JPH05137234A - Power supply voltage monitor for load - Google Patents

Abstract

PURPOSE:To realize correct monitoring of voltage to be applied on a load by a constitution wherein a voltage converting means converts the voltage between a switching means and the load into an input level at the A/D conversion input port of a microcomputor and inputs thus converted input level to the input port. CONSTITUTION:Resistances of resistors R1, R2 are set such that the potential at a voltage dividing point 53 will be lower than the reference voltage Vcc of A/D conversion even for the maximum collector voltage of a transistor 52. A microcomputor 51 monitors an A/D conversion input port A/D when the transistor 52 is interrupted. If the input value is lower than a predetermined level during that interval, a warning lamp 27 is lighted to prohibit anti-lock control. In other words, the microcomputor 51 can know the potential variation at the voltage dividing point 53 by inputting the voltage at the voltage dividing point 53 to the A/D conversion input port A/D.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load power supply voltage monitoring device preferably used in a so-called antilock brake system for preventing wheels from becoming locked.

[0002]

2. Description of the Related Art When a brake is suddenly applied on a wet road surface or a snowy road, the wheels stop rotating and reach a locked state. When the wheels are locked in this manner, not only the braking distance increases, but also the lateral grip force of the tire (hereinafter referred to as "cornering force") is lost and steering becomes impossible, resulting in an extremely dangerous condition. Become. In addition, the loss of cornering force can cause the vehicle to become unstable, causing it to sway and spin.

Therefore, conventionally, in order to prevent the wheels from being locked even when the brake pedal is strongly depressed to perform a sudden braking operation, a so-called anti-lock
A brake system (hereinafter referred to as "ABS") is installed in a vehicle and used. The ABS detects the vehicle speed, which is the actual speed of the vehicle, and the wheel speed, which is the speed of the vehicle corresponding to the rotation of the wheels, and the slip ratio defined by the following equation (1) is The brake pressure of each wheel is controlled so as to approach the control target value.

[0004]

[Equation 1]

That is, the coefficient of friction between the tire and the road surface becomes maximum not when the slip ratio is 100% (completely locked state where the wheel speed is 0), but when the slip ratio is 2.
It is known to be around 0%. On the other hand, the cornering force decreases as the slip ratio increases,
It becomes 0 at 100%. Therefore, in the ABS, the brake pressure is controlled at the time of the sudden braking operation so that the slip ratio is about 20% so that the friction coefficient between the tire and the road surface becomes maximum.

[0006] By such anti-lock control, ideal braking can be realized while the braking distance is minimized and the stability and steerability of the vehicle are secured regardless of the driving technique of the driver. The control of the brake pressure is performed by controlling the hydraulic pressure from the master cylinder connected to the brake pedal with the hydraulic unit. The hydraulic unit is provided with solenoid valves corresponding to the front and rear wheels, and these solenoid valves are used for the control unit (EC
Driven by U), the hydraulic pressure transmitted to the brake of each wheel is controlled.

Electric power is supplied from the battery to the solenoid valve, but if the voltage applied to the solenoid valve is lowered due to a drop in battery voltage or the like, the solenoid valve cannot be driven well.
As a result, the control of the brake pressure of each wheel becomes poor, and it is dangerous to perform the antilock control in such a state. Therefore, conventionally, the voltage applied to the solenoid valve is monitored, and when a decrease in the applied voltage is detected, the antilock control is stopped and the warning lamp provided on the instrument panel is turned on to turn on the ABS. The driver is notified that the vehicle is in an inoperative state.

The prior art for monitoring the applied voltage to the solenoid valve is shown in FIG. The battery voltage V _B from the battery 1 mounted on the vehicle is passed through the harness as the ignition voltage V _IG to the control unit (EC
U) 2 and the stabilized power supply circuit 3 supplies the power supply voltage Vcc (5
V) is created. The voltage V _IG is also _supplied to the power supply voltage monitoring circuit 5. The power supply voltage monitoring circuit 5 gives a predetermined detection output to the microcomputer 4 when detecting that the voltage V _IG has become lower than a predetermined voltage (for example, 10 V).

The battery voltage V _B is also applied to the above warning lamp 6 for informing the driver that the ABS is inactive, and also via line 7 a solenoid valve in the hydraulic unit. 8 is also being supplied. An output transistor 10 for driving the solenoid valve 8 is connected to the microcomputer 4. The collector voltage of the transistor 10 is the resistance 11,
The voltage is divided by 12 and the voltage at the voltage dividing point 13 is connected to the input port P of the microcomputer 4. The microcomputer 4 monitors the drive state of the solenoid valve 8 by monitoring the signal from the input port P.

