JP4325507B2 - COMPRESSION RATIO CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE - Google Patents

Description

  The present invention relates to a compression ratio control device for an internal combustion engine capable of operating an engine compression ratio.

As disclosed in Patent Document 1, a variable compression ratio mechanism capable of operating a compression ratio of an internal combustion engine has been conventionally known. When such a variable compression ratio mechanism is provided, the fuel consumption rate can be improved while avoiding knocking by setting the engine compression ratio as high as possible within a range in which knocking can be avoided. Therefore, in general, knocking is more likely to occur as the required load increases, so the engine compression ratio is lowered, and the engine compression ratio is increased as the required load decreases.
JP 07-229431 A

  However, depending on the engine operating state, the fuel efficiency improvement effect due to the increase in the engine compression ratio is not always obtained. In other words, in order to change the engine compression ratio, drive energy is inevitably required by an electric or hydraulic actuator. Therefore, if the compression ratio is increased or decreased frequently, a lot of energy is consumed in the operation of the compression ratio. End up. As a result, the improvement in fuel efficiency obtained by increasing the compression ratio is offset or reduced by the energy consumption resulting from the operation of the compression ratio, and the expected improvement in fuel efficiency cannot be obtained. As a result, the reliability and durability of the mechanism, motor, etc. for manipulating the compression ratio may be reduced.

  More specifically, in the low load range, it is difficult to obtain the fuel efficiency improvement effect accompanying the increase in the engine compression ratio compared to the high load range. There is a tendency (see FIG. 14). Therefore, in a high load range, the target compression ratio varies relatively greatly with respect to the driver's accelerator operation, and the compression ratio is likely to change frequently. For this reason, problems such as a decrease in fuel efficiency improvement effect and a decrease in reliability and durability of the compression ratio operation system as described above are likely to occur.

  Thus, for example, it is conceivable to intentionally delay or slow down the change of the compression ratio so that the compression ratio is not frequently manipulated. However, when the compression ratio is reduced, if the reduction is intentionally delayed, the compression ratio becomes transiently too high, which may cause knocking.

  The present invention has been made in view of such problems, and has as its main object to provide a novel compression ratio control device for an internal combustion engine that can stably and efficiently operate the engine compression ratio.

An internal combustion engine compression ratio control apparatus according to the present invention includes:
A required compression ratio calculating means for calculating a required compression ratio based on the engine required value corresponding to the required load or the required torque;
Target compression ratio setting means for setting a target compression ratio based on the required compression ratio;
Compression ratio operating means for operating the engine compression ratio toward the target compression ratio,
And, the target compression ratio setting means , based on the engine required value, a temporary delay processing means for calculating a value obtained by subjecting the engine required value to a first order delay;
Upper limit compression ratio calculating means for calculating an upper limit compression ratio corresponding to the upper limit value of the target compression ratio based on the first-order lag processed value;
A selection means for selecting a smaller value as the target compression ratio between the required compression ratio and the upper limit compression ratio;
Is included.

  According to the present invention, when the compression ratio increases, such as when the vehicle is decelerated, the increase in the target compression ratio is suppressed / relieved. It is possible to prevent the expected fuel consumption reduction effect due to the change of the offset from being offset or reduced, and to reduce the reliability and durability of the mechanism and actuator that operate the compression ratio due to an excessive change of the compression ratio Can be suppressed or eliminated.

  On the other hand, when the compression ratio decreases, such as during vehicle acceleration, the decrease in the compression ratio is not intentionally delayed, so that the compression ratio becomes excessively high as described above, causing knocking. It wo n’t cause a serious situation.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example of a variable compression ratio mechanism applied to a compression ratio control device for an internal combustion engine according to the present invention. This variable compression ratio mechanism uses a multi-link type piston-crank mechanism in which the piston 3 and the crankpin 8 of the crankshaft 7 are linked by a plurality of links, and the structure thereof is disclosed in JP-A-2003-90409, etc. Are well known as disclosed in Japanese Patent Application Laid-Open No. H10-209, and only a brief description will be given here.

  The variable compression ratio mechanism includes an upper link 5 having one end connected to a piston 3 that slides in a cylinder 2 of a cylinder block 1 via a piston pin 4, and a connection pin 6 to the other end of the upper link 5. And a lower link 9 rotatably connected to the crankpin 8 of the crankshaft 7 and one end of the lower link 9 via a connecting pin 10 in order to limit the degree of freedom of the lower link 9. Are connected to each other and the other end of the control block 11 is swingably supported by an engine body (engine fixed body) such as the cylinder block 1, and the swing support position of the control link 11 is a control shaft. 12 is configured to be variably controlled by an eccentric cam portion 13 which is a control eccentric shaft portion. The control shaft 12 is disposed in parallel with the crankshaft 7 and is rotatably supported by the cylinder block 1.

