Abstract:
An engine mount structure for an apparatus equipped with an engine mounts an engine on a resin casing with an elastic body therebetween. The structure includes: a base plate arranged so that one side thereof faces the engine and the other side thereof faces the casing; a cylindrical elastic body that protrudes toward the engine from the base plate and is provided at an end portion thereof on an engine side with a securing member on which the engine is fixed; and a bolt that protrudes toward the casing from the base plate and couples the casing and the base plate to each other. An area where the bolt is disposed on the base plate protrudes in a stepped shape toward the engine from an area where the elastic body is disposed on the base plate.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present application claims priority from Japanese Patent Application No. 2013-043045 filed on Mar. 5, 2013, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to an engine mount structure for an apparatus equipped with an engine and more particularly relates to an engine mount structure that makes it possible to reduce the size of the apparatus. 
         [0004]    2. Related Art 
         [0005]    In a portable apparatus equipped with a general-purpose engine such as a portable electric generator, the engine is disposed on a frame or the like with an elastic body such as a vibration-reducing rubber therebetween. 
         [0006]    As an example of the related art concerning such an engine mount structure for an apparatus equipped with an engine, Japanese Unexamined Patent Application Publication No. H11-82043 discloses a portable electric generator in which an engine, an electric generating device, a fuel tank, and the like are attached to a frame made of pipes, and in which a cylindrical vibration-reducing rubber is disposed between a lower portion of the frame and a bottom surface of the engine and a bolt is inserted into an aperture of the vibration-reducing rubber so as to fasten the engine to the frame. 
         [0007]    Recently, it has been becoming increasingly common for housings (casings) of electric generators or the like to be formed as capsule-type structures made of a resin. In an apparatus equipped with an engine and having such a resin casing, for example, the vibration-reducing rubber is disposed on the top surface of a metallic base plate formed by a pressing process, the engine is mounted on the vibration-reducing rubber, and a bolt that protrudes downward from the base plate fastens the casing to the base plate. 
         [0008]    However, in the engine mount structure in which the elastic body protrudes from one side of the base plate and the bolt protrudes from the other side of the base plate, the base plate increases in size in the thickness direction (usually, a vertical direction) and consequently the outer dimensions of the apparatus equipped with the engine increase. 
       SUMMARY OF THE INVENTION 
       [0009]    In view of the above problems, an example of an object of the present invention is to provide an engine mount structure that can be used in an apparatus equipped with an engine and that makes it possible to reduce the size of the apparatus. 
         [0010]    In order to achieve the above object, an aspect of the present invention provides an engine mount structure for an apparatus equipped with an engine, the engine mount structure being configured to mount an engine on a casing made of a resin with an elastic body therebetween. The engine mount structure includes: a base plate arranged so that one side thereof faces the engine and the other side thereof faces the casing; an elastic body made of an elastic material and formed into a cylindrical shape, the elastic body being disposed so as to protrude toward the engine from the base plate and being provided at an end portion thereof on an engine side with a securing member to which the engine is fixed; and a bolt that protrudes toward the casing from the base plate and that couples the casing and the base plate to each other. An area where the bolt is disposed on the base plate is arranged so as to protrude in a stepped shape toward the engine from an area where the elastic body is disposed on the base plate. 
         [0011]    An end portion of the elastic body on a casing side may protrude toward the casing from the base plate and comes into contact with the casing. Ribs may be provided around the elastic body at a contact position between the elastic body and the casing. 
         [0012]    Further, a projection may be provided on the casing at a contact position between the elastic body and the casing so as to be inserted into an aperture of the elastic body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a longitudinal sectional view of an engine mount structure for an apparatus equipped with an engine in accordance with an implementation of the invention; 
           [0014]      FIG. 2A  is a plan view of a base plate in the engine mount structure illustrated in  FIG. 1 , illustrating the base plate to which a vibration-reducing rubber or the like is attached and which is viewed from an engine side; 
           [0015]      FIG. 2B  is a longitudinal sectional view of part of the base plate taken from a line IIB-IIB in  FIG. 2A ; 
           [0016]      FIG. 2C  is an enlarged sectional view of part of the base plate in a circular area IIC in  FIG. 2B ; and 
           [0017]      FIG. 3  is an enlarged sectional view of part of the engine mount structure in an area indicated by an arrow III in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    An implementation of an engine mount structure for an apparatus equipped with an engine (hereinafter merely referred to “an engine mount structure”) according to the present invention will be described with reference to the drawings 
         [0019]    In the implementation of the invention, an apparatus equipped with an engine is a portable engine generator that contains a device such as a general-purpose engine, an electric generator, a fuel tank, and a controller in a casing made of a resin. 
