JP4341392B2 - Variable compression ratio device for internal combustion engine - Google Patents

Description

  The present invention relates to a variable compression ratio device for an internal combustion engine that controls the compression ratio of a cylinder according to operating conditions.

  The present applicant first uses a multi-link type piston-crank mechanism as a compression ratio variable device for a reciprocating internal combustion engine, and changes the piston top dead center position by movably controlling a part of the link. Various proposals have been proposed (for example, see Patent Document 1).

  The compression ratio variable device described in Patent Document 1 connects a piston pin of a piston and a crank pin of a crankshaft via an upper link and a lower ring, and connects a control link that restricts the operation of the link to the lower link. By variably operating the swing fulcrum of the control link, the compression ratio of the cylinder determined by the piston top dead center position can be arbitrarily changed.

  In the case of this variable compression ratio device, the cylinder block is provided with a control shaft parallel to the crankshaft, and an eccentric cam that forms the swing fulcrum of the control link is integrally provided on the control shaft. The eccentric cam is provided eccentrically with respect to the main bearing of the control shaft, and one end of the control link is rotatably supported by the eccentric cam, and the center position of the eccentric cam is operated by the rotation operation of the control shaft. Thereby, the compression ratio of the cylinder is arbitrarily changed. The control shaft is operated by an operation shaft of an actuator that moves forward and backward in accordance with operating conditions, and the operation shaft and the control shaft are linked via a drive transmission mechanism as described below.

  That is, as shown in FIG. 7, the drive transmission mechanism is configured to freely rotate a pin support hole 2 provided at the tip of the operating shaft 1 of the actuator and a central large-diameter portion 3a in the pin support hole 2. The supported connecting pin 3, a pair of arm members 5, 5 provided on the outer circumference of the control shaft 4 and spaced apart in the axial direction, and one end of each arm member 5, 5 along the axial direction is radial. And both ends of the connecting pin 3 supported by the pin support hole 2 are slidably engaged with the slits 6 of both arm members 5 and 5. . In this drive transmission mechanism, when the operating shaft 1 is advanced or retracted by an actuator, the connecting pin 3 slides in the slits 6 of both arm members 5 and 5 and the control shaft 4 is rotated, so that the operating shaft 1 is advanced and retracted. Is transmitted to the control shaft 4 as a rotation operation.

The arm members 5 and 5 are disposed between the main bearing 7 of the control shaft 4 and the eccentric cam 8 adjacent to the main bearing 7. Further, reference numeral 9 in FIG. 7 denotes a conversion ring for converting the rotation of the actuator into the advance / retreat operation of the operation shaft 1.
JP 2002-115571 A

  However, in this conventional variable compression ratio device, the operating shaft 1 supports the connecting pin 3 so as to be rotatable, and both ends of the connecting pin 3 are engaged with the slits 6 of the pair of arm members 5 and 5 of the control shaft 4. Because of the combined drive transmission mechanism, it is difficult to form the arm members 5 and 5 on the control shaft 4 and it is difficult to process the slits 6 in each arm member 5 with high accuracy.

  That is, in this apparatus, since the pair of arm members 5 and 5 are arranged close to each other on the axis of the control shaft 4, the arm member 5 is not only difficult to manufacture by forging, but also manufactured by casting. , The removability when the 5 part is removed from the mold is deteriorated. In particular, in order to widen the rotation range of the control shaft 4 (in order to widen the variable range of the compression ratio), it is necessary to ensure a long slit 6 of the arm member 5, but in order to ensure a long slit 6 length. If the extension lengths of both arm members 5 and 5 are increased, it becomes more difficult to remove the die.

  Further, when the slits 6 are formed in both the arm members 5 and 5, it is necessary to perform cutting and polishing at the same time on the both arm members 5 and 5 so that the slit positions of both are accurately matched. Since the main bearing 7 and the eccentric cam 8 protrude from the outer peripheral surface of the control shaft 4, it is difficult to perform simultaneous machining due to space constraints, and it is impossible to achieve sufficient machining accuracy. It is. And since the processing accuracy of both the slits 6 and 6 cannot be sufficiently increased, unnecessary gaps and friction are easily generated between the slits 6 and 6 and the connecting pin 3, and when the gap is large, Due to the explosion impact during engine operation and the alternating load due to the inertial mass, abnormal noise is likely to be generated in the gap portion, and if the friction is large, the energy loss during the operation of the actuator becomes large. Moreover, there is a concern that misalignment between the slits 6 and 6 may cause the operation of the connecting pin 3 and thus the operation of the control link to be inaccurate, leading to a decrease in the control accuracy of the compression ratio.

