Vehicle speed detector, method, and meter device

Abstract

To provide a vehicle speed detector, a method, and a meter device by which response time to the output of a vehicle speed pulse signal can be accelerated.SOLUTION: A meter device 1 comprises a signal conversion unit 11 that inputs, from a vehicle speed sensor 2 as an input signal, a vehicle speed pulse signal of four cycles per one rotation of a rotation axis AX rotating along with the rotation of a wheel T and converts the signal into a vehicle speed pulse signal of eight cycles per one rotation of the rotation axis AX to output it as an output signal. The signal conversion unit 11 is configured to: calculate a pulse width A of the first half square wave as a pulse width for one cycle of the first cycle in the output signal at the time when the first half square wave equivalent to the first half cycle of the first cycle in the input signal is inputted immediately after the input of the input signal is started; and output the square wave of the first cycle in the calculated output signal at the time when the input of the latter half square wave equivalent to the latter half cycle of the first cycle in the input signal is completed.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a vehicle speed detection device and method, and a meter device.

Background Art

[0002] Some meter devices input a vehicle speed pulse signal from a vehicle speed sensor mounted on a vehicle, calculate the vehicle speed of the vehicle based on the vehicle speed pulse signal, and then output a vehicle speed pulse signal corresponding to the vehicle speed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a conventional meter device, since the vehicle speed is calculated from the average value of the vehicle speed pulse signals for one rotation of the rotating shaft that rotates as the wheels rotate, after the input of a certain number of vehicle speed pulse signals is completed until the vehicle speed is determined, the vehicle speed pulse signal is output. For example, when the vehicle speed sensor outputs a vehicle speed pulse signal of 4 cycles per rotation of the rotating shaft, 4 cycles of vehicle speed pulse signals are required for vehicle speed calculation. Further, in such a meter device, regarding vehicle speed calculation, a response time of 4 cycles or more is required to obtain the true speed with respect to a change in vehicle speed.

[0005] An object of the present invention is to provide a vehicle speed detection device and method, and a meter device that can speed up the response time for output of a vehicle speed pulse signal.

Means for Solving the Problems

[0006] In order to achieve the above object, the vehicle speed detection device according to the present invention inputs, as an input signal, a vehicle speed pulse signal having N (N = natural number) cycles per rotation of a rotating shaft that rotates with the rotation of a wheel from a vehicle speed sensor, and converts it into a vehicle speed pulse signal having 2N cycles per rotation of the rotating shaft and outputs it as an output signal. The signal conversion unit calculates, at a time point when a first half rectangular wave corresponding to the first half cycle of the first cycle in the input signal is input immediately after the input of the input signal starts, the pulse width of the first half rectangular wave as the pulse width for one cycle of the first cycle in the output signal, and outputs the rectangular wave of the first cycle in the calculated output signal at a time point when the input of the second half rectangular wave corresponding to the second half cycle of the first cycle in the input signal is completed.

Advantages of the Invention

[0007] According to the vehicle speed detection device and method, and the meter device according to the present invention, there is an effect that the response time to the output of the vehicle speed pulse signal can be increased.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by the following embodiments. That is, the components in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same, and various omissions, replacements, and changes can be made without departing from the gist of the invention.

[0010] [Embodiment] FIG. 1 is a block diagram showing a schematic configuration of a meter device according to an embodiment. FIG. 2 is a timing chart showing the relationship between an input signal and an output signal of the meter device according to the embodiment. FIG. 3 is a flowchart showing the operation of the meter device according to the embodiment.

[0011] The meter device 1 shown in FIG. 1 is mounted on a vehicle and notifies a driver of the vehicle of various information regarding the vehicle. The meter device 1 is disposed, for example, on an instrument panel in front of the driver's seat. The meter device 1 is connected to a vehicle speed sensor 2 and vehicle equipment 3.

[0012] The vehicle speed sensor 2 detects the rotational speed of a rotating shaft AX that rotates as the wheels T of the vehicle rotate. The vehicle speed sensor 2 has Hall elements installed at 90° intervals, and outputs a rectangular wave of 4 cycles per rotation of the rotating shaft AX. The vehicle speed sensor 2 is connected to the meter device 1 and outputs a vehicle speed pulse signal of 4 cycles per rotation of the rotating shaft AX of the vehicle to the meter device 1.

