JPH09277905A - Vehicle anti-theft device - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To prevent an engine from being able to start due to disconnection of a communication line. An EEPROM of an immobilizer ECU 20
The reference code is stored in 20a, and the processing unit 20
b compares the secret code sent from the transponder 12 of the key 10 with the reference code. Engine ECU2
No. 4 transmits a rolling code when the engine speed reaches 500 rpm. Immobilizer ECU2
When 0 matches the code, the rolling code is transmitted. The engine ECU 24 stops the engine when the rolling code cannot be received within a predetermined time. In addition, the backup memory 24d in the engine ECU 24
The fact that the engine 30 is stopped is stored. In the next engine start, speed up the rolling code communication. Also, when the backup power source of the backup memory 24d is disconnected, the communication is similarly speeded up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-theft device for a vehicle, particularly when an engine starting operation is performed by using an incorrect key or an illegal circuit change.
The present invention relates to a device that stops the start of an engine.

[0002]

2. Description of the Related Art In automobiles and the like, a lock device that can be released by a correct key is provided on a door or the like, and an engine can be started only by a correct ignition key. In this way, the vehicle is prevented from being stolen. To ensure the prevention of theft, it has been proposed to equip a further anti-theft mechanism, which is being put into practical use.

[0003] For example, an automobile technology casebook / issue number 95
603 (Japan Automobile Manufacturers Association Intellectual Property Section 1995.1
2.1) discloses a vehicle anti-theft device that interlocks with an ignition key and prohibits the start of the engine when a correct ignition key is not used.

In this vehicle anti-theft device, a transponder for transmitting a personal identification code is built in an ignition key. This transponder receives electric power from radio waves from an antenna provided in the key cylinder and transmits the stored personal identification code. An immobilizer (Imobilizer) ECU is connected to the antenna of the key cylinder, and it is determined whether or not the transmitted password is correct. Further, the immobilizer ECU is connected to an engine ECU that controls engine ignition (ignition) and fuel supply (fuel injection), and informs the engine ECU whether a correct password has been obtained. If the correct password is not obtained in the immobilizer ECU, the engine ECU prohibits the supply of fuel to the engine and the ignition in the engine, and controls the stop of the engine. As a result, it is possible to prevent the engine from starting and the vehicle from running when the user attempts to start without using the correct key. The engine ECU is
The engine is started as usual in accordance with the ignition being turned on by operating the ignition key, and receives the signal from the immobilizer ECU to stop the engine.

Here, the starter motor is rotating at the initial stage of engine startup, and the power supply voltage fluctuates greatly. Therefore, the communication between the immobilizer ECU and the engine ECU is performed after the engine speed reaches 500 rpm or more.

That is, the engine speed is 500 rpm.
When the above is reached, the engine ECU creates a predetermined rolling code by generating a random number, and the immobilizer E
Send to CU. When the immobilizer ECU recognizes the correct key, the immobilizer ECU generates a rolling code by the same random number generation and returns the rolling code to the engine ECU.
As a result, it is confirmed by the engine ECU that the correct key has been used, the key confirmation process ends, and normal engine operation continues.

On the other hand, when the correct rolling code is not returned within the predetermined time, the engine ECU stops ignition and fuel injection. Therefore, if the operation is not performed with the correct key, the engine is stopped.

[0008]

However, in this conventional example, the engine is not stopped for a few seconds (until it is confirmed that the rolling code is not returned) after the engine speed reaches 500 rpm. Therefore, by repeating this, the vehicle runs to some extent.

Further, a backup memory is provided inside the engine ECU to count and store the number of times of engine stop control at the time of starting, and when an abnormal starting operation is performed several times in succession, the engine is stopped. It is also possible to perform processing such as not starting.

However, if the power supply to the backup memory is cut off, the count value up to the previous time will be cleared, and eventually there will be a problem that the vehicle can run to some extent.

The present invention has been made to solve the above-mentioned problems, and a vehicle antitheft device capable of performing a sufficient traveling stop process even when the power supply to the backup memory is cut off. The purpose is to provide.

[0012]

According to the present invention, the code of the key inserted in the key cylinder is compared with the reference code stored in the storage means, and the result determines whether to permit the engine to start. In vehicle anti-theft devices,
The backup memory includes a backup memory connected to the backup power source and storing data as to whether or not the engine start is permitted, and a backup power source abnormality detecting means for detecting that the power supply to the backup memory is cut off.

