JP5136366B2 - Control device for variable compression ratio mechanism of internal combustion engine - Google Patents

Description

  The present invention relates to control of a variable compression ratio mechanism of an internal combustion engine that changes a piston stroke in accordance with a rotational position of a control shaft.

Patent Document 1 discloses a variable compression ratio mechanism that makes an engine compression ratio variable by changing a piston stroke of an internal combustion engine. In this mechanism, a link row composed of a plurality of links linking a piston reciprocating in a cylinder and a crankpin of a crankshaft, an eccentric shaft portion of a control shaft whose rotational position is changed and held by a drive portion such as a motor, Are linked by the control link, and the piston stroke is changed by changing the motion restraint condition of the lower link by the control link in accordance with the rotational position of the control shaft. In the power transmission path from the drive unit to the control shaft, a clutch for interrupting reverse input of a load caused by in-cylinder pressure or the like to the drive unit via the link train is interposed. In addition, a speed reduction mechanism is interposed in the power transmission path from the clutch to the control shaft. The clutch functions as a cage that mechanically holds the rotational position of the control shaft corresponding to the engine compression ratio.
JP 2007-239520 A

  In the case where the above-described cage does not involve slip, the rotational position of the control shaft is mechanically strictly fixed. Therefore, in a steady operation state with a constant compression ratio, the control shaft does not rotate and continues to receive a load such as in-cylinder pressure from the engine side at a constant angle. Here, in the bearing portion that rotatably supports the main shaft of the control shaft on the engine body side such as a cylinder block, even if the rotation of the control shaft is mechanically fixed, there are few surrounding structures including the control shaft itself. A slight movement state that moves slightly in the rotational direction on the surface of the bearing portion due to the elastic deformation is inevitable. When fine movement occurs in the bearing portion in this way, there arises a problem that this fine movement induces the occurrence of fretting (surface flaws) and promotes fretting wear of the control shaft. This fretting wear is generally a failure phenomenon that must be avoided when durability is taken into account because the amount of wear accumulates with time. Further, when the control shaft is fixed at the same position, the load application position is concentrated on the same position, and local wear is likely to be caused.

  The present invention has been made in view of such problems, and an object of the present invention is to reduce or avoid the occurrence / promotion of fretting wear due to the fine movement of the control shaft.

The present invention provides a link row composed of a plurality of links that link a piston that reciprocates in a cylinder and a crankpin of a crankshaft, a control shaft whose rotational position is changed and held by a drive unit, and the control shaft and the link. The present invention relates to control of a variable compression ratio mechanism of an internal combustion engine that includes a control link that links columns, and whose piston stroke changes according to the rotational position of the control shaft. Then, set the target compression ratio according to the engine operating state, and, at a predetermined tolerance in a region including the target compression ratio, it intends rows swing control for rocking the control shaft in the rotational direction.
The first invention is characterized in that the swing control is executed in a steady operation state in which the target compression ratio is maintained near the minimum compression ratio.
The second invention is characterized in that the width of the allowable deviation region is adjusted according to the engine operating state, and the width of the allowable deviation region is increased as the target compression ratio is lower.
A third invention has a control axis sensor for detecting the rotational position of the control shaft, and the deviation amount of the allowable deviation area is set to zero during execution of the reference position learning control of the sensor output of the control axis sensor. It is characterized by doing.

  According to the present invention, the intervention of the lubricating oil in the bearing portion of the control shaft is facilitated by performing the swing control for swinging the control shaft in the rotational direction within a predetermined allowable deviation region including the target compression ratio. By improving the lubrication performance, the generation and promotion of fretting wear due to the fine movement of the control shaft can be effectively reduced or avoided. Moreover, compared with the case where the control shaft is mechanically fixed at the same position, the load application position does not concentrate at the same position, and it is possible to suppress the local progress of wear.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a variable compression ratio mechanism for an internal combustion engine according to an embodiment of the present invention, and corresponds to a cross-sectional view in a direction perpendicular to the crankshaft axis passing through the cylinder center of the in-line engine.

  In the cylinder block 11, a cylindrical cylinder 12 is formed for each cylinder, and a water jacket 13 is formed around each cylinder 12. A piston 14 is disposed in each cylinder 12 so as to be movable up and down. The piston pin 15 of each piston 14 and the crankpin 17 of the crankshaft 16 are a link row composed of a plurality of links, specifically, an upper. The link 22 and the lower link 21 are mechanically linked. Reference numeral 18 denotes a counterweight of the crankshaft 16. Specifically, the variable compression ratio mechanism includes a lower link 21 that is attached to the crankpin 17 so as to be relatively rotatable, an upper link 22 that connects the lower link 21 and the piston pin 15, and a cylinder parallel to the crankshaft 16. A control shaft 23 extending in the column direction, an outer peripheral circular eccentric shaft portion 24 eccentrically provided on the control shaft 23, a control link 25 connecting the eccentric shaft portion 24 and the lower link 21, and a control shaft 23 And an actuator unit 30 including an electric motor (hereinafter also referred to as “drive unit”) 33 as a drive unit that is rotationally driven within a predetermined control range.

