JP2006205936A - Engine starting control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine starting control system capable of certainly protecting a power source regardless of the level of a short current when short-circuit is generated in an immobilization amplifier. <P>SOLUTION: In the immobilization amplifier 52, a power source voltage is fed from a power source circuit 50. It is detected based on a voltage level on a power source feeding line relative to the immobilization amplifier 52 by a short-circuit detection part 54 whether or not an output to the immobilization amplifier 52 side of the power source circuit 50 generates short-circuit. Further, when the short-circuit detection part 54 detects the short-circuit state for a constant time or longer, a power source restriction means for restricting the power source output from the power source circuit 50 to the immobilization amplifier 52 is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an engine start control system.

Japanese Patent Laid-Open No. 8-133016

  In recent years, in order to prevent theft of automobiles, an authentication ID is stored in a key or a wireless communication portable device carried by a user of the automobile, and the engine ID is based on the result of checking the ID with the master ID on the vehicle side. There is known an engine start system (so-called immobilizer (commonly referred to as “immobilizer”)) that permits start (for example, Patent Document 1).

  In the engine start system as described above, when the ID authentication is rejected, the engine control unit enters a start prohibition setting state (immobility set state) and refuses to start the engine by an unauthorized person. The start prohibition control command is executed by an immobilizer control unit different from the engine control unit, and the engine control unit refers to a start prohibition setting / cancellation signal from the immobilizer control unit to control engine start. To do.

  The immobilizer control unit may be connected to peripheral circuit elements that are expected to consume a certain amount of power, such as a transponder reader for user ID authentication. Such peripheral circuit elements are driven via an immobilizer amplifier connected to a dedicated power supply circuit.

  There is a problem of circuit destruction due to overcurrent at the time of short circuit as usual in a circuit element having a large load. Specifically, if the immobilizer amplifier is shorted to ground for some reason, the power supply circuit may be destroyed due to heat generated by overcurrent. Conventionally, the short-circuit current on the load side is detected in the form of a voltage drop with a shunt resistor. If the detected short-circuit current becomes larger than a certain level, a short-circuit protection circuit with a forced power-off function using a transistor switch or the like is used. The method of stopping the power output by hardware has been taken.

  However, with the above method, if the detected short-circuit current does not increase beyond a certain level, the forced power-off function will not operate, and ultimately it is up to the circuit constants of the short protection circuit to prevent circuit destruction. There is a fault that becomes. Therefore, even if the short-circuit condition is certain, if the short-circuit current is slightly smaller than the threshold current value determined from the circuit constant, the short-circuit protection circuit will no longer work, and the immobilizer amplifier will continue to operate in that state. This leads to heat generation or destruction of the power circuit.

  An object of the present invention is to provide an engine start control system capable of reliably protecting a power supply regardless of the level of a short-circuit current when a short circuit occurs in an immobil amplifier.

Means for Solving the Problems and Effects of the Invention

In order to solve the above problems, an engine start control system of the present invention includes:
An ID acquisition function for acquiring the user ID stored in the security key possessed by the user, and authenticating the acquired user ID. If the authentication result is acceptance authentication, the content indicates engine start permission. An immobilizer control unit having an engine start prohibition signal output function for outputting an engine start prohibition signal, which is a content indicating engine start prohibition when there is,
An immobilizer peripheral circuit element that is connected to the immobilizer controller and performs electrical operations related to basic functions in a state where the load is larger than the control signal input / output processing by the immobilizer controller;
An immobilizer amplifier that drives immobilizer peripheral circuit elements;
A power supply circuit for supplying a power supply voltage to the immobilizer amplifier;
A short detection unit that detects whether the output to the immobilizer side of the power circuit is short-circuited based on the voltage level on the power supply line to the immobilizer amplifier;
And a power limiting unit that limits power output from the power supply circuit to the immobilizer amplifier when the short detection unit detects a short state for a predetermined time or more.

  According to the above configuration, since the short circuit of the immobilizer amplifier is detected based on the voltage level on the power supply line with respect to the immobilizer amplifier, it is possible to reliably detect the occurrence of the short circuit regardless of the short current. And, when the short-circuit state is continuously detected, the power output from the power supply circuit to the immobilizer amplifier is limited. The power supply can be surely protected regardless of the generation level of the short current.

  In order to simplify the hardware configuration of the engine start control system (immobilizer system) as a whole and to reduce the weight of the entire system, it is effective to implement the power supply limiting means as software on the immobilizer control unit. . In this case, the power supply circuit is configured so that the power supply output operation to the immobilizer amplifier is controlled based on the power supply operation command input from the immobilizer control unit, and the power supply limiting unit is realized by the function on the immobilizer control unit. It can be configured to limit the power output from the power supply circuit to the immobilizer amplifier by receiving the short detection input from the short detection unit and restricting the output of the power supply operation command to the power supply circuit by software processing. it can.

