JP4924479B2 - Variable compression ratio internal combustion engine - Google Patents

Description

  The present invention relates to a variable compression ratio internal combustion engine capable of changing a compression ratio during operation, and more particularly to an arrangement of a mechanism for changing and maintaining the compression ratio.

As a variable compression ratio mechanism that can change the compression ratio during engine operation, for example, Patent Document 1 discloses a feed screw mechanism that converts the rotational motion of a motor into a reciprocating motion of an actuator rod, and a reciprocating motion of an actuator rod that is controlled by a control shaft. A slider crank mechanism that converts to a rotational motion is disclosed.
JP 2007-239520 A

  By the way, the combustion pressure in the cylinder, the inertial force of the main moving parts, and the like are transmitted to the control shaft via each link, and a rotational torque (control shaft torque) around the rotation axis acts on the control shaft. The component of the control shaft torque in the axial direction of the actuator rod is transmitted to the feed screw mechanism via the actuator rod, and converted into torque that rotates the feed screw mechanism. And it acts as a load in the circumferential direction (load F1) on the reduction gear meshing with the feed screw mechanism.

  On the other hand, the actuator rod bends and deforms due to the vertical component of the control shaft torque. As a result, a circumferential load (load F2) acts on the reduction gear meshing with the feed screw mechanism.

  The loads F1 and F2 also act on the pinion gear of the motor that meshes with the reduction gear.

  In the configuration disclosed in Patent Literature 1, since the load acting on the reduction gear and the pinion gear is increased by combining the load F1 and the load F2, in order to maintain the set compression ratio against the control shaft torque. Necessary torque (holding torque) also increases. For this reason, there is a problem that the mechanism for changing and maintaining the compression ratio cannot be made compact.

  Therefore, an object of the present invention is to reduce the load acting on the mechanism for changing / holding the compression ratio and to make the structure compact.

  The variable compression ratio internal combustion engine of the present invention includes a plurality of links that link a piston that reciprocates in a cylinder and a crankpin of a crankshaft, a control shaft whose rotation angle is changed and held by a drive unit, and a rotation of the control shaft A control link that links an eccentric shaft that is eccentric from the center and one of the links, an actuator rod that moves in the axial direction in accordance with the rotational motion of the control shaft, and the axial motion of the actuator rod is converted into rotational motion. A feed screw mechanism and a control shaft rotation control means for controlling the rotation angle of the control shaft linked to the feed screw mechanism via a speed reduction means, and a load acts on the eccentric shaft of the control shaft from the control link during engine operation. Control shaft torque generated by Therefore, due to the component force in the actuator rod axial direction of the load acting on the actuator rod, the acting direction of the load F1 acting on the gear in the meshing portion of the feed screw mechanism and the speed reducing means, and the actuator rod axial direction of the load acting on the actuator rod The control shaft rotation control means is arranged so that the acting direction of the load F2 acting on the gear of the meshing portion of the feed screw mechanism and the speed reducing means is a direction that cancels each other by the component force in the direction substantially orthogonal to the direction.

  Alternatively, a plurality of links that link pistons that reciprocate in the cylinder and a crankpin of the crankshaft, a control shaft whose rotation angle is changed and held by the drive unit, an eccentric shaft that is eccentric from the rotation center of the control shaft, and the above A control link that links one of the plurality of links, and a control shaft rotation control unit that links the control shaft via a speed reduction unit to control the rotation angle of the control shaft, and controls the control shaft from the control link during engine operation. The direction of the action of the load F1 acting on the gear of the meshing part of the control shaft and the speed reduction means by the control shaft torque generated by the load acting on the eccentric shaft of the control shaft, and the load acting on the eccentric shaft of the control shaft from the control link By And the control shaft is deformed, the direction of action of the load F2 acting on the gear meshing portion between the control shaft and the deceleration means such that the direction cancel each other, to place the control shaft rotation control means.

  According to the present invention, since the load F1 and the load F2 act in the direction in which they cancel each other, it acts on the control shaft rotation control means for controlling the rotation angle of the control shaft, that is, the mechanism for changing / holding the compression ratio. The maximum load to be reduced is reduced. Thereby, the mechanism for changing and maintaining the compression ratio can be made compact.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view of an engine provided with a variable compression ratio mechanism of the present embodiment.

