JPH0192538A - Compression ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To aim at preventing torque shock due to abrupt change in compression ratio during transition operation of an internal combustion engine by compensating a desired compression ratio such as to reduce the absolute value of the difference between the desired compression ratio of the internal combustion engine and an actual compression ratio thereof. CONSTITUTION:An internal combustion engine 1 incorporates a compression ratio changing mechanism 2 for changing over the compression ratio of the engine over several stages. In this arrangement, there are provided a means 3 for detecting the operating condition of the internal combustion engine 3, and a means 4 for setting a desired compression ratio of the internal combustion engine 1 in accordance with the operating condition detected by means 3. Further, there is provided a means 5 for computing a variation in the difference between the desired compression ration set by the means 4 and an actual compression ratio of the internal combustion engine 1. Further, there is provided a means 6 for compensating the desired compression ratio to decrease the absolute value of the above-mentioned difference. Further, there is provided a means 7 for controlling the compression ratio changing mechanism 2 to obtain the desired compression ratio compensated by the means 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a compression ratio control device for an internal combustion engine in which the compression ratio is variable steplessly or in multiple steps depending on operating conditions.

[Conventional technology]

In an Otto cycle internal combustion engine, increasing the compression ratio improves combustion efficiency, improves fuel consumption rate, and increases output. However, when the compression ratio is increased, knocking becomes more likely to occur.

Therefore, the compression ratio is made as high as possible without causing knocking, and as the compression ratio changes, the required values for the ignition timing and air-fuel ratio also change, so the ignition timing and air-fuel ratio are controlled according to the compression ratio. is also executed. In other words, the compression ratio that does not cause knocking is determined according to the engine speed and operating conditions such as the engine load represented by the intake air amount, intake pipe pressure, throttle opening, etc., and the current compression ratio is determined. A control device for switching the compression ratio to the above-mentioned compression ratio is disclosed, and the ignition timing, air-fuel ratio, or Methods are already known for temporarily controlling the throttle valve in such a way that the torque shock is reduced.

(Unexamined Japanese Patent Publication No. 59-43937, etc.) [Problems to be Solved by the Invention] However, with the method of correcting sudden changes in torque using the various characteristics described above, control delays during transients and errors in adaptation can be avoided. As a result, some torque shock remains, and it cannot be said that drivability has been completely improved.

The present invention has been made in view of the current situation, and it is an object of the present invention to provide a compression ratio control device that fundamentally suppresses torque shock.

[Means for solving problems]

In FIG. 1, an internal combustion engine 1 includes a variable compression ratio mechanism 2 that can change the engine compression ratio steplessly or in multiple steps. The compression ratio control device of the present invention includes an operating condition detecting means 3 for detecting the operating state of the engine 1, and an engine l based on the operating condition detected by the operating condition detecting means 3.
a compression ratio change calculation means 5 for calculating the difference between the target compression ratio and the actual compression ratio; target compression ratio correction means 6 which corrects the target compression ratio to reduce the absolute value of the difference from the actual compression ratio when the value is larger than the target compression ratio; It has a mechanism control means 7 for controlling the above mechanism.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Figure 2 shows an internal combustion engine in which the compression ratio is changed by changing the combustion chamber volume steplessly or in multiple steps depending on the engine load represented by the engine speed and intake pipe internal pressure, for example. This is a partial schematic diagram, in which a sub-cylinder 12 is formed in the upper part of the combustion chamber 10 and projects upward, and a sub-piston 14 that slides inside the sub-cylinder 12 is disposed to control the The piston drive device 18 as a variable compression ratio mechanism receives a command from the circuit 16 and moves the sub-piston 14 up and down, thereby changing the volume of the combustion chamber 10,
That is, the compression ratio is changed steplessly or in multiple steps.

