KEYLESS VEHICLE ENTRY APPARATUS

Abstract: A keyless entry apparatus for locking and unlocking a door, trunk lid, and a window of a vehicle. The electric waves radiated from a transmitter (104) are received by a pickup (102) which is provided on a vehicle body in a concealed state without any external exposure which would impair the aesthetic appearance of the vehicle body. The pickup consists of a loop antenna or an electrostatic detection antenna which detects the surface currents induced on the vehicle body by the electric waves radiated from the transmitter. The pickup is disposed at a portion on which the surface currents are concentrated such as, for example, a front pillar (100), trunk lid and roof.

Description: The present invention relates to keyless vehicle entry apparatus. Keyless vehicle entry apparatus designed to automatically lock or unlock a door on receiving a coded signal of very low power from a transmitter have recently come into general use, in particular for high-quality cars wherein such an apparatus replaces a conventional door locking device in which a key is used. It is possible to provide such a keyless vehicle entry apparatus not only for the vehicle door but also for other vehicle entries such as, for example, opening and closing a trunk or a window, or warning of a possible car-theft, thereby providing many advantages for the driver or owner of the vehicle. In such a conventional keyless vehicle entry apparatus, as exemplified by that shown in Fig. 28, a coded signal consisting of electric waves (of 60 MHz in the example shown in Fig. 28) transmitted by a transmission antenna 12 of a transmitter 10 is received by a pole antenna 16 for radio broadcast wave reception which is provided on vehicle body 14, and the received signal is fed to a divider 20 through a feeder line 18. The divider 20 divides the received signal into the inputs of a radio 22 and a keyless entry signal receiver 24. As a result, an audio signal is emitted from the speaker 26 of the radio 22, and a control signal 28 for locking or unlocking a door is supplied from the keyless entry signal receiver 24. Such a conventional keyless vehicle entry apparatus, however, which divides a received signal into two, causes a drop in the receiving sensitivity for radio broadcast waves by about 3 dB. Furthermore, since the antenna for radio broadcast wave reception is adjusted mainly for radio broadcasting frequency bands, in particular, for the FM band (76 to 90 MHz in Japan), adequate sensitivity is sometimes unobtainable for the carrier frequency (60 MHz) of the electric waves which are generally used for propagating a coded signal in a keyless vehicle entry apparatus. In addition, in a strong electric field zone, such as in the vicinity of a transmitting station for FM broadcasts or TV broadcasts, a strong input jamming occurs, and this necessitates such counter-measures as filtering and trapping. Thus to solve the above two problems it is necessary to provide an antenna exclusively for use by the keyless vehicle entry apparatus. However, although a pole antenna which projects outwardly from the vehicle body is superior in performance in its own way, it always remains a nuisance from the point of view of vehicle design. Furthermore, such a pole antenna is disadvantageous in that it is subject to damage, tampering or theft and also in that the antenna tends to generate noise during high-speed driving. For these reasons, there has heretofore been a strong desire to eliminate the need for such pole antennas, and thus to provide a pole antenna once again would be at variance with current circumstances. One of the proposals made to eliminate such problems has been to provide a receiving loop antenna for a keyless vehicle entry apparatus on a moulding located in the vicinity of the outside handle of a door (Japanese Patent Laid-open No. 44861/1984). This keyless vehicle entry apparatus is advantageous in that the electric waves from a transmitter can be positively received without changing the external form or appearance of a vehicle body. Such an improved keyless vehicle entry apparatus, however, is comparatively low in sensitivity, and, in addition, it is necessary from the viewpoint of its directional characteristics to dispose a transmitting antenna in close proximity (at a distance of about 10 cm) to the receiving loop antenna. Thus, it is not possible to enjoy the full advantage of the keyless vehicle entry apparatus which can automatically lock and unlock a door when the operator is standing at a certain distance from the vehicle body. Accordingly, it is an object of the present invention to provide a keyless vehicle entry apparatus having good operability and which does not affect the aesthetic appearance of a vehicle body, thereby eliminating the above-described problems. The prior art, for example as shown in Figure 28 hereof, teaches a keyless vehicle entry apparatus comprising a portable transmitter operable to transmit a coded signal at a predetermined radio frequency, and receiving equipment adapted to be carried by a vehicle; said receiving equipment comprising: an antenna system to receive said transmitted signal, signal processing means to decode the received signal, and means to generate a control signal for causing locking or unlocking of a vehicle entry in response to a decoded received signal having a predetermined characteristic. The present invention is characterized in that: said antenna system comprises a pick-up mounted adjacent a sheet metal member forming a portion of the vehicle body to detect radio frequency surface currents induced in said sheet metal member by transmitted radio frequency signals and which have a concentrated flow along a marginal edge portion of said sheet metal member; said pick-up comprising a casing formed of electrically conductive material and having an elongate opening, and an elongate loop antenna disposed within said casing with a longer side thereof exposed through said opening; mounting means mounting said casing to said vehicle