JPH064672U - Power circuit for tachograph - Google Patents

Abstract

(57) [Abstract] [Purpose] In a tachograph power supply circuit that supplies battery power to a drive circuit that drives a DC motor as a drive source for recording according to vehicle speed, while eliminating waste of battery power, Turn on the ignition switch
It is not affected by the noise generated by the off operation. [Structure] When the low speed detection means 11 detects that the speed of the vehicle is equal to or lower than a predetermined speed, the power supply control means Tr2 stops the power supply to the drive circuits 1 to 3.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a tachograph that records the operating state of a vehicle, and particularly to a tachograph power supply circuit that supplies a DC power source to a drive circuit that drives a DC motor that is a drive source for recording the vehicle speed based on a speed signal. It is a thing.

[0002]

[Prior art]

 Conventionally, as this kind of tachograph power supply circuit, one shown in FIG. 5 is known. In the figure, 1 is an input circuit for inputting a speed pulse whose frequency changes according to the traveling speed of the vehicle. This input circuit 1 converts the input speed pulse and outputs a frequency corresponding to the frequency of the input speed pulse. Output a signal. Reference numeral 2 denotes an fV conversion circuit that converts an input frequency signal into a voltage having a magnitude corresponding to the frequency. The fV conversion circuit 2 responds to the frequency of the frequency signal from the input circuit 1, that is, the speed. Output a voltage of magnitude.

Reference numeral 3 denotes a differential amplifier that inputs the voltage output from the fV conversion circuit 2 as a reference voltage to one input and outputs a difference voltage between this voltage and the voltage input to the other input. The voltage output from the differential amplifier 3 is applied to the direct current (DC) motor 4. The DC motor 4 is a drive source that drives a recording needle (not shown). The DC motor 4 is normally or reversely rotated according to the polarity of the voltage applied to it, and is stopped when the input voltage becomes zero. Reference numeral 5 is a potentiometer connected to the output rotary shaft of the DC motor 4, and the potentiometer 5 has its resistance value changed according to the position of the recording needle driven by the DC motor 4 to reach the position of the recording needle. Generates a voltage of a corresponding magnitude. Therefore, the differential amplifier 3, the DC motor 4, and the potentiometer 5 form a servo circuit.

The input circuit 1, the fV conversion circuit 2 and the differential amplifier 3 described above constitute a drive circuit for driving a DC motor 4 which is a drive source for a tachograph, and a collector is shown in this drive circuit. Not connected to the battery, and the emitter is supplied with power via the NPN transistor Tr1 connected to them. The transistor Tr1 constitutes a constant voltage circuit together with the Zener diode ZD connected between its base and the ground. This constant voltage circuit is driven by biasing the base of the transistor Tr1 by the Zener voltage of the Zener diode ZD. Supply a constant voltage to the circuit.

The Zener diode ZD has its cathode connected to the collector of the transistor Tr1 via the NPN transistor Tr2 and the resistor R1. When the transistor Tr2 is turned on, a Zener voltage is generated to turn on the transistor Tr1. . The transistor Tr2 is turned on when an ACC (accessory) power supply is applied to its base through the delay circuit 6 and the ignition switch is in the ACC position and the AC power supply is on. The delay circuit 6 sets the transistor Tr2 so as to continue supplying power until the DC motor 4 returns to the 0 position when the DC switch 4 has not returned to the 0 position when the ignition switch is turned off from ACC. It is for turning on, and this can be done by using the discharging time of the charged charge of the capacitor, for example.

[0006]

[Problems to be solved by the device]

 Since the above-mentioned conventional power supply circuit controls the power supply to the drive circuit by turning on / off the ACC power supply, while the ACC power supply is on, the power is supplied to various places regardless of the running condition of the vehicle. Power will be supplied. For this reason, when the vehicle is stopped in the idling state, for example, the DC motor 4 is in the 0 position and the drive circuit does not need to work, but the drive circuit is supplied with power and is There is a problem that the battery power is wasted.

Further, in the conventional power supply circuit, since the power supply to the drive circuit is controlled by turning the ACC power supply on and off, noise when the ACC power supply is turned on and off affects the drive circuit, and When the starter is started up, power is already supplied to the drive circuit, so there is a problem that the drive circuit picks up noise at the time of engine start and malfunctions.

Therefore, in view of the above-mentioned conventional problems, the present invention provides a tachograph power supply circuit which eliminates the waste of battery power supply and is not affected by the noise generated by the on / off operation of the ignition switch. It is an object.

[0009]

[Means for Solving the Problems]

 In order to achieve the above object, the tachograph power supply circuit according to the present invention is a tachograph power supply circuit for supplying battery power to a drive circuit for driving a DC motor as a drive source for recording according to vehicle speed. A low speed detecting means for detecting that the speed of the vehicle is lower than or equal to a predetermined speed, and a power supply control means for stopping the power supply to the drive circuit in response to the speed detected by the low speed detecting means being lower than or equal to the predetermined speed. It is characterized by having.

[0010]

[Action]

 With the above configuration, when the vehicle speed falls below the predetermined speed and it can be judged that the vehicle is stopped, the low speed detection means detects this and the power supply control means responds to the detection by the power supply to the DC motor. Since the power supply is stopped, battery power is not consumed when the vehicle is stopped, and since the drive circuit is not working when the ignition switch is operated or the engine is started, it is possible to avoid malfunctioning due to noise generated at that time. To be done.

