DE3214276A1 - Computer-controlled ignition angle adjustment for spark ignition engines with positive ignition - Google Patents

Abstract

The need to reduce the fuel consumption and to reduce the emission of noxious substances call for the ignition time point adjustment on spark ignition engines with positive ignition to be optimised. This object is achieved in that a conventional ignition system with mechanical components such as centrifugal force adjuster and partial vacuum adjuster is converted into a characteristic diagram-dependent ignition system by means of a computer-defined control pressure on the partial vacuum adjuster, built up via solenoid valves which are also computer controlled, as a function of the engine operating data present at the computer. This characteristic diagram-controlled ignition system permits a freely selectable adaption of the ignition angle to the engine speed and engine loading taking into account further engine-specific operating data. By the use of electronic auxiliary devices such as a microprocessor, whilst maintaining conventional mechanical ignition angle adjustment devices, on the one hand an optimum ignition angle adjustment is achieved and on the other hand the advantages of the proven, service-friendly and operationally reliable ignition angle adjustment devices are preserved. This system is also particularly suitable for retrofitting vehicles currently in operation with conventional spark ignition engines.

Description

Patent description

The invention relates to a computer-controlled ignition angle setting for spark ignition Otto engines.

Method and arrangement or systems for controlling the ignition angle setting on externally ignited Otto engines with a speed-dependent centrifugal adjuster implemented component and a quasi-load-dependent. via differential pressure adjuster realized components are known. The speed-dependent advance of the ignition point is made possible by the design of the centrifugal weights, tension springs and cam tracks of the centrifugal adjuster certainly.

The quasi-load-dependent adjustment of the ignition point is made by the differential pressure between the suction pipe and the external air pressure at the membrane of the Realized vacuum adjuster. Such systems were the previous ones Requirements, in particular for high specific power and adequate fuel consumption, just; the increasing demands for cancellation of fuel consumption and low pollutant emissions make it necessary to optimize the ignition timing. The differential pressure effective in the vacuum adjuster does not have the necessary one clear assignment to the engine load (torque), the engine operating point is not uniquely determined by speed and differential pressure.

More recently, systems are also known that have a computer-controlled Ignition angle adjustment on externally ignited Otto engines as a function of speed, Perform load and other engine operating data. Such systems with map-controlled Ignition timing, partly in connection with map-controlled mixture formation, define the engine operating point compared to the first-mentioned purely mechanical system unambiguous, but due to their complexity they are only the top ones in motor vehicles Price range used.

The maintenance of these fully electronic systems is exclusively specialist workshops reserved, in the event of failure of the electronics a breakdown repair in the conventional way No longer possible.

The invention is therefore based on the object of providing a system of the initially called type to create, which is due to the advantage of the map-controlled ündwinkel setting, combined with the ease of maintenance and operational safety of conventional mechanical systems, as well as reasonable investment costs.

This object is achieved according to the invention in that a conventional Ignition system, its ignition angle adjustment device by means of centrifugal and vacuum adjusters is actuated by a computer-defined control pressure on the vacuum adjuster is converted into a map-dependent ignition system.

This map-controlled ignition enables immediate adaptation the current ignition angle (actual value) to that of the engine speed, load and others current operating parameters, which are stored in the computer's read-only memory Target value of the ignition angle.

Ease of maintenance as well as operational safety are ensured by maintaining conventional centrifugal and vacuum adjusters given, with the control pressure on the vacuum adjuster from a vacuum in the storage tank and the outer one Air pressure is built up via computer-controlled solenoid valves.

If the actual value of the ignition angle is no longer brought to the target value can be identified, this is indicated as a malfunction, transition to conventional Operation is possible by switching over the corresponding pressure lines. Without too this switchover is an operation of the vehicle, albeit under worse conditions, possible because the conventional distributor assigns the Ignition pulse defined for the compression work cycle.