body portion so that said exposed longer side of said loop antenna extends lengthwise of and closely adjacent said marginal edge portion; and said pick-up being adapted to receive only signals in a narrow frequency band including the predetermined transmission frequency. The invention thus makes it possible to build the pick-up within the vehicle body so that it does not affect the aesthetic appearance of the vehicle body. It is also possible to provide such a pick-up exclusively for the keyless vehicle entry apparatus and thus to exclude jamming waves from broadcasting stations, transmission lines or the like by setting the reception frequency in a selected narrow frequency band. It is further possible to provide a substantially non-directional keyless vehicle entry apparatus by providing two or more such pick-ups on the vehicle body so that they tend to compensate for one another with respect to directivity. DE-A-1949828 describes a vehicle antenna system comprising an antenna mounted adjacent a sheet metal member forming a portion of the vehicle body to detect radio frequency surface currents induced in said sheet metal member by broadcast radio frequency signals. An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 shows a first embodiment of keyless vehicle entry apparatus according to the present invention; Fig. 2 illustrates the directional pattern of a pick-up used in the first embodiment. Figs. 3 to 5 show the arrangement for attaching the pick-up used in the first embodiment to a vehicle body; Figs. 6 to 8 show the arrangement for attaching the pick-up used in a second embodiment of a keyless vehicle entry apparatus to a vehicle body; Figs. 9 to 11 show the arrangement for attaching the pick-up used in a third embodiment of a keyless vehicle entry apparatus to a vehicle body; Figs. 12 to 15 show the arrangement for attaching the pick-up used in a fourth embodiment of a keyless vehicle entry apparatus to a vehicle body; Figs. 16 to 17 show the arrangement for attaching the pick-up used in a fifth embodiment of a keyless vehicle entry apparatus to a vehicle body; Figs. 18 to 20 show the arrangement for attaching the pick-up used in a sixth embodiment of a keyless vehicle entry apparatus to a vehicle body; Fig. 21 shows a seventh embodiment of a keyless vehicle entry apparatus according to the present invention; Fig. 22 illustrates the directional patterns of the pick-ups used in the seventh embodiment; Fig. 23 illustrates the directional patterns of the pick-ups used in another embodiment; Fig. 24 illustrates the directional patterns of the pick-ups used in still another embodiment; Fig. 25 illustrates the directional patterns of the pick-ups used in a further embodiment; Fig. 26 illustrates the directional patterns of the pick-ups used in a still further embodiment; Fig. 27 illustrates the directional patterns of the pick-ups used in a still further embodiment; Fig. 28 shows the structure of a conventional keyless vehicle entry apparatus; Fig. 29 illustrates surface currents I induced on the vehicle body B by the electric waves W from a transmitter; Fig. 30 illustrates a probe for detecting the distribution of surface currents on the vehicle body and having the same construction as that of a pick-up used in the present invention, and a circuit for processing signals from the probe; Fig. 31 illustrates the electromagnetic coupling between the surface currents I and the loop coil of the pick-up; Fig. 32 illustrates the directional pattern of the loop antenna shown in Fig. 31; Fig. 33 illustrates the intensity distribution of the surface currents; and Fig. 34 illustrates the directions of flow of the surface currents. Figs. 29 to 34 illustrate a process for examining the distribution characteristics of high-frequency currents so as to ascertain the location at which a pick-up can operate most efficiently on the vehicle body of an automobile. The structure shown in Figs. 29 to 34 is also shown in Figs 5 to 10 of our EP-A-182497 and in others of our co-pending European Patent Applications relating to vehicle antennae, all being documents of the type described in Article 54 (3) of the European Patent Convention. Fig. 29 shows that when the electric waves W from a transmitter pass through the vehicle body B of conductive metal, surface currents I are induced at various vehicle locations at levels corresponding to the intensities of electromagnetic waves passing therethrough. The present invention is concerned primarily with electromagnetic waves of relatively high frequency bands of 60 MHz which are desirably used for transmitting coded signals in a keyless vehicle entry apparatus. The distribution of the surface currents induced on the vehicle body by electromagnetic waves within the above-described particular wave bands is measured so as to seek a location on the vehicle body which is higher in surface current density and lower in noise and at which a pick-up to be used in the present invention can be located. The distribution of surface currents is determined by a simulation using a computer and also by measuring actual intensities of surface currents at various locations on a vehicle body. The measurement is carried out by the use of a probe which can operate in accordance with the same principle as that of a pick-up, actually located on the vehicle body at a desired location, as will be described later. Such a probe is moved on the vehicle body over the entire surface thereof to measure the level of surface currents at various locations on the vehicle body. Fig. 30 shows an example of such a probe P which is constructed in accordance with substantially the same principle as that of the pick-up described hereinafter. The probe P is composed of a casing 40 of electrically conductive material for preventing any external electromagnetic wave from transmitting to the interior thereof and a loop coil 42 fixed within the casing 40. The casing 40 includes an opening 40a formed therein through which a portion of the loop coil 42 is externally exposed. The exposed