Abstract:
A carburetor choke mechanism including an actuator linearly expanded and contracted based on a temperature change; a connection lever which is connected to a rotation axis at one end, and rotates based on receiving a thrust of the actuator; a choke lever which is connected with the other end of the connection lever, and receives a rotary force; and a valve shaft where a choke valve is fixed to one end thereof, and a valve shaft lever which receives a transfer of a rotary force from the choke lever is provided on the other end thereof, wherein the choke lever has a bottomed cylindrical shape covering an outer circumference of the valve shaft lever, and the valve shaft lever penetrates a bottom thereof, and is provided rotatably, and a connection mechanism between the connection lever and the choke lever is provided inside a cylindrical outer periphery of the choke lever.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a carburetor choke mechanism which controls a degree of opening of a choke valve automatically. 
     2. Related Background of the Invention 
     A choke mechanism is used in order to enhance an air-fuel ratio temporarily at the time of engine start-up. Although a choke valve has been opened and closed by manual operation heretofore, increasing recently has been an automatic choke type where the degree of opening of the choke valve provided in a carburetor has been made to be dependent on a change of an engine temperature for achieving stabilizing of a warming-up operation, and enhancing in fuel efficiency (for example, Patent Document 1). 
       FIG. 7  is a side view showing a conventional choke mechanism shown in Patent Document 1. In addition,  FIG. 8  is a sectional view of  FIG. 7 , and  FIG. 8A  shows an A-A cross section, and  FIG. 8B  shows a B-B cross section. 
     The choke mechanism described in Patent Document 1 is designed to have a mechanism in which a valve shaft  31   a  of a choke valve  31  is arranged at a position which is offset to one side from a center line of an intake-air path  30   a , and the choke valve  31  inclines against the center line of the intake-air path  30   a  so that a large side of the choke valve  31  rather than a small side thereof may be located at a downstream side of the intake-air path  30   a  in a fully closed state. A choke lever  33  is mounted in a form that it projects outside from a carburetor main body  30  of the valve shaft  31   a , and this choke lever  33  is comprised of a bottomed cylindrical part  33   a  fitted to the valve shaft  31   a  in a rotatable state, and of a lever arm  33   b  protruded in a integrated form on an outer side of this bottomed cylindrical part  33   a . In an inner side of the bottomed cylindrical part  33   a , a pair of stopper protrusions  34  and  34 ′ arranged at a certain interval in the circumferential direction are formed, and a valve shaft lever  35  has been fixed to the valve shaft  31   a  so that the valve shaft  31   a  may become rotatable only between these stopper protrusions  34  and  34 ′. Then, a valve shaft spring  36  to energize this valve shaft lever  35  so as to be abutted on one stopper protrusion  34  located at a closing side of the choke valve  31  is provided between the choke lever  33  and the valve shaft lever  35 . 
     At a lower outer circumference of the choke lever  33 , a pair of stopper walls  37  and  37 ′ which are arranged at an interval in the circumferential direction are formed, and a stopper pin  38  arranged between these stopper walls  37  and  37 ′ is protruded from the carburetor main body  30 . Then, by one stopper wall  37  abutting on the stopper pin  38 , a closing position C of the choke lever  33  at which the choke valve  31  is made to be fully closed is specified, and by the other stopper wall  37 ′ abutting on the stopper pin  38 , a opening position O of the choke lever  33  at which the choke valve  31  is made to be fully opened is specified. 