A major advantage of the system according to the invention over known ones conventional ignitions still consists in that by actual value-setpoint comparison and subsequent control process of the ignition angle unaffected by signs of wear is set.

The system according to the invention is in particular also suitable for retrofitting vehicles in operation with conventional Otto engines.

Further advantageous refinements and developments of the invention result from the subclaims.

For a better understanding of the invention, an embodiment is shown below the same described with reference to Fig.l.

The explanation is based on an Otto engine with coil ignition and Carburetor system. It will be understood that the invention can be applied in a corresponding manner Otto engines with other ignition and mixture formation systems, such as injection engines with transistor ignition, is applicable.

In the block diagram of Fig.l, the unit (1) identifies the computer for recording the current operating parameters generated by the engine (2), as well as for Calculation and control of the optimal ignition angle according to the table (54) stored map, effective on the mechan. Vacuum adjuster (3).

The signals are transmitted from the motor (2) to the computer (1) via an analog / digital converter (A / D converter) (10) and trigger circuits (11). The control signals from the computer (1) to the motor (2) and its components takes place via switching amplifier (12). In the UnitCl) shown elements, as well as A / D converter (10), trigger circuits (11) and switching amplifier (12) are expediently built in one assembly, or integrated in components.

The computer (1) is configured from the central processing unit (CPU) (4), the read-only memory (ROM) (5), the read-write memory (RAM) (6) and the Input / output module (I / O port) (7). CPU (4), ROM (5), RAM (6) and I / O port (7) are linked by address, data and control lines.

When the system is started, the CPU (4) starts the program sequence at the start address of the ROM (5) with the data acquisition program (51).

Via the I / O port (7) and the linked A / D converter (10) one after the other the electrical analog signals received via the corresponding sensors the intake pressure (21), the throttle valve position (22) and the engine temperature (24) placed on the input of the A / D converter (10), converted into a digital data word and detected again via the I / O port (7).

With adapted electrical levels of the signals (21), (22), (24) is sufficient the accuracy of an 8-bit A / D converter.

Via inductive or optical pulse generators, attached to the flywheel, on the V-belt drive of the water pump or

Alternator, is due to the positive connection with the Crankshaft or camshaft a pulse at the top dead center of a specific piston obtained, which is advantageous for determining the engine speed (20) from the computer-determined Time interval of two consecutive impulses, as well as the end point of the through Ignition pulse started on the corresponding piston (25), the. Ignition angle assigned Time interval is used.

For the sake of simplicity, the ignition angle is without reference in FIG. 1 with (25) referred to on (20). The position of the starter flap (23) is adjusted accordingly attached switch divided into two areas, thus is a digital signal generated. The digital signals are sent via trigger circuits (11) and an I / O port (7) transferred to the computer (1). The trigger circuits (11) generate on the output side defined voltage level as required for the transfer of the signals to the I / O port (7) are required, and interference voltages on the input side are suppressed. Corresponding protective circuits for the analog inputs of the A / D converter (10) are intended.

The donors discussed above can also be attached to other devices Places realizable.

The recorded analog and digital operating parameters define one certain engine operating point, which in turn is determined by the subsequently running ignition angle program (52) the setpoint value of the ignition angle from the map stored in table form (54) specifies. The specified maps are based on measurements on the respective engine type Engine test bench and in the operated motor vehicle, for the lowest possible specific Fuel consumption in compliance with certain limit values for pollutant emissions, determined. It is useful for various specific driving conditions such as the warm-up phase, Stop-and-go operation, city operation, intercity operation, which is determined by the chronological sequence the registered operating parameter values are recognized, special operating ranges which are not pronounced in the normal map can be controlled via additional maps.

The tables (54) mentioned contain an advantageous embodiment the optimal time intervals between the ignition point assigned to the operating points and top dead center, expressed in time units, which in turn are measured in such a way that that e.g. in the speed range from 800 ... o6400 rpm the number of time units as Numerical values from 0 to 255 can be expressed in one byte. The map is described by a family of support points, arranged in tables (54).

