A half-fitting prevention connector (1) includes a first connector (2) and a second connector (3). The first connector (2) has an engagement groove (7) and retaining projections (8) provided at a front end portion thereof. The second connector (3) includes a housing body (4) and a slider (5) slidably mounted within the housing body (4). The housing body (4) includes an elastic lock arm (10) having at its front end a lock portion (9) for engagement in the engagement groove (7), and the slider (5) is resiliently urged in an axial direction, and has an elastic cantilever arm (12), and abutment portions (11) for abutting engagement respectively with the retaining projections (8) are formed at a front end of the cantilever arm (12). An abutment surface of each retaining projection (8) are both formed into substantially-arcuate surfaces, substantially disposed on an imaginary circle (A) having its center disposed on an axis (C) of flexing of the cantilever arm (12).

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a half-fitting prevention connector, used
 to electrically connect wire harnesses in an automobile and others, in
 which a half-fitted condition is prevented by a resilient force of a
 resilient member, and also damage to the connector is prevented.
 The present application is based on Japanese Patent Application No. Hei.
 10-254119, which is incorporated herein by reference.
 2. Description of the Related Art
 Various half-fitting prevention connectors have heretofore been known. For
 example, a half-fitting prevention connector, disclosed in Unexamined
 Japanese Patent Publication No. Hei. 9-134757, will be described.
 As shown in FIG. 8, the related half-fitting prevention connector 61
 comprises a first connector 62, in which connector terminals 78, connected
 respectively to wires of a wire harness, are mounted, and a second
 connector 63 in which connector terminals 79 for contact respectively with
 the connector terminals 78 are mounted. The second connector 63 comprises
 a housing body 64, and a slider 65 which is attached to the outer
 periphery of the housing body 64 for sliding movement in an axial
 direction, and is resiliently urged forward.
 An engagement groove 67 and a retaining projection 68 are provided at a
 front end portion of a housing of the first connector 62, and an elastic
 lock arm 70, having a lock portion 69 for engagement in the engagement
 groove 67, is provided at a front end portion of the housing of the second
 connector 63.
 The slider 65 is resiliently urged forward in the axial direction so as to
 control the flexing (elastic deformation) of the lock arm 70 and also to
 prevent a half-fitted condition, and an abutment portion 71 for abutting
 engagement with the retaining projection 68 is provided at the front end
 of the slider 65. This abutment portion 71 is provided at a cantilever arm
 72 connected to a rear end portion of the slider 65, and this cantilever
 arm 72 can be elastically deformed outwardly, and has a rectangular slide
 hole 73 formed through a central portion thereof.
 A cantilever arm-pressing projection 74 is formed at that portion of the
 housing body 64 corresponding to the slide hole 73. The male connector
 terminals 78 project into an internal space 75 of the first connector, and
 the female connector terminals 79 are received respectively in terminal
 receiving chambers 76 in the housing body 64.
 In the half-fitting connector 61 of the above construction, as the first
 and second connectors 62 and 63 are fitted together as shown in FIG. 9,
 the abutment portion 71, formed at the distal end of the cantilever arm 72
 formed on the slider 65, is first brought into abutting engagement with
 the retaining projection 68 formed on the housing 66 of the first
 connector 62.
 Then, when the housing body 64 of the second connector 63 is further pushed
 in the fitting direction, only the housing body 64 advances in the fitting
 direction, with the slider 65 kept stopped. As a result, the front portion
 of the lock arm 70 is exposed from the slider 65, and therefore can be
 flexed upwardly as shown in FIG. 10. Then, when the housing body 64 is
 further pushed, the lock portion 69 slides onto the front end portion of
 the mating housing 66.
 Then, immediately before the lock portion 69 is brought into engagement in
 the engagement groove 67, the cantilever arm-pressing projection 74
 presses the abutment portion 71 to cancel the retaining engagement of the
 abutment portion 71 with the retaining projection 68 as shown in FIG. 11,
 and therefore the lock portion 69 is engaged in the engagement groove 67,
 and at the same time the slider 65 advances under the influence of the
 resilient force to cover the lock portion 69, thereby preventing the
 disengagement of the lock portion.
 If the fitting force is removed before the abutment portion 71 is
 disengaged from the engagement projection 68, the housing body 64 is
 pushed back in an anti-fitting direction under the influence of the
 resilient force acting on the slider 65. Therefore, such a half-fitted
 condition of the two connectors can be easily detected.