[0013] The vehicle equipment 3 is, for example, a tachograph or the like. The vehicle equipment 3 is connected to the meter device 1 and inputs a vehicle speed pulse signal of 8 cycles per rotation of the rotating shaft AX that has been converted by the meter device 1.

[0014] The meter device 1 includes a display unit 10 and a signal conversion unit 11.

[0015] The display unit 10 displays information regarding the vehicle. The display unit 10 is configured by, for example, a liquid crystal display device or the like, and displays a speedometer, a tachometer, a fuel gauge, various cautions, etc. on the liquid crystal screen.

[0016] The signal conversion unit 11 receives, for example, a vehicle speed pulse signal with a period of four cycles per rotation of the rotation axis AX1 that rotates as the wheels T rotate from the vehicle speed sensor 2 as an input signal IN, converts it into a vehicle speed pulse signal with a period of eight cycles per rotation of the rotation axis AX1, and outputs it as an output signal OUT. The signal conversion unit 11 is composed of an electronic circuit mainly including a well-known microcomputer including, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and an interface. The functions of the signal conversion unit 11 described above are realized by loading an application program held in the ROM into the RAM and executing it with the CPU, operating various devices in the vehicle under the control of the CPU, and reading and writing data in the RAM and ROM.

[0017] Functionally, the signal conversion unit 11 includes a calculation unit 12 and an output unit 13.

[0018] The calculation unit 12 calculates the output period of the output signal OUT based on the input signal IN input from the vehicle speed sensor 2. Specifically, the calculation unit 12 calculates the pulse width for a half cycle detected from a rectangular wave corresponding to a half cycle in the input signal IN as the pulse width for one cycle in the output signal OUT.

[0019] Here, when the input signal IN is a vehicle speed pulse signal with 4 cycles per rotation of the rotation axis AX1, for example, the pulse widths of the rectangular waves (square waves) corresponding to half a cycle in the input signal IN for 4 cycles are pulse widths A, B, C, D, E, F, G, H as shown in FIG. 2. On the other hand, when the output signal OUT is a vehicle speed pulse signal with 8 cycles per rotation of the rotation axis AX1, the pulse widths of the rectangular waves corresponding to half a cycle in the output signal OUT for 8 cycles are A / 2, B / 2, C / 2, D / 2, E / 2, F / 2, G / 2, H / 2 as shown in FIG. 2. In the illustrated example, each rectangular wave having the pulse widths A, C, E, G in the input signal IN is a rectangular wave for half a cycle from the rising edge when switching from Lo to Hi to the falling edge. Each rectangular wave having the pulse widths B, D, F, H in the input signal IN is a rectangular wave for half a cycle from the falling edge when switching from Hi to Lo to the rising edge. The pulse widths A to H of each rectangular wave in the input signal IN become smaller (narrower) as the vehicle speed increases and larger (wider) as the vehicle speed decreases. The pulse widths A / 2, B / 2, C / 2, D / 2, E / 2, F / 2, G / 2, H / 2 of each rectangular wave in the output signal OUT become smaller (narrower) as the vehicle speed increases and larger (wider) as the vehicle speed decreases.

[0020] The calculation unit 12 calculates the pulse width A of the front half rectangular wave corresponding to the front half period (front half of the half period) of the first period in the input signal IN as the pulse width A for one period of the first period in the output signal OUT. In this case, the pulse width for half of the first period in the output signal OUT is A / 2. Also, the calculation unit 12 calculates the pulse width B of the rear half rectangular wave corresponding to the rear half period (rear half of the half period) of the first period in the input signal IN as the pulse width B for one period of the second period in the output signal OUT. In this case, the pulse width for half of the second period in the output signal OUT is B / 2. Further, the calculation unit 12 calculates the pulse width C of the front half rectangular wave corresponding to the front half period of the second period in the input signal IN as the pulse width C for one period of the third period in the output signal OUT. In this case, the pulse width for half of the third period in the output signal OUT is C / 2. Additionally, the calculation unit 12 calculates the pulse width D of the rear half rectangular wave corresponding to the rear half period of the second period in the input signal IN as the pulse width D for one period of the fourth period in the output signal OUT. In this case, the pulse width for half of the fourth period in the output signal OUT is D / 2.