portion of the loop coil 42 is located in close proximity to the surface of the vehicle body B to detect magnetic flux induced by surface currents on the vehicle body B. Another portion of the loop coil 42 is connected to the casing 40 through a short-circuiting line 44. The loop coil 42 further includes an output end 46 connected to a core 50 in a coaxial cable 48. Still another portion of the loop coil 42 includes a capacitor 52 for causing the frequency in the loop coil 42 to resonate relative to the desired frequency to be measured (60 MHz, in Fig. 30) to increase the efficiency of the pick-up. Thus, when the probe P is moved along the surface of the vehicle body B and also angularly rotated at various locations of measurement, the distribution and direction of surface currents can accurately be determined at each of the vehicle locations. In Fig. 30, the output of the probe P is amplified by a high-frequency voltage amplifier 54 and the resulting output voltage is measured by a high-frequency voltmeter 56. This coil output voltage is read at the indicated value of the high-frequency voltmeter 56 and also is recorded by an XY recorder 58 to provide the distribution of surface currents at various vehicle locations. The input of the XY recorder 58 receives signals indicative of various locations on the vehicle from a potentiometer 60 to recognize the value of the surface currents at the corresponding location. Fig. 31 illustrates an angle ϑ of deflection between the high-frequency surface currents I and the loop coil 42 of the pick-up. As is clear from the drawing, magnetic flux  interlinks with the loop coil to generate a detection voltage V in the loop coil 42. As shown in Fig. 31, when the angle ϑ of deflection is equal to zero, that is, the surface currents I are parallel to the loop coil 32 of the pick-up, the maximum voltage can be obtained. The direction of the surface currents I when the probe P is rotated to obtain the maximum voltage can also be known. Figs. 33 and 34 respectively show the magnitude and direction of high-frequency surface currents induced at various different locations on the vehicle body at the frequency of 60 MHz, the values of which are obtained from the measurements by the probe P and the simulation effected by the computer. As is clear from Fig. 33, the distribution of surface currents has higher densities at the marginal edge of the vehicle body and lower densities at the central portion of the flat vehicle panels. It will also be apparent from Fig. 34, that the surface currents are concentrated in the direction parallel to the marginal edge of the vehicle body or in the direction along the connections of various flat panels. Additionally, the value of the current decreases in correspondence with the distance from the edge of the metal flat portion of the vehicle body. Since the range under 6 dB is the lower limit for currents in which good sensitivity is actually obtainable, very good sensitivity may be obtained if the pick-up is disposed within a distance of 4.5 cm from the peripheral edge. Fig. 1 shows a first embodiment of a keyless vehicle entry apparatus according to the present invention. A pick-up 102 having a similar structure to the above-described probe is disposed at a front pillar 100 to detect the surface currents which flow concentratedly on the front pillar 100. The center of the receiving band for the pick-up 102 is adjusted to be 60 MHz, and the pick-up 102 is enabled to receive only high-frequency surface currents in a narrow band by impedance matching, so that the influence of jamming waves such as FM broadcast waves or TV broadcast waves is reduced. A keyless vehicle entry apparatus in accordance with this embodiment includes a transmitter 104 which is operated by the user and a receiver 106 provided in the vehicle body, and when the pick-up 102 detects surface currents induced by the electric waves from the transmitter 104, the receiver 106 electrically processes them. The transmitter 104 includes a crystal oscillator 108 which has a frequency of 60 MHz, and an RF amplifier 112 which amplifies the signal and supplies it to a transmitting antenna 110, and the RF amplifier 112 is controlled by the user. The transmitter 104 includes a key operation switch 114 which is turned on or off by the user, and in accordance with the operation process or operation timing of the switch 114, a code setting circuit 116 receives an electrical input signal. The output of the code setting circuit 116 is converted to a desired electrical signal by an encoder 118, and the coded signal controls the output of the RF amplifier 112 through a modulator 120. Thus, according to the transmitter 104 shown in Fig. 1, a desired modulated keyless entry signal is transmitted from the transmitting antenna 110 by the keyless entry operation, namely, the operation of the switch 114 by the user. On the vehicle body, high-frequency surface currents are induced by the electric waves from the transmitter 104, and the pick-up 102 receives the above-described transmitted keyless entry signal from the surface currents, and supplies it to an RF amplifier 124 of the receiver 106 where it is subjected to a desired amplifying operation. The amplified signal is mixed by a mixer 126 with a local oscillating frequency signal of, e.g., 59.545 MHz of a local oscillator 128, and is further amplified by an intermediate frequency amplifier 130. The amplified signal is demodulated and detected by a detection circuit 132, and is decoded by a decoder 134 to the code set by the user. The receiver 106 feeds the decoded signal as a control signal 136 which is to be used for locking or unlocking a door, or for other purposes. Fig. 2 shows the directional characteristic of the pick-up in the 60 MHz frequency band which is provided on the left-hand front pillar of the vehicle body in the first embodiment. As is shown in the characteristic curve 138, the pick-up has good sensitivity on the right-hand side of the vehicle body, and slightly lowered sensitivity in the forward and