According to this embodiment, the control circuit 16 includes a crank angle sensor 20 for detecting the engine speed NE as an operating condition detection means, and an intake pipe pressure sensor (vacuum sensor) for detecting the intake pipe pressure PM. 22, and the crank angle sensor 20 is connected to the distributor 24.
will be installed on the

In addition to the above-mentioned sensors, the control circuit 16 usually includes, for example, a throttle position sensor 28 connected to the throttle valve 26 for detecting the throttle opening, a cooling water temperature sensor 30 for detecting the temperature state of the engine, and The control circuit 16 is connected to an intake/exhaust temperature sensor (not shown), etc., and the control circuit 16 is controlled based on the operating conditions and external conditions detected by these sensors.
sends a signal to the fuel injection valve 32 and ignition plug 34, and drives the injection valve 32 and ignition plug 34 with an air-fuel ratio and ignition timing corresponding to compression ratio control, which will be described later.

In this figure, 36 is an intake valve, 38 is a piston, and 40 is an intake valve.
indicates a cylinder block, and 42 indicates a cylinder head.

FIG. 3 is a block diagram showing the inside of the control circuit 16 that executes each control as described above. This control circuit 16 is configured as a microcomputer system, and is a central processing unit! (cpU) 44 and read-only memory (R
OM) 46 and random access memory (RAM)
4B, input port 50, output port 52, and A/D
It consists of a converter 54 and a bus 56 connecting these elements. Therefore, the signals from the various sensors mentioned above are sent to the input port 50, and the CPU 44 performs correction calculations for the compression ratio, ignition timing, and fuel injection amount, and determines the operating conditions and external conditions. Fuel injection valve 3 from 52
2. Send a signal to the ignition plug 34 and the piston drive device 18 to control them.

FIG. 4 shows the target compression ratio CRBAS in the present invention.
Compression ratio map (for stepless) used when determining F
It is. As is clear from the figure, in this embodiment, the target compression ratio CRnn5e is determined by a map search based on a combination of the engine speed NE and the intake pipe internal pressure PM (two-dimensional map).

Naturally, this map is not limited to these two characteristics,
In addition to this, throttle opening TA and intake air amount Q/rotational speed NE
It is also possible to use a three-dimensional map that takes into account the following. Further, this compression ratio map is stored in a predetermined area of the ROM 46 in the control circuit 16, and the CPU 4
This is calculated and determined in step 4.

5 and 6 are diagrams conceptually showing the compression ratio control of the present invention. FIG. 5 shows changes in the intake pipe internal pressure PM and compression ratio when the vehicle accelerates suddenly, and FIG. The figure shows changes in the same characteristics during sudden deceleration.

First, with regard to FIG. 5, for example, when the vehicle suddenly accelerates from steady running, the intake pipe internal pressure PM rapidly increases as shown by the solid line A. Accordingly, the target compression ratio CR11A3E corresponding to this change in operating conditions is curved as shown by the dotted line in the compression ratio map of FIG.

However, in general control methods, the control program itself is executed every predetermined time (Δt) or every predetermined crank angle, so the calculated target compression ratio CRIIAS! changes linearly as shown by the dashed-dotted line in the figure, and the target compression ratio CRBASE drops rapidly especially from point a. That is, this determined target compression ratio CRIIA
In the conventional control method in which execution processing is performed as is according to SE, this drop causes a torque shock and causes deterioration of drivability. On the other hand, the control according to the present invention changes the range of change in compression ratio CR per unit time Δt by a predetermined amount (
In the figure, the target compression ratio CRBAsv is kept within α), and the target compression ratio CRBAsv is corrected as shown by the solid line B in the figure, so that there is no so-called sudden change in the compression ratio.

This is also the case during sudden deceleration as shown in FIG. 6, in which the compression ratio is not increased rapidly but increased by a predetermined amount, thereby alleviating the torque shock.

FIG. 7 is a flowchart showing the operation of the control circuit 16 for realizing the control as described above. The program for realizing this operation is stored in a predetermined area of the ROM 46, and this routine is an interrupt routine that is executed at predetermined time intervals or at predetermined crank angles, as in the conventional case.

First, in step SIO, the engine speed NE is read by the crank angle sensor 20, and in the subsequent step 320, the intake pipe internal pressure PM is read from the vacuum sensor 22.
In step S30, the target compression ratio CRI is determined by a map search of the compression ratio map shown in FIG. 4 using these NE and PM.
Calculate 43E.

