JPH03181869A - Apparatus for inspecting time constant circuit - Google Patents

Abstract

PURPOSE:To accurately inspect a time constant by a method wherein the charge voltage of a condenser is read at every inspection sampling cycle when the inspection condition of the time constant is formed and the read value is compared with a tolerance range to judge the quality of the time constant. CONSTITUTION:The detection value of a sensor A is read by applying the output of the sensor A to a time constant circuit B and reading the charge voltage of the condenser of the circuit B at every predetermined usual sampling cycle. It is judged whether an inspection condition is formed in an inspection condition judging means C and, when the inspection condition is formed, a predetermined sampling cycle is altered to a shorter inspection sampling cycle in a sampling cycle altering means D and the charge voltage of the condenser of the circuit B is read in a charge voltage reading means E at every altered inspection sampling cycle. Subsequently, it is judged whether the change of charge voltage read in a charge voltage judging means F is within a tolerance range and, when the change of charge voltage is out of the tolerance range, the time constant of the circuit B is judged to be inferior by a time constant judging means G and, therefore, the time constant can be accurately inspected.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an inspection device for inspecting the time constant of a time constant circuit used in an A/D converter or the like.

<Prior art> For example, in an electronically controlled fuel injection system for an internal combustion engine, a throttle sensor, an air flow meter, etc. are used, and the analog output thereof is converted into digital by an A/D converter in a control unit. For example, fuel injection valves, ignition coils, etc. are controlled based on the output of the converter. Therefore, it is important for quality control to inspect whether the time constant of the time constant circuit of the A/D converter matches the regular specifications. Conventional testing devices for testing the time constant of such a time constant circuit include the following.

That is, the time constant circuit of the A/D converter is composed of a resistor 1 and a capacitor 2, as shown in FIG. charge the battery.

The charging voltage of the capacitor 2 is then applied to a latch circuit (not shown) via a comparator (not shown), and a digital signal is manually input from the latch circuit to the control device.

A first conventional example of testing the time constant of the time constant circuit is to visually check whether the time constant matches the regular specifications.

Further, as a second conventional example, there is one in which the time constant is tested by measuring the impedance between A and B in FIG.

<Problems to be Solved by the Invention> However, in the first conventional example using visual inspection, there is a problem that the time constant cannot be effectively inspected due to miniaturization of components (chip formation).

Further, in the second conventional example, since the impedance is measured, the capacitance of the capacitor 2 cannot be tested, so there is a problem that the time constant cannot be tested accurately.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a time constant @path test device that can accurately test the time constant.

<Means for Solving the Problems> For this reason, the present invention, as shown in FIG.
test condition determining means C, which reads the detected value of the sensor by applying the charging voltage to the capacitor at a predetermined normal sampling period, and determines whether the test condition is satisfied; and a sampling period changing means for changing the test sampling period to a shorter test sampling period than the predetermined sampling period when the test conditions are satisfied; and a charging pressure reading means E for reading the charging voltage of the capacitor for each changed test sampling period. a charging pressure determining means F for determining whether the read change in the charging pressure is within an allowable range; and determining that the time constant of the time constant circuit is defective when the change in the charging pressure is outside the allowable range. A time constant determination means G is provided.

<Operation> In this way, when the time constant test conditions are met, the capacitor charging voltage is read every test sampling period, and
This read value is compared with an allowable range to determine whether the time constant is good or bad.

<Example> An example of the present invention will be described below based on FIGS. 2 to 6. In this embodiment, the time constant @path of the A/D converter in a device that controls the fuel injection amount, ignition timing, etc. will be explained.

In FIG. 2, the A/D converter 11 is provided with a time constant circuit consisting of a resistor weight 2 and a capacitor I3. An analog signal (voltage signal) is applied to the capacitor 13 from a multiplexer 15 via a resistor 12 and a changeover switch I4. The multiplexer 15 sends analog signals from sensors such as a throttle sensor and an air flow meter to each channel CH.

~CH,, and input the specified channel CH.

An analog voltage of ~CH, is applied to the capacitor 13.

The charging voltage of the capacitor 13 is applied to the non-inverting terminal of the comparator 16 via the changeover switch 14, and the output voltage of the comparator 16 is applied to the latch circuit 17. The latch circuit 17 converts the analog signal from the comparator 16 into a digital signal and inputs the digital signal to the engine control device 18.

