JPH0542868A - Fade detecting device of brake - Google Patents

Abstract

PURPOSE:To provide a fade detecting device at a low cost. CONSTITUTION:A fade detecting device includes a signal processing circuit 19 forming the specified pulse wave form according to wheel speed, wheel speed sensor capable of detecting wheel speed by the number of pulses appearing in a pulse wave form, temperature sensor 15 built in this wheel speed sensor and capable of detecting the heat temperature of the brake of a vehicle, and comprises this temperature sensor 15 connected to the signal processing circuit 19. In addition, the fade detecting device is provided with a temperature change detecting circuit which expresses the change in the brake temperature detected by the temperature sensor as the change in the wave form of a pulse wave form.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake fade detecting device, and more particularly to a brake fade detecting device integrally incorporated in a wheel speed sensor.

[0002]

2. Description of the Related Art Generally, when the temperature of a brake pad or a rotor (the temperature of a shoe and a drum in the case of a drum brake) reaches a certain temperature or higher, the brake fades and the effectiveness of the brake deteriorates. It is known. Therefore, conventionally, a technology has been proposed in which a temperature sensor such as a thermocouple or thermistor is embedded in the brake pad, the temperature of the brake pad is detected by this temperature sensor, and the possibility of fade is predicted by this. (JP-A-57-54743).

[0003]

However, according to the conventional technique of this type, since the brake pad is a consumable item, the temperature sensor embedded therein must be discarded each time the brake pad is replaced. It has to be uneconomical. In addition, since the brake pad has a very high temperature due to its structure, it is difficult to draw out the lead wire and the temperature sensor is expensive.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems of the prior art and to provide an economical and economical brake fade detection device.

[0005]

In order to achieve the above object, the present invention has a signal processing circuit for generating a predetermined pulse waveform in accordance with the wheel speed, and determines the wheel speed from the number of pulses appearing in the pulse waveform. A wheel speed sensor that can be detected, a temperature sensor that is built in the wheel speed sensor and that can detect the heating temperature of the brake of the vehicle, and this temperature sensor are connected to a signal processing circuit. In addition, a temperature change detection circuit for causing a change in the temperature of the brake detected by the temperature sensor to appear as a change in the waveform shape of the pulse waveform is provided.

[0006]

According to the present invention, when the brake is heated, the pulse waveform output through the signal processing circuit is output in a state in which the waveform shape is changed from the normal state. The wheel speed can be detected from the number, and the heating state of the brake can be detected from the pulse waveform shape.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a brake fade detection device according to the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a hub to which a tire 3 can be attached, and an inner ring 5a of a hub bearing 5 is fixed to the hub 1. A fixed outer ring 5b is fitted on the outer circumference of the inner ring 5a, and a wheel speed sensor 7 is attached to the outer circumference of the outer ring 5b. The wheel speed sensor 7 is provided with a magnetoelectric conversion element 9 in the detecting portion, and the magnetoelectric conversion element 9 is arranged so as to face the magnetized surface of the pulsar ring 11 fixed to the outer periphery of the inner ring 5a.

A brake 13 is connected to the hub 1, and the brake 13 is composed of a brake pad 13a and a rotor 13b.

Furthermore, according to this embodiment, as shown in FIG. 2, the wheel speed sensor 7 has a built-in temperature sensor 15 including a temperature sensitive element such as a negative characteristic thermistor in addition to the magnetoelectric conversion element 9. The temperature sensor 15 is preferably arranged near the brake 13 so that the heating temperature of the brake 13 can be detected. Reference numeral 17 denotes a substrate made of glass epoxy resin or the like.
A signal processing circuit 19 described later is formed. 21 is a lead wire.

The signal processing circuit 19, as shown in FIG.
After amplifying the pulse waveform from the magnetoelectric conversion element 9 via the amplifier 23 and shaping the waveform via the comparator 25,
The pulse waveform is output as a waveform as shown in FIG. 4A through the switching element 27 composed of a transistor or the like. The switching element 27 is turned on only when a voltage higher than the reference voltage Vref is applied to the non-inverting input terminal of the comparator 25.

