JPH04198756A - Vehicle speed detecting device - Google Patents

Abstract

PURPOSE:To obtain a device applicable to various vehicle types with a simple operation by providing a frequency division ratio setter changing the set frequency division ratio to multiple values for a frequency dividing means of the pulse signal outputted from a pulse signal generating means. CONSTITUTION:A pulse signal generating means 3 outputs the first set number of pulse signals S for one rotation of the output shaft 17 of a transmission. The pulse signal S is compared with the preset reference voltage with a comparing circuit 5, if the pulse signal S is the reference voltage or above, the comparing circuit 5 outputs a pulse signal Sp. The pulse signal Sp is inputted to a frequency dividing circuit 7, and the frequency is divided at the set frequency division ratio 1/n. The set frequency division ratio 1/n is the value set by a frequency division ratio setter 9 in advance so that four pulses are generated in one rotation of an axle. The number of pulse signals in one rotation of the axle can be reduced to four and inputted to a vehicle speed calculating circuit 11 by only changing the dip switch of the frequency division ratio setter 9 even when the gear ratio and wheel diameter of a drive system have different specifications.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a vehicle speed detection device that detects vehicle speed based on the rotational speed of an output shaft of a vehicle transmission.

[Conventional technology]

Conventionally, as this type of vehicle speed sensor, one shown in FIG. 3 is known. That is, in the figure, a drive gear 105 is fixed to an output shaft 103 of a vehicle transmission 101, and a driven gear 109 of a vehicle speed sensor 107 is meshed with this drive gear 105. In the vehicle speed sensor 107, a shaft 111 is integrally fixed to a driven gear 109, and a permanent magnet 1 having a large number of magnetic poles is attached to the tip of the shaft 111.
13, and a detecting section 115 made of a magnetoresistive element or the like is installed facing the permanent magnet 113 at a predetermined gap, and the detecting section 115 converts changes in magnetic flux density into electrical signals. do. This signal is input to electronic control unit 117. In the electronic control unit 117,
After converting this signal waveform into a pulse signal and further frequency-dividing it by four, the vehicle speed is determined by counting the number of pulses within a predetermined time using a frequency counter or the like.

[Problem to be solved by the invention]

By the way, in such a vehicle speed sensor 107, the number of pulses output from the vehicle speed sensor 107 differs even at the same vehicle speed due to differences in vehicle types such as drive system gear ratios and wheel diameters, so various design specifications are required. must be taken into account. In order to simplify such complicated specifications, there are cases where a standard is established in which the number of pulses output from the vehicle speed sensor 107 per one revolution of the axle is set to a predetermined number (for example, 4 pulses). However, in the past, in order to meet the above specifications,
This was done by changing the gear ratio between the driving gear 105 and the driven gear 109. However, such changes in gears require new molds or mechanical design changes, resulting in increased costs. The present invention aims to solve the above-mentioned problems of the conventional technology.It is an object of the present invention to provide a highly versatile vehicle speed detection system that does not require mechanical design changes such as changing gears, is compatible with various vehicle types, The purpose is to provide equipment.

[Means to solve the problem]

The present invention, which was made to solve the above problems, provides a vehicle speed detection device that detects vehicle speed based on the rotational speed of an output shaft of a vehicle transmission. a pulse signal generating means for generating a signal; a frequency dividing means for frequency dividing the pulse signal output from the pulse signal generating means to a second set number of pulse signals at a set frequency division ratio; speed calculation means for calculating a vehicle speed based on the output pulse signal, and further provided with a frequency division ratio setting device for the frequency division means that can change the set frequency division ratio to a plurality of values. It is characterized by:

[Effect]

In the present invention, a pulse signal generating means is provided on the output shaft of the vehicle transmission. The pulse signal generating means outputs a first set number of pulse signals for one rotation of the output shaft. This pulse signal is input to the frequency dividing means, where the frequency is divided by a set frequency dividing ratio to a second set number, and the pulse signal is input to the speed calculating means. The speed calculating means calculates the vehicle speed based on the pulse signal from the frequency dividing means. Further, in the present invention, the frequency division ratio set in the frequency dividing means can be changed by the frequency division ratio setter. Therefore, by setting the set frequency division ratio to a desired value, the pulse signal from the pulse signal generating means can be adjusted to the second set number, regardless of the specifications of the gear ratio of the drive system. ,
Therefore, there is no need to change the specifications of gears, etc. as in the past.

