WO1987007933A1

WO1987007933A1 - Automatic variable transmission for vehicles

Info

Publication number: WO1987007933A1
Application number: PCT/FI1987/000083
Authority: WO
Inventors: Urpo Mantovaara; Jouko Niemi
Original assignee: Variped Oy
Priority date: 1986-06-17
Filing date: 1987-06-17
Publication date: 1987-12-30
Also published as: JPH01503081A; FI862579A0; FI75036C; AU7546087A; FI75036B

Abstract

A variable transmission automatically changing its transmission ratio in accordance with the resistance to propagation of the vehicle, in which the power-transmitting transmission link is a V-belt (1) or equivalent and in which the primary pulley consists of cup disks (2, 3) urged against each other by effect of a spring force. In the variable transmission of the invention, the inner cup disk (3) of the primary pulley is connected to the hub of the primary shaft with a short multiple-end thread, through which the torque of the shaft tends to move the cup disks (2, 3) in relation to each other, thus way changing the pressure effect of the spring force and at the same time preventing tilting of the cup disk.

Description

Automatic variable transmission for vehicles

The present invention concerns a variable transmission which auto¬ matically changes its transmission ratio in accordance with the resistance to propagation of the vehicle and in which the power- transmitting link is a V-belt or equivalent, and in which the primary pulley consists of cup disks urged against each other by action of a spring force, connected with pins to be non-rotatable in relation to each other and so connected to the shaft that one of them is axial ly movable and the other is fixed but rotatably carried.

An automatic variable transmission for a bicycle is known in the art for instance through the reference DE PS 93896, the principle of the transmission therein disclosed being that the pulleys for the flat belt serving as transmission link are made of helical leaf springs which in the secondary pulley are curved in the direction of rotation and in the primary pulley, against it. This principle has later been applied in several references, for instance by supplementing or replacing the springs with levers moving in helic¬ al grooves. A drawback of transmissions of this type are pulley designs which are complex and involve friction and are sensitive to dust and dirt.

A torque-sensing V-belt pulley is known in the art for instance through the reference DE PS 224180, where admittedly the pressure effect of the cup disk rotating with reference to the other half with screw juncture only serves to boost the lever control acting on both belt pulleys. V-belt pulleys consisting of cup disks which are non-rotatable in relation to each other have been tried out in the first place i n drives for auxiliary apparatus of internal com¬ bustion engines, such as charging generators and fans, where compression or torsion springs also occur in addition to threads. A design of this kind is for instance disclosed in the reference USP 2,478,289.

The object of the present invention is to eliminate the above draw¬ backs. The variable transmission of the invention automatically changing transmission ratio in accordance with the resistance to propagation of the vehicle is characterized in that the axial ly moving cup disk has been connected to the shaft with a short multiple-end ball thread, through which the torque on the shaft tends to move the cup disks i n relation- to each other, thus chang¬ ing the pressure effect of the spring force and simultaneously pre¬ venting tilting Df the cup disk.

The object of the invention is t.o provide a variable transmission which in all circumstances automatically and steplessly changes its transmission ratio and which is competitive in efficiency with a chain transmission, and which has not been achieved so far.

An advantageous embodiment of the variable transmission of the in¬ vention is characterized in that the effect of torque reduces the pressure effect of spring force.

An advantageous embodiment of the variable transmission of the in¬ vention is also characterized in that the ball thread connecting the the axially moving cup disk of the primary pulley to the shaft is a multiple-end screw provided with at least one ball in each thread.

An advantageous embodiment of the variable transmission of the in¬ vention is also characterized in that the contact of the balls with the flank surfaces of the thread is a four-point contact when radial load is present.

An advantageous embodiment of the variable transmission of the invention is also characterized in that the axially fixed cup disk of the primary pulley is connected to the hub of the primary shaft with a four-point ball bearing, the screws connecting the outer races of said varying at the same time constituting the fixing of the support ring of the compression spring and providing control preventing rotation of the cup disks in relation to each other.

An advantageous embodiment of the variable transmission of the invention is also characterized in that at least one surface touch¬ ing the side of the belt on the pulleys transmitting power is grooved in a manner known in itself in the art.