backward directions of the vehicle body. In other words, the keyless vehicle entry apparatus in accordance with this embodiment has good sensitivity on the driver's seat side (in Japan and the U.K. at least) where there is the greatest likelihood of the keyless entry operation being effected, thereby securing a good operability with respect to keyless entry operation. The arrangement for attaching the pick-up to the front pillar will now be explained in detail with reference to Figs. 3 to 5. The structure shown in Figs. 4 and 5 is also shown in Figs. 2 and 3 of our EP-A-182497. In Fig. 3 is shown the schematic structure of the pick-up attached to the front pillar. The pick-up 102 is accommodated in the front pillar 100 for supporting the roof panel. In the embodiment, the pick-up 102 consists of an electromagnetic type pick-up which includes a loop coil. As is clear from the sectional view of Fig. 4, the pillar 100 includes a pedestal plate 150 which serves as the main pillar and has a configuration of a hollow prism. A windshield molding 152 is secured to the surface of the pedestal plate 150 which faces the exterior of the vehicle body, and the molding 152 retains a front windshield glass 154. A weather strip rubber 156 is secured to the surface of the pedestal plate 150 which faces the rear portion of the vehicle body, thereby maintaining the water-sealed state of the joint between a side window glass 158 and the pedestal plate 150. A front pillar garnish 160 is mounted on the surface of the pedestal plate 150 which faces the interior of the vehicle body to enclose the surface of the pedestal plate 150, thereby maintaining the aesthetically pleasing appearance of the vehicle body. The pick-up is longitudinally disposed on the front pillar 100, and in the example shown in Fig. 4, the pick-up 102 of electromagnetic coupling type is inserted into the hollow portion of the pedestal plate 150. The pick-up 102 is composed of a casing 162 of a conductive material and an elongate loop coil 164 which is provided within the casing 162 and constitutes an antenna element, as is shown in Figs. 4 and 5. The casing 162 for shielding the loop coil from external magnetic flux is provided with an elongate opening 162a at one side thereof. A longer side of the loop coil 164 is exposed from the opening 162a and is disposed in proximity to the pillar where high-frequency surface currents flow concentratedly, in particular, to the pedestal plate 150. In order to insert the pick-up 102 into the hollow prism of the pillar pedestal 150, an opening 150a is provided on a part of the pillar pedestal 150. The pick-up 102 is inserted into the pillar before the front garnish 160 is fixed. In order to secure the casing 162 of the pick-up 102 to the pedestal plate 150, brackets 166, 168 are fixed to both sides of the casing 162 by spot welding or the like, and the brackets 166, 168 are tightly screwed to the pedestal plate 150. Accordingly, the loop coil 164 in this fixed state is disposed in the vicinity of the opening 150a of the pedestal plate 150, whereby the magnetic flux induced by the surface currents which flow concentratedly on the pedestal plate 150 are effectively interlinked with the loop coil 164. Circuitry 170 including a pre-amplifier and the like is housed behind the loop coil 164 in the casing 162. Power source and a signal for controlling the circuit is supplied from a cable 172 to the circuitry 170, and the high-frequency detection signal detected by the loop coil 164 is fed through a coaxial cable 174 and is processed by a circuit similar to that used for examining distribution of surface currents. The loop coil 164 is in the form of a single wound coil which is covered with electrical insulation such that the coil can be arranged in an electrically insulated relationship with and in close contact with the pedestal plate 150. Preferably the loop coil 164 is attached to the peripheral edge of the pedestal plate 204. Thus, the magnetic flux induced by the surface currents concentratedly flowing on the pedestal plate 150 can interlink with the loop coil 164 with efficiency. After the pick-up 102a is inserted into the front pillar 100 in this way, the front pillar 100 is covered with the front pillar garnish 160. Thus, the structure of the front pillar 100 is the same as an ordinary pillar in terms of external appearance. As a result, the high-frequency surface currents which are concentrated and flow on the front pillar are detected with efficiency by the loop coil which is longitudinally provided there, thereby ensuring reception in the high-frequency bands without any external exposure of the antenna system. A second embodiment of a keyless vehicle entry apparatus according to the present invention will be explained, in which a pick-up is longitudinally disposed at the peripheral edge of the engine hood. In this embodiment, the pick-up is disposed on the rear peripheral end portion of the engine hood and its directional characteristic has high sensitivity in the forward direction of the vehicle body. The arrangement for attaching the pick-up to the engine hood will be explained in detail with reference to Figs. 6 to 8. The structure shown in Figs. 6 to 8 is also shown in Figs. 6 to 8 of our EP-A-180462. In Fig. 6, an engine hood 200 is rotatably supported by the vehicle body at one end thereof, and in its closed state, the inner surface of the peripheral end portion which faces the front windshield glass 154 is opposed to a front outer panel 202. The inside of the front outer panel 202 is connected to a front inner panel 204 and the front windshield glass 154 is supported on the front outer panel 202 by a stopper 206. A dam 208 is provided between the front windshield glass 154 and the front inner panel 204, thereby preventing the ingress of rainwater or the like. At the lower end of the front windshield glass 154, as is known, a molding 210 is provided. A pick-up 212 in this embodiment has a similar structure to the pick-up used in the first embodiment, and includes a casing 