Patent Publication Number: US-10315320-B2

Title: Electric shaver

Description:
RELATED APPLICATIONS 
     This application is the U.S. National Phase under 35 U.S.C. § 371 of International Application No. PCT/JP2013/007119, filed on Dec. 4, 2013, which in turn claims the benefit of Japanese Application No. 2012-272028, filed on Dec. 13, 2012, the disclosures of which Applications are incorporated by reference herein. 
     TECHNICAL FIELD 
     The present invention relates to an electric shaver. 
     BACKGROUND ART 
     Patent Document 1 discloses an example of an electric shaver. The electric shaver in Patent Document 1 includes a driving unit, an outer blade, and an inner blade.  FIG. 27  illustrates an electric shaver  1000  of Patent Document 1. The driving unit is not shown in  FIG. 27 . 
     The electric shaver  1000  includes an outer blade  1010  and an inner blade  1020 . The outer blade  1010  is pressed against a skin  1030 . The outer blade  1010  includes an outer blade hole  1011 . Facial hair  1040  growing on the skin  1030  enters the outer blade hole  1011 . The inner blade  1020  is positioned in the outer blade  1010 . The inner blade  1020  is driven by the driving unit to move back and forth in a sideward direction of the outer blade  1010 . The inner blade  1020  includes an inner blade hole  1021 . The inner blade  1020  cuts the facial hair  1040  drawn into the inner blade hole  1021  through the outer blade hole  1011 . 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese National Phase Laid-Open Patent Publication No. 2009-502278 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     The skin  1030  may enter the inner blade hole  1021  through the outer blade hole  1011 . The skin  1030  drawn into the inner blade hole  1021  is caught between the outer blade  1010  and the inner blade  1020  when the inner blade  1020  moves back and forth relative to the outer blade  1010 . This irritates the skin  1030 . The same problem occurs when using a rotary electric shaver. 
     It is an object of the present invention to provide an electric shaver that is less likely to irritate the skin. 
     Means for Solving the Problems 
     One aspect of the present invention is an electric shaver including an outer blade, an inner blade, an inner blade joint component, and a skin guard. The outer blade includes an outer blade hole. The inner blade includes an inner blade main body wall, a plurality of blade pieces, an inner blade hole, and an inner blade internal space. The inner blade rotates or moves back and forth relative to the outer blade to cut hair drawn in through the outer blade hole. The inner blade main body wall is coupled to the inner blade joint component. The inner blade internal space is surrounded by the inner blade main body wall and the plurality of blade pieces. The skin guard is located in the inner blade internal space at a position corresponding to the inner blade hole, and the skin guard comes into contact with the skin that enters the inner blade internal space through the inner blade hole. 
     The skin guard is formed in the inner blade internal space at a position corresponding to the inner blade hole. The skin guard comes into contact with the skin that enters the inner blade internal space through the inner blade hole. This restricts entry of the skin into the inner blade internal space through the inner blade hole or reduces the amount of skin that enters the inner blade hole. Thus, an electric shaver that is less likely to irritate the skin can be provided. 
     In one embodiment, the skin guard includes a guard base and a guard contact portion. The guard base is coupled to the inner blade joint component or the inner blade main body wall and supports the guard contact portion. The guard contact portion is shaped to extend toward the inner blade hole and is located closer to the inner blade internal space than a distal end of the inner blade or is located between the outer blade and the distal end of the inner blade. 
     In one embodiment, the guard contact portion includes a portion open at an inner blade hole side. 
     In one embodiment, the skin guard includes a guard elastic portion. The guard elastic portion is located between the guard base and the guard contact portion, the guard elastic portion is supported by the guard base, and the guard elastic portion supports the guard contact portion. 
     In one embodiment, the guard contact portion is formed from an elastic material. 
     In one embodiment, suspension force of the skin guard is larger than suspension force of the outer blade and suspension force of the inner blade. 
     In one embodiment, the electric shaver further includes at least one of a skin-entry amount detector and a pressing force detector, and a control unit. The skin-entry amount detector detects a skin-entry amount indicating an amount of the skin that is drawn into the inner blade hole through the outer blade hole, and the skin-entry amount detector provides the control unit with a skin-entry amount detection signal corresponding to the detected skin-entry amount. The pressing force detector detects pressing force indicating pressure applied to the outer blade when the outer blade comes into contact with the skin, and the pressing force detector provides the control unit with a pressure detection signal corresponding to the detected pressing force. The control unit moves a distal end of the skin guard toward the inner blade hole in accordance with at least one of the skin-entry amount detection signal that indicates an increase in the skin-entry amount and the pressure detection signal that indicates an increase in the pressing force. 
     In one embodiment, the electric shaver further includes an oscillator that oscillates the skin guard. 
     In one embodiment, the skin guard includes a rotating portion that rotates when contacting the skin. 
     In one embodiment, the skin guard is located in the inner blade internal space at a position corresponding to at least two of the plurality of inner blade holes. 
     In one embodiment, the inner blade includes a longitudinal high pressure portion, which contacts the skin with a high pressure, and a longitudinal low pressure portion, which contacts the skin with a lower pressure than the longitudinal high pressure portion, in a longitudinal direction of the inner blade joint component. The skin guard is located in the inner blade internal space at a position corresponding to the longitudinal high pressure portion. 
     In one embodiment, the skin guard is one of a plurality of skin guards arranged in a lateral direction of the inner blade joint component in the inner blade internal space. 
     In one embodiment, the inner blade includes a lateral high pressure portion, which contacts the skin with a high pressure, and a lateral low pressure portion, which contacts the skin with a lower pressure than the lateral high pressure portion, in a lateral direction of the inner blade joint component. The skin guard is located in the inner blade internal space at a position corresponding to the lateral high pressure portion. 
     In one embodiment, the skin guard is similar in shape to the inner blade. 
     In one embodiment, the skin guard is formed integrally with the inner blade. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of an electric shaver according to a first embodiment. 
         FIG. 2  is a plan view of an inner blade unit according to the first embodiment. 
         FIG. 3  is a cross-sectional view taken along a line D 3 -D 3  in  FIG. 2 . 
         FIG. 4A  is a cross-sectional view illustrating a state in which skin and facial hair have entered an inner blade internal space in the inner blade unit of the first embodiment, and  FIG. 4B  is a cross-sectional view illustrating a state in which the inner blade is cutting the facial hair. 
         FIG. 5  is a cross-sectional view of an inner blade unit according to a second embodiment. 
         FIG. 6  is a diagram related to the inner blade unit according to the second embodiment, and is a cross-sectional view illustrating a state in which the skin and the facial hair have entered the inner blade internal space. 
         FIG. 7  is a cross-sectional view of an inner blade unit and a control unit according to a third embodiment. 
         FIG. 8  is a cross-sectional view of the inner blade unit and the control unit according to the third embodiment. 
         FIG. 9  is a cross-sectional view of an inner blade unit and a control unit according to a fourth embodiment. 
         FIG. 10  is a diagram related to the inner blade unit and the control unit according to the fourth embodiment, and illustrates a state in which an outer blade is pressed against the skin. 
         FIG. 11  is a cross-sectional view of an inner blade unit and an oscillator according to a fifth embodiment. 
         FIG. 12  is a diagram related to the inner blade unit and the oscillator according to the fifth embodiment, and is a cross-sectional view illustrating a state in which a skin guard is oscillating. 
         FIG. 13  is a plan view of an inner blade unit according to a sixth embodiment. 
         FIG. 14  is a cross-sectional view taken along a line D 14 -D 14  in  FIG. 13 . 
         FIG. 15  is a plan view of an inner blade unit according to a seventh embodiment. 
         FIG. 16  is a cross-sectional view taken along a line D 16 -D 16  in  FIG. 15 . 
         FIG. 17  is a front view of an inner blade unit according to an eighth embodiment. 
         FIG. 18  is a front view of an inner blade unit and an outer blade according to a ninth embodiment. 
         FIG. 19  is a front view of an inner blade unit and an outer blade according to a tenth embodiment. 
         FIG. 20  is a front view of an inner blade unit according to an eleventh embodiment. 
         FIG. 21  is a cross-sectional view taken along a line D 21 -D 21  in  FIG. 20 . 
         FIG. 22  is a cross-sectional view taken along a line D 22 -D 22  in  FIG. 21 . 
         FIG. 23  is a perspective view of an inner blade unit according to a twelfth embodiment. 
