JP2000098049A - Vehicle sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately judge whether a vehicle exists or not by detecting the phase difference between reception and transmission signals and judging whether the level of the reception signal and the phase difference are larger than a threshold or not. SOLUTION: An oscillation circuit 11 generates a pulse signal with a specific period and a transmission circuit 10 receives it and excites a transmission coil 5. A reception signal is induced in a reception coil 6 by alternate magnetic flux being generated by the transmission coil 5. An output line from the oscillation circuit 11 to the transmission coil 5 is branched and is connected to a phase difference detection circuit 12, and a transmission signal is inputted as a pulse signal. A pulse reception signal is also inputted to the phase difference detection circuit 12, where the phase difference between the reception signal and the transmission signal is detected and is outputted to a CPU 13. An amplitude detection circuit 18 detects the level of the amplitude of the reception signal and compares it with a threshold being received from the CPU 13 and then returns the result to the CPU 13. The CPU 13 outputs a vehicle detection signal when the amplitude of the reception signal is larger than the threshold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic flux transmission / reception type vehicle sensor.

[0002]

2. Description of the Related Art As shown in FIG. 1, a vehicle sensor of this type includes, for example, a transmission coil 5 and a reception coil 6 which are arranged apart from each other in a deep part of a parking lot. An alternating magnetic field having a predetermined period is generated between the coils 5 and 6,
The position of the vehicle approaching the two coils 5 and 6 in the alternating magnetic field is detected based on the electromotive force induced electromagnetically by the receiving coil 6. Here, when a metal body such as a vehicle approaches the coils 5 and 6, the number of magnetic fluxes linked to the receiving coil 6 increases. Therefore, as shown in FIG. 8, the relationship is established that the amplitude of the reception signal guided to the reception coil 6 increases as the vehicle approaches the sensor. And
When the amplitude becomes larger than the threshold value, the sensor operates assuming that the vehicle has approached the predetermined distance L1. Thereby, for example, the vehicle is parked in the toll parking lot, and the toll timer is started.

[0003]

However, there is a case where a foreign substance which is a metal body different from the vehicle, for example, a juice can C rolls into the parking lot and enters (see FIG. 7). When the can of juice approaches the vehicle sensor, the relationship between the approach distance and the amplitude of the reception signal guided to the reception coil 6 is shown by a broken line in FIG. Since the can is a metal body smaller than the vehicle, the sensor does not operate when the can approaches the predetermined distance L1. However, as shown in the figure, when the can approaches the distance L5 far beyond the predetermined distance L1, the amplitude of the received signal exceeds the threshold value in the same manner as when the vehicle approaches the predetermined distance L1. The sensor operates. For this reason, for example, a trouble such as the start of the toll timer may occur even though the vehicle is not parked in the toll parking lot.

[0004] A magnetic flux transmission / reception type vehicle sensor different from the one described above detects a vehicle approaching a predetermined distance based on a phase difference between transmission and reception signals of both coils. No. 58-36653. Here, a relationship is established between the approach distance of the vehicle to the sensor and the phase difference, as shown in FIG. 9, as the vehicle approaches the sensor, the phase difference increases. Then, when the phase difference becomes larger than the threshold,
The sensor operates assuming that the vehicle has approached the predetermined distance L1. However, even with such a phase difference,
When the can approaches the distance L6 far exceeding the predetermined distance L1, the can is erroneously detected as a vehicle in the same manner as described above.

The present invention has been made in view of the above circumstances, and has as its object to provide a vehicle sensor capable of accurately determining the presence or absence of a vehicle.

[0006]

According to a first aspect of the present invention, there is provided a vehicle sensor for detecting whether or not a vehicle has approached beyond a predetermined distance. An oscillation circuit that outputs a periodic transmission signal, a transmission coil that generates a magnetic flux based on the transmission signal, a reception coil that outputs a reception signal by linkage of the magnetic flux, and detects a phase difference between the reception signal and the transmission signal. A phase difference detection unit, a comparison unit that operates when the magnitude of the received signal is larger than the threshold, and a threshold setting unit that sets a threshold based on the phase difference detected by the phase difference detection unit. The unit determines the threshold from a threshold curve indicating the magnitude of the received signal that is linked to the transition of the phase difference, and the threshold curve is linked to the transition of the phase difference associated with the approach of a foreign object in all phase differences. The size of the received signal The standard vehicle has approached a predetermined distance with respect to the standard vehicle curve that is set to be larger than the foreign object curve and indicates the magnitude of the received signal that is linked to the transition of the phase difference accompanying the standard vehicle approach. Intersect at the corresponding point of time, and on the side where the phase difference is smaller than the corresponding point, it is set larger than the standard vehicle curve, and on the side where the phase difference is larger than the corresponding point, it is set smaller than the standard vehicle curve. Having.

