JPS6098369A - Data processing method of speedometer - Google Patents

Abstract

PURPOSE:To prevent degradation of the measuring capacity for a very low speed by counting up a counter each time when the state of a pulse signal is changed. CONSTITUTION:When an automobile is run, a magnet disc 1 is rotated, and the pulse signal is generated from a lead switch 2. This pulse signal is supplied directly to a monostable multivibrator 3a, and this signal has the phase inverted and is supplied to a monostable multivibrator 3b. Outputs of monostable multivibrators 3a and 3b are synthesized by an OR circuit 5 and are supplied to a counter 6. The number of pulses of the signal supplied to the counter 6 is twice as large as that of the signal generated from the lead switch 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a speedometer data processing method that improves the measurement accuracy of low speed sections.

[Prior art]

Generally, the speed of an automobile is expressed by converting the rotation of the axle into on/off pulses, and calculating the number of pulses generated in a predetermined period of time as n1. In this case, the number of pulses generated per rotation of the axle is determined by taking into account the distance resolution per pulse, the degree of difficulty in manufacturing the sensor, etc.

However, the speedometer 1 constructed in this manner has the drawback that although there is no problem during normal running, the number of pulses generated decreases during extremely low speeds, resulting in extremely poor measurement performance.

[Object and structure of the invention]

Therefore, it is an object of the present invention to provide a speedometer data processing method that does not deteriorate measurement performance even at extremely low speeds.

In order to achieve this object, the present invention is configured to increment the count every time a state change occurs in the pulse signal. Hereinafter, the present invention will be described in detail using drawings showing embodiments.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, reference numeral 1 denotes a magnetic disc that rotates in response to the rotation of the axle. Four magnets are provided on the circumference. 2 is a reed switch which generates an ON signal every time the magnet of the magnet disc 1 approaches. 3a and 3b are mono-multivibrators which, when supplied with an input signal, generate a pulse having a duration shorter than the input signal period determined by the maximum speed of the vehicle. 4 is an inverter, 5 is an OR circuit, and 6 is a counter.

The operation of the circuit configured in this way is as follows. When the automobile runs, the magnetic disk 1 rotates, and the reed switch 2 generates the signal shown in FIG. 2(a). At this time, the magnets of the magnet disk 1 are arranged so that the duty ratios of the waveforms shown in (a) are equal. When the signal shown in FIG. 2 (,) is generated, it is directly supplied to the mono multi-pipe rake 3a, and is supplied to the mono multi-vibrator 3b with its phase inverted. For this reason, the mono multivibrator 3 &
The signal shown in FIG. 2(b) is output, and the monomultipipe lake 3b outputs the signal shown in FIG. 2(c). These signals are combined by an OR circuit 5 and supplied to a counter 6 as a signal shown in FIG. 2(d). The signal shown in (d) is (
It has twice the number of pulses as the signals shown in b) and (e), and therefore data processing can be performed with high accuracy even when the number of pulses generated from the reed switch 2 at extremely low speeds is reduced.

The difference in performance between the conventional device and the device to which the present invention is applied is due to one rotation of the magnet disk 1! Let's examine a car that generates 74 pulses and has a tire circumference of 2 meters. When this car is running at a speed where the reed switch 2 generates one pulse per second, the speed S is as follows.

S == -X 3600 = '-8K''/hour Therefore, the conventional device does not have a speed resolution of 1.8 km/h or less.On the other hand, the device to which the present invention is applied has a resolution of 0.9 km/h, which is half this. In addition, normal speedometers perform sampling every 0.5 seconds to ensure accuracy, and calculate and display the vehicle speed based on the values of the past two samplings.For this reason, when the speed is less than Ikm/h, When trying to display a zero, the period of the pulse generated by the reed switch 2 when the speed is Ikm/h is 1.8 seconds, and the conventional device takes about 2 pulses to count this pulse, so it cannot display a zero during this time. In contrast, the device to which the present invention is applied can display zero after one second, and has good followability.

FIG. 3 is a block diagram showing another embodiment.
a, the number of rises is counted by a counter 7b, and an adder 8 adds up the number of rises.

In FIG. 4, the output of the reed switch 2 is counted by a microcomputer 9, and as shown in the flowchart shown in FIG. If it is determined to be 1-YESj, then as shown in step 101, it is determined whether the level of the internal register A of the microcombi caller 9 is at the level 10j, and if rNOJ, it is determined to be 1-YESj. Since there is no change in the level of the input encoding signal, other processing shown in step 102 is performed and the process returns to step 10[l].

While repeating this operation, the input signal changes to the "u level Kara FO" level, so step 100
It is determined that Then, as shown in step 103, it is determined whether the level of register A is "1" level or not, and r
If YESJ, the level of register A is inverted (from "1" to rOJ) in step 104, the count is incremented as shown in step 105, and the process returns to step 100 through the process of step 102.

If the state of the input level does not change at this time, step 100
Then, rNOJ is determined, but in step 103, “N
Since the determination is ``O'', the flow returns to step 100 again through the process of step 102.

As this operation is repeated, the input signal changes from "0" level to "
1" level, so step 100 is determined to be "rYES", and when step 101 is also determined to be rYES J, the level of register A is inverted ("0") in step 106.
"→rlJ) After that, the count is increased in step 105, the process in step 102 is performed, and the process returns to step 100. In this way, each time a state change occurs in the output signal of the reed switch 2, the count value is incremented.

FIG. 6 is a block diagram 1 showing another embodiment, in which terminals 9a and 9b of the microcomputer 9 are interrupt terminals,
The terminal 9a accepts an interrupt when the input signal changes from the l-0J level to the ``1'' level, and the terminal 9b accepts an interrupt when the input signal changes from the ``1'' level to the 10'' level. There's a carp.

When an interrupt is accepted, the microcomputer 9 increments the count of an internal counter. Such a device increments the count each time a state change occurs in the input message.

〔Effect of the invention〕

As explained above, the data processing method on the speed side according to the present invention is configured to increment by one every time a change in the state of the input signal occurs, so that accurate data processing can be performed even at extremely low speeds. It has the effect of

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of a device constructed by applying the present invention, FIG. 2 is a waveform diagram of each part of the device in FIG. 1, and FIGS. 3 and 4 show other embodiments. FIG. 5 is a flowchart 1 showing the operation of the apparatus in FIG. 4, and FIG. 6 is a block diagram showing another embodiment. 1...Magnet disc, 2...Leat switch, 3a
, 3b...mono multi-by-break, 4°°°° inverter, 5...mare circuit, 6-...counter. Patent applicant: Koito Seisakusho Co., Ltd. Agent: Masaki Yamakawa (and one other person)

Claims (1)

[Claims] In a speedometer data processing method that generates a pulse signal every time a predetermined distance is traveled and counts the number of pulses at a predetermined time interval, there is a method in which the count is incremented every time a state change occurs in the pulse signal. Characteristic speedometer data processing method.