JP2941149B2 - Capacitor capacity diagnostic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for diagnosing the capacity of a capacitor, and more particularly to a capacitor capacity diagnosing apparatus suitable for use in diagnosing the capacity of a backup power supply capacitor of an airbag device provided in an automobile or the like. .

[0002]

2. Description of the Related Art An airbag device protects an occupant by deploying an airbag in front of the occupant in the event of an automobile collision. When deploying the airbag, current is passed from the vehicle battery to a squib for igniting the priming of the airbag device. If the battery system fails, the airbag device does not operate. Therefore, a backup power supply including a capacitor is provided near the airbag device.

[0003] The capacitor may be damaged during use or may have a capacity reduction due to aging. In such a case, the capacitor cannot function as a backup power supply, and the airbag device may not operate at the time of collision of the vehicle. Therefore, at the same time as the operation check of various devices by the microcomputer at the start of the operation of the automobile, the capacity of the capacitor for the backup power supply is diagnosed.

A conventional capacitor capacitance diagnosis apparatus diagnoses a capacitor capacitance by monitoring a change in a capacitor voltage when the capacitor is charged from a power supply via a charging resistor. The charging voltage of the capacitor has a time constant CR
It draws a curve determined by and rises. This time constant is determined by the capacitance C of the capacitor and the charging resistance R. When the capacitance C of the capacitor is decreasing, the charging voltage of the capacitor rises more rapidly than when the capacitance is normal.

A conventional capacitor capacitance diagnostic apparatus measures the time from when the capacitor voltage exceeds the first set voltage to when it reaches the second set voltage by utilizing such characteristics of the charge voltage of the capacitor. If this time is longer than the predetermined time, the capacitance of the capacitor is normal.
Diagnosis was made that there was an abnormality in the capacitor capacity.

[0006]

However, in the above conventional diagnostic apparatus, if the time from when the capacitor voltage exceeds the first set voltage to when the capacitor voltage reaches the second set voltage becomes longer for some reason, it is difficult to solve the problem. Until the time expires, the capacitor capacity diagnosis cannot be terminated. In addition,
It is considered that such a long time is caused by an increase in the charging resistance R or an increase in the capacitance C of the capacitor due to the coupling of another capacitor circuit to the capacitor.

In such a case, if the user waits for the completion of the diagnosis of the capacitance of the capacitor, the time until it is determined that the check is completed becomes longer, so that the next control cannot be performed. For example, it is not possible to quickly shift to the control of the airbag as described above. SUMMARY OF THE INVENTION It is an object of the present invention to shorten a diagnosis time in a capacitor capacity diagnosis device.

[0008]

In order to achieve the above object, the present invention detects a capacitor charging voltage at the time of diagnosing a capacitor, and sets the capacitor voltage to a predetermined first voltage.
In the capacitor capacitance diagnostic device, a time period from when the threshold value is exceeded to when the second threshold value is exceeded is measured, and when the measured time is shorter than a set time, it is diagnosed that the capacitance of the capacitor is abnormal. If the capacitor voltage does not exceed the second threshold value even after the second set time longer than the set time has elapsed, a determination means for terminating the capacitor capacity diagnosis is provided.

According to the present invention, when terminating the capacitor capacity diagnosis, it is possible to diagnose that there is no abnormality in the capacitor capacity.

[0010]

By setting the second set time to an appropriate value, even when the capacitor voltage does not easily reach the second threshold, the capacitor capacity diagnosis can be completed within a desired time. Then, the control can be promptly shifted to the control after the end of the check.

The longer time required to reach the second threshold value is due to an increase in the charging resistance R or an increase in the capacitance C of the capacitor. When used, there is no problem even if the capacitor is used as it is. Therefore, in such a case, it is possible to diagnose that there is no abnormality in the capacitor capacity and to shift to the normal control as it is.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to the diagnosis of the capacity of a capacitor used as a backup power supply for an airbag apparatus will be described below with reference to the drawings. In each of the drawings for explaining the embodiments, components having the same function are denoted by the same reference numerals, and redundant description will be omitted.

