Method for investigating a protective system with air cushion and a device for investigating a protective system with air cushion

The subject of the invention is a method of controlling the efficiency of a supporting capacitor in a protective system with an airbag.

Protective systems with an airbag are known which protect passengers of motor vehicles and usually include an executive system and a control system. The actuator comprises at least one inertia switch connected in series with the excitation device, e.g. an incandescent igniter, and with an electric power source. The control system tests the efficiency of the executive system and controls the activation of the indicator, which informs the vehicle operator about the detected system error. Controls of this type usually check the voltage values ​​at various points of the executive system and compare the values ​​of the controlled voltages with a given range of values, if the value of the controlled voltage is outside this range, it means that a system error has occurred.

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Protective systems with an airbag are powered by a car battery. If the vehicle's deceleration exceeds a value sufficient to close the inertial switches in the protection system, for example during a collision, the excitatory device will operate and inflate the airbag. The battery provides the electricity needed to activate the stimulus device. Known airbag protective systems usually include a support capacitor that works either as the main energy source or as a back-up source in the event that the actuator is disconnected from the battery as a result of a collision.

The supporting capacitor in such protective systems with an airbag must have a capacity that is sufficient to supply the electricity needed to operate the excitation device. Control systems are known that check the steady state voltage on the capacitor terminals. However, an incorrect capacitance value cannot be detected by a simple steady state voltage control on the capacitor terminals.

It is known from US Pat. No. 3,714,627 to control system for an airbag protection system that controls the efficiency of the supporting capacitor. The voltage received at the terminals of the supporting capacitor is compared with the charging voltage generated at the terminals of the control capacitor during the initial supply of the protection system. If the voltage at the holding capacitor terminals is greater than the charging voltage at the control capacitor terminals during this initial power-up period, then the holding capacitor circuit is open. Then the vehicle operator is informed about the error by means of an error indicator.

Also known is a control system for a protective system with an airbag in which the incandescent fuse has one terminal connected to the ground via a resistor and a second terminal connected to the capacitors. The capacitors are connected to the energy source through diodes and resistors, with an inertial switch through other diodes and field effect transistors connected to a microcomputer to which the signaling device is connected. The microcomputer controls the voltage on the tested capacitor. If the controlled voltage at the terminals of the capacitor being checked, partially discharged, has a value not exceeding the specified limit value, which occurs, for example, when the capacitor circuit is open, or has an incorrect value, a signaling device is activated to inform the vehicle operator about the detected error. Control of capacitors in this system requires the use of a separate field effect transistor and a separate voltage divider for each capacitor connected to the analog-to-digital converter. In addition, each capacitor check is time consuming. Because any airbag protection system must be thoroughly tested during the manufacturing process, a long test time is not desirable. It is therefore purposeful to shorten the time needed to carry out a number of tests required during the production of the system, and thus shorten the production cycle.

The method of testing a protective system with an airbag is known from US Pat. No. 4,835,513, in which the efficiency of the supporting capacitor is monitored in an airbag protective system, containing an incandescent igniter, the first inertial switch connected to one incandescent terminal and to a capacitor support and a second inertia switch connected to the second glow plug terminal and to ground. In this method, with the help of elements connecting the capacitor with the energy source, the capacitor is charged to the first voltage value so that if the capacitor capacity is greater than the specified value, sufficient electrical potential is obtained to excite the incandescent igniter by the electricity stored in the capacitor when the first and the second inertia switches close. This method consists in the fact that the capacitor is partially discharged for a specific period of time, the voltage remaining on the capacitor after this specified period of time is monitored, this controlled voltage value being defined as the second voltage value, the difference between the first voltage value and a second voltage value with a specified limit value and an error indication is provided to the vehicle operator if the comparison system indicates, that the voltage is greater than the specified limit.

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The method according to the invention consists in adding the value of the controlled voltage on the capacitor at time T_Qequal to Vc / T_Q/, to the value of the voltage controlled on the capacitor during T ,, equal to V / T. /, the value of the voltage V / T / is subtracted from the value of the voltage V_ / T. / XCXUUCX and this sum is divided by this difference.

In a preferred embodiment of the method, the value of the controlled voltage on the capacitor is divided in time T, equal to νθ / Τι /, by the value of the controlled voltage on the capacitor in time T_Qequal to V_C/ T_Q/.

In a preferred embodiment of the method, the value of C is determined according to the equation:

^c · Tjw λΓ '

L^vc^{/ T}1^/ - ^vd where t is the discharge time equal to the difference between the times T and T_Q, R is the composite charge / discharge resistance and is the value of the final voltage across the capacitor, with partial discharge of the capacitor being carried out over a considerable period of time.

In a preferred embodiment of the method, the value of C is determined according to the equation:

In - ^vf

L^Vc^{/ T}l / * ^Vft

2R

IN ⁺ W 'w - w.

2V, where t is the discharge time equal to the difference between the times T and T_Q, R is the composite charge / discharge resistance and Vf is the value of the final voltage across the capacitor, with partial discharge of the capacitor carried out over a significant period of time.

An advantage of the invention is to provide a method for checking the efficiency of a supporting capacitor in a protective system with an airbag that allows accurate determination of the efficiency of a supporting capacitor in a protective system in which the first and second inertia switches are connected to both terminals of the incandescent fuse. It is also possible to accurately determine the values ​​of inertial switch resistors connected in parallel.