[0021] Further, the calculation unit 12 calculates the pulse width E of the front half rectangular wave corresponding to the front half cycle of the third cycle in the input signal IN as the pulse width E for one cycle of the fifth cycle in the output signal OUT. In this case, the pulse width for a half cycle of the fifth cycle in the output signal OUT is E / 2. Also, the calculation unit 12 calculates the pulse width F of the rear half rectangular wave corresponding to the rear half cycle of the third cycle in the input signal IN as the pulse width F for one cycle of the sixth cycle in the output signal OUT. In this case, the pulse width for a half cycle of the sixth cycle in the output signal OUT is F / 2. Also, the calculation unit 12 calculates the pulse width G of the front half rectangular wave corresponding to the front half cycle of the fourth cycle in the input signal IN as the pulse width G for one cycle of the seventh cycle in the output signal OUT. In this case, the pulse width for a half cycle of the seventh cycle in the output signal OUT is G / 2. Also, the calculation unit 12 calculates the pulse width H of the rear half rectangular wave corresponding to the rear half cycle of the fourth cycle in the input signal IN as the pulse width H for one cycle of the eighth cycle in the output signal OUT. In this case, the pulse width for a half cycle of the eighth cycle in the output signal OUT is H / 2.

[0022] In particular, when the input of the input signal IN is started from the vehicle speed sensor 2, the calculation unit 12 of the present embodiment calculates the pulse width A of the front half rectangular wave corresponding to the front half cycle of the first cycle in the input signal IN as the pulse width A for one cycle of the first cycle in the output signal OUT at the time when the front half rectangular wave is input. Then, after outputting the rectangular wave of the first cycle in the output signal OUT, the calculation unit 12 calculates the pulse width B of the rear half rectangular wave corresponding to the rear half cycle of the first cycle in the input signal IN as the pulse width B for one cycle of the second cycle in the output signal OUT.

[0023] The output unit 13 sequentially outputs, as the output signal OUT, eight cycles of rectangular waves from the first cycle to the eighth cycle of the output signal OUT calculated by the calculation unit 12. In particular, the output unit 13 of this embodiment outputs a rectangular wave of the first cycle of the calculated output signal OUT at the time when the input of the latter half rectangular wave having a pulse width B corresponding to the latter half of the first cycle of the input signal IN is completed. The time when the input of the latter half rectangular wave having a pulse width B corresponding to the latter half of the first cycle of the input signal IN is completed is, in other words, the timing when the rising edge of the first half cycle of the second cycle of the output signal OUT is detected. That is, as shown in FIG. 2, the signal conversion unit 11 starts outputting the output signal by the output unit 13 with a delay of one cycle of the first cycle of the input signal IN. In this case, the output unit 13 does not output the output signal OUT at the time when the input of the first half rectangular wave having a pulse width A corresponding to the first half of the first cycle of the input signal IN is completed.

[0024] Furthermore, the output unit 13 outputs a rectangular wave of the second cycle in the output signal OUT calculated by the calculation unit 12 at the time when the input of the first half rectangular wave corresponding to the first half of the second cycle in the input signal IN is completed. The time when the input of the first half rectangular wave corresponding to the first half of the second cycle in the input signal IN is completed is, in other words, the timing when the falling edge of the first half of the second cycle in the output signal OUT is detected. In this way, after the input of the second half rectangular wave having the pulse width B corresponding to the second half of the first cycle in the input signal IN is completed, the output unit 13 outputs an output signal with a pulse width of one cycle corresponding to each rectangular wave whose pulse widths change from C to H at the time when the input of each rectangular wave whose pulse widths change from C to H in the input signal IN is completed.

[0025] Next, an example of the operation of the signal conversion unit 11 in the meter device 1 of this embodiment will be described with reference to the flowchart of Fig. 3. Steps S1-S8 shown in the figure correspond to the signal conversion process executed by the signal conversion unit 11.

[0026] First, in step S1, after the input of the input signal IN starts, the calculation unit 12 determines whether the input of the first half cycle of the first period is completed by the signal conversion unit 11. For example, the calculation unit 12 determines whether the input of the first half cycle of the first period is completed by detecting the fall and fall of the first period of the input signal IN. When the input of the first half cycle of the first period is completed, the signal conversion unit 11 proceeds to step S2. On the other hand, when the input of the first half cycle of the first period is not completed, step S1 is repeated.