  1 is a piston, 2 is a cylinder block, 3 is an upper link, 4 is a lower link, 5 is a control link, 6 is a crankshaft, 7 is a control shaft, 11 is a first link, 12 is a second link, and 13 is an actuator rod. , 16 is a bearing portion, and 17 is a ball screw nut (feed screw mechanism).

  The piston 1 is housed in the cylinder of the cylinder block 2 so as to be able to reciprocate. The control shaft 7 extends in the cylinder row direction substantially parallel to the crankshaft 6. The lower link 4 is connected to the crankpin 6a of the crankshaft 6 so as to be relatively rotatable.

  The upper link 3 is connected to the piston 1 at the upper end and to the lower link 4 at the lower end via a piston pin 1a and a connecting pin 8 so as to be relatively rotatable. The control link 5 has an upper end connected to the lower link 4 and a lower end connected to the control shaft 7 via connection pins 9 and 10 so as to be relatively rotatable. The control link 5 is connected to a position eccentric from the rotation shaft 7a of the control shaft 7. For example, an eccentric cam eccentric to the rotation shaft 7a is provided on the control shaft 7, and the control shaft 7 is attached to the eccentric cam. Link.

  One end of the first link 11 is fixed to the rotating shaft 7a so as to rotate integrally with the control shaft 7, and the other end is connected to one end of the second link 12 via a connecting pin 14 so as to be relatively rotatable. Yes. The other end of the second link 12 is connected to the tip of the actuator rod 13 via a connecting pin 15 so as to be relatively rotatable.

  The actuator rod 13 is inserted into a ball screw nut 17 on the right side (hereinafter referred to as a base end side) in the figure, and is supported by a bearing portion 16 so as to be slidable between the ball screw nut 17 and the end portion on the connecting pin 15 side. ing. In addition, a male screw portion that is screwed with a female screw portion provided on the inner periphery of the ball screw nut 17 is provided in a predetermined range from the base end side.

  2A is a diagram schematically illustrating the configuration of FIG. 1, FIG. 2B is a diagram viewed from the base end side of the actuator rod 13, and FIG. 2C is a diagram illustrating the periphery of the actuator rod 13 viewed from above the engine. FIG. 18 is an intermediate gear having a small diameter portion 18a and a large diameter portion 18b, 19 is a pinion gear, 20 is a compression ratio changing / holding mechanism having both a function as a compression ratio changing mechanism and a function as a compression ratio holding mechanism (control shaft rotation control). Means).

  In the compression ratio changing / holding mechanism 20, a holding mechanism 20a and a motor 20b are arranged in series. The holding mechanism 20a may have a structure that can hold the rotating shaft 20c of the motor 20b so that the rotating shaft 20c does not rotate when control shaft torque described later is transmitted.

  FIG. 7 is a diagram illustrating an example of the holding mechanism 20a. The holding mechanism 20a surrounds the disc 52 fixedly supported on the rotating shaft 20c of the motor 20b, an armature 53 that faces the disc 52, a spring 51 that urges the armature 53 in the direction of the disc 52, and the spring 51. The coil 50 is provided.

  In a state where no voltage is applied to the coil 50, the armature 53 is pressed against the disk 52 by the biasing force of the spring 51, thereby inhibiting the rotation of the rotary shaft 20c. That is, the rotation of the rotating shaft 20c can be prohibited when the frictional force (holding torque) between the armature 53 and the disk 52 is larger than the rotating torque of the rotating shaft 20c. On the other hand, when a voltage is applied to the coil 50, the armature 53 separates from the disk 52 and is attracted to the coil 50 against the urging force of the spring 51, so that the disk 52 is freely rotatable and the rotating shaft 20c is also freely rotatable. Become.

  An outer peripheral gear 17 a is provided on the outer peripheral portion of the ball screw nut 17, and the outer peripheral gear 17 a meshes with the small diameter portion 18 a of the intermediate gear 18. On the other hand, the large diameter portion 18b meshes with a pinion gear 19 provided on the rotating shaft 20c of the motor 20b. In this embodiment, the outer peripheral gear 17a, the intermediate gear 18 and the pinion gear 19 are spur gears, but other gears such as a helical gear may be used.

