JPS62142860A - Ignition timing control device for varying compression ratio internal combustion engine - Google Patents

Abstract

PURPOSE:To always control an ignition timing to an optimum value even if there is a delay in working of a compression ratio control mechanism, by a method wherein, through detection of a combustion maximum pressure and the like representing the actual compression ratio of an internal combustion engine, an ignition timing is controlled by means of a map suitable to a compression ratio. CONSTITUTION:An internal combustion engine 1 has a control mechanism 2 which varies a compression ratio depending upon an operating condition. In this case, a signal responding to switching of the actual compression ratio of an internal combustion engine 1 by means of a set means 3. Additionally, the set value of an ignition timing responding to the ignition timing of the internal combustion engine 1 is computed by a set means 4. Ignition is effected at an ignition timing set by a control device 5. This constitution detects a combustion maximum pressure, representing the actual compression ratio of the internal combustion engine 1, and a displacement sensor signal level, and controls an ignition timing by means of a map suitable to a compression ratio. Thus, even if there is a delay in operation of a compression ratio control mechanism 2 due to control of an oil pressure, an ignition timing can be always controlled to an optimum value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ignition timing control device for an internal combustion engine in which the compression ratio is variable according to operating conditions.

(Prior art) In an Otto cycle internal combustion engine, increasing the compression ratio improves combustion efficiency, improves fuel consumption rate, and increases output. However, increasing the compression ratio can cause knocking. It becomes easier.

Therefore, the compression ratio is made as high as possible without causing knocking. When the compression ratio changes, the required value of the ignition timing also changes, so the ignition timing is controlled according to the compression ratio. Although there are various methods for varying the compression ratio, there is one that mechanically changes the stroke of the piston itself (for example, see Japanese Patent Laid-Open No. 58-91340).

[Problem that the invention seeks to solve]

In devices where the compression ratio can be varied by mechanically changing the stroke of the piston, it is usually driven by a hydraulic mechanism or the like. On the other hand, since ignition timing is purely electrically controlled, the response is faster than a mechanism that changes the compression ratio. Therefore, when changing the compression ratio, the ignition timing changes immediately, but the compression ratio change is delayed, and the ignition timing does not match the compression ratio in a transient state. Therefore, there are problems such as knocking and poor drivability.

The object of the present invention is to achieve compatibility with switching of ignition timing when switching the compression ratio in an internal combustion engine having a variable compression ratio. In addition, as related technology to this invention, Japanese Patent Application Laid-Open No. 60-230
There is No. 522.

[Means for Solving the Problems] In FIG. 1, an internal combustion engine 1 includes a compression ratio control mechanism 2 that varies the compression ratio depending on operating conditions.

The ignition timing control device for an internal combustion engine according to the present invention includes a compression ratio detection means 3 that generates a signal corresponding to switching of the actual compression ratio of the internal combustion engine 1, and a compression ratio detection means 3 that is connected to the compression ratio detection means 3 and is connected to the compression ratio detection means 3 to generate a signal corresponding to switching of the actual compression ratio of the internal combustion engine 1. The ignition timing control device 4 comprises an ignition timing setting means 4 which calculates a set value of the ignition timing, and an ignition timing control device 5 which is connected to the ignition timing setting means 4 and causes ignition to be performed at the set ignition timing.

[For production]

The compression ratio detection means 3 detects whether the actual compression ratio of the internal combustion engine 1 is a high compression ratio or a low compression ratio. The ignition timing setting means 4 sets the ignition timing according to the detected compression ratio, and the ignition timing control device 5 performs control so that the set ignition timing is obtained.

〔Example〕

In FIG. 2, 10 is the main body of a four-cylinder internal combustion engine, and 12
14 is a combustion chamber, 14 is a spark plug, 16 is an intake pipe, and 18 is an air flow meter. 19 is a distributor.

FIG. 3 shows a detailed longitudinal section of the engine of one cylinder, with 20 being a cylinder block, 21 being a cylinder head, 22 being a piston, 23 being a connecting rod, and 2
4 indicates a piston pin, and 25 indicates a crankshaft.