  When the rotational position of the control shaft 12 changes, the motion constraint condition of the lower link 9 by the control link 11 changes, and the stroke characteristics and engine compression ratio of the piston 3 can be changed continuously. The control shaft 12 is rotationally driven by a motor 22 as a driving source / actuator linked through an actuator mechanism 31, and the operation of the motor 22 is a control signal corresponding to a target compression ratio tε output from the engine control unit 20. Controlled by. This compression ratio control is performed based on engine operating conditions. Typically, the compression ratio control is performed toward the low compression ratio side so as to avoid knocking as the engine load increases. Reference numeral 23 denotes an in-vehicle battery that supplies power to the starter 21 and the motor 22.

  According to such a variable compression ratio mechanism, in addition to being able to change the engine compression ratio in a continuous and stepless manner according to the engine operating state, it is possible to bring the piston stroke characteristic itself closer to a preferable characteristic, for example, a characteristic close to simple vibration. it can. Further, by connecting the control link 11 to the lower link 9, the drive system such as the control shaft 12 and the actuator mechanism 31 can be disposed obliquely below the crankshaft 7 having a relatively large space, so that the engine mountability is improved. Also excellent.

  As disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2003-90409, the actuator mechanism 31 that links the control shaft 12 of the variable compression ratio mechanism and the motor 22 that is the power source is operated from the control shaft 12 side. This is an irreversible transmission mechanism in which the rod 33 does not inadvertently move in the axial direction due to the rotational driving force, that is, the compression ratio does not fluctuate inadvertently. That is, it is possible to keep the compression ratio at the current set state without depending on the torque of the motor 22 and to reduce power consumption. The structure of the actuator mechanism 31 will be briefly described. A link lever 32 is fixed to the control shaft 12, and a pin at the tip of the rod 33 of the actuator mechanism 31 is engaged with a slit of the link lever 32. As a result, the control shaft 12 rotates as the rod 33 advances and retreats in the axial direction. The actuator mechanism 31 includes the rod 33 as a male screw member, a sleeve 34 as a female screw member screwed into the male screw portion of the rod 33, and a casing 35 that rotatably holds the sleeve 34. The sleeve 34 is rotationally driven by the motor 22.

  The engine control unit (ECM: engine control module) 20 is based on engine operating conditions detected by various sensors such as a rotational speed sensor 24, an accelerator opening sensor 25, a water temperature sensor 26, and a control shaft sensor 27. In addition to performing well-known fuel injection control, ignition timing control, etc., a control signal is output to the starter motor 21 that rotationally drives (cranks) the motor 22 and the crankshaft 7 to control its operation.

  FIG. 2 is a control block diagram of the compression ratio according to the first embodiment of the present invention, and FIG. 3 is a flowchart showing the flow of setting control of the target compression ratio tε of the first embodiment. This routine is stored in, for example, the engine control unit 20, and is repeatedly executed every predetermined period. The compression ratio operation means 40 operates the engine compression ratio toward the target compression ratio tε, and is composed of the variable compression ratio mechanism, the motor 22, the actuator mechanism 31 and the like shown in FIG.

  First, the required torque (load) calculating means of step 1 (denoted as “S” in the figure) calculates a required load or required torque tT1 as an engine required value based on the engine operating state. More specifically, based on the accelerator opening APO detected by the accelerator opening sensor 25 and the engine rotational speed Ne detected by the rotational speed sensor 24, referring to a control map as shown in FIG. The required torque tT1 is calculated.

  In step 2, the required compression ratio tε1 is calculated based on the required torque tT1 (required compression ratio calculating means). More specifically, the required compression ratio tε1 is calculated based on the engine speed Ne and the required torque tT1 with reference to a control map as shown in FIG.

  Based on the accelerator opening APO, the accelerator opening averaging means in step 3 calculates an accelerator opening average value APOave obtained by smoothing and averaging the accelerator opening APO (smoothing means). More specifically, a weighted average / first-order lag process is performed on the accelerator opening APO by the following equation (1) to calculate the average value APOave.

APOave = k × APO + (1−k) × APOave_old (1)
In the above equation (1), “k” is a preset constant less than 1, and “APOave_old” is the previous value of APO ave before one calculation (at the time of the previous calculation).

  In step 4, the average value tT2 of the required torque is calculated based on the accelerator opening average value APOave as in step 1.

  In step 5, an upper limit compression ratio tε2 corresponding to the upper limit value of the target compression ratio tε is calculated on the basis of the averaged required torque tT2 and the engine speed Net (upper limit compression ratio calculating means). ).

