Measuring and testing – Speed – velocity – or acceleration
Reexamination Certificate
1997-03-06
2001-09-04
Moller, Richard A. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
C180S197000, C303S121000, C361S236000, C477S020000, C477S040000, C477S183000
Reexamination Certificate
active
06282954
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is based on a system for changing a signal representing the rotational speed of at least one, wheel of a motor vehicle. For the closed-loop or open-loop control of the braking force, drive power, and/or dynamics of motion of a motor vehicle, it is known that the rotational speeds of the wheels of the vehicle can be measured. The state of the art provides various methods (e.g., Hall or magnetoresistive sensors) for this purpose. In addition, it is known that the point at which the brake lining of a vehicle brake becomes worn out can be determined by, for example, embedding contact pins a certain depth below the surface of the brake lining. When the brake lining has been worn down to this depth, the pins trigger a contact.
Active sensors for use in open-loop or closed-loop antilock, drive slip, engine, and transmission control systems in motor vehicles are described in, for example, the article “Integrierte Hall-Effekt-Sensoren zur Positions-und Drehzahlerkennung”, eletronik industrie, Vol. 7, pp. 29-31, 1995. In a two-wire system, sensors of this type supply two current levels, which are converted by a precision resistor into two voltage levels in a corresponding control device.
In addition to the Hall-effect sensors mentioned above, it is also possible to use magnetoresistive sensors to detect rotational speeds. This is known from, for example, the article “Neue, Alternative Lösungen für Drehzahlsensoren im Kraftfahrzeug auf magnetoresisitiver Basis”, VDI-Berichte, No. 509, 1984.
A special shared device for detecting brake lining wear and the rotational speed of a wheel is described In DE-C2 26 06 012 (U.S. Pat. No. 4,076,440). For this purpose, the detected brake lining wear and the wheel speed detected by means of an inductive sensor are sent over a common signal line to an evaluation unit. This is achieved in that the wheel speed sensor is entirely or partially short-circuited in reaction to the detected amount of brake lining wear.
To detect the rotational speed of the wheel and the brake lining wear at the wheel brake, other systems, such as those described in DE-C 43 22 440, require at least two signal lines between the wheel unit and the evaluation unit.
In regard to the detection of rotational speed described above, it is known that the air gap between the rotating toothed wheel rim and the actual sensor element has a considerable effect on the quality of the rotational speed signal. In reference to this point, see, for example, DE-OS 32 01 811, for example.
In addition, in the case of systems to help the driver get the vehicle started (so-called “hill holders”), for example, information on the rotational direction of the wheels is also required. Here it is especially necessary to known if the vehicle is moving backwards. See, for example, DE-OS 35 10 651 on this point.
The information cited above and other types of data (such as data on the degree of brake lining wear, the size of the air gap, and the direction of rotation) are usually detected close to the wheel and evaluated in a control unit located some distance away from the wheel. The information must therefore be transmitted to the control unit.
In the case of an engine (internal combustion engine or electric motor), it is known that the rpm's of the engine can be detected by means of inductive, magnetoresistive, or Hall sensors.
The task of the present invention is to provide means for transmitting the rotational speed signal and additional information in the simplest possible, reliable manner.
BRIEF SUMMARY OF THE INVENTION
The invention is based on a system for changing a signal representing a rotational movement with a first means for generating a first signal representing the rotational movement and a second means for generating at least one second signal representing an additional type of information. Such information can consist in, for example, the determination of the direction in which rotation is occurring and/or of the size of the above-cited air gap and/or of the degree of the brake lining wear in at least one brake of the vehicle. The air gap can be determined on the basis of the amplitude of a signal associated with the rotational speed signal. A third means is also provided, by means of which the first signal (speed signal) can be changed as a function of the second signal (direction of rotation, air gap, and/or brake lining wear).
The core of the invention now consists in that the first means is designed in such a way that the first signal (rotational speed signal) assumes at least two first current values and/or two first voltage values. In addition, the third means according to the invention is designed in such a way that, to change the first signal (rotational speed signal), at least one of the first current values and/or voltage values can be changed for at least a certain period of time to at least one second current value and/or voltage value as a function of the second signal (direction of rotation, air gap, and/or brake lining wear).
The invention offers the advantage that, in a simple and reliable manner, the additional information concerning direction of rotation, air gap, brake lining wear, and/or other operating conditions of the vehicle, of the vehicle brake, and/or of the vehicle engine can be transmitted over the output line of the rotational speed sensor. As a result, it is possible to eliminate, for example, the above-mentioned second signal line for the exclusive transmission of the additional information.
Another advantage of the invention consists in that the speed sensor and the detector of the above-cited additional information form a compact unit.
The system according to the invention is used advantageously in a motor vehicle, where the first signal can represent the rotational speed of a vehicle wheel; the rpm's of the vehicle's engine, which can be either a gasoline or diesel engine or an electric motor; and/or the rpm's of a shaft operationally connected to the vehicle's transmission.
In a variant, the invention is used in a wheel speed sensor unit, such as that used in conjunction with an antilock, drive slip, and/or automatic driving dynamics control system. Here the wheel speed information can be sent together with at least one of the additional types of information cited above (direction of rotation, air gap, and/or brake lining wear) from a sensor unit located close to the wheel to a control unit located some distance away from the wheel in a low-cost and reliable manner.
Another variant of the invention pertains to the possibility of using the system according to the invention to detect the rpm's of the engine. In this application, too, the engine rpm information can be sent together with at least one of the above-mentioned additional types of information from a sensor unit near the engine to a control unit some distance away from the engine in a low-cost and reliable manner. The additional information to be transmitted in this case includes in particular information on the backwards rotation of the engine. An internal combustion engine turns backwards primarily when the engine is being started and when it is stalling. With the systems being used at present, so-called intake manifold “bangs” can occur. An engine control unit with conventional speed sensors (which do not recognize backwards rotation) continues to receive a speed signal when the engine is rotating backwards, but it cannot tell that the engine is turning in the wrong direction. Because the engine is turning in the wrong direction, the ignition angle will be off by a wide margin the next time an injection or ignition is initiated. If the fuel intake valve is open when ignition occurs, the above-mentioned intake manifold “bangs” will occur. These bangs in the intake manifold can lead to the destruction of the following components:
the idling regulator,
the throttle valve,
the intake manifold itself, and
possibly the pressure gauge or the known hot-film air mass flow meter.
If it is possible to detect when the engine is turning ba
Lehner Michael
Ott Karl
Schneider Thomas
Walther Michael
Fulbright & Jaworski LLP
Moller Richard A.
Robert & Bosch GmbH
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