  In the above configuration, the power limiting unit is configured to input a power operation command signal from the immobilizer control unit to the power circuit, and when the input duration of the short detection from the short detection unit exceeds a predetermined reference time. The input of the power supply operation command signal from the immobilizer control unit to the power supply circuit can be cut off. When the battery voltage temporarily decreases to such an extent that it falls outside the input specification range of the power supply circuit depending on the operation state of the automobile, the short detection unit may instantaneously detect a short circuit. Therefore, if configured as described above, the input of the power supply operation command signal from the immobilizer control unit to the power supply circuit is not interrupted in the short-circuit detection when such erroneous detection occurs, and the immobilizer amplifier The problem of stopping can be effectively avoided.

  Next, in the engine start control system of the present invention, a transponder having a user ID stored in a security key can be provided. By providing a security key fixed mounting portion in the automobile and providing a transponder reader here, the user ID can be reliably read by mounting the security key to the fixed mounting portion. In this case, the immobilizer peripheral circuit element includes a high-frequency radio wave generation source (included in the reader) that generates an excitation high-frequency radio wave for driving and exciting the transponder, and the immobil amplifier includes the high-frequency radio wave. It can be for driving the source. Since the immobilizer amplifier is used to drive a high-frequency radio wave generation source that is indispensable for ID authentication by the transponder, if a short circuit abnormality occurs, ID authentication becomes impossible and engine startup becomes impossible. Therefore, the protection of the power supply circuit according to the present invention is beneficial from the viewpoint of securing the engine start function of the automobile.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram schematically showing an electric system of an automobile equipped with an engine start control system of the present invention. The engine start control system 1 authenticates the ID acquisition function for acquiring the user ID stored in the security key 2 possessed by the user and the acquired user ID, and starts the engine if the authentication result is acceptance authentication. The immobilizer control unit 5 having an engine start prohibition signal output function that outputs an engine start prohibition signal (5) that indicates contents indicating permission and that indicates engine start prohibition when rejection authentication is required. Configured as part.

  The immobilizer control unit 5 is connected to immobilizer peripheral circuit elements that perform electrical operations related to basic functions in a state where the load is larger than the control signal input / output processing by the immobilizer controller 5. In the present embodiment, as shown in FIG. 3, a main circuit 53 incorporated in a reader 112 of a transponder 127 described later corresponds to this, and this main circuit (imobi peripheral circuit element) 53 is driven by an immobilizer amplifier 52. .

  The immobilizer amplifier 52 is supplied with a power supply voltage from the power supply circuit 50. Whether the output of the power supply circuit 50 to the immobilizer amplifier 52 is short-circuited is detected by the short detection unit 54 based on the voltage level on the power supply line for the immobilizer amplifier 52. A power limiting unit is provided for limiting the power output from the power circuit 50 to the immobilizer amplifier 52 when the short detection unit 54 detects a short state for a predetermined time or longer.

  Since the short circuit of the immobilizer amplifier 52 is detected based on the voltage level on the power supply line with respect to the immobilizer amplifier 52, the presence or absence of the short circuit can be reliably detected regardless of the short circuit current. Since the power output from the power supply circuit 50 to the immobilizer amplifier 52 is limited when the short-circuit state is continuously detected, it is difficult for erroneous detection of a short circuit due to noise or the like to occur. The power supply can be surely protected regardless of the circuit constants and the occurrence level of the short current.

This will be described in more detail below.
The engine start control system 1 includes a wireless communication portable device (smart key (security key)) 2 that can be freely carried by a driver (user), and a controller 4 mounted on an automobile 3. The controller 4 includes an immobilizer control unit 5, a transmission / reception unit 6 (FIG. 3: a transmission / reception circuit 6C and a modulation / demodulation circuit 6M), and a transponder reader 112. ID authentication can be performed either by the wireless communication function of the portable device 2 or by direct reading from the transponder 127 (FIG. 3). In the former case, the immobilizer control unit 5 intermittently outputs a request signal from the transmission / reception unit 6 to the outside of the vehicle. When the wireless communication portable device 2 enters a predetermined area in the vehicle and receives a request signal, the wireless communication portable device 2 automatically wirelessly transmits the user ID of the wireless communication portable device 2 to the automobile 3 side.

