192 clutches and power-stop control – Clutches – Progressive engagement
Patent
1995-09-13
1997-05-06
Lorence, Richard M.
192 clutches and power-stop control
Clutches
Progressive engagement
192 5334, 192108, 192114T, 74339, F16D 2302, F16D 1106
Patent
active
056262132
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an engaging device for a gear freely rotatably mounted on a shaft in a transmission, for locking the gear to the shaft or releasing the gear from the shaft, comprising an engaging sleeve mounted non-rotatable but axially displaceable relative to the shaft, and provided with engaging teeth, and a toothed rim joined to the gear and provided with corresponding engaging teeth, the engaging teeth having pointed end portions and opposite flanks connected thereto, each of the flanks being provided with a step spaced from the end portion, so as to form first surface portions inclined from the pointed end portion towards the step, on the engaging teeth of the engaging sleeve and of the gear.
BACKGROUND OF THE INVENTION
Engaging devices of this type are generally used in modern motor vehicle gearboxes. The inwardly inclined surface portions of the tooth flanks are designed to increase the engaging force of the engaging sleeves, i.e. prevent an engaged gear from "popping out" due to the engaging sleeve being displaced from its engaged position under high torque load and during power shifting. The inwardly inclined surface of the tooth flank causes the force acting on the flank in the rotational direction to have a force component acting in the engagement direction of the engaging sleeve, the magnitude of the force component depending on the angle of the inclined surface portion relative to the rest of the flank surface.
One result of the engaging teeth of the engaging sleeve and the free gear being provided with tooth flanks, the outer end portions of which are inclined inwards, is that there must be, depending on the angle of incline, a certain amount of play between the engaging teeth of the engaging sleeve and the free gear. This play causers backlash in the gearbox and in modem gearboxes this backlash amounts to about 50% of the total backlash in the gearbox.
In general, the smaller the play is between the teeth of the engaging sleeve and the free gear, the smaller the risk will be for gear disengagement during power shifting. In modern serial production of gearboxes most units would function without any risk of disengagement even with a very small angle of inclination (between 1.degree. and 2.degree.) and consequently with very, little play, but it is unavoidable that for a small number of gear-boxes the variations within the tolerances will be such that there will be a large backlash in the gearbox despite the small angle of inclination of the flank portion, giving rise to the risk of gear disengagement. In order to achieve full security by unfavourable variation within tolerances in new gearboxes and in gearboxes with backlash caused by wear, the teeth of the engaging sleeve and the free gear are therefore made with surface portions, the angle of inclination of which is between 3.degree. and 4.degree.. However, the consequence of this is that the backlash in most gearboxes will be greater than what it actually needs to be.
SUMMARY OF THE INVENTION
The purpose of the present invention is to provide an engaging device of the type described by way of introduction, which combines the two apparently non-compatible properties of small backlash and great security against gear pop-out.
This is achieved according to the invention by virtue of the fact that the tooth flanks of the engaging sleeve are provided with a second step spaced from the first step so that second surface portions are formed which are inclined from the first step towards the second step and which have a smaller angle of inclination relative to a plane parallel to the adjacent flank surfaces inside the second step than the first surface portions.
The second surface portion can have an angle of inclination of between 1.degree. and 3.degree., which provides adequate security against gear disengagement in most cases. The angle of inclination of this surface portion determines the required play, which will be small. The first surface portion can have an angle of inclination of between 3.degr
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patent: 4727968 (1988-03-01), Chana
patent: 4848548 (1989-07-01), Diehl
AB Volvo
Lorence Richard M.
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