JPH0616995Y2 - Ignition timing control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an ignition timing control device for an internal combustion engine, which controls a peak position of combustion pressure to a predetermined value determined by an engine state.

[Conventional technology]

Japanese Patent Publications Nos. 49-29209 and 56-21913 propose devices for controlling the ignition timing so that the peak position of the combustion pressure reaches a predetermined value at which the maximum torque can be obtained. in this case,
Control of ignition timing is generally performed by an electronic control device using a microcomputer. The peak position of the combustion pressure is detected at a predetermined crank angle (for example, every 1 ° CA).
It is performed by detecting the combustion pressure and observing the change in the combustion pressure. Then, the ignition timing is feedback-controlled so that the peak position of the combustion pressure becomes a predetermined crank angle.

In the prior art, in order to accurately detect the peak position of the combustion pressure, it is necessary to make the crank angle interval for detecting the combustion pressure as short as possible. However, this is limited by the time constraint associated with A / D conversion processing of the signal from the pressure sensor and the time constraint required for other arithmetic processing. As a result, there is a problem that sufficient peak position detection accuracy cannot be obtained. In particular, when processing is performed in a plurality of cylinders or in a high engine speed region, the interval for measuring the combustion pressure cannot be relatively short, so that there is a large problem of deterioration in accuracy.

Therefore, in Japanese Patent Application No. 60-194764, the difference in combustion pressure is detected at a pair of crank angle positions that are close to each other with the crank angle exhibiting the peak of combustion pressure being sandwiched, and the ignition timing is controlled so that the difference becomes a predetermined value. Are proposing things. That is, this pressure difference means the deviation of the actual peak position of the combustion pressure from the peak position of the combustion pressure when ignition is performed at the optimum ignition timing, that is, the deviation of the actual ignition timing from the optimum ignition timing. Therefore, the MBT advance angle can be obtained by controlling the ignition timing so that the pressure difference becomes a predetermined value. At this time, even if the ignition is performed with the MBT advance angle, the peak position of the combustion pressure is somewhat different depending on the rotation speed and the load. Therefore, the predetermined value of the pressure difference is changed according to the rotation speed and the load.

[Problems to be solved by the invention]

As described above, strictly speaking, the crank angle value (θ _pmax ) at the optimum ignition timing (MBT) is not constant but changes depending on the engine operating conditions (that is, engine speed and load). In this case, if there is a change in the sensitivity of the pressure sensor, the peak position will deviate even if the pressure difference at the two points is the same, making it impossible to control the peak position accurately.

The idea is to obtain the optimum peak position without being affected by the fluctuation of the sensitivity of the pressure sensor.

[Means for solving problems]

The ignition timing control device for an internal combustion engine according to the present invention, as shown in FIG. 1, includes a combustion pressure detecting means 2 for detecting the combustion pressure of the internal combustion engine 1 and a pair of combustion pressure detecting means 2 which are close to each other with a crank angle exhibiting a peak of the combustion pressure interposed. Timing means 3 for detecting the crank angle position, combustion pressure difference calculation means 4 for calculating the difference between the measured combustion pressures at the pair of crank angle positions, means 5 for calculating the target value of the combustion pressure difference, and combustion pressure difference. 6 for calculating the ignition timing according to the difference between the target value and the measured value of
An engine for generating an ignition signal so that ignition is executed at the calculated ignition timing, and at least one of a pair of timings detected by the timing detection means 3 so that the pressure difference becomes zero at the optimum ignition timing. And a means 8 for making correction according to the operating conditions.

〔Example〕

FIG. 2 shows an internal combustion engine in the embodiment, 10 is a cylinder block, 12 is a piston, 14 is a connecting rod, 16 is a cylinder head, 18 is a combustion chamber, 2
Reference numeral 0 is an intake valve, 22 is a spark plug, 24 is a distributor, 26 is an ignition coil, and 27 is an igniter. A pressure sensor 28 for detecting combustion pressure is arranged in the combustion chamber 18. The first crank angle sensor 30 and the second crank angle sensor 32 are installed on the distributor 24.
On the other hand, the first magnet member 36 and the second magnet member 38 are arranged on the distribution shaft 34 of the distributor 24. The first magnet member 36 has a magnet portion at one position on its circumference, and the first crank angle sensor 30 which is a Hall element generates a pulse signal for each rotation of the distribution shaft (corresponding to 720 ° CA). The second magnet member 38 has a plurality of magnet portions on its circumference, and generates a pulse signal for each small crank angle (for example, for each crank angle of 1 °).

