Acceleration sensor, especially duplex acceleration sensor, arrangement and method for detecting a loss of adhesion of a vehicle tire

Abstract

The invention relates to an acceleration sensor, especially a duplex acceleration sensor, an arrangement and a method for detecting a loss of road grip of a vehicle wheel (3). The acceleration sensor comprises a tube (5) having a longitudinal axis forming a circular arc segment, and two closed ends. A mass (15; 315) is arranged inside the tube (5) such that is able to move inside the tube (5) in the longitudinal direction thereof. A magnet arrangement (17; 203; 205; 317) is designed to counteract, by way of a magnetic force exerted on the mass (15; 315), a movement of said mass (15; 315) from an idle position (25), and a read-out unit (608) is designed to detect a movement of said mass (15) from the idle position (25).

Claims

1. A method for detecting a loss of road grip of a vehicle wheel, comprising the steps of: a) automatically verifying a loss of road grip of the vehicle wheel, by means of an acceleration sensor, in response to detection of a critical driving situation caused by rain or low temperature detected by a detector comprising a rain sensor or a temperature sensor, wherein the verifying is executed by way of: i. a change in acceleration of the vehicle wheel by means of a vehicle brake in order to cause a minor loss of road grip, comprising effecting an acceleration of one or several of the vehicle wheels automatically at regular time intervals upon the detection of the critical driving situation caused by rain or low temperature, and ii. the detection of the loss of road grip during the change in acceleration by the means of the acceleration sensor; and b) informing a vehicle driver of the verified loss of road grip by a warning unit, wherein the verifying is an active test in which one or several of the vehicle wheels are accelerated in order to detect whether or not a new loss of road grip occurs.

2. A method for detecting a loss of road grip of a vehicle wheel, comprising the steps of: a) changing acceleration of the vehicle wheel using a vehicle brake in order to cause a minor loss of road grip, when an activation element is activated by a driver and upon a detection by a detector of a critical driving situation caused by rain or low temperature, wherein the detector comprises a rain sensor or a temperature sensor; and b) during the change in acceleration, detecting a loss of road grip of the vehicle wheel by means of an acceleration sensor, wherein the activation element is designed as a push button which is arranged on a dash-board of a vehicle cockpit and can be pushed by a vehicle driver if the driver wants to test the road grip of one or several vehicle wheels on a road surface.

3. The method in accordance with claim 2, wherein the changing acceleration of the vehicle wheel is performed by several subsequent accelerations and/or decelerations of varying and/or increasing intensity.

4. An arrangement for detecting a loss of road grip of at least one vehicle wheel, the arrangement comprising: a detector comprising a rain sensor or a temperature sensor; a first acceleration sensor; a warning unit coupled to the first acceleration sensor, the warning unit designed to inform a vehicle driver of the loss of road grip if a loss of road grip is detected by the first acceleration sensor; and a control unit designed to control a vehicle brake in order to effect an acceleration of the at least one vehicle wheel, in order to cause a minor loss of road grip which serves to determine a degree of the loss of road grip, the arrangement further comprising: an activation element designed to send, upon activation by a vehicle driver, an acceleration signal to the control unit in order to effect an acceleration of at least one vehicle wheel, wherein the control unit is configured to effect the acceleration of one or several of the vehicle wheels upon a detection by the detector of a critical driving situation caused by rain or low temperatures, wherein the activation element is designed as a push button which is arranged on a dashboard of a vehicle cockpit and can be pushed by a vehicle driver if the vehicle driver wants to test the road grip of one or several vehicle wheels on a road surface.

5. The arrangement in accordance with claim 4: further comprising a second acceleration sensor opposite to the first acceleration sensor, the second acceleration sensor being a duplex acceleration sensor.

