Locking device

A spring force of a thrust spring can be determined independently of a spring force of a locking spring, reducing an operating load of an unlocking operation. A locking device includes a locking mechanism provided on one of two members to be engaged with each other, and a striker provided on the other of the two members. The locking mechanism includes a base plate, a hook, a pawl, a cam, a locking spring, a thrust spring and a canceling plate. The base plate has a recess that is capable of receiving the striker. The hook, when rotated relative to the base plate, is capable of forming a locked condition in which the striker is held between the hook and the recess of the base plate or an unlocked condition in which the hook is spaced away from the striker. The pawl is capable of rotating relative to the base plate and maintaining the hook in the locked condition. The cam is capable of further pressing the hook in the locked condition toward a locking direction. The locking spring is capable of biasing the hook and the pawl such that the hook and the pawl are stabilized in the locked condition or the unlocked condition. The thrust spring is capable of biasing the cam in a direction to press the hook. The canceling plate is rotatably supported via a shaft of the hook and is coaxially rotatable with the hook. The canceling plate has a movable range in which the canceling plate can rotate relative to the hook and has a contacting portion that is capable of contacting the striker within the movable range when the hook is in the locked condition.

TECHNICAL FIELD

The present invention relates to a locking device that is mainly used to lock a vehicle seat to a vehicle body side or to release the lock.

BACKGROUND ART

A known example of a locking device of this type is a technique disclosed in Patent Document 1. In this technique, a locking mechanism is provided on a seat side, and a striker is provided on a vehicle body side. The locking mechanism includes a base plate having a recess capable of receiving the striker, a hook, a pawl and a cam. The hook is rotatably attached to the base plate via a shaft, so that the locking mechanism is in a locked condition in which the striker is held between the hook and the recess of the base plate or in an unlocked condition in which the hook is spaced away from the striker. The pawl and the cam are rotatably attached to the base plate via a common shaft.

A locking spring is positioned between the hook and the pawl. The locking spring biases the hook and the pawl such that the hook and the pawl are stabilized at a rotational position corresponding to the locked condition or the unlocked condition. Also, a thrust spring is positioned between the cam and the base plate. The thrust spring biases the cam in a direction that the hook in the locked condition is further pressed toward a locking direction. As a result, a clearance between the striker and the locking mechanism in the locked condition is forcibly reduced.

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

In this way, when the hook and the pawl are retained in the locked condition, the locking spring biases the hook toward an unlocking direction. Conversely, at this time, the thrust spring biases the cam such that the hook is pressed toward the locking direction against a force of the locking spring. Therefore, a spring force of the thrust spring must be set so as to be normally greater than the locking spring. As a result, a large operating load will be required for unlocking the locking mechanism.

The present invention has been made for solving such problems. It is one object of the present invention to make it possible to freely determine a spring force of a thrust spring independently of a spring force of a locking spring, thereby reducing an operating load of an unlocking operation.

Means for Solving the Problem

The present invention has the following structure in order to achieve the above-mentioned objects.

A first invention is a locking device, which includes a locking mechanism provided on one of two members to be engaged with each other, and a striker provided on the other of the two members. The locking mechanism includes a base plate, a hook, a pawl, a cam, a locking spring, a thrust spring and a canceling plate.

The base plate has a recess that is capable of receiving the striker. The hook is rotatably attached to the base plate via a shaft. The hook, when rotated, is capable of forming a locked condition in which the striker is held between the hook and the recess of the base plate or an unlocked condition in which the hook is spaced away from the striker. The pawl is rotatably attached to the base plate via a shaft. The pawl is capable of rotating to a position in which the pawl can engage the hook and maintaining the hook in the locked condition. The cam is rotatably supported via the shaft of the pawl and is coaxially rotatable with the pawl. The cam is capable of further pressing the hook in the locked condition toward a locking direction. The locking spring is provided between the pawl and the canceling plate. The locking spring is capable of biasing the hook and the pawl such that the hook and the pawl are stabilized in the locked condition or the unlocked condition. The thrust spring is provided between the cam and the base plate and is capable of biasing the cam in a direction to press the hook. The canceling plate is rotatably supported via the shaft of the hook and is coaxially rotatable with the hook. The canceling plate has a movable range in which the canceling plate can rotate relative to the hook and has a contacting portion that contacts the striker within the movable range when the hook is in the locked condition.

