Abstract:
A parking brake and shift mechanism for vehicles comprises a transmission shaft, a parking shift gear wheel, a stopper, and a dog clutch. The parking shift gear wheel is provided with at least one tooth to move in conjunction with the axis of the transmission shaft. The stopper is provided with at least one groove which contains the tooth. The dog clutch is fixed on the transmission shaft and provided with at least one concavity for accommodating the tooth.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a parking brake and shift mechanism, and more particularly to a parking brake and shift mechanism for vehicles. 
   2. Description of the Related Art 
   The two design parking break and shift mechanism designs for four wheeled vehicles comprise transmission-mounted and frame-mounted. Both serve as a parking brake and shift mechanism by preventing movement of the transmission shaft. Regardless of design all parking brake mechanisms are placed outside of the engine. The design and fabrication of outside the engine parking brake and shift mechanisms is not only more complex but occupies a larger volume. 
   Motorcycle engines are popularly employed in a great variety of four wheeled vehicles, such as all terrain vehicles (ATVs) due to their low weight and small size. Various ATV parking brake and shift mechanisms employ a latching mechanism (such as a rocker arm or cam) to latch the parking shift gear wheel to the transmission shaft. This type of mechanism, however, is rather complex. Moreover, if the existing design of the engine and related equipment is modified by the addition of a parking brake and shift mechanism, the level of complexity persists, resulting in difficulty in layout, excessive design modification, and increased development costs. 
   BRIEF SUMMARY OF THE INVENTION 
   A simple parking brake and shift mechanism is disposed inside a vehicle engine for braking and changing gears. The main feature of the invention is placement of the parking brake mechanism inside the engine, adding a shift gear wheel to the crankcase based on the existing engine, and locking the transmission shaft via the crank case to prevent rotation of the transmission shaft due to the engagement between the dog clutch on the transmission shaft and the shift gear wheel while parking. Thus, the engine provides a parking brake function. 
   The invention is advantageous in that it decreases the amount of occupied space outside the engine and the complexity of fabrication due to placement of the parking brake inside the engine. Fewer components and lower cost result due to the use of existing gear mechanisms requiring only slight modification. Thus, the parking brake mechanism of the invention can be easily implemented in existing motorcycle engines, expanding the range of applications for existing motorcycle engines in four wheeled vehicles such as ATVs and greatly increasing the competitiveness of existing engines. 
   A detailed description is given in the following embodiments with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
       FIG. 1  is a sectional view of the parking brake and shift mechanism of the invention shifted into neutral gear; 
       FIG. 2  is a sectional view of the parking brake and shift mechanism of the invention shifted into parking gear; 
       FIG. 3  is a perspective diagram showing the relationship between the crankcase, the shift gear wheel and the dog clutch while the parking brake and shift mechanism of the invention is shifted into parking gear; 
       FIG. 4  is a perspective diagram of the parking brake and shift mechanism of the invention while the dog clutch abutting the parking shift gear wheel; 
       FIG. 5  is a sectional view of the parking brake and shift mechanism of the invention not shifted into parking gear; 
       FIG. 6  is a perspective diagram showing the relationship between the crankcase, the parking shift gear wheel and the dog clutch while the parking brake and shift mechanism of the invention is not shifted into parking gear; 
       FIG. 7  is a sectional view of the gearshift protecting mechanism protecting the gearshift at the axial position; 
       FIG. 8  is a sectional view of the gearshift protecting mechanism at the axial position as the gearshift is shifted; and 
       FIG. 9  is a sectional view of the gearshift protecting mechanism at the radial position as the gearshift is shifted. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
     FIG. 1  is a sectional view of the parking brake and shift mechanism of the invention in neutral, wherein the parking brake and shift mechanism for vehicles, disposed in crankcase  4 , mainly comprises a gearshift lever  1 , a gearshift drum  2 , a gearshift fork  3 , a transmission shaft  8 , a dog clutch  7 , a parking shift gear wheel  6 , a stopper  41 , a return spring  5 , a gearshift protection pin  9 , and a return spring of gearshift protection pin  10 . 
