JP6327018B2 - Engine valve structure - Google Patents

Description

  The present invention relates to a valve operating structure for an engine that opens and closes intake and exhaust valves.

  Conventionally, there is a structure using a camshaft and a tappet as a valve operating structure for opening and closing an intake / exhaust valve of an engine.

  In general, as the valve body of the intake / exhaust valve, a valve (hereinafter referred to as a “valve member”) in which an umbrella part which is a valve body part is provided at one end of a shaft-like valve stem is used. The valve member is urged by a valve spring in a direction in which the umbrella portion closes the valve hole. The intake / exhaust valve opens and closes when the umbrella portion contacts and separates from the valve hole.

  The tappet is disposed at the other end of the valve stem, that is, the end opposite to the side where the umbrella portion is provided (hereinafter referred to as “stem end”). The shape is a cup shape having a circular end wall portion in plan view and a cylindrical peripheral wall portion that rises from the periphery of the end wall portion toward the valve member.

  A cam lobe provided on a camshaft that rotates as the crankshaft of the engine rotates contacts the outer surface of the end wall of the tappet. When the cam surface of the cam lobe presses the other end of the valve stem against the urging force of the valve spring via the tappet, the intake valve and the exhaust valve are opened. Further, if the pressure on the cam surface is weakened, the valve member is moved by the urging force of the valve spring, and the intake valve and the exhaust valve are closed (see, for example, Patent Document 1).

JP 2010-281295 A

  In the valve operating structure of the engine of Patent Document 1, the center line in the width direction of the cam lobe, that is, the center line with respect to the axial direction of the cam shaft in the cam lobe is one side along the axial direction of the cam shaft with respect to the center line of the tappet. It is arranged eccentrically.

  For this reason, during operation, the tappet is rotated in one direction within the guide hole provided in the cylinder due to a large frictional force generated between the cam surface of the cam lobe and the end wall portion of the tappet. . Further, the rotation of the tappet also generates a rotational force in the valve stem that contacts the inner surface of the tappet, so that the valve member rotates around the axis.

However, since the axis of the valve stem is arranged in the same direction as the eccentric direction of the cam lobe with respect to the centerline of the tappet, the load acting on the tappet is on the eccentric side with respect to the centerline of the tappet. There is a tendency for the opposite side to become larger.
Such an uneven load may hinder the smooth rotation of the tappet and cause uneven wear on the cam lobe or tappet.

  Therefore, an object of the present invention is to suppress uneven wear that occurs in cam lobes and tappets.

  In order to solve the above-described problems, the present invention provides a valve member in which an umbrella portion that contacts and separates from a valve hole of a valve is provided at one end of a shaft-shaped valve stem, and the other end provided in the other end of the valve stem. A tappet consisting of an end wall part that comes into contact with and a peripheral wall part that rises from the periphery of the end wall part to the umbrella part side, and a camshaft provided with a cam lobe that is in sliding contact with the outer surface of the end wall part of the tappet, A cam lobe center line of the cam lobe with respect to the axial direction of the cam shaft is decentered along an axial direction of the cam shaft with respect to an end wall outer surface center line passing through the center of the end wall outer surface of the tappet, and the valve An engine valve-operating structure is provided in which the axis of the stem is arranged on the side opposite to the side where the cam lobe center line is decentered with respect to the end wall outer surface center line of the tappet.

  In this configuration, the camshaft is provided on each of the intake side and the exhaust side, each camshaft is provided with at least one cam lobe, and the camshaft on the intake side corresponds to the cam lobe center line of the cam lobe. With respect to the outer wall center line of the end wall portion of the tappet, the cam shaft on the exhaust side corresponds to the cam lobe center line corresponding to the cam lobe. With respect to the outer wall center line of the end wall portion of the tappet, it can be configured to be decentered in the other direction along the axial direction of the camshaft.

  The camshaft is provided on each of the intake side and the exhaust side, and each camshaft includes a plurality of cam lobes corresponding to the same cylinder, and the camshaft on the intake side includes each cam lobe of the plurality of cam lobes. A center line is arranged to be eccentric in one direction along the axial direction of the camshaft with respect to the corresponding outer wall centerline of the end wall portion of the tappet, and the camshaft on the exhaust side includes the plurality of cam lobes. Each cam lobe center line is arranged so as to be decentered in the other direction along the axial direction of the cam shaft with respect to the corresponding end wall outer surface center line of the tappet.