The control circuit 40 controls the ignition timing and is configured as a microcomputer system. The control circuit 40 includes a micro processing unit (MPU) 42, a memory 44, an input interface 46, an output interface 48, and a bus 50 connecting them. The pressure sensor 28 is connected to an analog-digital (A / D) converter (not shown) of the input interface 46, and inputs a signal according to the combustion pressure. The first crank angle sensor 30 and the second crank angle sensor 32 are connected to the input interface 46, and a pulse signal for each 720 ° CA, 1 ° C.
The pulse signal for each A is input.

The output interface 48 is connected to the igniter 27,
An ignition signal is applied.

FIG. 3 is a diagram showing a change in combustion pressure with respect to a crank angle, which has a peak at a crank angle slightly beyond the top dead center in the compression stroke. The position of this crank angle is substantially constant, but strictly speaking, it changes depending on operating conditions such as the load of the engine. In the conventional method, two points θ ₁ and θ ₂ that are symmetrical with respect to a certain reference crank angle position θ _X are taken, and
The difference in combustion pressure is measured at each point. If the crank angle at the peak of the combustion pressure (solid line) when ignited at the optimum ignition timing is θ _X , the pressure difference P between θ ₁ and θ _2
1 -P ₂ is zero. When the operating condition changes, the combustion pressure characteristic changes as shown by the broken line, and even if ignition is performed at the optimum ignition timing, the peak position shifts, and the pressure difference at that time P ₁ -P ₂
Is no longer zero. Therefore, as shown in FIG. 4, the pressure difference P ₁ − at two points θ ₁ and θ ₂ that sandwich the peak of the combustion pressure in the combustion pressure characteristic when ignition is performed at the optimum ignition timing.
The target value of P ₂ is set at each load is the actual during operation and controls the P ₁ -P value ignition timing so as to obtain a ₂ determined in the load. However, if the crank angle positions θ ₁ and θ ₂ for sampling the combustion pressure are fixed in this way, it becomes impossible to optimally control the combustion pressure peak position when the sensitivity of the pressure sensor changes. For example, assuming that the sensitivity is high as shown by the solid line in FIG. 5A and the sensitivity is low as shown by the broken line, the pressure difference P ₁ -P ₂ at θ ₁ and θ ₂ is Although it is the same as a, there is actually a difference of b between the peaks of both combustion pressures. Thus, if the crank angle position for sampling is fixed as in the conventional case, the combustion pressure peak position cannot be accurately controlled.

Therefore, in this invention, the sensitivity of the sensor is not affected by changing at least one of the two sampling positions θ ₁ and θ ₂ so that the combustion pressure difference P ₁ −P ₂ is always zero. It is a thing. That is, in FIG. 5 (b), in the present invention, at least one of θ ₁ and θ ₂ is changed according to the engine operating condition so that the pressure difference P ₁ −P ₂ = 0. Therefore, even if the sensitivity of the pressure sensor changes between the solid line and the broken line, the peak position is not affected by it.

A flow chart of ignition timing control that realizes the above-described principle of the present invention will be described.

FIG. 6 shows a crank angle interrupt routine executed each time a signal from the second crank angle sensor 32 arrives at every 1 ° CA. In step 60, the counter m is incremented. In step 62, it is determined whether or not there is a 720 ° signal from the first crank angle sensor 30, and if Yes, the process proceeds to step 64 and the counter m is reset.
That is, as shown in (a) of FIG. 9, a pulse signal for every 720 ° CA is obtained from the first crank angle sensor 30, and the counter m is reset at every arrival (b). Therefore,
The value of the counter m monotonically increases in the range of 720 ° CA.