   The relationships between each component are described in the following: 
   Transmission Shaft—As shown in  FIG. 3 , the dog clutch  7  and the parking shift gear wheel  6  are sequentially disposed on the transmission shaft  8 . The dog clutch  7  is fixed to the transmission shaft  8  and provided with one or a plurality of concavities  72  and convexities  71 . The parking shift gear wheel  6  is axially moveable along the transmission shaft  8  and provided with one or a plurality of teeth  61  mesh with the concavities  72  of the dog clutch  7 . 
   Stopper—The stopper  41  is fixed to the crankcase  4  or integrated with the crankcase  4 . The stopper  41  is further provided with one or a plurality of grooves  411  to contain the teeth  61  for constraining rotation of the parking shift gear wheel  6 , but allowing the parking shift gear wheel  6  to move axially along the transmission shaft  8 . 
   Return Spring—The return spring  5  is mounted between the parking shift gear wheel  6  and crankcase  4 . If the parking shift gear wheel  6  is pushed toward the stopper  41  by an external force, the return spring  5  will return the parking shift gear wheel  6  back to the original position when the external force is removed. The return spring  5  can be replaced with an elastomer such as a leaf spring, an elastic rubber, a gasbag, or similar. 
   When the parking brake and shift mechanism is shifted as shown in  FIG. 2 , the gearshift lever  1  is pulled to rotate the gearshift drum  2  as shown in  FIG. 1 , and the gearshift fork  3  is moved down, and the convexity  71  of the dog clutch  7  is driven downward to the interval between teeth  61  of the parking shift gear wheel. At this moment, the three convexities  71  of the dog clutch  7  mesh with the six teeth  61  of the parking shift gear wheel  6  separately and symmetrically as shown in  FIG. 3 . Thus, transmission shaft  8 , dog clutch  7  and the parking shift gear wheel  6  merge into one unit and prevent rotation of the transmission shaft  8  due to the engagement of groove  411  of stopper  41  and tooth  61  of the parking shift gear wheel  6 , thus parking occurs. 
   When the parking gear is shifted as shown in  FIG. 4 , the convexity  71  of the dog clutch  7  may potentially abut the tooth  61  of the parking shift gear wheel  6 . Thus, the parking gear is not shifted because the dog clutch  7  is not able to engage the parking shift gear wheel  6 . At this moment the dog clutch  7  pushes the parking shift gear wheel  6  toward the return spring  5 . Thus, the return spring  5  is compressed as shown in  FIG. 5  and  FIG. 6 . 
   If the vehicle is moved slightly by external force or by gravity, the transmission shaft  8  will slightly rotate the wheel, and the convexity  71  of the dog clutch  7  will mesh with the teeth  61  of the parking shift gear wheel  6  as shown in  FIG. 3 . At this moment, in a normal parking shift situation as shown in  FIG. 2 , the parking gear is shifted as shown in  FIG. 2  because the parking shift gear wheel  6  is returned to its original position by the return spring  5 . 
   When the parking gear is shifted out of the parking gear, the gearshift lever  1  is pulled to rotate the gearshift drum  2  and drives the gearshift fork  3  upward, thus, the teeth  61  of the parking shift gear wheel  6  leave the convexities  71  of the dog clutch  7  and the transmission shaft  8  can again freely rotate to shift out of parking gear. 
   In order prevent user error when shifting, a gearshift protection pin  9  is mounted on the crankcase  4  and inserted into the gearshift drum  2  in an axial direction for constraining the gear shift drum  2  as shown in  FIG. 7 . The return spring of gearshift protection pin  10  is further mounted on the crankcase  4  for keeping the gearshift protection pin  9  in the original position. 
   When the gearshift lever  1  is pulled for shifting into parking gear or out of parking gear as shown in  FIG. 8 , the gearshift protection pin  9  must be pulled out to enable the gearshift drum  2  to rotate for shifting. After shifting, the gearshift protection pin  9  is pushed back to the original position by the return spring of gearshift protection pin  10  and returns to the protecting position. The return spring of gearshift protection pin  10  can be replaced by the elastomer such as the leaf spring, the elastic rubber, and the gasbag. The gearshift protection pin  9  can also be mounted on the crankcase  4  and inserted into the gearshift drum  2  in a radial direction of the gear shift drum  2  for constraining rotation of the gearshift drum  2  and user error, as shown in  FIG. 9 , can be prevented. 
   While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.