  The upper end portion of the rod-like upper link 22 is attached to the piston pin 15 of the piston 14 so as to be relatively rotatable, and the lower end portion is connected to the lower link 21 via the first connecting pin 26 so as to be relatively rotatable. . One end of the control link 25 is connected to the lower link 21 via the second connecting pin 27 so as to be relatively rotatable, and the other end of the control link 25 is attached to the outer periphery forming the cylindrical surface of the eccentric shaft portion 24 so as to be relatively rotatable. It has been. As shown also in FIG. 2, the control shaft 23 has a plurality of main shafts 29 that are rotatably supported at the lower part of the cylinder block 11. The rotation center P of the eccentric shaft portion 24 is eccentric by a predetermined amount with respect to the rotation center Q of the main shaft 29.

  By rotating the control shaft 23 by the actuator unit 30 in accordance with the engine operating state, the position of the swing fulcrum of the control link 25 fitted around the eccentric shaft portion 24 changes, and the postures of the lower link 21 and the upper link 22 are changed. Changes, and the compression ratio of the combustion chamber defined above the piston 14 is variably controlled. Such a variable compression ratio mechanism, in addition to being able to continuously change the engine compression ratio, has a favorable piston stroke characteristic as compared to a single link mechanism in which the piston and the crank pin are connected by a single connecting rod. (For example, characteristics close to simple vibration). Further, since the control link 25 is connected to the lower link 21, the control link 25, the control shaft 23, and the actuator unit 30 can be arranged in the lower region of the crankshaft 16 having a relatively large space. Compared to the one described in Japanese Patent Application Laid-Open No. 2005-30234, the engine mounting property is excellent.

  FIG. 3 is a sectional view showing the actuator unit 30 as a single unit. The actuator unit 30 is mainly composed of a casing 40 that is fixed to the lower side of the cylinder block 11 and includes a plurality of parts 40A to 40C that are fixed to each other by bolts 42A, pins 42, and the like. The casing 40 is attached with the motor 33, and an actuator shaft 32 that engages with the control shaft 23 is supported so as to be able to reciprocate and slide in the axial direction. The drive torque of the motor 33 is transmitted to the control shaft 23 via Although not shown, an oil pan for storing lubricating oil is attached below the cylinder block 11 and the casing 40, and a crankshaft 16 or the like as a lubricating part is disposed above the oil pan. A crank chamber 19 is formed. The casing 40 functions as an outer wall of the crank chamber 19 that fluidly defines the crank chamber 19 together with the side wall of the cylinder block 11, and the casing 40 causes the actuator shaft 32 to move into the crank chamber 19. The motor 33 is held outside the cylinder block 11 while being slidably held in a faced position.

  The actuator unit 30 has a clutch (hereinafter also referred to as “cage”) 43 that cuts off the reverse input from the control shaft 23 side to the drive unit 33 side in the power transmission path from the motor 33 to the control shaft 23. It is intervened. The clutch 43 functions as a cage that mechanically holds the rotational position of the control shaft 23 corresponding to the engine compression ratio. A first speed reduction mechanism 44 is interposed in the power transmission path from the motor 33 to the clutch 43, and a second speed reduction mechanism 45 and a final speed reduction mechanism 46 are in the power transmission path from the clutch 43 to the control shaft 23. Is intervening.

  The first speed reduction mechanism 44 is fixed to the first input side gear 44A fixed to the output shaft (pinion shaft) 33A of the motor 33 and the input shaft 2 of the clutch 43, and engages with the first input side gear 44A. And a reduction gear train constituted by the output side gear 44B. The second reduction mechanism 45 includes a second input side gear 45A that is fixed to the output shaft 3 of the clutch 43, a second output side gear 45B that is provided on the outer periphery of the final gear 36 and meshes with the second input side gear 45A, It is a reduction gear train comprised by these. These gears are fixed using press-fitting or parallel keys.

  The final reduction mechanism 46 includes a feed screw mechanism 47 that converts the rotary motion of the final gear 36 into a reciprocating motion of the actuator shaft 32, a slider crank mechanism 48 that converts the reciprocating motion of the actuator shaft 32 into a rotary motion of the control shaft 23, have. As shown in FIG. 2, the feed screw mechanism 47 includes a male screw 35 formed at the end of the actuator shaft 32 on the motor side and a female screw 37 formed on the inner peripheral surface of the final gear 36 and meshing with the male screw 35. The rotational movement of the final gear 36 is converted into the reciprocating movement of the actuator shaft 32 and transmitted. The slider crank mechanism 48 converts the reciprocating motion of the actuator shaft 32 into the rotational motion of the control shaft 23 via the pin 39 and transmits it. The pin 39 is provided with small-diameter portions 39B on both sides of a large-diameter portion 39A that is rotatably fitted to one end (tip) of the actuator shaft 32 having a cylindrical shape. The small-diameter portion 39B is slidably fitted in a radially extending slit 41 formed in a pair of control plates 41A provided at one end of the control shaft 23. Therefore, when the actuator shaft 32 reciprocates, the control shaft 23 rotates in a predetermined direction via the control plate 41A while being accompanied by a sliding operation of the pin 39 in the slit 41.

  The clutch 43 is known as disclosed in Japanese Patent Application Laid-Open No. 2003-343601. Briefly described, the clutch 43 has a motor-side input shaft with respect to the stationary outer ring 1 as a stationary member fixed to the casing 40B. 2 and the output shaft 3 on the control shaft 23 side are supported so as to be rotatable forward and backward via rolling bearings 4A to 4D. The input shaft 2 and the output shaft 33A of the motor 33 are connected via the first reduction mechanism 44, and the output shaft 3 and the final gear 36 are connected via the second reduction mechanism 45. . The fixed outer ring 1 is stably fixed to the casing 40 by press-fitting or using a parallel key.