When measuring voltages to determine the value of the capacity of the supporting capacitor, accuracy is functionally related to the voltage supplied from the electric power source to the tested circuit, to the voltage received at the terminal in the tested circuit, to the values ​​of resistors in the tested circuit and to the voltage drop across the diodes in the tested circuit . The invention makes it possible to remove the effects of changes in the said voltages, voltage changes associated with changes in the value of resistors and voltage drops on the diodes. The solution according to the invention reduces the likelihood of errors and provides a significant increase in security compared to known solutions.

The subject of the invention is explained on the basis of the description of the drawing, in which Fig. 1 shows a known device for testing an airbag protection system, Fig. 2 - a known modified device for testing an airbag protection system implementing the method according to the invention, Figs. 3A, 3B and 3C - voltage waveforms as a function of time in the device of Fig. 2, Fig. 4A, 4B - procedural block diagram of the device of Fig. 2 and Fig. 5 - a procedural flowchart showing more precisely one operation of the flowchart of Fig. 4.

Figure 1 shows a known device for testing a protective system with an airbag The incandescent igniter 10 has one terminal connected to ground via a resistor 12 of 0.1 ohms and the other terminal connected to capacitors 14, 16. Capacitor 14 is connected to a voltage source Vup via a resistor 20 limiting the current and diode 18. The capacitor 16 is connected to the voltage source Vup through a resistor 22 limiting the current and the diode 18. Capacitors 14, 16 are charged via the incandescent fuse 10. The voltage arising on capacitors 14, 16 is essentially equal to the voltage of the electricity source V

Resistors 20, 22 prevent firing of the incandescent igniter 10 when charging capacitors 14, 16.

Capacitors 14, 16 are connected to one terminal of the inertia switch 24 respectively by diodes 26, 28. The other terminal of the inertia switch 24 is connected to the electric ground. Resistor 29 is connected in parallel to the inertial switch 24. After closing the inertial switch 24, the discharge current of the capacitors 14, 16 flows through a glow igniter 10 of sufficient intensity and duration.

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Capacitors 14, 16 are additionally connected to field-effect transistors 30, 32 via resistors 34, 36 respectively. Each half-transistor 30, 32 has a control electrode connected to a microcomputer 38. The node connecting the resistor 20 and the capacitor 14 is connected to a voltage divider 40 containing resistors 42 , 44 attached in series to the electrical mouse. The node connecting the resistor 22 and the capacitor 16 is connected to a voltage divider 46 containing resistors 48, 50 connected in series to the electrical ground.

The node connecting resistors 42, 44 is connected to the analog-to-digital converter 52.

The node connecting the resistors 48, 50 is connected to the analog-to-digital converter 52.

The analog-to-digital converter 52 is attached to the microcomputer 38. The microcomputer 38 is connected to the signaling system 54.

The device shown in Fig. 1 monitors the efficiency of the capacitors 14, 16 in series, i.e. separately. The microcomputer 38 partly discharges one of the tested capacitors and controls the voltage across the capacitor by means of a 40/46 split and a connection to an 52-D converter.

Figure 2 shows a known modified device 100 for testing an airbag protection system implementing the method of the invention. The device 100 includes an incandescent fuse 102 with a first terminal 104 connected to the first inertia switch assembly 106. The glow igniter 102 also has a second terminal 108 connected to the second inertia switch assembly 110.

The inertia switch assembly 106 includes a normally open inertia switch 112 and a resistor 114 connected in parallel thereto. The assembly 106 is called a safety sensor. The inertia switch assembly 110 includes a normally open inertia switch 116 and a resistor 118 connected in parallel thereto. The assembly 110 is called a front sensor. Usually the safety sensor is located inside the vehicle and the front sensor is located in a remote place near the front of the vehicle.

The front sensor 110 has a second terminal connected to the electrical ground. The second terminal 134 of the safety sensor 106 is connected to the battery 117 via the ignition switch 119 and the diode 120. The second terminal 134 of the safety sensor is also connected to the output of the converter 122 increasing the voltage by serial connection of the diode 124, resistor 126 and diode 128.

Voltage value V_up in a preferred embodiment it is significantly higher than the value of the battery voltage that is obtained via the ignition switch. The Vup voltage is used to charge the capacitor 130 connected between the node connecting the resistor 126 and diode 128 and ground. The voltage value at the charged capacitor 130 is equal to the voltage value Vu_p minus the voltage drop across diode 124 and resistor 126. The Vc voltage present at terminal 134, which is connected to the cathode of the diode 128, is equal to the voltage value on the charged capacitor 130 minus the voltage drop across the diode 128. The voltage Vc in normal operating conditions is much higher than battery voltage value, which causes the diode 120 to be reverse-polarized.

The values ​​of resistors 114 and 118 are selected so that the value of the current flowing in the steady state through the glow igniter 102 is significantly lower than the value required to ignite the glow igniter. Resistors 114, 118 in combination with the incandescent fuse 102 form a voltage divider. The value of voltage present at terminals 104, 108 results from the proportional voltage distribution V ^ Usually the value of the resistance of the igniter 102 is about 2 ohms. It is desirable for the resistance values ​​of the resistors 114, 118 to be 5 kilohms each.