First, an outline of the airbag device will be described.
This will be described with reference to the block diagram of the airbag device shown in FIG.
An airbag ECU (Electronic Control Unit) 1 responds to a detection result from an acceleration sensor 2 for detecting the impact of a vehicle collision, and if an acceleration is equal to or more than a certain value, a line m
A microcomputer 3 for controlling the deployment of the output airbag signals a signal to 1, a switching element and the transistor TR ₁ for supplying a current to the squib, the voltage of the battery 5 supplied thereto by the on of the IG switch 9 DC / DC converter 4 which boosts (12V) (24V)
, A backup capacitor 6, an A / D converter 7 for converting a voltage value generated at each end of the resistor R ₁ into a digital value, and a voltage of the battery 5 supplied via the IG switch 9. A constant voltage circuit 8 which converts the voltage to 5 V) and supplies it to the microcomputer 3; a diode 10;
Including a resistor R _2.

The condenser 6 is provided as an emergency power supply that guarantees the deployment of the airbag even if power from the battery 5 is not secured. The power supply of the airbag that connects the battery 5 and the ECU 1 due to a collision is provided. Even if the line is broken, the power stored in the capacitor 6 ensures that the airbag is deployed at a voltage of 24V.

Outside the airbag ECU 1, a switch 11 is provided, for example, on a bumper of an automobile for mechanically detecting a collision of the automobile. A squib 12 that is released into the airbag and instantaneously deploys the airbag, and a condenser 6 and a squib 12 that are provided in an instrument panel, for example.
An alarm means 13 such as an indicator lamp for notifying the driver of an abnormality of the ECU 1 such as the above is provided.

Here, the basic operation of the airbag device will be described. When the IG switch 9 is turned on and the vehicle is traveling normally, for example, when the own vehicle collides with the preceding vehicle,
Based on the deceleration detected by the acceleration sensor 2, the microcomputer 3 determines that the own vehicle has collided. At this time, the microcomputer 3 outputs a pulse wave of Hi in line ml, turn on the transistor TR _1. Also, at this time, since the switch 11 is also mechanically turned on due to the collision of the own vehicle, a large current flows through the squib 12 by a voltage that can be reliably supplied by the power supply from the battery 5 and the backup power supply from the capacitor 6. Then, the ignition of the squib 12 instantaneously deploys the airbag to protect the driver.

Next, the diagnosis of the capacity of the capacitor 6 will be described. FIG. 1 is a block diagram showing a portion related to a capacitor capacitance diagnostic device in the airbag device of FIG. 7, and shows a means for realizing a function executed by the microcomputer 3 as a block diagram. is there. FIG. 2 is a graph showing a change in the capacitor voltage Vc. The horizontal axis indicates time, and the vertical axis indicates the capacitor voltage Vc.
The ratio between c and the power supply voltage Vd is expressed in%.

[0018] IG switch 9 is turned on, the capacitor voltage Vc, as shown in FIG. 2, the time constant CR (C is the capacitance of the capacitor 6, R is the resistance charging resistor R ₁₎ depicting a curve determined by And gradually rise. Note that FIG.
Are the case where the initial value of the capacitor voltage Vc is 0%,
Two cases are shown in which when the G switch 9 is turned on immediately after being turned off, the capacitor does not completely discharge and has an initial value α%.

Capacitor voltage Vc and power supply voltage Vd
Is input to the calculating means 16 of the diagnostic device 15. The calculating means 16 calculates the initial value of the capacitor voltage Vc and the power supply voltage Vd.
Is calculated, the necessary numerical value is read from the storage means 17 according to the ratio, the capacitor voltage Vc is compared with the first threshold value, and when it exceeds this, the operation of the timer 18 is started. When the capacitor voltage Vc reaches the second threshold, the operation of the timer 18 is stopped.

In this embodiment, the capacitor voltage Vc
In both the case where the initial value of is 0 and the case where α% is not 0, the diagnosis of the capacitance of the capacitor can be reliably performed.
Two types of thresholds are prepared. That is, the first threshold value Va ₁ and the second threshold value Va ₂ when the initial value of the capacitor voltage Vc is 50% or less of the power supply voltage Vd, and the first threshold value Vb ₁ and the second threshold value Vb ₁ when the initial value is 50% or more. threshold Vb ₂ is prepared.