According to this embodiment, the signal processing circuit 1
The temperature sensor 15 is connected to the output terminal of 9 as a load element of the switching element 27, and a resistor 29 is connected to the temperature sensor 15 in series. These constitute a temperature change detection circuit for detecting the temperature change of the brake 13.

Next, the operation of this embodiment will be described.

Since the inner ring 5a of the hub bearing 5 rotates during operation of the vehicle, the pulsar ring 11 rotates,
A predetermined pulse waveform corresponding to the wheel speed is output from the magnetoelectric conversion element 9. This pulse waveform, as shown in FIG.
The waveform is shaped while being amplified and sent to the switching element 27.

Here, when the brake 13 is not heated too much, the resistance value of the temperature sensor 15 does not change, so the pulse waveform output through the switching element 27 is as shown in FIG. 4 (a). Appear as a normal waveform. Thus, according to this embodiment, the brake 13
When the temperature is detected, the temperature is detected, and the resistance value of the temperature sensor 15 decreases according to the heating temperature, so that the voltage at the output end increases and the pulse waveform output through the switching element 27. The amplitude of
It appears as a waveform as shown in (b).

According to this, since the pulse waveform whose amplitude is increased as compared with the normal state is output, the wheel speed can be detected from the number of pulses appearing in the pulse waveform, and
The heating state of the brake 13 can be detected from the waveform shape of the pulse waveform, that is, the magnitude of the amplitude of the pulse waveform.
When the vehicle is stopped, there is no output from the magnetoelectric conversion element 9. In this case, the switching element 27 is turned off, so that the current from the DC power supply Vcc is supplied to the temperature sensor 1.
5 and the resistor 29, and the temperature sensor 15 at the output end.
A substantially constant voltage waveform is output according to the resistance value of, that is, according to the heating state of the brake 13.

FIG. 5 shows another embodiment.

In this example, the temperature sensor 15 connected to the output terminal of the signal processing circuit 19 is connected to the inverting input terminal of the comparator 31. Here, the magnetoelectric conversion element 9
The pulse waveform output from the amplifier is amplified by the amplifier 23 and shaped by the comparator 31. At this time, the temperature sensor 15 is responsive to the heating state of the brake 13.
Since the resistance value of the comparator changes, the comparator 3
The voltage VTH applied to the inverting input terminal of 1 changes.

When the voltage VTH is at the threshold value VTHL in the normal state, the waveform as shown in FIG. 6A is output from the output terminal, and when it is at the threshold value VTHH at the high temperature, , A waveform as shown in FIG. 6B is output from the output end.

According to this, when the brake 13 is at a high temperature, a pulse waveform having a larger duty ratio than the normal state is output, so that the wheel speed can be detected from the number of pulses appearing in the pulse waveform and the pulse waveform can be detected. From the waveform shape of the brake 13, that is, the magnitude of the duty ratio
The heating state of can be detected. When the vehicle is stopped, there is no output from the magnetoelectric conversion element 9. In this case, since the current from the DC power supply Vcc flows through the resistors 33 and 35 and the temperature sensor 15, the output terminal has a substantially constant voltage according to the resistance value of the temperature sensor 15, that is, the heating state of the brake 13. The waveform is output.

If the heating state of the brake 13 can be grasped in this way, it is clear that when the temperature exceeds a certain temperature, the brake 13 will fade and its effectiveness will deteriorate. Various measures such as these are taken.

In FIG. 7, four temperature sensors 15 (No1 to No4) are provided in the vicinity of the brake 13, each temperature sensor 15 is connected to the electronic control unit ECU1, and an output terminal of the electronic control unit ECU1 is connected. A switching element 41 that is turned on when the output of the ECU 1 is high and turned off when it is low is connected, and a fade warning lamp 43 and a warning buzzer 45 are connected to the switching element 41.

