JPH05322908A - Speed detecting apparatus - Google Patents

Abstract

PURPOSE:To detect the very low speed instantaneously with regard to a speed detecting apparatus for detecting the speed of an automobile. CONSTITUTION:In a speed detecting apparatus for detecting rotaion 11 of the rotary shaft of a vehicle and for detecting the speed of the vehicle, a plurality of waveform-signal generating means 12, which generate a plurality of waveform signals per one rotaion that are continuously changed based on the rotation of the rotary shaft 11, and a plurality of waveform detecting means 13 for detecting the waveform signals at every constant phase difference, are provided. A waveform changing-rate obtaining means 31 obtains the changing rate of each detected waveform signal and synthesizes the changing rates. A speed obtaining means 32 obtains the speed by using the changing rate of the waveform signal, which is obtained with the waveform-changing-rate obtaining means based on the relationship between the preset synthesized waveform changing rate and the speed, as the parameters. An erroneous-operation preventing means 308 inhibits the use of the speed, which is obtained with the speed obtaining means 32, when the vehicle speed exceeds the specified value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed detecting device for detecting the speed of an automobile, and particularly to the present invention to detect an extremely low speed instantaneously.

[0002]

2. Description of the Related Art Conventionally, as a technique in such a field, there is a vehicle speed detecting device disclosed in Japanese Utility Model Laid-Open No. 62-12873. In a conventional speed detecting device, a method in which a magnet ring magnetized in multiple poles in a rotor portion that rotates in synchronization with rotation of a propulsion shaft of a vehicle, for example, the same as rotation of a transmission driven gear, and a magnetic resistance element in a sensor portion Thus, the waveform obtained from the change in time with rotation is converted into a pulse, the pulse interval is measured, the pulse interval is counted, or the pulse signal is counted, and the speed is obtained from this count.

[0003]

However, the conventional speed detecting device has a problem that the interval of one pulse is long and it takes too much time to detect the speed when the speed is very low. Therefore, an object of the present invention is to provide a speed detecting device capable of instantaneously detecting an extremely low speed in view of the above problems.

[0004]

In order to solve the above problems, the present invention provides a speed detecting device for detecting the rotation of a rotating shaft of a vehicle to detect the speed of the vehicle, a plurality of waveform signal generating means, and a plurality of waveform signal generating means. The waveform signal detecting means, the waveform change rate deriving means, and the speed deriving means are provided. The plurality of waveform signal generating means continuously changes based on the rotation of the rotary shaft to generate a plurality of waveform signals per one rotation.

The plurality of waveform signal detecting means detect the waveform signals for each constant phase difference. The waveform change rate deriving means derives the change rate of each detected waveform signal and synthesizes the change rates. The velocity deriving unit obtains the velocity from the relationship between the synthetic waveform change rate and the velocity created in advance, using the rate of change of the waveform signal obtained by the waveform change rate deriving unit as a parameter.

Further, the plurality of waveform signal generating means are composed of magnet rings magnetized in multiple poles, and the plurality of waveform signal detecting means are composed of a plurality of magnetic field detecting means for detecting a change in magnetic field distribution caused by the magnet ring. Good.
Further, when the vehicle speed is equal to or higher than a predetermined value, a malfunction preventing means may be provided for stopping the use of the speed obtained by the speed deriving means.

[0007]

According to the speed detecting device of the present invention, the plurality of waveform signal generating means continuously change based on the rotation of the rotary shaft to generate a plurality of waveform signals per rotation. The waveform signals are detected by the plurality of waveform signal detection means for each constant phase difference. The change rate of each detected waveform signal is derived by the waveform change rate deriving means, and the change rates are combined. Therefore, even if one of the plurality of waveform signal detecting means detects a waveform where the inclination of the waveform of the waveform signal is small and the change rate is small, the other waveform signal detecting means can detect the waveform where the inclination of the waveform is large and the change rate is large. Therefore, a constant rate of change can be obtained within one period of the magnetic field waveform. The extremely low speed of the vehicle is obtained from the relationship between the synthetic waveform change rate and the speed created in advance by the speed deriving means, using the change rate of the waveform signal obtained by the waveform change rate deriving means as a parameter. Therefore, the extremely low speed of the vehicle can be instantly measured from the magnitude of the change rate of the waveform signal formed by one of the plurality of waveform signal detecting means.

