Abstract:
A door handle for a vehicle which can miniaturize a transmitter provided on the vehicle and reduce a cost of the system is provided. The door handle includes a handle body which is mounted on an outer face of a door of the vehicle. A least a transmitting antenna of a transmitter which transmits a radio signal toward outside of the vehicle is integrated with the handle body. A smart key entry system for a vehicle using the door handle is also provided.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a door handle for a vehicle, and in particular to a door handle suited to be used in a vehicle which includes a transmitter for transmitting a radio signal. The present invention also relates to a smart entry system for a vehicle using the door handle. 
     2. Description of the Related Art 
     Conventionally, there is known an electronic key system which remote-controls lock/unlock of a door of a vehicle. For example, an electronic key system disclosed in Japanese Laid-Open Patent Application No. 5-156851 includes a wristwatch provided with a transmitter for generating ultrasonic waves modulated with a code for opening/closing operations of a door of a vehicle. A receiver is provided inside a door panel near the door handle for receiving the ultrasonic waves. The code for the opening/closing operations is demodulated from the received ultrasonic waves, and a key actuator is actuated in accordance with the demodulated code. 
     Recently, developments have been made of what is called a smart entry system in which a door of a vehicle is unlocked or locked when a user carrying a radio device comes close to or moves away from the vehicle. Such a smart entry system includes an onboard station which is provided on a vehicle and a portable station which is carried by a user. The onboard station transmits a radio request signal, and the portable station transmits a radio response signal including a predetermined code in response to the radio request signal transmitted by the onboard station. When the onboard station receives the radio response signal transmitted by the portable station, the onboard station compares the code included in the received response signal with a specific code. If the received code corresponds to the specific code, the onboard station unlocks the door. Thereafter, when the onboard station no longer receives the radio response signal from the portable station, the door is locked. 
     In such a smart entry system, if a transmitting antenna of the onboard station is provided inside a metallic door panel as in a case of the above-mentioned conventional electronic key system, an area in which the transmitted signal can reach (hereinafter referred to as a transmission area Ai) becomes narrower as shown in FIG. 1 for a higher frequency of the transmitted signal since the transmitted signal is shaded by the door panel to a greater extent. Thus, in order to enlarge the transmission area Ai, it is necessary to use a low frequency or large output power for the radio signal to be transmitted. In this case, a scale of a transmission circuit becomes larger and a cost of the system increases. 
     SUMMARY OF THE INVENTION 
     It is a first object of the present invention to provide a door handle for a vehicle which can miniaturize a transmitter provided on the vehicle and reduce a cost of the system. 
     It is a second object of the present invention to provide a smart entry system for a vehicle which can miniaturize a transmitter of an onboard station and reduce a cost of the system. 
     The first object of the present invention can be achieved by a door handle for a vehicle, the door handle comprising: 
     a handle body which is mounted on an outer face of a door of the vehicle; and 
     at least a transmitting antenna of a transmitter which transmits a radio signal toward outside of the vehicle, the at least a transmitting antenna being integrated with the handle body. 
     The second object of the present invention can be achieved by a smart entry system for a vehicle which includes an onboard station and a portable station, wherein the onboard station comprises: 
     a transmitter for transmitting a radio request signal via a transmitting antenna, at least the transmitting antenna being integrated with a door handle of the vehicle which is mounted on an outer face of a door of the vehicle; and 
     a receiver for receiving a radio response signal via a receiving antenna transmitted from the portable station in response to the radio request signal. 
     According to the inventions, since the radio signal is transmitted from the transmitting antenna which is integrated with the door handle mounted on an outer face of the door, the transmitted radio signal is not shaded by an outer door panel of the door. Accordingly, the radio signal can be transmitted from the antenna with a high efficiency without usage of a high frequency or a large output power. Thus, it is possible to miniaturize the transmitter and reduce a cost of the system while achieving a wide transmission area. 
     Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram showing a transmission area achieved by a conventional art; 
     FIG. 2 is a block diagram showing an onboard station of an example of a smart entry system in which a door handle according to the present invention is applied; 
     FIG. 3 is a block diagram showing a portable station of the smart entry system; 
     FIG. 4 is a diagram schematically showing a communication between the onboard station and the portable station; 
     FIG. 5 is a diagram showing a perspective view of a door of a vehicle; 
     FIG. 6 is a diagram showing a cross section of the door handle along a line A—A; 
     FIG. 7 is a diagram showing a cross section of the door handle along a line B—B; 
     FIG. 8 is a diagram showing a perspective view of a first transmitting antenna; 
     FIG. 9 is a diagram showing a perspective view of a handle case of the door handle; 
     FIG. 10 is a block diagram showing a first transmitting part; and 
     FIG. 11 is a diagram showing a transmission area achieved by the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 2 is a block diagram showing an onboard station  10  of an example of a smart entry system in which a door handle according to the present invention is applied. As shown in FIG. 2, the onboard station  10  includes a first transmitting antenna  11  and a second transmitting antenna  12 . The first transmitting antenna  11  is provided inside a door handle of a door of a vehicle. On the other hand, the second transmitting antenna  12  is provided near an instrument panel inside a cabin of the vehicle. The first transmitting antenna  11  is connected to a first transmitting part  14 , and the second transmitting antenna  12  is connected to a second transmitting part  16 . The first transmitting part  14  and the second transmitting part  16  are connected to an ECU (electronic control unit)  20 . 