         FIG. 24  is a plan view of an inner blade unit according to a thirteenth embodiment. 
         FIG. 25  is a front view of an inner blade unit according to another embodiment. 
         FIG. 26  is a front view of an inner blade unit according to yet another embodiment. 
         FIG. 27  is a cross-sectional view of conventional inner and outer blades. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment 
     A configuration of an electric shaver  1  will now be described with reference to  FIG. 1 . 
     The electric shaver  1  includes a shaver main body  10 , an outer blade unit  20 , and two inner blade units  30 . The electric shaver  1  is formed as a reciprocating electric shaver in which the inner blade unit  30  moves back and forth relative to the outer blade unit  20 . 
     The shaver main body  10  includes a grip  11 , a head  12 , a driving unit  13 , and a power switch  14 . The shaver main body  10  includes a main body front surface  10 A, a main body back surface  10 B, a main body right surface  10 C, and a main body left surface  10 D. A main body longitudinal direction, a main body sideward direction orthogonal to the main body longitudinal direction, and a main body depth direction orthogonal to the main body longitudinal direction and the main body sideward direction are defined based on the shaver main body  10 . 
     The main body front surface  10 A faces a user when the user uses the electric shaver  1 . The main body back surface  10 B is on the opposite side of the main body front surface  10 A in the main body depth direction. The main body right surface  10 C is on the right side of the main body front surface  10 A in the main body sideward direction. The main body left surface  10 D is on the left side of the main body front surface  10 A in the main body sideward direction. 
     The head  12  is coupled to the grip  11 . The driving unit  13  is accommodated in the grip  11  and the head  12 . The driving unit  13  partially protrudes out of the head  12 . The driving unit  13  moves the inner blade unit  30  back and forth in the main body sideward direction. The power switch  14  is formed on the main body front surface  10 A of the grip  11 . 
     The outer blade unit  20  includes an outer blade  21  and an outer blade casing  22 . The outer blade  21  is coupled to the outer blade casing  22 . The outer blade  21  has a suspension function for absorbing pressure applied in the main body longitudinal direction. The outer blade  21  includes outer blade holes  21 A. Facial hair of the user enters a space in the outer blade casing  22  through the outer blade holes  21 A. The outer blade holes  21 A are formed over the entire outer blade  21 . The outer blade casing  22  is coupled to the shaver main body  10 . 
     The inner blade unit  30  includes an inner blade  40 , an inner blade joint component  50 , and a skin guard  60  (see  FIG. 2 ). The inner blade joint component  50  couples the inner blade unit  30  to the driving unit  13 . The inner blade unit  30  moves back and forth relative to the outer blade unit  20  to cut the hair. The inner blade  40  includes an inner blade main body wall  41 . The inner blade main body wall  41  is coupled to the inner blade joint component  50 . The inner blade  40  has a suspension function for absorbing pressure applied in the main body longitudinal direction. 
     The configuration of the inner blade unit  30  will now be described in detail with reference to  FIG. 2 .  FIG. 2  schematically illustrates a portion of adjacent blade pieces  42  in the inner blade unit  30 . 
     The inner blade  40  is formed from a metal material. The inner blade  40  includes the inner blade main body wall  41  and a plurality of the blade pieces  42 . An inner blade hole  43  is formed between adjacent blade pieces  42 . The inner blade main body wall  41  and the plurality of blade pieces  42  are integrally formed from the same material. The inner blade  40  moves back and forth together with the inner blade joint component  50  in the main body sideward direction to cut the facial hair. 
     The plurality of blade pieces  42  are arranged in the main body sideward direction. The inner blade main body wall  41  and the plurality of blade pieces  42  form an inner blade internal space  44 . Facial hair enters the inner blade hole  43 . The inner blade joint component  50  is formed from a resin material. 
     The configuration of the skin guard  60  will now be described with reference to  FIG. 3 . 
     The skin guard  60  is formed from a resin material. Entrance of the skin into the inner blade internal space  44  is restricted when the skin guard  60  comes into contact with the skin through the inner blade hole  43  (hereinafter, referred to as “skin entry restriction function”). The skin guard  60  is located in the inner blade internal space  44  at a position corresponding to the inner blade hole  43 . In the illustrated example, a plurality of the skin guards  60  are located at positions corresponding to the inner blade holes  43  in the main body sideward direction. The skin guard  60  includes a guard base  61  and a guard contact portion  62 . The guard base  61  and the guard contact portion  62  are integrally formed from the same material. 
     The guard base  61  is coupled to the inner blade joint component  50 . For example, the guard base  61  has a rectangular parallelepiped shape. The guard base  61  supports the guard contact portion  62 . 
     The guard contact portion  62  has a shape that extends from the guard base  61  toward the inner blade hole  43 . The guard contact portion  62  comes into contact with the skin that enters the inner blade internal space  44  through the inner blade hole  43 . The guard contact portion  62  is located toward an inner blade internal space side from a distal end surface  42 A of the blade piece  42 . The guard contact portion  62  includes a plurality of openings  62 A arranged in the main body sideward direction and the main body depth direction. Facial hair enters the inner blade internal space  44  through the plurality of openings  62 A. The plurality of openings  62 A are formed in portions of the guard contact portion  62   s  at the inner blade hole side. 
     The operation of the electric shaver  1  will now be described with reference to  FIG. 1  and  FIG. 4 . 
     As illustrated in  FIG. 4A , the user presses the outer blade  21  against the skin  100 . Facial hair  110  enters the inner blade internal space  44  through the outer blade hole  21 A and the inner blade hole  43 . The skin  100  enters the inner blade hole  43  through the outer blade hole  21 A. At this point, the skin  100  comes into contact with the guard contact portion  62  of the skin guard  60 . The driving unit  13  illustrated in  FIG. 1  moves the inner blade unit  30  back and forth relative to the outer blade unit  20  in the main body direction sideward direction, while the power switch  14  is ON. 
     As illustrated in  FIG. 4B , the blade piece  42  of the inner blade  40  cooperates with the outer blade  21  to catch the facial hair  110  drawn through the outer blade hole  21 A of the outer blade unit  20 . Thus, the facial hair  110  is cut. 
     The electric shaver  1  according to the first embodiment has the following advantages. 
     (1) The skin guard  60  comes into contact with the skin  100  drawn into the inner blade internal space  44  through the inner blade hole  43 . Thus, the skin is prevented from entering the inner blade internal space  44  through the inner blade hole  43  or the amount of skin  100  entering the inner blade hole  43  and the inner blade internal space  44  is reduced. As a result, the electric shaver  1  is less likely to irritate the skin  100 . 
     (2) The guard contact portion  62  is located toward the inner blade internal space side from the distal end surface  42 A of the blade piece  42 . Thus, the blade piece  42  can more efficiently cooperate with the outer blade  21  to cut the facial hair  110 , compared with a configuration in which the distal end surface  42 A of the blade piece  42  is located toward the inner blade internal space side from the guard contact portion  62 . 
     (3) With the guard contact portion  62 , the facial hair  110  can efficiently enter the inner blade internal space  44  through the plurality of openings  62 A. 
     In the example illustrated in  FIG. 3 , the skin guard  60  includes the guard base  61  and the plurality of guard contact portions  62 . A single guard contact portion  62  and a guard base  61 A serving as a part of the guard base  61  supporting the guard contact portion  62  form a skin guard  60 A as a basic element of the skin guard  60 . For example, three skin guards  60 A are arranged in the main body sideward direction. The guard bases  61 A of the adjacent skin guards  60  are coupled with each other to form the guard base  61 . The guard bases  61 A of the plurality of skin guards  60 A are coupled with each other. This forms a single skin guard  60 , which is larger than each skin guard  60 A. 
     Second Embodiment 
     An electric shaver  1  according to a second embodiment differs from the electric shaver  1  according to the first embodiment in the following point but is otherwise the same. The inner blade unit  30  according to the first embodiment includes the skin guard  60  illustrated in  FIG. 3  and the like. The inner blade unit  30  according to the second embodiment includes a skin guard  260  illustrated in  FIG. 5  and the like. Components of the electric shaver  1  according to the second embodiment that are the same as those in the electric shaver  1  according to the first embodiment are denoted with the same reference numerals, and the description thereof is partially or entirely omitted. 
     The configuration of the skin guard  260  according to the second embodiment will now be described with reference to  FIG. 5 . 
