Machine element or mechanism – Control lever and linkage systems – Foot operated
Reexamination Certificate
1999-10-14
2001-08-21
Green, Mary Ann (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Foot operated
C074S560000
Reexamination Certificate
active
06276229
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a gas-pedal module having a gas pedal which is mounted in a housing and can be actuated, counter to the force of a restoring spring, with pedal-force-dependent hysteresis, and having a pedal-position sensor which produces an electric signal corresponding to the pedal position.
In gas pedals for motor vehicles, use is being made increasingly frequently of so-called “drive-by-wire” systems, in the case of which the gas pedal is no longer connected to the throttle via a Bowden wire, as has been the case up until now, but rather a sensor produces an electric output signal which corresponds to the gas-pedal position and passes, via lines, to an engine control system, which activates the throttle via an electric actuating motor in dependence on the signals.
From the Bowden wires which have usually been used up until now, the vehicle drivers are accustomed, during actuation of the gas pedal, to a force hysteresis which is derived from the frictional forces acting in the Bowden wire. These frictional forces set an increased resistance against the pressing-down action of the pedal and, when a certain gas-pedal position is being held, relieve the driver's foot of the restoring forces of the restoring spring. The counter pressure, when the gas pedal is pressed down, allows more precise positioning of the gas pedal, while the foot being relieved when a gas-pedal position is being held improves comfort.
With the “drive-by-wire” systems, attempts were made to maintain these desirable characteristics of the gas pedal, for which purpose a simulation of the properties of a Bowden wire with its restoring spring was necessary.
In order to simulate the hysteresis, use is usually made of direction-dependent frictional elements, as are outlined, for example, in DE 195 17 172. This document also discloses the conventional play-free mounting of the gas pedal in a housing. Since the mounting of the gas-pedal lever, on the one hand, has to be precise but also, at the same time, has to absorb very high pedal forces, a particularly high-quality, play-free mounting (for example needle bearings) has to be provided in order to avoid the possible occurrence of jamming. The costs of such a gas-pedal module are thus considerable.
BRIEF SUMMARY OF THE INVENTION
The object of the invention is to provide a gas-pedal module which can absorb high pedal forces and nevertheless does not involve the risk of the gas pedal jamming.
The object is achieved according to the invention in that the gas pedal is mounted in a floating manner in a bearing element which has play in the upward direction.
The bearing element, which is at least half-open, allows precise mounting of the gas pedal on the one hand and on the other hand, by virtue of the possibility of yielding in the upward direction, reliably prevents possible jamming of the gas pedal in its bearing location. In this case, a very small allowance for movement is sufficient in order to eliminate the risk of jamming reliably.
The solution according to the invention manages with extremely simple bearing elements, for example in the form of a half-shell.
The spring element is preferably a helical spring which, via a lever arm, produces a restoring moment which is directed counter to the moment provided by the actuating force about the pivot axis of the gas pedal. In this case, the force which is produced by the helical spring is preferably directed essentially counter to the bearing force of the gas pedal in the bearing element.
Consequently, both the actuating force and the restoring force of the spring are supported in the bearing element, this resulting in an increased friction moment when the pedal is pressed down, and thus in a certain hysteresis.
In order to achieve certain hysteresis characteristics, it is advantageous if the contact surface between the bearing element and a circumferential surface of the gas pedal is designed as a friction pairing with a certain coefficient of friction.
Such a configuration of the bearing element and of the mounted surface of the gas pedal makes it possible to achieve a hysteresis of the desired magnitude without separate components being used. In comparison with conventional designs with rockers, spring elements, frictional elements and damping elements, the mounting of which involves very high outlay in part, this constitutes a considerably simplification in design, which allows the production costs of gas-pedal modules to be reduced further without the mechanical properties being compromised.
It is also possible for the contact surface between the bearing element and the circumferential surface of the gas pedal to be subdivided into two circumferential-segment regions, which form two radial supporting locations. It is particularly advantageous here if at least one radial supporting location can be adjusted in the circumferential direction in relation to the circumferential surface of the gas pedal. This allows the characteristics of the gas-pedal module to be changed simply by adjusting a supporting location. This makes it possible to achieve simple adaptation of the frictional hysteresis, to a respective vehicle type, which corresponds to the character and the image of the vehicle. The development of a single gas-pedal module with a pedal housing and optimum friction-lining pairing is sufficient here, which makes a considerable contribution to the reduction of development costs. The force hysteresis is determined here from the following factors: coefficient of friction, geometry and normal force.
The gas-pedal travel is preferably limited in an idling position by a first stop and in the full-load position by a second stop. The travel between these two precisely defined positions can be initiated in a desired manner by the gas-pedal sensor and transmitted to the engine electronics.
Furthermore, in the case of vehicles with automatic transmission, it is desirable to provide a kick down position for the gas pedal.
For a gas-pedal module according to the invention, this may be realized such that, in the case of further-increased pedal pressure in the full-throttle position, the second stop forms a second pivot axis of the gas pedal, the gas pedal lifting off from the bearing element and passing into a kick down position. The changed pivot axis of the gas pedal results in a characteristic signal deviation of the gas-pedal sensor, it being possible for said signal deviation to be clearly assigned to the kick down position.
The level of the change in force which is necessary for achieving the kick down position can be defined in a customer-specific manner such that the second stop, for defining the necessary pedal pressure, is arranged at a certain distance from the bearing element. A third stop expediently serves for limiting the gas-pedal travel in the kick down position.
For pedal-position sensors, use is made nowadays of usually series-produced potentiometers with a slider fixed on the axis of rotation of the pedal arm. With the floating mounting of the gas pedal, this may result in difficulties in certain circumstances since radial movements of the slider on the housing-mounted resistive tracks may result in a signal deviation which cannot be distinguished from a rotary movement. The problem may be eliminated, for example, in that, instead of the potentiometers which have been customary up until now, use is made of sensors which operate with magneto resistive action and react exclusively to the orientation of the magnetic field and thus do not generate any signal deviations in the case of radial movements.
It is also possible for the gas-pedal module according to the invention to operate with potentiometers. For this purpose, it is provided that at least one potentiometer is mounted separately from the gas pedal and can be actuated via elements with play compensation separately in mechanical terms from the gas pedal. The play compensation for mechanical separation is necessary in order to compensate for any possible displacements of the gas pedal in relation to the bearin
Gohring Frank
Wendling Armin
Green Mary Ann
Mannesmann VDO AG
Mayer Brown & Platt
Speer Richard A.
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