Automatic OZ angle regulator on K1816BE31. Encyclopedia of radio electronics and electrical engineering

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Devices designed to automatically maintain the ignition timing (OZ) of an internal combustion engine at an optimal level are still quite complex. They can be simplified by using microcircuits with a high degree of integration. One example of this is shown below.

The most obvious way to improve the most important indicators of a gasoline internal combustion engine is to replace the centrifugal OZ angle regulator with an electronic one with manual, and even better, with automatic control. Similar electronic regulators have already been described in the journal [1; 2].

Based on the device [2], I developed a simpler automatic angle controller O3. Simplification was achieved using the K1816BE31 microcontroller. The presence of two digital sixteen-digit timers in it allows you to continuously and simultaneously measure the crankshaft speed and control the OZ angle. Unlike the prototype, the breaker contacts remain in the position of the initial angle 03, as for a mechanical centrifugal regulator, which ensures a normal ignition mode during engine start.

The automatic regulator is designed to work with a contact interrupter and an electronic ignition system. The spark delay relative to the moment of opening the contacts is equal to the difference between the sparking period (Ti - 1 / fi, where fi is the frequency of opening the breaker contacts) and the ignition advance time (corresponding to the angle OZ at a specific engine crankshaft speed).

The calculation of the moment of sparking is repeated every half-turn of the crankshaft, which practically ensures the inertia of the regulator. It also provides for the introduction of a temporary correction by an octane corrector, which sets both the value and the sign of the correction. Depending on the position of the throttle valve of the carburetor and the engine speed, the economizer solenoid valve is controlled according to a standard algorithm.

The schematic diagram of the digital controller is shown in fig. 1. The device consists of a processor unit, an input shaper, an output unit, an octane corrector, an economizer solenoid valve control unit, a voltage stabilizer and a galvanic isolation circuit from the microswitch contacts.

(click to enlarge)

The main element of the processor node is a single-chip microcontroller DD1, included according to a typical scheme with external memory (it stores programs). The microcontroller is clocked by the built-in oscillator, the frequency of which is set by the ZQ1 quartz resonator. Chip DD3 - latch low byte address.

The shaper, consisting of an input amplifier on a transistor VT1, a single vibrator on the elements DD2.1, DD2.4 and a trigger DD2.2, DD2.3, is assembled according to the scheme from [2] and is designed to eliminate the consequences of the bounce of the breaker contacts and supply a low-level signal to the input P3.2 of the controller when the breaker contacts are opened. The shaper input is connected to the car engine breaker.

Switch SA1 allows you to turn off the automatic regulator and send a signal from the interrupter directly to the ignition unit. This, in particular, makes it possible to start the engine with a heavily discharged battery, when the voltage of the on-board network is insufficient for normal operation of the machine.

The octane corrector includes switches SB1, SA2 and an encoder on diodes VD8-VD22. Correction of the moment of sparking is discrete, with a software-set step of 0,7 degrees. Depending on the position of the switch SA2, the signal in the binary inverse code through the diodes enters the inputs P1.0-P1.3 of the microcontroller and sets the number of correction steps for it. From the switch SB1 to the input P1.6 of the controller, a signal is received that determines the sign of the correction. It is determined by software that the open contacts of this switch correspond to an increase, and the closed contacts correspond to a decrease in the ignition timing relative to the nominal value.

The output node is assembled on a single vibrator DD4.1, DD4.3 with an amplifier based on transistors VT3, VT5 according to the scheme from [1] and is designed to generate positive polarity pulses with an amplitude of 12 V and a duration of 500 μs to start the electronic ignition system. If the output of element DD4.1 is connected to the inputs of a free element DD4.4 (not shown in the diagram), then a pulse sequence can be removed from the output of element DD4.4 for feeding to an electronic tachometer.

The electrovalve control unit is assembled on the element DD4.2 and transistors VT2, VT4 according to the scheme from [3]. A low logic level at the output P3.5 of the controller, after being inverted by the element DD4.2, opens transistors VT2, VT4. Through the open transistor VT4, a voltage of 12 V is supplied to the winding of the solenoid valve, which controls the flow of fuel into the engine carburetor.