     The skin guard  260  has a skin entry restriction function. The skin guard  260  is located in the inner blade internal space  44  at a position corresponding to the inner blade hole  43 . A plurality of the skin guards  260  are formed at positions corresponding to the inner blade holes  43  in the main body sideward direction. The skin guard  260  includes a guard base  261 , a guard contact portion  262 , and a guard elastic portion  263 . The guard base  261  and the guard contact portion  262  of the skin guard  260  are formed from the same material. 
     The guard base  261  is coupled to the inner blade joint component  50 . The guard base  261  is formed from a resin material. The guard base  261  has a rectangular parallelepiped shape. The guard base  261  supports the guard elastic portion  263 . 
     The guard contact portion  262  is formed from a resin material. The guard contact portion  262  has a shape that extends from the guard base  261  toward the inner blade hole  43 . The guard contact portion  262  comes into contact with the skin that enters the inner blade internal space  44  through the inner blade hole  43 . The guard contact portion  262  is located toward the inner blade internal space side from the distal end surface  42 A of the blade piece  42 . The guard contact portion  262  includes a plurality of openings  62 A arranged in the main body longitudinal direction and the main body depth direction. Facial hair enters the inner blade internal space  44  through the plurality of openings  62 A. The plurality of openings  62 A are formed on the inner blade hole side of the guard contact portion  62 . 
     The guard elastic portion  263  is formed from an elastic material. The guard elastic portion  263  is located between the guard base  261  and the guard contact portion  262 . The guard elastic portion  263  is supported by the guard base  261 . The guard elastic portion  263  supports the guard contact portion  262 . Suspension force of the guard elastic portion  263  is larger than suspension force of the inner blade  40  and the outer blade  21 . 
     The operation of the electric shaver  1  according to the second embodiment will now be described with reference to  FIG. 6 . 
     The user presses the outer blade  21  against the skin  100 . At this point, pressure may be unevenly applied to the outer blade  21  depending on how the user presses the outer blade  21 . When local contact occurs, pressing force PA is applied to one outer blade  21  for example. On the other hand, pressing force PB is applied to the other outer blade  21 . The pressing force PB is smaller than the pressing force PA. 
     The facial hair  110  enters the inner blade internal space  44  through the outer blade hole  21 A and the inner blade hole  43 . The skin  100  enters the inner blade hole  43  through the outer blade hole  21 A. At this point, the skin  100  comes into contact with the guard contact portion  262  of the skin guard  260 . A contraction amount of the guard elastic portion  263 , corresponding to the outer blade  21  to which the pressing force PA is applied, is larger than a contraction amount of the guard elastic portion  263 , corresponding to the outer blade  21  to which the pressing force PB is applied. 
     The electric shaver  1  according to the second embodiment has the following advantages in addition to the advantages (1) to (3). 
     (4) The guard elastic portion  263  elastically deforms in accordance with the pressing force from the outer blade  21  to the skin  100 . Thus, the position of the guard contact portion  262  changes in accordance with the pressing force from the outer blade  21  to the skin  100 . Accordingly, contact pressure between the guard contact portion  262  and the skin  100  can be prevented from being uneven, even when local contact occurs. 
     (5) The suspension force of the guard elastic portion  263  is larger than the suspension force of the inner blade  40  and the outer blade  21 . This facilitates the contact between the guard contact portion  262  and the skin  100  drawn into the inner blade hole  43  through the outer blade hole  21 A when the outer blade  21  is pressed against the skin  100 . 
     Third Embodiment 
     An electric shaver  1  according to a third embodiment differs from the electric shaver  1  according to the first embodiment in the following point but is otherwise the same. The inner blade unit  30  according to the first embodiment includes the skin guard  60  illustrated in  FIG. 3  and the like. An inner blade unit  30  according to the third embodiment includes a skin guard  360  illustrated in  FIG. 7  and the like. The electric shaver  1  according to the third embodiment further includes a pressing force detector  370  and a control unit  380  illustrated in  FIG. 7  and the like. Components of the electric shaver  1  according to the third embodiment that are the same as those in the electric shaver  1  according to the first embodiment are denoted with the same reference numerals, and the description thereof is partially or entirely omitted. 
     The configuration of the electric shaver  1  according to the third embodiment will now be described with reference to  FIG. 7 . 
     The electric shaver  1  includes the skin guard  360 , the pressing force detector  370 , and the control unit  380 . 
     The skin guard  360  is formed from a resin material. The skin guard  360  has a skin entry restriction function. The skin guard  360  is located in the inner blade internal space  44  at a position corresponding to the inner blade hole  43 . A plurality of the skin guards  360  are formed at positions corresponding to the inner blade holes  43  in the main body sideward direction. The skin guard  360  includes a guard base  361  and a guard contact portion  362 . The guard base  361  and the guard contact portion  362  are integrally formed from the same material. The skin guard  360  is electrically connected to the control unit  380 . 
     The guard base  361  is coupled to the inner blade joint component  50 . The guard base  361  has a rectangular parallelepiped shape. The guard base  361  supports the guard contact portion  362 . 
     The guard contact portion  362  has a shape that extends from the guard base  361  toward the inner blade hole  43 . The guard contact portion  362  has a configuration in which a distal end can be deformed in the main body longitudinal direction. The guard contact portion  362  comes into contact with the skin that enters the inner blade internal space  44  through the inner blade hole  43 . The guard contact portion  362  is located toward the inner blade internal space from the distal end surface  42 A of the blade piece  42 . The guard contact portion  362  includes a plurality of openings  362 A arranged in the main body longitudinal direction and the main body depth direction. Facial hair enters the inner blade internal space  44  through the plurality of openings  362 A. The plurality of openings  362 A are formed in a portion on the inner blade hole side of the guard contact portion  362 . 
     A pressure sensor is used as the pressing force detector  370 . The pressing force detector  370  detects pressing force PX, and supplies a pressure detection signal corresponding to the detected pressing force PX to the control unit  380 . The pressing force PX indicates pressure applied to the outer blade  21  when the outer blade  21  is pressed against the skin. The pressing force detector  370  is attached to the inner blade joint component  50 . The pressing force detector  370  is electrically connected to the control unit  380 . 
     The control unit  380  performs control so that a position of a distal end of the guard contact portion  362  is moved toward the inner blade hole  43  in accordance with the pressure detection signal indicating an increase in the pressing force PX. The control unit  380  is accommodated in the shaver main body  10 . 
     The operation of the electric shaver  1  according to the third embodiment will now be described with reference to  FIG. 8 . 
     The user presses the outer blade  21  against the skin  100 . When the pressing force PX, applied to the outer blade  21 , increases from initial pressing force PXA to pressing force PXB due to local contact for example, the control unit  380  moves the position of the distal end of the guard contact portion  362  toward the inner blade hole  43 . More specifically, skin pushback force of the skin guard  360  is increased. The skin pushback force is force of the skin guard  360  to push back the skin that enters the inner blade internal space  44  through the outer blade hole  21 A and the inner blade hole  43 . 
     The electric shaver  1  according to the third embodiment has the following advantage in addition to advantages (1) to (3). 
     (6) When the pressing force PX increases, the control unit  380  can change the skin pushback force in accordance with the change in the pressing force PX so that the position of the distal end of the guard contact portion  362  moves toward the inner blade hole  43 . 
     In the example illustrated in  FIG. 7  and  FIG. 8 , the skin guard  360  includes the guard base  361  and the plurality of guard contact portions  362 . A single guard contact portion  362  and a guard base  361 A serving as a part of the guard base  361  supporting the guard contact portion  362  form a skin guard  360 A as a basic element of the skin guard  360 . For example, three skin guards  360 A are arranged in the main body sideward direction. The guard bases  361 A of the adjacent skin guards  360  are coupled with each other to form the guard base  361 . The guard bases  361 A of the plurality of skin guards  360 A are coupled with each other. This forms a single skin guard  360  that is larger than each skin guard  360 A. 
     Fourth Embodiment 
     An electric shaver  1  according to a fourth embodiment differs from the electric shaver  1  according to the third embodiment in the following point but is otherwise the same. The electric shaver  1  according to the third embodiment includes the pressing force detector  370  illustrated in  FIG. 7  and the like. The electric shaver  1  according to the fourth embodiment includes a skin-entry amount detector  470  illustrated in  FIG. 9  and the like. Components of the electric shaver  1  according to the fourth embodiment that are the same as those in the electric shaver  1  according to the third embodiment are denoted with the same reference numerals, and the description thereof is partially or entirely omitted. 
