Machine element or mechanism – Mechanical movements – Grip units and features
Patent
1989-12-29
1991-07-09
Herrmann, Allan D.
Machine element or mechanism
Mechanical movements
Grip units and features
74200, F16H 1508
Patent
active
050294873
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND TO THE INVENTION
This invention relates to continuously-variable-ratio transmissions of the toroidal race rolling traction type. It relates especially to control of the variator, that is to say the ratio-varying unit, of such a transmission. Such units have been described in detail in various published patent specifications, such as GB-1296827, which will be described in more detail later. From this and other specifications it is known to provide a ratio-varying unit comprising an input disc and an output disc and rollers to transmit drive between them and a control member disposed within the unit (e.g. within the casing thereof) operable to vary the attitude of the rollers in unison and so vary the transmitted ratio.
In sophisticated transmissions using variators of the toroidal race type, it is known for the said member to be controlled by a lever which is precisely located at all times by a mechanism capable of working within close limits of accuracy. Examples of hydraulic mechanisms for this purpose are described in detail in GB-2023753-B and GB-2100372-B. The present invention, however, relates primarily to less sophisticated and expensive transmissions, and for the need to provide for the control member an operating mechanism that is simple and versatile and is operationally more effective than for the operator simply to hold the end of a lever.
SUMMARY OF THE INVENTION
According to one aspect the invention is characterised in that between a lever which is disposed outside the unit (e.g. outside the toroidal race assembly and normally outside a casing thereof) and the internal control member which is operable to vary the attitudes of the rollers in unison, there is a cam and follower, the cam positively determining the position of the follower.
Preferably the interaction of the cam and the follower is such that the relationship between angular movement of the cam and the resulting movement of the follower is non-linear.
The invention is particularly useful in a transmission which has a geared idle state; and the cam and follower may be arranged so that for a constant speed of rotation of the input disc, movement of the follower from one extreme of its movement to the other effects a change of motion of a final output member of the transmission from maximum speed of rotation in one sense to maximum in the opposite sense, through the geared idle state. The engagement of the cam and follower when the transmission is in the geared idle condition and no input force is being exerted upon the operating member of the mechanism, may be such that any tendency of the final output member to depart from a zero torque condition gives rise to a reaction between the follower and the cam which tends to move the follower so as to restore that zero torque condition.
In one form of the invention part of the cam may be of constant radius relative to the axis of rotation of the cam, and the follower may be in register with this part of the cam at geared idle.
Alternatively the said lever or the adjusting mechanism may be biased to the position corresponding to the geared idle state of the transmission.
The cam may be arcuate slot and the follower may be a pin or roller moveable in the slot.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a known mechanism by way of example;
FIG. 2 is view of a part of a transmission in accordance with the invention;
FIG. 3 shows further details of the transmission in a section taken on the line III--III in FIG. 2; and
FIG. 4 is similar to FIG. 2, but shows a modified cam.
DETAILED DESCRIPTION
FIG. 1, which corresponds to FIG. 1 of GB-1296827, shows a variator of the toroidal race rolling traction type comprising an input disc 10, formed with a part-toroidal race 10a carried on an input shaft 3, and an output disc 16 formed with a corresponding part-toroidal race 16a and coupled to an output shaft 6 by a bell-shaped member 4. Drive is transmitted between races 10a and 16a by three rollers 15, of which only one is shown. Each roller 15 is mounted in a roller carrie
REFERENCES:
patent: 3181381 (1965-05-01), Jorgensen
Farley Walter C.
Herrmann Allan D.
Laub David W.
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