  The structure of the transponder 127 is well known. For example, the transponder 127 is composed of a semiconductor in which a memory or the like is made into a sinkel chip and an antenna. It has a function to do. On the automobile side, a holder serving as a holding portion of the portable device 2 is disposed at a fixed position in the vehicle, and the reader 112 of the transponder 127 is disposed in this holder. As shown in FIG. 3, the reader 112 includes an immobilizer amplifier 52, a main circuit 53 and a modulation / demodulation circuit 56 that are driven by the immobilizer amplifier 52. As shown in FIG. 4, the main circuit 53 includes a high-frequency radio wave generation source (RF circuit) 129 and a transmission / reception coil 116. The RF circuit 129 drives the transmission / reception coil 116 at a high frequency to excite the transmission / reception coil of the transponder 127, frequency-modulates the user ID sent from the immobilizer control unit 5, and sends the user ID from the transmission / reception coil 116 to the transponder 127. Further, the user ID from the transponder 127 received by the transmitting / receiving coil 116 is demodulated and sent to the immobilizer control unit 5.

  Returning to FIG. 1, the automobile 3 is provided with an engine control unit 14. The engine control unit 14 is electrically connected to the power supply control unit 13. The engine control unit 14 controls fuel injection and engine ignition of the engine 16.

  A steering lock device 9 is mounted on the automobile 3. The steering lock device 9 includes the lock control unit 10 described above, a steering lock motor 11 as an actuator, and a steering lock 12. FIG. 2 is a schematic configuration diagram of the steering lock device 9. A worm gear 22 is attached to the output shaft of the steering lock motor 11, and the worm gear 22 is connected to a gear portion 25 of a lock pin (lock bar) 24 as a locking means via a spur gear 23. When the steering lock motor 11 is driven, the lock pin 24 moves in the direction of the arrow A shown in FIG. 2, and with this movement, the tip portion can be engaged with and disengaged from the concave portion 27 of the steering shaft 26. .

  When the steering lock motor 11 rotates forward, for example, and the lock pin 24 is inserted into the recess 27 of the steering shaft 26, the steering lock 12 is locked and the rotation of the steering shaft 26 is restricted. On the other hand, when the steering lock motor 11 rotates in the reverse direction and the lock pin 24 comes out of the recess 27, the steering lock 12 is unlocked and the steering shaft can be rotated.

  The steering lock device 9 includes a lock detection switch 33 and an unlock detection switch 34. These switches 33 and 34 are mechanical switches (limit switches in this example). The lock detection switch 33 detects the lock of the steering lock 12, and the unlock detection switch 34 detects the unlock of the steering lock 12. When the steering lock 12 is locked, the lock detection switch 33 is turned on when the contact portion 35 on the side of the lock pin 24 comes into contact, and outputs an on signal to the lock control unit 10. On the other hand, when the steering lock 12 is unlocked, the unlock detection switch 34 comes into contact with the contact portion 36 at the base end of the lock pin 24 and is turned on.

  As shown in FIG. 2, the lock / unlock identification signal is input to the lock control unit in the form of a level signal in which unlock is activated and lock is deactivated, for example. In this embodiment, the switch outputs of the unlock detection switch 34 and the lock detection switch 33 are both active (eg, high level) when turned on and inactive (eg, low level (grounded)) when turned off, and are reset. The output of the unlock detection switch 34 is input to the set terminal of the latch circuit 32, and the output of the lock detection switch 33 is input to the reset terminal so that the identification signal is locked by the control signal, and the output of the latch circuit 32 is locked and unlocked. It is used as an identification signal for the lock. Thus, the unlocking is not recognized until the lock pin 24 is completely detached from the steering shaft 26 and the unlock detection switch 34 is energized.

  The immobilizer control unit 5, the lock control unit 10, the power supply control unit 13, and the engine control unit 14 are all known computer hardware (ECU) in which a CPU, a ROM, a RAM, and an input / output unit (I / O port) are bus-connected. ) And are connected to each other via a network. FIG. 3 is a block diagram showing the immobility control unit 5 in more detail, and includes a computer in which a CPU 5A, a ROM 5B, a RAM 5C, and an input / output unit (I / O port) 5D are connected by a bus. In addition, an EEPROM 5F as a nonvolatile memory is connected to the bus. The EEPROM 5F is formed with a verification memory in which a master ID for authentication verification is written and a diagnostic memory described later (the latter constitutes a diagnostic storage means in the present invention). In the EEPROM 5F, the driving voltage at the time of reading is different from the driving voltage at the time of writing and erasing, and the latter (for example, 9V) is set higher than the former (for example, 5V). Reference numeral 5E denotes an EEPROM control power supply including a booster circuit for writing / erasing data to / from the EEPROM 5F. When the ECU configuring the immobilizer control unit 5 receives a reset signal RST from the unit, the contents of the RAM 5C are reset, and the output of each signal port of the input / output unit 5D is also initialized.