  The selection means in Step 6 sets the final target compression ratio tε based on the required compression ratio tε1 and the upper limit compression ratio tε2 (target compression ratio setting means). Specifically, the smaller one of the required compression ratio tε1 and the upper limit compression ratio tε2 is selected as the target compression ratio tε. This target compression ratio tε is output to the compression ratio operating means, and the engine compression ratio is operated toward the target compression ratio tε.

The operation when the compression ratio control according to the first embodiment is applied will be described with reference to the time chart of FIG. The accelerator opening average value APO ave is a value that intentionally dulls (delays) the follow-up performance with respect to the accelerator opening APO. Therefore, the upper limit compression ratio tε2 calculated using the accelerator opening average value APO ave is a value in which the followability to the required compression ratio tε1 is intentionally blunted. Therefore, by selecting the smaller one of the required compression ratio tε1 and the upper limit compression ratio tε2 as the target compression ratio tε, when the required compression ratio tε1 increases, the upper limit compression ratio tε2 becomes smaller than the required compression ratio tε1. The upper limit compression ratio tε2 is selected as the target compression ratio tε, and the target compression ratio tε is intentionally delayed with respect to the required compression ratio tε1, while the required compression ratio tε1 decreases when the required compression ratio tε1 decreases. Is less than the upper limit compression ratio tε2, the required compression ratio tε1 is selected as the target compression ratio tε, so that the target compression ratio tε follows the required compression ratio tε1 without delay.

  According to the present embodiment, when the compression ratio increases, such as when the vehicle is decelerated, the increase in the target compression ratio tε is suppressed / relieved. It is possible to effectively obtain the expected fuel consumption reduction effect by suppressing the compression ratio. Further, it is possible to prevent the reliability and durability of the compression ratio operation means 40 including the variable compression ratio mechanism, the actuator mechanism 31, the motor 22 and the like from being lowered by an excessive operation of changing the compression ratio. On the other hand, when the compression ratio decreases as in vehicle acceleration, the change in the compression ratio is not intentionally delayed. Therefore, as described above, it is possible to reliably prevent a situation where the compression ratio becomes excessively high and knocking occurs.

  Also, as described above with reference to FIGS. 2 and 3, the target compression ratio tε can be easily set by a relatively simple calculation process, the memory usage and calculation load can be suppressed, and this is advantageous in terms of cost. In particular, it is possible to easily calculate the upper limit compression ratio tε2 obtained by delaying (dulling) the required compression ratio tε1 using a known weighted average / first-order lag process, and to calculate the upper limit compression ratio tε2 and the required compression ratio tε1. By selecting the lower one as the target compression ratio tε, the desired target compression ratio tε can be easily set without using a complicated branching process or determination process.

  In the following embodiments, components that are the same as those in the embodiments already described are denoted by the same reference numerals, and differences from the embodiments described above will be mainly described.

  7 and 8 are a block diagram and a flowchart showing the flow of control of the compression ratio according to the second embodiment of the present invention. The second embodiment is different from the first embodiment only in the calculation process of the upper limit compression ratio tε2. That is, as in the first embodiment, in step 1, the required torque tT is calculated based on the accelerator opening APO and the engine speed Ne, and in step 2, the required torque tT is calculated based on the required torque tT and the engine speed Ne. The compression ratio tε1 is calculated.

  In step 3A, the requested torque tT is subjected to a weighted average / first-order lag process according to the following equation (2) to calculate a requested torque average value tTave obtained by averaging and smoothing the requested torque tT.

tTave = k * tT + (1-k) * tTave_old (2)
In the equation (2), “k” is a preset constant less than 1, and “tTave_old” is the previous value of tT ave before one calculation (at the time of the previous calculation).

  In the following step 5A, the upper limit compression ratio tε2 corresponding to the upper limit value of the target compression ratio tε is calculated based on the above required torque average value tTave and the engine speed Net, as in step 2 (upper limit compression ratio calculation). means). In step 6, as in the first embodiment, the smaller one of the required compression ratio tε1 and the upper limit compression ratio tε2 is selected as the target compression ratio tε (selecting means). This target compression ratio tε is output to the compression ratio operation means 40, and the engine compression ratio is manipulated toward the target compression ratio tε.

  According to the second embodiment, in addition to obtaining the same effect as that of the first embodiment, the calculation process can be further simplified by smoothing the required torque tT.

  9 to 12 are a block diagram and a flowchart showing a flow of control for setting the target compression ratio tε according to the third embodiment of the present invention. As in the first embodiment, in step 1, the required torque tT is calculated based on the accelerator opening APO and the engine speed Ne, and in step 2, the required compression ratio is calculated based on the required torque tT and the engine speed Ne. tε1 is calculated.