When the voltage V _IG becomes less than the predetermined voltage in the power supply voltage monitoring circuit 5, a signal indicating this is given from the power supply voltage monitoring circuit 5 to the microcomputer 4. In response to this, the microcomputer 4 turns on the warning lamp 6 and at the same time prohibits the antilock control. As a result, when the battery voltage V _B is lowered to such an extent that the solenoid valve 8 may be driven poorly, the antilock control is prohibited, so that it is possible to prevent a malfunction in the braking operation.

However, in this prior art, the voltage applied to the solenoid valve 8 is not directly detected, but only the ignition voltage V _IG is detected. That is, what is applied to the solenoid valve 8 is the voltage that has passed through the line 7, and this line 7 is composed of a harness, but since this harness is different from the harness that supplies the ignition voltage V _IG , The voltage V _IG monitored by the power supply voltage monitoring circuit 5 may be different from the voltage applied to the solenoid valve 8. Therefore, in the above-described prior art in which the voltage applied to the solenoid valve 8 cannot be accurately monitored, there is a possibility that the antilock control cannot be reliably prohibited when the voltage applied to the solenoid valve 8 decreases. is there.

Another prior art arrangement for solving this deficiency is shown in FIG. 4, parts corresponding to the respective parts shown in FIG. 3 are designated by the same reference numerals. In this prior art, the voltage applied to the solenoid valve 8 is directly detected by monitoring the voltage at the line 7 side terminal of the solenoid valve 8.
That is, the voltage applied to the solenoid valve 8 is input from the line 15 to the base of the transistor 17 via the resistor 16. Then, the collector voltage of the transistor 17 is input to the microcomputer 4 via the line 18.

With this configuration, when the voltage applied to the solenoid valve 8 is high, the transistor 17 is in a conductive state, and a low level signal is input to the microcomputer 4 from the line 18. When the voltage applied to the solenoid valve 8 drops, the transistor 17
Is cut off, a high level signal is output to the line 18, and the decrease in the applied voltage is detected by the microcomputer 4. The subsequent operation is the same as in the case of the above-mentioned first prior art.

[0014]

However, in the second prior art, since a new wiring corresponding to the line 15 is required, there is a problem that the structure is complicated and the cost is increased. is there. Therefore, an object of the present invention is to solve the above-mentioned technical problems and to provide a load power supply voltage monitoring device capable of monitoring an accurate applied voltage to a load with a simple configuration.

[0015]

According to a first aspect of the present invention, there is provided a load power supply voltage monitoring device which is connected in series to a circuit of a power supply and a load, and which supplies power to the load from the power supply. And a microcomputer having an analog / digital conversion input port for controlling conduction / interruption of the switching means, and a voltage between the switching means and a load, the analog / digital conversion input port And a means for inputting the voltage converted by the voltage converting means to an analog / digital conversion input port of the microcomputer, the microcomputer including the switching means. The analog / digital conversion input during the period when the Based on the input voltage of the port,
The present invention is characterized by determining whether or not the applied voltage to the load is normal.

According to the above arrangement, the voltage between the switching means and the load is converted into the input level of the analog / digital conversion input port of the microcomputer by the voltage converting means, and is input to this input port. Therefore, the input voltage to the analog / digital conversion input port when the switching means is in the cutoff state corresponds to the voltage applied to the load. The microcomputer determines whether or not the voltage applied to the load is normal, based on the input voltage when the switching means is in the cutoff state.

In this configuration, since the voltage between the switching means and the load is monitored, it is possible to directly monitor the voltage applied to the load instead of the power supply voltage. Further, as the voltage converting means, for example, an existing voltage dividing circuit for monitoring the driving state of the load can be used as it is, so that the circuit can be configured without using an extra circuit or wiring.

When a plurality of circuits of the load and the switching means are connected in parallel to the power source, the voltage converting means is provided corresponding to each load, and each load is used as the microcomputer. In this microcomputer, the maximum value of the input voltage of the analog / digital conversion input port in the period in which the switching means is in the cutoff state is applied. Based on the above, it may be determined whether or not the voltage applied to the load is normal.

Further, the judgment regarding the voltage applied to the load to the microcomputer may be made based on the average value of the input voltage of the analog / digital conversion input port during the period when the switching means is in the cutoff state. Further, it is preferable that the microcomputer does not judge the applied voltage to the load during a period immediately after the switching means is cut off.

With this configuration, when the load is an inductance such as a coil, the influence of the back electromotive force due to the interruption of the switching means can be eliminated.