Further, when there is an abnormality in the backup power source, the timing for determining whether or not to permit the engine start based on the collation result of the collating means is changed earlier.

As described above, when there is an abnormality in the backup power supply that supplies power to the backup memory, the timing for determining whether to permit engine start is advanced. Therefore, it is possible to shorten the starting time of the engine in response to an illegal starting operation. Therefore, the engine can be stopped early in the case of an illegal start operation performed after the battery is removed, and the running of the vehicle can be effectively prevented.

According to another aspect of the invention, the storage means for storing a predetermined reference code, the code of the key inserted in the key cylinder, and the reference code stored in the storage means are collated by communication. The code collating means is connected to the code collating means via a communication line, and it is determined whether or not the engine start is prohibited according to the collation result sent via the communication line. An engine starting means for controlling, an engine speed detecting means for detecting that the engine speed has reached a predetermined speed, a backup memory backed up by a backup power supply and storing whether or not a previous engine start is prohibited, including.

When the previous engine start is not prohibited, the verification result is communicated from the verification means to the engine start means when the engine speed exceeds a predetermined speed, and the previous engine start is prohibited. If there is an abnormality in the backup power supply or the backup power supply, the inquiry result is communicated from the collating means to the engine starting means before the engine speed reaches the predetermined number, and it is determined whether to permit the engine start. It is characterized by changing the timing early.

By controlling in this manner, normally, the collating means and the engine starting means can communicate with each other after the engine speed reaches a predetermined value, for example, 500 rpm.
This makes it possible to make a determination by communication after the starter motor has been driven, and it is possible to eliminate the influence of an error or the like due to a decrease in the power supply voltage due to the starter motor being driven.

On the other hand, when the starting of the engine is prohibited or the memory of the backup power supply is abnormal, the engine is rotated at a predetermined speed for the next engine starting.
For example, the determination is performed before reaching 500 rpm. In this way, if the determination is made up to the rotation speed at which the normal vehicle cannot travel, such as when the engine rotation speed is 500 rpm or less, the vehicle is driven to a certain extent by repeated incorrect operations multiple times or an incorrect start operation such as removing the battery. It is possible to effectively prevent the vehicle from running.

In still another aspect of the invention, the engine starting means continues communication with the code collating means for a predetermined time even after the engine starting prohibition process when the judgment timing is advanced, and the engine starting means communicates. When the communication that the code of the key is correct is received from the code collating means while continuing, the data is stored in the backup memory that the engine start at that time is not prohibited.

When the engine speed is below a predetermined value, there is a relatively high possibility that an error will occur in communication. Therefore, it is possible that the engine is stopped despite the correct starting operation. If communication is continued after the engine is stopped, this is recognized as a legal start operation, and a sufficient time is determined in the next operation. Therefore, it is possible to prevent the legitimate operation from being continuously recognized by mistake.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

[Entire System Configuration] FIG. 1 is a diagram showing an entire system of the vehicle antitheft device according to the present embodiment. A transponder 12 is incorporated in an ignition key 10 that is also used to open and close a door lock of a vehicle. This transponder 12 includes an antenna, a power supply circuit, a storage unit, a readout circuit, a transmission circuit, and the like.
Upon receiving a predetermined radio wave from the outside, the transponder 12 receives the radio wave with an antenna and supplies the radio wave to a power supply circuit. The power supply circuit obtains electric power from the received radio wave and supplies the electric power to the internal circuit. Then, the personal identification number stored in the storage unit is read out and transmitted from the antenna via the transmission circuit.

The key cylinder 14 can be rotated by the ignition key 10 having a predetermined shape (or a predetermined magnetization, etc.), and the accessory switch, ignition switch, starter switch, etc., depending on the rotation position, as in the usual case. Various switches such as are operated.
That is, the accessory switch controls on / off of the power of the accessory device, the ignition switch controls on / off of the power of devices required for traveling such as a spark plug, and the starter switch controls on / off of the power of the starter motor. It should be noted that rotation is possible only when the tip of the inserted ignition key 10 fits into the key cylinder 14.

An antenna 16 is provided around the front side of the key cylinder 14 (the side into which the key 10 is inserted). A predetermined radio wave is transmitted from the antenna 16 toward the transponder 12, and a radio wave from the transponder 12 is received by the antenna 16.

