JPH034174A - Speed detecting device for vehicle - Google Patents

Abstract

PURPOSE:To reduce the influence of abnormal oscillation, etc., and to improve the accuracy of vehicle speed arithmetic by varying a sampling period for inputting a vehicle speed pulse signal according to a vehicle speed. CONSTITUTION:A filter 1 inputs and processes a pulse signal outputted by a vehicle speed sensor 6 when a period setting circuit 3 outputs a sampling signal SB. Then when the level of a pulse signal obtained by the last sampling is L0 and the level of a current pulse signal is also L0, the filter 1 outputs an L0-level signal and when the level of the last pulse signal is Hi and the level of the current pulse signal is also Hi, an Hi-level signal is outputted. Then a vehicle measuring circuit 2 inputs the pulse signal outputted by the filter 1, calculates the vehicle speed from the number of pulses inputted within a specific time, and decides which of a fast, an intermediate, and a slow speed area the vehicle speed is in to output a signal Hi, Me, or L0, thereby reducing the influence of abnormal oscillation, etc.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a speed detection device for a vehicle. It can be used as a vehicle speed control.

(Prior Art) Conventionally, a vehicle speed sensor mounted on a vehicle includes a magnet that is rotated by the rotation of a speedometer cable or a gear of a transmission, and a reed switch or a magnetically sensitive element that is driven by this magnet. In the vehicle speed sensor configured as above, a magnet rotates at a speed corresponding to the vehicle speed, and a pulse signal having a frequency proportional to the vehicle speed is output from the reed switch or the magnetic sensing element.

[Problem to be solved by the invention]

However, in the above vehicle speed sensor, the cable or the sensor itself may cause abnormal oscillation due to engine vibration or the like. Here, the vehicle speed sensor has a speed of about 0 to 200 km/h, that is, O when converted to the frequency of the pulse signal.
It outputs pulse signals with a wide frequency range of about 1,427 to 1,427. The signal processing circuit that calculates the vehicle speed from this pulse signal must reliably read pulse signals having a wide range of frequencies as described above. For this reason, conventional signal processing circuits capture pulse signals at a fixed sampling period that matches the maximum speed of the vehicle. However, if abnormal oscillations such as those described above occur, there is a possibility that an error may occur in the vehicle speed calculation performed by the signal processing circuit, especially if the signal processing circuit receives an oscillation input at a frequency corresponding to a high speed when the vehicle speed is low.

The present invention has been made in view of the above points, and by appropriately changing the sampling period for capturing the vehicle speed pulse signal according to the vehicle speed, accurate vehicle speed calculation is possible even when abnormal oscillation occurs in the vehicle speed sensor etc. An object of the present invention is to provide a vehicle speed detection device capable of performing the following steps.

[Means to solve the problem]

In order to achieve the above object, the speed detection device for a vehicle according to the present invention includes a pulse signal ordering means for generating a pulse signal with a frequency corresponding to the running speed of the vehicle, and a pulse signal generated by the pulse signal generating means intermittently. output means for outputting a signal of a failed level when the level of the pulse signal taken in last time and the level of the pulse signal taken in this time match; The vehicle is configured to include a calculation means for calculating a traveling speed, and a period variable means for lengthening the sampling period at which the output means takes in the pulse signal as the travel speed calculated by the calculation means becomes lower.

[Effect]

According to the vehicle speed detection device configured as above,
The period variable means lengthens the sampling period at which the output means takes in the pulse signal as the traveling speed of the vehicle decreases. When the level of the pulse signal captured last time matches the level of the pulse signal captured this time, the output means outputs a signal with the matched level, so a pulse signal with a pulse width shorter than this sampling period is input. The signal will be ignored. In other words, even if an abnormal oscillation occurs in the vehicle speed sensor at a frequency equivalent to when the vehicle is running at high speed when the vehicle is running at low speed, the pulse signal input due to the abnormal oscillation is rejected, so the influence of the above abnormal oscillation is reduced. Vehicle speed calculations can be performed.

[Example] A first example of the present invention will be described below with reference to the drawings. 1st
In the figure, a vehicle speed sensor 6 outputs a pulse signal with a frequency proportional to the traveling speed of the vehicle.

