JPH0535993B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a battery rise warning device that predicts and warns of engine stalling and engine starting failure of a vehicle based on the state of the battery during engine operation.

(Prior Art) As a conventional battery warning device, there is known, for example, a device intended for electric vehicle batteries as disclosed in Japanese Patent Application Laid-Open No. 49-51540.

In this battery rise warning device, the discharge current of the battery is converted into voltage by a shunt resistor, and the battery voltage detected by the shunt resistor is amplified and then input to a voltage comparator and compared with a predetermined reference voltage. The battery terminal voltage when a discharge current of When the capacity drops below a specified value, an advance warning of battery buildup is issued.

(Problem to be Solved by the Invention) However, in such a conventional battery rise warning device, the battery charge/discharge current is passed through a shunt resistor to convert the current into voltage for detection. Because of this, it is inevitable that the shunt resistance will cause a drop in battery voltage and power loss, impairing the battery capacity.
In addition, when trying to reduce the negative effects by reducing the value of the shunt resistor, the detection voltage becomes smaller and a high-performance amplifier with a high amplification factor is required, resulting in a general problem in terms of reliability and cost. There were problems with the device used in vehicles.

(Means for Solving the Problems) The present invention has been made in view of such conventional problems, and it is possible to prevent engine stalling and engine starting with a simple configuration without requiring a shunt resistor for detecting discharge current. To provide a battery rise warning device which determines that the battery capacity has reached an impossible level and issues a warning in advance.

In order to achieve this object, the present invention detects the battery terminal voltage with a battery terminal voltage detection means while the engine is operating, and detects when the battery voltage decreases as the battery capacity decreases and continues for a certain period of time to determine the discharge state. The voltage determining means determines the state in which the detected voltage is below a first reference voltage value that is lower than a predetermined battery voltage, and when this determination output is obtained, a predetermined in-vehicle electrical load is detected. is connected to the battery by the switch means, and when a new load is connected by the switch means, the drop in battery terminal voltage is detected by the voltage drop detection means, and this voltage drop is determined as a predetermined second reference voltage. When the above occurs, the abnormality determining means determines that the engine has stalled or the battery capacity has decreased to such a level that the engine cannot be used, and the warning display means issues an advance warning of the battery rising.

(Function) According to the configuration of the present invention, when the battery terminal voltage continuously drops below the first reference voltage for a certain period of time, a predetermined in-vehicle electrical load is connected to the battery to reduce the battery terminal voltage. The lower the battery capacity, the greater the voltage drop when a new load is connected, so if the magnitude of this voltage drop exceeds the second reference voltage, engine stall may occur. If the engine continues to stop, it will be determined that the battery capacity is insufficient to restart the engine, and an advance warning will be issued.

In addition, since the decrease in battery capacity is determined only from the battery terminal voltage, there is no need for a shunt resistor to convert the battery charge/discharge current into a voltage signal, and battery voltage drop and power loss occur when a shunt resistor is connected. There are no problems and reliability is guaranteed when applied to general automobiles.
Furthermore, the cost can be reduced.

(Embodiment) FIG. 1 is a circuit block diagram showing an embodiment of the present invention.

First, to explain the configuration, 1 is a battery, which is charged by the alternator 2 while the engine is running, and the battery 1 is connected to switches 3a to 3a.
A plurality of on-vehicle electrical loads 4a to 4n are connected via 3n.

The terminal voltage Vb of the battery 1 is inputted to a voltage detection circuit 5 consisting of a waveform shaping circuit, etc.
Battery terminal voltage detected by voltage detection circuit 5
Vb is input to one side of the comparator circuit 6. The other side of the comparator circuit 6 is given a predetermined first reference voltage Vr from the first reference voltage circuit 7, and the comparator circuit 6 receives the battery terminal voltage from the voltage detection circuit 5.
A comparison output is generated when Vb becomes less than the first reference voltage _Vr1 . The output of the comparison circuit 6 is given to a discharge state determination circuit 8, and the discharge state determination circuit 8 includes a time constant circuit or a monostable multivibrator that generates an output when the output of the comparison circuit 6 continues for a certain period of time or more. It is provided. Therefore, if the battery terminal voltage Vb detected by the voltage detection circuit 5 by the comparator circuit 6, the first reference voltage circuit 7, and the discharge state determination circuit 8 continues for a certain period of time or more, it meets the predetermined first standard. It constitutes a voltage discrimination means that produces a discrimination output when the voltage Vr drops below ₁ .

