Brake control apparatus for bicycle

Abstract: A brake control apparatus (1) for a bicycle. The appratus (2) has a control lever (4) operatively connected with a control cable for pulling the cable (I) and a force transmission ratio adjuster mechanism (12) for adjusting a force transmission ratio in association with an operation of the control lever. The force transmission ratio is defined as a ratio obtained by dividing an output force from the cable associated with application of a unit input force to a certain lever position of the control lever. With the appratus of the invention, this force transmission ratio is so determined as to have a maximum value at a position during an entire stroke of the lever between a stroke start end and a stroke finish end and the maximum value position is on the side of the finish end after a play stroke on the side of the start end.

Description: BACKGROUND OF THE INVENTION 1 FIELD OF THE INVENTION The present invention relates to a brake control apparatus for a bicycle according to the preamble of the main claim. 2 DESCRIPTION OF THE RELATED ART Such an apparatus is known (EP-A- 0 389 931, WO 87/05576 and FR-B-863 609). EP-A-0 389 931 forms part of the state of the art by virtue of Art. 54(3) EPC. With a typical conventional brake control apparatus the control lever is pivotably supported to a bracket and the control cable is fitted into a hole formed at the root end of the control lever. Accordingly, the connecting portion of the control cable relative to the lever is maintained fixed relative to the pivot of the control lever (e.g. Japanese published utility model gazette No. JP-72-57-9193). For fully understanding the present invention, it should be helpful to define and explain here some essential concepts on which the invention is based. First, a cable force ratio is defined here as a ratio obtained by dividing an output force of and along the cable associated with application of a unit input force to a certain position of the control lever by said unit input force. Second, considering the possibility that the input force applied to the lever substantially equates with the amount of work transmitted to the cable; then, a cable movement ratio is defined here as a ratio which varies in inverse proportion to the above force transmission ratio. That is to say, this cable movement ratio is obtained by dividing an amount of movement of the lever associated with a unit operation amount of the lever at a certain position thereof by said unit lever operation amount. These cable movement ratio and the force transmission ratio are predetermined by the construction of the brake control apparatus per se and are not directly affected by elastic modulus of the brake shoe and/or of the cable. Then, during an initial stroke of the lever where thin force transmission ratio has a relatively small value, even if a considerably large unit input force is applied to the lever. That is, even if the control lever is pulled with a considerably large manual force, the cable output force remains relatively small thus being unable to bring the brake shoes into sufficiently effective pressure contact with the rim of a bicycle wheel. On the other hand, if the same amount of input force is applied in the subsequent stroke, the cable output force will be excessive thus too quickly establishing the pressure contact between the shoes and the rim. In connection with this problem, according to the conventional apparatus, however, the distance between the pivot of the control lever and the connecting portion of the cable remains fixed throughout the operational stroke of the lever; that is, the force transmission ratio remains fixed regardless of the lever position subjected to the input force. Further, with the convention, the cable is connected with the lever so that within the limited entire stroke of the control lever the force transmission ratio has the minimum value during the braking stroke of the lever where the contact between the shoes and the rim is established. Therefore, it is impossible to maintain the force transmission ratio relatively high through the braking stroke of the lever, In short, even a relatively large amount of lever movement can often fail to provide sufficient braking force. In addition, since even a small amount of lever movement results in a large amount of movement of the shoes, a fine braking action has been very difficult. Accordingly, the primary object of the present invention is to provide an improved brake control apparatus which can apply a strong braking force oven with a small input force and which makes a fine braking action readily possible. SUMMARY OF THE INVENTION The above-noted object, a brake control apparatus for a bicycle according to the preamble of the main claim is