The filter 1 receives the sampling signal S from the period setting circuit 3.
When B is output, the pulse signal output from the vehicle speed sensor 6 is captured, and signal processing is performed on this captured pulse signal. In this signal processing, the level of the pulse signal captured in the previous sampling is compared with the level of the pulse signal captured in the current sampling, and if they match, a signal with the matched level is output. That is, when the level of the previous pulse signal is Lo and the level of the current pulse signal is also Lo, a Lo level signal is output from filter l, and when the level of the previous pulse signal is Hi and the level of the current pulse signal is also Hi. When this is the case, a Hi level signal is output. In addition,
If the level of the previous pulse signal and the level of the current pulse signal are different, the filter l maintains the previous output. The vehicle speed measurement circuit 2 inputs the pulse signal output from the filter I, and calculates the vehicle speed from the number of pulses input within a predetermined period of time. Then, it is determined whether the calculated vehicle speed falls within a high speed area, a medium speed area, or a low speed area, and if the vehicle speed is in the high speed area, the high speed signal H1 is applied, and if the vehicle speed is in the medium speed area, the medium speed signal Me is used. , in the case of a low speed region, a low speed signal Lo is output, respectively. In addition, vehicle speed measurement circuit 2
Regarding the speed calculation method, in addition to the above method, for example, the time required for inputting a predetermined number of pulses may be measured, and the vehicle speed may be calculated from this time. The sampling period generating circuit 5 receives the reference signal from the oscillation circuit 4 and determines the high speed region and medium speed region of the vehicle speed.

Three types of timing signals FHFM and FL with different periods suitable for the sampling period of each low speed region are generated. These three types of timing signals Fn, Fs, FL
The period becomes shorter as the speed increases. The sampling period setting circuit 3 selects the timing signal F as the sampling period when the high speed signal Hi is output from the vehicle speed measuring circuit 2, and outputs the sampling signal SB to the filter 1 at a timing according to the timing signal F. Further, when the medium speed signal Me or the low speed signal Lo is output from the vehicle speed measurement circuit 2, the timing signals Fs and Ft are selected as the sampling period, respectively, and the timing signals are applied to the filter 1 at the timing according to the respective timing signals FM and FL. Outputs sampling signal SB.

The operation of the vehicle speed detection device configured as described above will be explained based on the configuration diagram in FIG. 1 and the waveform diagram in FIG. 2.

As shown in FIG. 2, the period is Ions from the vehicle speed sensor 6.
vehicle speed pulse signal (approximately 140 in the vehicle speed sensor of this embodiment)
km/h) is output, the timing signal FM (period 2.5 as
), the period of the pulse signal output from the filter 1 will be 10 m5, and the vehicle speed detected by the vehicle speed detection device will be approximately 140 b/h. On the other hand, when sampling is performed according to the timing signal FM (period: 7.5 ms) corresponding to the medium speed region when a vehicle speed pulse signal corresponding to approximately 140 + n/h is output, the output from filter 1 is The period of the pulse signal is 30ffIS, and the detected vehicle speed is approximately 45
h/h. Furthermore, when sampling is performed according to the timing signal PL (period: 22.5 m5) corresponding to the low speed region, the detected vehicle speed is approximately 15 kI.
II/h. That is, in order to accurately sample the vehicle speed pulse signal output from the vehicle speed sensor 6 at a constant sampling period, a sampling period corresponding to the high speed region must be adopted. However, according to this embodiment, by changing the sampling period according to the vehicle speed, a sampling period appropriate for the vehicle speed is always used. As a result, for example, when the vehicle speed is in a low speed region and the sampling period is 2
2.5 ms, due to abnormal oscillation, about 1
40) Even if an oscillation input corresponding to cm/h occurs,
Only a speed signal corresponding to about 15 km/h is output, and the influence of abnormal oscillation input can be reduced.

Also, considering the influence of vibration caused by engine rotation during idling, a vehicle with an engine rotation speed of 80 orpm when idling has a vibration vibration of approximately 457 (period: approximately 22m5).
．． There is a vibration of approximately 60 low/h (converted to vehicle speed). Here, even if the vehicle speed sensor etc. resonates with the above vibration and oscillates abnormally, if the sampling period is set to 22.5 ms corresponding to the low speed region, then a pulse signal with a period of 50 m5 or more will be detected. This embodiment also works effectively against the influence of vibration caused by engine rotation during idling.