FIG. 8 is a flowchart of the ECU 1.
First, the number i of the temperature sensor 15 is initialized (S
1), and +1 is incremented (S2). In this state, the No. 1 temperature sensor 15 is targeted, and the temperature data Ti of this sensor is taken in (S3). It is determined whether this temperature data Ti is higher than a predetermined temperature Ts (S4), and if it is lower, the output of the ECU 1 is made low (S5). In this case the switching element 4
1 remains off, and the fade warning lamp 43 and the warning buzzer 45 do not operate.

On the other hand, if the determination result is high, the output of the ECU 1 is made high (S6). In this case, the switching element 41 is turned on and the fade warning lamp 43 and the warning buzzer 45 operate. Next, it is determined whether or not the number of the temperature sensor 15 of interest is 4 or more (S).
7). When the temperature sensor 15 of No. 1 is targeted, the temperature is naturally 4 or less, so that the process proceeds to S2 and +1 is again incremented (S2).
The second temperature sensor 15 is targeted and the same steps as above are repeated. This is repeated until it is judged to be 4 or more in S7, and when it is judged to be 4 or more, the process proceeds to S1 and the series of cycles is ended.

According to this, four temperature sensors 15 (No1 to No4) are provided in the vicinity of the brake 13, the temperature of the brake 13 is monitored at a plurality of locations, and the temperature of the brake 13 rises for the driver. This is detected by light and sound through the fade warning lamp 43 and the warning buzzer 45, so that the fade phenomenon of the brake 13 can be accurately detected.

In FIG. 9, the ECU 2 includes an antilock brake system (ABS), an engine control system,
Speed control system (cruise control), automatic transmission control system (AT)
1 shows an ordinary electronic control unit for an automobile used for the above. Various sensors 51 and various actuators 53 are connected to the ECU 2, and in this example, the electronic control unit ECU 1 having the above configuration is further connected.

FIG. 10 is a flowchart of the ECU 2 for controlling the vehicle speed. First, the output of the ECU 1 is read (S1), and it is determined whether the output is high (brake heating) or low (normal brake) (S2).

If the vehicle speed is high, the current vehicle speed V is read (S3), the speed reduction throttle valve position TP is read (S4), and the vehicle speed V is faster than the set vehicle speed VS and the speed reduction throttle valve position. If TP is higher than the minimum position Tmin, the position TP is moved in the deceleration direction by ΔT (S5). Even if the vehicle speed V is faster than the set vehicle speed VS, if the position TP of the throttle valve for deceleration is at the minimum position Tmin, the throttle valve for deceleration does not move,
Then it shifts to (S1).

If the vehicle speed V is slower than the set vehicle speed VS and the position TP of the deceleration throttle valve is lower than the maximum position Tmax, the position TP is moved by ΔT in the speed increasing direction (S6). Even if the vehicle speed V is slower than the set vehicle speed VS, if the speed reduction throttle valve position TP is at the maximum position Tmax, the speed reduction throttle valve does not move,
Then it shifts to (S1).

If it is low in S2, the position TP of the deceleration throttle valve is read (S4 '), and if the position TP of the deceleration throttle valve is lower than the maximum position Tmax, that position TP is moved in the speed increasing direction by ΔT. At the same time (S6), if the position TP of the deceleration throttle valve is at the maximum position Tmax, the deceleration throttle valve is not moved, and the process proceeds to that state (S1).

FIG. 11 shows the ECU 2 for controlling the ABS.
It is a flowchart of. First, the output of the ECU 1 is read (S1), and it is judged whether the output is high (brake heating) or low (brake normal) (S2).
The operation of the BS is prohibited (S3), and when it is low, the prohibition of the operation of the ABS is released (S4).