An advantageous embodiment of the variable transmission of the invention is also characterized in that the curve shape of the grooving approximates an evolvent.

An advantageous embodiment of the variable transmission of the in¬ vention is also characterized in that the torque of the primary shaft can be changed by substituting for the recessed cup spring acting as compression spring another which is thinner or thicker.

An advantageous embodiment of the variable transmission of the in¬ vention is also characterized in that the torque of the primary shaft can be adjusted with adjusting springs or cylinders contain¬ ing pressurized fluid pushing the axially movable cup disk towards the fixed one.

An advantageous embodiment of the variable transmission of the in¬ vention in which also the secondary pulley consists of cup disks urged together is also characterized in that the pressurized fluid increasing the compression of the cup disks in the primary pulley reduces the compression of the cup disks in the secondary pulley.

An advantageous embodiment of the variable transmission of the in¬ vention in which the secondary pulley is fixed is also character¬ ized in that the pressurized fluid urging the cup disks of the primary pulley together increases the tension of the belt through the action of a jockey pulley. An advantageous embodiment of the variable transmission of the in¬ vention is also characterized in that the flow passage of the pressurized fluid is provided with a resistance check valve known in itself i n the art, with the aid of which the movement of the cup disks of the primary pulley away from each other can be retarded as the torque increases.

The variable transmission of the invention is provided with a thread sensing the torque on the shaft, but the design differs from those known in the art -in that here are at least two effective spring systems and they are both either settable or adjustable while driving.

The invention is described in the following more in detail with the aid of an example, referring to the drawing attached, in which: -

Fig. 1 presents a section of a pedalling shaft with bearing arrangements and of the primary pulley, the cup disks being as far from each other as possible and the contact ring being small;

Fig. 2 presents a quadrant of the compression spring of the primary pulley, viewed from the left end of the pedal shaft;

Fig. 3 presents a section A-A of the primary pulley, carried between the guide sleeves, the cup disks being as close to each other as possible;

Fig. 4 presents the pitch cylinder of the ball thread, developed into a plane and in both extreme positions;

Fig. 5 presents in section a modification of the primary pulley wherein the control force is transmitted through a thrust bearing from small cylinders pressing against the race of the latter;

Fig. 6 presents schematically a transmission wherein the primary pulley is a circular variable pulley and the secondary pulley is f i xed ;

Fig. 7 presents schematically a transmission wherein both pulleys are circular variable pulleys;

Fig. 8 presents schematical y a transmission wherein the primary pulley is an oval variable pulley and the secondary pulley is fixed, and

Fig. 9 presents schematically a transmission wherein both pulleys are variable pulleys and the primary pulley is oval.

In Fig. 1 is presented the pedal shaft with its bearing arrangements in a stepless variable transmission according to the invention for a bicycle, in which a V-belt 1 serves as transmission link. The primary pulley consists of cup disks 2 and 3 urged against each other under the effect of a spring force. The belt 1 runs between the cup disks 2 and 3. As taught by the invention, the axially movable cup disk 3 of the primary pulley is connected to the hub 9 of the primary shaft with a short multiple-end thread, through which the torque of the shaft tends to move the cup disks 2 and 3 in relation to each other, thus changing the pressure effect of the spring force and at the same time preventing tilting of the cup disk. The torque acts in th direction reducing the pressure effect of the spring force. In Fig. 1 is shown a section of the primary pulley, the cup disks 2 and 3 being as far from each other as possible and thus, the contact ring being small.

Fig. 5 presents, sectioned, an advantageous embodiment of the in¬ vention in which the control force on the primary pulley is trans¬ mitted through a thrust bearing from small cylinders 19 pressing against its race. The axially fixed cup disk 2 is attached to the outer races 4 and 3 of the four-point ball bearing with screws 11, which in addition fix the support ring 6 of the the cup spring 7 at a distance defined by the spacer sleeves 12. The spacer sleeves 12 are at the same time guides for the cup disk 3 and they prevent the rotation of the disks 2 and 3 in relation to each other. In Fig. 2 is shown a quadrant of the compression spring of the primary pulley, viewed from the left end of the pedal shaft carrying the pedal 13.

