Method and system for detecting an object caught in the path of an automotive window using a piezoelectric torque sensing device

BACKGROUND OF THE INVENTION

The invention relates to a method and system for detecting an object caught in the path of an automotive window.

Many of the automotive vehicles today have electronically controlled windows and may even have electronically controlled sun/moon roofs. These systems provide the operator with ease in opening and closing the windows. However, if the operator is distracted while closing the window, it is possible for an object, such as an arm, hand or finger, to be caught between the window and the window frame of the automotive window.

A power window system consists of a regulator coupled to the window and driven by an electric drive motor. The motor typically comprises an output shaft connected to a worm associated with a gear wheel. The gear wheel is connected to an output member coupled to the regulator. Thus, as the motor rotates, the worm rotates, causing the gear wheel to also rotate. Rotation of the gear wheel results in the regulator being driven upward and downward.

One known technique for sensing/detecting the presence of an object caught between a window and its frame when the window is closed utilizes an elastically deformable damper coupled between the gear wheel and the output member. The elastically deformable member permits angular displacement between the wheel and the output member in response to a resistive torque being applied to the output member. The angular displacement is then sensed using a pair of angular position encoders, wherein one encoder is associated with the gear wheel and the other encoder is associated with the output member. If an object is present, a resistive torque is applied to the output member causing the damper to deform and generating an angular displacement between the output member and the gear wheel. This technique, however, has several challenging technical issues concerning the dampers. As examples, the elastic compliance must provide linearity throughout the entire range of torque, the elastic compliance must allow angular displacements large enough to be detected by the encoders, and the elastic stiffness changes as the damper ages.

Thus, there exists a need for a torque sensing device for sensing a torque associated with a resistive force applied to a power window that overcomes the problems encountered by the prior art.

SUMMARY OF THE INVENTION

A system for detecting the presence of an object caught between an automotive window and its respective frame is disclosed. The window is mounted on a regulator that is driven upward and downward by an electric drive motor controlled by a control circuit. A sensor is mounted on the drive motor for sensing a resistive torque applied to the regulator. The sensor generates a voltage signal having a value proportional to the sensed resistive torque.

A rotor shaft extends from the drive motor and has a cylindrical worm sleeve encircling it. The worm sleeve is formed with grooves. A grooved gear wheel is associated with the sleeve, and rotates in response to rotation of the worm sleeve. An output member extends from the gear wheel and is coupled to the regulator for moving the window upward and downward. A sensor comprises a piezoelectric layer mounted on the rotor shaft so that it is sandwiched between the worm sleeve and the rotor shaft when the worm sleeve is inserted onto the rotor shaft. The piezoelectric layer senses a pressure in response to the resistive torque being applied to the worm sleeve via the regulator.

Some rotating electric coupling transmits a signal from the piezoelectric layer to a control. In one embodiment, a pair of secondary brushes are mounted on a secondary commutator to transmit the voltage signal generated by the piezoelectric layer. The signal is received by a corresponding pair of secondary contacts connected to the control circuit. The control circuit determines whether or not an object is caught between the window and its respective frame based on the voltage signal. If an object is present, the value of the voltage signal exceeds a predetermined value. In response to this determination, the control circuit either stops or reverses the direction of the drive motor. Other rotating electric couplings may be used.

These and other features of the present invention can be understood from the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a schematic block diagram of a power window system incorporating the torque-sensing device of the present invention;

FIG. 2

is a perspective partial view of the torque-sensing device of the present invention; and

FIG. 3

shows forces on the inventive sensor.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1

shows a power window system

10

incorporating the torque-sensing device of the present invention. An automotive vehicle has a door

12

and a window frame

14

defining a window opening

16

. While a side window is shown, the term “window” as used in this application also extends to rear windows, moon roofs, sun roofs, or other vehicle closure components.

The door

12

is equipped with a window glass

18

movable elevationally within the window opening

16

and a drive motor

20

linked with a regulator

22

for driving the window glass

18

upward and downward. Microprocessor, or control circuit,

24

controls the drive motor

20

via motor drive circuit

26

in response to signals from switch

28

that commands upward/downward movement of the window glass

18

.

Turning now to

FIG. 2

, there is shown a perspective partial view of the torque-sensing device of the present invention. The device is incorporated into the drive motor, denoted generally by

20

. Drive motor

20

includes a motor portion

30

consisting of typical components (not shown), such as permanent magnets, commutator brush, etc. The drive motor

20

further includes an output rotor shaft

32

and a cylindrical worm sleeve

34

that is slidably mounted onto shaft

32

. Worm sleeve

34

, thus, rotates as rotor shaft

32

rotates causing gear wheel

36

to also rotate. Gear wheel

36

has an output member

38

that further rotates as gear wheel

36

rotates. Output member

38

is coupled to regulator

22

so that as output member

38

rotates, regulator

22

moves upward and downward accordingly. The structure of gear wheel

36

and output member

28

is shown somewhat schematically.

In order to sense any resistive force/torque applied to the regulator

22

due to an obstruction between the window

18

and frame

14

, a piezoelectric layer

40

is mounted on an end face of a hub portion

39

of the rotor

32

that comes in contact with a surface of the worm sleeve

34

so that it is sandwiched therebetween. Thus, as the torque resisting rotation of worm sleeve

34

changes, this changing torque is sensed via a proportional voltage signal generated by piezoelectric layer

40

.

The rotor shaft is formed with a semicircular hub portion

39

having outer end faces that receive the piezoelectric layer

40

. Worm sleeve

34

has a bore

35

received on shaft

32

. A hub portion

37

of the worm sleeve

34

has outer end faces that face the outer end faces of hub portion

39

. The piezoelectric layer

40

is thus caught between the end faces.

As shown in

FIG. 3

, when shaft

32

is turned by motor

30

, sleeve

34

is turned Sleeve

34

can be fixed to be driven by shaft

32

, such as by splines. When sleeve

34

is driven, a resistance torque force F is transmitted back to the shaft

32

. The piezoelectric

40

senses the magnitude of the force F. If an obstruction is in the way of the window, the resistance torque increases, and force F increases.

The voltage generated by the piezoelectric layer

40

is sensed via a secondary commutator/brush assembly

42

included in the drive motor

20

. The secondary commutator

42

has a pair of brushes

44

that are electrically connected to piezoelectric layer

40

. The secondary brushes

44

rotatably come into contact with secondary contacts

46

that transmit the signal from the piezoelectric layer

40

to the control circuit

24

. Other rotating electrical coupling may be used.

In operation, the drive motor rotates according to control signals generated by control circuit

24

in response to switch

28

. If no resistive torque is applied to the output member

38

via the regulator

22

, then the worm sleeve

34

is not pressured against piezoelectric layer

40

and rotor shaft

32

. On the other hand, if a resistive torque is applied to the output member

38

, the worm sleeve

34

is pressured against the rotor shaft

32

. Piezoelectric layer

40

senses this pressure and generates a voltage signal for receipt by brushes

44

, which in turn transmit this signal to the control circuit

24

via the contact members

46

. This voltage is compared to a reference voltage. A particular voltage level is associated with an indication an obstruction is in the path of the window. If control

24

senses that this level is pass, then control circuit

24

commands the drive motor

20

to either stop or reverse its direction.

Preferred embodiments have been disclosed. However, a worker in this art would recognize that modifications would come within the scope of this invention. Thus, the following claims should be studied to determine the scope and content of this invention