An immobilizer ECU 20 is connected to the antenna 16 via an amplifier 18 for amplifying a received signal. A key insertion detection switch 22 is provided in the key cylinder 14, and a signal indicating whether or not the key 10 is inserted is supplied to the immobilizer ECU 20. Therefore, the immobilizer ECU 20 operates the key 10
Can be detected at the time of insertion, and at this time, a predetermined radio wave can be transmitted from the antenna 16 and a reply from the transponder 12 can be received.

The immobilizer ECU 20 stores therein a reference code corresponding to the secret code of the key 10. In this example, the reference code is stored in the EEPROM 20a. Then, the processing unit 20b causes the antenna 16
It is determined whether the personal identification code sent from the transponder 12 via the reference code matches the reference code.

An engine ECU 24 is connected to the immobilizer ECU 20 via a communication line. In this engine ECU 24, the immobilizer ECU 20
The terminal that receives the signal from the terminal is the terminal IMI, and the terminal that transmits the signal to the immobilizer ECU 20 is the terminal IMO.

The engine ECU 24 controls an ignition (plug ignition) control unit 26 and a fuel injection (fuel supply) control unit 28. The ignition control unit 26 and the fuel injection control unit 28 are connected to the engine 30, and control ignition and fuel supply of the engine by these.

That is, the engine ECU 24 responds to the ignition on by the rotation of the key cylinder 14,
Enables power supply to the spark plug and fuel supply to the engine. In accordance with the rotation of the engine 30 in accordance with the rotation of the starter motor, predetermined ignition and fuel supply are performed, and after the engine 30 starts to rotate, ignition and fuel supply are continuously controlled.

The engine ECU 24 is connected to a rotation sensor 32 which is attached to the engine 30 and detects the number of revolutions of the engine 30, and detects the number of revolutions of the engine 30.

The immobilizer ECU 20 includes an encoder 2
0c and a random number generator 20d are provided. Encoder 2
0c generates a start code when the immobilizer ECU 20 is operating, and the random number generator 20d generates a predetermined rolling code. The immobilizer ECU
The 20 is also provided with a transmission / reception circuit for communication via the antenna 16, a communication interface for communication with the engine ECU 24, and the like.

The engine ECU 24 also includes a processing unit 2
4a, a decoder 24b, a random number generator 24c, and a backup memory 24d are provided. The decoder 24b is
The starting code sent from the immobilizer ECU 20 is decoded, and the random number generator 24c generates a predetermined rolling code. Further, the backup memory 24d stores a count value, a flag, etc., which are necessary for the next processing. The processing unit 24a is for performing various processes, and the engine ECU 24 is also provided with a communication interface for communicating with the immobilizer ECU.

The backup memory 24d is an SRAM which is constantly supplied with electric power from the battery 34 and holds the stored contents. The battery 34 also supplies power for operating various devices.

[Operation] Next, the operation of this system will be described with reference to the timing charts of FIGS. 2 and 3 and the flowcharts of FIGS.

First, the driver sets the ignition key 1
When 0 is inserted into the key groove of the key cylinder 16, the key insertion detection switch 22 detects this and the power is turned on,
Each part starts operation. That is, the immobilizer ECU
20 starts transmitting the start code to the engine ECU 24 and waits for reception of a signal from the antenna 16. Then, when the signal from the antenna 16 is received, it is determined whether or not the secret code sent from the transponder 12 matches the reference code stored in the EEPROM 20a.

If they match, the start code is sent while waiting for the rolling code to be received, and when the code is received, the rolling code is returned. On the other hand, if the secret code and the reference code do not match, the engine EC
The communication line to U24 is fixed to L. If the key insertion detection switch 22 is not provided, the operation may be started by turning on the accessory switch or turning on the ignition switch.

Then, when the ignition switch is turned on in response to the operation of the key 10, the engine ECU 24
The ignition control unit 26 and the fuel injection control unit 28 make the engine 30 operable. Furthermore, by turning on the starter switch,
The starter motor is turned on, the engine starts to rotate, and ignition and fuel supply are started.

[Starting Code] As described above, when the key insertion detection switch 22 or the accessory switch is turned on, the immobilizer ECU 20 starts its operation, and the encoder 20c generates a starting code to start the transmission. To do. As a result, the starting code appears at the terminal IMI of the engine ECU 24, as shown in FIG. This start code is repeatedly sent by the immobilizer ECU 20. In addition, as the start code,
Various means such as encryption using a combination of levels H and L, PWH (pulse width modulation), and PSK (phase shift keying) can be applied.