Therefore, the voltage present at terminals 104, 108 is about half the voltage V ^

The analog-to-digital converter 140 is used to control the voltage in various devices of the device 100. The first input of the analog-to-digital converter 140 is connected to the output of the converter 122 increasing the voltage through a resistance divider 144 containing resistors 146, 148 connected between converter output 122 and ground . The filtering capacitor 150 is connected between the connection of resistors 146, 148 and ground. The second input 152 of the analog-to-digital converter 140 is connected to voltage on terminal 134 through a resistance divider 154 containing resistors 156, 158 connected in series between terminal 134 and ground. The filtering capacitor 160 is connected between the connection of resistors 156, 158 and ground.

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The differential amplifier circuit 170 is used to control the voltage received at the incandescent fuse 102. The differential amplifier circuit 170 includes an operational amplifier 172 having a non-inverting input 174 connected to terminal 108 via resistor 176. A non-inverting input 174 is also connected to a DC voltage source via resistor 178 Direct voltage V ^ c is used to polarize the non-inverting input 174. Non-inverting input 174 is also connected to the filtering capacitor 180. A second terminal of the filtering capacitor 180 is connected to ground.

The inverting input 182 of the operational amplifier 172 is connected to terminal 104 via a resistor 184. The operational amplifier 172 has an output 186 that is electrically connected to its own inverting input 182 through a parallel circuit consisting of resistor 188 and capacitor 190. Terminals 1932 and 194 of the operational amplifier 172 are connected to converter output 122 and to ground.

The output 186 of the operational amplifier 172 is connected to the output terminal 196 of the analog-to-digital converter 140 through a series circuit consisting of resistors 200 and 202. The filtering capacitor 204 is connected between one terminal of resistor 202 and ground. Diode 205 is connected to the node connecting resistors 200 and 202, while diode 205 is energized. Diode 205 prevents voltage being applied to input 196 of the analog-to-digital converter 140 when the device 100 is not powered.

Input terminal 206 of the analogue-digital converter 140 is the auxiliary di terminal 108 through the resistance divider circuit 208, which consists of 210, 21 2 resistors inserted in series between terminal 108 and ground. Filter capacitor 214 is connected between the node connecting resistors 210, 212 and ground. There is a voltage Vp on terminal 108. There is a voltage V ^ at the output 186 of the operational amplifier 172.

The analog-to-digital converter 140 is operatively connected to the microcomputer 250. The microcomputer 250 addresses the signals fed to the inputs of the analog-to-digital converter 140. The analog-to-digital converter 140 sends series output binary coded signals directed to the microcomputer 250. The microcomputer 250 is programmed to calculate the resistance values ​​of resistors divisors included in the device 100. For example, when measuring the voltage V ^ on terminal 108, the voltage present at the input 206 of the analogue-digital converter 140 is divided by the resistors 210, 212. The microcomputer 250 calculates the resistor values ​​when determining the voltage present at terminal 108.

The first switching circuit 260 is connected in parallel to the sensor 106. The switching circuit 260 includes a pnp 262 transistor whose emitter is connected to terminal 134. The collector of transistor 262 is connected to terminal 104 via resistor 264. The base of transistor 262 is connected to terminal 134 via resistor 266 The base of transistor 262 is also connected to the collector of transistor npn 270 through resistor 272. The emitter of transistor 270 is connected to ground. The base of the transistor 270 is connected to the output terminal 274 of the microcomputer 250 via a resistance divider circuit 276. The resistance divider circuit 276 includes resistors 278, 280 connected in series between output 274 and ground. The base of transistor 270 is connected to the node connecting resistors 278 and 280.

The second switching circuit 290 is connected in parallel to the front sensor 110. The second switching circuit 290 comprises a npn 292 transistor whose collector is connected to terminal 10B via a resistor 294. The emitter of transistor 292 is connected to ground. The base of the transistor 292 is connected to the output 29B of the microcomputer 250 via a resistance divider circuit 300. The resistance divider circuit 300 includes resistors 302, 304 connected in series between output 298 of microcomputer 250 and ground. The base of transistor 292 is connected to the node connecting resistors 302 and 304.

Transistors 262, 292 are designated as Q1 and Q2. The microcomputer 250 controls the excitation of transistors Q1 and Q2 so that there is a selective connection of resistors 264, 294 in parallel with resistors 114, 118.

The microcomputer 250 also has an output 310 connected to an indicator 312 located inside the vehicle cabin. The indicator 312 provides the vehicle operator with an indication of the error detected in the device 100. The microcomputer 250 also has an output 316 connected to permanent memory 318, which is used to record error information used for analysis by technical service personnel.

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The device provides accurate measurement of the impedance value of each of the inertia switch resistors 114, 118 and control of the efficiency of the capacitor 130, which is to check the correct activation of the capacitor and to check that the capacitor has the correct, or at least the minimum capacity value. The device 100 performs measurements of the resistor and capacitor in parallel, i.e. two measurements simultaneously. Checking the capacitor short circuit is also carried out by measuring the Vg voltage value at the input 152 of the analogue-digital converter 140. If the microcomputer 250 determines that Vc is less than the 18 V DC voltage, then the capacitor 130 is shorted.

Figures 3A, 3B, 3C, 4A, 4B and 5 are shown to explain the operation of the device implementing the method according to the invention.