  Therefore, the present invention provides a variable compression ratio device for an internal combustion engine that can reduce the manufacturing cost, reduce the energy loss, and improve the control accuracy by making the drive transmission mechanism easy and highly accurate. Is to provide.

  As a means for solving the above-described problems, the present invention projects a single plate-like arm member having a slit along the axial direction, one end of which is open radially outward, on the outer periphery of the control shaft. A pair of parallel support pieces each having a pin support hole formed coaxially is formed at the tip of the actuator operating shaft, and both ends of the connecting pin are rotatably supported by the pin support holes of both support pieces. At the same time, the both support pieces are arranged on both sides of the arm member so as to sandwich the arm member therebetween, and the intermediate portion of the connecting pin is slidably engaged with the slit of the arm member.

  In the case of the present invention, when the operation shaft is advanced and retracted by operating the actuator, the connecting pin rotates in the support holes of both support pieces that support both ends thereof, and slides in the slit of the arm member while moving the control shaft. Rotate.

  In the present invention, since the arm member protruding from the control shaft has a single plate shape, casting, forging, or connecting a separate member to the outer peripheral surface of the control shaft in which the axial space is limited. The arm member can be easily provided. And the slit provided in an arm member can also be processed easily with high precision since the arm member is a single plate. Therefore, according to the present invention, it is possible to reduce the manufacturing cost, reduce the unnecessary gap between the slit and the connecting pin, the occurrence of friction, etc., reduce the energy loss and improve the compression ratio control accuracy. Can be achieved.

  Next, each embodiment of the present invention will be described with reference to the drawings.

  1 to 3 and FIGS. 4C and 4D show a first embodiment of the present invention, and FIG. 2 is a cross-sectional view showing the entire variable compression ratio device of this embodiment. is there.

  As shown in FIG. 2, a piston 13 is slidably accommodated in a cylinder 12 formed in the cylinder block 11, and an upper end portion of an upper link 15 can swing on a piston pin 14 of the piston 13. It is connected. On the other hand, the crank pin 17 of the crankshaft 16 supports a central portion of a substantially triangular lower link 18 so as to be rotatable. One end of the lower link 18 is connected to the lower end of the upper link 15 with a first connecting pin 19. It is connected so as to be swingable.

  A control shaft 20 is rotatably disposed at the lower end of the cylinder block 11 in parallel with the crankshaft 16, and an eccentric cam 21 is integrally provided on the control shaft 20 so as to be eccentric with respect to the bearing center. ing. The base end of the control link 22 is rotatably supported on the outer periphery of the eccentric cam 21, and the tip end portion of the control link 22 swings to the other end of the lower link 18 via the second connecting pin 23. Connected as possible. The center of the eccentric cam 21 forms a swing fulcrum of the control link 22, and its center position changes as the control shaft 20 rotates. When the center position of the eccentric cam 21 changes due to the rotation of the control shaft 20, the operation restraint condition of the lower link 18 by the control link 22 changes, the top dead center position of the piston 14 changes, and eventually the engine compression. The ratio will be changed. The control shaft 20 is provided with a number of eccentric cams 21 corresponding to each cylinder, and the pistons 14 of all the cylinders are similarly controlled by the control link 22.

  The control shaft 20 is rotated by the operation shaft 25 of the actuator 24. The actuator 24 includes an operation shaft 25 that is housed in a casing 26 so as to be able to advance and retreat, and a cylindrical member 27 that is screwed into a male screw portion on the proximal end side of the operation shaft 25. The rotation is controlled by a motor or the like according to the conditions, so that the operation shaft 25 moves forward and backward. The operation shaft 25 of the actuator 24 and the control shaft 20 are connected by a drive transmission mechanism 28 as shown in FIGS.

  The drive transmission mechanism 28 is a single piece provided between the main bearing 29 (the bearing for rotatably supporting the control shaft 20 on the lower portion of the cylinder block 11) at the center of the control shaft 20 and the eccentric cam 21. A plate-like arm member 30, a slit 31 formed in the arm member 30 so as to open radially outward and along the axial direction and the radial direction of the arm member 30, and the operation shaft 25 of the actuator 24 A pair of parallel plate-like support pieces 32, 32 projecting in a bifurcated manner at the tip, and pin support holes 33, 33 formed coaxially at positions opposed to the support pieces 32, 32, respectively; A connecting pin 34 having both ends rotatably fitted in the pin support holes 33, 33 of the support pieces 32, 32, and a slit of the arm member 30 at the substantially axial center of the connecting pin 34. Width slidably engaged with 31 5 is formed.