This internal combustion engine has a variable compression ratio mechanism which will be described below. That is, an eccentric bearing 27 is rotatably fitted into an opening 23a formed at the upper end of the connecting rod 23, and the piston pin 24 is inserted into the eccentric bearing 27. The eccentric bearing 27 has a wall thickness that changes in the circumferential direction. A radial lock pin engagement hole 28 is formed in the thickest portion of the eccentric bearing 27. On the other hand, a lock pin storage hole 29 is opened in the radial direction in the opening 23a at the upper end of the connecting rod 23 that accommodates the eccentric bearing 27. The lock pin engagement hole 28 of the eccentric bearing 27 and the lock pin storage hole 29 at the upper end of the connecting rod 23 are located in the illustrated position where the thickest part of the eccentric bearing faces below the connecting rod axis. They are based on each other. lock pin 30
is fitted into the lock pin storage hole 29 and can freely move in and out of the lock pin engagement hole 28.

Two hydraulic passages are installed to move the lock pin 30 into and out of the lock pin engagement hole 28. That is, two arcuate oil grooves 31 and 32 are formed at intervals in the circumferential direction on the inner surface of the opening 23d through which the crankshaft 25 is inserted at the lower end of the connecting rod 23. One oil groove 31 communicates with the lower part of the lock pin storage hole 29 via an oil hole 23e in the connecting rod 23. The other oil groove 32 opens into an arcuate oil groove 34 on the inner peripheral surface of the opening 23a at the upper end of the connecting rod through an oil hole 23f formed in the connecting rod 23 independently of the oil hole 23e. The oil groove 34 is formed in the radial hole 2 formed in the eccentric bearing 27.
It communicates with the upper part of the lock pin engagement hole 28 via 7b.

An oil hole 25a is formed in the crankshaft 25.
One end 25a-1 of a extends to an opening 23d at the lower end of the connecting rod. Therefore, during rotation of the crankshaft 25, the oil holes 25a are alternately communicated with the oil grooves 31 and 32. The other end 25a-2 of the oil hole 25a extends to the opening 20a of the journal portion 20'' of the cylinder block 20. Also in this opening 20a, there are two independent angular arcuate oil holes similar to those described above. Grooves 37 and 38 are formed, and the oil hole 25a is formed in the oil groove 37 while the crankshaft 25 is rotating.
, 38 alternately.

The position of the oil hole 25 is set as follows. That is, during the rotation of the crankshaft 25, the oil hole 25a communicates with the oil groove 37 of the journal part and the oil groove 31 of the connecting rod. Communication between the oil groove 38 and the oil groove 32 of the connecting rod is performed alternately.

The oil grooves 37 and 38 are connected to a high compression ratio oil passage 40 via oil holes 20b and 20C formed in the cylinder block 20.
and a low compression ratio oil passage 41.

In FIG. 2, the inlet 40 of the high compression ratio oil passage 40
a and the inlet 41a of the low compression ratio oil passage 41 are connected to a solenoid-driven hydraulic switching valve 45 via hydraulic piping 43.44.
connected to. The hydraulic switching valve 45 is connected to the high compression ratio oil passage 4
Hydraulic pressure from the oil pump 46 is selectively supplied to the 0 or low compression ratio oil passage 41. 47 is an oil tank. The hydraulic switching valve 45 is driven as follows by a control circuit that will be described later. When the solenoid 45a is demagnetized, the oil pressure from the oil pump 46 is transferred to the pipe 43.
The low compression ratio oil passage 41 is introduced into the high compression ratio oil passage 40 via a pipe 44, while the low compression ratio oil passage 41 is communicated with an oil tank 47 via a pipe 44.

Therefore, the oil pressure is transmitted from the oil hole 20b (Fig. 4) to the oil 137 in the journal portion 20' through the oil hole 25a in the crankshaft 25.
When communicating with the oil groove 31 of the connecting rod 23, the oil hole 23e in the connecting rod 23 acts on the lower end of the lock pin 30. On the other hand, the oil pressure at the upper end of the lock pin 30 escapes to the oil tank 47 through the following path. That is, the lock pin engagement hole 28 is connected to the oil holes 27b and 23.
When the oil groove 32 of the connecting rod 23 communicates with the oil groove 38 of the journal portion through the oil hole 25a of the crankshaft 25 through f, it communicates with the oil hole 20c, and from there, through the passage 41, the piping 44 and the switching It is communicated with a tank 47 via a valve 45. In this way, hydraulic pressure is applied to the lower end of the lock pin 30 and pressure is released from the upper end, so that the lock pin 30 is urged upward toward the lock pin engagement hole 28 and is fitted into the circumference 28. This state is then held by the lock pin 30. In this state, the maximum eccentric part of the eccentric hair ring 27 takes a lower position, so the position of the piston pin 24 becomes relatively high. This is because the effective length of the connecting rod 23 increases, so a high compression ratio is achieved. Set.