Figures 3A, 3B and 3C show voltage waveforms as a function of time in the device of Fig. 2, and Figs. 4A and 4B are a schematic block diagram of the device of Fig. 2. When carrying out operation 400 of Fig. 4A, the device is powered on when the operator starts the vehicle. The microcomputer 250 delays any further operation of the device 100 by the time delay X1. The X1 time delay is sufficient to ensure that the capacitor 130 is fully charged. This delay is implemented during operation 402. During operation 404, the microcomputer 250 measures the value of voltage Vg on terminal 134 and measures the value of voltage VUp. Both measured values ​​are stored in the internal memory of the 405 microcomputer. To measure the capacitance value of the capacitor 130, the capacitor discharges partially, i.e. over an allowed period of time. In order to accomplish this partial discharge, the microcomputer determines during operation 406 operating conditions corresponding to the discharge of the capacitor, as a result of which during transistor 408 transistors Q1 and Q2 are brought into a conduction state. When transistors Q1 and Q2 conduct, resistor 264 is connected in parallel to resistor 114 and resistor 294 is connected in parallel to resistor 118. Such a parallel connection of resistors causes a decrease in the Vg voltage value present at terminal 134.

Returning to Fig. 3A, if transistors Q1 and Q2 are in a state of conduction at the time of Tg and are in a state of non-conductivity at the time of Tp, the voltage Vc decreases by

V. If at time T1 transistors Q1 and Q2 are both in a nonconductive state, the capacitor 130 begins to charge to a value that is equal to the value of voltage V_up minus the voltage drop across diode 124 and resistor 126. If the capacitor 130 value is greater than the set minimum value, then the voltage drop V will be less than the set maximum value. At the moment T1 the microcomputer can start to control the Vg voltage. If the voltage drop V during the period T0 to T ^ is greater than the set limit value, it means that the capacitor 130 value is smaller than the set minimum value.

It was found that the fulfillment of the condition:

^ZT0^FROM - ^Vc ^ZT1^FROM <threshold value ^ (1) ensures good accuracy in controlling small capacities, i.e. capacitance values ​​smaller than the set value. The accuracy of this control measurement is functionally related to the value of V and V * up 'cc voltages, which relationship serves as the reference level for the analog-to-digital converter 140, not the resistance values ​​of resistors 156 and 158. Changes in resistance of resistors 156 and 158 within tolerance are effectively eliminated in the calculation.

The improved condition that essentially eliminates the effects of changes in the Vgg and V voltages is as follows:

up ^VC ^ZT0^FROM v_c / T / ^VC ^ZT0^FROM * ^VC ^ZT1^FROM threshold value?

The result of this division essentially removes changes in the voltage ratio V

CC (2) and 'up, and voltage drops on diodes 124 and 128. The only significant changes result from the uncertainty of processing carried out by the analog-to-digital converter and errors from cutting off, associated with the division operation carried out by the microcomputer 250.

Equation (2) can be mathematically reduced as follows:

^VC ^{/ T}1^ZVC ^ZT0^FROM

256 threshold ^ (3)

167 782, which further reduces the variability of this solution from the processing uncertainty of the analog-to-cffr converter. This capacity control can be considered as controlled control, i.e. adapted to changes in Vc £, Vup and to voltage drops on diodes 124 and 128.

Another control, which is not as accurate as the preferred method represented by equation (3), but is not less valuable as an independent control, i.e. which can be used at the end of the line control, is to calculate the actual value of capacitor 130.

Namely:

^VC ^{/ T}L^{Z = V}C ^{/ T}0^{With e_t / <+ V}f ^Z1 ®·^{ί / 4}7 (4) where = RC, R is the equivalent total charge / discharge resistance, t is the discharge time / T ^ - Tg /, and is the final voltage achieved if transistors Q1 and Q2 are left for a substantial part of the period at supply voltage V_ATp. Solution of equation (4) with respect to C gives: as a result the following equation:

(5)

R · Iri

M / Tq /

V_c /_tl/

Using the Taylor series approximation for the natural logarithm, we obtain: .3, /

Μ ι · · · Η & &)

Ing X = 2

This gives a series that converges quickly so that the approximation of 1n X can be represented in the form:

ln X = 2 ^{+ 1}

Substituting the approximate equation (7) with equation (5), we obtain: t (7)

2R% ^ZT0^{Z + V}C ^ZT1^FROM - ^2Vf ^VC ^ZT0^FROM v_c / t_x/ (8) equation (8) can be rewritten as follows:

t

C = - 2R <V_P / T_n/ + V_r /T./

2V, ^VC ^ZT0^FROM^VC ^ZT1^FROM (9) where C is the capacity, t is the discharge time / T1 - Tg /, and R is the equivalent total charge / discharge resistance. We assume that R = 490 ohms, t = 300 ms, Vg / Τθ / = 23 V, Vc / T_x/ = 22 V and Vf = 19 V.

The solution of equation (9) gives the result:

C = -—- · (45-38) (10) · (490) or C = 2143 pF. (11)

Such loads are easily performed in the form of a simple equation:

300 · [V_r /T./ + V_r / T_n/ - 150]

C - -2-1-2-2- (12) ^VC ^ZT0^FROM - ^VC ^ZT1^FROM

Because Vf and R are 'evaluated values, the accuracy of equation (12) is less than the accuracy of equation (3). However, the check carried out according to equation (9) is beneficial in that it reduces the control time and increases the confidence that equation (3) provides accurate information.