  The arm member 30 is integrally formed with the control shaft 20 by casting or forging, and extends in the direction perpendicular to the axis so that the axial direction of the control shaft 20 is the plate thickness direction, and extends in the direction perpendicular to the axis. The slit 31 is formed on the leading end surface of the protruding portion. Further, the connecting pin 34 has both end portions 37, 37 having a large diameter with respect to the axial intermediate portion 36 in which the two-surface width 35 is formed, and the large diameter portions at both ends are rotated to the pin support holes 33, 33. It is movably fitted.

  The operation shaft 25 is assembled to the arm member 30 of the control shaft 20 in a state where the large-diameter portion 37 of the connecting pin 34 is supported by both support pieces 32 and 32. Specifically, the support pieces 32, 32 that support the connecting pin 34 are arranged so as to sandwich the arm member 30 from both sides in the axial direction, and the two-surface width 35 portion of the connecting pin 34 slides on the slit 31 of the arm member 30. Fits freely. Therefore, when the operating shaft 25 is advanced or retracted by driving the actuator 24, the connecting pin 34 slides in the slit 31 of the arm member 30 while rotating in the pin support hole 33. At this time, the operating shaft 25 is advanced or retracted. Is converted into a rotation operation and transmitted to the control shaft 20.

  Here, the dimension of each part, such as the arm member 30, the connecting pin 34, the support piece 32, is set like the following formula | equation (1)-(3) (refer FIG. 3).

L3 (L4)>L5> L6 (1)
L3; width L4 between the support pieces 32, 32; axial length L5 of the intermediate portion 36 (small diameter portion) of the connecting pin 34; axial length L6 of the two-surface width 35 of the connecting pin 34; Axial width L1> L2 (2)
L1; distance L2 between the adjacent eccentric cam 21 and the main bearing 29; maximum width of both support pieces 32 in the axial direction of the control shaft 20 D2> D1 (3)
D2: Diameter D1 of the intermediate portion 36 of the connecting pin 34; Diameter of the end portion 37 of the connecting pin 34 First, formula (1) will be described. This is the two-sided width 35 of the connecting pin 34 and both support pieces 32, 32. The relationship between the width between the support member 32 and the axial width of the arm member 30 is defined, and the axial length L5 of the two-surface width 35 is set smaller than the width L3 between the support pieces 32, 32. The large-diameter portion (end portion 37) of the connecting pin 34 can be fitted with a sufficient width into the pin support hole 33, and the two-surface width 35 is made larger than the axial width L6 of the arm member 30. The arm member 30 is always reliably engaged in the slit 31. As for the relationship of L3> L5, when this is the opposite, the fitting width between the connecting pin 34 and the pin support hole 33 is reduced by the two-sided width 35 entering the pin support hole 33, and the connection during engine operation is reduced. The backlash in the axial direction of the pin 34 increases, and as a result, the connecting pin 34 easily interferes with the eccentric cam 21 and the main bearing 29, but such a problem can be reliably avoided by the above setting.

  Expression (2) defines the maximum width L2 of the two support pieces 32. By setting the maximum width L2 of the two support pieces 32 smaller than the interval L1 between the eccentric cam 21 and the main bearing 29, the operation is performed. The support piece 32 is prevented from interfering with the eccentric cam 21 and the main bearing 29 when the shaft 25 is advanced or retracted.

  Equation (3) defines the diameter of the connecting pin 34, and the contact surface pressure with the pin support hole 33 is increased by setting the diameter of both end portions 37 to be larger than the diameter of the central portion 36. The durability of the connecting pin 34 and the pin support hole 33 is improved.

  As a matter of course, since both support pieces 32 and 32 of the operation shaft 25 are disposed on both sides in the axial direction of the arm member 30, the axial width L6 of the arm member 30 and the width L3 between the support pieces 32 and 32 are provided. Is in a relationship of L6 <L3.

  As described above, the drive transmission mechanism 28 of the variable compression ratio device is provided with the single-plate arm member 30 integrally formed on the control shaft 20, the slit 31 is formed in the arm member 30, and the operation shaft 25. Since the intermediate portion 36 of the connecting pin 34 that is rotatably supported by the support piece 32 on the side is slidably engaged with the slit 31, molding of each part of the drive transmission mechanism 28, in particular, an arm The member 30 and the slit 31 can be easily formed.

