Portable transmitter contained in a hard-to-open case

An ID code is wirelessly sent to a device, such as a keyless-entry system or a keyless-starter system mounted on an automobile, from a portable transmitter. Electronic components including an electronic circuit board, a transponder and a battery are all contained in a resin case. The resin case is composed of a front case and a rear case, both firmly connected to each other. The case cannot be opened to take away the transponder contained therein without breaking the case. If the case is forcibly opened, a trace showing such a fact is unavoidably left on the case. The battery contained in the case, however, can be replaced or unloaded without breaking the case through an opening formed exclusively for the battery.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims benefit of priority of Japanese Patent Application No. 2003-106739 filed on Apr. 10, 2003, the content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a portable transmitter, which is advantageously used as a transmitter in a keyless-entry system for an automobile and in a keyless-starter system.

2. Description of Related Art

In conventional transmitters of this kind, a transponder for wirelessly transmitting an identification code (ID code) to a device to be operated is contained in a case. In a keyless-starter system for an automobile, for example, the engine is permitted to start when an IC code sent form the transmitter coincides with an ID code pre-installed in the automobile.

An example of the transmitter of this kind is disclosed in JP-A-2001-140513. A case containing components of the transmitter including a transponder and a battery is composed of a front case and a rear case, both being detachably connected. To replace a worn battery with a new one, it is necessary to be able to easily open the case. The case structure having the front case and the rear case detachably connected to each other, however, involves the following problem. The case may be opened by an unauthorized person such as a thief, and the transponder may be stolen without leaving a trace that the case was opened by someone. The thief is able to start the engine using the transponder to steal the automobile. Since no trace showing such an unauthorized act is left, it is highly possible that the owner does not notice for a certain period of time that the transponder is taken out from the transmitter case. Therefore, the possibility that the automobile is stolen will increase. The same problem is involved in the keyless-entry system.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an improved portable transmitter, in which a transponder contained therein is difficult to be taken away without leaving a trace on the transmitter case.

The portable transmitter includes an electronic circuit board, a battery for supplying power to the electronic circuit board, and a transponder, all these components being contained in a resin case. An ID code (an identification code) that allows a device to be operated upon receipt of the ID code is wirelessly transmitted from the portable transmitter to the device such as a keyless-entry system or a keyless-starter system for an automobile. When the battery voltage is normal, the ID code is transmitted from the electronic circuit board, and when the battery voltage is abnormally low, the ID code is transmitted from the transponder.

The resin case of the portable transmitter is composed of a front case and a rear case, both being firmly connected not to be easily separated. The front case includes a front hook having a projection and a depression, and similarly the rear case includes a rear hook having a projection and a depression. The projection of the front hook engages with the depression of the rear hook, while the projection of the rear hook engages with the depression of the front hook. Alternatively, the projection may be formed in either the front hook or the rear hook, and the projection may be engaged with the depression formed in the other hook.

Since the front case and the rear case are firmly connected not to be easily separated, if the case is forcibly opened, either the front hook or the rear hook is broken. Therefore, a trace showing that the case was forcibly opened is unavoidably left on the case. However, the battery has to be loaded or unloaded without breaking the case. Therefore, an opening through which only the battery is taken out is formed. A sealing member is disposed between the front case and the rear case to keep the case water-tight. A sealing surface which the sealing member contacts is molded not to leave any slide line of a molding die.

According to the present invention, the transponder contained in the case cannot be taken away without breaking the case. An owner of the portable transmitter easily recognizes the fact that the case was forcibily opened. Therefore, the possibility that an automobile is stolen using the taken-away transponder can be considerably reduced.

Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiment described below with reference to the following drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention will be described with reference to accompanying drawings. As an example of the portable transmitters of the present invention, a transmitter for used in a keyless-entry system of an automobile will be described. In the keyless-entry system, as well known, an identification code (ID code) is wirelessly transmitted to an automobile from a portable transmitter. When the ID code sent from the transmitter coincides with an ID code pre-stored in the automobile, the door is automatically locked or unlocked according to a signal showing an intention of the user. In this manner, the user of the automobile is able to lock or unlock the door without using a mechanical key from a position a certain distance apart from the automobile.