A node is assembled on relay K1, which provides galvanic isolation of the microcontroller input from the contacts of the sensor-microswitch, which is installed on the carburetor and is mechanically connected to the throttle. When the damper is open, the sensor contacts are closed and a voltage of 1 V is applied to the relay winding K12. Through the closed contacts K1.1 of the relay, a low logic level is applied to the input P1.7 of the controller, informing it about the opening of the throttle.

The auto-regulator is powered by the car's on-board network. Through the input filter L1C13, the DC voltage is supplied to the DA1 stabilizer, from the output of which a voltage of 5 V is supplied to microcircuits and other nodes. The regulator turns on simultaneously with the ignition of the car.

When the supply voltage is applied, the capacitor C6 is charged through the resistor R8, generating a reset signal, according to which the controller DD1 goes into its initial state and performs preparatory operations. First, it sets a low level at the output P3.5, which, after being inverted by the DD4.2 element and amplified by the transistor VT2, opens the transistor VT4, and the voltage of the on-board network is supplied to the solenoid valve winding, thereby allowing fuel to be supplied to the engine carburetor.

Secondly, a low-level pulse at the lower input of the DD2.2 element according to the circuit sets the trigger DD2.2, DD2.3 to its initial state, in which the output of the DD2.2 element is high, and the output of the DD2.3 element is low . Thirdly, it enables a low-level interrupt at input P3.2.

Fourth, sets the internal timers - TO and T1 counters to 16-bit mode and enables the interrupt from the internal timer T1. The controller timers are organized so that their state is incremented by 1 after 12 oscillator cycles. At a clock frequency of 12 MHz, the timer state increments after 1 µs, which makes it possible to measure a period of no more than 65535 µs, which corresponds to an engine crankshaft speed of at least 457 min-1. When the timer transitions from the "all ones" state to the "all zeros" state, an overflow flag is set in a special register of the controller, according to which, if the interrupt is enabled, the controller executes the corresponding subroutine servicing this interrupt.

Next, the controller resets the timers, starts the timer TO count and goes into the waiting mode for a low level at input P3.2. Thus, the digital controller is ready to start the engine.

At the first opening of the breaker contacts at the output of the single vibrator DD2.1, DD2.4, a pulse with a duration of 500 μs will be generated, which, after differentiation by the C7R11R12 circuit, will switch the trigger DD2.2, DD2.3 and a low level will be set at the output of the element DD2.2. Entering the input P3.2 of the controller, it will call the appropriate interrupt service routine, which stops the TO timer, saves its state, performs the initial setting and restarts in counting mode. After that, the stored value of the maintenance timer is analyzed.

When the engine is started, the crankshaft speed is less than allowed for measurement, therefore, the maintenance timer overflows. Under this condition, the controller without delay will generate a short low-level pulse at the output P3.4, which will start the single vibrator DD4.1, DD4.3. A low-level pulse with a duration of 500 μs, generated at the output of a single vibrator, will close the transistors VT3, VT5 and start the electronic engine ignition system. After that, the controller with a low-level pulse to the lower input of the element DD2.2 sets the trigger DD2.2, DD2.3 to its original state and again goes into standby mode for the next trigger switching.

When the crankshaft speed exceeds 457 min-1, the maintenance timer overflow no longer occurs and the controller analyzes the sparking period when executing the interrupt processing routine at input P3.2. In accordance with the characteristics of the mechanical regulator P147B, shown in fig. 2 (N - crankshaft speed).

On its horizontal section from zero to point 1, the device generates output pulses without delay, i.e. at the moment of opening the breaker contacts, in section 1 - 2, the controller calculates the necessary delay in the formation of the ignition pulse according to the formula

tset = (tmeas - φoz tmeas/180) - tcalc ± tcorr,

where tzad - ignition delay time, μs; tmeas - time between two adjacent openings of the breaker, µs; φoz - the value of the ignition advance angle at a specific engine crankshaft speed, degrees; tcalc - the time elapsed from the moment of opening the contacts of the interrupter to the end of the calculation of the ignition delay, μs; tcorr - time correction (ignition correction), depending on both the position of the octane-corrector switch and the correction sign switch, μs.