The plurality of waveform signal generating means are magnet rings magnetized in multiple poles, and the plurality of waveform signal detecting means are easily constituted by a plurality of magnetic field detecting means for detecting a change in magnetic field distribution caused by the magnet ring. It When the vehicle speed is equal to or higher than a predetermined value, reliability is improved by providing a malfunction preventing means for stopping the use of the speed obtained by the speed deriving means.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of vehicle speed signal generating means according to an embodiment of the present invention. The speed detecting device of the present invention comprises a plurality of waveform generating means 12 and a plurality of waveform signal detecting means 13 shown in FIG. The plurality of waveform generating means 12 is, for example, a magnet ring 1 having a plurality of magnetic poles.
The magnet ring 121 is composed of a permanent magnet on a disc having magnetic poles formed at equal intervals at about 20 positions in the circumferential direction. It is provided integrally with the connected rotating shaft 11.

The plurality of waveform signal detecting means 13 are for detecting the signal waveforms generated by the plurality of waveform generating means 12, and a plurality of magnetic field detecting elements for detecting the magnetic field change of the magnet ring 121, for example, Hall elements. 131,
It is formed of 132 and is arranged in the vicinity of the rotating shaft 11. The arrangement position is as shown in this figure (b) which expanded the A part of this figure (a), but as an example, the two hall elements 131 and 132 are the said magnet ring 121.
Are arranged so that the phases of the magnetic field waveforms H1 and H2, which represent the change in the magnetic field distribution due to the rotation of the, as a change in voltage, differ by 90 °.

Next, the basic operation for obtaining the extremely low speed of the vehicle from the plurality of waveform generating means 12 and the plurality of waveform signal detecting means 13 will be described. The plurality of waveform generating means 12 generate a plurality of magnetic field waveforms when the rotating shaft 11 makes one rotation, and the plurality of waveform signal detecting means 13 detect each magnetic field waveform.
In one of the plurality of waveform signal detecting means 13, the measured magnetic field waveform has a periodic waveform, and if the vehicle speed is high, the period of the magnetic field waveform becomes short and the temporal change of the magnetic field waveform becomes large, so that the vehicle speed becomes high. If it is smaller, the period of the magnetic field waveform becomes longer and the temporal change of the magnetic field waveform becomes smaller. Therefore, if the relationship between the magnetic field change rate, which is a temporal change of the magnetic field waveform, and the vehicle speed is obtained in advance and the magnetic field change rate is derived from the detected magnetic field waveform, the extremely low speed of the vehicle can be instantly obtained. However, one waveform signal detection means has a large magnetic field change rate and a small magnetic field change rate in one cycle of the magnetic field waveform, and cannot detect an extremely low speed from the magnetic field change rate at a small magnetic field change rate. Therefore, a plurality of waveform signal detecting means 13 are provided so that when the magnetic field change rate detected by one waveform signal detecting means is small, the other waveform signal detecting means can detect a large magnetic field change rate.

The basic operation will be specifically described below.
For simplification of description, a case where two Hall elements 131 and 132 are used as the plurality of waveform signal detecting means 13 will be described. The two Hall elements are arranged so that magnetic field waveforms H1 and H2 having different phases by 90 ° are obtained. Thus, the magnetic field waveform change rate is obtained by sampling these magnetic field waveforms at regular intervals. These magnetic field waveforms are sine waves as shown in FIG. 2 (however, FIG. 2 shows the case where the magnet ring 121 rotates at a constant speed), and if z in the figure is considered to be 0 °, one of the waveforms is 0.
The magnetic field change rate increases near 90 °, 180 °, 360 ° (the numerical value represents the phase of one magnetic field waveform H1), but 90%
At around 270 °, the rate of magnetic field change becomes small. Since the other waveform is arranged so that its phase is different by 90 °,
When one magnetic field waveform change rate is small, the other magnetic field waveform change rate is large, and when one magnetic field waveform change rate is large, the other magnetic field waveform change rate is small. If detected, the waveform magnetic field change rate corresponding to the vehicle speed can be found to some extent instantaneously. Regarding the relationship between the vehicle speed and the rate of change in the magnetic field waveform, for example, when two Hall elements 131 and 132 are used as the above-mentioned magnetic field detection elements and a magnet ring 121 is magnetized with 20 poles, two Hall elements 131 are used. , 132 are arranged so that the phase difference of the detected waveforms detected by each Hall element is 90
If made different, the magnetic field waveform H1 detected from one Hall element is H1 = B · sin (2π · f · t) (1), and the other magnetic field waveform H2 is H2 = B · cos ( 2π · f · t) (2) Here, B represents the amplitude of the magnetic field waveform, and f represents the rotation frequency (Hz) of the magnet ring. Since the magnet ring is attached so that the rotation speed corresponding to the vehicle speed can be obtained, the rotation frequency of the magnet ring and the vehicle speed have a predetermined correspondence.