solved by the characterizing features thereof. With these characterizing features of the invention, the force transmission ratio is so determined as to have a maximum value at a position during an entire stroke of the lever between a stroke start end and 8 stroke finish end, and this maximum value position is set on the side of the finish end after a play stroke on the side of the start end and also the maximum value position is on the side of the start end before a skid stroke on the side of the finish end. Accordinly, this construction is even more effective for the prevention of skid accident than the construction with the first-described features. According to these features of the invention, in addition to the above second features, the force transmission ratio is so determined that an average value thereof during a braking stroke is larger than further respective average values thereof in the play stroke and in the skid stroke. Further features are characterized in the subclaims. As described in details as above, the present invention has fully achieved the intended object of providing an improved brake control apparatus which can apply a strong braking force even with a small input force and which makes a fine braking action readily possible. Further, the invention's apparatus is advantageous also for preventing the dangerous skid accident due to locking of the brake shoes and the wheel rim. Moreover, with the effective utilization of the manual lever operating force, the apparatus provides the user with less fatigue under severe riding condition where strong and fine braking actions are required very frequently. Consequently, the invention's apparatus affords the user greater safety. Further and other objects, features and effects of the invention will become more apparent from the following more detailed description of the embodiments of the invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Accompanying drawings Figs. 1 through 8 illustrate a brake control apparatus according to one preferred embodiment of the present invention; in which, Fig. 1 is a vertical section of the apparatus, Fig. 2 is a graph of a force transmission ratio, Fig. 3 is a graph of a cable movement ratio, Fig. 4 is a principle diagram, Fig. 5 is an exploded view showing a bracket body and a cable connecting device, Fig, 6 is a side view showing the bracket body, Fig. 7 is a plane view showing the bracket body alone, and Fig. 8 is a section view taken along a line 8-8 of Fig. 1; Further drawings Figs. 9 through 11 illustrate other embodiments of the invention; in which, Figs. 9 and 10 show major portions in the vicinity of a lever shaft, and Fig. 11 is a graph of a force transmission ratio. DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the invention will now be described in particular with reference to the accompanying drawings. Figs. 1 through 8 show a first embodiment of the invention. Referring now to Figs. 1, 7 and 8, a brake control apparatus 1 of this embodiment includes a bracket 2 to be attached adjacent a grip G of a bicycle handle bar H and a control lever 4 pivotably supported to the bracket 2 via a lever shaft 3. On and about the lever shaft 3, there is fitted a lever spring 3a having its legs placed in abutment with the bracket 2 and the lever 4, respectively in order to urge the control lever 4 to its home position, i.e. a stroke start end. The bracket 2 includes a bracket body 5, shaped rectangular in cross section, for supporting the lever and an attaching member 6 for attaching the bracket body 5 to the handle bar H. This bracket 2 is entirely coated with resin. A cable structure W, to be operatively connected with this brake control apparatus for transmitting braking force from this apparatus to brake shoes disposed adjacent a wheel rim of the bicycle, includes an inner cable I, acting as a brake control cable, and an outer tube O covering the inner cable I. For connecting this cable structure W, the bracket body 5 includes, at a right upper position thereof, an outer tube receiver 7 for receiving the outer tube O while adjusting an exposed length of the inner cable I relative to this outer tube O. Accordingly, when the inner cable I is pulled, this cable I effects a relative movement with respect to the fixedly positioned outer tube O. That is, the brake control apparatus effects a braking operation by pulling, i.e. moving the inner cable I relative to the outer tube O in association with a user's manual operation on the control lever 4. With this apparatus operation, the brake shoes of an unillustrated brake device are brought into effective pressure contact with the wheel rim for braking a running bicycle. As shown in Fig. 1, the control lever 4 defines, at its base portion, a through hole 8 through which the lever