FIG. 12 is a flow chart of the ECU 2 when changing the boost amount of the brake booster. First E
Read the output of CU1 (S1) and judge whether the output is high (brake heating) or low (brake normal) (S1)
2) If it is high, the target value of the hydraulic pressure of the brake booster is set to be high at PH (S3), and if it is low, it is set to be low at PL (S4).

FIG. 13 is a flowchart of the ECU 2 when the AT shift schedule is changed. First ECU
1 output is read (S1), it is judged whether the output is high (brake heating) or low (brake normal) (S2),
If it is high, the shift schedule map is changed to a low-speed gear-oriented type (S3), and if it is low, it is changed to a normal type (S4).

According to this, by combining the ECU 2 with the ECU 1, the antilock brake system (A
BS, engine control system, speed control system (cruise control), automatic transmission control system (AT), etc. can be controlled more finely.

Specifically, before the fade occurs, the vehicle speed can be limited, the ABS operation can be prohibited, and the brake load can be reduced, so that an accident can be prevented. It will not fade again, so
The life of the brake pad can be extended. Further, since the boost amount of the brake booster can be automatically increased, even if a fade occurs, it is possible to correct the deterioration of the braking effectiveness to some extent.

[0036]

As is apparent from the above description, according to the present invention, the pulse waveform output from the signal processing circuit is
When the brake is in the heating state, it is output in a state where the waveform shape has changed compared to the normal state, so the wheel speed can be detected from the number of pulses appearing in the pulse waveform and the heating state of the brake from the shape of the pulse waveform. Can be simultaneously detected, and the temperature sensor that detects the heating state of the brake is built in the wheel speed sensor, so it is compact and the cable for the wheel speed sensor can also be used, so the temperature sensor cable is not required. And so on.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an arrangement relationship between a wheel speed sensor and a brake.

FIG. 2 is a vertical sectional view showing a wheel speed sensor.

FIG. 3 is a circuit diagram showing an embodiment of a fade detection device according to the present invention.

4 is a diagram showing a pulse waveform formed by the apparatus of FIG.

FIG. 5 is a circuit diagram showing another embodiment of the fade detection device.

6 is a diagram showing a pulse waveform formed by the apparatus of FIG.

FIG. 7 is a circuit diagram showing a fade warning device.

8 is a flowchart of the ECU 1 of FIG.

FIG. 9 is a circuit diagram in which the ECU 1 of the present invention is combined with the ECU 2 of the automobile.

FIG. 10 is a flowchart of an ECU 2 that controls a vehicle speed.

FIG. 11 is a flowchart of the ECU 2 that controls the ABS.

FIG. 12 is a flowchart of the ECU 2 that changes the brake boost amount.

FIG. 13 is an ECU 2 that changes the AT shift schedule.
It is a flowchart of.

[Explanation of symbols]

 1 Hub 3 Tire 5 Hub Bearing 7 Wheel Speed Sensor 9 Magnetoelectric Conversion Element 11 Pulser Ring 13 Brake 15 Temperature Sensor 19 Signal Processing Circuit 23 Amplifier 25 Comparator 27 Switching Element

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location G01K 13/10 7267-2F

Claims (2)

[Claims] 1. A wheel speed sensor having a signal processing circuit for generating a predetermined pulse waveform according to a wheel speed and capable of detecting the wheel speed from the number of pulses appearing in the pulse waveform, and the wheel speed sensor. A temperature sensor that is built in the vehicle and that is capable of detecting the heating temperature of the brake of the vehicle; and a temperature sensor that is connected to the signal processing circuit and that detects the temperature of the brake detected by the temperature sensor. A temperature change detection circuit that causes a temperature change to appear as a change in the waveform shape of the pulse waveform, and a fade detection device for a brake. 2. The brake fade detection device according to claim 1, wherein a change in the waveform shape of the pulse waveform is captured and compared with a preset waveform shape, and a fade may occur when the two waveforms are different. A fade detecting device for a brake, characterized in that it is provided with a means for making a driver sense that something is present.