     The ECU  20  supplies first and second request codes to the first transmitting part  14  and the second transmitting part  16 , respectively. The first transmitting part  14  and the second transmitting part  16  modulate radio signals having a frequency f 1  (134 kHz, for example) with the first and second request codes, respectively. The modulated request signals are transmitted from the first transmitting antenna  11  and the second transmitting antenna  12 , respectively, toward a portable station  60  which will be described below. It should be noted that the first transmitting part  14  and the second transmitting part  16  may be integrally constructed as a single circuit. 
     A receiving antenna  22  is provided inside an inner mirror of the vehicle for receiving a signal having a frequency f 2  (300 MHz, for example) transmitted by the portable station  60 . The signal received by the receiving antenna  22  is demodulated in a receiving part  24  and then supplied to the ECU  20 . 
     A memory  26  is connected to the ECU  20 . The memory  20  contains a plurality of different codes stored therein such as a first code for locking the door, a second code for starting an engine and a transponder ID code. The memory  26  is a non-volatile memory such as an EEPROM. Thus, contents stored in the memory  26  are maintained if power supply to the memory  26  is shut off. 
     An operation detecting part  28  detects operations of various switches by a user. For example, when the operation detecting part  28  detects an operation of an ignition switch, the operation detecting part  28  supplies a detection signal indicating the operation of the ignition switch to the ECU  20 . A door opening/closing detecting part  30  detects opening/closing of a door on a side of a driver seat (or each door of the vehicle) and supplies a detection signal to the ECU  20 . A sensor group  32  includes various sensors for detecting a vehicle speed and opening/closing of a window. These sensors supply detection signals to the ECU  20 . 
     Additionally, a steering lock part  40 , an immobilizer part  42  and a door lock part  44  are connected to the ECU  20 . The steering lock part  40  mechanically prohibits a steering operation. The immobilizer part  42  prohibits fuel supply and ignition of an engine  50 . The door lock part  44  locks and unlocks each door of the vehicle. 
     Further, an engine control part  48  is connected to the ECU  20 . The engine control part  48  controls a start operation of the engine  50  by means of a cell motor, as well as a regular operation of the engine  50 . 
     FIG. 3 is a block diagram showing the portable station  60  of the smart entry system. As shown in FIG. 3, the portable station  60  includes a transmitting antenna  62  and a receiving antenna  64 . These antennas  62 ,  64  are connected to a transmitting/receiving circuit  66 . The transmitting/receiving circuit  66  is connected to an ECU  68 . When the receiving antenna  64  receives the request signal having the frequency fi transmitted by the onboard station  10 , the received signal is demodulated in the transmitting/receiving circuit  66  and then supplied to the ECU  68 . 
     A memory  70  is connected to the ECU  68 . The memory  70  contains first and second codes stored therein. The first and second codes are read out from the memory  70  and supplied to the transmitting/receiving circuit  66  by the ECU  68 . These first and second codes are modulated in the transmitting/receiving circuit  66  and transmitted as a radio signal having the frequency f 2  (300 MHz, for example) from the transmitting antenna  62  toward the onboard station  10 . 
     FIG. 4 schematically shows an example of a communication between the onboard station  10  and the portable station  60 . As shown in FIG. 4, the first and second request signals having the frequency f 1  are transmitted from the first and second transmitting antennas  11 ,  12  of the onboard station  10 , respectively. When the portable station  60  receives the first request signal (when the portable station  60  is outside the vehicle) or the second request signal (when the portable station  60  is inside the vehicle), the portable station  60  transmits a signal having the frequency f 2  which is modulated with the first or second code in accordance with the received request signal. When the signal transmitted by the portable station  60  is received by the receiving antenna  22  provided inside the inner mirror, the received signal is demodulated in the receiving circuit  24  and then supplied to the ECU  20 . Thus, the ECU  20  can detect the first or second code transmitted by the portable station  60 . 
     FIG. 5 shows a perspective view of a door  80  of the vehicle. As shown in FIG. 5, a door handle  82  of a grip type according to the present invention is mounted to a metallic outer door panel  84  of the door  80  so that the door handle  82  projects outwardly in a lateral direction of the vehicle. The door handle  82  has a shape of a bent pipe and is fixed to the outer door panel  84  at both ends thereof. Thus, the door  80  can be opened and closed by gripping a grip part in the intermediate part of the door handle  82  by a human hand. 