214, a loop coil 216 and circuitry 218. The pick-up 212 is fixed within a distance of 6.0 cm from the peripheral portion, in particular, the peripheral edge of the engine hood which faces the front outer panel 201, whereby it is possible to positively detect the high-frequency surface currents which flow concentratedly with high density on the peripheral portion of the engine hood. Fig. 7 shows the structure of the pick-up 212 which is attached to the engine hood 200, and Fig. 8 is an external view of the pick-up to be attached to the engine hood. The detail is approximately the same as that in the first embodiment. The pick-up 212 is attached to the engine hood 200 by brackets 220 and 222, and a screw 224. Power source and a signal for controlling the circuitry are supplied from a cable 226, and a high-frequency detection signal is fed out by a coaxial cable 228. It is necessary to select the location of the pick-up so as not to obstruct the accommodation of the wiper blades. The structures of the transmitter and the receiver in this embodiment are the same as those in the first embodiment, and explanation thereof will therefore be omitted. A third embodiment of a keyless vehicle entry apparatus according to the present invention will be explained, in which a pick-up is disposed at the peripheral portion of the trunk lid. In this embodiment, the pick-up exhibits highly sensitive directivity in the backward direction of the vehicle body. The arrangement of the pick-up to the trunk lid will be explained in detail with reference to Figs. 9 to 11. The structure shown in Figs. 9 to 11 is also shown in Figs. 1, 3 and 4 of our EP-A-180462. In Fig. 9, a water sealing weather strip 304 is provided between a trunk lid 300 and a rear tray panel 302 so as to prevent the ingress of rainwater or the like from a rear window glass 306. A dam 308 provided between the rear window glass 306 and the rear tray panel 302 maintains airtightness and prevents the ingress of rainwater, sound or the like. A molding 310 is provided at the lower end of the rear window glass 306 on the external side, as is known. In this embodiment, the pick-up 312 is fixed at the peripheral end portion of the trunk lid 300 which faces the rear tray panel 302, and the pick-up 312 consists of an electromagnetic coupling type pick-up having a similar structure to that used in the first embodiment. As is clear from Fig. 9, the loop coil 314 provided in the pick-up 312 is disposed such that the longitudinal direction thereof agrees with the longitudinal direction of the trunk lid 300. The loop coil 314 is disposed within a distance of 6.0 cm from the peripheral edge of the trunk lid 300, so that the loop coil 314 acquires with efficiency the surface currents which flow concentratedly on the peripheral portion of the trunk lid 300. Since surface currents flow on the vehicle body along the marginal edge portions thereof, as is shown in Fig. 34, the loop coil 314 is longitudinally disposed on the peripheral portion of the trunk lid 300. The pick-up in this embodiment, as is the case with the first embodiment, includes a casing 316 of a conductive material. The casing 316 accommodates a loop coil 314 and circuitry 318, and has an opening 316a which is opposed to the trunk lid 300. Thus, the magnetic flux which is induced by the high-frequency surface currents flowing on the peripheral portion of the trunk lid 300 is introduced into the casing 316, which shields the loop coil 314 from external magnetic flux. Power source and a signal are supplied to the circuitry 318 from a cable 320, and a high-frequency detection signal is fed out by a coaxial cable 322, and is processed by a circuit similar to that explained in the first embodiment. In this way, according to this embodiment, since high-frequency surface currents are detected by means of the pick-up from the inside of the trunk lid, reception of a keyless entry signal is enabled without any external exposure of the antenna system. Fig. 10 shows the arrangement of the pick-up 312 to the trunk lid 300. The same numerals are provided for those elements which are the same as those shown in Fig. 9, and explanation thereof will be omitted. Brackets 324 and 326 are attached to the side surfaces of the casing 316 of the pick-up 312 by bolts or the like, and the brackets 324 and 326 are secured to the inner panel of the trunk lid 300 by screws 328, thereby rigidly securing the pick-up 312 to the inside of the trunk lid 300. Therefore, the pick-up 312 is preferably constructed as shown in Fig. 11. A fourth embodiment of a keyless vehicle entry apparatus according to the present invention will be explained, in which a pick-up is provided in the vicinity of the rear roof of a vehicle body. If the pick-up in this embodiment is disposed at the rear right-hand corner of the roof, the apparatus exhibits good receiving sensitivity on the right-hand side of the vehicle body, namely, on the driver's seat side where it is most likely that the keyless entry operation will be effected. Thus it is to be understood that the above-described position is a preferred location. The arrangement for attaching the pick-up to the rear roof will be explained in detail hereinunder with reference to Figs. 12 to 15. A metal roof panel 400 which is illustrated in the exposed state is connected to a rear glass window 404 with a rear window frame 402 as its marginal end. A pick-up 406 is provided within a distance of 6.0 cm from the edge of the rear window frame 402. As in the first embodiment, the pick-up 406 includes a casing 408, a loop coil 410, circuitry 412, a cable 414, a coaxial cable 416 and brackets 418 and 420. Fig. 14 is a cross-sectional view of the pick-up 406 which is fixed to the roof panel. The roof panel includes a roof panel 422, to one end of which the rear window frame 402 is secured. The rear window glass 404 is secured to the roof panel 422 through a fastener 424 and a dam 426, these two being rigidly bonded by an adhesive 428. A molding 430 is fixed between the roof panel 422 and the