     The configuration of the electric shaver  1  according to the fourth embodiment will now be described with reference to  FIG. 9 . 
     The electric shaver  1  includes the skin-entry amount detector  470  and the control unit  380 . 
     The skin-entry amount detector  470  detects a skin-entry amount and supplies a skin-entry amount detection signal, corresponding to the detected skin-entry amount, to the control unit  380 . The skin-entry amount indicates an amount of the skin that enters the inner blade internal space  44  through the outer blade hole  21 A and the inner blade hole  43 . A reflective photoelectric sensor is used as the skin-entry amount detector  470 . The skin-entry amount detector  470  is attached to the inner blade joint component  50 . The skin-entry amount detector  470  is electrically connected to the control unit  380 . 
     The control unit  380  performs control so that the position of the distal end of the guard contact portion  362  is moved toward the inner blade hole  43  in accordance with the skin-entry amount detection signal indicating an increase in the skin-entry amount. The control unit  380  is accommodated in the shaver main body  10 . 
     The operation of the electric shaver  1  will now be described with reference to  FIG. 10 . 
     The user presses the outer blade  21  against the skin  100 . At this point, pressing force may be unevenly applied to the outer blade  21  when local contact occurs. Thus, the amount of skin entering the inner blade internal space  44  through the outer blade hole  21 A and the inner blade hole  43  changes in accordance with the positions of the outer blade  21  and the inner blade  40 . The skin-entry amount detector  470  irradiates the skin with a predetermined amount of light. The light, radiated from the skin-entry amount detector  470 , reaches the skin  100  to be reflected. The reflected light returns to the skin-entry amount detector  470 . The skin-entry amount detector  470  detects time T between the radiation of the light onto the skin and the returning of the reflected light to the skin-entry amount detector  470 . The control unit  380  determines that the skin-entry amount has increased when the time T is shorter than a predetermined threshold TX. Upon determining that the skin-entry amount has increased, the control unit  380  moves the position of the distal end of the guard contact portion  362  toward the inner blade hole  43 . More specifically, the skin pushback force of the skin guard  360  is increased. 
     The electric shaver  1  according to the fourth embodiment has advantages corresponding to advantages (1) to (3) and (6). 
     Fifth Embodiment 
     An electric shaver  1  according to a fifth embodiment differs from the electric shaver  1  according to the second embodiment in the following point but is otherwise the same. The electric shaver  1  according to the second embodiment includes the skin guard  260  illustrated in  FIG. 5  and the like. The electric shaver  1  according to the fifth embodiment includes an oscillator  500  in addition to the skin guard  260  illustrated in  FIG. 11  and the like. Components of the electric shaver  1  according to the fifth embodiment that are the same as those in the electric shaver  1  according to the second embodiment are denoted with the same reference numerals, and the description thereof is partially or entirely omitted. 
     The configuration of the electric shaver  1  according to the fifth embodiment will now be described with reference to  FIG. 11 . 
     The electric shaver  1  includes the oscillator  500 . The oscillator  500  oscillates the skin guard  260 . The oscillator  500  includes an electric motor  510 , a cam member  520 , and a guide  530 . 
     The electric motor  510  is accommodated in the shaver main body  10 . The electric motor  510  includes an output shaft  511 . The electric motor  510  rotates the output shaft  511 . The output shaft  511  is coupled to a first cam member  521  of the cam member  520 . The cam member  520  includes the first cam member  521  and a second cam member  522 . 
     The first cam member  521  is attached to the inner blade joint component  50 . The second cam member  522  is attached to top of the first cam member  521 . The second cam member  522  supports the guard elastic portion  263 . The second cam member  522  moves back and forth in the main body longitudinal direction when the first cam member  521  rotates. 
     The guide  530  guides the rotation of the first cam member  521 . The guide  530  guides the back and forth movement of the second cam member  522  in the main body longitudinal direction. The guide  530  is attached to the inner blade joint component  50 . 
     The operation of the electric shaver  1  will now be described with reference to  FIG. 12 . 
     The electric motor  510  rotates the output shaft  511 . When the output shaft  511  rotates, the first cam member  521  rotates. When the first cam member  521  rotates, the second cam member  522  moves back and forth in the main body longitudinal direction. Thus, the skin guard  260  oscillates and shakes off the shaved facial hair attached to the skin guard  260 . 
     The electric shaver  1  according to the fifth embodiment has the following advantages, in addition to advantages (1) to (3) and (4). 
     (7) The oscillator  500  oscillates the skin guard  260  and shakes off the shaved facial hair attached to the skin guard  260 . Thus, the facial hair is not interfered with when entering the inner blade internal space  44 . 
     Sixth Embodiment 
     An electric shaver  1  according to a sixth embodiment differs from the electric shaver  1  according to the first embodiment in the following point but is otherwise the same. The electric shaver  1  according to the first embodiment includes the skin guard  60  illustrated in  FIG. 3  and the like. The electric shaver  1  according to the sixth embodiment includes a skin guard  660  illustrated in  FIG. 13  and the like. Components of the electric shaver  1  according to the sixth embodiment that are the same as those in the electric shaver  1  according to the first embodiment are denoted with the same reference numerals, and the description thereof is partially or entirely omitted. 
     The configuration of the skin guard  660  according to the sixth embodiment will now be described with reference to  FIG. 13 . 
     The skin guard  660  has a skin entry restriction function. The skin guard  260  is located in the inner blade internal space  44  at a position corresponding to the inner blade hole  43 . The skin guard  660  includes a rotational shaft  661  and a rotating portion  662 . 
     The rotational shaft  661  is formed from a metal material. The rotational shaft  661  has a shape that extends in the main body sideward direction in the inner blade internal space  44 . The rotational shaft  661  rotationally supports the rotating portion  662 . An end portion (not illustrated) of the rotational shaft  661  is secured to an end portion (not illustrated) of the inner blade joint component  50 . The rotational shaft  661  can be detached from the inner blade joint component  50 . 
     The rotating portion  662  is formed from a resin material. The rotating portion  662  rotates when contacting the skin that enters the inner blade internal space  44  through the inner blade hole  43 . A plurality of the rotating portions  662  are formed at positions corresponding to the inner blade holes  43  in the main body sideward direction. The rotating portion  662  can be detached from the inner blade joint component  50 , together with the rotational shaft  661 . The rotating portion  662  includes a skin contact surface  662 A. The skin contact surface  662 A is located toward the inner blade internal space side from the distal end surface  42 A of the blade piece  42 . 
     The operation of the electric shaver  1  will now be described with reference to  FIG. 14 . 
     The user presses the outer blade  21  against the skin  100 . The skin  100  enters the inner blade internal space  44  through the outer blade hole  21 A and the inner blade hole  43  and comes into contact with the rotating portion  662 . The user changes the positions of the outer blade  21  and the inner blade  40  with respect to the skin  100 , while pressing the outer blade  21  against the skin  100 . The rotating portion  662  rotates while contacting the skin  100  in accordance with the movement of the outer blade  21  and the inner blade  40  relative to the skin  100 . 
     The electric shaver  1  according to the sixth embodiment has the following advantage in addition to advantages (1) to (3). 
     (8) The rotating portion  662  rotates while contacting the skin  100 . This reduces friction between the skin guard  660  and the skin  100 . 
     Seventh Embodiment 
     An electric shaver  1  according to a seventh embodiment differs from the electric shaver  1  according to the first embodiment in the following point but is otherwise the same. The electric shaver  1  according to the first embodiment includes the skin guard  60  illustrated in  FIG. 3  and the like. The electric shaver  1  according to the seventh embodiment includes a skin guard  760  illustrated in  FIG. 15  and the like. Components of the electric shaver  1  according to the seventh embodiment that are the same as those in the electric shaver  1  according to the first embodiment are denoted with the same reference numerals, and the description thereof is partially or entirely omitted. 
     The configuration of the skin guard  760  according to the seventh embodiment will now be described with reference to  FIG. 15  and  FIG. 16 . 
     As illustrated in  FIG. 15  and  FIG. 16 , the skin guard  760  has a skin entry restriction function. The skin guard  760  is located in the inner blade internal space  44  at a position corresponding to the inner blade hole  43 . A plurality of the skin guards  760  are formed at positions corresponding to the inner blade holes  43  in the main body sideward direction. The skin guard  760  includes a guard base  761 , a guard contact portion  762 , and a rotating portion  763 . The guard base  761  and the guard contact portion  762  are integrally formed from the same material. 