  In each of these configurations, the outer surface of the end wall portion of the tappet may be configured such that the center portion is formed to be more convex than the outer peripheral portion. Further, the cam surface of the cam lobe may employ a configuration in which a central portion in the axial direction of the cam shaft is formed to be more convex than both end portions. Either one of the convex shape of the outer surface of the end wall portion of the tappet and the convex shape of the cam surface of the cam lobe can be employed, but it is desirable to employ both of them in combination.

  According to the present invention, the cam lobe center line with respect to the axial direction of the cam shaft in the cam lobe is eccentric along the axial direction of the cam shaft with respect to the end wall outer surface center line passing through the center of the end wall outer surface of the tappet. Is arranged on the side opposite to the side on which the cam lobe center line is eccentric with respect to the outer wall center line of the end wall of the tappet, so that the bias of the load acting on the tappet can be suppressed. As a result, the cam lobe can be rotated smoothly and the occurrence of uneven wear on the cam lobe and tappet can be suppressed.

It is a front sectional view showing the valve operating structure of the engine of one embodiment of this invention. It is a principal part enlarged view which shows other embodiment. It is sectional drawing which shows arrangement | positioning of a cam shaft and a valve | bulb. (A) (b) is a top view which shows typically the example of arrangement | positioning of a tappet and a cam lobe, respectively.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, only members and means directly related to the present invention are shown, and other members and the like are not shown. Further, the engine may be a single cylinder or a multi-cylinder having a plurality of cylinders 1 except for the embodiment that is specifically designated.

  As shown in FIG. 1, the camshaft S includes a shaft member 10 made of a shaft member and a cam member 12 fixed to the shaft member 10.

  The cam member 12 is a metal member in which a plurality of cam lobes 11 are formed as an integral member. In this embodiment, two cam lobes 11 adjacent in the axial direction are formed as an integral member. The shaft member 10 is a metal member made of a member different from the cam member 12. An appropriate number of cam members 12 are arranged so that the number of cam lobes 11 is the same as the number of valves of the engine.

  The shaft member 10 has a uniform cross-sectional shape with a circular cross section over the entire length in the axial direction. A large-diameter portion 21 is formed at one axial end of the shaft member 10, and a sprocket, a pulley, and the like are fixed to the large-diameter portion 21.

  In this embodiment, as shown in FIG. 1, cam lobes 11 adjacent in the axial direction are connected via a cam journal 14, and a cam journal cap 20 is disposed on the outer periphery of the cam journal 14. A plurality of cam journal caps 20 are arranged along the axial direction of the shaft member 10.

  The cam shaft S is rotatably supported by the cylinder head via the cam journal cap 20 and the cam journal 14.

  The cam member 12 is integrated with the shaft member 10 by inserting a single key 13 into a key groove 13a provided on the shaft member 10 and a key groove 13b provided on the inner surface of the shaft insertion hole of the cam member 12. It has become. Due to this integration, the cam member 12 cannot rotate relative to the shaft member 10 and cannot move in the axial direction.

  An example of an engine in which the camshaft S is arranged is shown in FIG. The engine cylinder 1 is provided with a port 3 communicating with the combustion chamber 2 and a valve member 5 for opening and closing the valve hole 4 of the port 3. Port 3 has an intake port and an exhaust port. A fuel injection device (not shown) for injecting fuel into the intake port is provided in the intake port, and fuel is injected into the intake air in the intake port to form an air-fuel mixture.

  The valve structure that opens and closes the intake port and the exhaust port includes a valve member 5 and a valve spring 6 that urges the valve member 5 in the valve closing direction of the valve hole 4. The valve member 5 includes a shaft-shaped valve stem 5b and an umbrella portion 5a that contacts and separates from the valve hole 4 of the valve at one end of the valve stem 5b. The valve stem 5 b is inserted into a valve insertion hole formed in the cylinder 1, and is movable forward and backward in the axial direction with respect to the cylinder 1.