     Opening and closing of the choke valve  31  in the case of an automatic choke type is performed by using an actuator which is expanded and contracted depending on the change of the engine temperature. However, in the case of the choke mechanism like Patent Document 1, at the time of fully closing or small degree of opening of the choke valve  31 , if an engine intake-air negative pressure exceeds a certain value, a difference between a rotation moment caused by the intake-air negative pressure which operates on the large side of the choke valve  31  and a rotation moment caused by the intake-air negative pressure which operates on the small side of the choke valve  31  overcomes a rotation moment caused by the valve shaft spring  36 , and the degree of opening of the choke valve  31  may be increased. That is, the choke valve  31  is energized to a fully-closed side, and however, it has such a configuration as to be able to be opened without depending on an actuator when the intake-air negative pressure becomes large. Besides, the degree of opening thereof is limited by the valve shaft lever  35  being abutted on the other stopper protrusion  34 ′. 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Publication No. 4129244 
       
    
     SUMMARY OF THE INVENTION 
     Here, in the choke mechanism described in Patent Document 1, since the lever arm  33   b  is located on the outer side of the bottomed cylindrical part  33   a , a radius of rotation (arm length) for rotating the choke lever  33  inevitably becomes large, and it is necessary to enlarge a stroke of an actuator in connection with it. Consequently, a structure of the whole choke mechanism must be enlarged, and since the stroke is large, it takes time to open the choke valve  31 , and it will also result in causing deterioration of fuel consumption. 
     Then, the present invention makes it an object to provide a carburetor choke mechanism which, while being an automatic choke type, is capable of making short an arm length of a choke lever which rotates a choke valve, making the whole choke mechanism compact, and making opening/closing time of the choke valve short with a simple configuration. 
     In order to achieve an above-mentioned object, the carburetor choke mechanism according to the present invention may comprise: an actuator which expands and contracts in a straight manner based on a temperature change; a connection lever which is connected to a rotation axis at one end, and which rotates based on receiving a thrust of the actuator; a choke lever which is connected with the other end of the connection lever, and receives a rotatory force; and a valve shaft on which a choke valve is fixed, and which rotates based on receiving a rotatory force from the choke lever, wherein the choke lever has a bottomed cylindrical shape covering an outer circumference of the valve shaft, and the valve shaft penetrates a bottom thereof, and the choke lever is provided rotatably centering around the valve shaft, and at least a part of connection mechanism between the connection lever and the choke lever is provided inside a cylindrical outer periphery of the choke lever. 
     In addition, the carburetor choke mechanism may be configured so that the valve shaft has a valve shaft lever at one end side, and a rotatory force of the choke lever is transferred to the valve shaft by the valve shaft lever, and/or so that provided is a cap which covers a cylindrical opening of the choke lever, and which rotates together with the choke lever, and a connection mechanism between the connection lever and the choke lever has been provided on an upper surface of the cap; and/or so that the connection mechanism is one which is constituted by inserting a pin in a groove, and either the groove or the pin is provided on the cap, and the other of the groove or the pin is provided in the connection lever. 
     According to the carburetor choke mechanism of the present invention, since the whole structure can be made compact, and the degree of opening of the choke valve can be controlled by a small stroke, an effect that it becomes possible to drive a choke valve after starting an engine more effectively and in a short time can be achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a plan view showing a carburetor choke mechanism according to the present invention; 
         FIG. 1B  is a front view showing a carburetor choke mechanism according to the present invention; 
         FIG. 2A  is a plan view of a connection portion describing a relation between a choke lever and a connection lever; 
         FIG. 2B  is a schematic diagram describing a relation between a choke lever and a connection lever; 
         FIG. 3  is a sectional view describing an arm length; 
         FIG. 4A  is a figure in which a connection mechanism is provided on a cap used in the present invention, and shows an example of a connection groove; 
         FIG. 4B  is a figure in which a connection mechanism is provided on a cap used in the present invention, and shows an example of a connection plate; 
         FIG. 5A  is a figure in which a connection groove is attached, as a connection mechanism, to a cap used in the present invention; 
         FIG. 5B  is a figure in which a connection plate is attached, as a connection mechanism, to a cap used in the present invention; 
         FIGS. 6A ,  6 B, and  6 C show examples of a connection mechanism which does not use a cap; 
         FIG. 7  is a side view showing a conventional choke mechanism; 
         FIG. 8A  is an A-A sectional view of  FIG. 7 ; and 
         FIG. 8B  is a B-B sectional view of  FIG. 7 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to accompanying drawings. 