【Example】

An embodiment of the present invention will be described below. FIG. 1 is a schematic configuration diagram showing a vehicle speed detection device attached to an output shaft of a transmission. In FIG. 1, a vehicle speed detecting device 1 includes a rotational speed signal generating means 3, a comparison circuit 5, a frequency dividing circuit 7, a frequency dividing ratio setting device 9, a vehicle speed calculating circuit 11, and a display 12. The rotational speed signal generating means 3 includes a rotating plate 13 and a detecting section 1.
5. The rotating plate 13 is the output shaft 17 of the transmission.
95 permanent magnet pieces 21 are embedded in the outer periphery of the date plate I9 at equal intervals (2 mm pitch) in the circumferential direction so that adjacent magnetic poles are different. It is formed by That is, the rotating plate 13 is
Permanent magnet pieces 21 are arranged in a circular shape in a mold and embedded by insert molding with resin. The detection unit 15 is installed at a predetermined distance in the radial direction of the rotary plate 13, and is composed of a magnetoresistive element that changes its resistance value in accordance with changes in magnetic flux density. The comparison circuit 5 inputs the waveform signal S from the detection section I5,
When the signal is higher than the reference voltage, the pulse signal Sp
This outputs the following. The frequency dividing circuit 7 inputs the pulse signal from the comparison circuit 5,
The device frequency division ratio setter 9, which is composed of a well-known circuit that divides the pulse signal at a set frequency division ratio of 1/n, sets the set frequency division ratio l/n of the frequency dividing circuit 7. , a program counter that can freely change the set frequency division ratio 1/n by manually operating a dip switch. In other words, the set frequency division ratio set by the frequency division ratio setter 9 is 1/
The n signal is input to the frequency divider circuit 7, and the pulse signal sp from the comparator circuit 5 is divided by this set frequency division ratio of 1/n. In this embodiment, the frequency division ratio setter 9 uses 1/128
It is possible to change the set frequency division ratio up to. Next, the operation of the above configuration will be explained in conjunction with the timing chart of FIG. 2. When the output shaft 17 of the transmission rotates due to the engine driving force, the rotating plate 13 fixed to the output shaft 17 rotates. This rotation of the rotating plate 13 changes the magnetic field. Then, the detection unit 15 receives the change in magnetic flux density and outputs a waveform signal S (FIG. 2(A)). This waveform signal S is input to the comparator circuit 5. The comparator circuit 5 compares the voltage with a predetermined reference voltage V ref and outputs a pulse signal Sp if the voltage is equal to or higher than the reference voltage V ref (FIG. 2(B)). This pulse signal Sp is transmitted to the frequency dividing circuit 7
and is divided by the set frequency division ratio 1/n (second
Figure (C)). Here, the set frequency division ratio 1/n is a value set in advance by the frequency division ratio setter 9 so that the number of pulses is four per rotation of the axle. The pulse signal frequency-divided by the frequency dividing circuit 7 is input to the vehicle speed calculation circuit 11. The vehicle speed calculation circuit 11 counts the number of pulses within a predetermined time and determines the vehicle speed based on this count value. This output is sent to the display 12 to display the vehicle speed. In the above embodiment, the setting frequency division ratio 1/n of the frequency division circuit 7 can be changed by changing the setting of the dip switch of the frequency division ratio setting device 9. The number of pulses for each pulse is set to 4 pulses. Therefore, even if the drive system has different gear ratios, wheel diameters, etc., the number of pulse signals per one revolution of the axle can be reduced to four pulses, and the vehicle speed calculation circuit 11
can be adjusted to input. Therefore, in this embodiment, the number of pulses can be easily changed by simply changing the dip switch of the frequency division ratio setter 9.
There is no need to change the design of gears etc. as with conventional technology (
, because of its versatility, it is possible to reduce costs. Moreover, since the number of permanent magnet pieces 21 of the rotary plate 13 is set to a large value of 95 pieces, it is possible to change the set frequency division ratio to a large number, thus making it possible to correspond to dozens of car models.
Moreover, the accuracy can be suppressed to an error of about ±2%. Further, the rotational speed signal generating means 3 of the above embodiment includes the rotating plate 1
3 and a detection section 15, and is a non-contact type that does not transmit driving force using gears as in the conventional technology, so it also has the effect of being excellent in durability. In the above embodiment, the pulse signal generating means includes 95 permanent magnet pieces 2 on the rotary plate 13 directly fixed to the output shaft 17.
1, the rotation speed signal generating means 3 is configured to output 95 pulse signals in one rotation of the output shaft 17. However, the present invention is not limited to this. A configuration may be adopted in which 95 pulse signals are obtained by rotating a rotary plate to which 95 or less permanent magnet pieces are fixed. In this embodiment, a smaller rotary plate can be used than in the first embodiment, and the space required is narrower. Further, in the above embodiment, the permanent magnet piece 21 is embedded in the outer periphery of the disk 19, and the detection part 15 of the magnetic resistance element
However, instead of this, an inductilon type structure may be used in which the same number of protrusions as the permanent magnet pieces are formed on the outer periphery of a magnetic disc, and a detecting section consisting of a coil is installed. In the above embodiment, the number of permanent magnet pieces 21 of the rotary plate 13 was set to 95, but in consideration of versatility and accuracy,
You may change the value to around 100 as appropriate. Furthermore, in the above embodiment, the number of pulse signals input to the vehicle speed calculation means (second set number) was set to four in consideration of detection errors, etc., but it is a value that contributes to improving detection reliability. If so, the number is not limited. Further, the set frequency division ratio in the frequency division ratio setting means may be changed by rewriting the set value using a ROM instead of a dip switch.