According to this structure, when the hook of the locking mechanism is in the locked condition, the contacting portion of the canceling plate contacts the striker, so as to prevent the biasing force of the locking spring from acting on the hook. Therefore, a spring force of the thrust spring for further pressing the hook in the locked condition toward the locking direction can be freely determined independently of a spring force of the locking spring. As a result, the biasing force of the thrust spring can be reduced without changing the spring force of the locking spring, so that an operation load for unlocking the locking mechanism can be reduced.

A second invention corresponds to the locking device of the first invention, in which the cam comprises a contact portion that is capable of contacting the hook. The contact portion is formed with a pressure angle that functions to further rotate the hook in the locked condition toward the locking direction and to maintain the hook while receiving a rotational load that is applied to the hook toward an unlocking direction.

The pressure angle formed in the contact portion of cam may further increase a function that further press the hook in the locked condition toward the locking direction based on the spring force of the thrust spring.

A third invention is a locking device, which includes a locking mechanism provided on one of two members to be engaged with each other, and a striker provided on the other of the two members. The locking mechanism includes a base plate, a hook, a pawl, a cam, a locking spring, a thrust spring and a transmission member.

The base plate has a recess that is capable of receiving the striker. The hook is rotatably attached to the base plate via a shaft. The hook, when rotated, is capable of forming a locked condition in which the striker is held between the hook and the recess of the base plate or an unlocked condition in which the hook is spaced away from the striker. The pawl is rotatably attached to the base plate via a shaft. The pawl is capable of rotating to a position in which the pawl can engage the hook and maintaining the hook in the locked condition. The cam is formed with a pressure angle that functions to further rotate the hook in the locked condition toward the locking direction and to maintain the hook while receiving a rotational load that is applied to the hook toward an unlocking direction. The locking spring is capable of biasing the pawl toward an engaging direction or a non-engaging direction with respect to the hook. The thrust spring is provided between the cam and the base plate and is capable of biasing the cam in a direction to press the hook. The transmission member is capable of transmitting a spring force of the locking spring to the hook or the striker. The transmission member contacts the striker when the hook is in the locked condition, thereby transmitting the spring force of the locking spring to the striker. Also, the transmission member is released from the striker and contacts the hook when the hook is in the unlocked condition, thereby transmitting the spring force of the locking spring to the hook.

According to this structure, depending on whether the hook of the locking mechanism is in the locked condition or the unlocked condition, a transmission target of the biasing force of the locking spring via the transmission member can be reliably switched between the striker and the hook.

A fourth invention corresponds to the locking device of the first, second or third invention, in which the pawl has an engagement end surface that can engage an engagement surface of the hook in the locked condition. The pawl is arranged such that when the hook in the locked condition is further pressed toward the locking direction by means of the cam, the engagement surface of the hook and the engagement end surface of the pawl are spaced away from each other.

According to this structure, in a condition that the hook in the locked condition is further pressed toward the locking direction, the engagement surface of the hook and the engagement end surface of the pawl do not contact each other. This may lead to reduction of noise.

A fifth invention corresponds to the locking device of the first, second, third or fourth invention, in which the pawl has an entrainment portion. The entrainment portion is constructed to contact the cam when the pawl is rotated in a direction to be displaced from a position in which the pawl is capable of engaging the hook, thereby rotating the cam in the direction.

According to this structure, in a lock releasing operation of the locking mechanism, upon rotation of the pawl, the cam can be simultaneously rotated. Therefore, the lock releasing operation can be unified.

A sixth invention corresponds to the locking device of the first, second, third, fourth or fifth invention, in which the two members to be engaged with each other are respectively a floor of a vehicle and a seat cushion of a retractable seat. The locking mechanism and the striker are respectively attached to the seat cushion and the floor.

DESCRIPTION OF REFERENCE SYMBOLS

BEST MODES FOR CARRYING OUT THE INVENTION

In the following, a preferred embodiment for carrying out the present invention will be described with reference to the drawings.

FIG. 1is a side view of a retractable seat for a vehicle. In order to retract a seat of this type, a reclining device (not shown) is first operated to fold a seat back12onto a seat cushion10as shown inFIG. 1. At the same time, a lock releasing operation is performed in order to unlock a locking device that engages a rear side lower portion of the seat cushion10with a floor14side. Thereafter, the seat cushion10is rotated using a front side end portion thereof as a fulcrum, so that the entire seat is raised against a back surface of a front seat (not shown).