According to a second aspect of the present invention, in the vehicle sensor according to the first aspect, the received signal becomes larger than the threshold value by the comparing unit within a predetermined time after the phase difference detecting unit starts detecting that there is a phase difference. It is characterized in that a foreign substance detection signal is output when this cannot be detected.

[0008]

<Operation and Effect of the Invention><Invention of claim 1> When the vehicle sensor is driven, the transmission coil is excited based on a transmission signal of a predetermined period from the oscillation circuit, and a magnetic flux is generated. Due to the linkage of the magnetic flux, a reception signal is induced in the reception coil, and is taken into the phase difference detection unit and the comparison unit. Here, when the vehicle approaches the vehicle sensor, since the vehicle is provided with a metal body, the magnetic flux density increases, the amplitude of the reception signal guided to the reception coil increases, and the reception signal and the transmission signal increase. And the phase difference increases. Then, the phase difference is detected by the phase difference detection unit, and the threshold setting unit that has received the phase difference sets the threshold and sends it to the comparison unit to determine whether the received signal is larger than the threshold.

Here, the threshold value setting section determines the threshold value from a threshold value curve indicating the magnitude of the received signal that is linked to the transition of the phase difference. Since the standard vehicle is set so as to intersect with the standard vehicle curve indicating the magnitude of the received signal linked to the transition of the phase difference at the corresponding point when the standard vehicle approaches the predetermined distance, the actual vehicle When approaching beyond the distance, the received signal exceeds the threshold and increases, and it is determined that the vehicle is present.

Now, there is a case where a foreign object approaches the vehicle sensor. Here, the foreign substance refers to a metal body other than the vehicle, such as a can, for example, and is assumed to be determined by the user of the vehicle sensor. The threshold curve is set to be larger for all phase differences than the foreign matter curve indicating the magnitude of the received signal linked to the transition of the phase difference accompanying the approach of the foreign matter. Accordingly, even if the foreign object approaches the vehicle sensor beyond the predetermined distance and the amplitude of the received signal increases, the threshold value cannot be exceeded and the foreign object is not erroneously detected as a vehicle. Thus, according to the vehicle sensor of the present invention,
The presence or absence of a vehicle can be accurately detected.

<Invention of Claim 2> When the vehicle approaches the vehicle sensor, a phase difference occurs in the transmission / reception signal, and this is detected by the phase difference detection unit. Then, when the vehicle approaches beyond a predetermined distance within a predetermined time, the comparison unit detects that the received signal has become larger than the threshold value. Therefore, in this case, no foreign object detection signal is output. On the other hand, when a foreign substance such as a metal body other than the vehicle approaches the vehicle sensor, the phase difference is detected but the received signal does not exceed the threshold,
The foreign object detection signal is output without the comparison unit operating within a predetermined time.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. The vehicle sensor according to the present embodiment includes a transmission unit 1 and a reception unit 2, which are installed in the back of a parking lot side by side and at a predetermined interval (see FIG. 1). Both units 1 and 2
As shown in FIG. 2, a case 23 made of a synthetic resin,
The transmission coil 5 or the reception coil 6 is accommodated in 24 and is covered with, for example, stainless steel covers 21 and 22. And electric wires 30, 3 extending from both coils 5, 6
1 is connected to a control unit (not shown), and the entire vehicle sensor has an electrical configuration as shown in FIG.
Specifically, it is as follows.

A transmission circuit 10 and an oscillation circuit 11 are connected to an electric wire 30 extending from the transmission coil 5. The oscillation circuit 11 generates a transmission signal that is a pulse signal having a predetermined period. The transmission circuit 10 receives the transmission signal and excites the transmission coil 5. As a result, the transmitting coil 5 generates an alternating magnetic flux having the same cycle as the transmitting signal, and the alternating magnetic flux induces the receiving signal to the receiving coil 6. The output line from the oscillation circuit 11 to the transmission coil 5 is branched and connected to the phase difference detection circuit 12,
Here, the transmission signal is input in the form of a pulse signal. The phase difference detection circuit 12 is also configured to receive a reception signal converted into a pulse signal. Here, a phase difference between the reception signal and the transmission signal is detected, and the detection result is transmitted to the CPU 13 (the threshold value of the present invention). (Corresponding to a setting unit).

