JPH0650273Y2 - Brake oil level alarm indicator lamp drive circuit - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a brake oil level alarm indicator lamp drive circuit for driving an alarm indicator lamp that lights up and issues an alarm when the brake oil level drops. .

[Conventional technology]

Conventionally, as a drive circuit of this type, there is one having a configuration shown in FIG. In the figure, reference numeral 1 is a brake oil level detecting section as a brake oil level detecting means, a ring-shaped float 1b floating on oil is provided around the reed switch 1a, and the reed switch 1a is turned on at the inner periphery thereof.・ Magnet 1c to turn off is attached. Further, a key switch SW, an alarm display lamp 2 and a resistor R are connected in series between the battery V _B and the detection unit 1.

In such a configuration, when the key switch SW is turned on and the brake oil has an appropriate amount, the reed switch
Since 1a is open, the indicator lamp 2 does not light up. On the other hand, if the brake oil is below the appropriate value,
The float 1b also descends as the oil level decreases, and the magnet 1c closes the reed switch 1a. Therefore, current is supplied from the battery V _B to the indicator lamp 2,
The warning display lamp 2 is turned on to warn that the level of the brake oil has dropped.

[Problems to be solved by the invention]

Since the conventional drive circuit is configured as described above, the drive circuit will not operate if the wire harness connecting the brake oil level detection unit 1 to the indicator lamp 2 is broken or the connector provided at the end of the wire harness has poor contact. Even if the brake oil does not work normally and the level of the brake oil decreases, the alarm display lamp 2 cannot be turned on to give an alarm, and there is a problem that the safety in brake operation is not sufficient.

Therefore, in view of the above-mentioned conventional problems, the present invention improves the safety of brake operation by making it possible to warn of an abnormal state such as a wire harness disconnection of an alarm display lamp for alarming a decrease in the level of brake oil. It is an object of the present invention to provide an indicator lamp drive circuit for a brake oil level alarm which is intended.

[Means for solving problems]

In order to achieve the above-mentioned object, the indicator lamp drive circuit for the brake oil level alarm made according to the present invention has one end that is closed when the brake oil drops below a predetermined level.
Brake oil level detecting means having a reed switch connected to D and a first resistor connected in parallel with the reed switch, an alarm display lamp for displaying an alarm by lighting, and driving the alarm display lamp A drive circuit and a wire harness having one end connected to the other end of the reed switch of the brake oil level detecting means,
The drive circuit is configured to detect the brake oil level by means of a second resistor connected between the other end of the wire harness and a power supply and a voltage at a connection point between the second resistor and the wire harness. And a second detecting means for detecting a disconnection of the wire harness, the alarm being detected by the first and second detecting means. It is characterized by turning on the display lamp for use.

[Action]

In the above configuration, the brake oil level detecting means has a reed switch whose one end is closed to ground when the brake oil drops below a predetermined level and a first resistor connected in parallel with the reed switch. The drive circuit has a second resistor connected between the power supply and the other end of the wire harness, one end of which is connected to the other end of the reed switch of the brake oil level detecting means. Therefore, when the wire harness is normal, the voltage between the second resistor and the connection point between the wire harness and the reed switch closes to the GND potential due to the decrease in the brake oil level, and the brake oil level decreases. If the reed switch is open without a switch, the voltage will be a divided voltage between both resistors, and if the wire harness is broken, the voltage will be approximately the power supply voltage.

Therefore, the first detection means detects the decrease of the oil level by the brake oil level detection means below the predetermined value by the voltage between the second resistance of the drive circuit and the connection point of the wire harness, and the second detection means. Detects wire breakage in the wire harness and turns on the alarm display lamp by these detections.Check whether the oil level has dropped below a specified value by turning on the alarm display lamp. If it is normal, it can notify that the wire harness is broken.

In any case, it is possible to ensure safety because it is inspected whether the oil level has dropped below a predetermined value due to the lighting of the alarm display lamp.

[Example of device]

 Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 is a brake oil level detecting section as a brake oil level detecting means, and a resistance _RL as a first resistance is connected in parallel with a reed switch 1a whose one end is connected to ground. . Further, 3 is a drive circuit that drives the alarm display lamp 2, and 4 is a wire harness that connects the drive circuit 3 and the detection unit 1.

The drive circuit 3 has a transistor TR ₄ whose collector is connected to the lamp 2 and a collector which is connected to the base of the transistor TR _{4, and} whose base is connected to one end of the wire harness 4 via the resistor R ₃ and the diode D _1. PNP transistor T
PNP transistor TR ₃ whose collector is connected to the base of R ₁ and transistor TR ₄ via resistor R _{10, and} whose collector is connected to the base of this transistor TR ₃ via resistor R _{9 and} whose base is resistor R ₅ , A NPN transistor TR ₂ connected to one end of the wire harness 4 via a diode D ₂ . Further, resistors R ₂ and R ₄ are connected between the emitter of the transistor TR ₁ and the battery V _B and GND which is a reference potential, and a resistor R ₇ is connected between the emitter of the transistor TR ₂ and battery V _B and GND which is a reference potential. And R ₈ are each connected. The other end of the wire harness 4, one end of which is connected to the other end of the reed switch 1a of the brake oil level detection unit 1, is connected to a battery V _B as a power source via a resistor R ₁ as a second resistor. Has been done.