rear window glass 404. An opening 402a for receiving the casing 408 of the pick-up 406 is provided on a part of the rear window frame 402 in order that the loop coil 410 of the pick-up 406 is opposed to the peripheral portion of the rear window frame 402. The casing 408 is provided with an opening 408a such that a longitudinal side of the loop coil 410 is exposed therefrom. In this manner, a part of the loop coil 410 exposed from the casing 408 of a conductive material is opposed in proximity to the peripheral portion of the rear window frame 402. After the pick-up 406 is secured to the exposed roof panel, in particular, to the rear window frame 402 in this manner, a roof garnish 432 is secured to the roof panel, and an edge molding 434 is fixed at the end portions of the roof garnish 432 and the rear window frame 402. A signal output from the pick-up provided in the above-described way is processed in a circuit similar to that in the first embodiment. In a fifth embodiment of a keyless vehicle entry apparatus according to the present invention, a pick-up is disposed on the front roof of a vehicle body. If the pick-up in this embodiment is disposed at the front right-hand corner of the roof, the apparatus exhibits good receiving sensitivity on the right-hand side of the vehicle body, namely, on the driver's seat side where it is most likely that the keyless entry operation will be effected. Thus it is to be understood that the above-described position is a preferred location. The detail of the arrangement for attaching the pick-up to the front roof will be described in the following with respect to Figs. 16 and 17. The structure shown in Figs. 16 and 17 is also shown in Figs. 5 and 6 of our EP-A-181120. The pick-up 500 in this embodiment is disposed in a service hole 502a of the header inner panel 502. As is clear from Fig. 17, a front windshield glass 154 is secured to the roof panel 422 through a dam 504, and a molding 508 is fixed between the roof panel 422 and the front windshield glass 154 through a stopper 506, as is known. The pick-up 500 has a similar structure to that in the first embodiment, and includes a casing 510, a loop coil 512 and circuitry 514. The loop coil 512 of the pick-up 500 is secured within a distance of 6.0 cm from the peripheral edge of the header inner panel 502, thereby positively detecting the surface currents which are concentrated with high density on the header inner panel 502. Referring next to Figs. 18 to 20, which shows a sixth embodiment of the present invention, a pick-up is attached to a hinge of the trunk lid. The structure shown in Figs. 18 to 20 is also shown in Figs. 2, 1 and 3 of our EP-A-187446. In Fig. 18, a trunk hinge 600 with one end thereof rotatably supported by the vehicle body and the other end secured to the trunk lid 602 rotatably supports the trunk lid 602. A pick-up 604 is disposed on the trunk hinge 600. A torsion bar 606 is provided on the end of the trunk hinge 600 which is rotatably supported by the vehicle body, so as to control the degree of opening of the trunk lid 602. As is known, a water sealing weather strip rubber 608 is provided between the trunk lid 602 and the vehicle body, thereby preventing the ingress of rainwater from a rear window glass 610. The pick-up 604 is longitudinally fixed on the outer surface of the trunk hinge 600, namely, on the side facing the trunk void, in such a manner that the longitudinal side of a loop coil 612 provided within the pick-up 604 is disposed in parallel to the longitudinal side of the trunk hinge 600. In this way, the loop coil 612 can positively catch the surface currents flowing on the trunk hinge 600 with high efficiency. The pick-up 604 includes a casing 614 and circuitry 616, as is the case with the first embodiment, and the opening side of the casing 614 is opposed to the trunk hinge 600. Brackets 618 and 620 are secured to both open end portions of the casing 614, and one end of each of the brackets 618 and 620 is firmly screwed to the trunk hinge 600. Therefore, it will be understood that the magnetic flux which is induced by the high-frequency surface currents flowing on the trunk hinge 600 is introduced into the casing 614, and the pick-up is shielded from external magnetic flux by the casing 614. The loop coil 612 is preferably provided along the trunk hinge 600 and is formed in conformity with the curvature of the trunk hinge 600. Power source and a signal for controlling the circuit are supplied to the circuitry 616 from a cable 622, as described above, and the high-frequency detection signal acquired by the loop coil 612 is fed out by a coaxial cable 624, and is processed by a similar circuit to that in the first embodiment. As described above, according to this embodiment, surface currents are detected from the trunk hinge which are unrelated to the detection of the surface currents in the prior art. In this manner, secure reception of the electric waves from the transmitter is enabled without any external exposure of the antenna of the keyless vehicle entry apparatus. Fig. 20 shows another example of arrangement for attaching a pick-up to the trunk hinge. The same numerals are provided for those elements which are the same as those in Fig. 19, and explanation thereof will be omitted. In this example, a pick-up 700 is attached to the back of the trunk hinge 600. A casing 702 accommodates a loop coil 704 and circuitry 706, and is firmly secured to the back of the trunk hinge 600 by brackets 708 and 710. In this example, the pick-up 700 does not protrude from the trunk hinge 600 into the trunk void, whereby it is prevented from coming into contact with or damage the baggage or the like placed within the trunk void. Fig. 21 shows a seventh embodiment of a keyless vehicle entry apparatus according to the present invention. Pick-ups 102a and 102b have a similar structure to the above-described probe and are provided on front pillars 100a and 100b, respectively, on both sides of the vehicle body to detect the surface currents which flow concentratedly