       FIG. 1  is a figure showing a carburetor choke mechanism according to the present invention, and  FIG. 1A  is a plan view, and  FIG. 1B  is a front view. 
     A driving source of this choke mechanism  10  is an electric type heat source actuator  13 . This electric type heat source actuator  13  is provided inside with a heater element which is not shown, and is configured so that internal wax may be distended when a temperature of this heater element rises, and thereby, a tip part  13   a  may be moved forward. After that, if electric conduction to the heater element is stopped and a temperature of the element descends, the tip part  13   a  will return to the original position. 
     The tip part  13   a  of the electric type heat source actuator  13  abuts on a connection lever  16 , and transfers a motive power thereto. The connection lever  16  is configured so that one end thereof is connected to a rotation axis, and the other end is connected to a choke lever  15 . Since the connection lever  16  is provided with a connection lever spring  16   b , and is energized toward the tip part  13   a  of the electric type heat source actuator  13 , the connection lever  16  is in a state of receiving a thrust always from the electric type heat source actuator  13 . Then, the connection lever  16  carries out rotational movement based on the thrust from the electric type heat source actuator  13 . 
     As for the connection lever  16  and choke lever  15 , a connection pin  16   a  is provided in the vicinity of an edge part of the connection lever  16 , and by inserting the connection pin  16   a  in a connection groove  21  provided on an upper surface of a cap  20  of the choke lever  15 , the connection lever  16  and choke lever  15  are made to be connected. Besides, conversely, the configuration may be such that the connection pin  16   a  is provided on an upper surface of the cap  20 , and the connection groove  21  is provided in the connection lever  16 . In the above configuration, a connection mechanism is configured by the connection groove  21  and the connection lever  16 . Then, as for this connection mechanism, at least a part of the configuration exists in an inner side of the outer periphery of the cylindrical choke lever  15 . 
     The cap  20  is, originally, a dust prevention cap which has been attached so that dust and water may not enter into the cylindrical choke lever  15 . In the case of having used it only for a usage of a dust prevention cap, what is necessary has been that the dust prevention cap has been just fitted in the choke lever  15  rotatably because of having covered only an opening of the choke lever  15 . However, since the cap  20  used in the present invention must transfer a power from the connection lever  16  to the choke lever  15 , the cap  20  and the choke lever  15  must be fixed mutually, by means of a pin or the like, so as not to rotate. A shape of the cap  20  and choke lever  15  may be configured so as to make the cap  20  and choke lever  15  not to be rotated mutually. 
     When connected by such connection mechanism as this, a movement of the tip  13   a  of the actuator will make the connection lever  16  rotate, and the connection pin  16   a  will transfer a rotatory force to the choke lever  15  while moving inside the connection groove  21 . Besides, since there are various methods other than this as a connection method of the connection lever  16  and choke lever  15 , variations thereof will be described later. 
     The choke lever  15  has a bottomed cylindrical shape, and has a cylindrical shape in the illustrated example, and however, the shape is not limited to the cylindrical shape. The shape may be a rectangular pipe shape or an ellipse shape. As for this choke lever  15 , a valve shaft  12  has penetrated a bottom part thereof. That is, the choke lever  15  has been fitted to the valve shaft  12  rotatably. In addition, at one end of the valve shaft  12 , a choke valve  11  is fixed, and at the other end of the valve shaft  12 , a valve shaft lever  17  is provided. Then, the structure is configured so that a rotatory force can be transferred to the valve shaft  12  from the choke lever  15  through the valve shaft lever  17 . 