[0021]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 2 is a conceptual diagram showing an outline of an antilock brake system (hereinafter referred to as “ABS”) to which a load power supply voltage monitoring device according to an embodiment of the present invention is applied. ABS is a wheel speed sensor 2 provided on each wheel.
This is a device that electronically controls the brake pressure of the brake 22 of each wheel based on the output of 1 to avoid the locked state of the wheel at the time of a sudden braking operation and realizes an optimum slip ratio. That is, when the brake pedal 23 is strongly depressed, the hydraulic pressure from the master cylinder 24 is controlled by the hydraulic unit 25 and is transmitted to the brake 22 of each wheel. This hydraulic unit 25 is provided with four channels for individually controlling the hydraulic pressure for each wheel, and at least one solenoid valve for controlling the hydraulic pressure is provided corresponding to each channel. Has been. This solenoid valve drive control is performed by a control unit (ECU) 26 that monitors the output of the wheel speed sensor 21. The reference numeral 27 is a warning lamp for notifying the driver of the possibility that the control thereof may become defective due to the reduction of the voltage applied to the solenoid valve and therefore the antilock control is prohibited.

FIG. 1 is a block diagram showing the electrical construction related to the driving of the solenoid valve. Electric power from a battery 31 (for example, a rated output voltage of 12V) is supplied to the control unit 26 via an ignition switch 32, and a relay of a relay 34 that controls power supply to a solenoid valve 33 in the hydraulic unit 25. It is provided to the coil 34b. Relay 34 switches the electric power from battery 31 given from line 35 to line 36. Further, the electric power via the ignition switch 32 is given to the warning lamp 27.

Further, the electric power from the battery 31 is supplied to the motor 40 in the hydraulic unit 25 from the line 35 through the contact 39a of the relay 39. The motor 40 drives a pump (not shown) for returning the excess liquid generated in the hydraulic unit 25 to the master cylinder 24 for controlling the hydraulic pressure. The relay coil 39b of the relay 39 is supplied with power from the battery 31 via the contact 34a of the relay 34.

Reference numeral 41 is a stop lamp which is turned on by being supplied with electric power through a switch 42 which is turned on by operating the brake pedal 23. The operation state of the brake pedal 23 is monitored by the control unit 26 via the line 43. The warning lamp 27 is turned on when the control unit 26 grounds the line 44. When the contact 34a of the relay 34 is connected to the ground side, a current flows from the line 45 through the diode 46, and the warning lamp is turned on at this time as well. The control unit 26 includes the ignition switch 3
In the period immediately after 2 becomes conductive, the relay coil 3
4b is demagnetized, the contact 34a is connected to the ground side, and the warning lamp 27 is turned on. Then, the relay coil 34b is excited. As a result, the solenoid valve 3
3 and the relay coil 39b can be supplied with electric power. Then, when the signal ALT-L indicating this is given when the power generation by the generator (not shown) is started, the warning lamp 27 is turned off.

The control unit 26 has a microcomputer 51 inside and a solenoid valve 33 as a load.
The output transistor 52 is provided as a switching means for driving the. The operating voltage Vcc for the microcomputer 51 is generated by the stabilized power supply circuit 55. The microcomputer 51 turns on / off the transistor 52.
By shutting off, the solenoid valve 33 is excited / demagnetized. The output transistor 52 and the circuit related thereto are provided individually for each solenoid valve 33, but in FIG. 1, only the circuit configuration for one channel is shown, and solenoids corresponding to other channels are shown. Illustration of the circuit configuration related to the valve 33 is omitted.

The collector voltage of the transistor 52 is divided by the resistors R1 and R2 constituting the voltage conversion means, and the potential appearing at the voltage dividing point 53 is given to the analog / digital conversion input port A / D of the microcomputer 51. There is. A Zener diode 54 is connected to the collector of the transistor 52 to prevent an overvoltage from being applied to the analog / digital conversion input port A / D due to the back electromotive force generated in the solenoid valve 33.

The resistors R1 and R2 are arranged so that the potential at the voltage dividing point 53 becomes equal to or lower than the voltage Vcc (for example, 5 V) which is the reference voltage for analog / digital conversion even when the collector voltage of the transistor 52 is maximum. The resistance value is set. The microcomputer 51 monitors the analog / digital conversion input port A / D while the transistor 52 is shut off. Then, when the input value in this period is less than the predetermined value, the warning lamp 27 is turned on and the antilock control is prohibited. The above-mentioned predetermined value is a value corresponding to the voltage (for example, 1V) of the voltage dividing point 53 when the collector voltage of the transistor 52 is, for example, 10V.

When the transistor 52 is cut off, the collector voltage of the transistor 52 becomes the voltage itself applied to the solenoid valve 33. Therefore, by monitoring the collector voltage during the period when the transistor 52 is cut off, the voltage applied to the solenoid valve 33 can be monitored. Since the collector voltage of the transistor 52 has the maximum value during the cutoff period of the transistor 52, the microcomputer 51 eventually has analog / analog
It suffices to monitor the maximum value of the input values from the digital conversion input port A / D.