In addition, if it is necessary to input and control the entire vehicle speed range, approximately 6 times per cycle of the vehicle speed pulse signal, taking into consideration the signal processing in filter 1 and the variation in the cycle of the vehicle speed pulse signal. It is desirable to set the sampling period so that sampling is performed. In other words, the low speed range is O~20km/h, and the medium speed range is 20~120h/h.
, if you set the high speed region to 120~2001al/h,
20) The period of the pulse signal output from the vehicle speed sensor 6 at cm/h is 70 ms, the period of the pulse signal at 120) cm/h is 11 ms, and the period of the pulse signal at 200 kII/h is 7 Ins, so the speed is low. The sampling period of the region is set to about 10111s1, the sampling period of the medium speed region is set to about 2s, and the sampling period of the high speed region is set to about 1IIs. ” A flowchart for realizing the operation of the first embodiment described above using a microcomputer is shown in FIG. 3(a).
Shown in (b).

In FIG. 3(a), in step 11, the sampling period FL corresponding to the low-speed area is stored in the memory SMP that stores the sampling period, and the value of the interrupt counter C0UNT, which determines the timing of interrupt processing, is set to correspond to the low-speed area. Initialization processing such as setting the sampling period Ft to a value is performed. In step 12, it is determined whether the vehicle speed is in a low speed region based on the determination result of the multiplex determination process executed in step 18, which will be described later. At this time, if it is determined that the vehicle speed is in the low speed region, the process proceeds to step 13, and the memory SM
The sampling period FL corresponding to the low speed region is stored in P. If it is determined in step 12 that the vehicle speed is not in the low speed region, the process proceeds to step 14, where it is determined whether the vehicle speed is in the medium speed region. At this time, if it is determined that the vehicle speed exists in the medium speed region, the process proceeds to step 15 and the sampling period F corresponding to the medium speed region is stored in the memory SMP, and if it is determined that the vehicle speed does not exist in the medium speed region , proceed to step 16 and store memory S.
The sampling period FM corresponding to the high speed region is stored in the MP. In step 17, the level of the previously captured vehicle speed pulse signal is compared with the level of the currently captured vehicle speed pulse signal, and if they match, it is processed as normal data, and if they do not match, this data is ignored. In step E8, the vehicle speed is calculated based on the vehicle speed data filtered in step 17, and it is determined whether the calculated vehicle speed falls within a range of low speed, medium speed, or high speed, and the determination result is Remember it. Vehicle speed is calculated by repeatedly executing the above process.

On the other hand, in the timer interrupt processing shown in FIG.
Set to the sampling period value stored in P. Then, in step 20, the memory DATA (N
) is stored in the memory DATA (N-1) as the previous data. Step 2
1, the vehicle speed pulse signal is taken in and the level of this pulse signal is stored in the memory DATA as the current data.
Store it in (N).

In this way, the level of the previous vehicle speed pulse signal and the level of the current vehicle speed pulse signal are stored in the memory DAT A (N
~1), are stored in DATA(N), and filter processing is performed in step 17 described above.

FIG. 1 is a block diagram of the first embodiment of the present invention, FIG. 2 is a waveform diagram explaining the operation of the first embodiment, and FIG. 3 is a flowchart when the present invention is implemented using a microcomputer. .

■... Filter, 2... Vehicle speed measurement circuit, 3... Sampling cycle setting circuit, 4... Oscillation circuit, 5...
Sampling cycle generation circuit, 6...vehicle speed sensor.

Claims (1)

[Scope of Claims] Pulse signal generating means for generating a pulse signal with a frequency corresponding to the running speed of the vehicle, which intermittently captures the pulse signal generated by the pulse signal generating means and compares the level of the previously captured pulse signal with the level of the previously captured pulse signal. output means for outputting a signal of the matched level when the level of the pulse signal taken in this time matches; a calculation means for calculating the traveling speed of the vehicle based on the signal output by the output means; and the calculation means. 1. A speed detection device for a vehicle, comprising a period variable means for lengthening a sampling period at which the output means takes in a pulse signal as the running speed calculated by the vehicle becomes lower.