FIG. 3 is a diagram showing the relationship between the amount of change in the magnetic field waveform per unit time and the vehicle speed when two magnetic field detecting elements are used. Two magnetic field waveforms represented by the above equations (1) and (2), that is, a magnetic field waveform having a phase difference of 90 °, is Δt = 50 ms.
When sampling is performed, the magnetic field waveform change amount (v) per unit time having a constant width with respect to the vehicle speed (0 to about 6 Km / h) is obtained as the magnetic field waveform change rate as shown in FIG.

The above is the two magnetic field detecting elements 131 and 13
Although the magnetic field waveform change rate when 2 is used,
The magnetic field waveform change rate in the case where more magnetic field detection elements are provided will be described. FIG. 4 is a diagram showing the relationship between the amount of change in the magnetic field waveform per unit time and the vehicle speed when three magnetic field detecting elements are used. The three magnetic field detecting elements are arranged so that the respective magnetic field waveforms have a phase difference of 60 °. As shown in the figure, when the magnetic field waveform change rate is obtained in the same sampling time as the above, the magnetic field waveform change amount per unit time of a constant width with respect to the vehicle speed is obtained.
It is narrower than that shown in and the accuracy is improved.

FIG. 5 is a diagram showing the relationship between the amount of change in the magnetic field waveform per unit time and the vehicle speed when six magnetic field detecting elements are used. In the case of this figure, since six Hall elements are used, the phase difference between the detected waveforms is 30 °. As shown in this figure, the amount of change in the magnetic field waveform per unit time is further increased as compared with the case of FIG. It can be seen that the width of becomes smaller and the speed can be obtained with high accuracy.

Next, a means for deriving the velocity from the magnetic field waveform change rate detected by the magnetic field detecting elements 131 and 132 will be described. FIG. 6 is a diagram for explaining a configuration for deriving an extremely low speed according to the embodiment of the present invention, and FIG. 7 is a diagram showing signal waveforms of respective parts of the extremely low speed detecting means of FIG. As shown in the figure, the speed detecting device of the present invention comprises a vehicle speed pulse generating means 2 and an extremely low speed detecting means 3 for deriving an extremely low speed. The vehicle speed pulse generating means 2 is a magnetic field detecting element 131.
Amplifier circuits 201 and 202 for amplifying the electric signals of the magnetic field waveforms from the respective converters and 132, and waveform shaping circuits 203 and 204 for inputting the amplified signals and shaping them into rectangular waves, respectively.
And a combining circuit 205 for inputting each of the rectangular signals and outputting 20 pulses per one rotation of the magnet ring 12.

The extremely low speed detecting means 3 includes a waveform change rate deriving means 31, a speed deriving means 32 and a malfunction preventing means 33.
It is equipped with. The waveform change rate deriving unit 31 samples the electric signal of the magnetic field waveform H1 amplified by the amplifier circuit 201 at an interval of twice Δt, as shown in FIG. As shown in FIG. 7A, the sample and hold circuit 301-a for sample and hold as a voltage value and the electric signal of the magnetic field waveform H1 are provided at an interval of twice Δt and at the sample and hold circuit 301-a.
And the sampling hold result of the sample hold circuit 301-a and the sample hold result of the sample hold circuits 301-a and 301-b. That is, as shown in FIG. 7B, the arithmetic circuit 303 that obtains the voltage value as the variation amount ΔV1 of the Δt interval of the magnetic field waveform H1 and the variation amount ΔV1 are
As shown in FIG. 7 (c), a comparison circuit 30 that compares the threshold value corresponding to the vehicle speed to the threshold value or less and outputs the rectangular wave signal.
5, similarly to the electric signal of the magnetic field waveform H2 amplified by the amplifier circuit 202, as shown in FIG.
A sample and hold circuit 30 that samples at an interval of twice t and samples and holds as a voltage value for twice the value of Δt.
2-a and the electric signal of the magnetic field waveform H1 are shown in FIG.
As shown in FIG. 3, the sample-hold circuit 3 performs sampling at the interval of twice the Δt and at the sampling timing with the sample-hold circuit 302-a with a shift of the Δt time, and sample-holds as a voltage value for twice the Δt.
02-b and the sample and hold results of the sample and hold circuits 302-a and 302-b, that is,
As shown in FIG. 7 (e), the calculation circuit 304 determines the voltage value as the change amount ΔV2 of the Δt interval of the magnetic field waveform H2, and the change amount ΔV2 corresponds to the vehicle speed as shown in FIG. 7 (f). A comparison circuit 306 which compares the threshold value or more or less and outputs the rectangular wave signal, and the comparison circuits 305 and 306.
7 (c) and 7 (f) to synthesize the rectangular waves respectively, and output as shown in FIG. 7 (g).
Including and In the example shown in FIG. 7 (g), the vehicle speed is equal to or higher than the threshold value.