  As shown in FIGS. 2B and 2C, the ball screw nut 17, the intermediate gear 18, and the pinion gear 19 pass through the central axis of the actuator rod 13 and are on straight lines that are substantially orthogonal to the reciprocating direction of the piston 1, respectively. Arrange them so that their rotation centers are aligned. The intermediate gear 18 is not necessarily required. Depending on the setting of the reduction ratio, the pinion gear 19 and the ball screw nut 17 may be directly engaged with each other, and a desired reduction ratio may be realized by the number of teeth. In the present embodiment, the intermediate gear 18 corresponds to the transmission means.

  When the motor 20b is driven to rotate, the rotation of the motor 20b is decelerated by the intermediate gear 18 and transmitted to the ball screw nut 17, and the actuator rod 13 having a male screw portion screwed with the female screw portion on the inner periphery of the ball screw nut 17 is axially moved. It moves to.

  When the actuator rod 13 moves to the proximal end side, the control shaft 7 rotates around the rotation axis 7a in the counterclockwise direction in the drawing via the second link 12 and the first link 11, and the position of the connecting pin 10 is lowered. . As a result, the lower link 4 is tilted counterclockwise around the crankpin 6a and the position of the connecting pin 8 is raised, so that the position of the piston 1 is raised. That is, the piston ratio at the top dead center position increases, so that the compression ratio increases.

  When the actuator rod 13 moves in the opposite direction, the control shaft 7 and the lower link 4 rotate in the clockwise direction in the figure, so that the piston 1 is lowered and the compression ratio is lowered. That is, in this embodiment, the compression ratio decreases as the actuator rod 13 advances.

  As described above, the variable compression ratio mechanism of the present embodiment includes the upper link 3, the lower link 4, the control link 5, the control shaft 7, the first link 11 and the second link 12, the actuator rod 13, the ball screw nut 17, and the deceleration. An intermediate gear 18 and a motor 20b are provided as means. Then, the drive of the motor 20b is controlled by a control unit (not shown), and the rotation angle of the control shaft 7 is controlled by advancing and retracting the actuator rod 13 according to the operating state, thereby changing the compression ratio.

  Further, as will be described later, the combustion pressure in the cylinder, the inertial force of the piston 1 and the like are transmitted to the control shaft 7 through the upper link 3, the lower link 4 and the control link 5. The transmitted load acts as a load for rotating the control shaft 7 (hereinafter referred to as control shaft torque) because the connecting pin 10 is eccentric from the rotation shaft 7a of the control shaft 7. Therefore, when the compression ratio reaches the target value, a current necessary for holding the control shaft 7 at a predetermined rotation angle against the control shaft torque is supplied to the holding mechanism, and the compression ratio is held at the target value.

  Note that the specific compression ratio control according to the operating state is the same as that disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-115571, and a description thereof will be omitted.

  Next, torque acting on the compression ratio changing / holding mechanism 20 will be described.

  When the in-cylinder combustion load Fburn acts on the piston 1, this load is transmitted to the lower link 4 via the upper link 3, and the lower link 4 rotates clockwise in FIG. 2A with the crank pin 6a as a fulcrum. Acts in the direction of As a result, a load Fcntrl that is pulled in the axial direction of the control link 5 acts on the control shaft 7, and a control shaft torque Tctrl acts on the control shaft 7 in the direction of clockwise rotation in FIG. In the case of a multi-cylinder engine, the control shaft torque Tctrl has the maximum value when the resultant force of the combustion load Fburn of one cylinder and the load due to the inertial force or the like of another cylinder becomes maximum. It almost coincides with the timing when Fburn becomes maximum.

  This control shaft torque Tctrl is transmitted to the second link 12 via the first link 11 and acts as an axial tensile load Fex.

  A component in the axial direction of the actuator rod 13 of the tensile load Fex (hereinafter referred to as the load Fexh) is converted into a rotational torque of the ball screw nut 17, and a circumferential load F 1 acts on the intermediate gear 18 meshing with the ball screw nut 17. The male screw portion of the actuator rod 13 and the female screw portion of the ball screw nut 17 are set so that the load F1 is upward in FIG.

  Further, due to the actuator rod axial direction vertical component Fexv1 (upward in FIG. 2A) of the tensile load Fex, the actuator rod 13 has the bearing portion 16 as a fulcrum within the clearance range of the bearing portion 16 as shown in FIG. Rotate clockwise. As a result, a downward load Fexv2 in FIG. 2A is applied to the portion of the actuator rod 13 that is closer to the ball screw nut 17 than the bearing portion 16, and the intermediate gear 18 that meshes with the ball screw nut 17 by this load Fexv2 is applied. The circumferential load F2 in the circumferential direction and downward in FIG. 2A acts.