【Effect of the invention】

As explained above, according to the present invention, the frequency division ratio set in the frequency dividing means can be changed by the frequency division ratio setter. Therefore, by setting the set frequency division ratio to a desired value, the number of pulses per rotation of the axle can be adjusted to a predetermined value, regardless of the specifications of the gear ratio of the drive system or the diameter of the wheels. Therefore, it is possible to provide a vehicle speed detection device that can adjust to a predetermined number of pulses without changing the mechanical specifications of gears, etc. (by simply setting the switch of the frequency division ratio setting device, etc.) .

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a vehicle speed detection device according to an embodiment of the present invention, and FIG. 2 is a configuration diagram showing a vehicle speed detection device according to the same embodiment.
FIG. 3 is a configuration diagram showing a conventional vehicle speed detection device. 1... Vehicle speed detection device 3... Rotation speed signal generating means (pulse signal generating means) 5
... Comparison circuit 7 ... Frequency division circuit (frequency division means) 9.
... Frequency division ratio setter 11 ... Vehicle speed calculation circuit (vehicle speed calculation means) 12 ... Display device 13 ... Rotating plate 15 ... Detection section 17
...Output shaft I9...Disk 21...Permanent magnet piece

Claims (1)

[Scope of Claims] A vehicle speed detection device that detects vehicle speed based on the rotational speed of an output shaft of a vehicle transmission, comprising: a pulse signal generator that generates a first set number of pulse signals for one revolution of the output shaft; means, and a pulse signal output from the pulse signal generating means,
A frequency dividing means for frequency dividing up to a second set number of pulse signals at a set frequency division ratio; and a speed calculation means for calculating a vehicle speed based on the pulse signals output from the frequency dividing means, further comprising: A vehicle speed detection device characterized in that the frequency dividing means is provided with a frequency division ratio setter capable of changing the set frequency division ratio to a plurality of values.