shaft 3 is inserted. The control lever 4 further includes a control portion 9 having a substantially 'U'-shaped longitudinal cross section and extending toward the grip P when attached to the handle bar H and has, at the base portion thereof, a narrow portion 10 projectable into and withdrawable from the interior of the bracket body 5 when the lever 4 is pivotably operated for a braking action. Also, downwardly of the through hole 8, there is formed a projection 11 used for setting. This projection 11 will be detailled later. As still shown in Fig. 1, in an entire stroke of the control lever 4, a stroke start end S is restricted by a start end setting element 12 attached to the bracket body 5 and a stroke finish end E is restricted either by an exposed length of the inner cable I which length is adjusted by the outer tube receiver 7 or by abutment against the grip G. Referring more particularly to the setting of the stroke start end S of the control lever 4, this start end S is restricted by abutment between the start end setting element 12 disposed downwardly of the lever shaft 3 inside the bracket body 5 and the setting projection 11 of the control lever 4. For this abutment between the element 12 and the projection 11, an adjuster screw 12a is screwed into the bracket body 5 and its leading end 12b is so disposed as to come into abutment against the setting projection 11. Further, a coil spring 12c is fitted about the adjuster screw 12a for restricting rotation of this screw 12a. Accordingly, through adjustment of rotational amount of the adjuster screw 12a, fine adjustment of the stroke start end S of the control lever 4 can be made. As shown in Figs. 1 and 5, there is provided a cam device C including a cable connecting element 13 functioning as a cable connecting portion for operatively connecting the inner cable I with the control lever 4, an elongated slot 14 acting as a movement allowing face defined in the control lever 4, and a cam groove 15 acting as a cam face defined in the bracket body 5. As further shown in Figs. 1 and 5, the cable connecting element 13 includes a cam follower 16 for sliding contact with the elongated slot 14 and the cam groove 15 and a cable retainer 17 for connecting the inner cable I to the cam follower 16. More particularly, the cam follower 16 includes a cable hook shaft 16a made of metallic material and having stopped ends (i.e. of reduced diameter), and a resin tube 16b and a metallic tube 16c fitted one after the other in the mentioned order on the middle portion of the hook shaft 16a. Further, resin rollers 16d each having a flange are fitted on the stepped ends of the hook shaft 16a. All the above elements 16b, 16c and 16d are rotatably fitted on the hook shaft 16a. Also, the resin tube 16b and the resin rollers 16d are formed of an appropriate resin material having small frictional resistance and good anti-friction strength. The cable retainer 17 is mainly comprised of a base member 17a having a gate-like bent shape consisting of one bridge part and a pair of side parts continuous through the bridge part. Adjacent one distal ends of the side parts, there is defined a hook hole 17b for the insertion of the cable hook shaft 16a therethrough. Adjacent the other distal ends of the side parts, there is defined a nipple hole 17c for insertion of a nipple 11 of one distal end of the inner cable I, and contiuously with the nipple hole 17c and extending into the bridge part, there is defined an insertion slot 17d for allowing sidewise insertion of the inner cable I and also for retaining the nipple 11 thereat. As shown in Figs. 5 and 8, the cam groove 15 is formed in the opposed lateral sides of the bracket body 5. The shaping arrangement of this cam groove 15 will be detailled later. The elongated slot 14 is formed at the narrow portion 10 of the control lever 4 in such a manner that the slot 14 longitudinally extends radially about the lever shaft 3. Further, the mettalic tube 16c of the cam follower 16 is fitted into this elongated slot 14 while the resin roller 16d is fitted into the cam groove 15. Also, the side parts of the base member 17a of the cable retainer 17 are disposed sidewise across the elongated slot 14 and the cable hook shaft 16a is inserted into the hook hole 17b so as to operatively connect the cable retainer 17 with the cam follower 16. In operation, as the control lever 4 is pivotably actuated by a user's manual operation, the cable connecting element 13 is pivoted for moving the cam follower 16 to and away from the lever shaft 3. Incidentally, through abutment between the opposed flanges of the resin rollers 16d against the side edges of the cam groove 15, movement of these resin rollers 16d along the lever shaft 3 is effectively restricted. Also, in this condition, the