  As shown in FIGS. 4 and 5, the input shaft 2 is provided with a through hole 6 along the axial direction at a position shifted radially outward from the shaft center, and the output shaft 3 includes the input shaft 2 and A concave groove 7 is formed along the radial direction on the opposite end face. By inserting a pin 8 into the through-hole 6 of the input shaft 2, projecting the tip of the pin 8 from the end surface facing the output shaft 3, and fitting it into the groove 7 formed on the end surface of the output shaft 3, The rotational torque from the input shaft 2 can be transmitted to the output shaft 3. A flange portion 2a whose diameter is increased radially outward is integrally formed at the output shaft side end portion of the input shaft 2, and serves as a cage continuously extending from the outer periphery of the flange portion 2a to the output shaft side in the axial direction. A plurality of column portions 2b are formed at equal intervals in the circumferential direction. The space between the column portions 2b adjacent to each other in the circumferential direction constitutes a pocket 9 that is open toward one side in the axial direction, and a pair of rollers 10a and 10b is disposed in each pocket 9, respectively. A plurality of pairs of cam surfaces (wedge surfaces) 9a, 9b are formed at equal intervals in the circumferential direction on the input shaft side outer periphery of the output shaft 3 so as to correspond to the pockets 9 positioned between the column portions 2b of the input shaft 2 described above. Has been. A plurality of pairs of rollers 10a and 10b are respectively disposed between the cam surfaces 9a and 9b of the output shaft 3 and the inner peripheral surface of the fixed outer ring 1, and the pockets 9 formed between the column portions 2b of the input shaft 2 are provided. Be contained. An elastic member 5 such as a spring is inserted between the pair of rollers 10a and 10b, and the elastic member 5 elastically presses the pair of rollers 10a and 10b away from each other. Each elastic member 5 is inserted and disposed between the pair of rollers 10 a and 10 b independently of the input shaft 2, the output shaft 3 and the fixed outer ring 1.

  When the reverse input torque in the clockwise direction is input to the output shaft 3 in the neutral state shown in an enlarged view in FIG. 6A, the reverse input cutoff clutch 43 is counterclockwise (rotated) by the elastic force of the elastic member 5. The roller 10a (backward in the direction) is engaged with the wedge gap in that direction, and the output shaft 3 is locked in the clockwise direction with respect to the fixed outer ring 1. Conversely, when counterclockwise reverse input torque is input to the output shaft 3, the roller 10b in the clockwise direction (backward in the rotational direction) is engaged with the wedge gap in that direction by the elastic force of the elastic member 5, and the output is output. The shaft 3 is locked counterclockwise with respect to the fixed outer ring 1. Therefore, the reverse input torque from the output shaft 3 is locked in both forward and reverse rotation directions by the pair of rollers 10a and 10b.

  On the other hand, when rotational torque is input to the input shaft 2 and rotated clockwise, for example, as shown in an enlarged view in FIG. 6B, first, the column portion of the input shaft 2 in the counterclockwise direction (backward in the rotational direction). 2b engages with the roller 10a in that direction (backward in the rotational direction) and presses it in the clockwise direction (forward in the rotational direction) against the elastic force of the elastic member 5. As a result, the counterclockwise (backward in the rotational direction) roller 10a is released from the wedge gap in that direction, the locked state of the output shaft 3 is released, and the output shaft 3 can be rotated clockwise. When the input shaft 2 further rotates clockwise, the pin 8 of the input shaft 2 abuts against the wall surface of the concave groove 7 of the output shaft 3 as shown in FIG. Rotational torque in the direction is transmitted to the output shaft 3 through the engaging portion between the pin 8 and the groove 7, and the output shaft 3 rotates clockwise. At this time, the roller 10b in the clockwise direction (forward in the rotation direction) does not engage with the wedge clearance in that direction, and idles in a state where the cam surface of the output shaft 3 and the inner peripheral surface of the fixed outer ring 1 are in contact. When a counterclockwise rotational torque is input to the input shaft 2, the output shaft 3 rotates counterclockwise by the reverse operation to that described above. Accordingly, the rotational torque in the forward and reverse rotational directions from the input shaft 2 is transmitted to the output shaft 3 through the engaging portion between the pin 8 and the concave groove 7, and the output shaft 3 rotates in the forward and reverse rotational directions. To do.

  Here, when the lock is released, the roller needs to be separated from the wedge gap as described above. However, when the output shaft can rotate excessively smoothly during this operation, the roller is separated from the wedge gap. Without rotating, it may rotate with the output shaft and may not be unlocked. For this reason, in order to smoothly perform the unlocking operation, a predetermined amount of rotational resistance (frictional force or the like) is applied to the output shaft 3. In the example of FIG. 7, the oil seal 49 is disposed on the output shaft 3 side to add resistance in the rotational direction. The oil seal 49 is basically interposed between the outer periphery of the second input side gear 45A of the second reduction mechanism 45 fixed to the output shaft 3 and the casing 40, and seals this portion. Thus, the resistance addition in the rotational direction is realized with a simple configuration using the oil seal 49.