 For canceling the fitted condition of the first and second connectors 62
 and 63, the slider 65 is returned rearward, and as a result, the housing
 body 64 is also returned since a slide range-limiting mechanism (not
 shown) is provided between the slider 65 and the housing body 64. At this
 time, the lock portion 69 is not covered with the slider 65, and the lock
 portion 69 has a rear slanting surface, and therefore the lock portion 69
 is disengaged from the engagement groove 67 while flexing the lock arm 70
 outwardly. When the slider 65 is released after the first and second
 connectors 62 and 63 are disconnected from each other, the slider 65 is
 moved in the disconnecting direction under the influence of the resilient
 force.
 However, in the above half-fitting prevention connector 61, when the
 abutment portion 71 of the slider 65 is to be disengaged from the
 retaining projection 68 during the fitting operation as shown in FIG. 11,
 the cantilever arm 72 is flexed about a flexing axis C as shown in FIG.
 12. In this case, if an abutment surface 71a of the abutment portion 71
 and a retaining surface (abutment surface) 68a of the retaining projection
 68 are both vertical, one or both of the two is subjected to chipping or
 deformation at a lap portion L, thus inviting a problem that the
 reliability and durability are much lowered.
 And besides, the cantilever arm 72 is formed on the slider 65 slidably
 attached to the outer periphery of the housing body 64, and therefore
 there is a possibility that the slider is deformed or damaged upon
 accidental impingement of an external object, which leads to a
 malfunction, and this results in a problem that the reliability and
 durability are further lowered.
 SUMMARY OF THE INVENTION
 With the above problems in view, it is an object of the present invention
 to provide a half-fitting prevention connector in which part of a housing
 is prevented from deformation and damage during a fitting operation, and a
 malfunction due to an accidentally-impinging object is prevented, thereby
 achieving excellent reliability and durability.
 To achieve the above object, according to the first aspect of the present
 invention, there is provided a half-fitting prevention connector which
 comprises a first connector including a first housing having an engagement
 groove and a retaining projection which are provided at a front end
 portion of the first housing, a second connector fittable to the first
 connector, the second connector including a second housing having an
 elastic lock arm, a front end of the elastic lock arm having a lock
 portion engaged with the engagement groove of the first housing when the
 first connector is fitted to the second connector, a slider attachable to
 the second housing, the slider being resiliently urged in an axial
 direction thereof when the slider is attached to the second housing, the
 slider including an elastic cantilever arm, and an abutment portion formed
 at a front end of the cantilever arm of the slider, the abutment portion
 having an abutment surface which abuts against an abutment surface of the
 retaining projection of the first housing when the first connector is
 fitted to the second connector. In the half-fitting prevention connector,
 the abutment surface of the abutment portion and the abutment surface of
 the retaining projection are substantially slanting surfaces which are
 substantially formed along an imaginary circle having its center at the
 axis of flexing of the cantilever arm. In other words, the abutment
 surface of the abutment portion and the abutment surface of the retaining
 projection are formed substantially in conformance with a locus of the
 flexing of the front end of the cantilever arm.
 Therefore, when the abutment portion of the slider, abutted against the
 retaining projection, is to be disengaged therefrom during the fitting
 operation, there is no interfering lap portion between these abutment
 surfaces, and the two surfaces can smoothly slide relative to each other.
 Therefore, deformation and damage will not develop, and the reliability
 and durability can be enhanced.
 In the above half-fitting prevention connector, preferably, the slider is
 attachable to the second housing so that the slider is received within the
 second housing.
 Therefore, deformation and damage by an accidentally-impinging object can
 be positively prevented. Accordingly, a malfunction due to deformation and
 damage is prevented, and the reliability and durability can be further
 enhanced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 One preferred embodiment of a half-fitting prevention connector of the
 present invention will now be described in detail with reference to FIGS.
 1 to 7.
 As shown in FIG. 1, the half-fitting prevention connector 1 comprises a
 first connector 2, having an engagement groove 7 and retaining projections
 8 provided at a front end portion of a housing 6, and a second connector 3
 including a housing body 4 and a slider 5 slidable within the housing body
 4. The housing body 4 includes an elastic lock arm 10 having at its front
 end a lock portion 9 for engagement in the engagement groove 7. The slider
 5 is resiliently urged in the axial direction by compression springs 30 so
 as to control the flexing (elastic deformation) of the lock arm 10 and
 also to prevent a half-fitted condition. The slider 5 has an elastic
 cantilever arm 12 at its central portion, and abutment portions 11 for
 abutting engagement respectively with the retaining projections 8 are
 formed on and project downwardly from a front end of the cantilever arm
 12.