  The resultant force of these loads F1 and F2 acts as a rotational torque on the compression ratio changing / holding mechanism 20 via the pinion gear 19.

  On the other hand, when the inertial force of the piston 1, the links 3, 4, 5, etc. acts as in the compression stroke or the exhaust stroke, each load and torque act in the opposite directions. Since the load acting on the control shaft 7 is the resultant force of the inertial force and the combustion load, the load acting on the compression ratio changing / holding mechanism 20 during actual operation is an alternating load.

  According to the configuration shown in FIGS. 2A to 2C, the load F1 and the load F2 act in the direction of canceling out, so the maximum value of the rotational torque transmitted to the compression ratio changing / holding mechanism 20 is reduced. To do. For this reason, the load applied to the holding mechanism 20a when the compression ratio is held at the set value can be reduced.

  Depending on the geometry of the first link 11 and the second link 12, the arrangement of the intermediate gear 18 and the pinion gear 19 in such a direction that the load F1 and the load F2 cancel each other is shown in FIGS. May be different. Also in this case, at least when the control shaft torque Tctrl reaches the maximum value, the intermediate gear 18 and the like are arranged so that the load F1 and the load F2 act in opposite directions. Thereby, since the maximum value of the rotational torque transmitted to the compression ratio changing / holding mechanism 20 is reduced, the load on the holding mechanism 20a can be reduced.

  Further, when the component Fexv1 of the load Fex acting on the actuator rod 13 in the direction orthogonal to the axial direction of the actuator rod 13 becomes maximum, that is, when the load F2 becomes maximum, the load F1 and the load F2 cancel each other. If the intermediate gear 18 and the pinion gear 19 are arranged so as to act in the direction in which the sound is transmitted, it is possible to avoid a decrease in sound vibration performance. This is because the displacement of the ball screw nut 17 in the direction perpendicular to the axial direction of the actuator rod 13 increases the impact force at the time of collision with the intermediate gear 18 and decreases the sound vibration performance. This is because the impact force can be reduced by making the load F1 and the load F2 cancel each other.

  As described above, in the present embodiment, the following effects can be obtained.

  (1) A plurality of links 3, 4 that link the piston 1 and the crankpin 6 a, a control shaft 7, a control link 5 that links the eccentric shaft eccentric from the rotating shaft 7 a of the control shaft 7 and the lower link 4. The actuator rod 13 that moves in the axial direction in accordance with the rotational movement of the control shaft 7, the ball screw nut 17 that converts the axial movement of the actuator rod 13 into the rotational movement, and the ball screw nut 17 are linked via the intermediate gear 18. A compression ratio changing / holding mechanism 20 for controlling the rotation angle of the control shaft 7, and a ball screw nut 17 and an intermediate gear 18 by a component force Fexh in the actuator rod axial direction of a load acting on the actuator rod 13 by the control shaft torque. To the gear of the meshing part with The load acting on the meshing portion of the outer peripheral gear 17a of the ball screw nut 17 and the intermediate gear 18 by the component force Fexv1 in the direction substantially perpendicular to the direction of the actuator rod axis of the load acting on the actuator rod 13 Since the compression ratio changing / holding mechanism 20 is arranged so that the acting direction of F2 is a direction that cancels each other, the holding torque required for the holding mechanism 20a can be reduced.

  (2) Since the compression ratio changing / holding mechanism 20 is arranged so that the acting direction of the load F1 and the acting direction of the load F2 cancel each other at least when the control shaft torque reaches the maximum value, the load F1 Even when the acting direction of the load F2 changes depending on the compression ratio or the direction of the load acting from the control link, the maximum value of the resultant force of the load F1 and the load F2 can be reduced. For this reason, the maximum value of holding torque can be reduced effectively.

  (3) When the component force Fexv1 in the direction substantially orthogonal to the actuator rod axis direction of the load Fex acting on the actuator rod 13 by at least the control shaft torque becomes the maximum value, the acting direction of the load F1 and the acting direction of the load F2 Since the compression ratio changing / holding mechanism 20 is arranged so that the directions cancel each other, the amount of radial displacement of the ball screw nut 17 can be reduced. Thereby, the impact force when the outer peripheral gear 17a of the ball screw nut 17 collides with the intermediate gear 18 is reduced, and the deterioration of the sound vibration performance can be avoided.