  As described above, since the rotation of the output shaft 33A of the motor 33 is sufficiently decelerated and transmitted to the control shaft 23 by the first deceleration mechanism 44, the second deceleration mechanism 45, and the final deceleration mechanism 46, the control shaft The reverse input torque acting on the motor 33 from the side can be greatly suppressed, and the motor 33 can be reduced in size and output, and the clutch 43 blocks the reverse input from the control shaft 23 side to the motor 33 side. can do. In this embodiment, since the second reduction mechanism 45 and the final reduction mechanism 46 are interposed between the clutch 43 and the control shaft 23, the reverse input from the control shaft 23 side to the clutch 43 side is suppressed. can do. Therefore, it is possible to reduce the size of the clutch 43 and improve the engine mountability while ensuring the shut-off ability, reliability, and durability of the clutch 43.

  Further, the screwing action of the feed screw mechanism 47 can more reliably prevent the actuator shaft 32 from being inadvertently rotated due to reverse input from the control shaft 23.

  The clutch 43 and the speed reduction mechanisms 44 to 46 are accommodated in the casing 40 except for the tip of the actuator shaft 32 protruding into the crank chamber 19. A seal member 50 is attached to the outer periphery of the actuator shaft 32 to seal a gap with the cylindrical inner periphery of the casing 40A. As this seal member, for example, various members such as an oil seal, a lip seal, and a labyrinth packing can be used in addition to an O-ring as illustrated. By such a seal member 50 and the oil seal 49 described above, the internal space of the casing 40 in which the clutch 43 and the speed reduction mechanisms 44 to 46 are disposed is liquid-tightly separated from the crank chamber 19. Therefore, the internal space of the casing 40 in which the clutch 43 and the speed reduction mechanisms 44 to 46 are disposed is lubricated by using a dedicated lubricant such as grease, in addition to the engine oil (lubricating oil) scattered in the crank chamber 19. The lubrication performance of the clutch 43 and the speed reduction mechanisms 44 to 46 can be greatly improved as compared with the case where the engine oil is lubricated in the same manner as the crankshaft or the like. Therefore, it is possible to further reduce the size of the clutch 43 while ensuring the load blocking capability of the clutch 43 and minimizing the load on the motor 33 side.

  The control unit 51 has a function of storing and executing various engine control processes such as fuel injection control and ignition timing control based on the engine speed and engine load detected by various sensors. Based on the detection signal of the control shaft sensor 52 that detects the rotational position of the control shaft 23 corresponding to the ratio, a control signal is output to the electric motor 33 as the drive unit, and the engine compression ratio, that is, the control shaft 23 of the control shaft 23 as described later. Control the rotational position.

  Next, control of the engine compression ratio, which is a feature of this embodiment, will be described. FIG. 7 is an explanatory diagram showing the generation factor of the control shaft torque due to the in-cylinder pressure such as the combustion load, and FIG. 7A shows a skeleton diagram of the variable compression ratio mechanism. The combustion load F0 in the downward direction of the cylinder axis acting on the crown surface of the piston 14 acts on the lower link 21 via the upper link 22 as the torque F1 around the crankpin 17. The rotation direction of the torque F1 is determined by the position of the second connecting pin 26 with respect to the crank pin 17, and is the counterclockwise direction in the illustrated example. The lower link 21 is connected to the control link 25 at the end portion not connected to the upper link 22, and the torque F <b> 1 acting on the lower link 21 is obliquely upward along the axial direction of the control link 25. Acts as a load F2. Here, the end portion of the control link 25 that is not connected to the lower link 21 is pivotally supported by the eccentric shaft portion 24 of the control shaft 23, and the eccentric shaft portion 24 is supported by the control shaft 23. The main shaft 29 is eccentric by a predetermined amount.

  FIG. 7B shows the positional relationship of the eccentric shaft portion 24 according to the engine compression ratio. As shown in the figure, since the force F2 resulting from the load due to the in-cylinder pressure acts on the eccentric shaft portion 24 at each compression ratio obliquely above the engine, the in-cylinder pressure is changed in the direction of changing from the maximum compression ratio to the minimum compression ratio. Acts as the control shaft torque F3. Note that this control shaft torque F3 is not only the direction shown in FIG. 7B, but also the torque in the opposite direction (counterclockwise direction) when the force due to the inertial force of the moving part upward is dominant, for example. Also works. Thus, since the control shaft 23 receives the torque F3 in the rotational direction from the engine side, in a steady operation state in which the target compression ratio tε is kept constant, the control shaft 23 is placed at a predetermined position against the torque F3. Need to hold on.

  FIG. 8 shows an example of a compression ratio control map used for setting the target compression ratio tε of the variable compression ratio mechanism. As shown in the figure, the target compression ratio tε is set in accordance with the engine speed and the engine load (load torque). Basically, the target compression ratio tε is set to a high compression ratio in order to improve fuel efficiency on the low rotation and low load side. On the high rotation high load side, the compression ratio is low so that knocking does not occur. The lower left area in the figure is the driving area that is mainly used for ordinary city driving. In such low to medium speed rotation and low to medium load regions, a high compression ratio is set. In such a high compression ratio setting, since the sensitivity of the change in the engine compression ratio with respect to the rotation angle of the control shaft 23 is high, in a steady operation state in which the high compression ratio setting is maintained, it is maintained as described later. The engine compression ratio is mechanically fixed by the device 43.

  On the other hand, the minimum compression ratio is set in the region on the high rotation / high load side. In the steady operation state in which the setting of the minimum compression ratio is maintained, as described later, a predetermined allowable deviation region Δtε including the target compression ratio tε is set, and the control shaft 23 is rotated within the allowable deviation region Δtε. Swing control is performed to swing in the direction. Therefore, in the control near the minimum compression ratio, the mechanical control shaft 23 is not fixed using the retainer 43, and the control shaft 23 corresponding to the engine compression ratio is repeatedly operated by the forward / reverse rotation of the motor 33. The rotational position of the control shaft 23 is held in the allowable deviation area Δtε while periodically changing the rotational position in the allowable deviation area Δtε.