rollers 16d fitted on the opposed stepped ends of the cable hook shaft 16a effectively prevent inadvertent fallout of this shaft 16a. According to the above-detailled construction, as illustrated in Fig. 4, moment acting on the lever 4 with application of manual force to a certain lever position is transmitted to the cable connecting element 13. Then, this moment acting on the control lever 4 can be obtained as a product of an input force P applied to a certain position of the lever multipled by a length L of an input arm defined by a perpendicular line drawn from the lever shaft 3 to an extension of the line of the input force. Although the magnitude and direction of this input force P varies according to the operation of the control lever 4, the amount of this variation is negligible. Therefore, the input arm length L can be considered as substantially constant through the entire stroke of the lover 4, regardless of the operational position of the lever 4. On the other hand, moment acting on the cable connecting element 13 is obtained as a product of an output force Q acting along the longitudinal direction of the inner cable I associated with the input force P of the control lever 4 multipled by a length M of an output arm defined by a perpendicular line drawn from the lever shaft 3 to an extension of the output force. Then, since the magnitudes of the moment acting on the control lever 4 and that acting on the cable connecting element 13 are substantially the same, we obtain: P x L = Q x M (a) Q = (P x L) / M (b) That is, it is possible to adjustably vary the output force Q by varying the output arm length M. In the instant embodiment, the cam groove 15 is curved facing the opposite side to the lever shaft 3 so that the cable connecting element 13 is positioned most adjacent the lever shaft 3 for rendering the output force arm length M short at a position between the stroke start end and the stroke finish end and on the side of the finish end after the play stroke on the side of the start end. Referring to Fig. 4, relationships among the output force value Q of the inner cable I, the force transmission ratio PR and the cable movement ratio MR will next be described in details. Suppose a small moving distance of the control portion 9 caused by a unit input force P to the control lever 4 at its certain position is d δ p and a small moving distance of the inner cable I caused by the sale unit input force P is d δ q; then, according to the law of conservation of momentum, we have: P x d δ p = Q x d δ q (c) The above equation (c) can be rewritten into an equation (d) below: P/Q = d δ q/ d δ p = (MR) (d) Then, assuming that the value of the input force P of the moment acting on the control lover 4 is substantially constant, the cable movement ratio MR varies In inverse proportion to the value of the output force Q. Further, the above equation (d) can be rewritten into an equation (e) below: (PR) = 1/(MR) (e) Therefore, the force transmission ratio PR varies in inverse proportion to the cable movement ratio MR. Next, the shaping of the cam groove 15 will be detailled with reference to Figs. 2 and 3 graphically showing the interrelated variations of the force transmission ratio PR and the cable movement ratio MR. In Fig. 2, a function curve f1 represents variation of the force transmission ratio PR with respect to variation in the movement amount of the inner cable I which is represented by the X axis. In Fig. 3, a function curve f2 represents variation of the cable movement ratio MR with respect to variation in the operation amount of the control lever 4 which is represented by the X axis. In these graphs, the entire stroke of the control lever 4 consists of three continuous ranges between the stroke start end (s) and the stroke finish end (e), that is, the play stroke S1 before and until the brake shoes come into effective contact with the wheel rim of the bicycle, the braking stroke S2 where the brake shoes brake the rotating rim after the contact, and the skid stroke S3 where the brake shoes end the rim are locked with each other thus causing a skid of the bicycle wheel on the ground. Incidentally, adjacent the braking stroke on the stroke start and, there exists a transition stroke S4 continuous with the play stroke S1. In this transition stroke S4, mechanical play present in the entire brake system of the bicycle is compensated for. That is to say, the effecting braking action takes place on the side of the stroke finish end after this transition stroke S4. Then, in the construction of the instant embodiment, the cam groove 15 corresponding to the braking stroke S2 is positioned adjacent the lever shaft 3 (see Fig. 6) so that the force transmission ratio PR has its maximum value MAX within the braking stroke S2 and on