  In addition, as shown in FIGS. 2A to 2C, the load F1 and the load F2 are not limited to acting on the same line in opposite directions. For example, the acting direction of the load F2 is relative to the acting direction of the load F1. If it is shifted by 90 degrees or more, the effect of reducing the load on the holding mechanism 20a due to the offset between the load F1 and the load F2 can be obtained.

  A second embodiment will be described.

  3A is a schematic view seen from above the engine around the control shaft 7 of the present embodiment, FIG. 3B is a sectional view taken along line II-II in FIG. 3A, and FIG. It is the figure which looked at the mode of deformation of control shaft 7 at the time of having done from the engine side.

  In the engine to which the present embodiment is applied, the piston 1, the upper link 3, the lower link 4, the control link 5, the crankshaft 6 and the control shaft 7 have the same configuration as in FIG. However, it differs in that the control shaft 7 is directly driven to rotate by the motor 20b without using the first link 11, the second link 12, the actuator rod 13 and the ball screw nut 17.

  Specifically, as shown in FIG. 3A, a gear portion 21 is provided at one end portion of the control shaft 7, and the gear portion 21 and a pinion gear 19 provided at the end portion of the rotating shaft of the motor 20b are provided. I'm engaged. Note that reference numeral 22 in FIG. 3A denotes a speed reduction unit (speed reduction means) interposed between the motor 20b and the pinion gear 19. Similar to the first embodiment, the speed reduction unit 22 is not necessarily required and may not be provided depending on the setting of the speed reduction ratio.

  The motor 20b is arranged so that the rotation center of the gear portion 21 and the rotation center of the pinion gear 19 are aligned on a straight line that is substantially orthogonal to the reciprocating motion direction of the piston 1.

  When the combustion load Fburn is applied in the configuration as described above, the load Fcntrl pulled in the axial direction of the control link 5 acts at the position of the connecting pin 10 of the control shaft 7 as in the first embodiment, and the control shaft 7, the control shaft torque Tcntr1 acts. A circumferential load F1 acts upward on the pinion gear 19 that meshes with the gear portion 21.

  On the other hand, as shown in FIG. 3 (c), the control shaft 7 undergoes bending deformation with the load Fcntrl as the fulcrum of the main bearing portion 23. A downward load F <b> 2 acts on the meshing portion between the gear portion 21 and the pinion gear 19. The resultant force of these loads F1 and F2 acts as rotational torque on the motor 20b via the pinion gear 19.

  As in the first embodiment, when an inertial load is applied, the directions of the load and torque are opposite to the above.

  By the way, in the present embodiment, the rotation centers of the gear portion 21 and the pinion gear 19 are arranged on a straight line substantially orthogonal to the axial direction of the control shaft 7 and the load F1 is upward in FIG. Since the motor 20b is disposed, the load F1 and the load F2 act in opposite directions. Therefore, as in the first embodiment, the load F1 and the load F2 cancel each other, and the maximum value of the rotational torque transmitted to the motor 20b can be reduced. As a result, the maximum torque required for the motor 20b to hold the compression ratio at the set value is reduced, so that the motor 20b can be miniaturized and the compression ratio changing / holding mechanism 20 can be made compact. Become.

  In the case of a multi-cylinder engine as shown in FIGS. 3A and 3B, the load acting on the control shaft 7 from the control link 5 of the cylinder closest to the gear portion 21 meshing with the pinion gear 19 is the maximum. At this time, as shown in FIG. 3B, the pinion gear 19 is arranged at a position where the acting direction of the load F1 and the acting direction of the load F2 cancel each other. This is because when the load acting on the control shaft 7 from the control link 5 of the cylinder closest to the gear portion 21 becomes maximum, the displacement of the gear portion 21 becomes maximum. At this time, the load F1 and the load F2 This is because the maximum value of the fluctuation torque acting on the compression ratio changing / holding mechanism 20 is reduced.

  As described above, in the present embodiment, the following effects can be obtained.