Here, in the present embodiment, the reason why the threshold value or the set time is set in two stages will be briefly described. Before the capacitor discharges enough,
When the switch 9 is turned on, as shown in FIG. 2, the initial value of the capacitor voltage Vc has a certain value α%. Therefore, even if somewhat higher initial capacitor voltage Vc, the value that can cover it, and set the first threshold value Vb ₁ and second threshold value Vb ₂ of high value.

Further, the initial value of the capacitor voltage Vc is low.
Sometimes the first and second thresholds can be reached quickly
As shown in FIG.₁And the second threshold
Va _TwoIs set. Thereby, the capacitor voltage V
Condensed at an early stage regardless of the initial value of c
The capacity diagnosis can be completed. Calculation means 1
6 is the power supply voltage Vd and the capacitor when the IG switch 9 is turned on.
The initial value of the capacitor voltage Vc from the power supply voltage Vc is the power supply voltage.
It is determined whether Vd is less than 50% or more.
A predetermined first threshold value Va from the storage unit 17;₁Or V
b₁, And a second threshold value Va_TwoOr Vb_TwoCall
And the capacitor voltage Vc is equal to the first threshold value Va.₁Or Vb
₁At this point, the timer 18 is operated, and the process proceeds further.
And the capacitor voltage Vc becomes the second threshold value Va_TwoOr Vb_Two
Then, the operation of the timer 18 is stopped.

The judging means 19 reads a necessary numerical value from the storage means 20 and measures the time T ₁ measured by the timer 18 (the time when the initial value of the capacitor voltage Vc is 50% or less).
Or T ₂ (a set time when the initial value of the capacitor voltage Vc is 50% or more) and a predetermined first set time Ta
(Time when the initial value of the capacitor voltage Vc is 50% or less) or Tb (time when the initial value of the capacitor voltage Vc is 50%)
(Set time in the above case). In addition, this first
Set time Ta or Tb is 200 ms to 500 ms
Set to a value of the order.

The time T ₁ measured by the timer 18 is
If is first short case and the time T ₂ than the set time Ta is shorter than the set time Tb is the reduction of the capacitor capacitance, since it is the rise in the capacitor voltage Vc becomes faster, the warning means 13 of the indicator lamp , An indication is made that the capacitor capacity is abnormal. Judgment means 1
9 further includes the times T ₁ and T ₂ measured by the timer 18.
Is compared with a second predetermined set time Tc, Td. The set time Tc is a set time when the initial value of the capacitor voltage Vc is 50% or less, and the set time Td
Is a set time when the initial value of the capacitor voltage Vc is 50% or more. The second set times T ₁ and T ₂ are set to values of about one second.

The judging means 19 forcibly stops the operation of the capacitor capacity diagnosis when the operation is not terminated even after the lapse of the second set time Tc or Td after the operation of the timer 18 is started. Terminate. Thus, even when the capacitor capacity increases for some reason and the rate of increase of the capacitor voltage Vc decreases, the diagnosis of the capacitor capacity can be completed within a predetermined time.

In such a case, since the capacitance of the capacitor is larger than usual, there is no particular problem in using it as it is when operating as a backup power supply. Accordingly, it is possible to determine that there is no abnormality in the capacitor capacity, end the diagnosis of the capacitor capacity, and quickly shift to the control of the airbag following various check operations.

Next, the procedure for diagnosing the capacitance of the capacitor will be described in detail with reference to the flowcharts of FIGS. The flow shown in the figure is operated by interruption every predetermined time. When the IG switch 9 is turned on, a check operation is started, and the flow of FIG. 3 is started. In the first operation, the process proceeds from step S31 to step S32, where the power supply voltage Vd and the capacitor voltage Vc are detected.
Since the power supply voltage Vd becomes a predetermined value at the same time when the IG switch 9 is turned on, the process proceeds from step S33 to step S34. Here, if the power supply voltage Vd is not OK, this flow ends. In the first flow, step S34
Then, the process proceeds to step S41 in FIG.

In step S41, a determination is made as to whether the capacitor voltage Vc is less than 50% of the power supply voltage Vd.
If the initial value of the capacitor voltage Vc is less than 50% of the power supply voltage Vd, Hi is set in the flag 2 in step S43, and if it is 50% or more, the flag 2 is set in step S42.
Is set to Lo. Then, Hi is set to the flag 1 in step S45, and the first flow ends. However, if the initial value exceeds 80%, step S
From 44, the process proceeds to step S68 in FIG. 6, an error is displayed, and the check ends.