the side of the stroke finish end (e) beyond the transition stroke S4, as shown in Fig. 2. With this, as shown in Fig. 3, the cable movement ratio MR, which varies in inverse proportion to the force transmission ratio MR, has its minimum value MIN within the braking stroke S2 and on the side of the stroke finish end (e) beyond the transition stroke S4. Accordingly, during this braking stroke S2, because of the large value of the force transmission ratio PR, even with application of a relatively small input force to the control lever 4, the bicycle can be braked with a sufficiently large force. Further, during this braking stroke S2, because of the small value of the cable movement ratio MR, the inner cable I is moved by a relatively small amount even when the lever 4 is operated by a large amount. Therefore, the effective constact between the shoes and the rim is established relatively gradually, whereby fine braking force adjustment is possible. On the other hand, during the play stroke S1, the cam groove 15 corresponding to the play stroke S1 is positioned distant from the lever shaft 3 (see Fig. 6) so that the force transmission ratio PR has a small value during this play stroke S1. With this, the cable movement ratio MR has a small value as shown in Fig. 3. Accordingly , even if the brake shoes and the rim are disposed with a good clearance therebetween , a small amount of operation on the control lever can quickly establish the shoes-rim contact, thus enabling a quick braking action. Further, during the skid stroke S3 too, the cam groove 15 corresponding to this skid stroke S3 is positioned distant from the lever shaft 3 (see Fig. 6) so that the force transmission ratio PR has a small value during this skid stroke S3 as well. Accordingly, during this skid stroke S3, the operational force on the control lever 4 is transmitted to the inner cable I less efficiently, thus preventing a skid phenomenon when the lever is pulled excessively. Moreover, the cyclist feels this reduction in the force transmission ratio from the braking stroke S2 to the skid stroke S3 as sudden increase in the heaviness of the lever operation. Consequently, the cyclist can become aware of the danger of skid beforehand. Furthermore, according to the above-described arrangement, most of the entire stroke of the control lever 4 is used as the braking stroke S2. This further facilitates the fine braking force adjustment. As may be illustrated by the function curves f1 and f2 in Figs. 2 and 3, the average value of the force transmission ratio PR during the braking stroke is sufficiently larger than the average values thereof in the play stroke and in the skid stroke. Accordingly, the above-described functions and effects can be fully achieved. Incidentally, a further function curve g1 of Fig. 2 represents variation of the force transmission ratio PR of the conventional apparatus with respect to variation in the movement amount of the inncer cable I represented by the X axis. Similarly, a further function curve g2 of Fig. 3 represents variation of the cable movement ratio MR of the conventional apparatus with respect to variation in the operation amount of the control lever 4. Referece mark S2' denotes a braking stroke of this convention. As shown, the braking stroke S2 obtained by the apparatus of the present invention is greater than the stroke S2' of the convention. And, also during this braking stroke S2, the force transmission ratio PR of the invention's apparatus is greater than that of the convention, whereby even a small operation force can provide a strong braking effect. The brake control apparatus of the above embodiment is constructed for use with a flat handle bar employed often in so-called all-terrain bicycles. However, the present invention can be embodied as an apparatus adapted for any other shape of handle bar, such as a drop handle bar. Some other embodiments of the invention will now be described specifically. In the foregoing embodiment, the force transmission ratio adjuster mechanism C comprises the cam device. Instead, this mechanism C can be of any other type to be described next. In this second embodiment shown in Fig. 9, the same elements as those in the foregoing embodiment are provided with the same reference numerals. Reference numeral 20 denotes a take-up member rotatable about the lever shaft 3 in association with a pivotal operation of the control lever 4 so as to take up the inner cable I thereabout. This take-up member 20 includes an outer peripheral portion 21 and a retainer portion 22 provided at a part of the peripheral portion 21 for retaining the cable nipple 11. In operation, in association with a pulling pivotal operation of the control lever 4, the take-up member 20 takes up the inner cable I about its outer peripheral