     FIGS. 6 and 7 show cross sections of the door handle  82  along a line A—A and a line B—B, respectively. As shown in FIG. 6, a handle grip part  86  of the door handle  82  has a hollow structure constituted by a combination of a plastic handle case  87  which is provided on an outer side of the vehicle and a plastic or metallic handle case  88  which is provided on an inner side of the vehicle. The first transmitting antenna  11  is disposed inside the handle grip part  86 . 
     As shown in FIG. 7, an arm  90  extends from one end  82 A of the door handle  82 . The arm  90  is inserted into the door  80  through the outer door panel  84 . A tip of the arm  90  is pivotably connected to a pivot shaft  92 . On the other side, a lever  94  extends from the other end  82 B of the door handle  82 . The lever  94  is inserted into the door  80  through the outer door panel  84 . A tip of the lever  94  is connected to a door opening/closing mechanism which is not shown in the figures. 
     When the handle grip part  86  is gripped by a human hand and pulled outwardly in a lateral direction of the vehicle, the lever  94  pivots around the pivot axis  92  in a direction indicated by an arrow X. Thus, the door  80  is opened by the door opening/closing mechanism being actuated. A door key cylinder  96  is mounted to the door  80  near the lever  94  by being inserted into the door handle  82  through the outer door panel  84  so that a keyhole face thereof is exposed outside. 
     As shown FIGS. 6 and 7, the first transmitting antenna  11  is disposed inside the handle grip part  86 , and the first transmitting part  14  (including a current detecting circuit  122  which will be described below) is mounted on an inner side of the outer door panel  84 . The first transmitting antenna  11  and the first transmitting part  14  are connected by a wire harness  98  which extends inside the door handle  82  and the arm  90 . Additionally, the first transmitting part  14  is connected to the ECU  20  by a wire harness  100 . 
     FIG. 8 shows a perspective view of the first transmitting antenna  11 . As shown in FIG. 8, a case  102  which is made of resin has an elongated plate-like shape with a center part thereof being cut oit. A ferrite plate  104  is supported in the cut-out part of the case  102 . A coil  106  is wound around a peripheral edge of the case  102 . The coil  106  is connected to a condenser  108  and the wire harness  98  to constitute the transmitting antenna  11 . The condenser  108  is disposed adjacently to the case  102  in a longitudinal direction of the case  102 . It should be noted that the case  102  may be made of ferrite. In this case, it is not necessary to cut out the center part of the case  102 . 
     In an assembling process of the door handle  82 , the first transmitting antenna  11  is fitted and fixed in an antenna containing part  110  provided inside the metallic handle case  88  shown in FIG.  9 . Then, the antenna containing part  110  is filled with a waterproofing material (silicone, for example). Thereafter, the plastic handle case  87  is mounted to the handle case  88  to form the handle  82 . 
     As shown in FIG. 10, the first transmitting part  14  is provided with the current detecting circuit  122  in addition to a transmitting circuit  120 . The current detecting circuit  122  detects a current flowing though the first transmitting antenna  11 . When a human hand touches the handle grip part  86  to open the door  80 , a stray capacitance of the first transmitting antenna  11  increases so that a current flowing through the first transmitting antenna  11  momentarily changes. The current detecting circuit  122  detects a contact of a human hand to the handle grip part  86  by detecting the above-mentioned current change and supplies a detection signal to the ECU  20 . 
     As mentioned above, the first transmitting antenna  11 , which is a part of a transmitter, is disposed inside the door handle  82  which outwardly projects from the door  80  so that the transmitting antenna  11  is positioned outside the door  80 . Since the request signal can be transmitted from the first transmitting antenna  10  through the plastic handle case  87 , the request signal is not shaded by the door  80 . Thus, it is possible to use a relatively high frequency and relatively small output power for the request signal while achieving a wide transmission area Ai as shown in FIG.  11 . Additionally, the door handle  82  can be miniaturized since only the first transmitting antenna  11  is disposed inside the door handle  82 . 
     In the above-mentioned embodiment, the receiving antenna  22  is disposed inside the inner mirror of the vehicle. However, the receiving antenna  22  may be disposed at any position where radio signals from outside the vehicle can be received. For example, the receiving antenna  22  may be provided at a center of the vehicle so as to be used as a common antenna for both sides of a driver seat and a passenger seat, or the receiving antenna  22  may be separately provided to each side of a driver seat and a passenger seat inside the door handle or the door. 
     The present invention is not limited to these embodiments, but variations and modifications may be made without departing from the scope of the present invention. 
     The present application is based on Japanese priority application No. 10-343296 filed on Dec. 2, 1998, the entire contents of which are hereby incorporated by reference.