     The guard base  761  is coupled to the inner blade joint component  50 . The guard base  761  has a rectangular parallelepiped shape. The guard base  761  supports the guard contact portion  762 . 
     The guard contact portion  762  has a shape that extends toward the inner blade hole  43 . The guard contact portion  762  has a skin entry restriction function. The guard contact portion  762  is located toward the inner blade internal space side from the distal end surface  42 A of the blade piece  42 . 
     The guard contact portion  762  includes an opening  762 A and a distal end recess  762 B. Facial hair enters the inner blade internal space  44  through the opening  762 A. The opening  762 A is formed in a portion on a side of the inner blade hole of the guard contact portion  762 . The distal end recess  762 B rotationally supports the rotating portion  763 . The distal end recess  762 B is formed at a distal end of the guard contact portion  762 . 
     The rotating portion  763  is formed from a resin material. The rotating portion  763  rotates when contacting the skin that enters the inner blade internal space  44  through the inner blade hole  43 . The rotating portion  763  has a spherical shape. A rotating spherical surface  763 A of the rotating portion  763  is located toward the inner blade internal space side from the distal end surface  42 A of the blade piece  42 . 
     The operation of the electric shaver  1  will now be described with reference to  FIG. 16 . 
     The user presses the outer blade  21  against the skin  100 . The skin  100  enters the inner blade internal space  44  through the outer blade hole  21 A and the inner blade hole  43  and comes into contact with the rotating portion  763 . The user changes the positions of the outer blade  21  and the inner blade  40  with respect to the skin  100 , while pressing the outer blade  21  against the skin  100 . The rotating portion  763  rotates while contacting the skin  100  in accordance with the movement of the outer blade  21  and the inner blade  40  relative to the skin  100 . 
     The electric shaver  1  according to the sixth embodiment has advantages (1) to (3) and (8). 
     In the example illustrated in  FIG. 15  and  FIG. 16 , the skin guard  760  includes the guard base  761  and the plurality of guard contact portions  762 . A single guard contact portion  762  and a guard base  761 A serving as a part of the guard base  761  supporting the guard contact portion  762  form a skin guard  760 A as a basic element of the skin guard  760 . For example, three skin guards  760 A are arranged in the main body sideward direction. The guard bases  761 A of the adjacent skin guards  760  are coupled with each other to form the guard base  761 . The guard bases  761 A of the plurality of skin guard  760 A are coupled with each other. This forms a single skin guard  760  that is larger than each skin guard  760 A. Each of the skin guards  760 A are arranged in correspondence with a different inner blade hole  43 . 
     Eighth Embodiment 
     An electric shaver  1  according to an eighth embodiment includes a skin guard  860  illustrated in  FIG. 17  instead of the skin guard  60  according to the first embodiment. Components of the electric shaver  1  according to the eighth embodiment that are the same as those in the electric shaver  1  according to the first embodiment are denoted with the same reference numerals, and the description thereof is partially or entirely omitted. 
     The configuration of the skin guard  860  according to the eighth embodiment will now be described with reference to  FIG. 17 . 
     The skin guard  860  has a skin entry restriction function. The skin guard  860  includes a guard base  861  and a plurality of guard contact portions  862 . A single guard contact portion  862  and a guard base  861 A serving as a part of the guard base  861  supporting the guard contact portion  862  form a skin guard  860 A as a basic element of the skin guard  860 . The skin guards  860 A are arranged in the main body sideward direction. The guard bases  861 A of the adjacent skin guards  860  are coupled with each other to form the guard base  861 . The guard bases  861 A of the plurality of skin guard  860 A are coupled with each other. This forms a single skin guard  860  that is larger than each skin guard  860 A. The plurality of skin guards  860 A are each located to correspond to the corresponding one of the inner blade holes  43  different from each other. The plurality of skin guards  860 A respectively correspond to all the inner blade holes  43 . The position of a distal end surface  862 A of the guard contact portion  862  in the main body longitudinal direction substantially matches the distal end surface  42 A of the blade piece  42 . The electric shaver  1  according to the eighth embodiment has advantages (1) to (3). 
     Ninth Embodiment 
     An electric shaver  1  according to a ninth embodiment includes an inner blade unit  930  illustrated in  FIG. 18  instead of the inner blade unit  30  according to the eighth embodiment. Components of the electric shaver  1  according to the ninth embodiment that are the same as those in the electric shaver  1  according to the eighth embodiment are denoted with the same reference numerals, and the description thereof is partially or entirely omitted. 
     A configuration of the inner blade unit  930  will now be described with reference to  FIG. 18 . 
     The inner blade unit  930  includes a plurality of inner blades  940 . The plurality of inner blades  940  are arranged in the main body sideward direction. The inner blades  940  include inner blade main body walls  941 , blade pieces  942 , and inner blade holes  943 . 
     The inner blade main body wall  941  and the blade piece  942  are integrally formed from the same material. The inner blade main body wall  941  and the blade pieces  942  form an inner blade internal space  944 . The inner blade hole  943  is formed between the adjacent blade pieces  942 . 
     The plurality of inner blades  940  have the inner blade main body walls  941  with heights in the main body longitudinal direction different from each other. The most outer inner blades  940  in the main body sideward direction are the shortest. The center one and the ones around the center one of the plurality of inner blades  940  (hereinafter, referred to as “center inner blade”) are the highest. The inner blade main body wall  941  farther from the outermost inner blade  940  and thus is closer to the center inner blade is higher. The inner blades  940  have different heights as described above. Thus, distal end portions of the inner blades  940  form an arch shape in a front view of the inner blades  940 . An outer blade  921  illustrated with a double-dashed line has the shape of an arch corresponding to the shape of the inner blades  940 . 
     The inner blade unit  930  can be divided into three sections, including a longitudinal high pressure portion RA and two longitudinal low pressure portions RB, in the main body sideward direction. The sections are defined based on the pressure applied to the inner blade  940 , while the electric shaver  1  is being used. The longitudinal high pressure portion RA is an intermediate section in the arch shape, and is likely to receive higher pressure than the longitudinal low pressure portion RB. The longitudinal low pressure portions RB at two positions are sections on both sides of the longitudinal high pressure portion RA in the main body sideward direction, and are likely to receive lower pressure than the longitudinal high pressure portion RA. The pressure relationship is established mainly because the inner blade  940  corresponding to the longitudinal high pressure portion RA has a shape that easily fits the skin. 
     The skin guard  960  includes a guard base  961  and a plurality of guard contact portions  962 . A single guard contact portion  962  and a guard base  961 A serving as a part of the guard base  961  supporting the guard contact portion  962  form a skin guard  960 A as a basic element of the skin guard  960 . The skin guards  960 A are arranged in the main body sideward direction. The guard bases  961 A of the adjacent skin guards  960 A are coupled with each other to form the guard base  961 . The guard bases  961 A of the plurality of skin guard  960 A are coupled with each other. This forms a single skin guard  960  that is larger than each skin guard  960 A. Each of the plurality of skin guards  960 A are arranged in correspondence with a different inner blade holes  943 . 
     The skin guard  960  is located in the inner blade internal space  944  corresponding to the longitudinal high pressure portion RA of the inner blade unit  930 . The plurality of skin guards  960 A respectively correspond to all of the inner blade holes  943  in the longitudinal high pressure portion RA. A position of the distal end surface  962 A of the guard contact portion  962  in the main body longitudinal direction is located toward the inner blade internal space side from a distal end surface  942 A of the blade piece  942  in the longitudinal high pressure portion RA. 
     The electric shaver  1  according to the ninth embodiment provides the following advantage in addition to advantages (1) to (3). 
     (9) Generally, it is difficult to shave the facial hair growing in a portion where the skin is recessed. A portion under the chin is one example of the portion where the skin is recessed. In the electric shaver  1 , the outer blade  921  has the arch shape. Thus, the outer blade  921  easily fits the portion where the skin is recessed, and thus the unshaved facial hair is less likely to remain. On the other hand, the skin is likely to enter the inner blade internal space  944  through the inner blade hole  943  in the longitudinal high pressure portion RA since the outer blade  921  and the inner blade  940  have the arch shape. Thus, the skin may be strongly irritated when the electric shaver does not include the skin guard  960 . The arch shapes of the outer blade  921  and the inner blade  940  facilitates shaving of the facial hair but also increases the risk of strongly irritating the skin. 
