FR2824301A1 - LIGHTING DIRECTION CONTROL UNIT OF A VEHICLE HEADLIGHT, AND ITS POWER SUPPLY - Google Patents

Abstract

The invention relates to a steering control unit comprising a device (12) for detecting the height of the vehicle, a power supply (10), a device (9) for controlling the direction of the optical axis of the light of a headlight, and a control device (7) which detects the attitude of the vehicle based on a signal obtained from the device (12) so that the control device (9) receives a signal for correcting the vehicle. after the change in attitude of the vehicle. A current limiting circuit is incorporated at the power end of the height sensing device (12), and power is transmitted through the power supply circuit (10) to the height sensing device via the intermediate of the current limiting circuit.Application to automobiles.

Description

The present invention relates to the compensation of circuit faults

  supply by short-circuiting between a line and a ground, in the case of a vehicle height detection device which detects the variation in height of the vehicle with respect to parts of the axle

  front or rear vehicle wheels.

  So that the lighting direction of a device

  of lighting mounted on a vehicle does not become irre-

  generally when the attitude of the vehicle in the direction of movement varies during the movement of the vehicle or when the vehicle is stationary, a mechanism is known, called the site angle adjustment mechanism, intended for

  regularly correct the lighting direction of the

  lighting sitive so that the direction variation

lighting is compensated.

  For example, an apparatus for adjusting the lighting direction of a lighting device has been proposed according to a variation in attitude of the vehicle (for example of pitch angle) on the basis of a signal from a height sensor

  vehicle mounted on the axle of the front or rear wheels.

  For powering vehicle height sensors

  cule, the predetermined voltage by a supply circuit of an electronic control unit ECU is transmitted to the

  sensor using for example a potentiometer.

  More specifically, the arrangement includes the detection of the attitude of the vehicle while a voltage of 5 V is applied to a first end of the potentiometer, the other end being connected to the ground line and the voltage being taken from a terminal. detection and being transmitted to an arithmetic circuit of the electronic control unit in the form of detected vehicle height information. When a fault by shorting the earth line or overcurrent appears in the power line connected to the vehicle height sensor for some reason, a problem of power system failure may arise because the output signal from the power supply circuit of the electronic control unit

  has an overload condition.

  Consequently, using an integrated circuit which can be a three-terminal regulator which contains a protection circuit in the event of overheating of the supply circuit, the problem can be solved, but the electronic unit of

order becomes expensive.

  The object of the invention is to avoid the breakdown of the supply circuit by incorporating a current limiting circuit at the end of the supply outlet connected to the

  vehicle height detection device.

  According to the invention, a current limiting circuit is placed at the output end of the power supply of a vehicle height detection device, in a power supply of the vehicle height detection device intended to detect the variation of

the attitude of the vehicle.

  Thus, according to the invention, a current of the vehicle height detection device is limited by the limitation circuit in the event of a breakdown by shorting the line to ground, so that the supply circuit is protected without the need to use an integrated circuit including a protection circuit in the event of overheating. Other features and advantages of the invention

  will be better understood on reading the description which will

  to follow examples of embodiments, made with reference to the appended drawings in which: FIG. 1 is a diagram of the basic configuration of a lighting direction control unit according to the invention; Figure 2 is a block diagram of an example of an elevation angle setting; FIG. 3 is a diagram of an example configuration of the supply circuit; FIG. 4 is a diagram of another example of a current limiting circuit; FIG. 5 is a diagram of another example of a circuit

  current limiting having diode and a tran

  sistor; and Figure 6 is a diagram of a current limiting circuit having two transistors. Vehicle power supply is used for power transmission to a detection device

  vehicle height and applies for example to an appliance

  adjustment of the suspension hardness as a function of a detection signal transmitted by a vehicle height detection device (in the case of a so-called "active" suspension), to a control unit of the

  lighting direction by a lighting device (mechanism

  elevation angle adjustment), etc. FIG. 1 represents the basic configuration of a lighting direction control unit 1 implementing a vehicle height detection device having a vehicle height detection device 2, a piloting device 3, a device 4 and

a vehicle headlight 5.