 In the half-fitting prevention connector of this embodiment, abutment
 surfaces 11a of the abutment portions 11 and retaining surfaces (abutment
 surfaces) 8a of the retaining projections 8 are formed either into arcuate
 (arc-shaped) surfaces, disposed on an imaginary circle A having its center
 disposed on an axis C of flexing of the cantilever arm 12, or into
 substantially-arcuate slanting surfaces close to the arcuate surfaces of
 the imaginary circle A.
 The slider 5 is received within the housing body 4, and the cantilever arm
 12 is provided at the central portion of the slider 5 in spaced relation
 of an upper surface of the slider 5.
 More specifically, one engagement groove 7 is formed in the upper surface
 of the housing 6 of the first connector 2, and the pair of retaining
 projections 8 and 8 are formed on the front portion of this upper surface.
 A plurality of female connector terminals 18 are received respectively in
 terminal receiving chambers 15.
 One elastic lock arm 10, having one lock portion 9 for engagement in the
 engagement groove 7, is formed at a central portion of the front end
 portion of the housing body 4. A pair of abutment portion-pressing
 projections 14 and 14 for respectively lifting the abutment portions 11
 while flexing the cantilever arm 12 are formed at a proximal end portion
 of the lock arm 10.
 A plurality of terminal receiving chambers 16 are formed below the lock arm
 10, and a plurality of male connector terminals 19 are received
 respectively in these terminal receiving chambers. A pair of spring
 receiving chambers 31 and 31 are provided adjacent to the outer sides of
 the abutment portion-pressing projections 14, respectively, and the
 compression springs 30 are received respectively in these spring receiving
 chambers. A pair of slide guide grooves 13 and 13 are provided above the
 spring receiving chambers 31, respectively, and extend in the longitudinal
 direction. A stop plate 21 for limiting the movement of the front end of
 the slider 5 is formed at the front end of the upper side of the housing
 body. A disengagement prevention projection 9a for preventing accidental
 cancellation of a locked condition is formed on the upper surface of the
 lock portion 9 formed at the front end of the lock arm 10.
 An operating portion 17 is formed on the rear end of the slider 5, and when
 disconnecting the two connectors from each other, the slider 5 is pulled
 in an anti-fitting direction through this operating portion 17. Guide
 portions 33 are formed respectively at opposite side portions of the upper
 portion of the slider, and extend from its rear end to its front end, and
 these guide portions 33 are guided respectively by the slider guide
 grooves 13 so that the slider can slide forward and rearward. Stop
 projections 22 are formed on the upper surface of the slider 5, and can
 abut against the stop plate 21 of the housing body 4, thereby limiting the
 movement of the slider 5.
 Spring retaining plates 32 are provided respectively at the front ends of
 the guide portions 33, and the front ends of the compression springs 30
 are abutted respectively against these plates 32. A disengagement
 prevention plate 22 is provided at the front end of the slider 5, and
 interconnects the pair of spring retaining plates 32, and this
 disengagement prevention plate 22 covers the lock portion 9 from the upper
 side so that the lock portion 9 will not be disengaged from the engagement
 groove 7.
 In the half-fitting prevention connector 1 of the above construction, as
 shown in FIGS. 1 and 2, the plurality of female terminals 18 each
 connected to a wire are inserted respectively into the terminal receiving
 chambers 15 in the first connector 2, and the plurality of male terminals
 19 each connected to a wire are inserted respectively into the terminal
 receiving chambers 16 in the second connector 3. Then, the compression
 springs 30 are inserted respectively into the spring receiving chambers 31
 in the second connector 3, and thereafter the slider 5 is inserted into
 the housing body 4 while being guided by the slider guide grooves 13. At
 this time, the slider is inserted while rear slanting surfaces of the stop
 projections 20 flex the stop plate 21, and the front end surfaces of the
 stop projections 20 abut against the rear edge of the stop plate 21,
 thereby determining the position of the front end of the slider 5.
 Next, the operation for fitting the first and second connectors 2 and 3
 together will be described. As shown in FIG. 3, when the first and second
 connectors 2 and 3 begin to be fitted together, the abutment surfaces 11a
 of the abutment portions 11, formed on the slider 5, abut respectively
 against the retaining surfaces 8a of the retaining projections 8 formed on
 the housing 6 of the first connector 2. When the housing 6 of the first
 connector 2 is further pushed in the fitting direction, the slider 5 is
 moved toward the rear end of the housing body 4 against the bias of the
 compression springs 30, as shown in FIG. 4.