The engine control device ts specifies a channel of the multiplexer 15 and reads a detection signal from the specified sensor. In addition, the engine control device 18
The control unit controls the ignition coil of the fuel injection valve 1 of the engine based on detection signals from various sensors.

Further, the engine control device 18 operates according to the flowcharts shown in FIGS. 3 and 4 to check the time constant of the time constant circuit.

Here, the engine control device 18 constitutes an inspection condition determining means, a sampling period changing means, a charging pressure reading means, a charging pressure determining means, and a time constant determining means.

Next, the operation will be explained according to the flowcharts of FIGS. 3 and 4.

At SL in FIG. 3, it is determined whether the test conditions for the time constant circuit are satisfied or not. If YES, the process advances to S2, and if NO, the routine is terminated.

These test conditions are operating conditions that do not occur during actual operation, are artificially created during inspection at the factory, and are input to the engine control device 18.

In S2, the sampling period is changed to the normal sampling period (
For example, the inspection sampling period is changed from 4o+5ec) to a shorter period (for example, 50 μsec). This inspection sampling period is such that changes in the charging voltage of the capacitor 3 can be sampled. The sampling period is a period for reading detection signals from each sensor during normal operation.

In S3, an inspection start signal is output.

Next, the flowchart of FIG. 4 will be explained. This routine is executed when the test start signal is input.

Sll reads the digital signal from the latch circuit 17 at each test sampling period. In this way, when the digital signal is read every inspection sampling period,
From these digital signals, changes in the charging voltage of the capacitor 13 can be read as shown by the broken line in FIG. The charging voltage of the capacitor 13 increases over time from the time when the input voltage is applied, as shown by the broken line in FIG. In addition, each point of the broken line in FIG. 5 is a read value for each inspection sampling period. Incidentally, a change in the charging voltage of the capacitor 13 is not detected during reading at each normal sampling period.

512 stores data for each test sampling period in RAM.
to store and store information.

At step 313, the accumulated data for each test sampling period is processed to approximate the change in the charging voltage of the capacitor 13 to a continuous charging pressure curve in the linear approximation section shown in FIG.

In S14, it is determined whether or not the approximated charging pressure curve is within an allowable range with respect to the ideal curve. If YES, the process proceeds to 315, and if NO, the process proceeds to S16.

In S15, it is determined that the time constant is within the allowable range and is OK.

In step 316, the time constant is out of the allowable range and is determined to be NG. Here, as shown in FIG. 6, the permissible range is set in consideration of the upper limit permissible error and the lower limit permissible error with respect to the ideal curve. Then, when the charging pressure curve deviates from the allowable range as shown by the broken line in FIG. 5, it is determined to be NG.

As explained above, when the test conditions are met, the charging voltage of the capacitor 13 is read every test sampling period,
Since the time constant is determined to be defective when the change in the charging voltage is out of the allowable range, the time constant of the time constant circuit can be accurately tested, thereby improving the testing accuracy. At this time, by incorporating the programs shown in the flowcharts of FIGS. 3 and 4 in the engine control device 18, the time constant can be tested, so that a low-cost testing device can be provided.

<Effects of the Invention> As explained above, the present invention reads the charging voltage of the capacitor at each test sampling period when the test conditions are met, and compares the read value with the allowable range to determine the quality of the time constant. Since this is done, it is possible to accurately test the time constant and judge whether it is good or bad.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to the claims of the present invention, Fig. 2 is a block diagram showing an embodiment of the present invention, Figs. 3 and 4 are flowcharts of the same, and Figs. 5 and 6 show the same operation. FIG. 7, which is a diagram for explanation, is a diagram showing a time constant circuit. 11...A/D converter 12...Resistor 13
...Capacitor 17...Latch circuit 18.
・Engine control device

Claims (1)

[Claims] The detection value of the sensor is read by applying the output voltage of the sensor to a time constant circuit consisting of a resistor and a capacitor and reading the charging voltage of the capacitor at each predetermined normal sampling period, Inspection condition determining means for determining whether an inspection condition is satisfied; and sampling period changing means for changing an inspection sampling period to a shorter one than the predetermined sampling period when the inspection condition is satisfied;
charging pressure reading means for reading the charging voltage of the capacitor every changed test sampling period; charging pressure determining means for determining whether a change in the read charging voltage is within an allowable range; 1. An inspection device for a time constant circuit, comprising: time constant determining means for determining that the time constant of the time constant circuit is defective when the change is outside an allowable range.