  The lower end of the valve spring 6, that is, the end close to the combustion chamber 2 is supported by the cylinder 1 via the valve spring seat, and the upper end, that is, the end on the cylinder head side, is the retainer 8 and the cotter 9. Is fixed to the valve stem 5b.

  A tappet 7 with which the end surface of the other end (stem end) of the valve stem 5b abuts is disposed on the other end side of the valve stem 5b. The tappet 7 is a cup-shaped member having a circular end wall portion 7a in plan view and a cylindrical peripheral wall portion 7b that rises from the periphery of the end wall portion 7a to the valve member 5 side.

  The tappet 7 fits into a guide hole formed in the cylinder head and slides on the inner surface of the guide hole. The stem end 5c comes into contact with a convex portion 7c provided on the inner surface of the end wall portion 7a of the tappet 7, and the cam lobe 11 rotating with the rotation of the crankshaft of the engine comes into contact with the outer surface 7d of the end wall portion 7a. .

  When the cam lobe 11 rotates, the outer cam surface 11a of the cam lobe 11 comes into sliding contact with the outer surface 7d of the corresponding end wall 7a of the tappet 7. When the valve stem 5 b is pressed against the urging force of the valve spring 6 through the tappet 7 by the action of the cam, the valve member 5 is lowered to open the valve hole 4. When the pressing force due to the action of the cam is weakened, the valve member 5 is raised by the elastic force of the valve spring 6 and closes the valve hole 4. Thus, the valve member 5 opens and closes the port 3 at a predetermined timing by the rotation of the cam lobe 11.

  Transmission of power to the camshaft S provided with the cam lobe 11 is performed between a sprocket or pulley provided on the large-diameter portion 21 of the camshaft S and a sprocket or pulley provided on the crankshaft side with a timing chain or belt. It is done by connecting with the same.

  On the outer surface 7d of the end wall portion 7a of the tappet 7, a crowning (convex surface) is formed. That is, the outer surface 7d of the end wall portion 7a of the tappet 7 is formed such that the center portion is more convex than the outer peripheral portion. As shown in FIG. 1, this crowning has a top on the center line of the tappet 7 (a line extending through the center of the end wall 7a in plan view and extending in the axial direction of the valve stem 5b), and ends from the top. It gradually inclines toward the umbrella part 5a over the entire circumference toward the ridgeline between the wall part 7a and the peripheral wall part 7b. The inclined surface has an arc shape from the top to the ridgeline in a cross section in a front view. An end wall outer surface center line which is a center line of the crowning provided on the outer surface 7d of the end wall portion 7a of the tappet 7 (a line extending through the crown of the outer surface 7d of the end wall portion 7a and extending in the axial direction of the valve stem 5b) In the following description, the crowning center line b) coincides with the center line of the tappet 7.

  A crowning is also formed on the cam surface 11 a of the cam lobe 11. That is, the cam surface 11a of the cam lobe 11 is formed such that the central portion in the axial direction of the cam shaft S is more convex than both end portions. This crowning has a top portion on the center line of the cam surface 11a with respect to the axial direction of the camshaft S, and gradually extends over the entire circumference of the camshaft S from the top portion toward the axial end portion of the cam surface 11a. Inclined toward the axis. The inclined surface has a circular arc shape from the top to the axial end of the cam surface 11a in the cross section in front view, and the cross section of the cam lobe 11 has a barrel shape as a whole. The cam surface center line c (the line extending through the crown of the cam lobe 11 and extending in the axial direction of the valve stem 5b, which is the center line of the crown provided on the cam surface 11a of the cam lobe 11, hereinafter referred to as the cam side crowning center line c) Is coincident with a center line of the cam surface 11a with respect to the axial direction of the cam shaft S (hereinafter referred to as a cam lobe center line).

  Here, the cam-side crowning center lines c and c in the two cam lobes 11 provided in one cam member 12 are arranged between the crowning center lines b and b of the corresponding tappets 7.

  Thus, by offsetting the crowning center line b on the tappet 7 side and the cam side crowning center line c on the cam lobe 11 side, the two cam lobes 11 are sandwiched between the tops of the crowns of the tappets 7 on both sides. Will be arranged. For this reason, the cam lobe 11 cannot get over the crown of the tappet 7, and the cam member 12 is restricted from moving in the thrust direction. That is, the cam lobe 11 can be prevented from moving in the axial direction of the camshaft S.