A keyless-starter system is also known hitherto. In the keyless-starter system, an automobile engine is automatically started upon receipt of an ID code wirelessly transmitted from a portable transmitter. Thus, the engine can be started without using a mechanical key in the similar manner as in the keyless-entry system. The portable transmitter according to the present invention is also applicable to other wireless control systems such as a system for starting a motor in an electric vehicle.

Referring toFIGS. 1–8, the structure and the function of the portable transmitter of the present invention will be described. The portable transmitter is composed of a resin case10and components contained therein. The components include a battery (a button-type)20, an electronic circuit board30, a transponder40and a mechanical key50.

The case10is composed of a front case11and a rear case12, both being connected not to be separated from each other (undetachably connected). The components of the transmitter are contained therein before the front case11is connected to the rear case12. The structure connecting the front case11to the rear case12is shown inFIG. 6in a scale enlarging a part of a cross-sectional view shown inFIG. 5. The front case11includes plural front hooks11aextending toward the rear case12, and the rear case12includes plural rear hooks12afor engaging with the front hooks11a.

As shown inFIG. 6, a projection11band a depression11care formed on the front hook11a. Similarly, projection12band depression12care formed on the rear hook12a. The projection11bof the front hook11aengages with the depression12cof the rear hook12a, and the projection12bof the rear hook12aengages with the depression11cof the front hook11a. A tapered surface11dis formed on the projection11bso that the projection11beasily engages with the depression12c. Similarly, a tapered surface12dis formed on the projection12bso that the projection12beasily engages with the depression11c. Engaging surfaces11eand12eof respective projections11band12bextend substantially in a longitudinal direction of the case10. Therefore, it is impossible to separate the front case11from the rear case12without breaking either one of the front hook11aor the rear hook12a. As also shown inFIG. 6, an O-ring18b(18a) as a first seal member is disposed between the front case11and the rear case12. The O-ring18bcontacts a sealing surface11hof the front case and a sealing surface12iof the rear case12.

As shown inFIG. 4, the battery20that supplies power to the electronic circuit board30is contained in the case10. The battery20can be loaded or unloaded through an opening12fformed in the rear case12without separating the front case11form the rear case12. A projected lip12gextending toward the opening12fserves as a member for preventing the battery20from dropping off. A battery cover13closing the opening12fis fixed to the rear case12with screws N (shown inFIG. 7). The battery cover13can be removed by loosening the screws N when necessary for replacing a worn battery with a new one. A second seal member14(an O-ring made of rubber) is disposed around the opening12fto be compressed with the battery cover13to thereby keep the inner space water-tight.

The rear surface of the transmitter is covered with a sliding cover15after the battery cover13is fixed to the rear case12with the screws N.FIG. 7shows the rear side of the transmitter with the sliding cover15removed, andFIG. 8shows the rear side with both of the battery cover13and the sliding cover15removed. The sliding cover15can be fixed to or removed from the rear surface by sliding the sliding cover15in the longitudinal direction of the case10.

As shown inFIGS. 7 and 8, a hook16afor stopping the sliding cover15at its position is provided on the rear surface of the case10. A lever16bconnected to the hook16ais provided at the bottom side of the case10. The hook16astopping the sliding cover15is released by operating the lever16b. The mechanical key50is contained in a space10aformed in the case10. The mechanical key50can be taken out from the space10aby releasing a key hook16cand by sliding the mechanical key50in the longitudinal direction of the case10. The key hook16cfunctions to fixedly contain the mechanical key50in the space10a. The key hook16cis connected to the lever16b. The key hook16ccan be moved to the position releasing the mechanical key50by operating the lever16b.