on the front pillars. Thus, accordint to the seventh embodiment, the two pick-ups which are disposed on the respective sides of the vehicle body compensate for each other, thereby enjoying good receiving sensitivity. In Fig. 21, the same numerals are provided for those elements which are the same as those in the first embodiment, and explanation thereof will be omitted. High-frequency surface currents are induced on the vehicle body by the electric waves from the transmitter 104, the pick-ups 102a and 102b receive a signal transmitted from the surface currents. The received signal from the pick-up 102a is fed, as it is, into a mixer 123, while the received signal from the pick-up 102b is fed into the mixer 123 after the phase thereof is corrected by a phase difference correction circuit 122. The received signals are mixed by the mixer 123, and thereafter the mixed signal is supplied to the RF amplifier 124 where it is subjected to a desired amplifying operation. Fig. 22 shows the directional patterns of the antenna in the keyless vehicle entry apparatus in accordance with this embodiment in the frequency band of 60 MHz. In Fig. 22 (A), the solid line shows the directional pattern of the pick-up 102a and the broken line that of the pick-up 102b, and Fig. 22 (B) shows the characteristic curve of both pick-ups as a result of synthesizing the directivities thereof. As is clear from Fig. 22 (A), the pick-up 102a exhibits good sensitivy on the right-hand side of the vehicle body, and slightly lowered sensitivity in the forward and backward directions of the vehicle body. In contrast, the pick-up 102b has a directivity completely contrary to that of the pick-up 102a, and it is to be understood that both pick-ups compensate for each other with respect to sensitivity. Accordingly, synthesis of the directional characteristics of both pick-ups 102 produces an approximately non-directional antenna, thereby enabling a good keyless entry operation from both sides of the vehicle body. Fig. 23 shows the directional patterns of the antenna in another embodiment of a keyless vehicle entry apparatus according to the present invention. Pick-ups are disposed on both rear corners of the roof of a vehicle body. As is clear from Fig. 23, both pick-ups 406a and 406b compensate for each other's lowered sensitivity, and improve the directional characteristic of the antenna in the keyless vehicle entry apparatus, as in the seventh embodiment shown in Fig. 21. Fig. 24 shows the directional patterns of the antenna in still another embodiment of a keyless vehicle entry apparatus according to the present invention. Pick-ups are disposed at the central portion of the front end of the roof and at the central portion of the rear end of the roof, respectively. As is obvious from Fig. 24, the pick-up 406 disposed at the central portion of the rear end of the roof has a good directional characteristic in the forward direction of the vehicle body, while the pick-up 500 disposed at the central portion of the front end of the roof has a good directional characteristic in the backward direction of the vehicle body. Thus, both pick-ups compensate for each other's lowered sensitivity, thereby constituting an antenna system producing a good directional characteristic. Fig. 25 shows the directional patterns of the antenna in a further embodiment of a keyless vehicle entry apparatus according to the present invention. Pick-ups are provided on a front pillar and at the central portion of the rear end of the roof. As is clear from Fig. 25, the pick-up 102b disposed on the front pillar exhibits a good directional characteristic on the right-hand and left-hand sides of the vehicle body, while the pick-up 406 disposed at the central portion of the rear end of the roof exhibits a good directional characteristic in the backward and forward directions of the vehicle body. Thus, both pick-ups can compensate for each other with respect to the directivity. Fig. 26 shows the directional patterns of the antenna in a still further embodiment of a keyless vehicle entry apparatus according to the present invention. Pick-ups are provided on the right-hand front pillar and on the rear right-hand corner of the roof, respectively. As is clear from Fig. 26, the directivities of the pick-up 102b disposed on the right-hand front pillar and the pick-up 406b disposed on the rear right-hand corner of the roof compensate for each other, thereby constituting an antenna system having a good directional characteristic. Fig. 27 shows the directional patterns of the antenna in a still further embodiment of a keyless vehicle entry apparatus according to the present invention. Pick-ups are provided on the front right-hand corner of the roof and the right-hand trunk hinge of the vehicle body, respectively. As is shown in Fig. 27, the pick-up 500a provided on the front right-hand corner of the roof and the pick-up 604 provided on the right-hand trunk hinge compensate for each other with respective to the directivity, thereby constituting an antenna system of a keyless vehicle entry apparatus having a good directional characteristic. Although two pick-ups are provided on the vehicle body in these embodiments, the number of pick-ups is not limited to two, and provision of three or more pick-ups is preferable. The locations of the pick-ups are not limited to those in the above-described embodiments and may be any positions where it is possible to detect the high-frequency surface currents induced on the vehicle body by the electric waves from the transmitter. As described above it is possible to provide a keyless vehicle entry apparatus including pick-ups exclusively for use by the apparatus without impairing the aesthetically pleasing external appearance of the vehicle, to prevent the radio broadcast receiving sensitivity from deteriorating due to division of a received signal from the radio broadcasting reception antenna into two, and, in addition, to reduce the influence of jamming waves by limiting the reception band of a pick-up to a narrow band.