  A potentiometer that uses variations in resistance

  tance, and a sensor intended to ensure a magnetic detection

  ticks using a Hall effect element for example, can be cited as vehicle height detection devices 2 (or vehicle height sensors) intended to detect variations in vehicle height. Although FIG. 1 represents an example in which vehicle height sensors are fixed to the axles of the front and rear wheels respectively, the invention is not limited to this arrangement because the embodiment can be such that the height detection is only for front or rear wheels. The height detection device 2 is intended to detect the displacement in height according to the distance between the axle and the vehicle body, and the detected signal is used

  as fundamental information for obtaining the atti-

  study of the vehicle both when stationary and on the move.

  A piloting device 3 is intended to vary the direction of the optical axis of the light from a headlight 5 as a function of a signal from the control device 4, and comprises a piloting mechanism comprising an operating member having a power source, such as a motor or an electromagnet. The control device 4 detects the attitude of the vehicle on the basis of the signal which can be obtained with the height detection device 2 and transmits to the piloting device 3 a signal for correcting the control of the headlight lighting direction 5 after the change in attitude of the vehicle, the control being carried out using arithmetic operations executed by a microcomputer included in an electronic control unit of known type. In this case, the control device 4 comprises a supply circuit and energy is transmitted to the vehicle height detection devices by the supply circuit via a

  current limitation described below.

  In the case of an automobile lamp for example, the headlight 5, the lighting direction of which is adjusted by the control device 4, is a headlight, an anti-rust light

  bacon, a bend lamp and the like.

  FIG. 2 represents an exemplary configuration having a potentiometer as a device for detecting the height of the vehicle, the central element being the electronic unit 7 for controlling site angle adjustment incorporated

to the circuit.

  In the electronic control unit 7, an arithmetic circuit 8, a control circuit 9 and a circuit

  supply 10 intended to transmit a predefined voltage

  completed (5 V) to arithmetic circuit 8 and vehicle height sensor are incorporated, and a voltage is intended to be transmitted by a storage battery

11 to the supply circuit 10.

  A potentiometer 12 forming the vehicle height sensor is placed outside the electronic unit 7 and receives a voltage via a supply terminal 13 connected to the supply line 10a of the supply circuit 10. Ain i, one end of the potentiometer 12 forming a power supply terminal is connected to terminal 13 while the other end is connected to the ground line (GND).

  The signal received from the detection terminal of the poten-

  tiometer 12 is tran put to the arithmetic circuit 8 of the micro-

  computer and the attitude of the vehicle is obtained during operations performed on a received signal, so that a

  control signal is transmitted to the control circuit 9.

  On reception of the control signal from the aritEmetic circuit 8, the control circuit 9 transmits a control signal to an operating member 14 intended to vary the lighting direction of the lighting device.

  so that the amount of steering is set.

  As the incorporation of an integrated circuit provided with a protection circuit in the event of overheating in the supply circuit 10 of the electronic control unit increases the cost, a method of forming a circuit is usually implemented power supply which transmits a predetermined voltage (5 V) by mounting on the outside of a power transistor on a dog timer

  guard (micro- detection and reset circuit

  computer that is no longer responding). In this case, a circuit for limiting the output current is also incorporated so that it prevents deterioration of the power transistor in the event of a short circuit between the over-voltage line and ground

in the supply line.

  As the supply line 10a of the vehicle height sensor leaves the electronic control unit 7, the risk of shorting the line to ground is greater in this circuit than in any other circuit. Consequently, the electronic control unit (more precisely its arithmetic circuit) must detect this failure by shorting the line to earth to indicate to the driver of the vehicle that failure when it

occurs.

  When the supply circuit 10 of the electric unit

  control board 7 has a protection function in the event of overheating, a limitation of the AC current for short-circuiting the power supply line lOa to earth includes the transmission of energy to the vehicle height sensor by connection a current limiting resistor at terminal 13 for example. More specifically, the short-circuit current between the line and the ground can be limited by insertion into the supply line 10a of a resistor which is connected in series with the height sensor of the vehicle. However, the value of the resistance must be reduced enough so that the influence of this during the automatic elevation angle adjustment is reduced. If the resistance value is 1% of that of potentiometer 12 which has a value of kQ for example, it is necessary to use a current limiting resistor having a value of approximately Q. Nevertheless, like the current limitation has a current value of approximately 100 to 150 mA for example, when trying to protect the circuit by limiting the current at the output of the power supply circuit of the electronic control unit, the voltage of power supply drops by 5 V when the short-circuit current between the line and the earth is limited by the insertion of a resistor of about 50 Q in

  the vehicle height sensor supply line.