"Flag XIMMOC" First, engine E
The CU first determines the value of the flag XIMMOC, which is set to 0 in the routine that is first performed by connecting the battery. This flag XIMMOC is also set to 0 when there is an error during the previous engine start, and is set to 1 when the engine start is normally completed.

Therefore, by checking the value of the flag XIMMOC at the beginning of the process in the engine ECU 24, it is determined whether the battery is once disconnected or the previous error occurred. The flag XIMMOC
Is a backup memory 24d in the engine ECU 24.
Is stored in Therefore, it will not be reset unless the battery is removed.

"In the case of normal operation last time" First, the flag XIMM
The case where the previous engine start with OC = 1 was normal will be described with reference to FIGS.

First, the engine ECU 24 monitors whether the terminal IMI for receiving the communication from the immobilizer ECU 20 is fixed to L from the state of the ignition switch being on (S1). This determination is made by measuring the duration of L of the terminal IMI with a counter or the like, and detecting it when it becomes a predetermined value or more. The determination of S1 is always made.

The fact that the IMI is L means that
The immobilizer ECU 20 outputs L, which means detection of fraud, and the flag XIMMOC =
After setting to 0 (S2), stop the engine (S
3).

As a result, when the immobilizer ECU 20 detects a mismatch with the reference code of the secret code or some injustice and brings the communication line to the L level, this is caused by the L level of the terminal IMI.
Detected in 4. Then, the engine ECU 24
However, since the ignition and the fuel injection are prohibited, the engine 30 is stopped.

Next, when the H level is detected at the terminal IMI, 1 is added to the fail counter CIMMOF (S4). As described above, in the present embodiment, the counter CIMMOF, which indicates the number of consecutive abnormal terminations in the engine starting process, is incremented at the beginning of the operation. Therefore, when the processing ends abnormally (on the way), the counter CIMMOF
Can be counted up. That is, when the ignition switch is turned off during the process, this counter CIMMOF is incremented. In addition,
This counter CIMMOF is a backup memory 24d.
Is stored within.

When the CIMMOF is counted up, it is determined whether this CIMMOF is 1. That is, if there is no error up to the last time, this counter CIMMOF
Is 0 and CIMMOF is 1 by adding 1 to this. Therefore, in this case, the rolling code reception waiting time n seconds is set to a maximum value, for example, 3 seconds (S
6). If CIMMOF = 2, n = 2 seconds (S
7, S8), and if CIMMOF = 3, n = 1 second is set (S9, S10). Thus, n is the counter CI
By gradually setting the waiting time of the rolling code in the engine ECU 24 by sequentially setting it smaller in accordance with the value of the MMOF, it is possible to keep the traveling of the vehicle below a predetermined value due to repeated unauthorized use.

Then, it is determined whether CIMMOF> 3 (S
11) If CIMMOF> 3, S2, S3
Then, the engine 30 is stopped. As a result, the engine 30 can be stopped at an early stage, and traveling due to an illegal start operation can be completely disabled.

When CIMMOF is 3 or less,
Next, it is determined whether the engine speed has reached 500 rpm (S12). And the engine speed is 500 rpm
This judgment is repeated up to and when 500 rpm is reached, it is judged whether the start code is received (S1).
3). The detection of the start code itself is repeated from the beginning of the process.

In this S15, the engine ECU 24
When it is determined that a signal is received at the terminal IMI of, but is different from the start code, m seconds (for example, 500
msec) is determined (S14). And
When the start code is not received even after m seconds have passed, the flag XIMMOC = 0 is set (S2), and the engine is stopped (S3).

As described above, by using the start code, not only the L level output from the immobilizer ECU 20 but also the fixation of the terminal IMI to the H level due to the disconnection of the line can be detected as an abnormality.
Can be stopped.

On the other hand, if the start code is received in S13, the engine ECU 24 sends the rolling code to the immobilizer ECU 20 (S15).
This rolling code is performed by a random number generator 24c in the engine ECU 24 in a predetermined manner.

Here, the immobilizer ECU 20 detects the match between the received personal identification code and the reference code stored in the EEPROM 20a,
When the reception of the rolling code is confirmed, the rolling code corresponding to the rolling code is generated by utilizing the random number generator 20d in the self. Engine E
Since the random number generation mechanism in the CU 24 and the immobilizer ECU 20 is configured in advance to correspond to each other, it will always correspond to the rolling code generated. Then, the immobilizer ECU 20 sends the rolling code to the engine ECU 24. When the secret code and the reference code do not match, the immobilizer ECU 20 sets the communication line to L at that time. Engine ECU2
4 constantly monitors the state of the terminal IMI, and when L of IMI is detected, the engine 30 is stopped at that time.