6. An arrangement for detecting a loss of road grip of at least one vehicle wheel, the arrangement comprising: a detector comprising a rain sensor or a temperature sensor; a first acceleration sensor; a warning unit coupled to the first acceleration sensor, the warning unit designed to inform a vehicle driver of the loss of road grip if a loss of road grip is detected by the first acceleration sensor; and a control unit designed to control a vehicle brake in order to effect an acceleration of the at least one vehicle wheel, in order to cause a minor loss of road grip which serves to determine a degree of the loss of road grip, wherein the control unit is configured to effect at regular time intervals the acceleration of one or several of the vehicle wheels automatically upon a detection by the detector of a critical driving situation caused by rain or low temperatures.

7. The arrangement in accordance with claim 6: further comprising a second acceleration sensor opposite to the first acceleration sensor, the second acceleration sensor being a duplex acceleration sensor.

Description

(1) Some preferred embodiments of the invention are, by way of example, described by means of the attached figures. The following is shown in

(2) FIG. 1: a schematic illustration of a first exemplary embodiment of an acceleration sensor according to the invention,

(3) FIG. 2: a schematic illustration of a second exemplary embodiment of an acceleration sensor according to the invention,

(4) FIG. 3: a schematic illustration of a third exemplary embodiment of an acceleration sensor according to the invention,

(5) FIG. 4: a schematic illustration of a fourth exemplary embodiment of an acceleration sensor accosting to the invention,

(6) FIG. 5: a schematic illustration of a fifth exemplary embodiment of an acceleration sensor according to the invention, and

(7) FIG. 6: a schematic illustration of an arrangement according to the invention.

(8) The illustrations of the schematically shown exemplary embodiments in FIGS. 1 to 6 are not true to scale. Especially the relation between the size of the acceleration sensor and the size of the vehicle wheel is not true to scale: when implemented in practice, the acceleration sensor would be significantly smaller than shown in the Figures.

(9) FIG. 1 schematically shows an acceleration sensor 1 when installed at a vehicle wheel 3. The acceleration sensor 1 is a part of an arrangement 601 shown in FIG. 6 for detecting a loss of road grip of the vehicle wheel 3.

(10) The acceleration sensor 1 comprises a tube 5 with a longitudinal axis which forms a circular arc segment. The tube 5 has closed ends 7 and 9. A contact surface 11 or respectively 13, which faces towards the inside of the tube 5, is respectively arranged at the ends 7 or respectively 9.

(11) A ball 15 forming a mass consisting of steel is arranged inside the tube 5 such that it is able to move inside the said tube 5 in the longitudinal direction thereof. The tube 5 is filled with a fluid not shown in the illustration. A coil 17 encloses the tube by means of a coil wire 19 wound several times around the tube. The coil 17 is provided with power via two electrical contacts 21 and 23 in order to exert an attracting magnetic force on the ball 15 and to counteract a movement of the ball 15 in the rotational direction 27 of the vehicle wheel 3 from an Idle position 25.

(12) A control unit 603 shown in FIG. 8 controls a power supply 613 of the coil 17. In this context, a positive acceleration of the vehicle wheel 3 in the rotational direction 27 through a vehicle engine is taken into account. This means that if the vehicle wheel 3 is accelerated in the rotational direction 27 through an increase of the torque of the vehicle engine, the control unit 603 will effect that the coil exerts an increased force on the ball 15 so that the latter remains in the idle position 25 (unless other accelerations effects occur). In addition, a negative acceleration of the vehicle wheel 3 against the rotational direction 27 through the vehicle brakes is taken into account. This means that if the vehicle wheel 3 is slowed down against the rotational direction 27 by the vehicle brake, the control unit 603 will effect that the coil exerts an increased force on the ball 15 so that the latter remains in the idle position. Through the compensation of positive accelerations (engine) and negative accelerations (brakes), a loss of road grip of the vehicle wheel 3 can be determined based on a movement of the ball 15 from the idle position 25. If, for example, the vehicle wheel 3 spins due to a loss of road grip, the ball 15 will, from the view direction of FIG. 1, move from the idle position 25 to the left. If the vehicle wheel 3 is locking up due to a loss of road grip when the vehicle is braking, the ball 15 will, from the view direction of FIG. 1, move to the right.