  Further, the axis a of the valve stem 5b is arranged so as to be eccentric with respect to the crowning center line b of the corresponding tappet 7 on the side opposite to the side where the cam lobe 11 slidably contacting the tappet 7 is eccentric.

  In FIG. 1, the axis a of the left valve stem 5 b in FIG. 1 is disposed on the opposite side of the cam lobe 11 on the cam side crowning center line c with respect to the crowning center line b of the left tappet 7. Has been. In addition, the axis a of the right valve stem 5b in the drawing is disposed on the opposite side of the side where the cam side crowning center line c of the cam lobe 11 is located with respect to the crowning center line b of the corresponding right tappet 7. Yes.

  Thus, the axis a of the valve stem 5b is offset with respect to the crowning center line b of the tappet 7, that is, with respect to the center line of the tappet 7, in the direction opposite to the cam lobe 11, so that the crowning center line b The balance of the load acting on the tappet 7 is improved. This is because the point of action of the force from the cam lobe 11 to the tappet 7 and the point of action of the force from the tappet 7 to the valve stem 5b are located on both sides of the crowning center line b.

By improving the load balance, the rotation of the tappet 7 can be improved, and the wear of the tappet 7 can be reduced.
As the cam lobe 11 is offset with respect to the tappet 7, the valve stem 5 b is offset to the opposite side of the cam lobe 11 to avoid excessive loads from being concentrated in one place. It works effectively for smoothness.

  As a modification of the above embodiment, for example, the cam-side crowning center lines c and c in the two cam lobes 11 provided in one cam member 12 are respectively between the crowning center lines b and b of the corresponding tappets 7. The thing arrange | positioned outside is also considered. The crowning center lines b and b of the tappet 7 are sandwiched between the cam side crowning center lines c and c of the two cam lobes 11.

  In this way, by offsetting the crowning center line b on the tappet 7 side and the cam side crowning center line c on the cam lobe 11 side, the two cam lobes 11 are both outside the top portions of the crowning of the two tappets 7. It becomes the arrangement to. For this reason, the cam lobe 11 cannot get over the crown of the tappet 7, and the cam member 12 is restricted from moving in the thrust direction. That is, the cam lobe 11 can be prevented from moving in the axial direction of the camshaft S.

  In these embodiments, the cam-side crowning center line c of the cam lobe 11 is made to coincide with the cam lobe center line that is the center line of the cam surface 11a with respect to the axial direction of the cam shaft S. A mode in which the center line c does not coincide with the cam lobe center line of the cam surface 11a is also conceivable.

  Furthermore, it is possible to adopt a mode in which no crowning is provided on the cam surface 11a of the cam lobe 11.

  In this case, since the outer surface 7d of the end wall portion 7a of the tappet 7 is formed with a crowning, it is the center line of the cam surfaces 11a of the two cam lobes 11 provided in the cam member 12 with respect to the axial direction of the camshaft S. Each cam lobe center line may be arranged between the crowning center lines b and b passing through the crown of each corresponding tappet 7. The cam lobe center lines of the two cam lobes 11 are both disposed between the crowning tops of the tappets 7 on both sides.

  Alternatively, when the cam lobe center lines with respect to the axial direction of the cam shaft S on the cam surfaces 11a of the two cam lobes 11 included in the cam member 12 are disposed outside the space between the crowning center lines b and b of the corresponding tappets 7. Good. In this arrangement, the crowning center lines b and b of the tappet 7 are sandwiched between the cam lobe center lines of the two cam lobes 11.

  Thus, even in a configuration in which no crowning is provided on the cam surface 11a, the cam member 12 can be restricted from moving in the thrust direction.

  When assembling the split camshaft S of this embodiment, first, the shaft member 10 made of a shaft member is inserted into the axial hole of the cam member 12 having the two cam lobes 11. The shaft member 10 may be inserted into the axial hole of the cam member 12 by shrink fitting or the like. When the cam member 12 is arranged at a predetermined axial position and an orientation around the axis, the cam member 12 is fixed to the shaft member 10 by press-fitting the key 13 into the key grooves 13a and 13b. Thereafter, the next cam member 12 is attached. When a spacer, an integrated cam journal, or the like is disposed between the cam members 12, 12 adjacent in the axial direction, the next cam member 12 is attached after the spacer, the integrated cam journal, or the like is disposed.