As a structure for this purpose, the front side end portion of a cushion frame11of the seat cushion10is connected to a hinge bracket16fixed to the floor14via a rotation shaft18. Further, the locking device engaging the rear side lower portion of the cushion frame11with the floor14side is roughly divided into a locking mechanism20that is positioned at the rear side lower portion (one of two members) of the cushion frame11, and a striker70that is fixed to the floor14(the other of the two members). The seat shown inFIG. 1is, for example, a rear seat for three passengers. A connection structure that is composed of the hinge bracket16and the rotation shaft18and the locking device that is composed of the locking mechanism20and the striker70are respectively disposed on, for example, both sides of the seat.

FIG. 2is a structural view of the locking device in an unlocked condition.FIG. 3is a structural view of the locking device in a half-locked condition.FIG. 4is a structural view of the locking device in a locked condition.FIG. 5is a structural view of the locking device in a thrust condition. As shown in these drawings, the locking mechanism20includes a base plate22, a hook30, a canceling plate40, a pawl46(including a release lever52) and a thrusting cam60. The base plate22is composed of a pair of superimposed plate elements, so that the remaining components of the locking mechanism20are positioned between the plate elements. However, inFIGS. 2-5, the nearer plate element is omitted. The base plate22is connected to the cushion frame11(FIG. 1).

A lower portion of the base plate22is provided with a recess23that is downwardly opened. The recess23can receive the striker70from an open side thereof. An opening width of the recess is gradually increased downwardly, so as to facilitate receiving of the striker. The base plate22has a stopper24and a spring engagement portion25that are formed therein by partly folding a right side periphery of thereof.

The hook30is rotatably attached to a support shaft36that is fixed to the base plate22. The hook30has a hook recess31that is opened leftwardly in the drawings. When the hook recess31engages the striker70that is received in the recess23of the base plate22, the striker70is held between the hook recess31and the recess23, so that the locked condition of the locking mechanism20is obtainedFIG. 4. The hook30has an engagement surface32that is formed in a circumferential surface thereof, and a projection33that is integrally projected therefrom, which protrusion is positioned between the engagement surface32and the support shaft36. Also, the hook30has a cylindrical engagement protrusion34that is integrally formed therein, which protrusion is opposed to the projection33across the support shaft36. Further, the engagement protrusion34can be replaced with a pin or other such member that is fixedly attached to the hook30.

The canceling plate40is rotatably attached to the support shaft36of the hook30. The canceling plate40has a contacting portion41that extends along one of opposite peripheries of the hook recess31of the hook30, and a spring engagement portion43that is formed therein by folding an opposite end portion of the contacting portion41. Also, the canceling plate40has a circular engagement hole42in which the engagement protrusion34of the hook30is loosely received. Thus, a clearance is formed between an outer circumferential surface of the engagement protrusion34and an inner circumferential surface of the engagement hole42, so as to define a movable range in which the canceling plate40can rotate relative to the hook30. Further, after the engagement protrusion34and the engagement hole42eccentrically contact each other, the hook30and the canceling plate40may integrally rotate.

The pawl46, the release lever52and the cam60are respectively attached to a support shaft50that is rotatably attached to the base plate22. The pawl46and the release lever52is attached to the support shaft50so as to rotate integrally therewith, whereas the cam60is rotatably attached to the support shaft50. Therefore, the pawl46and the release lever52may integrally rotate via the support shaft50, and the cam60may rotate relative to the pawl46and the release lever52. Further, the release lever52is connected to an operation cable or other such element (not shown) for performing the lock releasing operation, so that the pawl46can be rotated when the lock releasing operation is performed.

The pawl46has an engagement end surface47that can contact and push the engagement surface32of the hook30, and a protrusion48that is capable of contacting a portion of the cam60. Conversely, the release lever52has a spring engagement portion53that is formed by partly folding a side periphery of thereof. A locking spring56, composed of a tension coil spring, is positioned between the spring engagement portion53and the spring engagement portion43of the canceling plate40. By a spring force of the locking spring56, the hook30is being biased counterclockwise in the drawings via the canceling plate40and at the same time, the pawl46is biased clockwise via the release lever52. Further, the protrusion48of the pawl46corresponds to “an entrainment portion” of the present invention.

The thrusting cam60has a contact surface61that is capable of contacting the projection33of the hook30, which surface is formed in a distal end portion thereof. The contact surface61corresponds to “a contact portion” of the present invention. Further, the cam60has an arm portion62that is capable of contacting the protrusion48of the pawl46, and a spring engagement portion63that is formed by partly folding an end portion of the arm portion62. A thrust spring66composed of a tension coil spring is positioned between the spring engagement portion63and the spring engagement portion25of the base plate22. By a spring force of the thrust spring66, the cam60is being biased clockwise. Further, the cam60has a deformation promoting portion64that is formed between the contact surface61and a portion supported by the support shaft50, which portion is swollen to a bead-like shape. The deformation promoting portion64can deform with a smaller force than the other portions when the cam60is applied with a load from the hook30side.