Each part of the hardware in FIG. 1 constitutes the following means by software (the signal part is indicated by a reference numeral in parentheses).
User ID authentication means (immobilizer control unit 5): authenticates a user ID stored in a security key (wireless communication portable device 2) possessed by the user.
Specific vehicle operation unit control means (lock control unit 10): The specific vehicle operation unit, which is indispensable for the user to drive the automobile, is switched between an operable state and an inoperable state.
Specific vehicle operation section control command means (power supply control section 13): When the verification result signal (2) by the user ID authentication means is acceptance authentication, the specific vehicle operation section control means can operate the specific vehicle operation section. Command to enter state.
Engine operation prohibition signal output means (immobilizer control unit 5): An engine operation prohibition signal (switchable between a prohibition setting output state for prohibiting the engine operation of the automobile and a prohibition release output state for permitting the engine operation) 5) is output.
Engine control command means (immobilizer control unit 5): After the specific vehicle operation unit shifts to the operable state (recognized by the unlock completion signal (4)), the engine operation prohibition signal (5) is in the prohibition release output state. Switch to.
Engine start control means (engine control unit 14): When the engine operation prohibition signal (5) is in the prohibition release output state, the engine 16 is started and the engine operation prohibition signal is in the prohibition setting output state. In such a case, starting of the engine 16 is prohibited.
The function realization program for each means is stored in the ROM of each control unit 5, 10, 13, 14.

  The immobilizer control unit 5 receives the user ID from the wireless communication portable device 2 via the transmission / reception unit 6, and writes the user ID and the master ID registered in advance in the automobile 3 (in the collation memory of the EEPROM 5F). ). Then, the immobility control unit 5 unlocks the door lock 8 if the two IDs match. On the other hand, the immobilizer control unit 5 locks the door lock 8 when the door lock 8 is unlocked and no user ID is received from the wireless communication portable device 2. Therefore, the door lock 8 is automatically unlocked when the driver approaches the automobile 3, and the door lock 8 is automatically locked when the driver leaves the automobile 3. Note that the master ID may be updated at any time by a random number calculation or the like every time authentication processing is performed, and the user ID on the wireless communication portable device 2 side is also rewritten by wireless communication with the transmission / reception unit 6. Thereby, security can be further improved.

  In FIG. 1, the basic operation of the immobilizer in the engine start control system 1 is as follows. First, the automobile 3 is provided with a one-push engine starting system that can start and stop the engine 16 by operating a push button switch. The automobile 3 is provided with a one-push operation switch (engine starting switch) 21. It is installed. The engine start switch 21 may be provided in the wireless communication portable device 2. When the engine start switch 21 is pressed, a start trigger is sent to the power supply control unit 13, and in response to this, the power supply control unit 13 transmits an engine start request signal (1) to the immobility control unit 5.

  The immobility control unit 5 receives the engine start request signal (1), collates the user ID of the wireless communication portable device 2 with the master ID registered in the automobile 3, and when the collation coincides (that is, authentication acceptance), The verification result signal (2) is output to the power supply control unit 13. Further, the immobility control unit 5 transmits an unlock request signal (3) to the lock control unit 10. Upon receiving the lock release request signal (3), the lock control unit 10 drives the steering lock motor 11 to unlock the steering lock 12. When the unlocking of the steering lock 12 is completed, an unlock completion signal is transmitted to the immobility control unit 5 and the power supply control unit 13. Also, the power supply control unit 13 receives the verification result signal (2) of the authentication acceptance and activates the ignition (6).

  Immobilizer control unit 5 receives unlock completion signal (4)), immobilizer set (engine operation prohibition signal: active immobilizer set (prohibition release output state), inactive means immobilizer set (prohibition setting output state) ). On the other hand, the power supply control unit 13 also receives the unlock completion signal (4) and transmits a starter start request signal (7).

  The engine control unit 14 monitors the state of the engine operation prohibition signal in the initial state, and is in a standby state until the immobility set (inhibition release output state). When the immobilizer is set, the starter start request signal (7) is read. If it is active, it is determined that the start condition is satisfied and the engine is started.