Next, when the flow of FIG. 3 is entered again, since the flag 1 is set to Hi, step S is executed.
From 36, the process proceeds to step S51 in FIG. When the initial value of the capacitor voltage Vc is less than 50% of the power supply voltage Vd, the process proceeds to step S52, and when it is 50% or more, the process proceeds to step S52.
Go to 55. The above flow is repeated until the capacitor voltage Vc becomes the first threshold value (50% of Vc / Vd in step S52, and 80% of Vc / Vd in step S55) to be compared in steps S52 and 55, respectively. It is.

When the capacitor voltage Vc is higher than the first threshold value,
Then, the process proceeds from step S52 to step S53,
The time 18 when the timer 18 starts to operate₁Measurement is started.
Or go from step S55 to step S56,
-18 starts operation and time T _TwoMeasurement starts and the flow
Is over. Time T₁Or T_TwoMeasurement is started
From the next flow, step S34 in FIG.
From step S35 to step S61 or step in FIG.
Proceed to S64. In step S61 or step S64
Is equal to the capacitor voltage Vc and the second threshold value of 95% or 70%.
% Is compared. When the capacitor voltage Vc is equal to or less than the second threshold
If not, go through steps S63 and S66.
End the row.

When the capacitor voltage Vc becomes higher than the second threshold value, the operation of the timer 18 is stopped, and the operation time T ₁ or T _{2 of} the timer 18 is compared with the first set time Ta or Tb in step S62 or step S65. Is done. If the operation time T ₁ or T ₂ of the timer 18 is shorter than the first set time Ta or Tb, it means that the capacitance of the capacitor has decreased, and the process proceeds to step S68, where it is determined that an abnormality has occurred and the indicator lamp 13 is turned off. The light is turned on, and the check is ended in step S69. If the operation time T ₁ or T ₂ of the timer 18 is equal to or longer than the first set time Ta or Tb, the capacity of the capacitor is sufficient for the backup power supply. The check is ended in step S69.

Next, after the timer 18 starts operating, a second set time Tc (when the initial value of the capacitor voltage Vc is less than 50%) or Td (when the capacitor voltage Vc
Timer 1 has passed when the initial value of
If 8 does not stop, the process proceeds from steps S63 and S66 to step S67. In this case, since the capacity of the capacitor is sufficient, it is determined that the state is normal in step S67, and the check is ended in step S69.

Although the embodiment in which the present invention is applied to the diagnosis of the capacity of a capacitor used as a backup power supply for an airbag has been described above, the use of the capacitor is not limited to this use. Is applicable to general capacitors.

[0034]

According to the present invention, the diagnosis time can be shortened in the capacitor capacity diagnosis apparatus.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a graph showing a capacitor voltage for explaining the operation of the embodiment of the present invention.

FIG. 3 is a first flowchart illustrating the operation of the embodiment of the present invention;

FIG. 4 is a second flowchart illustrating the operation of the embodiment of the present invention.

FIG. 5 is a third flowchart illustrating the operation of the embodiment of the present invention.

FIG. 6 is a fourth flowchart illustrating the operation of the embodiment of the present invention.

FIG. 7 is a block diagram of an airbag device.

[Explanation of symbols]

 5 Power supply 6 Capacitor 9 IG switch 13 Alarm means 15 Diagnostic device 16 Calculation means 17, 20 Storage means 18 Timer 19 Determination means

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G01R 27/26 G01R 31/00 H01G 13/00 361

Claims (2)

(57) [Claims] A capacitor charging voltage is detected during diagnosis of a capacitor, and the capacitor voltage is set to a predetermined first voltage.
Measuring the time from exceeding the second threshold to exceeding the second threshold, and when the measured time is shorter than the first set time, diagnosing an abnormality in the capacitance of the capacitor; Even if a second set time longer than the first set time elapses, the capacitor voltage remains at the second set time.
A capacitor capacity diagnosis device provided with a determination means for terminating the capacitor capacity diagnosis when the threshold value does not exceed the threshold value. 2. The method according to claim 1, wherein the determining unit determines that there is no abnormality in the capacitor when the capacitor voltage does not exceed the second threshold value even after the lapse of the second set time. The capacitor capacitance diagnostic apparatus according to the above.