An electric wire extending from the receiving coil 6 is connected to an amplifier 14.
, And the received signal guided to the receiving coil 6 is amplified. The output line of the amplifier 14 is divided into two systems, and the waveform shaping circuit 1 connected to one output line
The received signal is converted into a pulse signal by 5 and input to the phase difference detection circuit 12. An amplitude detection circuit 18 is connected to the other output line via a waveform rectification circuit 16 and a smoothing circuit 17. Thereby, the amplitude detection circuit 18 (corresponding to the comparison unit of the present invention) can receive the DC-converted reception signal. Then, the magnitude of the amplitude of the received signal is taken out, compared with the threshold value received from the CPU 13, and a comparison result as to whether the amplitude is larger than the threshold value is sent back to the CPU 13.

The CPU 13 determines a threshold based on the detection result of the phase difference detection circuit 12 and
8 is output. The threshold is stored in the memory 19 connected to the CPU 13 in advance. The threshold data stored in the memory 19 is set based on the threshold curve shown in FIG. 4. This threshold curve is different from the data when a standard vehicle approaches the vehicle sensor and differs from the vehicle. This is based on data when a metal body, for example, a juice can (in this embodiment, a can is assumed as a foreign object) rolls into the parking lot and enters. Here, as described in the related art, when the vehicle, which is a metal body, approaches the vehicle sensor, there is a relationship that the amplitude of the reception signal guided to the reception coil 6 and the phase difference between the transmission and reception signals increase (FIG. 8 and FIG. 9). Then, in the graph of FIG. 4, the magnitude of the amplitude that is linked to the transition of the phase difference when the standard vehicle and the can approach the vehicle sensor is shown as a standard vehicle curve and a foreign matter curve. In this graph, the vehicle approaches the sensor as the abscissa advances to the right. Further, since the can is a metal body smaller than the vehicle, the foreign matter curve has a smaller value as a whole than the standard vehicle curve.

The threshold curve is set larger than the foreign matter curve in all phases to prevent the vehicle sensor from detecting cans. Then, for example, when the vehicle approaches the sensor to a predetermined distance L1 in the standard vehicle curve, so that the sensor detects the vehicle when the vehicle approaches the sensor beyond a predetermined distance L1 (see FIG. 1). At the corresponding point A (see FIG. 4), and on the side where the phase difference is smaller than the phase difference θ1 of the corresponding point A, the threshold curve becomes the amplitude R1 of the standard vehicle curve at the corresponding point A. And extends horizontally, and the phase difference θ1 of the corresponding point A
On the side where the phase difference is larger than the standard vehicle curve, it is set smaller. In the memory 19, based on the threshold curve, each phase difference and the magnitude of each corresponding amplitude
Data stored in one dimension is stored.

The CPU 13 outputs a threshold value to the amplitude detection circuit 18 based on the detection result of the phase difference detection circuit 12, and the amplitude detection circuit 18 sends a comparison result between the threshold value and the received signal to the CPU 13. Send it back. The flow of this process is shown in the flowchart of FIG. This will be described below together with the operation and effect of the present embodiment.

When the power supply of the vehicle sensor according to the present embodiment is turned on, a transmission signal, which is a pulse signal having a predetermined period, is output from the oscillation circuit 11, and based on this, the transmission coil 5 is excited to enter the parking lot at a predetermined period. An alternating magnetic flux is generated. Then, a reception signal is induced in the reception coil 6 by the linkage of the magnetic flux, and the reception signal is amplified by the amplifier 14. This is converted into a pulse signal by the waveform shaping circuit 15 and taken into the phase difference detection circuit 12, and the phase difference between the transmission signal and the reception signal is detected. The CPU 13 stores this phase difference in the register T in STEP 1 of the flowchart shown in FIG.
In step X2, it is determined whether TX is correct. Here, when a metal body such as a vehicle does not enter the parking lot, TX does not become positive because there is no phase difference between the transmission signal and the reception signal. Therefore, STEP
The route proceeds from NO to NO and it is determined that there is no vehicle (STEP 3), and the timer programmed in the software of this flowchart is reset (STEP 4) to return to ST.
Return to EP1.