The engine ECU 24 determines whether it has received a rolling code corresponding to the rolling code sent by itself (S16). After the value is returned to 0, the process ends. Therefore, the counter CIMMOF = 0 is reset only when the processing is normally completed.

On the other hand, if the correct rolling code is not returned despite the rolling code being sent, the normal operation is not performed. Therefore, in this case, it is determined whether n seconds have elapsed (S18). Then, the rolling code and the judgment of receiving the rolling code are repeated for 3 seconds, and when the rolling code cannot be received within n seconds, the process proceeds to S12, and XIMMOC is performed.
= 0 (S2) and the engine 30 is stopped (S3).

Here, n is any of 3, 2, and 1 seconds set in any of S6, 8, and 10. Therefore, this reception waiting time is shortened each time the engine starting operation has been abnormally ended. In particular, as described above, the CIMMOF is counted up before the engine is started, and thus the waiting time reduction process is performed even when the ignition is turned off during the start process.

It should be noted that the reason why the start code is detected and the rolling code is transmitted and received after the engine speed reaches 500 rpm is that the starter motor may be operating when the engine speed is 500 rpm or less. This is because the power supply voltage is unstable in this case and the probability of error occurrence is high.

In this way, the immobilizer ECU 20
Not the H of the communication line but the start code informs the engine ECU 24 that the operation is normal. Therefore, when the communication line is disconnected, the start code is not sent. Therefore, the engine ECU 24 can stop the engine because the start code is not sent. The immobilizer ECU 20 repeats the transmission of the start code even after the transmission of the rolling code. The engine ECU 24 can always confirm the connection of the communication line. Also,
It will be easier to restart when the engine is stalled.

As described above, when there is no error in the previous processing, that is, the flag XIMMOC = 1
The processing in the case of is performed. Further, when an abnormality is detected and the engine 30 is stopped, XIMMOC = 0 is set.

"In the case of battery disconnection or previous abnormality" It was determined to be abnormal after the battery was disconnected or in the processing at the previous engine start (flag XIMMOC =
The case (0) will be described with reference to FIGS.

Also in this case, the immobilizer ECU
20 detects engine fraud when it detects fraud
The communication line to is set to L. Therefore, the engine ECU 24
Monitors the terminal IMI and determines whether it is fixed at L (S21). If the terminal IMI is fixed to L, the engine 30 is stopped (S2
8).

On the other hand, the engine ECU 24 uses the terminal IMI.
When the H level at is detected, the routine immediately starts to check the rolling code. That is, the engine ECU 24 immediately starts transmitting the rolling code from the terminal IMO without waiting for the engine speed to reach 500 rpm (S22). Immobilizer ECU
20 sends a start code unless it detects fraud. However, when the rolling code is received from the engine ECU 24, a rolling code corresponding to the rolling code is generated and returned to the engine ECU 24.

While transmitting the rolling code from the terminal IMI, the engine ECU 24 monitors the state of the terminal IMI and determines whether the rolling code is received (S23). Then, when the rolling code can be received, the flag XIMMOC = 1 is set (S24), and the process ends.

On the other hand, if the rolling code cannot be received, it is determined whether the engine speed has reached 500 rpm (S25). And the engine speed is 500
The rolling code transmission and the rolling code reception determination are repeated until rpm is reached. Engine speed is 5
If the rolling code cannot be detected before reaching 00 rpm, the engine is stopped (S26).
A normal vehicle cannot run at all when the engine speed is 500 rpm or less. So, by this process,
You can surely stop traveling.

Further, in S26, after stopping the engine 30, it is determined whether the ignition is turned off (S27). Then, if the ignition is not turned off, the process returns to S22. As a result, the transmission of the rolling code from the engine ECU 24 and the transmission of the rolling code from the immobilizer ECU 20 are continued until the ignition is turned off. Therefore, the engine ECU 24 can receive the rolling code even after the engine is stopped. Then, in S23, when the rolling code is successfully received, the flag X
IMMOC = 1 is reset (S24). Therefore,
The next engine start can be performed with XIMMOC = 1.