  Thus, a drawback appears since the short-circuit between the line and the ground cannot be determined when the arithmetic circuit 8 is reset. If a short circuit between the supply line and ground occurs

  in the supply line joining the height sensor

  the vehicle, a current of about 100 mA (5 V / 50 Q) must be consumed for a supply voltage of 5 V at terminal 13. However, the current limitation value must be increased significantly to prevent condition

  above, so that the transistor can

  must have a large dimension and the cost of

  the power supply is therefore increased.

  To avoid this drawback, the current limiting circuit is placed at the output end directed towards the vehicle height sensor and the circuit

  is realized in the form of a constant current source.

  FIG. 3 represents an example of circuit 15 of the power supply. In this example, the watchdog timer and an integrated supply circuit 16 (for example of the TA8007F type) are used and the terminals of the integrated circuit have the following meaning: BIAS: supply terminal (receiving a voltage + B from the storage battery 11), OUT: terminal for consuming the basic current of the power transistor 17 intended for transmitting energy, COMP: terminal for compensating the phase of the supply, Vcc: supply terminal at 5 V, Tc: terminal for adjusting the time constant of the watchdog timer, CK: terminal for inputting the clock signal (input into the watchdog timer) from the microcomputer 18, and RST: reset signal output terminal (intended to create a reset pulse when power is restored and when control is lost)

to the microcomputer 18.

GND is the mass.

  The voltage + B of the storage battery is trans-

  put by a resistor 19 at the emitter of the PNP power transistor 17 and the collector of the power transistor is connected to the power supply line 10a at 5 V. In addition, the base of the power transistor 17 is connected by a

resistor 20 at the OUT terminal.

  A PNP transistor 21 is placed in the preceding stage of power transistor 17 to form a circuit for limiting the current of transistor 17. More precisely, the voltage + B of the accumulator part is transmitted to the emitter of transistor 21 , the base of transistor 21 is connected to the emitter of transistor 17 and the collector of

  transistor 21 is connected to the base of transistor 17.

  Reference 22 designates a capacitor connected to the

BIAS terminal.

  The collector of transistor 17 is connected to terminal Vcc of the integrated circuit 16 and it is also connected by a

  capacitor 23 at terminal COMP of integrated circuit 16.

  Among the resistors 24 and 25 connected to the 5 V supply line, the resistor 24, associated with a capacitor 26 connected in series with the resistor 24 and which is also grounded, is used for determining the watchdog timer time constant, and a connection node of the resistor 24 and the capacitor 26 is connected to the terminal Tc of the integrated circuit 16. In addition, the resistor 25 is connected to the terminal RST and a lifting resistance required for this

  terminal forms an exit point with open collector.

  A first end of a capacitor 27 is connected

  tee at power line 10a and the other end is grounded. In addition, a capacitor 28 is inserted in the

  signal line to terminal CK from the microphone

  computer 18 forming the arithmetic circuit 8.

  A current limiting circuit 29 associated with the supply line 10a directed to the vehicle height sensor is embodied by a constant current source comprising a current mirror circuit 30 in this embodiment of the invention. More specifically, two PNP transistors 31 and 32 are such that the emitters of the two transistors are connected to the power supply line 10a, the bases of the two transistors are connected to each other, the common base is connected to the collector of transistor 31, and the common collector is earthed via a resistor 33. In addition, the collector output of transistor 32 is transmitted to the sensor

  vehicle height (not shown) as feed signal

tation.

  While the vehicle height sensor is operating

  normally operates without presenting a short circuit between the line and the ground, the transistors 31 and 32 constituting the

  current mirror circuit 30 have saturated and are practi-

  only maintained in the conductive state so that a supply voltage of approximately 5 V is applied to the vehicle height sensor.

  If a short circuit occurs between the power line

  tation and mass, for the supply line lOa of the vehicle height sensor while the current limitation value of the current mirror circuit 30 is set at approximately 5 mA for example, the transistors 31 and 32 become sources of constant current at around 5 mA and the short-circuit current between the line and earth is limited to this value. Consequently, the energy consumed by the transistors remains equal to 5 () x 5 (mA) = 25 mW. Consequently, the watchdog timer controls the circulation in which the supply voltage of the electronic control unit has dropped at the time of the appearance of the short circuit and therefore prevents the microcomputer 18 from being reset by the RST terminal. . In addition, precautions can be taken to compensate for the short circuit between the line and the ma se without putting the microcomputer on standby, by circulation of the excess current due to the short circuit so that it lowers the supply voltage

  of the electronic control unit.