When a low compression ratio is to be selected, the solenoid 45a of the hydraulic switching valve 45 is energized. Then, the hydraulic pump 46 is in turn communicated with the low compression ratio hydraulic passage 41 via the piping 44, and the low compression ratio hydraulic passage 40 is communicated with the oil tank 47 via the piping 43. The hydraulic pressure introduced into the low compression ratio hydraulic passage 41 passes through the oil hole 20c, and when the oil groove 38 is communicated with the oil groove 32 by the oil hole 25a of the crankshaft,
It communicates with the oil hole 23f of the connecting rod, and the oil hole 2
7b and acts on the upper surface of the lock pin 30 from the lock pin engagement hole 28. On the other hand, the oil pressure in the lock pin storage hole 29 is communicated from the oil hole 23e to the oil hole 20b when the oil groove 31 is communicated with the oil groove 37 by the oil hole 25a, and from there to the piping 43 and the oil pressure switching valve 45. Through oil tank 4
Hydraulic pressure is released at 7. In this way, hydraulic pressure is applied to the upper end of the lock pin 30 and pressure is reduced at the lower end of the lock pin 30.
0 descends and exits from the lock pin engagement hole 28. Thus, the eccentric hair ring 27 is in a stable state near the top dead center where the most force is applied, with the eccentric portion of Iυ being located on the upper side. Thus, the position of the piston pin 24 is relatively lowered, which reduces the effective connecting rod length and results in a lower compression ratio setting.

As described above, in this embodiment, by providing the eccentric bearing 27 and making the lock pin 30 freely engageable and detachable, a desired high and low compression ratio can be obtained. Note that the compression ratio control mechanism is not limited to this embodiment, and may be any other known mechanism.

According to the present invention, the control circuit 50 drives the variable compression ratio mechanism to obtain the optimum compression ratio by detecting the operating conditions of the engine, and controls the ignition timing by detecting the actual compression ratio. installed (Figure 2).

The control circuit 50 is configured as a microcomputer system, and includes a central processing unit (CPU) 51, a read-only memory (ROM) 52, a random access memory (RAM) 53, a human output port 54, and an A/D converter. 55, and a path 57 connecting these elements.

The following sensor groups are provided to detect engine operating conditions. The distributor 19 is provided with a first crank angle sensor 56 and a second crank angle sensor 57.

The first crank angle sensor 56 is connected to the distributor shaft 19
It is installed facing the detection piece 58 on the crankshaft 15, and generates a pulse signal NE every 30' of the crankshaft 15, for example, which is used to know the engine rotation speed. The second crank angle sensor 57 is a detection piece 5 on the distributor shaft 19a.
9, and the crank angle shaft 15, for example, 720
A pulse signal G is generated every degree, and this serves as a reference signal.

The aforementioned air flow meter 18 generates an analog signal Q corresponding to the amount of intake air introduced into the engine.

A combustion pressure sensor 61 is installed in the combustion chamber 12 of each cylinder (
(See FIG. 3), the sensor 61 generates an analog signal P corresponding to the combustion pressure of each cylinder.

A first crank angle sensor 56 and a second crank angle sensor 57 that generate pulse signals are connected to the input/output port 54, and the NE multiplied signal and the G signal are inputted at predetermined timing. On the other hand, an air flow meter 18 that generates an analog signal
The combustion pressure sensor 61 of each cylinder is connected to an A/D converter 55, and signals from each sensor are sequentially inputted through A/D conversion processing. The combustion pressure sensor 61 of each cylinder is equipped with a peak hold circuit 63 for holding the peak value in the combustion pressure signal, thereby holding the maximum combustion pressure in the - cycle.