  In step 11, it is determined whether or not the required compression ratio can be increased by a subroutine shown in FIG. That is, at step 21, the accelerator opening APO is read. In step 22, it is determined whether or not the accelerator opening APO is in a high load range exceeding a predetermined opening mAPOSL set and stored in advance. In step 23, after the accelerator opening APO becomes equal to or less than the predetermined opening mAPOSL (after step 22 is denied), it is less than a predetermined period ΔT, that is, from the start of increase in the required compression ratio tε1 in the high load region. It is determined whether a predetermined period ΔT has not elapsed. If the predetermined period ΔT has elapsed, the routine proceeds to step 24, where an increase in the compression ratio is permitted, and the compression ratio increase enable / disable flag fUP is set to “1” accordingly. If it is less than the predetermined period ΔT, the routine proceeds to step 25 where the increase of the compression ratio is prohibited and the compression ratio increase enable / disable flag fUP is reset to “0” correspondingly.

  Referring to FIG. 10 again, in the following step 12, the target compression ratio tε is set based on whether or not the compression ratio can be increased in step 11 by the subroutine shown in FIG. Referring to FIG. 12, in step 31, the required compression ratio tε1 and the compression ratio increase availability flag fUP are read. In step 32, it is determined whether the compression ratio increase flag fUP is “1”. When fUP is “0”, that is, when the compression ratio increase is prohibited, the process proceeds to step 33, and the compression ratio increase permission width is set to “0”. When the compression ratio increase permission flag fUP is “1”, that is, when the compression ratio increase is permitted, the routine proceeds to step 34, where the compression ratio increase permission width is set to “COMPUP” which is a predetermined minute width.

  In step 35, the remaining increase change in the target compression ratio tε with respect to the required compression ratio tε1, that is, the difference between the current value of the required compression ratio tε1 and the previous value of the target compression ratio tε is smaller than the compression ratio increase permission width COMPUP. Determine whether. If the difference does not exceed the allowable width COMPUP, the process proceeds to step 36, and the required compression ratio tε1 is set as it is as the target compression ratio tε so that the target compression ratio tε does not exceed the required compression ratio tε1. On the other hand, if the difference exceeds the allowable width COMPUP, the target compression ratio tε is set by adding the compression ratio increase allowable width COMPUP to the previous value of the target compression ratio tε.

  The operation and effect when the compression ratio control according to the third embodiment is applied will be described with reference to the time chart of FIG. For example, when the vehicle is following the previous car during high-speed driving, an operation that temporarily releases the accelerator pedal (see reference numeral 41 in FIG. 13) is often performed in order to increase the inter-vehicle distance. If the compression ratio is temporarily increased every time such an operation is performed, the compression ratio will be changed excessively, the loss of energy required for the operation of the compression ratio will increase, and the durability of the compression ratio operation system will be increased. It will cause deterioration of reliability and reliability. On the other hand, according to the third embodiment, since the increase in the compression ratio is prohibited for a predetermined period ΔT in a high load region such as during the high-speed following operation, a temporary increase in the compression ratio (FIG. 13). (See reference numeral 42) can be suppressed from being performed excessively.

  In addition, when the compression ratio is increased after the predetermined period ΔT has elapsed, the target compression ratio tε is gradually increased step by step by a minute width COMPUP, so that energy loss and durability / reliability decrease due to a sudden increase in the compression ratio. Can be more reliably suppressed. Further, when the compression ratio decreases, the required compression ratio tε1 is set as the target compression ratio tε as it is as in the first embodiment, so that the decrease in the compression ratio is not delayed or blunted. There is no possibility of incurring a problem that causes knocking transiently due to a delay in the decrease in the speed.

  As described above, the present invention has been described with reference to specific embodiments. However, the present invention is not limited to the illustrated embodiments, and includes various modifications and changes without departing from the spirit of the present invention. For example, in the first and second embodiments, the increase in the target compression ratio may be intentionally blunted only in a predetermined high load region as in the third embodiment. In addition, as a method of intentionally slowing the increase in the target compression ratio, a method using a weighted average / first-order lag equation as in the first and second embodiments, and a stepwise compression ratio as in the third embodiment. Any method may be used such as a method of raising the temperature to the next.

  Characteristic technical ideas that can be understood from the above description are listed. However, the present invention is not limited to the configuration of the illustrated embodiment specified by using reference numerals.

