When the CPU 1 has an 8-bit configuration, digital data is handled in units of 8 bits, so the variable duty rectangular wave generating circuit 2 shown in FIG. 2, for example, is used.

In FIG. 2, 2a is an 8-bit shift register to which 8-bit duty determination data is input serially from the CPU 1, 2b is an 8-bit comparison counter to which a count-up clock is input from a clock generator (not shown), and 2c. compares the contents of the shift register 2a and comparison counter 2b, and sets the output to L while the shift register 2a is larger.
level, and when the comparison counter 2b becomes larger, the output is set to H level, and a rectangular wave with a duty corresponding to the duty determination data is outputted.

Now, if data 03H (hexadecimal) in the shift register 2a is set and the comparison counter 2b is reset, the magnitude comparator 2c compares the contents of the two and
is larger, so L level is output as the output. After that, the count up pulse is sent to the comparison counter 2b.
, and when the contents are incremented by 1, the value of the comparison counter 2b becomes 1, but since the contents of the shift register 2a are still larger, the output of the magnitude comparator 2c is at L level. However, if the comparison counter 2b continues to count up sequentially, the content of the comparison counter 2b becomes larger than the content of the shift register 2a, and at that point the output of the magnitude comparator 2c is inverted and becomes H level. Become.

Since the comparison counter 2b continues to count up after that, the output of the magnitude comparator 2c continues to take the H level. However, when the content of the comparison comparator 2b rolls over from FFH (hexadecimal) to 00H, the comparison counter 2c continues to count up. Since the content is smaller than that of the shift register 2a, the output of the magnitude comparator 2c is inverted again and becomes L level. By repeating the above operations, a rectangular wave with a duty of 3/256 can be continuously obtained. The contents of shift register 2a are replaced by duty determination data from CPU 1 only when changing the duty, and the value is 1/256 ~
It can be changed within the range of 256/256 (or 0/256 to 255/256).

Now, assume that the digital data input to the data input terminal IN is data indicating the liquid level of the fuel tank of the vehicle. The data is generated by an A-D converter that performs analog-to-digital (A-D) conversion with a predetermined resolution of the analog signal generated by the liquid level sensor. For example, the resolution is 1/16
If so, the data is 00000, 00001,...
It can be expressed as a 5-bit binary number such as 10000, but if CPU 1 has an 8-bit configuration, the data expressed using the lower 5 bits of 8 bits will be 8 bits.
It will be input to CPU1 in bit units.

On the other hand, the deflection angle θ of the pointer of the cross-coil type instrument 3
is determined by θ=tan ^-1 Ia/Ib, where Ia and Ib are the currents flowing through the cross coils 3a and 3b, respectively, and the present invention calculates the ratio of Ia and Ib between the H level and L level of the rectangular wave. The deflection angle is determined by θ=tan ⁻¹ (R _OUTY /1−R _OUTY ), that is, the duty ratio R _OUTY .

Therefore, as mentioned above, when inputting digital data with a resolution of 1/16, the deflection angle θ of the instrument pointer is θ ₀ = 0°, θ ₁ = θ 0 = 0°, assuming the span is 90°.
It is divided into 16 parts such as 5.625°, θ ₂ = 11.25°, ... θ ₁₆ = 90°, and the duty ratio R _OUTY for each deflection angle is as follows.

R _OUTY0 = 0 R _OUTY1 = 0.0897 R _OUTY2 = 0.1659 : R _OUTY15 = 0.9103 R _OUTY16 = 1 When using variable duty square wave generation circuit 2 configured as shown in Figure 2, a square wave with the above duty ratio is generated. To do this, the CPU 1 needs to output x for which x/256 is closest to the above duty ratio as the duty determination data, and for this purpose the CPU 1 stores the duty determination data x corresponding to the digital data in the read-only memory (ROM).
It has a table to output. In the above example, a table of digital data duty determination data x 00000 0 00001 23 00011 42 : : 01111 233 10000 255 may be prepared.

With the above configuration, when the CPU 1 takes in digital data from the data input terminal IN in step S1 as shown in the flowchart of FIG. 3, it checks whether the digital data has changed from the data that was taken in immediately before. is determined in step S2. If there is no change in the data and the determination is NO, the process returns to step S1 and the next digital data is acquired. If the judgment is YES, the duty determination data corresponding to the captured digital data is transferred to the next step.
The data is read from the table in the ROM in S3, and transferred to the shift register 2a of the variable duty rectangular wave generation circuit 2 in the subsequent step S4.

When the duty determination data is set in the shift register 2a, the comparison counter 2a is set at the same time.
After that, the magnitude comparator 2c repeatedly outputs a rectangular wave with a constant duty ratio determined by the duty determining data set in the shift register 2a until the duty determining data is changed. , which is applied to the drivers 4a and 4b. Drivers 4a, 4b
Since current flows through the cross coils 3a and 3b at the H and L levels of the rectangular wave, each cross coil 3
The direction of the composite vector of the magnetic fields generated by magnets a and 3b corresponds to the duty ratio, and the pointer of the meter 3 shows a deflection angle according to the digital data.

Although not specifically mentioned in the above explanation,
Depending on how the CPU 1 is programmed, settings such as the index and hysteresis of the paper needle can be changed freely, and display accuracy can be easily increased by increasing the resolution of the rectangular wave duty.

〔effect〕

As explained above, according to the present invention, the cross-coil type instrument can perform a predetermined display based on display information input in digital format, so that in an apparatus in which digital data is already prepared for digital display, In addition to easily converting the display to analog, if a microcomputer is installed for digital data processing, it can be easily implemented by adding a small amount of circuitry and changing the microcomputer's program. can get.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing one embodiment of the present invention, FIG. 2 is a block diagram showing a specific example of a part of FIG. 1, and FIG. 3 shows the operation of the central processing unit in FIG. FIG. 1...Central processing unit, 2...Variable duty square wave generation circuit, 3...Cross coil type instrument, 3
a, 3b...cross coil, 4a, 4b...driver.

Claims (1)

[Scope of Claims] 1. In a device for driving a cross-coil type instrument having a pair of cross coils arranged to intersect with each other, information to be displayed by a pointer deflection angle of the cross-coil type instrument is input in the form of digital data. a data input terminal that is input to the data input terminal; a storage means that stores duty determination data that determines the duty of the rectangular wave necessary to generate a pointer deflection angle that corresponds to each digital data; and a digital input terminal that is input to the data input terminal. means for capturing data and selecting duty determining data corresponding to the digital data from the storage means; variable duty square wave generating means for generating a square wave of duty according to the duty determining data selected by the selecting means; , driver means for passing current through one of the cross coils at one level of the rectangular wave generated by the variable duty rectangular wave generating means, and passing current through the other cross coil at the other level. Drive device for coil type instruments.