In such a configuration, when the brake oil level is normal, the reed switch 1a of the detection unit 1 is open, and if the specific resistance of the wire harness 4 is ΔR, (R _L + ΔR) is supplied as the input resistance of the drive circuit 3. It Also, when the brake fluid drops below the appropriate level, the reed switch
When 1a is closed, the specific resistance ΔR becomes the input resistance, and the wire harness 4 becomes disconnected or has poor contact, a substantially infinitely large resistance of 10 ⁶ Ω or more is input.

Here, as shown in FIG. 2, the brake is in a normal state when the input resistance is in the range of R _A to R _B , and the failure lamp 2 is turned off by the drive circuit 3. Further, when the input resistance decreases due to the decrease of the brake oil or the increase due to the disconnection of the wire harness, the drive circuit 3 detects the abnormal state and lights the alarm display lamp 2.

In the normal state, since the reed switch 1a is open and the wire harness 4 is connected, the input resistance is (R _L + Δ
R), and the PNP transistor TR ₁ and the NPN transistor TR ₂ are both turned off due to the voltage drop. Therefore, the transistors TR ₃ and TR ₄ are also off, and the alarm display lamp 2
Is off.

When the reed switch 1a is closed, the input resistance becomes approximately ΔR, and this voltage drop causes the input bias V _a of the drive circuit 3 to be V _a ≤V _b -V _D1 -V _R3 -V _BE1. Then, the PNP transistor TR ₁ turns on and the transistor
The TR ₄ is turned on and is turned on by supplying a current to the alarm display lamp 2. Therefore, transistor TR ₁ and resistor R
₂ to R _4, such as a diode D ₁ is, the voltage between the connection point between the resistor R ₁ and the wire harness 4, first detecting means for detecting a drop below a predetermined value of the oil level by the brake oil level detection section 1 Are configured.

Further, when the input resistance becomes large due to the abnormality of the wire harness 4, the bias V _a becomes V _a ≧ V _c + V _D2 + V _R5 + V _BE2 due to this voltage drop. Then, the transistors TR ₂ and TR ₃ are turned on, the transistor TR ₄ is turned on, and the lamp 2 is turned on.

From the above, when the input resistance shifts above and below the normal range, this voltage drop causes the drive circuit 3 to operate and turn on the alarm display lamp 2. Therefore, the transistor
TR _2, resistors R _5, R ₇ and R _8, such as a diode D ₂ is the resistor R ₁ and the voltage of the connection point of the wire harness 4, the second to detect the contact failure of the disconnection or the connector of the wire harness 4 Of the detection means.

The diodes D ₁ and D ₂ are provided to prevent backflow.

[Effect of device]

As described above, according to the present invention, by detecting the disconnection of the wire harness and the decrease of the brake oil level,
Since the alarm display lamp is lit to display the alarm, the brake oil level can be reliably checked, and it is possible to prevent the brake oil level from decreasing and the safety of the brake operation being impaired. At the same time, the result of inspection of the brake oil level can inform the possibility of wire harness breakage.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment according to the present invention, FIG. 2 is a diagram showing a lighting characteristic of an alarm display lamp with respect to an input resistance of the circuit shown in FIG. 1, and FIG. 3 is a circuit showing a conventional lamp driving circuit. It is a figure. 1 ... Brake oil level detection unit (brake oil level detection means), 2 ... Alarm display lamp, 3 ... Driving circuit, 4 ... Wire harness, TR ₁ , TR ₂ ...... Transistor, _RL ...... Resistance (First resistance), R ₁ ... resistance (second resistance), R _{2 to} R ₅ , R ₇ , R ₈ ... resistance, V _B ... battery (power supply).

Claims (1)

[Scope of utility model registration request] 1. A brake oil level detecting means having a reed switch, one end of which is closed when the brake oil drops below a predetermined level, is connected to GND, and a first resistor connected in parallel with the reed switch. An alarm display lamp for displaying an alarm by lighting, a drive circuit for driving the alarm display lamp, and a wire harness having one end connected to the other end of the reed switch of the brake oil level detecting means, The drive circuit is configured to detect the brake oil level by the second resistor connected between the other end of the wire harness and the power source and the voltage at the connection point between the second resistor and the wire harness. It has first detecting means for detecting a decrease in oil level below a predetermined value, and second detecting means for detecting disconnection of the wire harness. The brake lamp level warning indicator lamp drive circuit is characterized in that the warning indicator lamp is turned on by the detection by the first and second detecting means.