Now, when the vehicle enters the parking lot,
As shown in FIG. 1, the vehicle enters the magnetic field generated by the transmission coil 5. Here, since the vehicle is provided with the metal body, the magnetic flux density is higher than at the time of non-detection when the vehicle is not in the parking lot. In addition, since the vehicle sensor is disposed in the back part of the parking lot, as the vehicle goes to the back part of the parking lot, the lines of magnetic force penetrating the vehicle increase, and the magnetic flux density further increases. Then, the amount of magnetic flux linked to the reception coil 6 increases, the amplitude of the reception signal guided to the reception coil 6 increases, and the phase difference between the transmission and reception signals increases. Then, as shown in FIG. 1, for example, when the vehicle approaches the sensor to a distance L2 farther than the predetermined distance L1, the phase difference θ2 approximate to the corresponding point B of the distance L2 in the standard vehicle curve shown in FIG. The amplitude R2 of the signal is detected by the two detection circuits 12, 18. Then, the phase difference θ2 is taken into the register TX. Then TX> 0
Therefore, YE of STEP 2 in the flowchart is performed.
Proceeding to the route of S, the threshold M corresponding to TX is stored in the memory 19
(STEP 5), and the threshold value M is output to the amplitude detection circuit 18 (STEP 6). Then, the amplitude detection circuit 18 compares the threshold value M with the amplitude R2 of the received signal (STEP 7). Here, the threshold data recorded in the memory 19 is set based on a threshold curve shown in FIG. 4, and the threshold curve is smaller than the phase difference θ1 when the vehicle approaches the predetermined distance L1. In the case of a phase difference, the amplitude R1 is set so as to extend horizontally with the value of the amplitude R1 and become larger than the standard vehicle curve. Therefore, when the vehicle reaches the distance L2 to the sensor, the amplitude R2 is equal to the threshold M It is detected that it is not larger than (STEP 7), and the detection result is sent back to the CPU 13. The CPU 13 branches into two routes depending on whether or not the detection result is larger than the threshold value M. When it is determined that the detection result is not larger than the threshold value M as described above, the process proceeds to STEP 8 to determine whether or not the count of the timer is 0. Is determined. Here, the above STEP4
Since the timer count is reset to 0 at
Proceeding to the YES branch of STEP8, the timer is started in STEP9, and the count is incremented in STEP10.

Then, in the next STEP 11, it is determined whether or not the timer count value has reached the reference value. Here, the reference value is set to, for example, a count value corresponding to a case where 15 minutes have elapsed from the start of the timer. Therefore, since it does not take 15 minutes for the vehicle to enter the interior of the parking lot, the timer count value does not reach the reference value, and the determination is NO and the process returns to STEP1.

When the vehicle advances to the far side of the parking lot and approaches beyond the sensor operating distance L1 (see FIG. 6), a phase difference θ3 larger than θ1 in FIG. Thus, the threshold value M is set and output to the amplitude detection circuit 18. Here, as shown in FIG. 4, the threshold curve serving as a reference for determining the threshold is set so that when the detected phase difference becomes larger than the phase difference θ1 on the graph, it becomes smaller than the standard vehicle curve. Therefore,
The amplitude detection circuit 18 detects in step 7 that the amplitude of the received signal is larger than the threshold value M, and
It is taken in. Then, in STEP12, it is determined that the vehicle is present, the timer is reset, and (STEP12).
13), a vehicle detection signal is output (STEP 14).
Thereby, for example, the charge timer provided for the parking lot starts to be started.

By the way, there is a case where a foreign substance which is a metal body different from the vehicle, for example, a can of juice rolls into the parking lot and enters (see FIG. 7). However, in the present embodiment,
The threshold curve is set to be larger at all phase differences than the foreign object curve indicating the relationship between the phase difference detected when the juice can approaches the vehicle sensor and the magnitude of the received signal. Therefore, the threshold value M set in STEP 6 is always set to a value larger than the received signal for the can. Therefore, when the can enters the parking lot, STEP
At 7, the routine always proceeds to the NO route, and the timer count continues to increase. As a result, the can rolls into the parking lot and
When 5 minutes have elapsed, it is recognized in STEP 11 that the timer count has reached the reference value, and in STEP 15 it is determined that there is a foreign object, and a foreign object detection signal is output in STEP 16 to prepare, for example, for parking. The warning light comes on.