Since the speed deriving means 32 presets the reference magnetic field change amount as a reference signal of a plurality of comparators from the relationship between the magnetic field change amount and the vehicle speed obtained in advance as shown in FIG. , When the detected magnetic field change amount exceeds any of the reference magnetic field change amounts, the speed corresponding to the reference magnetic field change amount is obtained. Therefore, the waveform change rate deriving means 3
The speed is output to a display unit (not shown) using the amount of change (rate of change) of the waveform per unit time obtained by 1 as a parameter.

Further, the malfunction prevention means 33 includes a malfunction prevention circuit 308 and a vehicle speed determination circuit 309 for preventing malfunction when the vehicle speed is a certain value or more. by the way,
The magnetic field distribution waveforms detected by the magnetic field detecting elements 131 and 132 can obtain the number of revolutions corresponding to the vehicle speed, so that the cycle of the magnetic field distribution waveform becomes faster as the vehicle speed becomes faster. When the magnetic field distribution waveform is sampled at Δt intervals under the above conditions, the cycle of the magnetic field distribution waveform becomes shorter than the Δt interval as the vehicle speed increases (hereinafter referred to as sampling theorem). In the above case, the correct rate of change of the magnetic field distribution waveform at the Δt time cannot be detected (for example, when the magnet ring 12 is magnetized with 20 poles and a rectangular wave signal of 20 pulses per revolution of the rotor is obtained, the sample hold circuit 301 −
In the case where the sampling time of a, 301-b, 302-a, 302-b is 50 ms, sampling is performed at Δt intervals in order to avoid the deviation from the sampling theorem at a vehicle speed of about 11.7 km / h or more). , It is necessary to detect the vehicle speed that deviates from the sampling theorem. Therefore, the malfunction prevention circuit 308 detects a vehicle speed deviating from the sampling theorem based on the vehicle speed pulse from the synthesis circuit 205 and outputs a rectangular wave signal. Thereby, the reliability can be improved.

The vehicle speed determination circuit 309 synthesizes the output signal of the speed deriving means 32 and the output signal of the malfunction prevention circuit 308 to determine whether the current vehicle speed is higher or lower than the vehicle speed set as the threshold value. Are detected at Δt intervals. FIG. 8 is a view showing a speed detecting device according to another embodiment of the present invention,
FIG. 9 is a flow chart for explaining the operation of the extremely low speed detecting means of FIG. The extremely low speed detecting means 3 in FIG. 6 is shown as an analog circuit, but in the embodiment shown in FIG. 7, the extremely low speed detecting means 3 is a microcomputer (for example, a built-in A / D, Mitsubishi M
50927). In the case where two magnetic field detecting elements are used, as will be described with reference to FIG. 9, first in step 101, vehicle speed pulses from the synthesizing circuit 205 are used to perform A / D conversion (Analog to Digita) at Δt intervals.
l Check whether the vehicle speed deviates from the sampling theorem during conversion. If yes (removed), return to step 101. Step 1 in case of knowing (does not come off)
Go to 02.

In step 102, it is inspected whether or not Δt time which is the A / D conversion interval has elapsed. If the answer is No (before elapse), the procedure returns to step 101. If the answer is yes (after elapse), the procedure proceeds to step 103. In step 103, the magnetic field waveforms from the two magnetic field detection elements 131 and 132 are individually A / D converted at Δt intervals.