         [0020]    As illustrated in  FIG. 1  through  FIG. 3 , an engine mount structure  100  is used to secure an engine (not illustrated) to the top of a casing base  10 . The engine mount structure  100  includes a base plate  110 , a vibration-reducing rubber (an elastic body)  120 , an engine attachment boss  130 , a welding bolt  140 , and the like. 
         [0021]    The casing base  10  constitutes a lower section (a bottom section) of the resin casing that contains an engine, a fuel tank, an electric generator, a controller, and the like. The casing base  10  is formed integrally by, for example, a molding process in which a resin material is injected into a mold. The casing base  10  includes a bottom portion  11 , a base plate fastening wall  12 , a leg  13 , and the like. 
         [0022]    The bottom portion  11  has a flat plate-like shape, is provided on a lower section of the casing base  10 , and extends in a substantially horizontal direction. An aperture  11   a  is provided in the bottom portion  11  so as to receive a bolt  131  that is used to fasten an engine to the bottom portion  11 . In the implementation illustrated in  FIG. 1 , a pair of apertures  11   a  are provided in the bottom portion  11  and a projection  11   b  is provided around one of the apertures  11   a . The projection  11   b  is provided around the entire periphery of the aperture  11   a  and protrudes upward from the bottom portion  11 . The projection  11   b  is inserted into an aperture of a lower end  122  of the vibration-reducing rubber  120  so as to position the vibration-reducing rubber  120 . 
         [0023]    A casing fastening wall  112  of the base plate  110  is secured to the base plate fastening wall  12 . The base plate fastening wall  12  protrudes in a stepped shape upward (toward an engine side) from the bottom portion  11 . The aperture  12   a  is provided in the base plate fastening wall  12  so as to receive the welding bolt  140 . 
         [0024]    The leg  13  protrudes downward from a bottom surface of the bottom portion  11  so as to support an electric generator. 
         [0025]    The base plate  110  is secured to the casing base  10  and is fixed to the engine with the vibration-reducing rubber  120  therebetween. The base plate  110  is formed integrally by a sheet metal working such as press forming of a steel sheet. The base plate  110  includes a vibration-reducing-rubber holding wall  111 , a casing fastening wall  112 , and the like. In the implementation, a pair of vibration-reducing-rubber holding walls  111  are provided on both sides of the casing fastening wall  112 . 
         [0026]    As illustrated in  FIG. 2A , the base plate  110  is a strip plate that has a bow-shaped structure. The vibration-reducing-rubber holding walls  111  are provided on opposite ends of the base plate  110 . Each vibration-reducing-rubber holding wall  111  has a flat plate-like shape that substantially extends parallel to the bottom portion  11  of the casing base  10 . 
         [0027]    As illustrated in  FIG. 3 , the vibration-reducing-rubber holding wall  111  is spaced apart from and is disposed parallel to the bottom portion  11 . An aperture  111   a  is provided in the vibration-reducing-rubber holding wall  111  so as to receive the vibration-reducing rubber  120 . 
         [0028]    The casing fastening wall  112  is a flat plate that extends substantially parallel to the vibration-reducing-rubber holding wall  111  and that protrudes in a stepped shape toward the engine side (upward in the implementation) from the vibration-reducing-rubber holding wall  111 . As illustrated in  FIG. 3 , the top surface of the casing fastening wall  112  is slightly lower than the top surface of an engine attachment boss  130  so that the casing fastening wall  112  is spaced apart from and opposes a bottom surface of the engine when the wall  112  is attached to the electric generator. In the implementation, the casing fastening wall  112  is provided with, for example, a pair of apertures each of which receives the welding bolt  140 . 
         [0029]    The vibration-reducing rubber  120  is made of a material having viscoelasticity such as a rubber so as to suppress transmission of vibrations between the engine and the base plate  110 . The vibration-reducing rubber  120  has a cylindrical shape with a center axis disposed substantially perpendicular to the vibration-reducing-rubber holding wall  111  of the base plate  110 . The vibration-reducing rubber  120  is a bevel-like elastic body having an upper end  121  which is smaller in diameter than a lower end  122 . 
         [0030]    A peripheral groove  123  is provided on a whole outer periphery of the vicinity of a lower end  122  of the vibration-reducing rubber  120 . A peripheral edge around the aperture  111   a  in the vibration-reducing-rubber holding wall  111  of the base plate  110  is engaged with the peripheral groove  123 . When the vibration-reducing rubber  120  is coupled to the base plate  110  so that an inner peripheral edge around the aperture  111   a  in the vibration-reducing-rubber holding wall  111  is engaged with the peripheral groove  123 , the upper end  121  of the vibration-reducing rubber  120  protrudes upward over the vibration-reducing-rubber holding wall  111  while the lower end  122  of the vibration-reducing rubber  120  protrudes downward over the vibration-reducing-rubber holding wall  111 . 