Next, a function of the locking device will be described.

First, the locking mechanism20is now in the unlocked condition shown inFIG. 2. In this condition, the hook30is being biased counterclockwise via the canceling plate40due to the spring force of the locking spring56. That is, the engagement protrusion34of the hook30and the engagement hole42of the canceling plate40eccentrically contact each other. In addition, the circumferential surface of the hook30contacts the stopper24of the base plate22, so that the hook30is stabilized. Further, the pawl46(including the release lever52), biased clockwise due to the spring force of the locking spring56, contacts the circumferential surface of the hook30, so as to be stabilized. Also, the cam60biased clockwise due to the spring force of the thrust spring66contacts the projection33of the hook30, so as to be stabilized.

In the unlocked condition, when the seat cushion10is moved in order to be set in the floor14side, the striker70positioned on the floor14side enters the recess23formed in the base plate22of the locking mechanism20(FIG. 3). Upon entering of the striker70, the hook recess31of the hook30engages the striker70and at the same time, the contacting portion41of the canceling plate40contacts the striker70. As a result, the hook30and the canceling plate40rotate counterclockwise against the spring force of the locking spring56, so that the locked condition shown inFIG. 4is obtained. In this locked condition, the pawl46is rotated clockwise due to the spring force of the locking spring56, so that the engagement end surface47thereof contacts the engagement surface32of the hook30. Thus, the hook30is maintained in the locked condition (FIG. 4).

When the locking device is changed to the locked condition shown inFIG. 4, the cam60is rotated clockwise due to the spring force of the thrust spring66. As a result, the contact surface61of the cam60pushes the projection33of the hook30, thereby further rotating the hook30clockwise. That is, a pressure angle is defined in the contact surface61of the cam60, so as to apply a clockwise biasing force to the hook30. As a result, the striker70can be thrust into the recess23of the base plate22(FIG. 5). Therefore, the striker70is firmly held between the recess23of the base plate22and the hook recess31of the hook30, so that a clearance between the locking mechanism20and the striker70can be eliminated.

FIG. 6is an explanatory view of the pressure angle defined in the contact surface61of the cam60. In this drawing, a rotation center of the cam60, i.e., an axis of the support shaft50, will be referred to as A. Also, a contact point of the contact surface61of the cam60and the projection33of the hook30is referred to as P. In addition, a circular arc centered on the axis A and passing through the contact point P will be referred to as C1. Also, a circular arc extending along the contact surface61of the cam60and passing through the contact point P will be referred to as C2. Further, a tangential line with respect to the circular arc C1at the contact point P will be referred to as L1. Also, a tangential line with respect to the circular arc C2at the contact point P will be referred to as L2. The pressure angle in the contact surface61corresponds to an angle θ formed by the tangential lines L1and L2. When the cam60rotates clockwise inFIG. 6, the hook30can be rotated clockwise due to the pressure angle θ.

Further, the pressure angle θ in the contact surface61is restricted as follows. That is, if the pressure angle θ is excessively reduced, a clockwise rotational angle of the hook30is reduced when the cam60rotates clockwise. As a result, a rotational angle of the cam60must be increased, so that freedom of design is restricted. To the contrary, if the pressure angle θ is excessively increased, when the hook30is applied with a counterclockwise load, the cam60is pushed counterclockwise, so that the contact surface61may be disengaged from the projection33of the hook30. Therefore, the pressure angle θ may preferably be 5-12 degrees, more preferably, 7-10 degrees.

When the hook30is in a locked position shown inFIGS. 4 and 5, a biasing force of the locking spring56functions to rotate the canceling plate40counterclockwise. At this time, the contacting portion41of the canceling plate40contacts the striker70, so that a rotational position of the canceling plate40can be determined. In this condition, the engagement protrusion34of the hook30and the engagement hole42of the canceling plate40concentrically positioned without contacting each other. That is, the canceling plate40is in the movable range in which the canceling plate40can rotate relative to the hook30. Therefore, the biasing force of the locking spring56acting on the canceling plate40does not function to bias the hook30.

Thus, the canceling plate40can be taken as “a transmission member” that may transmit the biasing force of the locking spring56to the hook30or the striker70based on whether the hook30is in the unlocked condition or the locked condition.