  (1) Required compression ratio calculation means (step 2) for calculating the required compression ratio tε1 based on the engine required value corresponding to the required load or the required torque tT, and the target compression ratio tε based on the required compression ratio tε1. Target compression ratio setting means for setting, and compression ratio operation means 40 for operating the engine compression ratio toward the target compression ratio tε, and the target compression ratio setting means has the required compression ratio tε1. In the case of increasing, a compression ratio increasing / decreasing means for intentionally decreasing the followability of the target compression ratio tε with respect to the required compression ratio tε1 is included.

  (2) For example, as in the first and second embodiments, the compression ratio increase blunting means calculates a smoothed means (step 3) for smoothing the engine required value based on the engine required value. 3A), upper limit compression ratio calculation means (steps 5 and 5A) for calculating an upper limit compression ratio tε2 corresponding to the upper limit value of the target compression ratio tε based on the smoothed value, and the required compression ratio tε1. Selecting means (step 6) for selecting a smaller value as the target compression ratio tε in the upper limit compression ratio tε2.

  (3) Preferably, the compression ratio increase blunting means prohibits the increase in the target compression ratio tε for a predetermined period ΔT from the start of the increase in the target compression ratio tε (step 25).

  (4) More preferably, the compression ratio increase / decrease means increases the target compression ratio tε step by step by a predetermined increase permission width COMPUP (steps 34, 37).

  (5) The followability of the target compression ratio may be intentionally blunted by the compression ratio increase blunting means only in a predetermined high load range (step 22).

  (6) Preferably, the engine compression ratio operation means includes a lower link 9 attached to the crankpin 8 of the crankshaft 7, an upper link 5 that links the lower link 9 and the piston 3 of the internal combustion engine, and a control shaft. 12, a control eccentric shaft portion 13 provided eccentric to the control shaft 12, a control link 11 linking the control eccentric shaft portion 13 and the lower link 9, and the target compression ratio tε. And an actuator (actuator mechanism 31 and motor 22) for rotationally driving the control shaft 12.

FIG. 3 is a cross-sectional view showing an example of a variable compression ratio mechanism according to the present invention. The block diagram which shows the setting control of the compression ratio which concerns on 1st Example of this invention. The flowchart which shows the flow of the setting control of the compression ratio which concerns on the said 1st Example. The timing chart at the time of applying the compression ratio control of the said 1st Example. An example of the control map for setting a request torque. An example of the control map for setting a request compression ratio. The block diagram which shows the setting control of the compression ratio which concerns on 2nd Example of this invention. The flowchart which shows the flow of the setting control of the compression ratio which concerns on the said 2nd Example. The block diagram which shows the setting control of the compression ratio which concerns on 3rd Example of this invention. The flowchart which shows the flow of the setting control of the compression ratio which concerns on the said 3rd Example. A subroutine of step 11 in FIG. 10 for determining whether or not the compression ratio can be increased. A subroutine of step 12 in FIG. 10 for setting a target compression ratio. The timing chart at the time of applying the compression ratio control of the said 3rd Example. The characteristic view which shows the relationship between a request torque and a target compression ratio.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Piston 5 ... Upper link 7 ... Crank shaft 8 ... Crank pin 9 ... Lower link 11 ... Control link 12 ... Control shaft 13 ... Control eccentric shaft part 20 ... Engine control part 22 ... Motor (actuator)

Claims (3)

A required compression ratio calculating means for calculating a required compression ratio based on the engine required value corresponding to the required load or the required torque;
Target compression ratio setting means for setting a target compression ratio based on the required compression ratio;
Compression ratio operating means for operating the engine compression ratio toward the target compression ratio,
And, the target compression ratio setting means , based on the engine required value, a temporary delay processing means for calculating a value obtained by subjecting the engine required value to a first order delay;
Upper limit compression ratio calculating means for calculating an upper limit compression ratio corresponding to the upper limit value of the target compression ratio based on the first-order lag processed value;
A selection means for selecting a smaller value as the target compression ratio between the required compression ratio and the upper limit compression ratio;
A compression ratio control apparatus for an internal combustion engine, comprising: 2. The compression ratio control apparatus for an internal combustion engine according to claim 1, wherein a smaller value of the required compression ratio and the upper limit compression ratio is selected as the target compression ratio only in a predetermined high load range. The engine compression ratio operation means includes a lower link attached to a crankpin of a crankshaft, an upper link for linking the lower link and the piston of the internal combustion engine, a control shaft, and a control provided eccentric to the control shaft. An eccentric shaft portion, a control link that links the control eccentric shaft portion and the lower link, and an actuator that operates in response to the target compression ratio and rotationally drives the control shaft. 3. A compression ratio control device for an internal combustion engine according to 1 or 2 .

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