  That is, when the arm member 30 is formed by casting, the arm member 30 is not close to the other members, so that the mold release property is improved. In addition, when the arm member 30 is formed by forging, the control shaft 20 is formed by crimping a pair of rods, and at this time, by using the growth thickness of the crimping portion of both rods, the arm member is obtained. 30 can be molded.

  The formation of the slit 31 will be described in detail below with reference to FIG. 4 (a) and 4 (b) show what corresponds to the prior art of FIG. 7, and FIGS. 4 (c) and 4 (d) show the first embodiment.

  As shown in FIGS. 4A and 4B, in the case of the prior art in which a pair of parallel arm members 5 and 5 are integrally formed on the control shaft 4, two cutters 40 and 40A are connected to both arm members 5 and 5, respectively. It is desirable in terms of processing accuracy that the slits 6 and 6 are simultaneously processed. However, in the conventional structure in which the pair of arm members 5 and 5 are provided on the control shaft 4, the distance between the arm member 5 with respect to the main bearing 7 and the eccentric cam 8 must be narrowed. , 40A interferes with the main bearing 7 and the eccentric cam 8. For this reason, in the conventional one, each arm member 5 must be cut separately using a single cutter 40, and the positional accuracy of the slits 6 and 6 of both arm members 5 and 5 is increased. I could not.

  On the other hand, as shown in FIGS. 4C and 4D, in this embodiment, since the single-plate arm member 30 is formed on the control shaft 20, two cutters are not used. In addition, the single cutter 40 can perform processing without any problem in accuracy, and the space between the arm member 30 with respect to the main bearing 29 and the eccentric cam 21 can be sufficiently widened. There is no problem of contact with the cam 21. The same applies to the polishing process for the slit 31.

  Therefore, in the case of the drive transmission mechanism 28 of this embodiment, the arm member 30 and the slit 31 can be formed easily and accurately, so that the manufacturing cost can be reduced and each part can be reduced. Since the friction and the gap are reduced, it is possible to reduce the energy loss of the actuator 24 and improve the compression ratio control accuracy.

  Further, in this embodiment, since the two-sided width 35 is formed in the intermediate portion of the connecting pin 34 and the two-sided width 35 is engaged with the slit 31 of the arm member 30, the slit 31 and the connecting pin The surface pressure of the contact portion 34 can be lowered to improve the durability of the member, and the contact between the connecting pin 34 and the slit 31 can be stabilized and the operation of the apparatus during engine operation can be stabilized.

  It should be noted that pin support holes 33 and 33 need to be formed coaxially on both support pieces 32 and 32 of the operation shaft 25, and these pin support holes 33 and 33 are formed by other components such as the control shaft 20. The processing is remarkably easy because the processing is not performed on the portion arranged in a complicated manner.

  FIG. 5 shows a second embodiment of the present invention. In this embodiment, the connecting pin 134 of the drive transmission mechanism 28 is formed in a straight shape, and the pin support holes 33, Both end portions 137 and 137 and the intermediate portion 136 of the connecting pin 134 that is rotatably fitted to the 33 are formed in the same diameter. Also in this embodiment, the dimensions of each part are set so as to satisfy the expressions (1) and (2).

  In the case of this embodiment, basically the same effect as that of the first embodiment can be obtained, but since the connecting pin 134 is formed in a straight shape, the manufacturing of the connecting pin 134 is facilitated. Manufacturing at a low cost is possible.

  FIG. 6 shows a third embodiment of the present invention. In this embodiment, a single plate-like arm member 230 is manufactured separately from the rod-like control shaft 220, and both are cut into the two. After performing polishing, heat treatment or the like, the arm member 230 is finally fastened to the set position of the control shaft 220 with the bolt 50.

  In the case of this embodiment, the same effects as those of the first embodiment can be obtained, and the following effects can be further obtained.

  That is, in this embodiment, the shape of the control shaft 220 can be simplified, and the processing of the arm member 230 (for example, the cutting processing of the slit 31) can be performed in another place where there is a space. Cost can be further reduced.