  In recent years, as described above, a portable device 2 that wirelessly transmits a user ID to the immobilizer control unit 5 has been used as the security key 2. However, in the case of ID authentication using the portable device 2, there is a problem that authentication becomes impossible when the portable device 2 runs out of battery. In particular, when the portable device 2 is configured as a rechargeable mobile phone, the secondary battery mounted as a power source is mostly used for functions other than ID authentication, such as calls, emails, Internet communications, and games. Is more likely to cause trouble due to battery consumption. Specifically, it is possible to exemplify a situation where it is impossible to laugh, such as when the mobile device 2 is enthusiastic about chatting and playing and when returning to the car, the mobile device 2 runs out of battery and the engine does not start.

  However, if it is configured as shown in FIG. 3, in the ID authentication that is the first step of the process, when the portable device 2 runs out of battery and the ID authentication by wireless communication via the transmission / reception unit 6 fails, The user ID is read from the transponder 127 in the portable device 2 and authentication is retried. That is, if the transponder 127 mounted on the portable device 2 is used as a non-power backup authentication transmitting means for ID authentication by wireless transmission, even if the portable device 2 runs out of battery, the mounted transponder 127 is installed. Is supplied with operating power by receiving radio waves from the reader 112 side, and the stored ID can be returned to the reader 112 with no power supply, so that it is possible to avoid a situation where the engine cannot be started. .

  At this time, the immobilizer amplifier 52 is used to drive the high-frequency radio wave generation source 129 that is indispensable for ID authentication by the transponder 127. Therefore, if a short circuit abnormality occurs and the power supply circuit 50 is damaged, the transponder that is the last fort. ID authentication by 127 is also impossible, and literally goes up. Therefore, providing the power limiting means and protecting the power supply circuit 50 as in the present invention is beneficial from the viewpoint of securing the engine start function of the automobile. Hereinafter, a method for specifically protecting the power supply circuit 50 in the present invention will be described in more detail.

  The power limiting means can be configured separately from the immobilizer control unit 5, for example, a control hardware logic having a timer counter, a transistor switch on a power supply line controlled by the control hardware logic, It can be configured as a combination. However, in order to simplify the hardware configuration of the engine start control system (immobilizer system) as a whole and to reduce the weight of the entire system, the power supply limiting means can be realized by software on the immobilizer control unit 5. It is valid.

  In the present embodiment, as shown in FIG. 6, the power supply circuit 50 controls the power output operation to the immobilizer amplifier 52 based on the power supply operation command input (A) from the immobilizer control unit 5. The function is realized on the control unit 5, and by receiving the short detection input (C) from the short detection unit 54, the output of the power supply operation command to the power supply circuit 50 is regulated by software processing. The power output from the circuit 50 to the immobilizer amplifier 52 is limited.

  As shown in FIG. 3, in this embodiment, the short detection unit 54 is configured with a group of voltage dividing resistors 54 a and 54 b provided on a path branching from the power supply line to the immobilizer amplifier 52 to the ground as a main part. The divided voltage at the connection point of both resistors 54a and 54b is input to the input / output unit 5D of the ECU constituting the immobilizer control unit 5 as short-circuit detection information (the resistor 54c is for adjusting the input impedance to the ECU). When the immobil amplifier 52 is not short-circuited to the ground and exhibits a normal load impedance, the divided voltage is also in a high level (Hi) state corresponding to the power supply voltage. However, when the immobil amplifier 52 is shorted to ground, the load impedance is lowered, and the divided voltage is in a low level (Lo) state. Therefore, the immobility control unit 5 can use the divided voltage as binary short-circuit detection information.

  As conceptually shown in the timing chart of FIG. 8, in the present embodiment, the power supply limiting means receives the power supply operation command signal (A) from the immobilizer control unit 5 to the power supply circuit 50, and outputs from the short detection unit 54. When the input duration of the short detection exceeds a predetermined reference time T1, the input of the power supply operation command signal (A) from the immobilizer control unit 5 to the power supply circuit 50 is cut off. When the battery voltage temporarily decreases to such an extent that the battery voltage falls outside the input specification range of the power supply circuit 50 depending on the operation state of the automobile, the short detection unit 54 may instantaneously detect a short circuit. Therefore, with the above-described configuration, the input of the power supply operation command signal (A) from the immobilizer control unit to the power supply circuit 50 is cut off in a short-time short detection when such a false detection occurs. Therefore, the trouble that the immobilizer amplifier 52 stops can be effectively avoided.