  Furthermore, the configuration of the current limiting circuit is not limited to that shown in FIG. 3, since it can correspond to Example 34 of FIG. 4 in which the resistors 35 and 36 are connected to the emitters of the respective transistors 31 and 32 and connected to the supply line 10a. In this circuit, the reaction resistors 35 and 36 are inserted between the supply line lOa and the respective transmitters,

  when the transistors are unbalanced.

  In the example of circuit 37 in FIG. 5, the emitter of a PNP transistor 38 is connected to a resistor 39 which is connected to the supply line 10a and two diodes in series 40 and 41 are inserted between the base of transistor 38 and the supply line 10a. More specifically, the anode of the diode 40 is connected to the supply line 10a and the cathode of the diode is connected by the diode 41 placed in the direct direction at the base of the transistor 38 and is grounded by the by means of a resistor 42. In addition, the supply voltage is transmitted to the

  height of the vehicle by the collector of transistor 38.

  In any case, transistors have been used to form a circuit such as a constant current source having a predetermined limiting current value (from a few milliamps to about 10 mA), and energy is transmitted by this line lOa d power to the vehicle height sensor via the constant current source. In other words, when energy is normally transmitted to the vehicle height sensor without short circuit between the line and the ground, the transistors are saturated and maintained practically in the conducting state, so that a voltage preset (5 V) is applied to the vehicle height sensor. When a short circuit occurs between the power line and ground in the vehicle height sensor further, the current is limited by the effect of the constant current source. By adjusting the limit value of the

  current at this time, a cost reduction can be realized

  since the minimum capacity required of the transistor

  power 17 which transmits energy can be used.

  In addition, the transistors 44 and 45 are used to constitute a current limiter as shown in the example of circuit 43 in FIG. 6. The PNP transistor 44 is more precisely placed in the supply line 10a with its base at the ground via a resistor 46. In addition, a voltage Vcc of 5 V is transmitted by a resistor 47 to the emitter of transistor 44 and a supply voltage is transmitted to the height sensor of the

  vehicle by the collector of transistor 44.

  The base of the PNP transistor 45 is connected to the emitter of transistor 44, and a Vcc ten ion of 5 V is transmitted to the emitter of transistor 45. The collector of transistor 45

  is also connected to the base of transistor 44.

  As the above description clearly indicates,

  according to the invention, the current of a height detection device of a vehicle is limited by a current limiting circuit in the event of a short circuit between the supply line and the ground, so that the circuit d the power supply is protected without the need to use an integrated circuit, such as a three-terminal regulator, which

  contains a protection circuit in the event of overheating.

  In addition, even when a short circuit between the line

  and the mass appears in the supply line, the circuit

  arithmetic baking is not adversely affected by the reduction in supply voltage as the current limiting action is determined by the constant current source. Measures can therefore be taken to satisfactorily remedy the short circuit between

  the power line and ground.

  In addition, when applying the invention to a headlight lighting control unit, satisfactory precautions are taken to compensate for the effects of a short circuit between the power line. and mass, so the security of

  movement of the vehicle is ensured.

  Of course, various modifications can be made by those skilled in the art to the power supplies and units which have just been described only by way of example.

  nonlimiting without departing from the scope of the invention.

Claims (4)

  1. Power supply for transmitting energy to a device (2) for detecting the height of a vehicle, characterized in that a current limiting circuit is mounted at one end of the energy transmission   to the vehicle height detection device (2).   2. Power supply according to claim 1, characterized in that the current limiting circuit forms a constant current source.   3. lighting headlight control unit, comprising a vehicle height detection device (2) for detecting the variation in vehicle height, an electrical power supply (10) which transmits energy to the vehicle height detection device (2), a piloting device (9) for varying the direction of the optical axis of the light of a vehicle headlight, and a control device (7) for detecting the attitude of the vehicle according to a signal obtained from the vehicle height detection device (2) so that the piloting device receives a correction signal linked to the adjustment of the lighting direction by the headlight after the variation in attitude of the vehicle, characterized in that a current limiting circuit is incorporated at the supply end of the device (2) for detecting the height of the vehicle, and   energy is transmitted by a supply circuit   tation (10) placed in the control device (7) via the current limiting circuit at   vehicle height detection device (2).   4. Unit according to claim 3, characterized in that the current limiting circuit forms a source of