As shown inFIG. 4, the electronic circuit board30is formed by mounting tact switches32, an antenna33, a terminal34, an integrated circuit and other components on a printed circuit board31. The printed circuit board31is fixedly mounted on the rear case12from its front side. The tact switches32are positioned on the front surface of the printed circuit board31. The terminal34to be connected to a plus terminal of the battery20, another terminal to be connected to a minus terminal of the battery20, and the antenna33are mounted on the rear surface of the printed circuit board31.

The transponder40is press-fitted to the rear case12so that it can be firmly fixed to the rear case12. The transponder40is separated from the battery20by a separating wall12hto prevent the transponder40from being taken out from the opening12fwhen the battery cover13is removed. The electronic circuit board30is powered by the battery20and is adapted to automatically transmit the ID code. When the tact switch32is pushed by the user, the ID code is transmitted from the electronic circuit board30.

As shown inFIGS. 1,4and5, openings11fcorresponding to the respective tact switches32are formed on the front surface of the front case11. The openings11fare covered with a front film17that is integrally formed with the front case11. By pushing the front film17at a position corresponding to a particular tact switch32, the tact switch32can be operated. The front film17is formed by printing function displays17b,17c,17d(pictures or letters showing functions) on the rear surface of a transparent resin film17a. Since the function displays are printed on the rear surface, they are not erased by frequently touching the front surface. Background designs or pictures are also printed on the rear surface of the front film17to enhance the ornamental design of the transmitter by hiding the components located behind the front film17.

A repulsive force against a force pushing the tact switch32is a sum of a spring back force of the tact switch itself and a resilient force of the front film17. As the size of the opening11fbecomes smaller, the resilient force against the force pushing the tact switch32becomes larger. Therefore, the size of the opening11fis determined to obtain an optimum repulsive force against the force pushing the tact switch32.

As shown inFIG. 1, the function display17bcorresponds to a door-lock function,17cto a door-unlock function and17dto a trunk-opening function. That is, when the tact switch32corresponding to the function display17bis pushed, a signal for locking the door is transmitted. When the tact switch32corresponding to the function display17cis pushed, a signal for unlocking the door is transmitted. Similarly, when the tact switch32corresponding to the function display17dis pushed, a signal for opening a trunk is transmitted. Though four tact switches32are provided as shown inFIG. 4, only three functions are allocated to the respective tact switches32as shown inFIG. 1. Therefore, in this particular arrangement, one more function can be allocated to the vacant tact switch32.

The front film17is integrally molded together with the front case11, leaving the openings11fun-molded. Therefore, each opening11fis circularly surrounded by the molded portion. Thus, the openings11fare sealed by the molded portion and kept water-tight. A spacer11gformed together with the front case11by resin molding is disposed between the front film17and each tact switch32. The thickness of the spacers11gis different from spacer to spacer to adjust a distance between the front film17and each tact switch32. This adjustment is necessary because the front film17is not flat but curved as shown inFIG. 4. The plane shape of the spacer11gis substantially the same as the plane shape of the tact switch32. It is round in this particular embodiment. The plane area of the spacer11gis made a little larger than the plane area of the tact switch32.

As shown inFIG. 4(details shown inFIG. 6), a first sealing member18bis disposed between the front case11and the rear case12to seal the portion connecting both cases11,12. The first sealing member18bis integrally formed with a water-preventing cover18athat covers an entire surface of the electronic circuit board30. The first sealing member including the water-preventing cover18ais made of a rubber material.

Referring again toFIG. 1, a light source35such as a light emitting diode is provided in the case10, and the light from the light source35is emitted through a transparent portion17eof the front film17. In this embodiment, the light is lit when the battery voltage is normal, and the light is turned off when the battery voltage decreases to a level that is unable to operate the electronic circuit board30.

As shown inFIGS. 1 and 2, plural projections11iare formed on the front surface of the front case11, so that the user can recognize the top side and the bottom side of the transmitter by blind-touch. As seen inFIG. 4, portions of the front film17corresponding to the function displays17b,17c,17dare a little depressed from other portions, so that the user can find the respective function displays by blind-touch. Depressing the portions corresponding to the function displays also helps avoid unintended operation of the transmitter.