  Further, in the above configuration, when the short detection unit 54 detects a short circuit of the output load of the power supply circuit 50, a diagnosis storage unit is provided for storing the detection history as an immobilizer amplifier abnormality. In the system in which the output of the power supply operation command to the power supply circuit 50 is regulated by software processing, if a short circuit abnormality of the immobilizer amplifier 52 occurs, it can be easily stored as a diagnosis, which can be useful for maintenance such as failure investigation. it can. As shown in FIG. 3, in the present embodiment, a diagnostic memory area formed in the EEPROM 5F constitutes the diagnostic storage means.

  An example of software processing on the immobility control unit 5 for realizing the above processing is shown in the flowchart of FIG. This process is repeatedly executed at a cycle T0 shorter than the above-described reference time T1 for determining a short circuit. First, in S1, the input port of the short detection signal (C) from the short detection unit 54 is read. If it is Lo (ie, short) in S2, the process proceeds to S3, and a separately prepared timer program is started. Check whether it is. If activated, the process proceeds to S4, and the output port of the power supply operation command signal (A) is read. If it is Hi (that is, the power supply to the immobilizer amplifier 52 is instructed) in S5, S6 is performed. Go to and read the timer value. If this timer value is equal to or greater than T1, it is determined that the short circuit has occurred, and the power supply operation command signal (A) is switched to Lo in S8 to stop the power supply to the immobilizer amplifier 52. In S9, the fact that an abnormality has occurred in the immobilizer amplifier is stored in the EEPROM 5F together with the abnormality occurrence time, and the processing cycle ends.

  If the short detection input is Hi in S2 (that is, if no short has occurred), the process proceeds to S10 to reset the timer and end the processing cycle. Also, when the power operation command signal (A) is Lo in S5 (that is, when power supply to the immobilizer amplifier 52 is not commanded), the process proceeds to S10 to reset the timer and end the processing cycle. If the timer is not started in S3, the process proceeds to S11 to start the timer and end the processing cycle. If the timer value is not equal to or greater than T1 in S7, S8 and S9 are skipped and the processing cycle is terminated. In this case, since the timer continues counting without being reset, the short condition is satisfied (that is, the short detection signal (C) is Lo and the power operation command signal (A) is Hi). Thus, when the timer value becomes equal to or greater than T1 in S7 of the subsequent processing cycle, the short protection processing in S8 and the diagnosis storage processing in S9 are performed.

  Next, FIG. 5 is a circuit diagram showing a configuration example of the power supply circuit 50. In the present embodiment, the power supply circuit 50 is provided with current limiting circuits 64 and 65 that limit the output current when the output to the immobil amplifier 52 side is short-circuited. In the method of the present invention, the determination of the occurrence of a short circuit requires that the short circuit detection state last for a certain time (T1) or longer, and therefore, after the short circuit of the immobil amplifier 52 occurs, the power supply operation limiting process is completed. During this time, a large amount of current flows for a short time, and there is no change in the situation where the power supply circuit 50 is burdened. Therefore, by providing the current limiter as described above in the power supply circuit 50, it is possible to effectively protect the power supply even in a process transition period such as the determination waiting time.

  The power supply circuit 50 includes a constant voltage circuit 61, driving transistors 62f (and 62t) and 63t for switching the input voltage from the constant voltage circuit 61 using the power supply operation command signal (A) from the immobilizer control unit 5 as a drive input. The current limiting circuits 64 and 65 are configured to include a current limiting transistor that limits the output current of the driving transistor. In this way, the current limiting function can be realized by a simple analog circuit. The current limiting circuits 64 and 65 are configured such that current limiting transistors 65t and 64t are provided on branch paths 65j and 64j that branch from the input path (the gate is the former and the latter is the base) of the driving transistors 62f and 63t to the ground side. It consists of

  Since the transistor has a substantially constant voltage drop in the forward direction of the pn junction (about 0.6 V in the case of a silicon transistor), the current limiting transistors 65t and 64t are formed of bipolar transistors as in this embodiment. In this case, the pn junction drop voltage between the base and the emitter (in the case of the current limiting transistor 65t) or between the collector and the base (in the case of the current limiting transistor 64t) is used as the reference voltage. On the other hand, the current to be limited is voltage-converted by the detection resistors 65a and 65b and the detection resistor 64a (this becomes a current detection signal), and this is input to the input terminals (bases) of the current limiting transistors 65t and 64t. The When the voltage-converted current detection signal exceeds the reference voltage, the current limiting transistors 65t and 64t are turned on, and the input current of the driving transistors 62f (and 62t) and 63t is supplied from the branch paths 65j and 64j to the current limiting transistor 65t. , 64t and then leaks to the ground side, resulting in a current limiting effect. In this case, the current limit to be limited is determined in terms of circuit constants by the reference voltage and the resistance values of the detection resistors 65a, 65b, and 64a.