As described above, the thrust spring66may function to bias the cam60, so as to press the hook30toward a locking direction against the biasing force of the locking spring56. However, when the hook30is in the locked position, the biasing force of the locking spring56does not function to bias the hook30. Therefore, the spring force of the thrust spring66can be freely determined independently of the spring force of the locking spring56.

In the thrust condition shown inFIG. 5, although the engagement surface32of the hook30is spaced away from the engagement end surface47of the pawl46, they are positioned so as to contact each other. Therefore, when a large load is generated in a direction that the striker70is disengaged from the recess23of the base plate22, the deformation promoting portion64of the cam60is deformed, so that the engagement surface32of the hook30contacts the engagement end surface47of the pawl46. As a result, a clearance elimination function for eliminating the clearance between the locking mechanism20and the striker70is canceled. However, the locking mechanism20is maintained in the locked condition. In this way, when a load having a predetermined value or more is exerted between the locking mechanism20and the striker70in the locked condition, the deformation promoting portion64of the cam60can be deformed before any other portions contained in a transmission route thereof are deformed. As a result, fatal portions of the locking mechanism20can be prevented from deforming, thereby maintaining at least the original locking function.

When the locking mechanism20is unlocked, the pawl46is rotated counter clockwise against the spring force of the locking spring56via the release lever52. As a result, the engagement end surface47of the pawl46is displaced from a position opposed to the engagement surface32of the hook30. Thereafter, the protrusion48of the pawl46contacts the arm portion62of the cam60. Also, the cam60is rotated counterclockwise with the pawl46against the spring force of the thrust spring66, so that the contact surface61thereof is disengaged from the projection33of the hook30. As a result, the hook30is returned to the condition shown inFIG. 2with the canceling plate40, so that the locking mechanism20is changed to the unlocked condition.

FIG. 7is a structural view of the locking device20according to a different embodiment, which view corresponds toFIG. 2. In the locking device20shown in this drawing, the base plate22is not provided with the stopper24. Instead, a stopper hole28is formed in one of the plate elements of the base plate22. The spring engagement portion43of the canceling plate40is positioned in the stopper hole28. As shown in the drawing, when the locking mechanism20is in the unlocked condition, the spring engagement portion43of the canceling plate40that is biased counterclockwise by the spring force of the locking spring56contacts a periphery of the stopper hole28, so that the canceling plate40is stabilized. Thus, in the unlocked condition, the spring force of the locking spring56is received in the canceling plate40side. At this time, the engagement protrusion34of the hook30and the engagement hole42of the canceling plate40eccentrically contact each other at a portion opposite to a portion shown inFIG. 2. Further, in the half-locked condition, the locked condition and the thrust condition, the locking mechanism20shown inFIG. 7may function in substantially the same manner asFIGS. 3-5.

The preferred embodiment for carrying out the present invention have been described with reference to the drawings. However, the embodiment can be easily changed or modified without departing from the gist of the present invention.

For example, in the present embodiment, the seat cushion10of the retractable seat and the floor14are exemplified as the two members that respectively have the locking mechanism20and the striker70. However, they can be replaced with any two members that require locking and unlocking by the locking device. Further, in the locking mechanism20, as a mechanism for defining the movable range in which the canceling plate40can rotate relative to the hook30, following mechanisms (a) and (b) can be used in place of a combination of the engagement protrusion34and the engagement hole42.

(a) The engagement hole42of the canceling plate40can be changed to a slot having an opening portion opened to a direction that is not expected to contact (interfere with) the engagement protrusion34of the hook30. In this case, three types of slots are available with regard to the direction of the opening portion.

Type 1: In the locking mechanism20shown inFIGS. 1-7, the engagement hole42can be changed to a slot having an opening portion that is opened downwardly to the right in, for example,FIGS. 2 and 7.

Type 2: In the locking mechanism20shown inFIGS. 1-6, the engagement hole42can be changed to a slot having an opening portion that is opened upwardly to the right in, for example,FIG. 2.

Type 3: In the locking mechanism20shown inFIG. 7, the engagement hole42can be changed to a slot having an opening portion that is opened downwardly to the left inFIG. 7.

(b) The engagement protrusion34of the hook30and the engagement hole42of the canceling plate40can be replaced with each other. For example, an outer periphery of the hook30can be formed with a removed or recessed portion. Conversely, the canceling plate40is provided with a projection that is loosely engaged with the recessed portion.