It is assumed that the expected voltage drop under conditions when transistors Q1 and Q2 conduct within 295 milliseconds from time T0 to time T_L, is 2.5 V. If the voltage values ​​V_atpi Vcc correspond to the rated values, the rated result can be calculated. If the Vup voltage is greater than the rated value, the Vc voltage will also be greater than the rated value, and the output signals of the analog-to-digital converter,

167 782 representing Vc / Tg / and Vc / Ti /, will increase proportionally. The split operation effectively eliminates the increase in Vu voltage_p and voltage changes Vgg. The result of dividing Vc / Tq / by Vc / ^ / is automatically composed in terms of normal changes in the parameters of the device components.

The i30 capacitor should have sufficient capacity to ensure that sufficient electricity is supplied to fire the i02 fuse. Electricity supplied by the capacitor should be available within a predetermined time after disconnecting the battery from the Vup voltage and the switch igniter ii9. This means that the capacitance value of the i30 is important. Discharge / charge cycle shown in fig. 3A usually lasts seven seconds.

It is also possible to control other parts of the control circuit simultaneously with the control of the i30 capacitor.

Figures 4A and 4B show that the microcomputer introduces the time delay X2 in operation 4i0 after both transistors Qi and Q2 have been brought into a conduction state. In figure 38, the time delay X2 is determined by the times T0 and Ta. During the 4i2 operation, the microcomputer begins a series of switches of Qi and Q2 transistors from the conduction state to the clogged state and vice versa. Voltage values ​​in each state are measured and stored for later use. Operation 4i2 is shown in detail in Figure 5.

During operation 420, the microcomputer 250 puts transistors Qi and Q2 into a non-conductive state. After cutting off transistors Qi and Q2, the microcomputer introduces a delay during operation 422. Figure 3B shows that transistors Qi and Q2 stop conducting at time Ta and the time delay is equal to the difference between times Ta and Tg. During Tg during operation 424 the microcomputer reads the voltage values ​​on all inputs of the analog-to-digital converter and stores these values ​​in the memory 405. The i30 capacitor charges during the time between Ta and Tg. During Tg during operation 426, the microcomputer B puts the transistor Qi into a conduction state. The microcomputer then causes during operation 428 the time delay marked in Fig. 3B as the time between the times Tg and Tc. During this period, the capacitor i30 discharges at a slower rate than when both transistors Q1 and Q2 are in a conduction state.

During Tc, the microcomputer, performing operation 430, reads the Vc voltage values ​​and stores these values ​​in memory 405. During Tc, the microcomputer, by performing operation 432, puts transistor Q2 into conductive state and causes during operation 434 the time delay marked in Fig. 3B as the period between times Tc and Tg. During this period, both transistors Qi and Q2 are in a conduction state and the capacitor i30 discharges at the same rate as it discharges during the period between times T0 and Ta. During Tg during operation 436, the microcomputer reads the values ​​of voltages V ^ V ^ and Vs and stores these values ​​in memory 405. During Tg during operation 438, the microcomputer puts the transistor Qi into a non-conductive state and causes during the operation 440 the time delay marked in Fig. 3B as the period between times Tg and T0. During this period, the capacitor i30 continues to discharge, but at a slower rate than when both capacitors Qi and Q2 were in a conduction state. During T0 during operation 442, the microcomputer reads the values ​​of voltages Vc and Vj- and stores these values ​​in memory 405.

During operation 444, the microcomputer determines whether the discharge flag has been set, if the discharge flag has been set, the transistor Q1 is in the conduction state and the program returns to the main program in operation 448. Operation 446 ensures that both transistors Qi and Q2 are in a conduction state so that the portion of the capacitor control operation associated with the discharge continues, if the result of operation 444 is negative, which means that the capacitor is in the charging state, the program goes to operation 450 when transistor Q2 is in a nonconductive state. Operation 450 ensures that both transistors Q1 and Q2 are in a nonconductive state, which causes the i30 capacitor to charge.

Returning to Figures 4A and 4B, the microcomputer performs a series of control tests during operation 460. The control tests account for the majority of measurements of the resistance of resistors ii4, ii8, incandescent fuse i02 and capacitor capacity i30, which is intended by the end. that there are no open circuits or short circuits. The first test performed by the micro167 782 computer 250 is a test that checks whether the glow plug circuit 102 is open by checking the voltage at input 196. If the voltage at input 196 is less than 1 V, it means that the glow plug 102 has circuit open.

The second test, carried out in a series of control tests by the microcomputer 250, is a test that recalls the voltage value that occurred at terminal 134 when transistors Q1 and Q2 were cut off, and recalls the voltage that occurred at terminal 134 when transistors Q1 and Q2 were in conduction state. The microcomputer 250 then performs the operation to check that the condition given in the equation is met:

'c / Q1, Q2 cut off / - Vg / Q1, Q2 conduct / 1.63 V (p)

If the result of equation (13) is true, then the capacitor 130 is considered connected in the open circuit.

