Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
1999-04-22
2001-10-23
Schwartz, Christopher P. (Department: 3613)
Brakes
Wheel
Axially movable brake element or housing therefor
Reexamination Certificate
active
06305508
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an electromechanical wheel brake device set forth hereinafter.
A wheel brake device of this kind has been disclosed by DE 196 31 592 A1. The known wheel brake device has an electric motor which, in order to actuate the wheel brake device by way of a worm gear, i.e. an angular gear, drives a nut of a screw link actuator to rotate. A spindle of the screw link actuator presses a frictional brake lining against a brake body and thus produces a brake force or a brake moment. The known wheel brake device is embodied as a disk brake with a floating caliper; the electric motor, the worm gear, and the screw link actuator are accommodated in the floating caliper. The brake body is a brake disk that is connected in a rotationally fixed manner to a vehicle wheel. The screw link actuator is a rotation/translation conversion gear that converts a rotating drive motion of the angular gear into a translational motion for pressing the frictional brake lining against the brake body or releasing the brake lining from the brake body. In lieu of the nut, the spindle can be driven in a rotary fashion and the displacement motion of the nut thus produced can be used for the pressure application of the frictional brake lining.
The known wheel brake device with the worm gear has the disadvantage that depending on its type, the worm drive has a high proportion of sliding friction and as a result, has a poor efficiency and a high degree of wear. The wear reduces the efficiency over the service life. Moreover, there is a poor starting behavior as a result of the high degree of sliding friction, which impairs the ability of the wheel brake device to be metered. Due to the high proportion of sliding friction, which is required in principle, a large part of the energy is lost, primarily in reverse operation as an adjusting or -positioning gear. This results in a high degree of stress on the electric motor and its power supply.
OBJECT AND SUMMARY OF THE INVENTION
The wheel brake device according to the invention has the advantage over the prior art that the wheel brake device has a bevel gear pair as an angular gear. Due to a mutual rotating motion of the reciprocally meshing gear teeth of a bevel gear and a ring gear, the bevel gear pair has a low proportion of sliding friction and consequently has an improved efficiency and a low degree of wear. At a given capacity, the bevel gear pair can be accommodated in a smaller space and has a lower mass than a worm gear. A uniform transmission of force and moment is assured by means of a high contact ratio of the gear teeth of the pinion and the ring gear. The bevel gear pair has a good startup behavior, by means of which the brake force of the wheel brake device according to the invention can be finely metered.
The bevel gear pair, however, is susceptible to an axial displacement of the ring gear in relation to the bevel gear that meshes with the ring gear. The tooth flank play decreases or increases as a result of an axial displacement of the ring gear so that the gear teeth of the bevel gear and the ring gear do not mesh with each other and mutually rotate in the structurally provided manner so that even a slight axial displacement of the ring gear leads to a pronounced worsening of the efficiency of the bevel gear pair. The wear also increases. In order to prevent an axial displacement of the ring gear, in the wheel brake device according to the invention, the ring gear that drives the rotation/translation conversion gear to rotate is de-coupled from a reaction force, which results from a pressing force with which the rotation/translation conversion gear presses the frictional brake lining against the brake body. For the force de-coupling, the ring gear is connected in a rotationally fixed, axially mobile manner with the drive element of the rotation/translation conversion gear, i.e. for example to the nut or spindle of a screw link actuator. The rotationally fixed and axially mobile connection can be produced, for example, by means of a polygon profile, a multi-groove profile, or a serrated profile. The ring gear has a separate axial position that is independent of an axial position of the rotation/translation conversion gear. The axial position of the rotation/translation conversion gear axially supports this gear when the frictional brake lining is pressed against the brake body. The ring gear is free of the pressing force of the frictional brake lining against the brake body and from the resultant reaction force.
In order to maintain as exactly as possible the position of the ring gear in relation to the bevel gear that belongs to the bevel gear pair that meshes with it, the position of the ring gear is rigidly connected to a pivot bearing of the bevel gear, for example by way of a gear housing. The bevel gear can be attached to a motor shaft of the electric motor so that the motor shaft bearing is at the same time the pivot bearing of the bevel gear. Through the rigid connection of the pivot bearing of the bevel gear with the bearing of the ring gear, a structurally provided tooth flank play can be maintained in an almost constant manner even under stress and as a result, a favorable efficiency and low wear are achieved, even under stress.
Advantageous improvements and updates of the invention disclosed are possible by means of the measures set forth hereinafter.
The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of preferred embodiments taken in conjunction with the drawing.
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Hypoid gear set combines high reduction and compactness by Charles J. Murray.*
Hypoid gear definition.
Greigg Edwin E.
Greigg Ronald E.
Nguyen Xuan Lan
Robert & Bosch GmbH
Schwartz Christopher P.
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