  When the cam journal cap 20 is arranged on the outer periphery of the cam journal between the cam lobes 11 and 11 of the cam member 12, the cam lobe 11 has a relatively large diameter, and therefore a split cam journal cap is used. After the cam member 12 is fixed to the shaft member 10, the cam journal cap 20 is placed on the cam journal 14 between the cam lobes 11 and 11, and the cam shaft S is fixed to a predetermined location in the cylinder head using a bolt or the like. To do.

  Another embodiment is shown in FIG. In the above embodiment, the two cam lobes 11 adjacent in the axial direction are formed by the integral cam member 12 and are combined by the shaft member 10 which is a member different from the cam member 12, but in this embodiment, The camshaft S is configured by using the cam lobe 11 and the shaft member 10 as an integral member without using the cam member 12.

  Here, the cam side crowning center lines c and c passing through the tops of the crownings of the two cam lobes 11 adjacent in the axial direction are respectively in relation to the crowning center lines b and b passing through the tops of the corresponding crownets 7. The camshaft S is arranged eccentrically on the same side (left side in the figure) along the axial direction of the camshaft S.

  Further, the axis a of the valve stem 5b is eccentric with respect to the crowning center lines b and b of the corresponding tappets 7 on the side opposite to the side where the cam lobe 11 slidably contacting the tappet 7 is eccentric (right side in the figure). Has been placed.

  That is, in FIG. 2, the axis a of the left valve stem 5b in FIG. 2 is opposite to the side of the cam lobe 11 where the cam side crowning center line c is located with respect to the crowning center line b of the corresponding left tappet 7. Is arranged. In addition, the axis a of the right valve stem 5b in the drawing is also arranged on the opposite side of the cam lobe 11 where the cam side crowning center line c is located with respect to the crowning center line b of the right tappet 7. Yes.

  Also in this embodiment, the axis a of the valve stem 5b is offset in the direction opposite to the cam lobe 11 with respect to the crowning center line b of the tappet 7, that is, with respect to the center line of the tappet 7. The balance of the load acting on 7 is improved. Thereby, the rotational property of the tappet 7 can be improved and it can contribute to the wear reduction of the tappet 7.

  In each of the above-described embodiments, the valve member 5 and the tappet 7 that are adjacent along the axial direction of the camshaft S are the intake valves that are juxtaposed in the same cylinder of the engine or the exhaust valves that are juxtaposed in the same cylinder of the engine. It is also possible to use a pair of intake valves of adjacent cylinders of the engine or exhaust valves of adjacent cylinders of the engine.

  FIG. 4A shows an intake valve in which a tappet 7 that is an object to decenter the cam lobe 11 and the valve stem 5b, that is, the tappet 7 adjacent in the axial direction of the camshaft S corresponds to the same cylinder of the engine. Or the case where it is a thing of an exhaust valve is shown in the schematic diagram.

  This engine is a double overhead cam type in which camshafts S are provided on the intake side and the exhaust side, respectively, and is a four-valve type in which one cylinder has two intake valves and two exhaust valves. Each of the intake-side and exhaust-side camshafts S includes a plurality of (two in the embodiment) cam lobes 11 corresponding to the number of valves.

  In each valve on the intake side on the left side in the figure, the cam lobe center lines c and c of the plurality of adjacent cam lobes 11 correspond to the corresponding tappets 7; (A) and (B) end wall outer surface center lines b and b. These are arranged eccentrically on the same side (upward in the figure) along the axial direction of the camshaft S.

  Further, the axial centers a and a of the plurality of adjacent valve stems 5b are respectively in the axial direction of the camshaft S with respect to the end wall portion outer surface center lines b and b of the corresponding tappets 7; Along with this, the cam lobe 11 is arranged eccentrically on the opposite side (downward in the figure) to the side where it is eccentric.