     In the electric shaver  1  according to the ninth embodiment, the skin guard  960  is located in the inner blade internal space  944  corresponding to the longitudinal high pressure portion RA. Thus, the skin is less likely to enter the inner blade internal space  944  corresponding to the longitudinal high pressure portion RA. Thus, the configuration of the outer blade  921  and the inner blade  940  improving the shaving performance of the facial hair is achieved, with a low risk of strongly irritating the skin. Accordingly, the advantage of improving shaving performance of the facial hair and the advantage of protecting the skin can be achieved. 
     Tenth Embodiment 
     An electric shaver  1  according to a tenth embodiment includes an inner blade unit  130 A illustrated in  FIG. 19  instead of the inner blade unit  930  according to the ninth embodiment. Components of the electric shaver  1  according to the tenth embodiment that are the same as those in the electric shaver  1  according to the ninth embodiment are denoted with the same reference numerals, and the description thereof is partially or entirely omitted. 
     The configuration of the inner blade unit  130 A will now be described with reference to  FIG. 19 . 
     The inner blade unit  130 A includes a plurality of inner blades  140 A and the skin guard  960 . The plurality of inner blades  140 A are arranged in the main body sideward direction. The inner blades  140 A include inner blade main body walls  141 A, blade pieces  142 A, and inner blade holes  143 A. 
     The inner blade main body wall  141 A and the blade piece  142 A are integrally formed from the same material. The inner blade main body wall  141 A and the blade pieces  142 A form an inner blade internal space  144 A. The inner blade hole  143 A is formed between the adjacent blade pieces  142 A. 
     The inner blades  140 A of the inner blade unit  130 A have substantially the same height in the main body longitudinal direction. With this height relationship among the inner blades  140 A, distal end portions of the inner blades  140 A form a flat shape in the front view of the inner blades  140 A. An outer blade  121 A illustrated with a double-dashed line has a flat shape corresponding to the shape of the inner blades  140 A. 
     The inner blade unit  130 A can be divided in the main body sideward direction into three portions that include a longitudinal high pressure portion RAA and two longitudinal low pressure portions RBB. The sections are defined based on the pressure applied to the inner blade  140 A, while the electric shaver  1  is being used. In the electric shaver  1 , due to the shape of the inner blades  140 A, an end portion of the outer blade  121 A is frequently used by being pressed against the portion where the skin is recessed. Thus, the two longitudinal high pressure portions RAA are likely to receive higher pressure than the longitudinal low pressure portion RBB. The longitudinal low pressure portion RBB is located between the two longitudinal high pressure portions RAA and is likely to receive lower pressure than the longitudinal high pressure portions RAA. 
     The skin guard  960  is located in the inner blade internal space  144 A corresponding to the longitudinal high pressure portions RAA of the inner blade unit  130 A. The plurality of skin guards  960 A respectively correspond to all of the inner blade holes  143 A in the longitudinal high pressure portion RAA. The position of the distal end surface  962 A of the guard contact portion  962  in the main body longitudinal direction is slightly lower than the position of a distal end surface  142 X of the blade piece  142 A in the longitudinal high pressure portion RAA. 
     The electric shaver  1  according to the tenth embodiment has the following advantage in addition to advantages (1) to (3). 
     (10) In the electric shaver  1 , the skin guards  960  are located in the inner blade internal spaces  144 A corresponding to the inner blade holes  143 A in the longitudinal high pressure portions RAA. Thus, the skin is less likely to enter the inner blade internal space  144 A corresponding to the longitudinal high pressure portion RAA. Accordingly, the skin is less likely to be strongly irritated. 
     Eleventh Embodiment 
     An electric shaver  1  according to an eleventh embodiment includes a skin guard  160 B illustrated in  FIG. 20  and the like instead of the skin guard  860  according to the eighth embodiment. Components of the electric shaver  1  according to the eleventh embodiment that are the same as those in the electric shaver  1  according to the eighth embodiment are denoted with the same reference numerals, and the description thereof is partially or entirely omitted. 
     The configuration of the skin guard  160 B will now be described with reference to  FIG. 20  to  FIG. 22 . 
     As illustrated in  FIG. 20 , the electric shaver  1  includes a plurality of skin guards  160 B. The plurality of skin guards  160 B are arranged in the main body sideward direction. The plurality of skin guards  160 B are each located in the inner blade internal space  44  corresponding to the corresponding one of the inner blade holes  43  different from each other. The plurality of skin guards  160 B respectively correspond to all of the inner blade holes  43 . 
     As illustrated in  FIG. 21 , the skin guard  160 B includes a first skin guard  161 B and a plurality of second skin guards  162 B. The first skin guard  161 B may have an arch shape. For example, three second skin guards  162 B are arranged in a lateral direction of the inner blade joint component  50 , that is, in the main body depth direction. The second skin guard  162 B and the first skin guard  161 B are integrally formed from the same material. The second skin guard  162 B protrudes in a direction opposite to the inner blade joint component  50  from a curved portion of the first skin guard  161 B. The second skin guard  162 B has a protruding shape. A distal end of the second skin guard  162 B has a semispherical shape. 
     The blade piece  42  can be divided in the main body depth direction into three portions, namely, a lateral high pressure portion RZA and two lateral low pressure portions RZB. The sections are defined based on the pressure applied to the inner blade  40 , while the electric shaver  1  is being used. The lateral high pressure portion RZA is an intermediate section of the blade piece  42 , and is likely to receive higher pressure than the lateral low pressure portion RZB. The lateral low pressure portions RZB at two positions are sections on both sides of the lateral high pressure portion RZA in the main body sideward direction, and are likely to receive lower pressure than the lateral high pressure portion RZA. The pressure relationship is established mainly because the lateral high pressure portion RZA has a shape that easily fits the skin. 
     As illustrated in  FIG. 21 , the first skin guard  161 B is disposed in the lateral high pressure portion RZA between one of the lateral low pressure portions RZB and the other lateral low pressure portion RZB, in the main body depth direction. The plurality of second skin guards  162 B are located at portions corresponding to the lateral high pressure portion RZA in the main body sideward direction. When an outer blade (not illustrated) is pressed against the skin, the skin is more likely to enter the inner blade hole  43  corresponding to the lateral high pressure portion RZA than the inner blade hole  43  corresponding to the lateral low pressure portion RZB. In the electric shaver  1 , the skin guard  160 B is configured based on such a behavior of the skin. The second skin guard  162 B is located closer to an opening portion of the inner blade hole  43  than the first skin guard  161 B. This effectively prevents the skin from entering the inner blade internal space  44 . Thus, the second skin guard  162 B is located in the portion corresponding to the lateral high pressure portion RZA, and the skin is much less likely to enter the inner blade internal space  44  compared with when the second skin guard  162 B is not provided. 
     Sizes of the first skin guard  161 B and the second skin guard  162 B are described with reference to  FIG. 22 . 
     A width of the second skin guard  162 B is shorter than a width of the first skin guard  161 B. The width of the first skin guard  161 B is a distance from one end surface to the other end surface of the first skin guard  161 B. The width of the second skin guard  162 B is a distance from one end surface to the other end surface of the second skin guard  162 B. 
     The effect of the skin entry restriction function of each of the skin guards  161 B,  162 B mainly depends on a width XA of the distal end surface of the second skin guard  162 B. The skin entry restriction function becomes more effective as the width XA increases. When the width XA is within a predetermined width range, a preferable skin entry restriction function is ensured. Thus, the width XA of the distal end surface of the second skin guard  162 B is set to be within the predetermined width range. 
     Facial hair entrance easiness is one aspect indicating facial hair shaving easiness. The facial hair entrance easiness indicates how easily the facial hair enters the inner blade internal space  44 . A distance XB, between an end surface of the second skin guard  162 B and the outer blade  21 , largely affects the facial hair entrance easiness. The facial hair entrance easiness increases as the distance XB increases. The favorable facial hair entrance easiness is ensured when the distance XB is within the predetermined distance range. Thus, the distance XB is set to be within the predetermined distance range. 
     The width XA and the distance XB affect each other. Thus, the width XA and the distance XB are preferably set based on the skin entry restriction function and the facial hair entrance easiness. The skin guard  160 B has the width XA ensuring the preferably skin entry restriction function and the distance XB ensuring the preferable facial hair entrance easiness. When the width of the first skin guard  161 B is assumed to be the width XA from a distal end portion to a base end portion, the first skin guard  161 B may have a relatively low rigidity. Thus, in the assumed configuration, the maximum external load that can be received by the first skin guard  161 B is relatively small. 