Next, in step 340, the compression ratio CRoto when this routine was executed last time is read, and the process proceeds to step 350, where the change (difference) in the compression ratio ΔCR'''CRIASI!-C
Rot. Calculate.

Next, in step S60, it is checked whether the change in compression ratio ΔCR determined in step S50 is larger than a predetermined value α (α: positive value). By the way, as shown in Figure 4, compression ratio, when the operating conditions change to the light load side,
Since the target compression ratio CR11A3E will increase,
For example, during deceleration, ΔCR takes a positive value and its absolute value increases.

Therefore, in the case of sudden deceleration as shown in FIG. 6, the determination is YES and the process proceeds to step S70. Then, in step 370, the previous compression ratio CROLD is corrected to be higher by a predetermined value α, and the corrected target compression ratio CRi□,
This is the current target compression ratio.

On the other hand, when the determination in step S60 is No, the process advances to step S80 and it is determined whether ΔCR is smaller than 1 α. This is because ΔCR takes a negative value during acceleration, and in the case of sudden acceleration where the absolute value becomes larger than the predetermined value α (for example, the state shown in FIG. 5), ΔCR becomes -α
Since it is smaller, it is determined Yes, and step 39
It will proceed to 0.

In step S90, contrary to step S70, the previous compression ratio CROLD is corrected to decrease by a predetermined value α, and the corrected target compression ratio CRBASE is used as the current target compression ratio.

The answer is N at step S60 and step S80.

In this case, it is determined that there is no sudden acceleration or sudden deceleration, and therefore there is no torque shock, so the target compression ratio determined in step S30 is not changed and the process proceeds to the next step 5100.

In step 5100, the above-mentioned step S30
, the control circuit 16 controls the compression ratio variable mechanism 2 so that the target compression ratios determined in steps S70 and S90 are achieved.
A signal is sent to achieve the target compression ratio.

Finally, the process advances to step 5110, where the current compression ratio CRIIASt is CROL-loaded into a predetermined area of RAM 4B.
It will be remembered as D and will be returned.

In the case of sudden acceleration/deceleration, in the next flow execution, the compression ratio corrected as described above is further corrected for CROLD, and by repeating this process, it is finally The target compression ratio correction process is executed until ΔCR<α.

The control routine described above suppresses sudden changes in the compression ratio by increasing or decreasing the predetermined value α as compression ratio correction during sudden acceleration and sudden deceleration. On the other hand, FIGS. 8 and 9 show another embodiment of the present invention different from the correction method described above, in which the correction width is set large at the start of sudden acceleration/deceleration, and then the correction width is gradually reduced. This improves the followability of the compression ratio at the start of acceleration/deceleration. Specifically, as is clear from the figure, if sudden acceleration/deceleration starts, the target compression ratio CR1A determined from the current operating conditions
In this method, only half of the absolute value of the difference ΔCR between s1 and the actual compression ratio CROLD is corrected, and this correction is successively repeated thereafter. Therefore, the control routine for executing this correction, as shown in FIG. 10, is basically the same as the control routine in FIG. The compression ratio CR1IAsE is CRotn+ (CRmast
CROLD ) / 2 (during deceleration) and step 5290 to correct the target compression ratio CR□, yu to CROLD (
The only difference is that CROLD CRIA3 is corrected to 2 (during acceleration). [The corrected target compression ratio for both is (CRIIASE +CRotn)/2. ] In this embodiment, the determination value (predetermined value) α′ for determining whether or not the transient state is occurring is set smaller than the predetermined value α used in the control routine in FIG. By ensuring that the compression ratio is corrected up to a certain number of times (3 times in Figure 8.9), the target compression ratio that has been corrected to the target compression ratio that corresponds to the operating conditions after the end of sudden acceleration/deceleration can be smoothly corrected. I'm trying to get closer. In addition, in this regard, in order to further increase the number of times of correction processing, the predetermined value α' should be made as small as possible. Motsu No. 11
A diagram control routine may be used instead. That is, this control routine includes steps 8250 to 8250 in the control routine of FIG.
280 is omitted, and in this case, the correction process is not limited to correction only during sudden acceleration/deceleration, but also during normal acceleration/deceleration. This has an advantage in that it simplifies the program while achieving the object of the present invention of reducing torque shock during transient times. The control routines in Figures 7.10.11 described above are examples in which the present invention is applied to a mechanism that can steplessly switch the compression ratio, but the present invention also applies to multi-step control. The same applies. In other words, in the case of multi-stage control, the first
A compression ratio map as shown in Fig. 2 is used, and all operating regions included in a certain boundary line region have the same compression ratio (for example, CR, etc.).