The resulting delay value is subtracted from 65536, the result fixes the timer T1, after which it starts and the contents of the timer begin to increase by one every microsecond.

Simultaneously with the completion of the calculation of the ignition delay, the controller turns on or off the solenoid valve depending on the position of the throttle valve of the carburetor and the speed of the engine shaft. When the throttle is open, the controller constantly maintains a low level at the P3.5 output, thereby allowing fuel to be supplied to the carburetor.

When it is closed, relay K1 releases the armature, contacts K1.1 open and a high level is applied to input P10 of the controller through resistor R1.7. The controller compares the measured sparking period with software-defined time thresholds and opens or closes the valve accordingly. These time thresholds correspond to those set in the economizer control unit, which was mounted on the vehicle.

After the completion of the interrupt routine at input P3.2, the controller sets the trigger DD2.2, DD2.3 to its initial state and waits for the interrupt signal from the timer T1.

After a certain time, the timer T1 overflows, and it generates a request to process the interrupt vector. The controller executes the corresponding subroutine, stops the timer T1, starts the single vibrator DD4.1, DD4.3 with a low-level pulse. The closed transistor VT4 will generate a starting pulse for the ignition unit. After completing the subroutine, the controller again waits for a low level to enter P3.2.

Since the breaker contacts open every half-turn of the engine crankshaft, the time measured by the TO timer in each cycle corresponds to 180 degrees. The measured time is programmatically divided by 256 (a result corresponding to 0,7 degrees is obtained) and multiplied by the code entered from the encoder on VD8-VD22 diodes. As a result, the ignition delay correction time tcorr is obtained, which is taken into account in the final calculation of the ignition delay with the corresponding sign. Switch SA2 correction angle OZ can be changed in the range from 0 to +6,3 or from 0 to -6,3 degrees, which correspond to the upper and lower dashed broken lines in Fig. 2.

The use of the inverse code makes it possible to reduce the number of diodes in the encoder. When setting a minus correction angle, the controller characteristic is limited by software so that the resulting OC angle cannot take negative values.

Let us consider the formation of the characteristics of the automaton-regulator (the same as that of the centrifugal regulator), shown in Fig. 2 (thick broken line). In a centrifugal regulator, this form of characteristic is set by two springs of different stiffness, which come into action one after the other with an increase in the frequency of rotation of the chopper shaft. The line consists of four sections.

On the first section from the origin to point 1, the angle 03 is equal to zero. The remaining three sections - 1-2, 2-3 and 3-4 - are approximated by straight lines and are expressed by a system of three linear equations for the dependence of the angle O3 on the crankshaft speed, which is generally described by the formula φoz = K (N - N0) + φbegin, where φoz is the current angle of the OZ, degrees; N - current frequency of rotation of the engine crankshaft, min-1; N0 - rotation frequency at the starting point of the section, min-1; K - coefficient taking into account the angle of inclination of the site to the N axis; φbegin - the initial angle of the OZ for the site, deg.

Substituting these three equations for each section into the formula for tset and performing transformations, we obtain a system of three linear equations with the dependence of the delay time of the moment of sparking on the measured time interval between two adjacent openings of the interrupter:

tset = (tmeas K1/256 - B1) - tpasch ± tcorr (for section 1-2);

tset = (tmeas K2/256 - B2) - tpasch ± tcorr (for 2-3);

tset = (tmeas K3/256 - B3) - tpasch ± tcorr (for 3-4),

where K1, B1, K2, B2, K3, B3 are the calculated coefficients for the corresponding sections of the characteristic.

To determine these coefficients, a program (Table 1) was written in the Q-Basic programming language.