(13) In addition to the acceleration sensor 1, a second duplex acceleration sensor 29, which, in terms of function, has an identical design to the first acceleration sensor 1, is arranged in the vehicle wheel 3. In relation to the center 31 of the circular arc segment, the second acceleration sensor 29 is arranged opposite to the acceleration sensor 1. In other words, the second acceleration sensor 29 is arranged in the rotational direction 27, offset from the first acceleration sensor 1 by 180.

(14) In addition, FIG. 6 shows an evaluation unit 605 with evaluation electronics 607 and a read-out unit 608. The read-out unit 608 comprises the contact surfaces 11 and 13 shown in FIG. 1. A communication between the evaluation electronics 607 and the read-out unit 608 is wireless. The read-out unit 608 detects when the ball 15 touches one of the contact surfaces 11 or 13. A contact between the ball 15 and one of the contact surfaces 11 or 13 represents a loss of road grip. This loss of road grip is optically indicated to a driver 609 by means of a display 611. The control unit 603 communicates wirelessly with the power supply 613 in order to control the force the coil 17 exerts on the ball 15.

(15) An activation element 617 in the form of a push button is arranged at a vehicle steering wheel 615. If the vehicle driver 609 activates the activation element 617, an acceleration signal will be sent to a control unit 619. The control unit 619 is designed to control the vehicle engine and/or the vehicle brake in order to effect a positive or negative acceleration of the vehicle wheel 3.

(16) The arrangement shown in FIG. 6 can be used to realize an exemplary realization of a method according to the invention for detecting a loss of road grip of a vehicle wheel in accordance with the fourth aspect of the invention. In a first method step A, it is tested at regular intervals by means of an acceleration sensor 1 arranged at the vehicle tire 3 whether or not there is a loss of road grip. As soon as a loss of road grip is detected, this loss of road grip is verified in a method step B. The verification of the loss of road grip comprises the following steps: In a first method step i., the vehicle wheel 3 is accelerated by means of the vehicle brake and/or the vehicle engine. The acceleration is effected by means of the control unit 619. In another method step ii., it is detected by means of the acceleration sensor 1, whether or not there is a loss of road grip during the acceleration. In a method step C, the vehicle driver 609 is informed of the verified loss of road grip by means of the display 611.

(17) In addition, the arrangement shown in FIG. 6 can be used to realize a second exemplary realization of a method according to the invention for detecting a loss of road grip of a vehicle wheel 3 in accordance with the fifth aspect of the invention. In a first method step AA, the activation element 617 is activated by the vehicle driver 609. Once activated, the activation element 617 sends an acceleration signal to the control unit 619, which effects an acceleration of the vehicle wheel 3. Thus, in a method step BB, the vehicle wheel 3 is accelerated by means of the vehicle brake and/or the vehicle engine. During the acceleration, a loss of road grip of the vehicle wheel 3 is detected by means of the acceleration sensor 1 in a method step CC.

(18) The acceleration in accordance with method step BB is executed by means of several subsequent accelerations with increasing intensity. First of all, the vehicle wheel is slightly accelerated. If no loss of road grip is detected during this minor acceleration, the vehicle wheel will be accelerated once again with an increased intensity. The intensity of the acceleration is increased with each new acceleration until a loss of road grip is detected. Based on the intensity of the acceleration at which a loss of road grip is detected, using empirical values, a degree of road grip can be determined. In a method step DD, the degree of road grip can be indicated to the vehicle driver 609 by means of the display 611.

(19) FIG. 2 schematically shows an acceleration sensor 201 when installed at a vehicle wheel 3. The design of the acceleration sensor 201 is similar to the one of the acceleration sensor 1 shown in FIG. 1. Identical elements and elements with the same function are marked by the same reference number. Contrary to the acceleration sensor 1 shown in FIG. 1, the acceleration sensor 201 comprises two coils 203 and 205, which respectively exert a repelling magnetic form on the ball 15 in order to counteract a movement of the ball 15 from the idle position.