[0027] In step S2, the signal conversion unit 11 calculates the first period of the corresponding output signal based on the rectangular wave corresponding to the first half cycle of the first period by the calculation unit 12 and proceeds to step S3. Specifically, in step S2, when the first half rectangular wave corresponding to the first half cycle of the first period in the input signal IN is input immediately after the input of the input signal IN starts, the calculation unit 12 calculates the pulse width A of the first half rectangular wave as the pulse width for one period of the first period in the output signal OUT. Steps S1 - S2 are an example of the calculation process.

[0028] Next, in step S3, the signal conversion unit 11 determines whether the input of the second half cycle of the first period is completed by the calculation unit 12. For example, the calculation unit 12 determines whether the input of the second half cycle of the first period is completed by detecting the rise of the second period of the input signal IN. When the input of the second half cycle of the first period is completed, the signal conversion unit 11 proceeds to step S4. On the other hand, when the input of the second half cycle of the first period is not completed, step S3 is repeated.

[0029] Next, in step S4, when the input of the second half rectangular wave corresponding to the second half cycle of the first period in the input signal IN is completed by the output unit 13, the signal conversion unit 11 outputs the rectangular wave of the first period in the calculated output signal OUT as the output signal and proceeds to step S5. Steps S3 - S4 are an example of the output process.

[0030] Next, in step S5, the signal conversion unit 11 calculates, by the calculation unit 12, the second period of the corresponding output signal based on the rectangular wave corresponding to the latter half period of the first period, and proceeds to step S6. Specifically, in step S5, after the calculation unit 12 outputs the rectangular wave of the first period in the output signal OUT, the pulse width B of the latter half rectangular wave corresponding to the latter half period of the first period in the input signal IN is calculated as the pulse width for one period of the second period in the output signal OUT.

[0031] Next, in step S6, the signal conversion unit 11 determines, by the calculation unit 12, whether the input of the first half period of the second period is completed. The calculation unit 12 determines whether the input of the first half period of the second period is completed, for example, by detecting the falling edge of the second period of the input signal IN. If the input of the first half period of the second period is completed, the signal conversion unit 11 proceeds to step S7, while if the input of the first half period of the second period is not completed, step S6 is repeated.

[0032] Next, in step S7, when the input of the first half rectangular wave corresponding to the first half period of the second period in the input signal IN is completed by the output unit 13, the signal conversion unit 11 outputs the rectangular wave of the second period in the calculated output signal OUT as the output signal, and proceeds to step S8.

[0033] In step S8, the signal conversion unit 11 calculates an output signal according to the input signal after the second half cycle of the second period by the calculation unit 12, and the output unit 13 sequentially outputs the calculated output signal after the third period, and repeats the process until the vehicle stops. In this way, for the second period and later in the output signal OUT, when the first half rectangular wave corresponding to the first half cycle of the second period and later in the input signal IN is input, the signal conversion unit 11 calculates the pulse width of the first half rectangular wave as the pulse width for one cycle of the first, third, fifth, and seventh odd cycles in the output signal OUT. Also, when the second half rectangular wave corresponding to the second half cycle of the second period and later in the input signal IN is input, the signal conversion unit 11 calculates the pulse width of the second half rectangular wave as the pulse width for one cycle of the second, fourth, sixth, and eighth even cycles in the output signal OUT. Then, the signal conversion unit 11 sequentially outputs the rectangular wave after the second period in the calculated output signal OUT as the output signal OUT.

[0034] As described above, the meter device 1 according to the present embodiment inputs, as an input signal IN, a vehicle speed pulse signal with four cycles per rotation of the rotating shaft AX1 that rotates as the wheels T rotate from the vehicle speed sensor 2, and includes a signal conversion unit 11 that converts it into a vehicle speed pulse signal with eight cycles per rotation of the rotating shaft AX1 and outputs it as an output signal OUT. Immediately after the input of the input signal IN is started, when the first half rectangular wave corresponding to the first half cycle of the first period in the input signal IN is input, the signal conversion unit 11 calculates the pulse width A of the first half rectangular wave as the pulse width for one cycle of the first period in the output signal OUT, and outputs the rectangular wave of the first period in the calculated output signal OUT when the input of the second half rectangular wave corresponding to the second half cycle of the first period in the input signal IN is completed.