Now, operation of the transmitter will be described. First, operation under a normal condition where the battery voltage is normal, i.e., higher than a predetermined level will-be explained. When the transmitter is located within a first area which is apart from an automobile by a predetermined distance, a receiver mounted on the automobile receives the ID code automatically transmitted from the transmitter. If the ID code pre-installed in the receiver coincides with the ID code transmitted from the transmitter, an actuator for locking or unlocking the door is operated.

On the other hand, when the transmitter is located in a second area which is farther from the automobile than the first area, the ID code transmitted from the transmitter is not received by the receiver mounted on the automobile. In this case, the ID code is transmitted from the transmitter by manually pushing the tact switch32, and this ID code can be received by the receiver. Upon receiving the ID code, the actuator is similarly operated. In this manner, the door is locked or unlocked without using a mechanical key.

In the case of the keyless-starter system, when the user possessing the transmitter sits on the automobile seat, the ID code automatically transmitted from the transmitter is received by the on-board receiver. If the received ID code coincides with a pre-installed ID code, an ignition switch is turned on and an engine is started. Thus, the engine is automatically started without using a mechanical key.

Secondly, operation under an abnormal condition where the voltage of the battery20dropped to a voltage level that is unable to operate the electronic circuit board30for transmitting the ID code will be explained. The user may take out the mechanical key50contained in the transmitter by operating the lever16bto release the key hook16c. The user may lock or unlock the door with this mechanical key50.

When the user wants to start the engine under the abnormal condition, the user inserts the transmitter into a slot formed near a driver's seat. A caller installed in the slot sends a signal requesting the ID code to the transponder40contained in the transmitter. Electric power is automatically supplied to the transponder40from the automobile by means of electromagnetic induction, and the transponder40transmits the ID code to an on-board receiver. If the ID code received by the on-board receiver coincides with a pre-installed ID code, the ignition switch is turned on to start the engine. The ID codes mentioned above are all encrypted for security purpose.

FIG. 9shows relative positions of molding dies K1, K2and a slidable die K3used in a process of molding the front case11. The depression11cis formed by the slidable die K3that is slidably moved in direction X after the front case11is molded. All other portions of the front case11are formed by the molding dies K1and K2which are separated in direction Y after the front case11is molded. The sealing surface11hwhich contacts the first seal member18bis not formed by the slidable die K3, but it is formed by the molding die K1. In this manner, it is avoided to form a slide line L shown inFIG. 10Bon the sealing surface11h. If the slide line L is formed on the sealing surface11h, the portion connecting the front case11and the rear case12cannot be sufficiently sealed.FIG. 10Ashows a molding process in which the sealing surface11his formed by the slidable die K3. In this case the slide line L is formed on the sealing surface11has shown inFIG. 10B.

According to the present invention, the case10is formed by firmly connecting the front case11to the rear case12. Therefore, it is very difficult to open the case10without breaking the case10. If the case is forcibly opened to steal the transponder40contained therein, it is unavoidable to leave the trace. The owner of the transmitter immediately recognizes something unusual occurred to the transmitter. Therefore, the possibility that the door is open or the engine is started using the stolen transponder40can be considerably reduced.

The present invention is not limited to the embodiment described above, but it may be variously modified. For example, though the front hooks11aare provided in the front case11and the rear hooks12aare provided in the rear case12in the foregoing embodiment, only the front hooks11aor the rear hooks12amay be provided, eliminating the other hooks. Though the first area where the ID code is automatically transmitted and the second area where the ID code is manually transmitted are provided in the foregoing embodiment, it is, of course, possible to eliminate the first area. In other words, the ID code may be transmitted only by pushing the tact switch32.

The present invention is applied to the transmitter used in the keyless-entry system and the keyless-starter system in the foregoing description. However, the transmitter according to the present invention may be used in other systems. Further, application of the present invention is not limited to the automotive systems, but it may be applied to other systems such as a keyless entry system for doors of independent houses or apartment rooms.