  For the purposes of the present invention, the current limiting function assumes that the immobilizer amplifier 52 is short-circuited, and a current that greatly exceeds the rating of the immobilizer amplifier 52 during normal operation (that is, when not short-circuited) flows. In consideration of this, in the present embodiment, driving transistors for power supply output are provided in a plurality of stages (62f (and 62t), 63t), and the current limiting transistors are also provided in a plurality of stages (65t, 64t). The power supply protection effect is enhanced by providing the structure.

  Specifically, the driving transistor has a first driving transistor 62f that is directly driven by the input of the power supply operation command signal (A) and a part of the output of the first driving transistor 62f as a driving input. It is configured to include a second driving transistor 63t that operates in a utilized form and controls the output current I to the immobilizer amplifier 52. The current limiting circuits 64 and 65 include a first current limiting transistor 65t that limits the input current of the power supply operation command signal (A) to the first driving transistor 62f, and a second driving transistor 63t. And a second current limiting transistor 64t that limits the input current of the power supply side terminal.

  Even if the immobilizer amplifier 52 operates in the vicinity of the rated upper limit even during normal operation in which a short circuit does not occur, the load (peripheral circuit element) connected to the immobilizer amplifier 52 is assured (that is, In some cases, it is desirable to limit the current appropriately (with a constant level of voltage maintained) (for example, when the load is the reader 112 of the transponder 127 and the ID reading is frequently retried due to an abnormality in the transponder 127, etc.) ). On the other hand, in order to suppress a large current at the time of occurrence of a short circuit, there is a demand for giving priority to the current suppression effect even if the power supply output voltage is somewhat sacrificed. In this case, it is convenient to set the current limit to be limited step by step. Therefore, in the present embodiment, specifically, when the first current limiting transistor 65t has a passing current level of the second current limiting transistor 64t exceeding a predetermined value, the power supply operation command It is configured to operate so as to limit the input current of the signal (A). The function of setting the current limit to be limited to two levels having different levels depending on whether the immobilizer amplifier 52 is not short-circuited or short-circuited can be realized very easily. In this case, the overcurrent at the time of the non-short circuit is limited mainly by the second current limiting transistor 64t, and the large overcurrent at the time of the short circuit is the second current limiting transistor 64t and the first current limiting transistor. This is limited by the joint operation with the transistor 65t.

  The power supply circuit 50 of FIG. 5 has a constant voltage circuit 61 that receives the battery voltage VB and outputs a constant voltage. The constant voltage circuit 61 is a switching regulator type step-down circuit, for example, and its configuration is well known. The output of the constant voltage circuit 61 is controlled by a first drive transistor 62 f included in the first output drive control circuit 62. Specifically, the first driving transistor 62f becomes conductive when the power supply operation command signal (A) becomes Hi, and the power supply output from the constant voltage circuit 61 is allowed. In the present embodiment, the first driving transistor 62f is a MOS type transistor that has a high input impedance and is less likely to cause a problem in the discharge speed of the junction capacitance portion in order to reduce power consumption during driving and improve switching response. It is comprised by FET.

  On the other hand, the second output drive control circuit 63 located on the power output side includes the second drive transistor 63t described above. The second driving transistor 63t is a bipolar transistor, and has a bias resistor 63b for voltage feedback in order to stabilize the output voltage when not short-circuited. In order to secure the input-side sink current of the second driving transistor 63t, an intermediate driving transistor 62t made of a bipolar transistor is interposed between the first driving transistor 62f and the second driving transistor 63t. Has been inserted.

  The second current limiting transistor 64t is disposed on a path connecting the collector side of the second driving transistor 63t and the ground, and the collector input current to the second driving transistor 63t is detected by the detection resistor 64a. The The detected voltage is input to the base. When the detected voltage exceeds the forward voltage (0.6 V) between the collector and base of the second driving transistor 63t, the second current limiting transistor 64t becomes conductive. As a result, the output of the constant voltage circuit 61 leaks to the ground side via the path 64j. If it is not short-circuited, this leakage current is not so large, so the first current limiting transistor 65t is not conductive, and the output current of the second driving transistor 63t is in the first-stage current limiting state. On the other hand, in a state where a larger current is about to flow, such as when a short circuit occurs, the current leaking to the ground side via the second current limiting transistor 64t further increases, so the first current limiting transistor 65t. And the gate input voltage of the first driving transistor 62f is lowered, and the current level is further limited to a second-stage current limiting state (of course, even in a short circuit, the short current is relatively low). If it is smaller, the first-stage current limiting state may be maintained).