[0035] With the above configuration, the meter device 1 according to this embodiment, unlike conventional meter devices, can output the output signal OUT at the timing when one period of the first cycle is input immediately after the input of the input signal IN starts, whereas in conventional meter devices, the output signal OUT was output at the timing when the input signal IN was input for four periods as shown in FIG. 2. As a result, the meter device 1 can shorten the time from when the input signal is input from the vehicle speed sensor 2 to when the output signal is output, thereby increasing the response speed.

[0036] Further, the meter device 1 calculates the output signal OUT corresponding to the first half cycle of the first cycle in the input signal IN, and then outputs the output signal for one cycle of the first cycle in the output signal OUT with a half cycle delay. As a result, the meter device 1 can output the output signal OUT with a half cycle delay even when the vehicle speed pulse signal fluctuates (for example, the duty ratio fluctuates).

[0037] The vehicle speed detection method applied to the meter device 1 according to this embodiment includes a signal conversion step executed by the signal conversion unit 11. Steps S1 - S8 of the signal conversion step include steps S1 - S2 as a calculation step of calculating the pulse width A of the first half rectangular wave corresponding to the first half cycle of the first cycle in the input signal as the pulse width for one cycle of the first cycle in the output signal at the time when the first half rectangular wave corresponding to the first half cycle of the first cycle in the input signal is input immediately after the input of the input signal starts. The signal conversion step also includes steps S3 - S4 as an output step of sequentially outputting the rectangular wave of the first cycle in the output signal calculated in the calculation step at the time when the input of the second half rectangular wave corresponding to the second half cycle of the first cycle in the input signal is completed. Thereby, the vehicle speed detection method according to this embodiment can obtain the same effects as the meter device 1 described above.

[0038] In the above embodiment, the case where the present invention is applied to the meter device 1 has been described, but the present invention is not limited to this, and it may be applied to a vehicle speed detection device.

[0039] Also, in the above-described embodiment, the vehicle speed sensor 2 has been described as being of a 4-pulse specification per cycle, which is generally used for vehicles. However, the present invention is not limited thereto, and it may be of an 8-pulse specification per cycle. In this case, the signal conversion unit 11 inputs a vehicle speed pulse signal of 8 cycles per rotation of the rotation shaft AX1 as an input signal IN, converts it into a vehicle speed pulse signal of 8 cycles per rotation of the rotation shaft AX1, and outputs it as an output signal OUT. Such a signal conversion unit 11 switches the output signal from Lo→Hi or Hi→Lo with respect to the rising and falling edges of the input signal IN.

[0040] Also, in the above-described embodiment, the signal conversion unit 11 inputs a vehicle speed pulse signal of 4 cycles per rotation of the rotation shaft AX1 as an input signal IN, converts it into a vehicle speed pulse signal of 8 cycles per rotation of the rotation shaft AX1, and outputs it as an output signal OUT. However, the present invention is not limited thereto. For example, the signal conversion unit 11 may be configured to input a vehicle speed pulse signal of N (N = natural number) cycles per rotation of the rotation shaft AX1 as an input signal IN, convert it into a vehicle speed pulse signal of 2N cycles per rotation of the rotation shaft AX1, and output it as an output signal OUT.

[0041] Also, in the above-described embodiment, the rectangular waves having the pulse widths A, C, E, and G are all rectangular waves from the rising edge that switches from Lo to Hi to the falling edge. However, the present invention is not limited thereto, and they may all be rectangular waves from the falling edge that switches from Hi to Lo to the rising edge.

Explanation of Reference Numerals

[0042] 1 Meter device 2 Vehicle speed sensor 3 Vehicle equipment 10 Display unit 11 Signal conversion unit 12 Calculation unit 13 Output unit AX Rotation shaft

Claims

1. A signal conversion unit that takes, as an input signal, a vehicle speed pulse signal having N (N = natural number) cycles per rotation of a rotating shaft that rotates with the rotation of a wheel from a vehicle speed sensor, converts it into a vehicle speed pulse signal having 2N cycles per rotation of the rotating shaft, and outputs it as an output signal, wherein the signal conversion unit, immediately after the input of the input signal is started, when the first half rectangular wave corresponding to the first half cycle of the first cycle in the input signal is input, calculates the pulse width of the first half rectangular wave as the pulse width for one cycle of the first cycle in the output signal, and outputs the rectangular wave of the first cycle in the calculated output signal when the input of the second half rectangular wave corresponding to the second half cycle of the first cycle in the input signal is completed. A vehicle speed detection device characterized by the above.