  FIG. 9 shows the relationship between the rotation angle of the control shaft 23 and the engine compression ratio. As a feature of the multi-link variable compression ratio mechanism, the change in the engine compression ratio exhibits non-linear characteristics with respect to the change in the rotation angle of the control shaft 23. Specifically, the higher the compression ratio side, the higher the sensitivity of the change ratio of the compression ratio with respect to the change of the piston top dead center position, so the lower the compression ratio side, the lower the compression ratio change ratio with respect to the rotation angle of the control shaft 23. It has the characteristic to do. That is, in the vicinity of the minimum compression ratio, the change in the compression ratio is very insensitive to the rotation angle of the control shaft 23, and the control of the rotation angle of the control shaft 23 is ambiguous compared to the high compression ratio side. However, it means that there is little influence on the operation performance such as engine output. Therefore, even if the swing control is performed on the low compression ratio side as described above, the rebound to the driving performance such as the engine output is small, and the passenger does not feel uncomfortable.

  FIG. 10 shows the relationship between the setting of the allowable deviation region Δtε and the engine operating conditions, together with the width relationship of the allowable deviation region Δtε. As described above, since the change in the compression ratio with respect to the rotation angle of the control shaft 23 becomes less sensitive as the engine compression ratio becomes lower, the allowable deviation region becomes lower as the engine compression ratio becomes lower without affecting the engine operating performance. The width of Δtε is set large. In other words, the width of the allowable deviation region Δtε is increased as the rotation speed is higher.

  On the other hand, in the maximum compression ratio and the set state in the vicinity thereof, the allowable deviation region Δtε is sufficiently small and the swinging operation within the allowable deviation region Δtε is difficult. Thus, the rotational position of the control shaft 23 corresponding to the engine compression ratio ε is mechanically held. Here, the operation region in which the maximum compression ratio and the setting state in the vicinity thereof are used is an operation region on the low rotation / low load side represented by mode operation, and torque F3 acting on the eccentric shaft portion 24 of the control shaft 23. (Refer to FIG. 7) is also relatively low, so that the cage 43 can be downsized, and even if the rotational position of the control shaft 23 is mechanically held by the cage 43, the possibility of fretting is low. .

  FIG. 11 shows an example of a relationship curve of current with respect to efficiency and output in a general electric motor 33 as a drive unit. Generally, the electric motor 33 applies an electric current, rotates the output shaft 33A, and takes out an output. Depending on the magnitude of the applied current, it is possible to adjust and select the motor rotation speed and output / efficiency used. In the variable compression ratio mechanism as described above, if it is attempted to fix the rotational position of the control shaft 23 to one place by the motor 33 without using the retainer 43, the rotational speed of the control shaft 23 is 0 (zero) or the vicinity thereof. Therefore, the rotational speed of the output shaft 33A of the electric motor 33 that is a drive source is also zero or in the vicinity thereof. The stall point shown in FIG. 11 corresponds to the state where the rotational speed is zero, and the efficiency is also zero at this stall point. Zero efficiency is a state in which the applied current is not reflected as an output but is consumed as self-heating, which is very undesirable as a method of using the motor.

  On the other hand, in the present embodiment, particularly when the rotation angle of the control shaft 23 is insensitive to the change ratio of the compression ratio and the low compression ratio side, the compression ratio is maintained only by the motor 33 without using the retainer 43. The motor 33 is used in a region where the efficiency is higher than that in the vicinity of the stall point by repeatedly rotating or swinging the output shaft 33A of the motor 33 within the predetermined allowable deviation region Δtε without stopping. Therefore, the holding ability by the motor 33 is improved, and the compression ratio holding by only the motor 33 at a low compression ratio can be realized satisfactorily.

  FIG. 12 is a flowchart showing the control flow of this embodiment.

  In step S1, it is determined whether or not reference position learning control of sensor output of the control axis sensor 52 described later is being executed. If the sensor reference position learning control is being performed, this routine is terminated.

  In step S2, it is determined whether the target compression ratio tε is a constant steady operation state or a transient operation state in which the target compression ratio tε changes during acceleration or deceleration. This determination is made based on, for example, the rotation speed of the output shaft 33A of the drive unit 33, or in accordance with a change in the target compression ratio Δtε. If it is a transient operation state in which the target compression ratio Δtε changes, the routine ends without performing swing control described later and holding by the cage 43. In this case, normal compression ratio control toward the target compression ratio tε is performed. If it is determined that the operation is steady, the process proceeds to step S3.

  In step S3, the target compression ratio tε is read. This target compression ratio tε is set with reference to the control map shown in FIG. 8 based on, for example, the engine speed and the engine load. As shown in FIG. The compression ratio is low so that knocking does not occur on the high rotation high load side.

  In step S4, it is determined whether or not swing control is performed. For example, as shown in FIG. 10, if the engine speed and the engine load are on the high rotation / high load side that is larger than the predetermined determination value α, it is determined that the region is in the swing control execution region. Alternatively, if the target compression ratio tε is on the low compression ratio side that is smaller than a predetermined determination value, it may be determined that the region is in the swing control region.