The initial parameters for it are the characteristics of the centrifugal regulator of the breaker-distributor R147V of the Moskvich-2140 car, from the technical description [4] - the angle of rotation and the rotational speed of the engine crankshaft (not to be confused with the rotational speed and its rotation is half that of the crankshaft) at points 1, 2, 3 - table. 2.

In table. 3 summarizes the results of the calculation for the indicated program. The value of the crankshaft speed of 6000 min-1 is conditionally taken as the maximum, since the section from point 3 is horizontal. To simplify the control program of the controller, the values ​​of the period of sparking at the beginning of the sections of the characteristic are taken equal to the nearest multiple of 256.

In table. 4 shows the codes of the program, which is placed in the ROM DS1; it ensures the operation of the controller DD1.

With this program, the automatic regulator is similar in characteristics to the R147V breaker-distributor and the economizer control unit 252.3761 of the engine of the Moskvich-2140 car, designed to use A-76 gasoline. The thresholds for switching on and off the electrovalve according to the frequency of rotation of the crankshaft are taken equal to 1245 min-1 and 1500 min-1, respectively [5]. The addresses of the program, in which information is entered that determines the characteristic of the regulator, are indicated in Table. 5 and 6.

The content in the program is written in a two-byte hexadecimal code, except for the sparking period at the beginning of the corresponding sections (T1, T2, T3), which are represented only by the high byte. The thresholds for switching the electrovalve from frequency to time form (Table 6) are recalculated according to the formula tpor = 3 107/Npor, where tpor is time in µs; Npor - speed in min-1.

To use the machine with other centrifugal regulators and economizer control units, their characteristics are substituted into the calculation.

The automatic regulator is assembled on a technological board with dimensions of 130x85 mm. Connections are made with MGTF wire. Switches SA1, SA2, SB1 are installed on the front panel of the regulator. If it is not necessary to control the solenoid valve, the elements R13-R15, R18, R19, VT2, VT4, VD6, VD7, K1 can be omitted. The view of the device with the cover removed is shown in Fig. 3.

As a microcontroller, any microcircuit from the Intel51 family (180x31, 180x51, 180x52) or their domestic counterparts (K1816BE51, for example) is suitable.

A regulator made of serviceable parts and without errors does not need to be adjusted. Recommendations for replacing elements and checking the performance are set out in [1-3]. The adjustment limits for the correction of the OZ angle can, if desired, be increased to ± 10,5 degrees by using the SA2 switch for 16 positions with the addition of the appropriate number of diodes to the encoder. It is also possible to use an encoder in the form of a switch for 4 directions and 10 or 16 positions, as in [1].

The regulator is mounted on the dashboard of the car and connected to the breaker, ignition unit, solenoid valve and sensor on the carburetor with a shielded cable.

Before installing the electronic regulator, fix the crackers of the centrifugal regulator in their original position. The moment of opening the contacts of the breaker must correspond to the initial angle of the OZ. The breaker capacitor must be disconnected.

When installing the automatic regulator on cars with a screw sensor installed on the carburetor (its contacts are closed when the throttle is closed), it is necessary to connect the resistor R10 to the closed contacts of relay K1.

Although the device is designed to work with a contact breaker and an electronic ignition system, with the appropriate refinement of the input driver and output unit, it is able to work with a contactless breaker and other types of ignition unit.

The source text of the program for K1816BE31

Literature

1. Biryukov A. Digital octane corrector. - Radio, 1987, No. 10, p. 34-37.
2. Biryukov A. Digital automat-regulator of the OZ angle. - Radio, 1999, No. 1, p. 46-48; No. 2, p. 40,41.
3. Bannikov V. Improved economizer control unit. - Radio, 1991, No. 8, p. 28-31.
4. Gorelov N. S. et al. Cars "Moskvich" models 2140, 2138: Repair. - M.: Transport, 1993, p. 234.
5. Bannikov V. Replacement of economizer control units. - Radio, 1989, No. 8, p. thirty.

Author: A. Obukhov, Perm

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