[0011]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a power supply circuit for a tachograph according to the present invention. In FIG. 1, the same parts as those in the conventional circuit described above with reference to FIG. Is omitted.

In the power supply circuit of FIG. 1, a low speed detection circuit 11 for detecting a speed equal to or lower than a predetermined speed of, for example, 5 km / h based on the frequency signal output from the input circuit 1, and the low speed detection circuit 11 A constant voltage circuit 12 that constantly supplies a constant voltage is added to the circuit 1, and the output of the low speed detection circuit 11 turns on / off the transistor Tr2, that is, the on / off state of the constant voltage circuit including the transistor Tr1 and the Zener diode ZD. Control off.

In the above configuration, when the vehicle is running and a speed pulse is input to the input circuit 1, a frequency signal having a frequency corresponding to the speed is output to the output. When the speed of the vehicle is less than or equal to the constant speed, the output of the low speed detection circuit 11 becomes L level, and the transistor Tr2 is held in the off state. At the H level, the transistor Tr2 is turned on and a constant voltage is supplied to the fV conversion circuit 2 and the differential amplifier 3.

FIG. 2 shows a specific circuit example of the low speed detection circuit 11. In FIG. 2, reference numeral 111 denotes a retriggerable monostable multivibrator, to which the frequency signal from the input circuit 1 is applied. Then, the signal is triggered by the rise of the signal from the L level to the H level, a pulse for holding the H level for a predetermined time is generated at the Q output, and a pulse having a phase opposite to that of the Q output is generated at the inverted Q output. When the trigger is retried before the end of the predetermined time, a pulse that lasts the predetermined time is generated from the trigger time.

The duration of the pulse generated by the retriggerable monostable multivibrator 111 depends on the time constant RC defined by the resistor R11 and the capacitor C11 that are inserted in series with the power supply V _CC. Become.

Reference numeral 112 denotes a D-type flip-flop, whose D (delay) input directly receives the Q output of the above-mentioned single-stable multivibrator 111, and C (clock) input the frequency signal from the input circuit 1. Are directly supplied to the R (reset) input, and the inverted Q output is supplied to each of them via the integrating circuit 113 composed of the resistors R12 and R13 and the capacitor C12. The Q output becomes H level according to the input.

Details of the operation of the low speed detection circuit 11 will be described below with reference to the timing charts of FIGS. 3 and 4. At low speed, the monostable multivibrator 111 is supplied with a frequency signal having a long cycle as shown in FIG. 3 (a) at its input, and is triggered by the rise of each pulse to generate its Q output and inverted Q output. Invert as shown in FIGS. 3 (b) and 3 (c).

This frequency signal is also supplied as a clock pulse to the C input of the D-type flip-flop 112, and its R input is obtained by multiplying the inverted Q output by the integrating circuit 113 as shown in (d). Since the voltage is supplied and the D-type flip-flop 112 is in the reset state as shown in (e) at the rising timing of the pulse of the frequency signal, the state of the Q output is not captured in the D-type flip-flop 112. , (F), its Q output remains L level, and the transistor Tr2 as the power supply control means in FIG. 1 is kept in the off state. Note that Th is the threshold level of the R input.

On the other hand, at high speed, the monostable multivibrator 111 is supplied with a frequency signal having a short period as shown in FIG. 4A at its input and is triggered one after another by the rise of each pulse. The Q output and the inverted Q output do not change and are held at the H level and the L level, respectively, as shown in FIGS. 4 (b) and 4 (c). Therefore, the R input of the D-type flip-flop 112 is held at the L level as shown in (d), and therefore its Q output is held at the H level as shown in (f), and the power supply control of FIG. The transistor Tr2 as a means is kept in the ON state.

[0020]

[Effect of device]

 As described above, according to the present invention, when the vehicle is stopped or the speed is low enough to determine that the vehicle is stopped, the power supply to the drive circuit is stopped, so that the battery power is not wasted, and A tachograph power supply circuit that is not affected by the noise generated by turning on / off the ignition switch can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a tachograph power supply circuit according to the present invention.

FIG. 2 is a circuit diagram showing a specific circuit example of a low speed detection circuit in FIG.

FIG. 3 is a time chart for explaining the operation of the low speed detection circuit of FIG. 2 when traveling at low speed.

FIG. 4 is a time chart for explaining the operation of the low speed detection circuit of FIG. 2 when traveling at high speed.

FIG. 5 is a circuit diagram showing an example of a conventional tachograph power supply circuit.

[Explanation of symbols]

 1 Input Circuit (Drive Circuit) 2 f-V Converter Circuit (Drive Circuit) 3 Differential Amplifier (Drive Circuit) 4 DC Motor 11 Low Speed Detection Circuit (Low Speed Detection Means) Tr2 Transistor (Power Supply Control Means)

Claims (1)

[Scope of utility model registration request] 1. A tachograph power supply circuit for supplying battery power to a drive circuit for driving a DC motor as a drive source for performing recording according to a vehicle speed, and detecting that the speed of the vehicle is below a predetermined speed. A tachograph power supply circuit comprising: a low speed detection means; and a power supply control means for stopping power supply to the drive circuit in response to detection of a speed equal to or lower than a predetermined speed by the low speed detection means.