  (1) A plurality of links 3, 4 that link the piston 1 and the crankpin 6 a, a control shaft 7, a control link 5 that links the eccentric shaft eccentric from the rotating shaft 7 a of the control shaft 7 and the lower link 4. A compression ratio changing / holding mechanism 20 that is linked to the control shaft 7 via the speed reduction portion 22 and controls the rotation angle of the control shaft 7, and is provided with an engagement portion between the control shaft 7 and the speed reduction portion 22 by the control shaft torque. The control shaft 7 is deformed by the acting direction of the load F1 acting on the gear and the load acting on the eccentric shaft of the control shaft 7 from the control link 5, and acts on the gear of the meshing portion of the control shaft 7 and the speed reduction portion 22. The acting direction of the load F2 is a direction in which they cancel each other. Sea urchin, since placing the compression ratio changing and holding mechanism 20, it is possible to reduce the holding torque required of the holding mechanism 20a.

  (2) In a multi-cylinder internal combustion engine that controls the compression ratio of all cylinders with one compression ratio changing / holding mechanism 20 and the control shaft 7, control is performed from the control link 5 that is at least closest to the compression ratio changing / holding mechanism 20. When the load acting on the eccentric shaft of the shaft 7 becomes maximum, that is, when the displacement of the gear portion 21 of the control shaft 7 meshing with the speed reduction portion 22 becomes maximum, the load F1 and the load F2 cancel each other. Since the compression ratio changing / holding mechanism 20 is arranged as described above, the maximum value of the fluctuation torque acting on the compression ratio changing / holding mechanism 20 can be reduced.

  A third embodiment will be described.

  This embodiment is different from the first and second embodiments in that the holding mechanism 20a and the motor 20b are independent.

  FIG. 4A is a view of the periphery of the ball screw nut 17 as seen from the axial direction of the actuator rod 13 as in FIG. 2B. FIG. 4B is a view of FIG. 4A viewed from above the engine.

  The intermediate gear 18, the pinion gear 19, and the holding mechanism 20a are arranged in the same manner as in FIG. However, the motor 20 b is disposed via the intermediate gear 30 at a position symmetrical to the holding mechanism 20 a with respect to the rotation axis of the ball screw nut 17.

  With such a configuration, the intermediate gear 18 and the holding mechanism 20a are the same as in the first embodiment, but the intermediate gear 30 on the motor 20b side has a ball screw nut at a position where the load F1 and the load F2 are strengthened. 17 will be engaged. For this reason, a larger torque with the load F1 and the load F2 strengthening each other acts on the motor 20b.

  However, the motor 20b is driven so that the compression ratio becomes a set value (target compression ratio). For example, the amount of movement of the actuator rod 13 necessary to achieve the target compression ratio is calculated from the difference between the current piston top dead center position and the piston top dead center position at the target compression ratio, and the ball is calculated based on this movement amount. The rotation angle of the screw nut 17 is calculated. And the electric power supplied to the motor 20b is determined based on this rotation angle. Here, if the actual compression ratio does not reach the target compression ratio even if the electric power is supplied to the motor 20b due to the above-described fluctuating torque due to the combustion load or the like, it is further increased until the target compression ratio is reached. What is necessary is just to supply electric power.

  On the other hand, if the actuator rod 13 is moved by the varying torque against the holding force of the holding mechanism 20a, the holding mechanism 20a cannot be returned to the state before the movement.

  As described above, the motor 20b is less affected by the increase of the fluctuation torque than the holding mechanism 20a. Therefore, the motor 20b can be disposed at a position where the load F1 and the load F2 are strengthened as shown in FIG.

  Further, when the motor 20b and the holding mechanism 20a are arranged in parallel as shown in FIG. 4, the actuator rod shaft is compared with the case where the motor 20b and the holding mechanism 20a are arranged in series as shown in FIG. The length in the direction can be shortened, and the entire compression ratio changing / holding mechanism 20 can be made compact.

  FIG. 6 shows the relationship between the speed reduction ratio between the motor 20b and the control shaft 7 and the response time (compression ratio variable response time) when changing the compression ratio, and the relationship between the holding mechanism 20a and the control shaft 7. It is a figure which shows the relationship between a reduction ratio and the torque at the time of hold | maintaining against the load which acts (holding torque). The solid line in FIG. 6 is the compression ratio variable response time when the compression ratio is increased (the compression ratio is higher than the current level) and the compression ratio is decreased (the compression ratio is lower than the current level), and the broken line is the holding torque characteristic. Is shown.