  In each valve on the exhaust side on the right side in the figure, the cam lobe center lines c and c of the plurality of adjacent cam lobes 11 correspond to the corresponding tappets 7; (C) and (D) end wall outer surface center lines b and b. These are arranged eccentrically on the same side (downward in the drawing) along the axial direction of the camshaft S. That is, in the valve on the intake side, the cam lobe 11 is eccentric to the side opposite to the eccentric side.

  Further, the axial centers a and a of the plurality of adjacent valve stems 5b are respectively in the axial direction of the camshaft S with respect to the outer wall center lines b and b of the end wall portions of the corresponding tappets 7; (C) and (D). Along with this, the cam lobe 11 is arranged eccentrically on the side opposite to the side where the cam lobe 11 is eccentric (upward in the figure). That is, in the valve on the intake side, the valve stem 5b is eccentric to the side opposite to the eccentric side.

  Thus, for the same cylinder, the side on which the cam lobe 11 is eccentric with respect to the tappet 7 on the intake side and the exhaust side is set in the opposite direction, and the valve stem 5b with respect to the tappet 7 on the intake side and the exhaust side. Since the eccentric side is in the reverse direction, the load balance in one cylinder is improved, and the suppression of uneven wear of the member can be made more remarkable.

Incidentally, the eccentricity amount _W A of the cam lobe centerline c against the end wall outer surface center line _{b, W B, W C,} W D is preferably set all equal. Further, the eccentricity of the axis a of the valve stem 5b against the end wall outer surface center line _{b W A ', W B'} , W C ', W D' , it is desirable to set all equal. Further, the eccentricity W _A cam lobe centerline c for the same tappet 7, the axis a eccentricity W _A of the valve stem 5b _'is desirably set equal to each other. Eccentricity _{W B} and the eccentric weight _{W B} ', eccentricity _{W C} and the eccentric weight _{W C',} is the same relationship between the eccentricity amount _{W D} and the eccentric weight _{W D} '. In each figure, for the sake of easy understanding, each eccentric amount is shown to be large with respect to the outer diameter of the tappet 7, but the actual eccentric amount is a small dimension that is less than 1 mm.

  FIG. 4B shows an intake valve in which a tappet 7 to be decentered of the cam lobe 11 or the valve stem 5b, that is, the tappet 7 adjacent along the axial direction of the camshaft S corresponds to an adjacent cylinder of the engine. Or the case where it is with respect to an exhaust valve is shown in the schematic diagram.

  This engine is a double overhead cam type in which camshafts S are provided on the intake side and the exhaust side, respectively, and a two-valve type in which one cylinder has one intake valve and one exhaust valve. Each of the intake-side and exhaust-side camshafts S includes one cam lobe 11 corresponding to the same cylinder.

  In each valve on the intake side on the left side in the figure, the cam lobe center lines c and c of the plurality of adjacent cam lobes 11 correspond to the corresponding tappets 7; (A) and (B) end wall outer surface center lines b and b. These are arranged eccentrically on the same side (upward in the figure) along the axial direction of the camshaft S.

  Further, the axial centers a and a of the plurality of adjacent valve stems 5b are respectively in the axial direction of the camshaft S with respect to the end wall portion outer surface center lines b and b of the corresponding tappets 7; (A) and (B). Along with this, the cam lobe 11 is arranged eccentrically on the opposite side (downward in the figure) to the side where it is eccentric.

  In each valve on the exhaust side on the right side in the figure, the cam lobe center lines c and c of the plurality of adjacent cam lobes 11 correspond to the corresponding tappets 7; (C) and (D) end wall outer surface center lines b and b. These are arranged eccentrically on the same side (downward in the drawing) along the axial direction of the camshaft S. That is, in the valve on the intake side, the cam lobe 11 is eccentric to the side opposite to the eccentric side.

  Further, the axial centers a and a of the plurality of adjacent valve stems 5b are respectively in the axial direction of the camshaft S with respect to the outer wall center lines b and b of the end wall portions of the corresponding tappets 7; (C) and (D). Along with this, the cam lobe 11 is arranged eccentrically on the side opposite to the side where the cam lobe 11 is eccentric (upward in the figure). That is, in the valve on the intake side, the valve stem 5b is eccentric to the side opposite to the eccentric side.