The third test in a series of control tests, carried out by the microcomputer 250, is a test that recalls the voltage value that occurred at terminal 108 when transistor Q2 was in a conduction state, and that recalls the voltage value that occurred at terminal 108 when transistor Q1 was in a state conduction. The microcomputer 250 then performs the operation to check that the condition given in the equations is met:

Vp / 01 conducts / 6.20 V (14) and

V_F / 02 leads / —- / 0.11 (15)

Vp / Q1 leads /

If these conditions are met, then the microcomputer 250 assumes that the safety sensor 106 has an open circuit. In this situation, this means an error during check-up testing. After all control tests have been performed, operation 462 follows, during which the microcomputer 250 checks that all control tests have been performed. If the condition of equation (15) is met, then operation 464 occurs, during which the indicator light is on. Then operation 466 is performed, during which the error is saved in the programmed permanent memory. Then, during operation 468, the microcomputer 250 monitors the error occurrence time and starts recording in the permanent memory the time of occurrence and duration of the error. Then surgery 470 is performed.

Other control tests performed during operation 460 include recalling the capacitor Vg charge value and voltage value at terminal 108 when transistors Q1 and Q2 are in the cutoff state, and the initial voltage value at terminal 108 when the transistor Q2 is in the conduction state. The microcomputer 250 then performs the operation to check that the conditions given in the equations are met:

Vg - Vj- / 02 conducts / 0.6 V (16) or / V_r / 01, 02 cut off /

- > _0>51 (17)

Vp / 02 leads /

Vp / 01, 02 cut off /> 0.35 (18)

If condition (16) or condition (17) and condition (18) are met, the microcomputer 250 assumes that the safety sensor is shorted. Otherwise, the microcomputer 250 recalls the value of voltage present at terminal 108 when transistors Q1 and Q2 are cut off, the value of voltage present at terminal 134, and the value of voltage present at terminal 108 when transistor Q1 conducts. An operation is then carried out to check that the conditions in the equation are met:

Vp / 01 conducts / 0.6 V (19) or <».« ^<2>

Vp / 01 leads /

0.78 (21) and

V

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If condition G9) or conditions (2Τ) and (2,) are met, then the 25T microcomputer assumes that the front UT sensor has an open circuit. Otherwise, the microcomputer 25uter calls up the voltage value at the terminal, T8, gj y transit jj ij 2 o rescated, ozo zk / wa ^ the axis is written on the terminal, T8, when the transistor d conducts, the value hinged it jzαiśau jOT, gdd jtawacyaaa Q2 conducts and voltage Vc and performs the following operation to check that the condition given in the equation is met:

V '' ^VF

-L- / 0.40 (22)

Vj- / Q1 conducts / - Vp / Q2 conducts / \

If condition (22) is met, the 25T microcomputer assumes that the front UT sensor has an open circuit. Otherwise, the microcomputer recalls the input voltage value 96 when transistors Q and Q2 conduct, and perform the following operation to check. whether the condition given in the equation is met:

Vg / Ql, Q2 conductive / 1 V (23)

If condition (23) is met, the 25T microcomputer assumes that the incandescent fuse, T2 has an open circuit. This test prevents an ignition resistance greater than 5 ohms being mistakenly recognized as a short circuit in the W2 filament igniter.

If no error is found during 46T operation, it assumes sip that the resistors U4, U8 and incandescent fuse, T2 and capacitor, 3T are electrically connected and their values ​​are in the range that can be determined with the help of the system, TT.

If all tests are carried out, there is a transition from surgery. 462 for operation 48T, during which the 25T microcomputer calculates the resistance values ​​of the resistors U4, U8 and incandescent fuse, T2. To calculate the resistance of U4 resistors, U8 uses the following equation sip:

R / 118 /

R / 118 / + R / 114 / (24)

When transistor Q is cut off and transistor Q2 conducts, the voltage V ^ at terminal W8 can be calculated from the following equation:

'--Ί

R / 114 / + Rj (25)

When the resistance R is equal according to the equation

R / 118 / · R / 294 / (26). R / 118 / + R / 294 /.

we obtain by substituting equation (26) for equation (25) and solving it with respect to R / H8 /:

R / 118 / =

<td>Γν^vc</td><td>/ v_F -</td><td>ν_ρ./Ί</td>

<td>^VF-</td><td> • ^{/ V}C</td><td>- V</td>

R / 294 / (27)

If the resistance value of resistor 294 is equal, kiloom, equation (27) can be simplified to the equation:

/ V_c

R / 118 / v_F- / / v_c - v_F/ (28)

The resistance of the U8 resistor calculated according to the formula (28) is expressed in ohms. By substituting equation (28) for equation (24), we calculate the resistance value of the resistor H4 according to the following equation:

R / 114 / =

V_F·/ (29)

Equation (29) assumes that the resistance value of resistor 294 is equal to, kiloom. Then the resistance value of the U4 resistor calculated from equation (29) is also expressed in kiloohms.