  The compression ratio variable response time depends on the steady motor rotation speed determined based on the load torque acting on the actuator rod 13 from the control shaft 7, the torque of the motor 20b, the gear efficiency from the motor 20b to the ball screw nut 17, and the friction of the bearing portion 16. As shown in FIG. 6, the compression ratio variable response time when the compression ratio is increased becomes shorter as the speed reduction ratio increases in a range where the speed reduction ratio is small, but when the speed ratio exceeds a predetermined speed reduction ratio, the speed reduction ratio is increased. It becomes longer with the increase of. Further, the compression ratio variable response time when the compression ratio is reduced becomes longer in proportion to the increase of the reduction ratio over the entire reduction ratio range.

  A shorter compression ratio variable response time is desirable, and in particular, a shorter compression ratio variable response time when lowering the compression ratio is effective for avoiding knocking. In view of this, the range of the reduction ratio is such that the compression ratio variable response time when reducing the compression ratio is as short as possible within the range where the compression ratio variable response time when allowing a high compression ratio is acceptable. The number of teeth of the pinion gear 31 and the intermediate gear 30 is set so that the reduction ratio between the motor 20b and the control shaft 7 falls within this range.

  On the other hand, the holding torque decreases in inverse proportion to the increase in the reduction ratio. In order to avoid an increase in the size of the holding mechanism 20a, it is desirable that the holding torque is small.

  Therefore, the reduction ratio range in which the holding torque is reduced is set as the target range 2, and the number of teeth of the pinion gear 19 and the intermediate gear 18 is set so that the reduction ratio between the holding mechanism 20a and the control shaft 7 is in this range.

  As shown in FIG. 6, the target range 1 is smaller than the target range 2. That is, the reduction ratio between the motor 20b and the control shaft 7 is smaller than the reduction ratio between the holding mechanism 20a and the control shaft 7.

  Thus, by setting the reduction ratio between the motor 20b and the control shaft 7 and the reduction ratio between the holding mechanism 20a and the control shaft 7, the compression ratio variable response time is shortened, and the holding mechanism 20a Can be miniaturized.

  In addition, as long as the motor 20b is arrange | positioned in parallel with the holding | maintenance mechanism 20a, you may arrange | position in places other than the position where the load F1 and the load F2 strengthen. For example, as shown in FIG. 5, the holding mechanism 20a may be arranged on the opposite side of the ball screw nut 17 with respect to the motor 20b. FIGS. 5A and 5B correspond to FIGS. 4A and 4B, respectively.

  5A and 5B, both the motor 20b and the holding mechanism 20a are arranged so that the loads F1 and F2 cancel each other, and both are arranged in parallel. It will be. Also in this case, the reduction ratio between the motor 20b and the control shaft 7 is set to be smaller than the reduction ratio between the holding mechanism 20a and the control shaft 7.

  The configuration of this embodiment can also be applied to a configuration in which the control shaft 7 is directly driven as shown in FIG.

  As described above, in the present embodiment, in addition to the same effects as those in the first and second embodiments, the following effects can be further obtained.

  (1) The compression ratio changing / holding mechanism 20 includes a motor 20b and a holding mechanism 20a, and at least the holding mechanism 20a is disposed at a position where the loads F1 and F2 cancel each other. The holding mechanism 20a can be arranged in parallel, whereby the compression ratio changing / holding mechanism 20 as a whole can have a compact configuration.

  (2) Since the reduction ratio between the holding mechanism 20a and the control shaft 7 is larger than the reduction ratio between the motor 20b and the control shaft 7, the compression ratio variable response time can be shortened and the holding mechanism 20a can be downsized. it can.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