In step 66 of FIG. 6, it is determined whether or not the value of the counter m has reached the value m ₁ corresponding to the crank angle θ ₁ . See FIG. 9 (c). If Yes, the routine proceeds to step 68, where the A / D conversion of the signal from the pressure sensor 28 is executed, and the value is transferred to the memory area for storing P ₁ .

In step 70, another sampling position θ ₂ is calculated. θ ₂ is the position where the pressure difference P ₁ -P ₂ is zero across the combustion pressure peak as described above, and is determined by the load and the rotational speed. FIG. 8 shows such a relationship of θ ₂ . From this relationship, the data of θ ₂ for the combination of the load and the rotation speed is stored in the memory 44 as a table, and the value of θ ₂ for the combination of the measured load and the rotation speed is calculated by interpolation. . In step 72, the time from the present time until the crank angle of θ ₂ is reached is calculated from the engine speed, and the time is set in the timer.

When this time arrives, that is, when θ ₂ is sampled, the time coincidence interrupt routine of FIG. 7 is started. In step 72, A / D conversion of the signal from the pressure sensor 28 is executed, and the value is transferred to the memory area for storing P ₂ . At step 74, it is judged if the combustion pressure difference between the crank angles θ ₁ and θ ₂ is P ₁ −P ₂ > h. If Yes, the routine proceeds to step 76, where the ignition timing is controlled to the delayed side. If No in step 74, the process proceeds to step 78 and it is determined whether or not P ₁ -P ₂ <h. If Yes, the routine proceeds to step 80, where the ignition timing is controlled to the leading side. | P
_{When 1−} P ₂ | <h, it is determined that the dead zone is in effect, and the ignition timing is left unchanged.

By such feed back control of the ignition timing, the crank angle position at which the combustion pressure peaks is maintained at the optimum value according to the operating condition.

[Effect of device]

In this invention, each combustion pressure is A / D converted at two crank angles which are relatively close to each other after the compression top dead center,
And at least one of the two crank angles is changed according to the engine operating conditions, and the ignition timing is feedback controlled so that the pressure difference becomes zero, so that the combustion pressure is not affected by the sensitivity of the pressure sensor. The peak position of is controlled to the optimum position. Furthermore, pressure sampling Q
_1, since Q ₂ relates two points is not fixed, there is no influence of variation in precision between the fixed points.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of this invention. FIG. 2 is a diagram showing an embodiment of this invention. FIG. 3 is a relationship diagram of the crank angle and the cylinder pressure. FIG. 4 is a graph showing the relationship between the load and the target value of the pressure difference in the prior art. FIG. 5 is a graph for explaining the influence of the sensitivity of the pressure sensor in the conventional (a) and the present invention (b). 6 and 7 are flowcharts for explaining the operation of the control circuit. FIG. 8 shows the sampling angle θ _{2 with} respect to the load and the rotation speed.
A graph that explains the change in. FIG. 9 is a timing chart explaining how to set the crank angle for measuring the combustion pressure. 18 ... Combustion chamber, 22 ... Spark plug, 24 ... Distributor, 26 ... Ignition coil, 27 ... Igniter, 28 ... Pressure sensor, 30 ... First crank angle sensor, 32 ... Second crank angle sensor, 40 ... Control circuit.

Claims (1)

[Scope of utility model registration request] 1. An ignition timing control device for an internal combustion engine comprising the following components, a combustion pressure detecting means for detecting a combustion pressure of the internal combustion engine, and a pair of crank angle positions close to each other with a crank angle exhibiting a peak of the combustion pressure sandwiched therebetween. Detecting means, a combustion pressure difference calculating means for calculating a difference between the measured combustion pressures at the pair of crank angle positions, a means for calculating a target value of the combustion pressure difference, and a difference between the target value of the combustion pressure difference and the actually measured value. The means for calculating the ignition timing, the means for forming the ignition signal so that the ignition is executed at the calculated ignition timing, and the pair of timings detected by the tamming detection means for the pressure difference at the optimum ignition timing. A means for correcting the operating condition of the engine so that it becomes zero.