The resistance values ​​of the resistors U4, U8 can be determined by measurements carried out only in two cycles of operation of transistors Q, and Q2, that is, measurement when transistors

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Q1 and Q2 are cut off and measurements when transistor Q1 is cut off and transistor Q2 conducts. The same calculations with the help of measurements can be made when transistors Q1 and Q2 are cut off and measurements when transistor Q1 conducts and transistor Q2 is cut off. If V_FH is the voltage at terminal 108 when transistor Q1 conducts and transistor Q2 is cut off, resistance values ​​R / 114 / and R / 118 / are calculated according to the following equations:

/ V

R / 114 / =

R / 118 / = / V_r

F ^{/ v}c, · / V

V_F„/ (30)

F

- v_F„/ ^{/ v}c (31)

Voltage values ​​V_c, Vp, Vf * and Vf "are measured using an analog-to-digital converter 140. A preferred method of calculating the resistance of the front sensor of resistor 118 is given in equation (28). The preferred method of testing the resistance of resistor 114 is based on the recognition that:

R / 118 /

F

L^r1

R / 11B / (32)

When the resistor R ^ is a parallel connection of resistors 114 and 264, we get

R / 114 / · R / 264 / - --- ¹ R / 114 / + R / 264 / (33)

When substituting equation (33) for equation (32), equation (32) takes the form (R / 118 / · R / 114 /) + (R / 118 / · R / 264 /)

V, = -. _V^h [_ (R / 114 / · R / 264 /) + (R / 114 / · R / l18 /) + (R / 264 / · R / 11B /) J ^L

A similar analysis gives for voltage V_F equation:

'R'

V = -. v^h R + R / 114 / ^L (34) (35)

The resistance R is determined as in equation (26).

Substituting equation (26) to equation (35) we get:

'(R / 118 / · R / 294 /)'

V. = -. v_r^r [_ (R / ll8 / · R / 294 /) + (R / 114 / · R / 118 /) + (R / 294 / · R / l14 /) J ^L

When designing, R / 294 / equal to R / 264 / is assumed. The denominator is equal to the denominator of the equation (36). Equation (34) can be divided and gives as a result:

(36) equation (34) stands by equation (36) ^VF Γ R / 114 / + R / 264 / ^VF · R / 294 /.

(37)

When selecting R / 264 /

R / 294 / kiloom, equation (37) takes the form of the equation:

F

R / 114 / + 1 (38)

By solving equation (38) for R / 114 /, the following equation is obtained:

R / 114 /

<img file="PL167782B1_D0001.tif" />

(39) where resistance R / 114 / is expressed in kiloohms. This method of determining the resistance value of the resistor 114 is advantageous for two reasons: only one analog-to-digital converter channel is needed to obtain information, which eliminates errors related to voltage changes Vc from equation (29) and in connection with sharing the results obtained in one channel, changes in R / 210 / and R / 212 / resistance values ​​are eliminated. At the same time, changes in the value of resistance R / 156 / and R / 158 / are also eliminated, since the measurement of voltage V ^ is eliminated.

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For the measurement of resistance R / 118 / a similar approximation may be used taking into account the equations:

* F (R / 114 / -R / 264 /) + (R / 114 / · R / 118 /) + (R / 264 / -R / 118 /) (R / l14 / · R / 264 /) + ( R / 114 / · R / 118 /) + (R / 264 / · R / l18 /) _ (R / l18 / · R / 114 /) + (R / 118 / · R / 264 /) _ (R / 114 / · R / 264 /) + (R / l14 / · R / 118 /) + (R / 264 / · R / 118 /) (40) ^VC ~^VF ^VC '^VF ' ^VC-^VF (R / 114 / · R / 264 /) (R / 114 / -R / 264 /) + (R / 114 / -R / l18 /) + (R / 264 / -R / 118 /)

<td></td><td>(R / UB / · R / 294 /) + (R / 114 / · R / 118 /) + (R / 294 / -R / 114 /)</td>

<td></td><td>(R / ll8 / R · / 294 /) + (R / L14 / R · / 118 /) + (R / 294 / R · / 114 /)</td>

(R / 118 / · R / 294 /) (R / 118 / · R / 294 /) + (R / 114 / · R / 118 /) + (R / 294 / · R / 114 /) (R / 114 / · R / 118 /) + (R / 294 / · R / 114 /) (R / 118 / · R / 294 /) + (R / 114 / -R / l18 /) + (R / 294 / -R / 114 /) (41) (42) (43)

By dividing equation (43) by equation (41), assuming that R / 294 / = R / 264 / = 1 kiloom, we get the equation:

<img file="PL167782B1_D0002.tif" />

= R / 118 / + 1

Solving equation (44) for R / 118 /, we get (44)

R / 118 / v_F"- v_F, (45)

Equation (45) seems simpler than equation (28), but determining R / 118 / in accordance with equation (28) gives a more accurate result.

After completing this last test, the microcomputer calculates the resistance of the incandescent fuse 102.

The analog-to-digital converter is a bit-bit converter. whose serial outputs provide binary numbers between 0 and 255. The binary number 0 is the output signal when a voltage of 0 volts is measured. The binary number 255 is the output signal when the measured voltage is equal to the voltage of the analog-to-digital converter. As the voltage values ​​Vf, V ^, Vf "approach zero or when the values ​​(Vf * - Vf) or (Vf ',,) al because (V- -_nd. approaching near zero, results of these measurements become uncertain, which is caused by the operating characteristics of the analog-to-digital converter. The analog-to-digital converter usually has an uncertainty of order - 1. If, as a result of the measurement, the analog-to-digital converter produces an output signal representing a binary number of 100, an uncertainty of - 1 means an error equal to - 1%. However, when the voltage approaches zero and, for example, when the output of the analog-to-digital converter is the binary number 5, an uncertainty of - 1 means an error of - 20%. Therefore, at extremely low voltage values, the analog-to-digital converter is impractical. For this reason, the invention envisages carrying out control tests during operation 460 to determine initially whether the voltage values ​​are within a range that would be unfavorable due to the measurements being carried out using an analogue to digital converter.