The control circuit 50 executes necessary calculations based on the operating conditions detected by each sensor, and outputs a compression ratio control signal and an ignition signal from the input/output port 54. Ignition control device 6
6 consists of an ignition control circuit (igniter) and an ignition coil, and the ignition control circuit is connected to the input/output port 54 to receive and receive ignition signals. On the other hand, the ignition coil is connected to the center electrode of the distributor 19, and high voltage is distributed to the spark plugs 14 of each cylinder according to the rotation of the distribution shaft 19a. The input/output port 54 is further connected to a solenoid 45a of a hydraulic switching valve 45, and compression ratio switching control is executed in accordance with a compression ratio control signal.

The operation of the control circuit 50 will be explained below using a flowchart. The program to realize this operation is in ROM5.
2 is stored in a predetermined area.

FIG. 5 shows a compression ratio control routine. This routine may be a time interrupt routine that is executed at predetermined time intervals. In step 70, the engine rotational speed NE and the intake air amount to rotational speed ratio Q/NE, which is a representative value of the engine load, are input. Engine speed NE is the 1st
It is assumed that calculation is performed using a well-known method from the interval of pulse signals every 30 degrees of crank angle from the crank angle sensor 56, and that the intake air amount to rotational speed ratio Q/NE is also calculated in a separate routine.

In step 71, the compression ratio to be set is determined from the engine rotational speed NE and the intake air amount to rotational speed ratio Q/NE.

That is, in a predetermined area of the ROM 52, there is a map indicating which compression ratio, high or low, should be set for the combination of the rotation speed NB and the intake air amount-to-rotation speed ratio Q/NE. The CPU 51 selects a desired compression ratio from the input actually measured NE and Q/NE.

In step 72, it is determined whether the compression ratio determined in step 71 is a high compression ratio. When the compression ratio to be selected is a high compression ratio, the process proceeds from step 71 to step 73, and the signal level applied from the input/output port 54 to the solenoid 45 of the hydraulic pressure switching valve 45 is turned OFF. Therefore, the hydraulic switching valve 4
5 assumes the right position in FIG. 2, and supplies hydraulic pressure to the inlet 40a of the high compression ratio hydraulic passage 40, and the inlet 41a of the low compression ratio hydraulic passage 41 is communicated with the tank 47.

Therefore, as described above, the lock pin 30 is urged upward, and the lock pin 30 engages with the lock pin engagement hole 28.
The eccentric bearing 27 is held in a position where its maximum eccentric portion faces downward, the effective length of the connecting rod 23 is increased, and the compression ratio is set to be large.

As a result of the map search, if the compression ratio to be selected is a low compression ratio, the process proceeds from step 72 to step 74, where an ON signal is applied to the solenoid 45a of the hydraulic pressure switching valve 45 from the output port 54. Therefore, the switching valve 45 takes the left position in FIG.
7. Therefore, the lock pin 30 is urged downward and removed from the lock pin engagement hole 28. As a result, the eccentric bearing 27 is released from the restraint state, and the maximum eccentricity, which is a stable state, is located on the upper side. In this way, the effective length of the connecting rod 23 is shortened and the compression ratio is set small.

Figure 6 shows the ignition timing control routine, and this routine is performed at T
This is a crank angle interrupt routine that is started when the crank angle sensor 56,57 detects a predetermined crank angle of the angle XA from DC (see FIG. 7(a)). In step 77, the CPU 51 reads the maximum combustion pressure of that cylinder during the previous ignition (before 720'CA). That is, the pressure sensor 61 installed in each cylinder detects the combustion pressure of that cylinder, and the detected waveform is shown in FIG.
c), and reaches its maximum at an angle after compression top dead center (TDC). The peak hold circuit 63 connected to the pressure sensor 61 of that cylinder sequentially updates the peak value in the pressure sensor signal waveform (c) as shown in FIG. 7(d), and finally reaches the maximum combustion pressure. The value P is held in the peak hold circuit 63 until the next ignition, and the fourth
At step 77 in the figure, data on the maximum pressure P obtained as a result of combustion during the previous ignition is A/D converted by the A/D converter 55. Note that after the A/D conversion is completed, the peak hold circuit 63 is reset (R5).