     Thus, the first skin guard  161 B has a configuration of ensuring a preferable rigidity in addition to the configuration of ensuring the preferable skin entry restriction function and facial hair entrance easiness. If the first skin guard  161 B receives a load when contacting the skin, the first skin guard  161 B elastically deforms with the basal portion functioning as a fulcrum point. Thus, the first skin guard  161 B is less likely to be damaged when the rigidity of the basal portion of the first skin guard  161 B is increased. 
     The distance XB between one end surface of the second skin guard  162 B and the outer blade  21  is greater than or equal to a predetermined distance. For example, the predetermined distance indicates a diameter of the facial hair that differs among persons. In the second skin guard  162 B, a typical diameter of the facial hair is selected as the predetermined distance, and the distance XB is determined based on the predetermined distance thus selected. The facial hair is likely to enter the inner blade internal space  44  due to the size relationship between the second skin guard  162 B and the outer blade hole  21 A of the outer blade  21 . 
     A gap space SA is formed between the first skin guard  161 B and the inner blade main body wall  41 . An extra space SB is formed between the second skin guard  162 B and the blade piece  42 . A width of the gap space SA is defined by a distance between the end surface of the first skin guard  161 B and the inner blade main body wall  41 . A width of the extra space SB is defined by a distance between the end surface of the second skin guard  162 B and the blade piece  42 . The width of the extra space SB is longer than the width of the gap space SA. The width of the extra space SB is set to be such a length that the cut facial hair is less likely to be jammed between the second skin guard  162 B and the blade piece  42 . 
     The electric shaver  1  according to the eleventh embodiment has the following advantage in addition to advantages (1) to (3). 
     (11) In the electric shaver  1 , the second skin guard  162 B is located in the inner blade internal space  44  corresponding to the inner blade hole  43  in the lateral high pressure portion RZA. Thus, the skin is less likely to enter the inner blade internal space  44  corresponding to the lateral high pressure portion RZA. Accordingly, the skin is less likely to be strongly irritated. 
     Twelfth Embodiment 
     An electric shaver  1  according to a twelfth embodiment includes a skin guard  160 C illustrated in  FIG. 23  instead of the skin guard  60  according to the first embodiment. Components of the electric shaver  1  according to the twelfth embodiment that are the same as those in the electric shaver  1  according to the first embodiment are denoted with the same reference numerals, and the description thereof is partially or entirely omitted. 
     The configuration of the skin guard  160 C will now be described with reference to  FIG. 23 . In  FIG. 23 , only a part of the inner blade unit  30  in the main body sideward direction is illustrated for the sake of description. 
     The skin guard  160 C is located at a position in the inner blade internal space  44  corresponding to the inner blade hole  43 . The skin guards  160 C are located at positions respectively corresponding to the inner blade holes  43  in the main body sideward direction, that is, the longitudinal direction of the inner blade joint component  50 . The skin guard  160 C includes a guard base  161 C and a guard contact portion  162 C. 
     The guard base  161 C, the inner blade joint component  50 , and the inner blade  40  are integrally formed from the same material. The guard base  161 C has a shape that is similar to that of the inner blade  40 . For example, the guard base  161 C has an arch shape. 
     The guard contact portion  162 C and the guard base  161 C are integrally formed from the same material. The guard contact portion  162 C has a shape that extends from the guard base  161 C toward the inner blade hole  43 . The guard contact portion  162 C comes into contact with the skin that enters the inner blade internal space  44  through the inner blade hole  43 . A distal end surface  162 CX of the guard contact portion  162 C is located toward the inner blade internal space side from the distal end surface  42 A of the blade piece  42  in the main body longitudinal direction. 
     The electric shaver  1  according to the twelfth embodiment has the following advantages in addition to advantages (1) to (3). 
     (12) The shape of the guard base  161 C is similar to that of the inner blade  40 . Thus, the distal end surface  162 CX of the guard contact portion  162 C can be more accurately positioned with respect to the distal end surface  42 A of the blade piece  42  in the main body longitudinal direction. 
     (13) The guard base  161 C, the inner blade joint component  50 , and the inner blade  40  are integrally formed from the same material. Thus, the distal end surface  162 CX of the guard contact portion  162 C can be more accurately positioned with respect to the distal end surface  42 A of the blade piece  42  in the main body longitudinal direction. 
     Thirteenth Embodiment 
     An electric shaver  1  according to a thirteenth embodiment includes an inner blade unit  130 D illustrated in  FIG. 24  instead of the inner blade unit  30  according to the first embodiment. Components of the electric shaver  1  according to the thirteenth embodiment that are the same as those in the electric shaver  1  according to the first embodiment are denoted with the same reference numerals, and the description thereof is partially or entirely omitted. 
     The configuration of the inner blade unit  130 D will now be described with reference to  FIG. 24 . 
     The inner blade unit  130 D includes an inner blade  140 D and a skin guard  160 D. The inner blade unit  130 D has a rotary configuration in which the inner blade  140 D rotates with respect to an outer blade (not illustrated) to cut facial hair drawn through the outer blade. A plurality of the inner blades  140 D are spaced apart in a circumference direction of a circular inner blade joint component  150 D. 
     The skin guard  160 D has a skin entry restriction function. The skin guard  160 D includes a guard base  161 D and a plurality of guard contact portions  162 D. A single guard contact portion  162 D and a guard base  161 DA serving as a part of the guard base  161 D supporting the guard contact portion  162 D form a skin guard  160 DA as a basic element of the skin guard  160 D. The skin guards  160 DA are arranged in the circumference direction and a radial direction. The guard bases  161 DA of the adjacent skin guards  160 DA are coupled with each other to form the guard base  161 D. The guard bases  161 DA of the plurality of skin guards  160 DA are coupled with each other. This forms a single skin guard  160 D that is larger than each skin guard  160 DA. Each of the plurality of skin guards  160 DA are located in correspondence with a different inner blade hole  143 D. The plurality of skin guards  160 DA respectively correspond to all of the inner blade holes  143 D. 
     For example, three guard contact portions  162 D are arranged in the radial direction in each inner blade internal space  144 D. The circumference direction of the inner blade unit  130 D corresponds to the main body sideward direction of the reciprocating inner blade unit  30  (see  FIG. 1  and the like). The radial direction of the inner blade unit  130 D corresponds to the main body depth direction of the reciprocating inner blade unit  30  (see  FIG. 1  and the like). 
     The electric shaver  1  according to the thirteenth embodiment provides advantages (1) to (3). 
     Other Embodiments 
     The disclosed electric shaver includes other embodiments that differ from the first embodiment to the thirteenth embodiment. The other embodiments include the following modifications, for example. The modifications and the embodiments can be combined with each other as long as there is no technical contradiction. 
     The guard base  61  according to the first embodiment is coupled to the inner blade joint component  50 . However, the configuration of the guard base  61  is not limited to the example in the first embodiment. A guard base according to a modification is coupled to the inner blade main body wall  41 . 
     The skin guard  60  according to the first embodiment has the configuration in which the guard base  61  and the guard contact portion  62  are integrally formed from the same material. The configuration of the skin guard  60  is not limited to the example in the first embodiment. The skin guard according to a modification has a configuration in which a guard base and a guard contact portion are integrally formed with the same elastic material. 
     The skin guard  60  according to the first embodiment has the guard contact portion  62  that comes into contact with the skin  100 . However, the configuration of the skin guard  60  is not limited to the example in the first embodiment. A skin guard according to a modification blows air to the skin  100  that has entered through the outer blade hole  21 A and the inner blade hole  43  to prevent the skin  100  from entering the inner blade internal space  44 . 
     The guard base  61  according to the first embodiment, the guard base  361  according to the third embodiment, and the guard base  761  according to the seventh embodiment are coupled to the inner blade joint component  50 . However, the configuration of the guard base is not limited to the example in the first embodiment, the third embodiment, and the seventh embodiment. A guard base according to a modification and the inner blade joint component  50  are integrally formed. 
     The guard base  61  according to the first embodiment, the guard base  261  according to the second embodiment, the guard base  361  according to the third embodiment, and the guard base  761  according to the seventh embodiment have the rectangular parallelepiped shape. However, the shape of the guard base is not limited to the example in the first embodiment, the second embodiment, the third embodiment, and the seventh embodiment. A guard base according to a modification has any shape such as a cube. 