The block diagram which shows an example of the engine starting control system of this invention. The schematic diagram which shows an example of a steering lock mechanism. The block diagram which shows the detail of an immobility control part. The conceptual diagram of the security key using a transponder. FIG. 4 is a circuit diagram showing a configuration example of the power supply circuit of FIG. 3. Explanatory drawing of an effect | action of the immobility control part of FIG. The flowchart which shows the processing flow of the software which implement | achieves the function of the power supply restriction | limiting means of the immobility control part of FIG. FIG. 8 is a timing diagram explaining the processing of FIG. 7.

Explanation of symbols

1 Engine start control system 2 Portable device (security key)
3 Automobile 5 Immobility control unit 5F EEPROM (diag storage means)
50 Power supply circuit 52 Immobilizer amplifier 53 Main circuit (Imobi peripheral circuit elements)
54 short detection unit 61 constant voltage circuit 62f first driving transistor 63t second driving transistor 65t first current limiting transistor 64t second current limiting transistor 64, 65 current limiting circuit 112 reader 127 transponder 129 High frequency radio wave source

Claims (10)

An ID acquisition function for acquiring the user ID stored in the security key possessed by the user, and authenticating the acquired user ID. If the authentication result is acceptance authentication, the content indicates engine start permission. An immobilizer control unit having an engine start prohibition signal output function for outputting an engine start prohibition signal, which is a content indicating engine start prohibition when there is,
An immobilizer peripheral circuit element that is connected to the immobilizer controller and performs an electrical operation related to the basic function in a state where the load is larger than the control signal input / output processing by the immobilizer controller;
An immobilizer amplifier for driving the immobilizer peripheral circuit element;
A power supply circuit for supplying a power supply voltage to the immobilizer amplifier;
A short detection unit that detects whether an output to the immobil amplifier side of the power circuit is short-circuited based on a voltage level on a power supply line to the immobil amplifier;
A power limiting means for limiting a power output from the power circuit to the immobilizer amplifier when the short detection unit detects a short state for a predetermined time or more;
An engine start control system comprising: In the power supply circuit, a power output operation to the immobilizer amplifier is controlled based on a power supply operation command input from the immobilizer control unit,
The power limiting means is implemented on the immobilizer control unit, and receives a short detection input from the short detection unit, and controls output of the power operation command to the power circuit by software processing. The engine start control system according to claim 1, wherein a power output from the power supply circuit to the immobilizer amplifier is limited. The power limiting means is configured to input a power operation command signal from the immobilizer control unit to the power supply circuit, and when a short detection input duration from the short detection unit exceeds a predetermined reference time, 3. The engine start control system according to claim 2, wherein an input of the power operation command signal from the immobilizer control unit to the power circuit is cut off. 4. The engine start control system according to claim 2, further comprising diagnostic storage means for storing a detection history as an immobilizer amplifier abnormality when the short detection unit detects a short circuit of an output load of the power supply circuit. 5. The engine start control according to any one of claims 1 to 4, wherein the power supply circuit is provided with a current limiting circuit that limits an output current when an output to the immobilizer amplifier side is short-circuited. system. The power supply circuit includes a constant voltage circuit and a driving transistor for controlling an input voltage from the constant voltage circuit using a power supply operation command signal from the immobilizer control unit as a drive input, and the current limiting circuit includes the drive 6. The engine start control system according to claim 5, further comprising a current limiting transistor for limiting an output current of the operating transistor. The driving transistor operates in such a manner that a first driving transistor directly driven by an input of the power operation command signal and a part of an output of the first driving transistor are used as a driving input, A second driving transistor for controlling the output current to the immobilizer amplifier,
The current limiting circuit includes: a first current limiting transistor that limits an input current of the power operation command signal to the first driving transistor; and an input current at a power supply side terminal of the second driving transistor. The engine start control system according to claim 6, further comprising a second current limiting transistor for limiting. The first current limiting transistor operates to limit an input current of the power supply operation command signal when a passing current level of the second current limiting transistor exceeds a predetermined value. Item 8. The engine start control system according to Item 7. The security key is provided with a transponder storing the user ID,
The immobilizer peripheral circuit element includes a high frequency radio wave generation source that generates a high frequency radio wave for excitation for driving and exciting the transponder, and the immobilizer amplifier is for driving the high frequency radio wave generation source. The engine start control system according to any one of claims 1 to 8. The security key is a portable device that wirelessly transmits the user ID to the immobilizer control unit, and the transponder mounted on the security key constitutes a non-power backup authentication transmission unit for ID authentication by the wireless transmission. Item 10. The engine start control system according to Item 9.

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