(20) FIG. 3 schematically shows an acceleration sensor 301 when installed at a vehicle wheel 3. The design of the acceleration sensor 301 is similar to the one of the acceleration sensor 1 shown in FIG. 1. Identical elements and elements with the same function are marked by the same reference number. Contrary to the acceleration sensor 1 shown in FIG. 1, the acceleration sensor 301 comprises several balls 315. The coil 317 exerts an attracting force on the balls 315 in order to counteract a movement of the balls 315 from the idle position.

(21) FIG. 4 schematically shows an acceleration sensor 401 when installed at a vehicle wheel 3. The acceleration sensor 401 comprises a chamber 403 in which an admiralty anchor-shaped mass 405 is suspended by means of a straight rod 407 and a circular arc-shaped segment 409. The suspension is located at a first end of the rod 407, wherein, starting from a second end of the rod, the circular arc shaped segment 409 extends in two directions transversely to the longitudinal axis of the rod 407. A coil spring 411 or respectively 413 forms respectively a connection between the rod 40 and an inside wall 415 or respectively 417. The coil springs 411 and 413 counteract a movement of the mass 406 from an idle position 425. The chamber 403 respectively composes a contact surface 419 or respectively 421, which an end 427 or respectively 429 of the segment 409 will touch if the mass 405 moves from the idle position 425. By means of a read-out unit, which is not shown in the figure, this contact of an end 427 or respectively 429 and a contact surface 419 or respectively 421 is detected. A second acceleration sensor 431, which, in terms of function, has the same design as the first acceleration sensor 401, is arranged in the rotational direction 433, offset from the first acceleration sensor 401 by 180.

(22) FIG. 5 schematically shows an acceleration sensor 501 when installed at a vehicle wheel 3. The acceleration sensor 501 is designed similarly to the acceleration sensor 401. Identical elements and elements with the same function are marked by the same reference number. Contrary to the acceleration sensor 401 shown in FIG. 4, the mass 505, which is arranged in a pendulum-like manner inside the chamber 403, consists of a rod 407 and a ball-shaped head mass 509. The rod 407 is suspended at a first end in such a way that it can swing. The head mass 509 is arranged at a second end of the rod. In addition, the acceleration sensor 501 comprises several contact surfaces 519. Depending on how far the mass 505 swings out of the idle position 425, the ball shaped mass 509 will touch one of several contact surfaces 519. A read-out unit, which is not shown in the figure, detects which one of the contact surfaces 519 the ball 509 touches. Thus, the degree of the movement of the mass from the idle position 426 is determined.

REFERENCE NUMBERS

(23) 1 Acceleration sensor

(24) 3 Vehicle wheel

(25) 5 Tube

(26) 7, 9 End

(27) 11, 13 Contact surface

(28) 15 Ball

(29) 17 Coil

(30) 19 Coil wire

(31) 21, 23 Contacts

(32) 25 idle position

(33) 27 Rotational direction

(34) 29 Second acceleration sensor (duplex acceleration sensor)

(35) 31 Center

(36) 201 Acceleration sensor

(37) 203, 205 Coils

(38) 301 Acceleration sensor

(39) 315 Balls

(40) 317 Coil

(41) 401 Acceleration sensor

(42) 403 Chamber

(43) 405 Mass

(44) 407 Rod

(45) 400 Segment

(46) 411, 413 Coil spring

(47) 415, 417 Inside wall

(48) 419, 421 Contact surface

(49) 425 Idle position

(50) 427, 429 End

(51) 431 Second acceleration sensor

(52) 433 Rotational direction

(53) 501 Acceleration sensor

(54) 505 Mass

(55) 509 Head mass

(56) 519 Contact surfaces

(57) 601 Arrangement

(58) 603 Control unit

(59) 605 Evaluation unit

(60) 607 Evaluation electronics

(61) 608 Read-out unit

(62) 609 Vehicle driver

(63) 611 Display

(64) 613 Power supply

(65) 615 Vehicle steering wheel

(66) 617 Activation element

(67) 619 Control unit