     The guard contact portion  62  according to the first embodiment, the guard contact portion  262  according to the second embodiment, the guard contact portion  362  according to the third embodiment, the rotating portion  662  according to the sixth embodiment, and the rotating portion  763  according to the seventh embodiment are located toward the inner blade internal space side from the distal end surface  42 A of the blade piece  42 . However, the configurations of the guard base and the rotating portion are not limited to the example in the first embodiment, the second embodiment, the third embodiment, the sixth embodiment, and the seventh embodiment. A guard base and a rotating portion according to a modification are positioned on the same plane as the distal end surface  42 A of the blade piece  42 . 
     The electric shaver  1  according to the third embodiment includes the pressing force detector  370 . However, the configuration of the electric shaver  1  is not limited to the configuration exemplified in the third embodiment. An electric shaver  1  according to a modification includes the skin-entry amount detector  470  according to the fourth embodiment in addition to the pressing force detector  370 . A control unit of the electric shaver according to the modification moves the position of the distal end of the guard contact portion  362  toward the inner blade hole  43 , when at least one of the skin-entry amount and the pressing force increases. More specifically, the skin pushback force of the skin guard  360  is increased. 
     The pressure sensor is used as the pressing force detector  370  according to the third embodiment. However, the configuration of the pressing force detector  370  is not limited to the configuration exemplified in the third embodiment. A strain gauge is used as the pressing force detector  370  according to a modification. 
     The oscillator  500  according to the fifth embodiment oscillates the skin guard  260  in the main body longitudinal direction. However, the configuration of the oscillator  500  is not limited to the configuration exemplified in the fifth embodiment. An oscillator according to a modification oscillates the skin guard  260  in at least one of the main body sideward direction and the main body depth direction. 
     The skin guard  660  according to the sixth embodiment includes the rotational shaft  661 . The rotational shaft  661  has a shape that extends in the main body sideward direction in the inner blade internal space  44 . However, the configuration of the rotational shaft  661  is not limited to the configuration exemplified in the sixth embodiment. A skin guard according to a modification has a rotational shaft extending in the main body depth direction in the inner blade internal space  44 . 
     The rotating portion  662  according to the sixth embodiment and the rotating portion  763  according to the seventh embodiment are formed from a resin material. The configuration of the rotating portion is not limited to the example in the sixth embodiment and the seventh embodiment. A rotating portion according to a modification is formed from a metal material. 
     The skin guards  860 A are preferably located at positions respectively corresponding to all the inner blade holes  43  in the inner blade internal spaces  44 , as in the eighth embodiment. However, the positions at which the skin guards  860 A are located are not limited to the configuration exemplified in the eighth embodiment. The skin guard  860 A may not be located at a position corresponding to some of the inner blade holes  43  in the inner blade internal space  44  as in modifications illustrated in  FIG. 25  and  FIG. 26 . 
     In the skin guard  860 A according to the eighth embodiment, the position of the distal end surface  862 A of the guard contact portion  862  in the main body longitudinal direction substantially matches the position of the distal end surface  42 A of the blade piece  42 . However, the position of the distal end surface  862 A is not limited to the position exemplified in the embodiment. A distal end surface of a contact portion guard according to a modification is located between the distal end surface  42 A of the inner blade  40  and the outer blade  21 . 
     Generally, when curly facial hair with a bent distal end enters an outer blade hole (not illustrated), the distal end may not reach the inner blade hole  43 . In the modification, the distal end surface of the contact portion guard is located between the distal end surface  42 A of the inner blade  40  and the outer blade  21 , and thus the distal end of the curly facial hair may come into contact with the guard contact portion. Thus, the guard contact portion can straighten the facial hair. Thus, the distal end of the curly facial hair can enter the inner blade hole  43 . All things considered, the shaving performance of the electric shaver  1  can be improved. 
     The inner blade units  30  according to the first embodiment to the twelfth embodiment move back and forth relative to the outer blade unit  20  in the main body sideward direction. However, the configuration of the inner blade unit  30  is not limited to the configurations exemplified in the first embodiment to the seventh embodiment. An inner blade unit according to a modification rotates relative to the outer blade unit  20 . More specifically, an electric shaver according to a modification has a configuration of what may be referred to as a rotary electric shaver. 
     The electric shavers  1  according to the first embodiment to the thirteenth embodiment cut the facial hair. However, an object to be cut by the electric shaver  1  is not limited to the facial hair. An electric shaver according to a modification cuts various types of hair including the facial hair. 
     The electric shavers  1  according to the first embodiment to the twelfth embodiment each include two inner blade units. The number of inner blade units is not limited to the example in the first embodiment to the twelfth embodiment. An electric shaver according to a modification includes one or three or more inner blade units. 
     DESCRIPTION OF REFERENCE CHARACTERS 
       1  . . . electric shaver,  10  . . . shaver main body,  10 A . . . main body front surface,  10 B . . . main body back surface,  10 C . . . main body right surface,  10 D . . . main body left surface,  11  . . . grip,  12  . . . head,  13  . . . oscillation unit,  14  . . . power switch,  20  . . . outer blade unit,  21  . . . outer blade,  21 A . . . outer blade hole,  22  . . . outer blade casing,  30  . . . inner blade unit,  40  . . . inner blade,  41  . . . inner blade main body wall,  42  . . . blade piece,  42 A . . . distal end surface,  43  . . . inner blade hole,  44  . . . inner blade internal space,  50  . . . inner blade joint component,  60  . . . skin guard  60 A . . . skin guard,  61  . . . guard base,  61 A . . . guard base,  62  . . . guard contact portion,  62 A . . . openings,  100  . . . skin,  110  . . . facial hair,  260  . . . skin guard,  261  . . . guard base,  262  . . . guard contact portion,  262 A . . . openings,  263  . . . guard elastic portion,  360  . . . skin guard,  361  . . . guard base,  362  . . . guard contact portion,  362 A . . . openings,  370  . . . pressing force detector,  380  . . . control unit,  470  . . . skin-entry amount detector,  500  . . . oscillator,  510  . . . electric motor,  511  . . . output shaft,  520  . . . cam member,  521  . . . first cam member,  522  . . . second cam member,  530  . . . guide,  660  . . . skin guard,  661  . . . rotational shaft,  662  . . . rotating portion,  760  . . . skin guard,  760 A . . . skin guard,  761  . . . guard base,  761 A . . . guard base,  762  . . . guard contact portion,  762 A . . . openings,  762 B . . . distal end recess,  763  . . . rotating portion,  763 A . . . rotating spherical surface,  860  . . . skin guard,  860 A . . . skin guard,  861  . . . guard base,  861 A . . . guard base,  862  . . . guard contact portion,  862 A . . . distal end surface,  921  . . . outer blade,  930  . . . inner blade unit,  940  . . . inner blade,  941  . . . inner blade main body wall,  942  . . . blade piece,  942 A . . . distal end surface,  943  . . . inner blade hole,  944  . . . inner blade internal space,  960  . . . skin guard,  960 A . . . skin guard,  961  . . . guard base,  961 A . . . guard base,  962  . . . guard contact portion,  962 A . . . distal end surface,  121 A . . . outer blade,  130 A . . . inner blade unit,  140 A . . . inner blade,  141 A . . . inner blade main body wall,  142 A . . . blade piece,  142 X . . . distal end surface,  143 A . . . inner blade hole,  144 A . . . inner blade internal space,  960  . . . skin guard,  961  . . . guard base,  961 A . . . guard base,  962  . . . guard contact portion,  962 A . . . distal end surface,  160 B . . . skin guard,  161 B . . . first skin guard,  162 B . . . second skin guard,  160 C . . . skin guard,  161 C . . . guard base,  162 C . . . guard contact portion,  162 CX . . . distal end surface,  130 D . . . inner blade unit,  140 D . . . inner blade,  143 D . . . inner blade hole,  144 D . . . inner blade internal space,  150 D . . . inner blade joint component,  160 D . . . skin guard,  160 DA . . . skin guard,  161 D . . . guard base,  161 DA . . . guard base,  162 D . . . guard contact portion,  1000  . . . electric shaver,  1010  . . . outer blade,  1011  . . . outer blade hole,  1020  . . . inner blade,  1021  . . . inner blade hole,  1030  . . . skin,  1040  . . . facial hair.