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Then, there is a transition from operation 480 to operation 482, during which it is checked if all or not all of the resistance values ​​calculated during operation 480 are within the specified range. If the result of the check, carried out during operation 482, is negative, then returns to operation 464, during which the indicator is activated. The error determining the resistance value is saved in the programmed permanent memory during operation 466, and the error time is controlled and stored during operation 468. From operation 468 or from the operation confirming the results obtained during operation 482, operation 470 is performed to determine whether the discharge flag is set. If the discharge marker is set, then proceeds to operation 486, during which it is determined whether the discharge time has expired.

The check of how long the capacitor is discharged before the final measurement of voltage V ^ is carried out for the purpose of checking the capacity value and is carried out by comparison with the capacitor curve. Voltage V ^, without taking into account voltage drops on diodes 124, 128, when transistors Q1 and Q2 are cut off, can be determined by the following equation:

. 26.3 (R / 114 / + R / 118 /)

V = - (46) (R / 114 / + R / 118 /) - R / 126 /

Assuming that the resistance values ​​of the resistors 114, 118 are equal to 5 k ohms and the resistance value of the resistor 126 is equal to 511 ohms, we obtain a voltage value of Vg equal to 25 'V. Then, when both transistors Q1 and Q2 conduct, the voltage across the capacitor will tend to decrease to the value of voltage Vę ·, unless the voltage drops on diodes 124, 128 are taken into account, which voltage Vg · is expressed by the equation:

26.3 (R (114) // R (264) + R (118) // R (294)

V_r- = —- (47) (R (114) // R (264) + R (118) // R (294)) + R (126)

The symbol // is used to mark parallel to.

Assuming that both resistances R / 264 / and R / 294 / are equal to 1 kOhm, we get - voltage value Vg - equal to 20.19 V. The time constant of the capacitor discharge circuit is equal to:

ϊ = (C (130)) - ((R (114) // R (264) + R (118) // R (294) // R (12ć) (48)

Select the point on the discharge curve over the section where the slope of the discharge voltage curve as a function of time is still significant, i.e. before the time when the curve becomes flat. This reduces possible measurement errors. In the example discussed above, the measurement should be carried out before the voltage drops to 20.19 V. The discharge time is about 295 ms, and the charge time is about 7 s, so that reliable testing can be carried out. It is advantageous if the capacitor 130 is not discharged to a level lower than required for firing the incandescent igniter, i.e. it should not be allowed that even the full discharge level of the capacitor through the switching circuit could be sufficient to ignite the incandescent igniter.

Figure 3B shows that the period between times Tg and Ta is about 25 ms when switching transistors Q1 and Q2, approximately every 2 ms. The period between successive times T0 and T ^, etc. is equal to about 30 ms. if the total discharge time is 295 ms, ten complete resistance testing cycles can be performed during the capacitor discharge process.

Figures 4A and 4B show that if the capacitor discharge time has not yet expired, i.e. before 295 ms, it returns to operation 410, during which the microcomputer 250 introduces a delay of 24.9 ms, before starting a new switching sequence of transistors Q1 and Q2 . If the discharge time has expired, there is a transition from operation 486 to operation 488, during which a capacity check is performed. The capacity check is carried out to determine the Vc voltage and check if the set value ąv has been exceeded, i.e. check that the Vc voltage measured during operation 404 minus the value of the Vc voltage measured in the last sequence is not greater than the set value Δ V.

During operation 490, the charge flag is set and transistors Q1 and Q2 are cut off during operation 492. After this, the capacitor 130 begins to charge.

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During operation 494, it is checked that the capacitor has been checked. If the result of operation 494 is negative, you return to operation 464, during which the indicator is activated, the error is recorded. In programmable non-volatile memory during operation 466, and the time of error occurrence is recorded during operation 468. If the capacitor check has been carried out, the transition from operation 494 to operation 410 occurs, during which the microcomputer 250 introduces a delay.

Figure 3C illustrates a charging cycle in which both transistors Q1 and Q2 are in a nonconductive state for the greater part of each control cycle period and capacitors are charging. The switching sequence of transistors implemented during operation 412 begins. The switching sequence is completed during periods of times T ^, Tf, Tg, T_H and Ti. Other operations are carried out in a similar manner to that described for the discharge cycle. Control tests are carried out during operation 460. If all control tests have been carried out, the resistance values ​​of the resistors are calculated during operation 480. If during operation 470 you are asked if the discharge marker is set, you get a negative response during the charging cycle, during which you go to operation 500, during which you determine whether the charging time has expired or has not expired.

In the given embodiment of the invention, the charging time is about 7 seconds. If the charging time has not yet elapsed, it goes to operation 410 and the cycle is repeated. If the charging time has elapsed, you go to operation 406, during which the discharge marker is set and the cycle · repeats. If resistance calculations are performed every 30 ms, approximately 230 complete resistance checks are performed during the capacitor charging period.

<img file="PL167782B1_D0003.tif" />

26.

3.4

1Γ

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1Ω

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F = g.1

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<img file="PL167782B1_D0007.tif" />

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ο

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167 702

420

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UP Department of Publications. Circulation of 90 copies

Price: PLN 150