  Thus, with respect to the cylinders adjacent to each other along the axial direction of the camshaft S, the side on which the cam lobe 11 is eccentric with respect to the tappet 7 on the intake side and the exhaust side is the reverse direction, and the intake side and the exhaust side Thus, since the side where the valve stem 5b is eccentric with respect to the tappet 7 is set in the reverse direction, the load balance between the adjacent cylinders is improved, and the suppression of uneven wear of the members can be made more remarkable.

The eccentric amount W _A , W _B , W _C , W _D of the cam lobe center line c with respect to the end wall outer surface center line b, and the eccentric amount W of the shaft center a of the valve stem 5b with respect to the end wall outer surface center line b. The setting of _A ′, W _B ′, W _C ′, and W _D ′ is the same as described above.

  In the embodiment of FIG. 4 (b), in an engine having a plurality of cylinders, two cylinders adopting an eccentric structure between the valve stem 5b, the tappet 7 and the cam lobe 11 are shown. In this engine, the eccentric structure in one cylinder shown in FIG. 4B can also be adopted.

  In this invention, since the axis a of the valve stem 5b is offset in the direction opposite to the cam lobe 11 with respect to the center line of the tappet 7, the balance of the load acting on the tappet 7 is improved. Thereby, the rotational property of the tappet 7 can be improved, and it can contribute to reduction of tappet wear. As the cam lobe 11 is offset with respect to the tappet 7, the valve stem 5 b is offset to the opposite side of the cam lobe 11 to avoid excessive loads from being concentrated in one place. It works effectively for smoothness.

1 Cylinder 2 Combustion chamber 3 Port 4 Valve hole 5 Valve member (valve)
5a Umbrella 5b Valve stem 5c Stem end 7 Tappet 7a End wall 7b End wall 7d Outer surface 10 Shaft member 11 Cam lobe 11a Cam surface 12 Cam member 13 Key 14 Cam journal 20 Cam journal cap S Camshaft

Claims (5)

A valve member provided with an umbrella part that contacts and separates from the valve hole of the valve at one end of the shaft-shaped valve stem;
A tappet comprising an end wall portion provided at the other end of the valve stem, and the peripheral wall portion rising from the peripheral edge of the end wall portion toward the umbrella portion;
A camshaft provided with a cam lobe in sliding contact with the outer surface of the end wall of the tappet,
The cam lobe center line of the cam lobe with respect to the axial direction of the cam shaft is decentered along the axial direction of the cam shaft with respect to the end wall outer surface center line passing through the center of the end wall outer surface of the tappet.
A valve operating structure for an engine in which an axis of the valve stem is disposed on a side opposite to a side on which the cam lobe center line is eccentric with respect to the end wall outer surface center line of the tappet. The camshaft is provided on each of the intake side and the exhaust side,
Each camshaft comprises at least one cam lobe;
The camshaft on the intake side is arranged such that the cam lobe center line of the cam lobe is decentered in one direction along the axial direction of the cam shaft with respect to the corresponding end wall outer surface center line of the tappet,
The camshaft on the exhaust side is arranged such that the cam lobe center line of the cam lobe is decentered in the other direction along the axial direction of the cam shaft with respect to the outer wall center line of the corresponding end wall of the tappet. The valve operating structure for an engine according to claim 1. The camshaft is provided on each of the intake side and the exhaust side,
Each camshaft includes a plurality of cam lobes corresponding to the same cylinder,
The intake side camshaft is configured such that each cam lobe center line of the plurality of cam lobes is decentered in one direction along the axial direction of the camshaft with respect to the corresponding end wall outer surface center line of the tappet. Arranged,
The camshaft on the exhaust side is configured such that each cam lobe center line of the plurality of cam lobes is decentered in the other direction along the axial direction of the cam shaft with respect to the corresponding end wall outer surface center line of the tappet. The valve operating structure for an engine according to claim 1, wherein the valve operating structure is disposed.   The valve operating structure for an engine according to any one of claims 1 to 3, wherein a central portion of the outer surface of the end wall portion of the tappet is formed to be more convex than an outer peripheral portion.   5. The valve operating structure for an engine according to claim 1, wherein the cam surface of the cam lobe is formed such that a central portion in the axial direction of the cam shaft is more convex than both end portions.

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