     In an inner side of the choke lever  15 , stoppers have been provided in the same way as a conventional way, and the valve shaft lever  17  is limited so that the choke valve  11  can rotate only between a fully opened position and a fully closed position by means of the stoppers. In addition, a valve shaft spring  12   a  which energizes the valve shaft  12  in a full closing direction of the choke valve  11  is provided between the choke lever  15  and the valve shaft lever  17 . 
     Furthermore, other stoppers are provided at a lower outer circumference of the choke lever  15 , which limits the choke lever  15  so as to be able to rotate the choke valve  11  only between the fully closed position and fully opened position thereof. Besides, the choke lever  15  is energized in the full closing direction of the choke valve  11  by the choke lever spring  15   a.    
     In addition, in the same way as a conventional example, at the time of fully closing or small degree of opening of the choke valve  11 , if an engine intake-air negative pressure exceeds a certain value, a difference between a rotation moment caused by the intake-air negative pressure which operates on the large side of the choke valve  11  and a rotation moment caused by the intake-air negative pressure which operates on the small side of the choke valve  11  overcomes a rotation moment caused by the valve shaft spring  12   a , and the degree of opening of the choke valve  11  can be made to be increased. Then, the increase in the degree of opening is restricted by the valve shaft lever  17  abutting on the stopper. 
       FIG. 2  is a figure describing a relation between the choke lever and the connection lever, and  FIG. 2A  is a plan view of a connection portion, and  FIG. 2B  is a schematic diagram for description. In addition,  FIG. 3  is a sectional view describing an arm length. 
     A rotation angle required for making the choke valve  11  moved from a fully closed position to a fully opened position is assumed as β, and a distance from an axial center of the valve shaft  12  to an axial center of the connection pin  16   a  is assumed as R 1 , and a distance from a rotation axis of the connection lever  16  to the connection pin  16   a  is assumed as R 2 . Consequently, a stroke L of the connection pin  16   a  is determined by R 1  and β. Here, it is the electric type heat source actuator  13  that moves the connection lever  16 , and a rotation angle α is determined based on a specified stroke amount of the electric type heat source actuator  13 , and spatial relationship between a rotation axis of the connection lever  16  and the electric type heat source actuator  13 . Therefore, if the distance R 1  from the axial center of the valve shaft  12  to the axial center of the connection pin  16   a  is made to be short, the stroke L of the connection pin  16   a  can be made to be short in the same way, and the distance R 2  from the rotation axis of the connection lever  16  to the connection pin  16   a  can also be made to be short thereby. Thereby, the connection mechanism can be constituted compactly on the whole. 
     As for a conventional connection mechanism, as shown in  FIG. 3 , since a projection  25  or the like has been provided at an outer side of a cylinder part of the choke lever  15 , an arm length becomes R 1 ′, and as a matter of course, it is longer than the arm length R 1  of the present invention. Therefore, the connection mechanism will also have been made to be large on the whole. In the present invention, since adopted has been a configuration such that the connection pin  16  may come on an upper surface of the cap  20  in order to make R 1  small, the distance R 1  from the axial center of the valve shaft  12  to the axial center of the connection pin  16   a  can be made to be short. 
     The configuration like this enables the whole choke mechanism  10  to be compact. In addition, it is possible that the cap  20  conventionally used for dust prevention is utilized effectively, and the connection mechanism is provided on the cap  20 . 
     Then, a variation of the connection mechanism will be investigated.  FIG. 4  is a figure in which a cap used for the present invention is provided with a connection mechanism, and  FIG. 4A  shows an example in which a connection groove is provided, and  FIG. 4B  shows an example in which a connection plate is provided. In addition,  FIG. 5  is a figure in which a cap used for the present invention is provided with a connection mechanism, and  FIG. 5A  shows an example in which a connection groove is attached, and  FIG. 5B  shows an example in which a connection plate is attached. Here, although an example in which the connection groove  21  and the connection plate  22  are provided in a cap  20  side is shown, the connection pin  16   a  may be provided in the cap  20  side, and the connection groove  21  and the connection plate  22  may be provided in the connection lever  16  side. 