  Further, since the arm member 230 protrudes greatly in the radial direction with respect to the control shaft 220, if the arm member 230 is formed integrally with the control shaft 220 and the whole is hardened, the arm member 230 having a large radial change. Due to this portion, the control shaft 220 is bent, and there is a concern that the coaxiality of the control shaft is lowered due to the bending. However, in this embodiment, since the arm member 230 and the control shaft 220 are separate bodies, the variation in the compression ratio between the cylinders due to the bending of the control shaft 220 is eliminated by performing heat treatment on both separately. Can do. Further, heat treatment suitable for the arm member 230 and the control shaft 220 can be performed, for example, simple heat treatment can be performed on the control shaft 220 side, and the heat treatment efficiency can be improved.

The disassembled perspective view which shows the principal part of the 1st Embodiment of this invention. Sectional drawing which shows the whole variable compression apparatus of the embodiment. The fragmentary sectional top view which shows the dimensional relationship of the principal part of the embodiment. A plan view of a conventional apparatus (A), a side view (B) during the cutting process of the conventional apparatus, a plan view (C) of the first embodiment of the present invention, and a side view (D) during the cutting process of the same embodiment FIG. The fragmentary sectional top view which shows the dimensional relationship of the principal part of the 2nd Embodiment of this invention. The disassembled perspective view of the principal part which shows the 3rd Embodiment of this invention. The disassembled perspective view which shows the principal part of the conventional variable compression apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 13 ... Piston 14 ... Piston pin 15 ... Upper link 16 ... Crank shaft 17 ... Crank pin 18 ... Lower link 20, 220 ... Control shaft 21 ... Eccentric cam 22 ... Control link 24 ... Actuator 25 ... Operation shaft 28 ... Drive transmission mechanism 30 , 230 ... arm member 31 ... slit 32 ... support piece 33 ... pin support holes 34 and 134 ... connecting pin 35 ... two-sided widths 36 and 136 ... intermediate parts 37 and 137 ... end parts

Claims (7)

A plurality of links that mechanically connect the piston pin of the piston and the crank pin of the crankshaft;
A control shaft extending parallel to the crankshaft;
An eccentric cam provided eccentric to the control shaft;
A control link having one end connected to one of the plurality of links and the other end rotatably supported by the eccentric cam;
An actuator operating axis that is advanced and retracted according to operating conditions;
A drive transmission mechanism that converts the advance / retreat operation of the operation shaft into a rotation operation and transmits it to the control shaft,
In the variable compression ratio device for an internal combustion engine that arbitrarily controls the compression ratio of the cylinder by rotating the control shaft by the operation of the actuator and operating the swing fulcrum of the control link by the rotation,
The drive transmission mechanism;
A single plate-like arm member having a slit along the axial direction with one end opening radially outward, and projecting from the outer periphery of the control shaft;
A pair of parallel support pieces projecting from the tip of the operating shaft of the actuator, each of which has a pin support hole formed coaxially;
A connection pin having both ends rotatably supported in the pin support holes of the pair of support pieces,
The pair of support pieces are arranged on both sides of the arm member so as to sandwich the arm member therebetween, and the intermediate portion in the axial direction of the connecting pin supported by the support pieces is slidable in the slit of the arm member. A variable compression ratio device for an internal combustion engine, wherein the variable compression ratio device is engaged with an internal combustion engine.   The variable compression ratio device for an internal combustion engine according to claim 1, wherein a two-surface width that is slidably engaged with the slit is provided in an intermediate portion in the axial direction of the connecting pin.   3. The internal combustion engine according to claim 2, wherein an axial length of the two-side width of the connecting pin is set larger than an axial width of the arm member and smaller than a width between the support pieces. Variable compression ratio device for engines.   The variable compression ratio of the internal combustion engine according to any one of claims 1 to 3, wherein both end portions of the connection pin supported by the pin support hole are formed to have a larger diameter than an intermediate portion of the connection pin. apparatus.   The variable compression ratio device for an internal combustion engine according to any one of claims 1 to 3, wherein both end portions of the connecting pin supported by the pin support hole are formed to have the same diameter as an intermediate portion of the connecting pin. The variable compression ratio of the internal combustion engine according to any one of claims 1 to 5, wherein the arm member is provided between an eccentric cam on a control shaft and a main bearing that rotatably supports the control shaft. A device,
A variable compression ratio device for an internal combustion engine, wherein a maximum width in the control shaft axis direction of both the support pieces is set smaller than a distance between the eccentric cam and the main bearing. The variable compression ratio device for an internal combustion engine according to any one of claims 1 to 6, wherein the arm member is manufactured separately from the control shaft, and the two are integrally coupled after manufacturing.

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