The output of the discharge state determination circuit 8 is given as a switch control signal to a switch circuit 9. A predetermined electric load 10 is connected to this switch circuit 9, and in response to the output of the discharge state determination circuit 8, a switch is activated. The switch contact of the circuit 9 is closed, and a predetermined on-vehicle electrical load 10 is connected to the battery 1. As this on-vehicle electrical load 10, for example, a rear differential gear heater is used, and the on-vehicle electrical load 1
Rear differential heater as 0 is battery 1
When connected to the resistor, the discharge current of the battery 1 is increased by a predetermined current Δi determined by the resistance value. As the on-vehicle electrical load 10, in addition to the rear defogger heater, it is possible to use an appropriate on-vehicle electrical load that consumes a current of 5 A or more constantly regardless of the operating state.
Furthermore, as for the on-vehicle electrical load 10 connected to the battery 1 by the switch circuit 9, the battery discharge current does not increase even if the switch circuit 9 closes the switch contact when the selected load is in the operating state. It is desirable to connect the on-vehicle electrical loads to the switch circuit 9 and temporarily increase the battery discharge current by connecting the other loads that are not in use to the battery 1 even if any one of the on-vehicle loads is in use. .

On the other hand, the output of the voltage detection circuit 5 is
1, the voltage holding circuit 11 receives the switch output of the switch circuit 9, and the voltage holding circuit 11 receives the switch output of the switch circuit 9.
The battery terminal voltage Vb immediately before the switch contact is closed is held and output. The voltage holding circuit 11 for this purpose is a so-called sample hold circuit that inputs the detection output of the voltage detection circuit 5 to a capacitor via an analog switch and outputs the terminal voltage of the capacitor via a high input impedance amplifier. used.

Switch circuit 9 held in voltage holding circuit 11
The battery terminal voltage immediately before the switch contact closes is applied to one input of the differential circuit 12, and the output of the voltage detection circuit 5 is applied as is to the other input of the differential circuit 12. Therefore, the differential circuit 12
is the voltage difference between the battery terminal voltage Vb just before the switch contact of the switch circuit 9 closes and the battery terminal voltage that causes a voltage drop when the switch contact of the switch circuit 9 is closed and the on-vehicle electrical load 10 is connected to the battery 1. The voltage drop is detected and output, and this differential circuit 12 constitutes a voltage drop detection means. Further, the voltage drop in the differential circuit 12 is detected by the switch circuit 9.
The voltage difference between the battery terminal voltage and the voltage held by the voltage holding circuit 11 is obtained several seconds after the on-vehicle electrical load 10 is connected to the battery 1.

The voltage drop detected by the differential circuit 12 due to the connection of the on-vehicle electrical load 10 is input to one side of the comparison circuit 13, and the second reference voltage Vr from the second reference voltage circuit 14 is input to the other side of the comparison circuit 13. ₂ is entered. Therefore, the comparison circuit 13 generates a comparison output when the voltage drop obtained from the differential circuit 12 becomes equal to or higher than the second reference voltage _Vr2 , and the warning display is displayed based on the comparison output from the comparison circuit 13. At step 15, a warning of battery failure is displayed.
Therefore, the comparison circuit 13 and the second reference voltage circuit 14
This constitutes an abnormality determining means that causes the warning display section 15 to display a battery drain warning when the voltage drop detected in the differential circuit 12 is a predetermined second reference voltage _Vr2 .

Next, the operation of the embodiment shown in FIG. 1 will be explained.

First, the relationship of battery capacity to battery terminal voltage Vb and battery discharge current Ib is as shown in the characteristic graph of FIG. 2, for example, taking battery 1 with a specified battery voltage of 12V.