The value of the counter CIMMOF is not used in the processing when XIMMOC = 0. Therefore, it is preferable to reset CIMMOF to 0 at the beginning of this processing. Note that CIMMOF may be reset to 0 when XIMMOC = 1 is set.

In S27, if the ignition is turned off, the process ends. Therefore, when the rolling code cannot be received before the ignition is turned off, the flag XIMMOC remains 0.

As described above, by transmitting / receiving the rolling code even after the engine is stopped, it is possible to prevent a situation in which the engine cannot be started when there is no injustice. That is, in the communication up to the engine speed of 500 rpm, a communication error is likely to occur, and the communication of the correct rolling code may not be performed even when there is no injustice. On the other hand, after the engine is stopped, the starter motor does not operate and reliable communication can be performed. Therefore, it is possible to prevent the engine from being unable to start due to a simple communication error.

As described above, in this embodiment, when the power supply to the backup memory 24d is cut off and the contents are cleared, the rolling code is transmitted and received in the next process at an early stage. That is, if the rolling code communication is not normally completed before the engine speed reaches 500 rpm, the engine is stopped.
Therefore, when the backup power supply line is disconnected, the engine does not reach 500 rpm and the vehicle can be reliably stopped. In particular, since the flag XIMMOC = 0 is set to the value at the time of abnormality, it is easy to set the value of the flag XIMMOC with the disappearance of the stored contents by turning off the power. That is, during the normal initial operation, this flag XIM
By clearing MOC to zero, you can set the previous abnormality.

Further, according to the present embodiment, the backup memory 24d receives the electric power from the battery 34 and holds the contents thereof. Then, when the power supply to the backup memory 24d is cut off, the flag XIMMOC is reset to 0. Therefore, at the next engine start, the rolling code transmission / reception starts immediately after the start of processing. Therefore, an effective engine stop process can be performed when the battery is removed.

Further, according to the above-mentioned embodiment, the starting code is transmitted before transmitting / receiving the rolling code, but the flag XIMMOC functions even if the starting code is not provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an entire system.

FIG. 2 is a timing chart showing the operation of the embodiment (previously normal).

FIG. 3 is a timing chart showing the operation of the embodiment (previous abnormality).

FIG. 4 is a flowchart showing the operation of the embodiment (normal last time).

FIG. 5 is a flowchart (2) showing the operation of the embodiment.
Is (previously normal).

FIG. 6 is a flowchart showing the operation of the embodiment (previous abnormality).

[Explanation of symbols]

10 ignition keys, 12 transponders, 1
4 key cylinder, 20 immobilizer ECU, 24
Engine ECU, 26 Ignition control unit, 28
Fuel injection control unit, 30 engine,
20a EEPROM, 20c encoder, 24b decoder, 24d backup memory.

Claims (3)

[Claims] 1. A vehicle antitheft device for checking the code of a key inserted in a key cylinder and a reference code stored in a storage means, and determining whether to permit engine start according to the result of the backup. The backup power supply is connected to the power supply and includes a backup memory that stores data as to whether or not the engine start is permitted and a backup power supply abnormality detection unit that detects that the power supply to the backup memory is cut off. A vehicle anti-theft device, characterized in that if there is, the timing for determining whether to permit engine start based on the result of the collation by the collating means is changed earlier. 2. A storage means for storing a predetermined reference code, a code collating means for collating the code of the key inserted in the key cylinder with the reference code stored in the storage means by communication, and the code. An engine starting unit that is connected to the matching unit via a communication line, determines whether to prohibit the engine start according to the matching result sent via the communication line, and controls the engine start according to this. Includes engine speed detection means that detects when the engine speed has reached a specified speed, and backup memory that is backed up by a backup power supply and that stores whether or not the previous engine start was prohibited. Is not prohibited, when the engine speed exceeds a predetermined speed, The verification result is communicated, and if the previous engine start is prohibited or there is an abnormality in the backup power supply, communication of the inquiry result from the verification means to the engine start means before the engine speed reaches the predetermined number. The antitheft device for a vehicle, characterized in that the timing of determining whether to permit engine start is changed early. 3. The apparatus according to claim 1 or 2, wherein the engine starting means, when the judgment time is advanced,
When the communication with the code collating means is continued for a predetermined time even after the engine start prohibiting process, and the communication is received from the code collating means that the key code is correct while the engine starting means continues the communication, An anti-theft device for a vehicle, which stores data in a backup memory that engine starting at that time is not prohibited.