In Fig. 3 is shown a section A-A of the primary pulley, carried between the guide sleeves 12 in a position in which the cup disks 2 and 3 are as close as possible to each other. Half of the peri¬ pheral force of the belt 1, in other words, the share of the cup disk 2, is transmitted .over the sleeves 12 to the cup disk 3 whence the whole torque is transmitted over the screw ring 8 of the ball thread and the balls 15 to the nut ring, that is, to the hub ring 9 of the pedal shaft.

The parallelity of the cup disks 2 and 3, which is paramount in view of the efficiency of the transmission, is maintained by action of the four-point bearing 14 and the thread balls 15. In an advantgeous embodiment, the contact of both balls under radial loading is a four-point contact and it is free of play. In Fig. 4 is shown the pitch cylinder of the ball thread, developed into a plane and in both extreme positions. The thrust bearing, comprising a ball ring 16, an inner race 18 and O-rings 17 of the i nner race, or a cylinder 20 associated with the hub ring, constitute a similarly axially movable guidance reducing the cu disk tilt.

The torque of the primary shaft can be changed by substituting for the recessed cup spring 7 acting as the compression spring, one which is thinner or thicker. The torque can be adjusted with the aid of adjustment springs pushing the axially movable cup disk 3 towards the fixed disk 2, or with the aid of cylinders containing pressurized fluid. If the secondary pulley also consists of cup disks being urged together, the course of the pressurized fluid may be arranged so that the pressurized fluid increasing the compression of the cup disks 2 and 3 in the primary pulley reduces the compression of the cup disks in the secondary pulley. If the secondary pulley is fixed, the pressurized fluid urging the cup disks 2 and 3 of the primary pulley together may increase the tension of the belt 1 by means of a jockey pulley.

The reciprocating variations, on each revolution, caused by varying torque due to changing pedal position can be prevented by the aid of a resistance check valve V inserted in the flow passage of the pressurized fluid; such a valve may in the design of Figs 1 and 3 be provided in a flow passage system created by borring in the hub ring. With the aid of the valve V, the movement away from each other of the cup disks- 2 and 3 of the primary pulley can be retard¬ ed.

Pressure control of the pressurized fluid is accomplished with a cylinder preloaded with an adjustment spring, its advantageous placement being on the handle-bar of the bicycle or close thereto. The control spring may also be constituted by compressed air which is only transformed into oil pressure, with a pressure transformer, close to the variable pulley.

Fig. 6 presents schematically a transmission in which the primary pulley is a circular variable pulley and the secondary pulley is fixed. In Fig. 6 is also shown a jockey pulley 21. Fig. 7 presents schematically a transmission in which both pulleys are circular adjustable pulleys. Fig. 8 presents schemat cally a transmission in which the primary pulley is an oval variable pulley and the secondary pulley is fixed. Furthermore, in Fig. 9 is shown a schematic diagram of a transmission in which both pulleys are vari¬ able pulleys and the primary pulley is oval. Straight arrows indicate the direction of the pedal force and curved arrows, the direction of rotation. In a variable transmission i n which the se¬ condary pulley is fixed, a jockey pulley 21 is required which may be loaded merely by a spring force dependent on the adjustment position or, in addition, also by the pressurized fluid. In a vari¬ able transmission in which also the secondary pulley is a variable pulley consisting of cup disks, the effect of the pressurized fluid has to be inverse related to that acting on the primary pulley. If the primary pulley is oval, a jockey pulley 21 equalizing the belt length is required regardless of whether the secondary pulley is fixed or a pulley variable like the primary pulley but changing the radius of its contact ring in opposite direction, both of which are conceivable within the scope of the present invention.

In an advantageous embodiment of the invention the adjustable sus¬ pension system is a liquid or air spring suspension or a combina¬ tion of both, whereby excessively rapid control movements can be prevented by means of throttling.