As is clear from the characteristic graph in Figure 2,
Battery terminal voltage Vb is battery discharge current Ib
There is a relationship that decreases approximately linearly as increases.
Furthermore, it has a characteristic that uses the battery capacity as a parameter, which is expressed as the amount of charge (%) relative to the amount of electricity when the battery is fully charged. There is a relationship where the decline becomes larger.

In order to predict the rise of the battery 1 having the characteristics shown in FIG.
As Vr ₁ , Vr ₁ =11.75V is set. By setting this first reference voltage Vr = 11.75V, the value of the battery discharge current Ib at which the comparator circuit 6 produces a comparison output is 37A at 100% battery capacity, 20A at 50% battery capacity,
At 30% it's 12A, at 20% it's 8A, and at 10% it's 5A.

Even if the comparator circuit 6 produces a comparison output in this way,
At any of the battery capacities shown in Figure 2,
Since it is not known whether the comparison output is obtained from the Vb-Ib characteristic, the battery capacity cannot be determined from the output of the comparison circuit 6.

The determination of the battery capacity when the comparison output of the comparison circuit 6 is obtained can be obtained from the voltage drop of the battery 1 that is reduced due to the connection of the predetermined on-vehicle electrical load 10 to the battery 1 by the switch circuit 9.

That is, suppose that by closing the switch circuit 9 and connecting the battery 1 to a predetermined on-vehicle electrical load 10, the battery discharge current Ib1 up to that point increases by a predetermined current Δi determined by the load impedance of the on-vehicle electrical load 10. As is clear from the characteristic graph in Figure 2, the voltage drop in the battery terminal voltage with respect to the increase Δi in the battery discharge current is smaller as the battery capacity is larger.
As the battery capacity decreases, a large voltage drop will occur.

Therefore, for example, if a battery warning is to be issued when the battery capacity drops to 20% or less, the slope K can be determined in advance by assuming that the slope of the characteristic curve giving 20% battery capacity is approximately a straight line. Since the increase in battery discharge current when the load 10 is connected is Δi, the voltage drop ΔV due to the connection of the on-vehicle electrical load 10 when the battery capacity is 20% is uniquely determined as ΔV = K × Δi. This on-vehicle electrical load 10
The value of the second reference voltage Vr ₂ by the second reference voltage circuit 14 is determined based on the voltage drop ΔV of the battery terminal voltage expected when the battery terminal voltage is connected. Specifically, the second reference voltage Vr ₂ can be set to a value of about _0.2 to 0.3 V, assuming that a battery warning is issued when the battery capacity becomes 20% or less.

Next, the operation of the embodiment shown in FIG. 1 will be explained in detail by taking as an example the case where the first reference voltage Vr ₁ =11.75V and the second reference voltage Vr ₂ =0.2 to 0.3V are set. do.

Now, the detection voltage of the voltage detection circuit 5 is the specified voltage 12V
Therefore _, if the voltage Vb ₁ drops to 11.5V as _shown in FIG. occurs, and when the comparison output of the comparator circuit 6 is obtained continuously for a certain period of time or more in the discharge state determination circuit 8, the discharge state determination circuit 8 generates a determination output and closes the switch contact of the switch circuit 9, and the discharge state determination circuit 8 generates a determination output and closes the switch contact of the switch circuit 9. An electrical load 10 is connected to the battery 1. The switch output when the switch 9 is closed is given to a voltage holding circuit 11, and the voltage holding circuit 11 holds the detected voltage _Vb1 immediately before the switch circuit 9 closes. Next, switch circuit 9
When a predetermined on-vehicle electrical load 10 is connected to the battery 1 and a few seconds have passed by closing, the battery terminal voltage Vb is increased by Δi from the previous battery discharge current Ib ₁ due to the connection of the on-vehicle electrical load 10. If the battery capacity at this time _is 20%, the voltage drop detected in the differential circuit 12 is ΔV.
(=Vb ₁ -Vb ₂ ) exceeds the second reference voltage Vr ₂ for the comparator circuit 13, and the comparator circuit 13 generates a comparison output, which causes the warning display unit 15 to display a battery-out warning by turning on the display lamp or buzzer. This will be done by the sound of the sound, etc.