The ignition angle program (52) allows through; corresponding interpolation methods, Intermediate values of the map defined by the interpolation point as time interval setpoint (between Ignition timing and top dead center). If the measured actual value deviates (Time intervals) from the calculated target value by more than an allowed tolerance, the control program (53) changes the control pressure on the mechanical Vacuum adjuster (3) to reduce the deviation between the actual value and the setpoint. The conceded The deviation is adapted to the local slope of the map.

Assuming that the measured actual value of the time interval is smaller than the setpoint calculated for the operating parameters and outside the tolerance range is, the mechan. Vacuum adjuster (3) adjusted in the direction of early ignition will.

This is due to a changed diaphragm deflection of the vacuum adjuster (3) is reached, depending on the embodiment, the control pressure is increased or humiliated; in the following we assume an embodiment in which the Control pressure must be increased.

The control pressure can be changed between the value of the outer Air pressure (35) and the pressure value in the vacuum reservoir (34), this is Connected to the suction pipe via a check valve, so that it is in the storage tank (34) a negative pressure up to the massive amount of that previously prevailing in the intake pipe Value is built up. Due to the large size of the storage container (34) combined with a correspondingly small dimensioning of the connecting line to the control pressure chamber (3), as well as the control pressure chamber (33) itself and the valves (31) and (32), it is ensured that the for increasing the differential pressure in the control pressure chamber (33) (compared to external air pressure) necessary mass flow is realized by connecting the reservoir (34) to the control pressure chamber (33) via the computer-controlled valve 1 (31), with the corresponding position of the also computer-controlled Valve 2 (32), only leads to a slight change in pressure in the reservoir (34). As soon as the differential pressure in the suction pipe exceeds the differential pressure in the control pressure chamber (33) the connection between the two is released by the check valve, so that the pressure builds up again in the reservoir (34).

The control program (53) is via the I / O port (7) and a Switching amplifier (12) the valve l (31) for a time interval that corresponds to the deviation Actual value setpoint (of the time interval between ignition point and top dead center) adjusted is opened. In the method according to claim 1, the cycle is now repeated, wherein again the sequence of the operating parameters via the measured value acquisition program (51) detected, the current setpoint is determined via the ignition angle program (52) and via the control program (53) causes a corresponding change in the control pressure, if the difference between the actual value and the setpoint value exceeds the permitted tolerance range.

Assuming that the measured actual time interval value is greater is than the setpoint calculated for the current operating parameters, outside of the tolerance range, the mechanical vacuum adjuster (3) must point in direction Retarded ignition can be adjusted0 For this purpose, the Control pressure in the control pressure chamber (33) reduced.

Via the I / O port (7), valve 2 (32) is initially connected to the closed valve 1 (31) with the external air pressure (35). Now will by the control program (53) via the I / O port (7) and a switching amplifier (12) the valve 1 (31) again opened for a time interval that corresponds to the deviation Actual value setpoint is adapted.

The switching valve 2 (32) has a lower switching frequency than the touch valve 1 (31).

The duration of one crankshaft revolution, switching time of the valve 1 (31) and transport processes of the gas up to a maximum number of possible cycles per time unit, fits into the timing of the change processes in the vehicle engine.

For example, when a vehicle accelerates from a standstill, as a relatively fast process with several switching processes, a very fast regulation not desirable, because the strong change of the throttle valve position from "open" to "closed", as well as the strong speed and load changes when disengaging or disengaging Engaging the engine-vehicle power transmission, resulting in ignition angle adjustments that are not required. At the same time, this increases the frequency of Switching cycles of the valves (31) and (32), in particular of the touch valve 1 (31), make sense limited. Blank page

Claims (6)