In step 78 of FIG. 6, the reference maximum combustion pressure Pr is calculated from the rotational speed NE and the intake air amount to rotational speed ratio Q/NE.
The calculation of ef is executed. This reference value Pref is set as follows. That is, the compression ratio for the combination of the engine speed NE and the intake air amount-to-rotation speed ratio Q/NE is determined according to the map in step 71 of FIG. The standard maximum combustion pressure values obtained when operating at this set compression ratio are the same for the high compression ratio and the low compression ratio, respectively.

The reference value Prcf is determined to be an appropriate dark value for this standard maximum combustion pressure. For example, the reference value pref is set to an intermediate value between the standard maximum combustion pressure when operating at a high compression ratio and the standard maximum combustion pressure when operating at a low compression ratio. It is determined whether the compression ratio is high or low depending on whether the compression ratio is small.

In step 79, the reference value Pref is corrected by the ignition timing retardation correction amount Δθ. That is, even if NE and Q/NE are the same, the actual ignition timing at that time changes the maximum combustion pressure that can be obtained, so the reference value Pre
will be subject to amendments.

In step 80, it is determined whether the maximum combustion pressure P is greater than the reference value Pref. If the judgment is positive, the compression ratio set by the variable compression ratio mechanism has already been switched to a high compression ratio, or a command to switch to a low compression ratio has been issued, but the switching is still in progress. Show that. In this case, the process proceeds from step 80 to step 81, and from the ignition timing map for high compression ratio, the basic ignition timing θB
The ASE operation is executed. As is well known, the basic ignition timing is a map of ignition timing values suitable for high compression ratios for the combination of rotational speed NE and intake air meter - rotational speed ratio Q/NE, and is actually measured. The calculation of θBASE for NE and Q/NE is performed.

If the determination in step 80 is negative, it means that the compression ratio has already been switched to a low compression ratio, or that the compression ratio is in the middle of switching even if a command to switch from a low compression ratio to a high compression ratio has been issued. means. In this case, the routine proceeds from step 80 to step 82, where calculation of the basic ignition timing θBASE is executed from the ignition timing map for low compression ratio.

As mentioned above, the basic ignition timing is a map of ignition timing values suitable for low compression ratios for combinations of rotational speed NE and intake air amount to rotational speed ratio Q/NE, and is actually measured. N
The calculation of θBASE for E and Q/NE is performed.

In step 83, the ignition timing θ is determined by subtracting the retardation correction amount Δθ from the basic ignition timing θBASE. This correction amount Δθ is a retardation correction due to knocking or the like, and since this correction is not related to the features of the present invention, a description thereof will be omitted.

In step 84, an ignition command is output from the output port 54 to the ignition control circuit 66. Therefore, as shown in Figure 7 (b), the ignition signal rises, and when it falls, a high voltage is generated in the ignition coil and ignition is performed.
It is well known that this is the calculated ignition timing θ.

As described above, in this embodiment, the ignition timing is controlled by detecting whether or not the compression ratio has actually changed by setting the reference value Pref according to the engine operating conditions. It can be controlled to suit the compression ratio.

Furthermore, since the combustion pressure sensor 61 is installed in each cylinder, the state of combustion pressure can be accurately detected in each cylinder, and control delays between cylinders can be dealt with individually.

In the embodiment shown in FIG. 8, a displacement sensor 100 is installed in the cylinder head 21 to detect the compression ratio.
Detects the distance between the top surface and the top surface. The displacement sensor 100 is configured as an eddy current type, for example, and can obtain a signal depending on the distance to the top surface of the piston.

However, when the distance to the top of the piston is small, see Figure 9 (
It becomes a low-level signal as shown in (a), and when the same distance is large, it becomes a high-level signal as shown in (b). Since the position of the top dead center of the piston 22 changes depending on the compression ratio,
The compression ratio can be determined by the level of the displacement sensor 100.

FIG. 10 shows a flowchart of the ignition timing control routine in this embodiment. This routine is a crank angle interrupt routine executed by a signal from the crank angle sensor 56 every 30° CA. In step 104, it is determined whether this 30' signal corresponds to top dead center. If the determination is affirmative, the process proceeds to step 105, where A/D conversion of the signal from the displacement sensor 100 is performed. The signal level from the displacement sensor 100 takes a maximum value at the top dead center obtained every 360 degrees of crank angle as shown in FIG. Shows the current compression ratio. In step 106, A/
The A/D converted value by the D converter 55 is stored in a predetermined area of the memory as the latest compression ratio data. Note that the compression ratio may be detected by averaging the output of the displacement sensor at the top dead center several times in advance.