  If it is determined that the region is not in the swing control region, the process proceeds from step S4 to step S5, and the rotational position of the control shaft 23 is mechanically held by the holder 43. If the deviation between the actual compression ratio detected by the control shaft sensor 52 and the target compression ratio tε is large, the actual compression ratio is made sufficiently close to the target compression ratio tε, and then the holding by the cage 43 is performed. When holding by the holder 43, voltage application to the electric motor 33 is stopped to reduce energy consumption.

  When it is determined that the region is to be subjected to the swing control, the process proceeds to step S6, and an allowable deviation region Δtε in the swing control is set (allowable deviation region setting means). That is, the maximum value εMAX and the minimum value εMIN of the control target value in the swing control are set. For example, as shown in FIG. 10, by setting the width Δεu on the high compression side and the width Δεd on the low compression ratio side with respect to the target compression ratio tε to be the same, the deviation / deviation of the actual engine compression ratio with respect to the target compression ratio tε. Can be suppressed. Alternatively, when the margin of the compression ratio with respect to knocking is small, is the width Δεd on the low compression ratio side relative to the target compression ratio tε relatively large and the width Δεu on the high compression ratio side relatively small? Or it may be zero.

  Further, as described above, since the allowable deviation width changes according to the target compression ratio tε, the width of the allowable deviation region Δtε itself is adjusted according to the target compression ratio tε. Specifically, as shown in FIG. 10, as the target compression ratio tε decreases, the sensitivity of the control shaft 23 with respect to changes in the compression ratio decreases, so the width of the allowable deviation region Δtε is increased.

  In the following step S7, a switching cycle between the maximum value εMAX and the minimum value εMIN of the target compression ratio tε in the swing control is set so that the maximum combustion load of each cylinder does not concentrate on the same place as will be described later. .

  In step S8, swing control is executed. That is, the control target value output to the drive unit 33 is alternately switched between the maximum value εMAX and the minimum value εMIN of the allowable deviation region Δtε set in step S6 at the switching cycle set in step S7. As described above, the control target value is controlled alternately and stepwise between the maximum value εMAX and the minimum value εMIN, so that the actual control shaft 23 swings within the allowable deviation region Δtε in the rotational direction with a response delay. It will be.

  Next, characteristic configurations of the present invention and their functions and effects will be listed below with reference to the above-described embodiments.

  [1] A link row composed of a plurality of links 21 and 22 linking the piston 14 reciprocating in the cylinder 12 and the crankpin 17 of the crankshaft 16, and a control shaft whose rotational position is changed and held by the drive unit 33. 23, and a control link 25 for linking the control shaft 23 and the link row, and a control device for a variable compression ratio mechanism of an internal combustion engine in which the piston stroke changes according to the rotational position of the control shaft 23. , Target compression ratio setting means for setting the target compression ratio tε according to the engine operating state, and swing control for swinging the control shaft 23 in the rotational direction within a predetermined allowable deviation region Δtε including the target compression ratio tε. Swing control means for performing

  In this way, by performing swing control that swings the control shaft in the rotational direction within a predetermined allowable deviation region Δtε including the target compression ratio tε, the rotation of the control shaft 23 is fixed in one place. Thus, the lubricating oil can easily intervene on the surface of the bearing portion that supports the control shaft 23, the frequency of occurrence of the fretting wear described above can be reduced, and the reliability and durability can be improved.

  Further, by swinging the control shaft 23 in the allowable deviation region Δtε, the load application position on the bearing portion does not concentrate at the same place, and the progress of local wear can be suppressed and the stall can be suppressed. Since it is possible to use a region that is relatively more efficient than the vicinity of the point (see FIG. 11), the holding capability of the electric motor 33 as the drive unit is improved, and as a result, the electric motor 33 that is the drive source is downsized. Can be achieved.

  [2] In the swing control, the maximum value tεMAX and the minimum value tεMIN of the allowable deviation region Δtε are alternately set as control target values. Thus, while the control target value is a simple control in which the control target value is switched alternately and stepwise between the maximum value tεMAX and the minimum value tεMIN, the width of the allowable deviation region Δtε is utilized to the maximum, and the control shaft 23 is actively The forward / reverse operation can be performed, and the lubrication performance can be improved by promoting the intervention of the lubricating oil into the bearing portion as described above.

  [3] As shown in FIG. 7, a load F <b> 3 caused by the in-cylinder pressure of the engine and the inertial force of the moving parts acts on the bearing portion of the main shaft 29 of the control shaft 23. Among these loads, the maximum combustion load F0 due to the in-cylinder pressure near the compression top dead center is the largest, and acts as a bending load F3 on the control shaft 23 via the control link 25. Therefore, if the surface pressure maximum points of a plurality of cylinders are concentrated on the same portion of the bearing portion of the main shaft 29, local wear and seizure may occur at that portion.

  Therefore, in order to prevent the maximum combustion loads of a plurality of cylinders from concentrating at the same location, a vibration cycle in swing control, that is, a switching cycle between the maximum value tεMAX and the minimum value tεMIN of the control target value is set. ing. Specifically, the switching cycle is set so as not to coincide with the ignition intervals of the plurality of cylinders. In other words, the swing angular velocity of the swing control is an angular velocity at which the maximum surface pressure point of the bearing portion of the main shaft 29 of the control shaft 23 does not overlap with at least two consecutive combustion timings in the ignition sequence of the cylinder. It is set above. As a result, the maximum surface pressure does not continuously act on the same portion of the bearing portion, so that the above-mentioned problems can be solved and the reliability and durability can be improved.