Claims: 1. A keyless vehicle entry apparatus comprising a portable transmitter (104) operable to transmit a coded signal at a predetermined radio frequency, and receiving equipment (102,106) adapted to be carried by a vehicle; said receiving equipment comprising: an antenna system (102) to receive said transmitted signal, signal processing means (106) to decode the received signal, and means to generate a control signal for causing locking or unlocking of a vehicle entry in response to a decoded received signal having a predetermined characteristic; characterized in that: said antenna system comprises a pick-up (102; 212; 312; 406; 500; 604; 102a, b) mounted adjacent a sheet metal member (150; 200; 300; 402; 502; 600) forming a portion of the vehicle body to detect radio frequency surface currents induced in said sheet metal member by transmitted radio frequency signals and which have a concentrated flow along a marginal edge portion of said sheet metal member; said pick-up comprising a casing (162; 214; 316; 408; 510; 614) formed of electrically conductive material and having an elongate opening, and an elongate loop antenna (164; 216; 314; 410; 512; 612) disposed within said casing with a longer side thereof exposed through said opening; mounting means (166; 220; 324; 418; 502a; 618) mounting said casing to said vehicle body portion so that said exposed longer side of said loop antenna extends lengthwise of and closely adjacent said marginal edge portion; and said pick-up being adapted to receive only signals in a narrow frequency band including the predetermined transmission frequency. 2. Apparatus according to claim 1 characterized in that said pick-up (102) is mounted within a hollow front pillar (100) of the vehicle body with the exposed side of its loop antenna (164) extending longitudinally of the length of the pillar. 3. Apparatus according to claim 1 characterized in that said pick-up (212) is mounted with the exposed side of its loop antenna (216) extending longitudinally of the rearward marginal edge portion of an engine hood (200) of the vehicle. 4. Apparatus according to claim 1 characterized in that said pick-up (312) is mounted with the exposed side of its loop antenna (314) extending longitudinally of the forward marginal edge portion of a trunk lid (300) of the vehicle. 5. Apparatus according to claim 1 characterized in that said pick-up (406; 500) is mounted with the exposed side of its loop antenna (410; 512) extending longitudinally of the rear or the front marginal edge portion of a roof panel (402; 502) of the vehicle. 6. Apparatus according to claim 1 characterized in that at least first and second said pick-ups are provided at different positions on the vehicle. 7. Apparatus according to claim 6 characterized in that said first and second pick-ups (102a, 102b) are each mounted within a hollow front pillar (100a, 100b) of the vehicle body with the exposed side of their loop antenna (164) extending longitudinally of the length of the pillar, the first pick-up (102a) at the left side and the second pick-up (102b) at the right side of the vehicle. 8. Apparatus according to claim 6 characterized in that said first and second pick-ups (406a, 406b; 406, 500) are both mounted with the exposed side of their loop antenna (410; 512) extending longitudinally of a marginal edge portion of a roof panel (402; 502) of the vehicle. 9. Apparatus according to claim 6 characterized in that said first pick-up (102b) is mounted within a hollow front pillar (100) of the vehicle body with the exposed side of its loop antenna (164) extending longitudinally of the length of the pillar, and said second pick-up (406) is mounted with the exposed side of its loop antenna (410) extending longitudinally of the rear marginal edge portion of a roof panel (402) of the vehicle substantially centrally of the length of said rear marginal edge portion. 10. Apparatus according to claim 6 characterized in that said first pick-up (500a) is mounted with the exposed side of its loop antenna (512) extending longitudinally of the forward marginal edge portion of a roof panel (502) of the vehicle substantially at one end of the length of said forward marginal edge portion, and said second pick-up (604) is mounted with the exposed side of its loop antenna (612) extending longitudinally of the length of a hinge (600) of a trunk of the vehicle, said first and second pick-ups being on the same side of the vehicle.

Inventors: KONDO, HIROSHI, OHE, JUNZO
Applicants: TOYOTA JIDOSHA KABUSHIKI KAISHA
Application year: 1986
Main classification: B60R25
IPC codes: G07C9, H01Q1