In step 107, it is determined whether the crank angle at the time of this interruption is the crank angle for ignition. If the determination is affirmative, the process proceeds to step 108, where the output level of the displacement sensor 100 at the latest top dead center input in step 106 is compared with a predetermined value Xo. That is, if the current crank angle is at time p in FIG. 11(a), the output level of the displacement sensor at time q is the latest compression ratio data.

If the determination is affirmative, the compression ratio is determined to be a high compression ratio, and the process proceeds to step 109, where the basic ignition timing θBASE is calculated from a map for high compression ratios. On the other hand, when the determination in step 108 is negative, the compression ratio is determined to be low, and in step 110, the basic ignition timing θBA is determined from the map for low compression ratio.
SE is calculated. In step 110, ignition timing is calculated, and in step 112, an ignition signal is output.

In this embodiment, by detecting the signal from the displacement sensor as a representative value of the compression ratio and controlling the ignition timing, it is possible to obtain the ignition timing that matches the actual compression ratio. Further, by installing a displacement sensor lOO in each cylinder, it is possible to grasp the compression ratio of each cylinder, and it is possible to cope with control delays in each cylinder.

〔Effect of the invention〕

According to this invention, by detecting the maximum combustion pressure representing the actual compression ratio of the engine and the displacement sensor signal level, the ignition timing can be determined using a map that matches the compression ratio.
I can wholesale. Therefore, even if there is a delay in the operation of the variable compression ratio control mechanism due to hydraulic control or the like, the ignition timing can always be controlled to the optimum ignition timing.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of this invention. FIG. 2 is a configuration diagram of an embodiment in which the compression ratio is detected at the maximum combustion pressure. FIG. 3 is a detailed longitudinal sectional view of the combustion chamber portion of one cylinder. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. 5 and 6 are flowcharts showing the operation of the control circuit in FIG. 2. FIG. 7 is a timing chart showing the operation of the control circuit. FIG. 8 is a partial diagram of an embodiment in which the compression ratio is detected by a displacement sensor. FIG. 9 is a diagram explaining what kind of signal can be obtained from the displacement sensor. FIG. 10 shows a flowchart 10 for explaining the operation of the embodiment shown in FIG.
... Engine body 12 ... Combustion chamber 14 ... Spark plug 18 ... Air flow meter 19 ... Distributor 22 ... Piston 23 ... Connecting rod 24 ... Piston pin 25 ... Crankshaft 27... Eccentric bearing 29... Lock bin engagement hole 30... Lock pin 40... Hydraulic passage for high compression ratio 41... Hydraulic passage for low compression ratio 45... Hydraulic switching valve 5.0 ...Control circuit 56,57...Crank angle sensor 61...Combustion pressure sensor 66...Ignition circuit 100...Displacement sensor Fig. 1 Fig. 5 Fig. 8 Fig. 22... Piston +00...・Displacement sensor Figure 9 Figure 10

Claims (1)

[Scope of Claims] 1. In an ignition timing control device for an internal combustion engine having a compression ratio control mechanism that varies the compression ratio according to operating conditions, a signal is generated in response to switching of the actual compression ratio of the internal combustion engine. a compression ratio detection means for detecting a compression ratio; an ignition timing setting means connected to the compression ratio detection means for calculating a set value of ignition timing according to the compression ratio of the engine; An ignition timing control device for an internal combustion engine, comprising an ignition timing control device for controlling the ignition timing. 2. The compression ratio detection means includes a pressure detection means for detecting the maximum combustion pressure of the engine, and a means for determining whether the compression ratio is high or low by comparing the level of the pressure signal from the pressure detection means with a predetermined reference value. An ignition timing control device according to claim 1. 3. The compression ratio detection means consists of a displacement sensor that detects the top dead center position of the piston, and means that determines whether the compression ratio is high or low by comparing the level of the displacement signal from the displacement sensor with a predetermined reference value. An ignition timing control device according to claim 1.