Communications: electrical – Vehicle detectors
Reexamination Certificate
1999-11-19
2003-03-18
Lee, Benjamin C. (Department: 2632)
Communications: electrical
Vehicle detectors
C340S928000, C340S572100, C340S005420, C340S941000, C705S013000
Reexamination Certificate
active
06535143
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vehicle detection system for detecting a passage of a vehicle in a non-contact manner, and more particularly to a vehicle detection system capable of discriminately detecting between predetermined specific vehicles and other vehicles and being usable at a parking area or the like.
2. Description of the Related Art
Loop coils buried in the ground have been generally used as a vehicle detection system for managing vehicles incoming and outgoing a parking area. A detection principle of this vehicle detection system is as follows. When a vehicle comes over a loop coil, a parameter of the loop coil changes and this change is detected. For example, when the inductance of a loop coil changes, this inductance change is detected to detect that a vehicle is over the loop coil, and a detection signal is generated.
A conventional vehicle detection system of such a type is shown in FIG.
9
. In a conventional vehicle detection system
100
, a loop coil
1
buried under an inlet road of a parking area forms a resonance circuit with a capacitor
102
of a self-oscillator
101
which oscillates at the resonance frequency of the resonance circuit. An oscillation output of the self-oscillator
101
is supplied to a frequency discriminator
103
which generates a d.c. voltage corresponding to the oscillation frequency of the self-oscillator
101
. A d.c. voltage output from the frequency discriminator
103
is supplied to an A/D converter
104
to convert it into a digital signal. This digital signal is supplied to a controller
105
which compares it with a predetermined threshold value to detect the vehicle.
When a vehicle A comes over the loop coil
1
, the inductance of the loop coil
1
lowers because of an eddy current loss by a vehicle body and the oscillation frequency of the self-oscillator
101
shifts to a higher frequency. Therefore, an output of the A/D converter
104
exceeds the threshold value. The controller judges that the vehicle A is over the loop coil
1
, and generates a vehicle detection signal. In response to this vehicle detection signal, a ticket vendor
2
and a car gate driver circuit
3
are operated to issue a parking ticket, and when the parking ticket is picked up by the driver, a car gate
4
is opened. In this manner, vehicles incoming and outgoing the parking area are managed. The frequency discriminator
103
is realized by a ratio detector or the like. It can also be realized by a frequency counter. In this case, the A/D converter
104
can be omitted and the count of the frequency counter is directly supplied to the controller
105
to process it.
Charged parking areas include a time charging parking area which charges in accordance with the parked time and a monthly contract charging parking area which contracts on a month unit basis. Most of large time charging parking areas also provide monthly contract charging. Almost all such combined parking areas have a space in the parking area for allowing vehicles of persons in charge of the parking area to be parked.
Such combined parking areas provide services of giving a card to each driver of a specific vehicle such as a contracted vehicle and a vehicle associated with the parking area, and allowing the driver to freely come in and go out of the parking area. Although such a card is used generally by inserting it into a ticket vendor or a fare adjuster, there is a card of a different type whose contents can be read while the driver holds it up in the vehicle. A parking area in/out management system which allows both types of cards has a non-contact card reader. A non-contact card is called a transponder of a non-contact discrimination system which is formed in a card shape.
A vehicle management system of a parking area using both a vehicle detection system and a non-contact card reader is configured as shown in FIG.
10
.
FIG. 10
shows the parking area incoming side. As shown in
FIG. 10
, this system is constituted of a non-contact card reader
107
with a card antenna
106
, a vehicle detection system
100
A with a loop coil
1
A, a ticket vendor
2
, a car gate driver
3
, and another vehicle detection system
100
B with a loop coil
1
B, all being connected to a controller
105
A and disposed in this order from the upstream side of the inlet road of the parking area. The vehicle detection systems
100
A and
100
B have the structure same as the vehicle detection system
100
shown in FIG.
9
. When the controller
105
A detects that a vehicle comes over the loop coil
1
A, it operates the ticket vendor
2
and car gate driver
3
. After the ticket is issued, a car gate
4
is opened. When the controller
105
A detects that the vehicle comes over the loop coil
1
B, it operates the car gate driver
3
to close the car gate
4
. The parking area outlet side is structured in a similar manner except that the ticket vendor is replaced by a fare adjuster.
However, although it is convenient if such a conventional non-contact card reader is provided in combination with an insertion type card reader, the conventional system is associated with some problems. One problem is that a driver is required to carry a card and hold it up when the vehicle comes in and goes out a parking area. If the driver does not hold the card up inadvertently and the vehicle comes over the loop coil, then the ticket vendor issues a parking ticket. Even in such a case, the parking area is required to be managed so that if the driver holds the card up thereafter toward the card reader, the vehicle is allowed to come in the parking area, and the parking ticked once issued becomes wasteful. Another problem is that an illegal parking cannot be inhibited if a card is transferred to a third party from its owner. Another problem is that if a non-contact vehicle discriminator system which discriminates vehicles from vehicle numbers by using image recognition techniques, is used, the camera installation position is limited and the system is expensive.
Some non-contact card readers utilize radio waves, whereas others utilize magnetic fields.
In the former case, a read performance is deteriorated by rains and snows. In such a case, an antenna cannot be buried in the ground, but it is mounted above the ground. There arises therefore a problem that dust-proof and robbery-proof of an antenna is necessary increasing the cost. If a non-contact card reader utilizes microwaves, it is necessary to mount the antenna at the position where a stable read operation is possible in terms of radio wave transmission characteristics, thus posing a problem of a position limitation. Further, in this case, a transponder cannot be mounted under the vehicle body, but it is mounted on the front side of the vehicle body thus degrading the decorative performance of the vehicle body. Also the non-contact card reader utilizing microwaves is associated with some problems that the transponder requires a battery as its power source and is expensive and that the reader is required to receive the model acceptance as a radio wave equipment.
In the latter case, the non-contact card reader utilizes magnetic coupling or magnetic induction. Therefore, a read performance is not affected by rains and snows, an antenna can be buried in the ground, dust-proof and robbery-proof are not necessary, and a transponder can be mounted conveniently under the vehicle body. The distance between the transponder mounted under the vehicle body and the antenna buried under the ground is approximately a distance between the ground surface and the bottom of the vehicle body, so that a stable and less-variation read performance is possible, and the decorative performance of the vehicle body is not damaged. Further with magnetic coupling or magnetic induction, the transponder is not necessary to use a battery, and the reader is not required to receive the model acceptance as a radio wave equipment. However, in the latter case, the frequency range used by the card reader is several tens kHz to several hundreds kHz. The f
Miyamoto Yukihiko
Morimoto Yoshinori
Kabushiki Kaisha Kenwood
Lee Benjamin C.
Robinson Eric J.
Robinson Intellectual Property Law Office P.C.
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