The microcomputer 51 is provided with analog / digital conversion input ports A / D for four channels corresponding to each solenoid valve 33, and the input value for each channel is monitored. However, in determining whether to prohibit the antilock control, for example, the maximum value of four channels is compared with the above predetermined value, or the average value of the input values of four channels is compared with the above predetermined value. do it.

The microcomputer 51 is an analog /
The input signal from the digital conversion input port A / D is also used for monitoring the drive state of the solenoid valve 33. That is, as long as the voltage dividing circuit including the resistors R1 and R2 is focused on the function of monitoring the driving state of the solenoid valve 33, the voltage dividing circuit including the resistors 11 and 12 shown in FIGS. In the configuration of the present embodiment, the voltage dividing point 5 of this voltage dividing circuit is
Analog / digital conversion of the voltage of 3 Input port A / D
It is characterized in that the change in the potential at the voltage dividing point can be known in detail in the microcomputer 51 by inputting into the.

As described above, in this embodiment, the voltage applied to the solenoid valve 33 is directly monitored by monitoring the voltage between the transistor 52 and the solenoid valve 33 during the cutoff period of the transistor 52. I am trying. Therefore, since the accurate voltage applied to the solenoid valve 33 is monitored, this can be reliably detected when the antilock control may be defective.

Further, as is clear from comparison between FIG. 1 and FIGS. 3 and 4, the existing voltage dividing circuit (resistor R1 in FIG. 1) for dividing the collector voltage of the output transistor 52 is used.
And R2 and, in FIG. 3 or 4, resistors 11 and 12. 4) can be used, there is no need for new wiring unlike the prior art of FIG. In this way, the configuration can be simplified, which in turn can contribute to cost reduction.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the case where the load power supply voltage monitoring apparatus according to the present invention is used for the ABS is taken as an example. However, when it is necessary to directly monitor the voltage applied to the load in addition to the ABS. It can be widely applied to. Further, it goes without saying that it can be applied to any load other than the solenoid. In addition, various design changes can be made without changing the gist of the present invention.

[0034]

As described above, according to the load power supply voltage monitoring apparatus of the present invention, since the voltage between the switching means and the load is monitored, the voltage applied to the load is directly detected. Therefore, the applied voltage can be accurately monitored. Moreover, the voltage conversion means for converting the voltage between the switching means and the load into the input level of the analog / digital conversion input port of the microcomputer is the same as the existing voltage dividing circuit for monitoring the driving state of the load. Since it can also be used, the circuit can be configured without requiring an extra circuit or wiring. As a result, the structure can be simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an antilock brake system to which a load power supply voltage monitoring device according to an embodiment of the present invention is applied.

FIG. 2 is a conceptual diagram showing an outline of an antilock brake system.

FIG. 3 is a block diagram showing an electrical configuration of a prior art.

FIG. 4 is a block diagram showing an electrical configuration of another prior art.

[Explanation of symbols]

 26 Control Unit 31 Battery 33 Solenoid Valve (Load) 51 Microcomputer 52 Output Transistor (Switching Means) 53 Voltage Dividing Point R1 Resistance R2 Resistance

Claims (4)

[Claims] 1. A switching means which is connected in series to a circuit of a power source and a load and which controls power supplied from the power source to the load, and which controls conduction / interruption of the switching means,
A microcomputer having an analog / digital conversion input port, a voltage conversion means for converting a voltage between the switching means and the load into an input level at the analog / digital conversion input port, and a voltage conversion means for converting the voltage. The input voltage of the analog / digital conversion input port of the microcomputer is input to the analog / digital conversion input port of the microcomputer. A load power supply voltage monitoring device, which determines whether or not the voltage applied to the load is normal based on the above. 2. A plurality of circuits of said load and switching means are connected in parallel to a power source, said voltage conversion means is provided corresponding to each load, and said microcomputer comprises each load. In addition to having an analog / digital conversion input port compatible with
It is characterized in that whether or not the voltage applied to the load is normal is determined based on the maximum value of the input voltage of the analog / digital conversion input port during the period when the switching means is in the cutoff state. The load power supply voltage monitoring device according to claim 1. 3. A plurality of circuits of said load and switching means are connected in parallel to a power source, said voltage conversion means is provided corresponding to each load, and said microcomputer comprises each load In addition to having an analog / digital conversion input port compatible with
A method for judging whether or not a voltage applied to the load is normal based on an average value of an input voltage of the analog / digital conversion input port during a period when the switching means is in a cutoff state. Item 2. The load power supply voltage monitoring device according to Item 1. 4. The load according to claim 1, 2 or 3, wherein the microcomputer does not judge a voltage applied to the load during a period immediately after the switching means is cut off. Power supply voltage monitoring device.