     In the case of a structure using the connection groove  21 , since the connection is carried out with the connection pin  16   a  inserted in the groove, there is no possibility that the connection mechanism will be dislocated. However, even without doing so far, because of energizing separately by means of a spring or the like, it is considered that the case where the connection mechanism is dislocated will be little even in the case of the connection plate  22  as shown in  FIG. 43 . In addition,  FIG. 4A  and  FIG. 4B  show the case where the cap  20  and the connection groove  21  or the connection plate  22  are manufactured as a unit, and however, these may be attached on an upper surface of the cap  20  using screws  23  or the like as shown in  FIG. 5A  and  FIG. 5B . As a matter of course, these may be attached with an adhesive. 
     In addition, the connection groove  21  or the connection plate  22  has a shape in which there exists a turnoff point and two straight lines seem to be connected. In the case of only opening and closing of the choke valve  11 , only one straight line part  21   a  or  22   a  is sufficient, and however, a reason for having provided straight line part  21   b  or  22   b  in addition to that is because adjusting is carried out so that a some oversized stroke rather than a required stroke may be generated since it is difficult to make a stroke of the electric type heat source actuator  13  constant. That is, if a stroke of the electric type heat source actuator  13  becomes larger than a prescribed amount, the connection lever  16  also is going to rotate more greatly than the required amount of rotation, and therefore, additional straight line part  21   b  or  22   b  is provided so that the connection pin  16   a  may escape then. Therefore, the additional straight line part  21   b  or  22   b  is configured as an angle such that the choke lever  15  does not rotate even in the case of the connection pin  16   a  passing. 
     Besides, at least a part of the straight line part  21   a  or  22   a  where the connection pin  16   a  conducts from fully closing to fully opening of the choke valve  11  may just be inside an outer periphery of the choke lever  15 , and a part may project in the outer side of the outer periphery. However, if all the straight line parts  21   a  and  22   a  exist inside the outer periphery of the choke lever  15 , the stroke of the actuator  13  can be made smaller, and the connection mechanism can be made more compact. 
     Examples shown so far have had the connection groove  21  or the like provided on an upper surface of the cap  20  covering the choke lever  15 , and however, a case where the cap  20  is not used is also considered.  FIG. 6  shows an example of a connection mechanism which does not use a cap. 
       FIG. 6A  and  FIG. 6B  show a case where there is no cap  20 . At this time, a projection  15   b  is made to be provided on an outer side of the choke lever  15 , and a connection groove  24   a  or a connection plate  24   b  may be just attached thereto with screws  23  or the like. Shapes (for example, the direction of a groove, etc.) of the connection groove  24   a  and the connection plate  24   b  are not limited to shown shapes, and however, since there is a purpose of making the arm length (R 1 ) short, the connection position should be made to exist inside the cylindrical shape of the choke lever  15 . 
     In addition, in  FIG. 6C , the cap  20  is used, and however, a case where the cap  20  is not used in the connection mechanism is shown. The projection  15   b  having a height exceeding the cap  20  is made to be provided on an outer side of the choke lever  15  also here, and a connection plate  24   c  is attached on a crown of the projection  15   b  with screws  23  or the like. The shape of the connection plate  24   c  is not limited in particular, and may be the same shape as the connection groove  24   a  or the connection plate  24   b , and may be the same shape as the connection groove  21  shown in  FIG. 1 . 
     As mentioned above, by providing at least a part of the connection mechanism over the choke lever  15 , or on the upper surface of the cap  20 , the stroke of the electric type heat source actuator  13  results in being short, and therefore, it is possible to make the choke mechanism compact. In addition, if the stroke is short, a driving period also becomes short, and therefore, the carburetor choke mechanism  10  which optimizes an air-fuel ratio, and leads also to enhancing fuel consumption has been achieved. In addition, such carburetor choke mechanism as this has general-purpose properties, and can be applied to many models.