JPS60256063A - Speed detector for car - Google Patents

Abstract

PURPOSE:To obtain an accurate car speed signal by eliminating the effect of the chattering of a contact, by providing two reed switches to provide phase difference between contact operations thereof and applying wave form shaping to the contact signal of each reed switch by an electronic circuit. CONSTITUTION:When a rotor 1 is rotated to the direction shown by the arrow, a magnet 2 forms a magnetic field around a reed switch 3 and a contact 4 is opened and closed. At this time, when the lead switch 3 receives the vibration of a car, a chattering signal is generated at the contact 4. With respect to a reed switch 5, a chattering signal is generated at a contact 6 as shown by the signal (b) in the drawing in the same way as mentioned above. These both signals A, B are inputted to an electronic circuit and triggering is applied at the rising of the signal B and, thereafter, the deformation of output is prevented, before the signal A falls, to obtain the output of a signal C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a vehicle speed detector for detecting the vehicle speed of an automobile.

[Prior art]

Conventionally, there has been a vehicle speed detector of this type as shown in FIG. In the figure, 1 is a rotating body, 2 is a magnet placed around the rotating body 1 at 90 degree intervals, 3 is a reed switch placed near the rotating body 1, and 4 is a contact point of the reed switch 3. .

Next, the operation will be explained. The rotational speed of the rotating body 1 changes depending on the vehicle speed of the automobile, and the magnet 2 also rotates together with the rotating body 1. This magnet 2 generates four magnetic fields in the reed switch 3 in one rotation of the rotating body 1. This magnetic field opens and closes the contacts 4 of the reed switch 3. The opening/closing signal of the reed switch 3 becomes a signal corresponding to the vehicle speed, so that the vehicle speed can be detected.

Since the conventional vehicle speed detector is configured as described above,
The reed switch 3 is shaken by the vibration of the car, and the distance between it and the rotating body 1 changes, and as a result, the strength of the magnetic field acting on the reed switch 3 also changes, causing the contact 4 to chatter at the moment the switch opens and closes. This has the disadvantage that an incorrect signal indicating an abnormal increase in vehicle speed is issued, making it impossible to obtain an accurate vehicle speed signal.

[Summary of the invention]

This invention was made with the aim of improving this drawback, and it is possible to create a system by providing two reed switches, creating a phase difference in their contact operations, and shaping the waveform of the contact signal of each reed switch using an electronic circuit. An object of the present invention is to provide a vehicle speed detector for an automobile that can eliminate the influence of chattering of switch contacts and obtain an accurate vehicle speed signal.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In Fig. 2, 1 is a rotating body that rotates according to the vehicle speed;
are magnets arranged around the rotary body 1 at intervals of 90 degrees. 3 is a reed switch similar to that shown in FIG. 1 arranged near the outer periphery of the rotating body 1, and 4 is a contact point thereof.

5 is another reed switch placed near the outer periphery of the rotating body I, and 6 is its contact point. This reed switch 5
is located between the reed switch 3 and the magnet 2° at a predetermined angle.

Next, the operation of the present invention will be explained with reference to the signal waveform diagram in FIG. When the rotating weight rotates in the direction of the arrow, the magnet 2 creates a magnetic field around the reed switch 3, and the contacts 4 open and close. At this time, when the reed switch 3 is subjected to vibrations from the automobile, a chattering signal is generated at the contact 4 as shown at A in FIG. On the other hand, the reed switch 5 also has the third
As shown in B in the figure, a chattering signal is generated at the contact 6. Both signals A and B are input to an electronic circuit (for example, Surin: 1 Fang) 7, and a trigger is applied when the B signal rises.After that, the output is not deformed until the human signal falls. A signal (waveform) output can be obtained. In this way, the vehicle speed signal can be extracted as a chattering-free signal, so that an accurate vehicle speed signal can be obtained.

In the above embodiment, the vehicle speed detector was used as an automobile speed detector.
By arranging two reed switches, when the rotating body 1 reverses, the operating order of the contact signals of both reed switches 3.5 is reversed. For example, if the rotating body 1 rotates in the opposite direction to the arrow direction in FIG. 2, the order of the contact signals will be reversed from that in FIG. 3. This allows it to function as a detector that can also detect when a vehicle is moving backwards.

〔Effect of the invention〕

As explained above, according to the present invention, chuckling of the switch contacts is prevented by providing two reed switches, creating a phase difference in their contact operations, and shaping the waveform of the contact signal of each reed switch using an electronic circuit. This eliminates the influence and provides accurate vehicle speed signals, resulting in a highly reliable vehicle speed detector for automobiles.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional vehicle speed detector, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a signal waveform diagram for explaining the operation. 1... Rotating body, 2... Magnet, 3.5... Reed switch, 4, 6... Contact. In addition, in the figures, the same reference numerals indicate the same or similar parts O. Agent: Masuo Oiwa Figure 1 Figure 2 Procedural amendment (voluntary) Mr. Commissioner of the Japan Patent Office l, Indication of case Patent application 113465/1982 No. 3, To Hitoshi Katayama, representative of the person making the amendment, Section 5, Detailed explanation of the invention in the specification to be amended, column 6, contents of the amendment, page 4, lines 5-6, 1 modification” as “change”. correct.

Claims (1)

[Claims] In a vehicle speed detector that detects the vehicle speed of a car using a reed switch in the speedometer, two of the reed switches are provided, a phase difference is created between the contact operations, and the waveform of the contact signal of each reed switch is shaped by an electronic circuit. A vehicle speed detector for an automobile, characterized in that it is configured as follows.