In step 104, based on the result of the A / D conversion, the result of the A / D conversion before Δt time and the current A / D conversion are performed.
By comparing the results, the amount of change in the magnetic field at the Δt interval is individually calculated for the two waveforms. Next, at step 105, a value (SΔV) having a large magnetic field change amount is calculated from the two magnetic field change amounts.

Next, at step 106, the vehicle speed corresponding to SΔV is retrieved from the map showing the relationship between the magnetic field change amount and the vehicle speed shown in FIG. In step 107, the vehicle speed is displayed.
Although only one threshold value of the magnetic field change amount is provided in the above embodiments, a plurality of vehicle speeds can be detected by setting a plurality of threshold values.

Further, although the case where two magnetic field detecting elements are used is shown this time, a plurality (n) of magnetic field detecting elements may be used. In this case, the optimum position of each magnetic field detection element arrangement is when the phase difference of the magnetic field waveform detected by each magnetic field detection element is 180 ° / n. Further, it is obvious that the detection may be performed by using a magnetoresistive element (MRE) as the magnetic field detecting element.

In the above, the permanent magnets on the disk in which the magnetic poles are formed at equal intervals at 20 positions in the circumferential direction are used, but it is clear that the number of magnetic poles may be two or more. Also, this time, the transmission driven gear was shown as a place where the rotation speed corresponding to the vehicle speed generated while the vehicle is running was shown. Any place where you can get a number.

[0026]

As described above, according to the present invention, a plurality of waveform signals that continuously change based on the rotation of the rotary shaft are generated, and one of them is a waveform signal having a small slope and a small change rate. Even if a waveform is detected, the other waveform signal detection means can detect the waveform at a place where the slope of the waveform is large and the rate of change is large. From the relationship between a certain waveform change rate and speed, the extremely low speed of the vehicle is instantaneously obtained using the change rate of the detected waveform signal as a parameter.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a vehicle speed signal generating means according to an embodiment of the present invention.

FIG. 2 is a diagram showing a phase difference between magnetic field waveforms and a magnetic field waveform change rate.

FIG. 3 is a diagram showing a relationship between a magnetic field waveform change amount per unit time and a vehicle speed when two magnetic field detection elements are used.

FIG. 4 is a diagram showing a relationship between a magnetic field waveform change amount per unit time and a vehicle speed when three magnetic field detection elements are used.

FIG. 5 is a diagram showing a relationship between a magnetic field waveform change amount per unit time and a vehicle speed when six magnetic field detection elements are used.

FIG. 6 is a diagram illustrating a configuration for deriving an extremely low speed according to the embodiment of the present invention.

FIG. 7 is a diagram showing signal waveforms of respective portions of the extremely low speed detecting means of FIG.

FIG. 8 is a diagram showing a speed detection device according to another embodiment of the present invention.

9 is a flow chart for explaining the operation of the extremely low speed detecting means of FIG.

[Explanation of symbols]

 2 ... Vehicle speed pulse generating means 3 ... Very low speed detecting means 11 ... Rotating shaft 12 ... Plural waveform generating means 13 ... Plural waveform signal detecting / generating means 31 ... Waveform change rate deriving means 32 ... Speed deriving means 33 ... Malfunction preventing means 121 ... Magnet ring 131, 132 ... Magnetic field detection element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiji Aoki 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (3)

[Claims] 1. A speed detecting device for detecting the rotation of a rotating shaft (11) of a vehicle to detect the speed of the vehicle, wherein a plurality of waveforms per rotation are continuously changed based on the rotation of the rotating shaft (11). A plurality of waveform signal generating means (12) for generating signals, a plurality of waveform signal detecting means (13) for detecting the waveform signals at constant phase differences, and deriving the rate of change of each detected waveform signal. A waveform change rate deriving means (31) for synthesizing the change rate, and a speed using the change rate of the waveform signal obtained by the waveform change rate deriving means as a parameter from the relationship between the synthesized waveform change rate and the speed that has been created in advance. And a velocity derivation means (32) for obtaining the velocity detection device. 2. The plurality of waveform signal generating means (12) are magnet rings magnetized in multiple poles, and the plurality of waveform signal detecting means (13) detect a plurality of changes in magnetic field distribution caused by the magnet rings. 2. The speed detecting device according to claim 1, which is the magnetic field detecting means. 3. The malfunction prevention means (33) for stopping the use of the speed obtained by the speed deriving means when the vehicle speed is equal to or higher than a predetermined value. Speed detection device.