         [0031]    As illustrated in  FIG. 2C  and  FIG. 3 , ribs  124  and  125  are provided on a bottom surface of the lower end  122  of the vibration-reducing rubber  120 . The rib  124  protrudes downward from an inner peripheral edge on the bottom surface of the lower end  122 . The rib  125  protrudes downward from an outer peripheral edge on the bottom surface of the lower end  122 . The ribs  124  and  125  are provided on the entire periphery of the vibration-reducing rubber  120 . As illustrated in  FIG. 2C , sectional shapes of the ribs  124  and  125  taper from proximal ends (upper ends) to distal ends (lower ends). When the casing base  10  is coupled to the electric generator, the lower ends of the ribs  124  and  125  are pressed onto the bottom portion  11  of the casing base  10 . At this time, the ribs  124  and  125  are elastically compressed in a vertical direction. 
         [0032]    The engine attachment boss  130  is directly coupled to the engine. The engine attachment boss  130  is formed into a disc-like shape by, for example, a sheet metal working and is provided at its center with an aperture for receiving a bolt  131  that is used to fasten the engine to the boss  130 . The engine attachment boss  130  is secured to the upper end  121  of the vibration-reducing rubber  120  by a vulcanized adhesive or the like. The engine attachment boss  130  is fastened to the engine by inserting the bolt  131  into the boss  130  from an under side. 
         [0033]    The welding bolt  140  is used to couple the base plate  110  and the casing base  10  to each other. The welding bolt  140  includes an external thread portion that substantially extends in a vertical direction and a disc-like flange portion provided on an upper end of the external thread portion. When the external thread portion of the welding bolt  140  is inserted downward into the aperture in the casing fastening wall  112  and is made to protrude from the bottom surface of the casing fastening wall  112 , the flange portion of the welding bolt  140  is secured to the casing fastening wall  112  by welding. As illustrated in  FIG. 1 , the welding bolt  140  is inserted into the aperture  12   a  in the base plate fastening wall  12  of the casing base  10  and is fastened on the bottom surface of the casing base  10  by a nut  14  from an under side. 
         [0034]    As described above, the implementation can obtain the following effects. 
         [0035]    (1) Since the casing fastening wall  112  of the base plate  110  protrudes in a stepped shape toward the engine and from the vibration-reducing-rubber holing wall  111 , it is possible to dispose the vibration-reducing rubber  120  and the welding bolt  140  so that they overlap in the thickness direction of the base plate  110 , thereby decreasing the height of the engine mount structure  100  and also decreasing the overall height of the electric generator. Also, in the case where the height of the electric generator is a typical height for electric generators, it is possible to mount an engine having a larger cylinder volume and to exert the same horsepower as an engine having a smaller cylinder volume by using a rotational speed that is lower than that of the engine having the smaller cylinder volume. Accordingly, it is possible to reduce noise while maintaining a level of the horsepower. 
         [0036]    (2) Since the O-ring type ribs  124  and  125  are provided on the lower end  122  of the vibration-reducing rubber  120 , deviations in the relative positions of the bottom portion  11  and the vibration-reducing rubber  120  on account of dimensional tolerances of the base plate  110  and the casing base  10  can be reduced by the ribs  124  and  125  deforming by a certain amount. Consequently, it is possible to prevent the base plate  110  from colliding against the casing base  10  and thereby causing collision noise during operation of the engine when there is a clearance between the vibration-reducing rubber  120  and the casing base  10 , or it is possible to prevent the vibration-reducing rubber  120  from excessively pressing against the casing base  10  and thereby causing deformation or breakage of the casing base  10 . 
         [0037]    (3) Since the casing base  10  is provided around the aperture  11   a  in the bottom portion  11  of the casing base  10  with the projection  11   b  to be inserted into the aperture of the lower end  122  of the vibration-reducing rubber  120 , it is easy to position the base plate  110 , to which the vibration-reducing rubber  120  is attached, with respect to the casing base  10 , thereby improving workability in assembly work and the precision of products. 
       Modified Examples 
       [0038]    It should be noted that the invention is not limited to the implementation described above and that various alterations and modifications fall within the technical scope of the invention. 
         [0039]    For example, shapes, structures, materials, and producing methods of the respective members that constitute the engine mount structure, and numbers and positions of the respective fastening members and elastic bodies are not limited to the above implementation. These items may be altered suitably, as required. 
         [0040]    Also, although the engine mount structure is disposed on a lower part of the engine in the above implementation so that the central axes of the respective bolts and the like extend in a substantially vertical direction, the bolts and the like may be inclined or may support another part of the engine. 
         [0041]    Although an example of the apparatus equipped with the engine is the electric generator in the above implementation, this is not limited. The invention can be applied to any apparatus having a different use.