  [4] In the multi-link variable compression ratio mechanism that changes the engine compression ratio by changing the crown surface height position, that is, the top dead center position of the piston 14 as described above, the compression against the change in the piston top dead center position. The sensitivity of the ratio change is higher at the higher compression ratio side and lower at the lower compression ratio side, and the piston crown surface height per unit angle of the control shaft 23 is lower at the low compression ratio side than at the high compression ratio side. Since the allowance is small, as shown in FIG. 9, the change allowance of the compression ratio with respect to the rotation angle of the control shaft is very small in the vicinity of the minimum compression ratio as compared with the vicinity of the maximum compression ratio.

  Here, as described above, setting the allowable deviation region Δtε before and after the target compression ratio tε is synonymous with performing an operation of repeatedly changing the compression ratio in terms of micro. In particular, when swing control of the control shaft 23 is performed by setting the allowable deviation region Δtε as described above in the vicinity of the highest compression ratio at which the change sensitivity of the compression ratio with respect to the rotation angle of the control shaft 23 is high, the actual engine compression ratio is reduced. The fluctuation becomes relatively large, the fluctuation of the engine output becomes large, and the drivability may be hindered.

  Therefore, the swing control is prohibited in the vicinity of the highest compression ratio where the compression ratio change sensitivity with respect to the rotation angle of the control shaft 23 is high, and the target compression is set near the lowest compression ratio where the compression ratio change sensitivity with respect to the rotation angle of the control shaft 23 is low. The swing control with the allowable deviation region Δtε is performed only in the steady operation state where the ratio is maintained. In the vicinity of this minimum compression ratio, the sensitivity of the change in the compression ratio with respect to the rotation of the control shaft 23 is low. Therefore, even if the swing control is performed, there is little influence on the engine output and the engine operability is not hindered.

  [5] On the other hand, in the vicinity of the maximum compression ratio, since the sensitivity of the change in the compression ratio with respect to the rotation of the control shaft 23 is very high, if the swing control of the control shaft 23 is performed, the engine compression ratio, that is, the engine output is The fluctuation of the engine is large and will adversely affect the engine performance. Therefore, in a steady operation state in which the target compression ratio is maintained near the maximum compression ratio, stable control of the compression ratio is maintained by mechanically holding the rotational position of the control shaft 23 by the cage 43 without performing swing control. It can be performed.

  The operation range near the maximum compression ratio is not a high load range but an operation range from low to medium speed and low to medium load typified by the mode range. It is affected by the in-cylinder pressure of the engine and the inertial force of moving parts. This is an operating state in which the torque F3 acting on the control shaft 23 from the engine side is low. Therefore, by limiting the operation region in which the holding by the cage 43 is performed only to the vicinity of the maximum compression ratio, the cage corresponding to only the lower load side compared to the case in which the holding by the cage 43 is performed in the entire operation region. 43 and the cage 43 can be reduced in size and cost.

  [6] As shown in FIG. 10, since the allowable deviation width changes according to the target compression ratio tε, preferably, the width of the allowable deviation region Δtε is adjusted according to the engine operating state. .

  [7] More specifically, the width of the allowable deviation region Δtε is increased as the target compression ratio tε is lower. As a result, the control shaft 23 can be swung greatly by increasing the width of the allowable deviation region Δtε on the low compression ratio side without causing deterioration in operability due to fluctuations in the engine output accompanying fluctuations in the compression ratio. Fretting occurrence frequency can be further reduced.

  In the case of an internal combustion engine with a supercharger, the supercharging pressure is controlled near the minimum compression ratio. However, since there is a time delay in the rise of the supercharging pressure, even when the compression ratio is set, the load load output by the engine differs depending on the supercharging pressure. In particular, as the supercharging pressure increases, the frequency of occurrence of abnormal combustion such as knocking increases. Therefore, as the load load increases, it is necessary to narrow the allowable deviation region Δtε and strictly control the compression ratio. On the other hand, in a region where supercharging is not performed, since the load applied by the engine is low and the possibility of knocking is low, the compression ratio may be controlled relatively slowly. In this way, by appropriately changing the size of the allowable deviation area according to the supercharging pressure, that is, the load load output by the engine, control is performed to swing the control shaft greatly without causing problems such as knocking. The frequency of occurrence of fretting can be reduced.

  [8] Immediately after the engine is started immediately after the ignition switch is turned on, generally, the actual rotational position of the control shaft 23 corresponding to the actual engine compression ratio and the control shaft sensor 52 for detecting the rotational position of the control shaft 23 are detected. Reference position learning control (initialization control) using the sensor output of the control axis sensor 52 is performed in order to correct and learn the mutual relationship with the detected signal. During the reference position learning control, it is necessary to strictly learn and calibrate the rotational position relationship of the control shaft 23. Therefore, if the allowable deviation region Δtε as described above exists, the reference position learning control cannot be performed satisfactorily. . Therefore, during the reference position learning control, the reference position learning control can be smoothly performed by setting the allowable deviation region Δtε to zero and prohibiting the swing control.

  [9] The link row includes a lower link 21 rotatably attached to the crankpin 17 of the crankshaft 16, and an upper link 22 that links the lower link 21 and the piston 14, and the control link 25 One end is connected to the lower link 21, and the other end is connected to an eccentric shaft portion 24 provided eccentric to the control shaft 23.