portion 21 to pull this cable I. In the course of this take-up action, the distance between the lever shaft 3 and the outer peripheral portion 21 varies in accordance with the lever position, thus varying the length M of the cable moment arm and consequently adjusting the force transmission ratio PR. A third embodiment will now be describe with reference to Fig. 10. In the alternate construction of this embodiment, at one side of the base portion of the control lever 4, there is provided a shaft 22, about which a cable retainer element 23 is loosely fitted. Further, forwardly with respect to the pivotal direction of the control lever 4 when pulled, a contact roller 24 contactable with the inner cable I is pivotably attached to the bracket body 5. In operation, as the control lever 4 is pulled, the inner cable I comes closer to the lever shaft 3 thus gradually shortening the output arm length M. Thereafter, as the lever 4 is further pulled, the inner cable I comes into contact with the contact roller 24, thus swithing over the direction of the output force Q of the cable moment thus increasing the output arm length M again. In this way, the force transmission ratio PR is adjusted by this construction. Next, some other modified constructions will be described specifically. (A) In the foregoing embodiments, the adjustment of the force transmission ratio PR is effected by varying the output arm length M. Instead, the adjustment is possible by varying the input arm length L, or by varying both arm lengths M and L. For instance, it is conceivable to construct a quadrople link mechanism by privotably attaching the control lever 4 to the bracket body 5 by means of a pair of link elements. Then, by appropriately setting pivot-to-pivot distances of this mechanism, the input arm length L can be changed for varying the force transmission ratio PR to a desired value. (B) In the foregoing embodiments, the work applied to the control lever 4 is directly transmitted to the inner cable I. Instead, it is also conceivable for the work to be transmitted indirectly to the cable I. For instance, it is conceivable to interpose, between the control lever 4 and the bracket body 5, a compression coil spring pivotable in association with a pivotal pulling operation of the control lever 4, such that during the play stroke S1 this compression spring is compressed to store the applied work thus reducing the force transmission ratio PR while during the braking stroke S2 the spring is released from the compression thus releasing the stored work and consequently increasing the force transmission ratio PR. Further, if the center axis of this compression spring is appropriately set in accordance with the pivoting amount of the control lever 4, it is possible to again reduce the force transmission ratio PR during the skid stroke S3. Therefore, with this modified construction too, the force transmission ratio PR can be varied to a desired value. (C) In the embodiment illustrated in Fig. 2, the maximum value MAX of the force transmission ratio PR is denoted by one point in the function curve f1. However, it is to be understood that as shown by a further function curve f3 in Fig. 11 this maximum value MAX can be a segment having a certain width rather than a single point. Similarly, the minimum value of the transmission force ratio PR can be a segment, as well. Indeeed, this function curve f3 of Fig. 11 is the most suitable characteristics for achieving the distinguished effects of the present invention. It is also conceivable to further modify this construction such that the force transmission ratio PR drops conspicuously sharply adjacent the border between the braking stroke S2 and the skid stroke S3. This modification is advantageous for making the cyclist aware of the danger of skidding as he feels sudden increase in the mechanical resistance against his pulling of the lever 4. Incidentally, the function curve f3 can be as denoted by a dotted line of the drawing so that the maximum value MAX may be positioned on the side of the stroke finish end (e) beyond the transition stroke S4. (D) In the foregoing embodiment, the movement allowing face is constructed as the elongated slot 14 while the cam face is constructed as the cam groove 15 and the cam follower 16 is fitted into these slot and groove. Various modifications of this construction are conceivable. For instance, it is conceivable to provide a pair of projections having the movement allowing face and the cam face, respectively so that the cam follower comes into sliding contact with the projections. (E) In the foregoing embodiments, the cable structure W has the outer tube O as well as the inner cable I. Instead, it is also conceivable to use the inner cable I alone, while eliminating the outer tube O.