CR, etc.), so if the target compression ratio determined from the operating conditions during sudden acceleration/deceleration changes over two or more regions from the compression ratio of the sudden acceleration/deceleration section, (for example, CR, → CR4,), the actual compression ratio only needs to change for each region (for example, CR, → CR4,).
I? I-CRZ→CR3→Cl? , , see the arrow in the figure)
. Therefore, in the control flowchart in this case, the compression ratio map in step S30 of FIG. 7 is rewritten, for example, to the multi-stage compression ratio map shown in FIG. If so, α in steps 360 to 90 may be replaced with 1.

Incidentally, in any of the embodiments described so far, it is a matter of course that the fuel injection amount and ignition timing are changed in synchronization with the compression ratio control according to the present invention.

〔effect〕

As described above, according to the present invention, the target compression ratio calculated in response to the operating conditions during the transient,
Since the target compression ratio is newly corrected so as to reduce the absolute value of the difference from the actual compression ratio, torque shock due to sudden changes in the compression ratio is prevented.

Furthermore, since there is no sudden change in the compression ratio, synchronization of the ignition timing and air-fuel ratio becomes easier and control accuracy improves. In addition, even if there are large changes in operating conditions such as short bursts of light, such as continuous acceleration, the fluctuation range of the compression ratio can be kept smaller than before with the above correction, thus preventing extreme hunting of the compression ratio. This also improves the durability of the variable compression ratio mechanism.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the present invention; Fig. 2 is an engine block diagram of an embodiment of the present invention; Fig. 3 is a block diagram of the present invention showing the inside of the control circuit; Fig. 4 is a block diagram of the present invention used in this embodiment. compression ratio map;
Fig. 5 is a diagram conceptually showing the compression ratio control of the present invention during sudden acceleration; Fig. 6 is a diagram conceptually showing the compression ratio control during sudden deceleration; Fig. 7 is shown in Figs. 5 and 6. Flowchart diagram showing the operation of the control circuit that enables compression ratio control; 8th
The figure conceptually shows compression ratio control different from Fig. 5.6 during sudden acceleration; Fig. 9 conceptually shows the same compression ratio control as Fig. 8 during sudden deceleration; Part 10 is 8.9
A flowchart of a control circuit that enables the compression ratio control shown in the figure; FIG. 11 is a simplified flowchart of the flowchart shown in FIG. 10; FIG. 12 is a compression ratio map used in compression ratio multi-step control: DESCRIPTION OF SYMBOLS 10... Combustion chamber, 12... Sub cylinder, 14... Sub piston, 16... Control circuit, 1B... Piston drive device, 20... Crank angle sensor, 22... Vacuum sensor , 24... Distributor, 26... Throttle valve, 28... Throttle position sensor, 30...
・Cooling water temperature sensor, 32...Fuel injection valve, 34・
...Spark plug.

Claims (1)

[Scope of Claims] 1. In a compression ratio control device for an internal combustion engine equipped with a variable compression ratio mechanism capable of changing the compression ratio steplessly or in multiple stages, an operating condition for detecting the operating condition of the engine. a detection means, a target compression ratio setting means for determining a target compression ratio of the engine based on the operating conditions detected by the operating condition detection means, and a compression ratio change for determining the difference between the target compression ratio and the actual compression ratio. calculation means; target compression ratio correction means for correcting the target compression ratio to reduce the absolute value of the difference from the actual compression ratio when the absolute value of the difference is greater than a predetermined value; A compression ratio control device for an internal combustion engine, comprising mechanism control means for controlling the mechanism to a target compression ratio corrected by a target compression ratio correction means.