If a battery warning is issued in this way, the battery capacity may be low enough to cause the engine to stall or to restart the engine while driving, so the driver should avoid unnecessary on-vehicle load switching. Appropriate measures can be taken, such as turning off the engine, or stopping the engine after sufficient idling when the vehicle is stopped.

FIG. 3 is a circuit block diagram showing another embodiment of the present invention, and this embodiment is characterized by using a calculation means by a microcomputer to give advance warning of battery exhaustion.

That is, the battery voltage 1 detected by the voltage detection circuit 5
The A/D converter 16 converts the terminal voltage Vb into a digital signal and inputs it to the microcomputer 18. The microcomputer 18 includes a CPU 19 as a calculation means and a RAM 2 for temporarily storing input data.
0, and a ROM 21 that permanently stores a processing program for giving an advance warning of a battery failure, and furthermore, a switch circuit 9 connected in series to a predetermined on-vehicle electrical load 10 can be turned on and off by the control output of the CPU 19. That's what I do.

CPU 19 installed in microcomputer 18
The calculation functions are the comparison circuit 6, discharge state determination circuit 8, voltage holding circuit 11, and
The functions of the differential circuit 12 and comparison circuit 13 are realized by program processing. In addition, in order to more accurately determine the battery capacity, a second
Store the table data created based on the characteristic graph of battery 1 as shown in the figure,
Using this table data, in-vehicle electrical load 10
The battery capacity may be determined from the voltage drop ΔV of the battery terminal voltage when the battery 1 is connected to the battery 1, and an advance warning of the battery rising may be issued.

(Effects of the Invention) As described above, according to the present invention, a predetermined electrical load is applied to the battery when the battery terminal voltage continuously decreases below a predetermined first reference voltage. Connect the battery to temporarily increase the discharge current of the battery, detect the voltage drop in the battery terminal voltage at this time, and determine whether the battery capacity has decreased below the specified capacity. As a result, it is possible to determine a decrease in battery capacity by simply detecting the terminal voltage of the battery, so unlike conventional devices, a shunt resistor is used to control the battery discharge current. There is no need for a means to convert it into a voltage signal, and it is possible to accurately determine the battery capacity by detecting only the battery terminal voltage, and to judge and issue advance warnings of battery rise conditions that may cause the engine to stall or be unable to restart after the engine has stopped. can.

In addition, since a predetermined on-vehicle load is only temporarily connected to the battery in order to determine the decrease in battery capacity, the power loss of the battery is significantly reduced compared to the case where the discharge current is continuously detected using a shunt resistor. Furthermore, since the reduction in battery capacity is determined through the actual operation of the battery due to the connection of a new on-vehicle electrical load, it is possible to provide highly reliable advance warning of battery drain.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing one embodiment of the present invention, FIG. 2 is a characteristic graph showing the relationship between battery terminal voltage and discharge current using battery capacity as a parameter, and FIG. 3 is another embodiment of the present invention. FIG. 3 is a circuit block diagram showing an example. 1: Battery, 2: Alternator, 3a-3
n: switch, 4a to 4n, 10: onboard electrical load, 5: voltage detection circuit, 6, 13: comparison circuit,
7: First reference voltage circuit, 8: Discharge state determination circuit, 9: Switch circuit, 11: Voltage holding circuit, 1
2: Differential circuit, 14: Second reference voltage circuit, 1
5: Warning display section, 16: A/D converter, 18: Microcomputer, 19: CPU, 20:
RAM, 21: ROM.

Claims (1)

[Scope of Claims] 1. Voltage detection means for detecting battery voltage during engine operation; A drop in battery voltage caused by a decrease in battery capacity, which is continuously detected for a certain period of time or longer during which the discharge state can be determined by the voltage detection means. The first detection voltage is lower than the predetermined battery voltage.
Voltage discrimination means that generates a discrimination output when the voltage drops below a reference voltage value; Switch means that receives the discrimination output of the voltage discrimination means and connects a predetermined in-vehicle electrical load to the battery; and the load caused by the switch means. Voltage drop detection means for detecting a drop in battery voltage at the time of connection; and when the drop detected by the voltage drop detection means is equal to or higher than a predetermined second reference voltage, a warning display means displays an advance warning of battery rise. A battery rise warning device characterized by comprising an abnormality determination means.