Claims: A brake control apparatus for a bicycle, the apparatus having a control lever (4) operatively connected with a control cable (I) for pulling the cable (I); and a force transmission ratio adjuster mechanism (C) for adjusting a force transmission ratio (PR) in association with an operation of said control lever (4), said force transmission ratio (PR) being defined as a ratio obtained by dividing an output force (Q) from the cable (I) associated with application of a unit input force (P) to a certain lever position of the control lever (4); being characterized in that said force transmission ratio (PR) being so determined as to have a maximum value (MAX) at a position during an entire stroke of said lever (4) between a stroke start end (s) and a stroke finish end (e), said maximum value position (MAX) being on the side of said finish end (e) after a play stroke (S1) on the side of said start end (s). A brake control apparatus as defined in Claim 1, characterized in that said maximum value position (MAX) is set on the side of said stroke finish end (e) beyond a transition stroke (S4) continuous from said play stroke (S1), mechanical play present in a brake system being compensated for during said transition stroke (S4). A brake control apparatus as defined in Claim 2, characterized in that said control cable (I) is so connected to said control lever (4) that moment acting on said control lever (4) in association with operation of the lever (4) at the certain lever position is transmitted to said control cable (I); said force transmission ratio adjuster mechanism (C) effecting the adjustment of said ratio (PR) by varying a ratio of an arm length (M) of moment on said cable (I) by a further arm length (L) of the moment on said lever (4). A brake control apparatus as defined in Claim 3, characterized in that said control lever (4) is pivotably supported to a bracket (2) via a lever shaft (3); said control cable (I) is operatively connected with said lever (4) via a cable connecting portion (13); said force transmission adjuster mechanism (C) comprising a cam device (C) adapted for pivoting said cable connecting portion (13) in association with operation of said control lever (4) closer to and away from said lever shaft (3); said cable connecting portion (13) being moved closest to said lever shaft (3) at the lever position corresponding to the maximum value (MAX) of said force transmission ratio (PR). A brake control apparatus as defined in Claim 4, characterized in that said cam device (C) includes; a movement allowing face (14) formed on said control lever (4) for allowing said relative movement between said cable connecting portion (13) and said lever shaft (3), and a cam face (15) formed on said bracket (2) in association with said movement allowing face (14). A brake control apparatus as defined in claim 1 being characterized in that said maximum value position (MAX) being on the side of said start end (s) before a skid stroke (S3) on the side of said finish end (e). A brake control apparatus as defined in Claim 6, characterized in that said force transmission ratio (PR) is so determined that an average value thereof during a braking stroke (S2) is larger than further respective average values thereof in said play stroke (S1) and in said skid stroke (S3). A brake control apparatus as defined in Claim 7, characterized in that said maximum value position (MAX) is set on the side of said stroke finish end (e) beyond a transition stroke (S4) continuous from said play stroke (S1), mechanical play present in a brake system being compensated for during said transition stroke (S4). A brake control apparatus as defined in Claim 8, characterized in that said control cable (I) is so connected to said control lever (4) that moment acting on said control lever (4) in association with operation of the lever (4) at the certain lever position is transmitted to said control cable (I); said force transmission ratio adjuster mechanism (C) effecting the adjustment of the ratio (PR) by varying a ratio of an arm length (M) of moment on said cable (I) by a further arm length (L) of the moment on said lever (4). A brake control apparatus as defined in Claim 9, characterized in that said control lever (4) is pivotably supported to a bracket (2) via a lever shaft (3); said control cable (I) is operatively connected with said lever (4) via a cable connecting portion (13); said force transmission adjuster mechanism (C) comprising a cam device (C) adapted for pivoting said cable connecting portion (13) in association with operation of said control lever (4) closer to and away from said lever shaft (3); said cable connecting portion (13) being moved closest to said lever shaft (3) at the lever position corresponding to the maximum value (MAX) of said force transmission ratio (PR). A brake control apparatus as defined in Claim 10, characterized in that said cam device (C) includes; a movement allowing face (14) formed on said control lever (4) for allowing said relative movement between said cable connecting portion (13) and said lever shaft (3), and a cam face (15) formed on said bracket (2) in association with said movement allowing face (14).

Inventors: NAGANO MASASHI, NAGANO, MASASHI
Applicants: SHIMANO KK, SHIMANO INC.
Application year: 1990
Main classification: B62L3
IPC codes: B62L3