 As a result, a front slanting surface of an engagement projection 7a abuts
 against a front slanting surface of the lock portion 9 to press the lock
 portion 9 upward, so that the lock arm 10 is flexed upwardly, as shown in
 FIGS. 4 and 5. Then, the lock portion 9 slides over the engagement
 projection 7a of the mating housing 6, and is engaged in the engagement
 groove 7.
 At this time, front slanting surfaces of the abutment portion-pressing
 projections 14 abut respectively against rear end surfaces of the abutment
 portions 11, so that the cantilever arm 12 of the slider 5 is pressed and
 flexed upwardly, as shown in FIG. 5. As a result, the abutment surface 11a
 of each abutment portion 11, abutted against the associated retaining
 projection 8, is urged upward to slide on the retaining surface 8a. As a
 result, the slider 5 is moved to the foremost position in the housing body
 4 by the resilient force of the compression springs 30 as shown in FIG. 6.
 The disengagement prevention plate 22 holds the disengagement prevention
 projection 9a, formed at the front end of the lock arm 10, from the upper
 side, thereby preventing the engaged condition from being canceled by
 vibrations and so on. Thus, the operation for fitting the first and second
 connectors 2 and 3 is completed.
 If the pushing force is removed before the abutting engagement of the
 abutment portions 11 with the retaining projections 8 is canceled, the
 housing body 4 is pushed back away from the housing 6 by the resilient
 force of the compression springs 30 into a position where the female and
 male terminals are not completely electrically connected together.
 Therefore, a half-fitted condition of the first and second connectors 2
 and 3 can be positively detected.
 For canceling the fitted condition of the first and second connectors 2 and
 3, the finger is engaged with the operating portion 17, and is pulled in
 the anti-fitting direction against the bias of the compression springs 30.
 As a result, the disengagement prevention plate 22 slides rearwardly over
 the disengagement prevention projection 9a, so that the lock arm 10 can be
 flexed upwardly. In this condition, when the housing 6 of the first
 connector 6 is pulled, the engagement projection 7a on the first connector
 2 can slide over the lock portion 9 because of the formation of the rear
 slanting surface of the lock portion 9, and therefore the first connector
 2 is withdrawn from the second connector 3.
 In the above half-fitting prevention connector 1, as shown in FIG. 7, the
 abutment portion 11 and the retaining surface 8a of each retaining
 projection 8 are both formed into substantially arcuate (arc-shaped)
 surfaces, substantially disposed on an imaginary circle A having its
 center disposed on the axis C of flexing of the cantilever arm 12.
 Therefore, when the abutment portion 11 of the slider 5, abutted against
 the retaining projection 8, is to be disengaged therefrom during the
 fitting operation, abutment surface 11a and the retaining surface 8a, and
 the two surfaces can smoothly slide relative to each other. Therefore,
 deformation and damage will not develop, and the reliability and
 durability can be enhanced.
 The slider 5 is received within the housing body 4, and the abutment
 portions 11 of the cantilever arm 12 is disposed at a level below the
 upper surface, and therefore deformation and damage by an
 accidentally-impinging object can be prevented. Therefore, a malfunction
 due to deformation and damage is not encountered, and the reliability and
 durability can be further enhanced.
 The half-fitting prevention connector of the present invention is not
 limited to the above embodiment, and suitable modifications can be made.
 For example, in the above embodiment, although one lock arm 10, having one
 lock portion 9, is provided at the central portion, a pair of lock arms
 can be provided at the opposite side portions, respectively, in which case
 the arrangement of the engagement groove 7 and the engagement projection
 7a of the mating connector 2 is suitably changed. Although the female
 connector terminals 18 are received in the housing 6 while the male
 connector terminals 19 are received in the housing body 4, this
 arrangement may be reversed, in which case the terminal receiving chambers
 15 and 16 are changed in configuration.
 As described above, in the half-fitting prevention connector of the present
 invention, the abutment surface of each abutment portion and the abutment
 surface of each retaining projection are both formed into
 substantially-arcuate surfaces, substantially disposed on an imaginary
 circle having its center disposed on the axis of flexing of the cantilever
 arm. Therefore, when the abutment portion of the slider, abutted against
 the retaining projection, is to be disengaged therefrom during the fitting
 operation, there is no interfering lap portion between these abutment
 surfaces, and the two surfaces can smoothly slide relative to each other.
 Therefore, deformation and damage will not develop, and the reliability
 and durability can be enhanced.
 And besides, the slider is received within the housing body, and therefore
 deformation and damage by an accidentally-impinging object can be
 positively prevented, and therefore a malfunction due to deformation and
 damage is prevented, and the reliability and durability can be further
 enhanced.