Device, sensor and method for detecting the presence of a user for the opening of an access point to a motor vehicle

Patent metadata

Field	Value
Publication number	US-8970288-B2
Application number	US-201414285790-A
Country	US
Kind code	B2
Filing date	May 23, 2014
Priority date	Jun 7, 2013
Publication date	Mar 3, 2015
Grant date	Mar 3, 2015

Abstract

A device for detecting the presence of a user for the unlocking of an access point to a motor vehicle, includes a first generator of a first supply voltage, a detection capacitor adapted to be charged on account of the presence of a user, and a storage capacitor defining at the terminals thereof a storage voltage. The device also includes an intermediate capacitor, elements for charging the detection capacitor from the first supply voltage and the storage voltage, elements for discharging the detection capacitor into the intermediate capacitor, elements for charging the storage capacitor, the elements being configured so that the charge of the storage capacitor is equal to the charge of the intermediate capacitor, and elements for detecting the presence of a user for the unlocking of an access point to the motor vehicle on the basis of the charge of the storage capacitor.

First claim

The invention claimed is:

1. Device for detecting the presence of a user for the unlocking of an access point to a motor vehicle, said device comprising a first generator of a first supply voltage (Vx), a detection capacitor (Cx) adapted to be charged on account of the presence of a user, and a storage capacitor (Cs) defining at the terminals thereof a storage voltage (Vs), said device being characterized in that it comprises:
an intermediate capacitor (C INT ),
means for charging the detection capacitor (Cx) from the first supply voltage (Vx) and the storage voltage (Vs), comprising voltage summing means, such that the voltage at the terminals of the detection capacitor (Cx) is equal to the sum of the first supply voltage (Vx) and the storage voltage (Vs),
means for discharging the detection capacitor (Cx) into the intermediate capacitor (C INT ) so as to allow the discharge of the detection capacitor (Cx) into the intermediate capacitor (C INT ) at a voltage value equal to the storage voltage (Vs),
first means for charging the storage capacitor (Cs), said means being configured so that the charge of the storage capacitor (Cs) is equal to the charge of the intermediate capacitor (C INT ), and
means for detecting the presence of a user for the unlocking of an access point to the motor vehicle on the basis of the charge of the storage capacitor (Cs).

2. Device according to claim 1 , characterized in that the means for charging the detection capacitor (Cx) comprise a first switch (S 1 ), and the means for discharging the detection capacitor (Cx) into the intermediate capacitor (C INT ) comprise a second switch (S 2 ).

3. Device according to claim 2 , characterized in that the means for detecting comprise:
a second generator of a second supply voltage (Vcc),
second means for charging the storage capacitor (Cs) from the second supply voltage (Vcc),
means for measuring the storage voltage (Vs),
means for measuring a period (t) of charging of the storage capacitor (Cs) between an initial determined moment and a moment at which the storage voltage (Vs) has reached a predetermined storage threshold (V TH ), and,
means for comparing the measured period (t) with a reference period (Tref) so as to detect the presence of a user for the unlocking of an access point to the motor vehicle.

4. Device according to claim 2 , characterized in that the first means for charging the storage capacitor (Cs) comprise a fourth switch (S 4 ) and an operational amplifier (AO), of which the output is connected to the negative input terminal, such that the charge of the storage capacitor (Cs) is equal to the charge of the intermediate capacitor (C INT ).

5. Device according to claim 1 , characterized in that the means for detecting comprise:
a second generator of a second supply voltage (Vcc),
second means for charging the storage capacitor (Cs) from the second supply voltage (Vcc),
means for measuring the storage voltage (Vs),
means for measuring a period (t) of charging of the storage capacitor (Cs) between an initial determined moment and a moment at which the storage voltage (Vs) has reached a predetermined storage threshold (V TH ), and,
means for comparing the measured period (t) with a reference period (Tref) so as to detect the presence of a user for the unlocking of an access point to the motor vehicle.

6. Device according to claim 5 , characterized in that the first means for charging the storage capacitor (Cs) comprise a fourth switch (S 4 ) and an operational amplifier (AO), of which the output is connected to the negative input terminal, such that the charge of the storage capacitor (Cs) is equal to the charge of the intermediate capacitor (C INT ).

7. Device according to claim 5 , characterized in that the second charging means comprise a third switch (S 3 ) arranged in series with a load resistor (Rc).

8. Device according to claim 7 , characterized in that the first means for charging the storage capacitor (Cs) comprise a fourth switch (S 4 ) and an operational amplifier (AO), of which the output is connected to the negative input terminal, such that the charge of the storage capacitor (Cs) is equal to the charge of the intermediate capacitor (C INT ).

9. Device according to claim 7 , characterized in that the capacitance variation (ΔCx) of the detection capacitor (Cx) is given by:

Δ
⁢

⁢

C
X

=

Th
·
Δ

⁢

⁢
t

R
C

·
x

·

C
INT

C
S

·

V
CC

V
X

where Th is the variation of the number of intervals Δt included within the measured period (t) in accordance with the variation of the detection capacitor.

10. Device according to claim 9 , characterized in that the first means for charging the storage capacitor (Cs) comprise a fourth switch (S 4 ) and an operational amplifier (AO), of which the output is connected to the negative input terminal, such that the charge of the storage capacitor (Cs) is equal to the charge of the intermediate capacitor (C INT ).

11. Device according to claim 9 , characterized in that

C
INT

C
S

·

V
CC

V
X

≤
1.

12. Device according to claim 11 , characterized in that the first means for charging the storage capacitor (Cs) comprise a fourth switch (S 4 ) and an operational amplifier (AO), of which the output is connected to the negative input terminal, such that the charge of the storage capacitor (Cs) is equal to the charge of the intermediate capacitor (C INT ).

13. Device according to claim 1 , characterized in that the first means for charging the storage capacitor (Cs) comprise a fourth switch (S 4 ) and an operational amplifier (AO), of which the output is connected to the negative input terminal, such that the charge of the storage capacitor (Cs) is equal to the charge of the intermediate capacitor (C INT ).

14. Motor vehicle characterized in that it comprises a device according

Assignees

• Hourne Xavier
• Ung Monirat
• Galaup Julien
• Continental Automotive France
• Continental Automotive Gmbh

Inventors

• Hourne Xavier
• Ung Monirat
• Galaup Julien

Classifications

• H03K17/955 Primary

  using a capacitive detector · CPC title

• G07C2009/00793

  by Hertzian waves · CPC title

• G07C9/00309

  operated with bidirectional data transmission between data carrier and locks · CPC title

• G07C2209/65

  using means for sensing the user's hand · CPC title