2. The signal conversion unit, after outputting the rectangular wave of the first cycle in the output signal, calculates the pulse width of the second half rectangular wave corresponding to the second half cycle of the first cycle in the input signal as the pulse width for one cycle of the second cycle in the output signal, outputs the rectangular wave of the second cycle in the calculated output signal when the input of the first half rectangular wave corresponding to the first half cycle of the second cycle in the input signal is completed, and for the output signal after the second cycle, when the first half rectangular wave corresponding to the first half cycle after the second cycle in the input signal is input, calculates the pulse width of the first half rectangular wave as the pulse width for one cycle of an odd cycle in the output signal, when the second half rectangular wave corresponding to the second half cycle after the second cycle in the input signal is input, calculates the pulse width of the second half rectangular wave as the pulse width for one cycle of an even cycle in the output signal, and sequentially outputs the rectangular waves after the second cycle in the calculated output signal as the output signal. The vehicle speed detection device according to Claim 1.

3. The signal conversion unit, takes, as an input signal, a vehicle speed pulse signal having 4 cycles per rotation of the rotating shaft, converts it into a vehicle speed pulse signal having 8 cycles per rotation of the rotating shaft, and outputs it as an output signal, calculates the pulse width of the second half rectangular wave corresponding to the second half cycle of the first cycle in the input signal as the pulse width for one cycle of the second cycle in the output signal, calculates the pulse width of the first half rectangular wave corresponding to the first half cycle of the second cycle in the input signal as the pulse width for one cycle of the third cycle in the output signal, Calculate the pulse width of the trailing rectangular wave corresponding to the second half cycle of the second cycle in the input signal as the pulse width for one cycle of the fourth cycle in the output signal. Calculate the pulse width of the leading rectangular wave corresponding to the first half cycle of the third cycle in the input signal as the pulse width for one cycle of the fifth cycle in the output signal. Calculate the pulse width of the trailing rectangular wave corresponding to the second half cycle of the third cycle in the input signal as the pulse width for one cycle of the sixth cycle in the output signal. Calculate the pulse width of the leading rectangular wave corresponding to the first half cycle of the fourth cycle in the input signal as the pulse width for one cycle of the seventh cycle in the output signal. Calculate the pulse width of the trailing rectangular wave corresponding to the second half cycle of the fourth cycle in the input signal as the pulse width for one cycle of the eighth cycle in the output signal. Sequentially output the rectangular waves for eight cycles of the first to the eighth cycles calculated as the output signal. The vehicle speed detection device according to claim 1 or 2.

4. Comprises a signal conversion step executed by a signal conversion unit that inputs a vehicle speed pulse signal having N (N = natural number) cycles per rotation of a rotating shaft that rotates as the wheels rotate from a vehicle speed sensor as an input signal, and converts it into a vehicle speed pulse signal having 2N cycles per rotation of the rotating shaft and outputs it as an output signal. The signal conversion step is as follows: A calculation step of calculating the pulse width of the leading rectangular wave corresponding to the first half cycle of the first cycle in the input signal as the pulse width for one cycle of the first cycle in the output signal when the leading rectangular wave corresponding to the first half cycle of the first cycle in the input signal is input immediately after the input of the input signal starts. An output step of sequentially outputting the rectangular wave of the first cycle in the output signal calculated in the calculation step when the input of the trailing rectangular wave corresponding to the second half cycle of the first cycle in the input signal is completed. A vehicle speed detection method characterized by the above.

5. A display unit for displaying information related to the vehicle. Comprises a signal conversion unit that inputs a vehicle speed pulse signal having N (N = natural number) cycles per rotation of a rotating shaft that rotates as the wheels rotate from a vehicle speed sensor as an input signal, and converts it into a vehicle speed pulse signal having 2N cycles per rotation of the rotating shaft and outputs it as an output signal. The signal conversion unit is as follows: When the leading rectangular wave corresponding to the first half cycle of the first cycle in the input signal is input immediately after the input of the input signal starts, calculate the pulse width of the leading rectangular wave as the pulse width for one cycle of the first cycle in the output signal. When the input of the latter half of the rectangular wave corresponding to the latter half of the first period in the input signal is completed, the calculated rectangular wave of the first period in the output signal is output. A meter device comprising:

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