  According to such a structure, in addition to being able to continuously change the engine compression ratio, the piston stroke characteristic itself is a preferable characteristic as compared to a single link mechanism in which the piston and the crank pin are connected by a single connecting rod, For example, it can be set to a characteristic close to a single vibration with excellent vibration characteristics. Further, since the control link 25 is connected to the lower link 21, the control link 25, the control shaft 23, the actuator unit 30 and the like can be arranged in a lower region of the crankshaft 16 having a relatively large space, Excellent in engine mounting.

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes without departing from the spirit of the present invention. . For example, in the above embodiment, the clutch 43 is used as a mechanism for mechanically holding the rotational position of the control shaft, but other mechanisms such as a cogging brake may be used.

  Further, the swing control is not limited to the control target value as described above, which is controlled to be switched alternately and stepwise between the maximum value εMAX and the minimum value εMIN of the allowable deviation region Δtε. It may be changed in multiple steps or continuously within Δtε.

Sectional drawing which shows one Example of the variable compression ratio mechanism of the internal combustion engine which concerns on this invention. The disassembled perspective view which shows the final deceleration mechanism of the said variable compression ratio mechanism. Sectional drawing which shows the actuator unit of the said variable compression ratio mechanism. Sectional drawing which follows the ZZ line | wire of FIG. 5 which shows the clutch as a holder | retainer. Sectional drawing which follows the YY line | wire of FIG. 4 which shows the said clutch. The operation explanatory view of the above-mentioned clutch. Explanatory drawing which shows the form of the torque which acts on the control shaft by cylinder pressure. Explanatory drawing which shows an example of the control map of target compression ratio. Explanatory drawing which shows the relationship between the angle of a control shaft, and an engine compression ratio. Explanatory drawing which shows an example of an allowable deviation area | region. The characteristic view which shows an example of the efficiency and output curve of an electric motor. The flowchart which shows the flow of control concerning a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 ... Cylinder 14 ... Piston 16 ... Crankshaft 17 ... Crankpin 21 ... Lower link 22 ... Upper link 23 ... Control shaft 24 ... Eccentric shaft part 25 ... Control link 33 ... Electric motor (drive part)
43 ... Clutch (retainer)
51 ... Control unit 52 ... Control axis sensor

Claims (7)

A link row composed of a plurality of links linking a piston that reciprocates in the cylinder and a crank pin of the crankshaft, a control shaft whose rotational position is changed and held by a drive unit, and a link between the control shaft and the link row And a control device for a variable compression ratio mechanism of an internal combustion engine in which the piston stroke changes according to the rotational position of the control shaft.
Target compression ratio setting means for setting a target compression ratio according to the engine operating state;
Above the target compression ratio predetermined tolerance region comprising, have a, a swing control means for rocking control for rocking the control shaft in the rotational direction,
The control apparatus for a variable compression ratio mechanism of an internal combustion engine, wherein the swing control by the swing control means is executed in a steady operation state where the target compression ratio is maintained near the minimum compression ratio .   2. The control device for a variable compression ratio mechanism of an internal combustion engine according to claim 1, wherein the swing control means alternately sets a maximum value and a minimum value of the allowable deviation region as a control target value.   3. The control device for a variable compression ratio mechanism for an internal combustion engine according to claim 2, wherein a switching cycle of the control target value is set so as not to coincide with an ignition interval of a plurality of cylinders. In operation region where the swing control by the swing control means is not performed, according to any one of claims 1 to 3, characterized in that it has a holding device for mechanically holding the rotational position of the control shaft A control device for a variable compression ratio mechanism of an internal combustion engine. A link row composed of a plurality of links linking a piston that reciprocates in the cylinder and a crank pin of the crankshaft, a control shaft whose rotational position is changed and held by a drive unit, and a link between the control shaft and the link row And a control device for a variable compression ratio mechanism of an internal combustion engine in which the piston stroke changes according to the rotational position of the control shaft.
Target compression ratio setting means for setting a target compression ratio according to the engine operating state;
A swing control means for performing swing control for swinging the control shaft in the rotational direction within a predetermined allowable deviation region including the target compression ratio;
An allowable deviation area setting means for adjusting the width of the allowable deviation area according to the engine operating state,
The control apparatus for a variable compression ratio mechanism for an internal combustion engine, wherein the allowable deviation area setting means increases the width of the allowable deviation area as the target compression ratio is lower . A link row composed of a plurality of links linking a piston that reciprocates in the cylinder and a crank pin of the crankshaft, a control shaft whose rotational position is changed and held by a drive unit, and a link between the control shaft and the link row And a control device for a variable compression ratio mechanism of an internal combustion engine in which the piston stroke changes according to the rotational position of the control shaft.
Target compression ratio setting means for setting a target compression ratio according to the engine operating state;
A swing control means for performing swing control for swinging the control shaft in the rotational direction within a predetermined allowable deviation region including the target compression ratio;
A control axis sensor for detecting the rotational position of the control shaft,
A control apparatus for a variable compression ratio mechanism of an internal combustion engine, wherein a deviation amount of the allowable deviation region is set to zero during execution of reference position learning control of sensor output of the control shaft sensor . The link row is composed of a lower link that is rotatably attached to a crankpin of the crankshaft, and an upper link that links the lower link and the piston,
The control link has one end connected to the lower link, the other end according to any one of claims 1 to 6, characterized in that it is connected to an eccentric shaft part provided eccentrically to the control shaft internal combustion Control device for variable compression ratio mechanism of engine.

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