Also, the vehicle is not pushed into the back of the parking lot, and is parked farther than a predetermined distance L1 from the sensor.
When 5 minutes have elapsed, the timer count exceeds the reference value and the warning light is turned on, as in the case of the can. Thus, a warning that the parking position is inappropriate can be issued.

As described above, according to the vehicle sensor of this embodiment, the presence / absence of a vehicle can be accurately detected. Further, foreign objects other than the vehicle are present in the parking lot, and the vehicle is parked at an inappropriate position. Can also be detected.

<Other Embodiments> The present invention is not limited to the embodiments. For example, the following embodiments are also included in the technical scope of the present invention. Various changes can be made without departing from the scope of the invention. (1) In the above-described embodiment, the threshold value M is output from the CPU 13 to the amplitude detection circuit 18, and whether or not the received signal is larger than the threshold value is detected by hardware. May be taken into the CPU and the comparison with the threshold value may be performed by a program.

(2) Although the transmission circuit of the above embodiment generates the transmission signal as a pulse, it may generate the transmission signal as a sine wave.

(3) In the present invention, the threshold value to be compared with the magnitude of the received signal is set based on the phase difference between the transmitted signal and the received signal. It is also possible to adopt a configuration in which a threshold value is set in advance and vehicle detection is performed by comparing the threshold value with the phase difference.

[Brief description of the drawings]

FIG. 1 is a plan view of a parking lot provided with a vehicle sensor according to a conventional example and an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a vehicle sensor.

FIG. 3 is a block diagram of a vehicle sensor.

FIG. 4 is a graph showing a standard vehicle curve and a threshold curve.

FIG. 5 is a flowchart showing processing of a CPU and an amplitude detection circuit;

FIG. 6 is a plan view showing a state where the vehicle sensor is parked in the back of the parking lot.

FIG. 7 is a plan view showing a state in which a can has entered the parking lot.

FIG. 8 is a graph showing the relationship between detection distance and amplitude.

FIG. 9 is a graph showing a relationship between a detection distance and a phase difference.

[Explanation of symbols]

 5 ... Transmission coil 6 ... Reception coil 10 ... Transmission circuit 11 ... Oscillation circuit 13 ... CPU (threshold setting unit) 12 ... Phase difference detection circuit (Phase difference detection unit) 18 ... Amplitude detection circuit (Comparison unit) L1 ... Predetermined distance

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Daisuke Hayakawa 3-5-3, Akebonocho, Tachikawa-shi, Tokyo F-term (reference) 2G005 CA02

Claims (2)

[Claims] 1. A vehicle sensor for detecting whether a vehicle has approached beyond a predetermined distance, comprising: an oscillation circuit for outputting a transmission signal of a predetermined period; and generating a magnetic flux based on the transmission signal. A transmitting coil to be output; a receiving coil that outputs a received signal by interlinking the magnetic flux; a phase difference detecting unit that detects a phase difference between the received signal and the transmitted signal; and a magnitude of the received signal is larger than a threshold value. And a threshold setting unit that sets a threshold based on the phase difference detected by the phase difference detection unit, wherein the threshold setting unit interlocks with the transition of the phase difference. The threshold value is determined from a threshold curve indicating the magnitude of the signal, and the threshold curve indicates, for all phase differences, a foreign substance indicating the magnitude of the reception signal that is linked to the transition of the phase difference accompanying the approach of the foreign substance. From the curve While being set to be large, the standard vehicle has approached the predetermined distance with respect to the standard vehicle curve indicating the magnitude of the received signal that is linked to the transition of the phase difference with the approach of the standard vehicle. Intersect at the corresponding point at the time, on the side where the phase difference is smaller than the corresponding point, is set larger than the standard vehicle curve, and on the side where the phase difference is larger than the corresponding point, set smaller than the standard vehicle curve. A vehicle sensor, comprising: 2. The vehicle sensor according to claim 1, wherein
Within a predetermined time after the phase difference detection unit starts detecting that there is a phase difference, when the comparison unit cannot detect that the reception signal has become larger than a threshold value, a foreign object detection signal is output. Vehicle sensor.