COMPUTER CONTROLLED IGNITION ANGLE ADJUSTMENT FOR EXTERNAL IGNITION OTTO ENGINES Claims 1.) Method and arrangement of a computer-controlled setting of the ignition angle on spark ignition Otto engines, characterized in that by a measured value acquisition program (51) stamped in the memory (5) of the computer (1) via analog / digital converter (10) and trigger circuits (11) digitally on the input / output module (I / O port) (7) pending current measured values of the engine speed (20), the intake pressure (21), the throttle valve position (22), the starter valve position (23), the engine temperature (24) and the ignition angle (25) of the engine (2) are continuously detected, and via a ignition angle program (52) also memorized in the memory (5) of the computer (1) from stored tables (54), which in turn are based on measurements on the engine test bench and determined in the operated vehicle on the respective engine type, for the lowest possible specific fuel consumption in compliance with certain limit values for pollutant emissions, display the optimal ignition angle setting as a function of the applied parameter values, for the current parameter values and specific driving conditions such as the warm-up phase, Stop-and-go operation, city operation, intercity operation, optimal ignition angle (setpoint) is determined, with a deviation of the measured ignition angle actual value from the calculated one Setpoint by more than an allowed tolerance, by one in the computing memory (5) Embossed control program (53) via the I / O port (7) and switching amplifier (12), for a program-specific time interval, the touch valve 1 (31) on the mechanical Vacuum adjuster (3) switched from position "closed" to position "open" so that the differential pressure (compared to external air pressure) in the control pressure chamber (33) increased or. is decreased, depending on the switching valve 2 (32) the control pressure chamber (33) with the storage container (34) which is at maximum negative pressure or with the external air pressure (35) connects, and thus via the known e mechanical Ignition angle adjustment device (36) the ignition angle is adjusted accordingly, and then repeats the cycle beginning with the measured value acquisition (51) and thus the actual value of the ignition angle is continuously readjusted to the target value of the ignition angle will. 2.) Method and arrangement according to claim 1, characterized in that that by a dwell angle program additionally impressed in the memory (5) of the computer (1) (55) a control of the closing duration of the ignition coil primary circuit (37) the I / O port (7) depending on the engine speed (20) and the voltage of the Vehicle battery (28) is made. 3b) Method and arrangement according to claim 1 and 2, characterized in that that by a fuel enrichment program additionally impressed in the memory (5) of the computer (1) (56) one of the engine speed (20), the intake pressure (21), the throttle valve position (22) and the engine temperature (24) dependent mixture enrichment through an I / O port (7) controlled single-stage (38) or multi-stage (38,39) metering valve in the enrichment respectively. Injection pipe done 0 4.) Method and arrangement according to claim 1 to 3, characterized in that the driving speed as further measured values (26) and the fuel consumption (27) are recorded in the measured value recording program (51) and with an adapting program additionally impressed in the memory (5) of the computer (1) (57) when the switch (29) is operated manually under quasi-stationary conditions the ignition angle <in a range around that defined by the ignition angle program (52) Value varies and is set for minimum specific fuel consumption and a corresponding correction value in a battery-backed read-write memory (6) is saved by the adaptation program (57), so that an example-specific Adaptation of the type-oriented tables (54) is made possible. 5.) Method and arrangement according to claim 1 to 4, characterized in that that the known mechanical Xliehkraft ignition angle adjustment is retained and by the pressure-controlled additional adjustment described in claim 1 an optimal ignition angle is set, with readjustment by turning of the ignition distributor the corresponding range of variation of the pressure-controlled, over Actual value-setpoint comparison of the ignition angle realized, additional adjustment established and thus increased operational reliability while maintaining the basic principle of the system is achieved. 6.) Method and arrangement according to claim 1 to 5, characterized in that that the two valves (31) and (32) as a combined valve with three pressure connections to the control pressure chamber (33), to the storage container (34) and to the external air pressure (35) contains, whereby the combined valve in the basic position (both electrical inputs inactive) the pressure lines to (33), (34), (35) are closed and when active electrical input to (31) the components (33) and (34), with active electrical Input to (32) the components (33) and (35) are connected.