It is a schematic block diagram of the engine by 1st Embodiment. (A) is a diagram schematically showing the configuration of the engine according to the first embodiment, (b) is a diagram of the periphery of a ball screw nut as viewed from the actuator rod axial direction, and (c) is a diagram of the same as viewed from above the engine. . (A) Schematic configuration diagram around the control shaft of the second embodiment, (b) is a sectional view taken along line II-II of (a), (c) is a diagram showing the state of bending deformation of the control shaft. is there. (A) is the figure which looked at the ball screw nut periphery of 3rd Embodiment from the actuator rod axial direction, (b) is the figure which looked from the engine upper direction similarly. (A) is the figure which looked at the ball screw nut periphery of the other example of 3rd Embodiment from the actuator rod axial direction, (b) is the figure seen similarly from engine top. It is a figure showing the relationship between compression ratio variable response time and holding torque, and reduction ratio. It is a figure showing an example of a holding mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piston 3 Upper link 4 Lower link 5 Control link 6 Crankshaft 7 Control shaft 11 1st link 12 2nd link 13 Actuator rod 17 Ball screw nut 18 Intermediate gear 19 Pinion gear 20 Compression ratio variable and holding mechanism 30 Intermediate gear 31 Pinion gear 50 Coil 51 Spring 52 Disc 53 Armature

Claims (7)

A plurality of links that link a piston that reciprocates in the cylinder and a crankpin of the crankshaft;
A control shaft extending substantially parallel to the crankshaft;
A control link that links an eccentric shaft that is eccentric from the rotation center of the control shaft and one of the plurality of links;
An actuator rod that moves in an axial direction along with the rotational movement of the control shaft;
A feed screw mechanism for converting the axial motion of the actuator rod into rotational motion;
Control shaft rotation control means for controlling the rotation angle of the control shaft linked to the feed screw mechanism via a transmission means,
The feed screw mechanism and the actuator rod in the actuator rod axial direction by the component force in the actuator rod axial direction of the load acting on the actuator rod by the control shaft torque generated by the load acting on the eccentric shaft of the control shaft from the control link during engine operation. It acts between the feed screw mechanism and the transmission means by the acting direction of the load F1 acting between the transmission means and the component force in the direction substantially perpendicular to the actuator rod axial direction of the load acting on the actuator rod. The variable compression ratio internal combustion engine, wherein the control shaft rotation control means is arranged so that the acting direction of the load F2 is a direction that cancels each other. A plurality of links that link a piston that reciprocates in the cylinder and a crankpin of the crankshaft;
A control shaft extending substantially parallel to the crankshaft;
A control link that links an eccentric shaft that is eccentric from the rotation center of the control shaft and one of the plurality of links;
Control shaft rotation control means for controlling the rotation angle of the control shaft linked to the control shaft via a transmission means,
An operation direction of a load F1 acting between the control shaft and the transmission means by a control shaft torque generated by a load acting on the eccentric shaft of the control shaft from the control link during engine operation;
The control shaft is deformed by the load acting on the eccentric shaft of the control shaft from the control link, and the acting direction of the load F2 acting between the control shaft and the transmission means is a direction that cancels each other out. Thus, the variable compression ratio internal combustion engine characterized by disposing the control shaft rotation control means.   The control shaft rotation control means includes a motor for rotating the control shaft and a holding mechanism for holding the rotation angle of the control shaft, each independently linked to a feed screw mechanism, and for the load F1. 3. The variable compression ratio internal combustion engine according to claim 1, wherein at least the holding mechanism is disposed at a position where the action direction and the action direction of the load F <b> 2 cancel each other.   The motor and the holding mechanism are linked to a control shaft at different reduction ratios, and a reduction ratio between the holding mechanism and the control shaft is larger than a reduction ratio between the motor and the control shaft. The variable compression ratio internal combustion engine according to claim 3.   The control shaft rotation control means is arranged such that at least when the control shaft torque reaches a maximum value, the direction of action of the load F1 and the direction of action of the load F2 cancel each other. The variable compression ratio internal combustion engine according to any one of claims 1 to 4.   When the component force in the direction substantially orthogonal to the actuator rod axial direction of the load acting on the actuator rod by at least the control shaft torque becomes the maximum value, the acting direction of the load F1 and the acting direction of the load F2 are mutually The variable compression ratio internal combustion engine according to any one of claims 1, 3 and 4, wherein the control shaft rotation control means is arranged so as to cancel each other. In the multi-cylinder internal combustion engine that controls the compression ratio of all cylinders with the one control shaft rotation control means and the control shaft,
When the load acting on the eccentric shaft of the control shaft is maximized from the control link located at least closest to the control shaft rotation control means, the acting direction of the load F1 and the acting direction of the load F2 are mutually The variable compression ratio internal combustion engine according to any one of claims 2 to 4, wherein the control shaft rotation control means is arranged so as to be in a direction to cancel each other.

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