Since the object of the invention is primarily the primary pulley which in a bicycle is usually larger than the secondary pulley and in hich the contact arc is always more than 180°, arranging for retardation by making the cup disks rotatable in relation to each other during adjustment is not a good solution.

The properties and range of adjustment described in the foregoing are sufficient to guarantee reliable operation and good efficiency, provided that the belt is flexible and has sufficient rigidity against tension and lateral compression and that it has been manu¬ factured to be uniform enough in quality and dimensional ly accurate.

In very dirty conditions or in rain some slipping may still occur, and such is best counteracted by providing one of the contact sur¬ faces of the secondary pulley with spiral grooves. Such grooving may also be used for higher efficiency and in order to reduce the belt wear if the spiral configuration is made to approximate an evolvent, as disclosed in the Finnish patent application No. 853430.

The reliability and precision in operation of the variable trans¬ mission may also be improved by further developing the control system. Modern electronics, pick-up technique and hydraulics offer opportunities which are becoming better, and developing, all the t ime .

It is obvious to a person skilled in the art that various embodi¬ ments of the invention are not exclusively confined to the example presented in the foregoing and that they may vary within the scope of the claims stated below.

Claims

C l a i ms

1. A variable transmission automatically changing transmission ratio in accordance with the resistance to propagation of the vehicle, in which the power-transmitting transmission link is a V-belt (1) or equivalent and in which the primary pulley consists of cup disks (2,3) urged against each other by effect of a spring force and which are interconnected with pins to be non-rotatable in relation to each other, and so connected to the shaft that one of them is axially movable and the other is fixed but rotatably carried, characterized in that the axially movable cup disk is con¬ nected to the shaft with a short multiple-end ball thread, through which the torque of the shaft tends to move the cup disks (2,3) in relation to each other, thereby varying the pressure effect of the spring force and at the same time preventing tilting of the cup disk.

2. Variable transmission according to claim 1, characterized in that the effect, of the torque is one which reduces the pressure effect of the spring force.

3. Variable transmission according to claim 1 or 2, characterized in that the ball thread connecting theaxially movable cup disk of the primary V-belt pulley to the shaft is a multiple-end ball screw having at least one ball (15) in each thread.

4. Variable transmission according to claim 3, characterized in that the contact of te balls (15) with the flank surfaces of the thread is a four-point contact when radial load is present.

5. A variable transmission according to any one of the preceding claims, characterized in that the axially fixed cup disk (2) of the primary pulley attaches to the hub (9) of the primary shaft with a four-point ball bearing (14), the screws (11) connecting its outer races at the same time constituting the attachment of the support ring (6) of the compression spring (7) and a guide (12) preventing rotation of the cup disks (2,3) in relation to each other.

6. A variable transmission according to any one of the preceding claims, characterized in that at least one of the surfaces in con¬ tact with the a side of the belt (1) on the power-transmitting pulleys is grooved in a manner known in itself in the art.

7. Variable transmission according to claim 6, characterized in that the curved shape of the grooving approximates an evolvent.

8. Variable transmission according to any one of the preceding claims, characterized in that the torque of the primary shaft can be changed by substitutingx for the recessed cup spring (7) serving as compression spring another which is thinner or thicker.

9. Variable transmission according to any one of the preceding claims, characte ized in that the torque of the primary shaft can be adjusted with adjusting springs pushing the axially movable cup disk towards the fixed one, or with cylinders containing pressuriz¬ ed fluid.

10. Variable transmission according to claim 9, in which also the secondary pulley consists of cup disks curged together, charactei— ized in that the pressurized fluid increasing the pressing together of the cup disks (2,3) in the primary pulley reduces the pressing together of the cup disks in the secondary pulley.

11. Variable transmission according to claim 9, in which the secondary pulley is fixed, characterized in that the pressurized fluid pressing together the cup disks (2,3) of the primary pulley increases the tension of the belt (1) by means of a jockey pulley (21) .

12. Variable transmission according to any one of the preceding claims, characterized in that in the flow passage of the pressurized fluid is provided an adjustable resistance check valve (V) known in itself in the art, with the aid of which the movement away from each other σf the cup disks (2,3) of the primary pulley may be retarded when the torque increases.