JP2017190726A - Camshaft for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce the weight of a camshaft while securing torsional rigidity of a shaft during rotation of the camshaft.SOLUTION: A camshaft for an engine includes a shaft and a cam provided in an outer periphery of the shaft, and is rotated in a fixed direction by receiving torque of a crankshaft. The shaft has a thinned portion, and the thinned portion is formed so that torsional rigidity of the shaft when the camshaft is rotated in the fixed direction by receiving the torque of the crankshaft is larger than the torsional rigidity of the shaft when assuming that the camshaft is rotated in a direction opposite from the fixed direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an engine camshaft.

  Conventionally, camshafts that drive engine intake valves and exhaust valves have solid camshaft shafts (solid type), and camshaft shafts are hollow throughout their length. (Patent Document 1) discloses an example of a hollow type camshaft.

JP 2014-18833 A

  According to the camshaft described in Patent Document 1, although a certain amount of weight can be reduced as compared with a solid camshaft, the torsional rigidity is not considered. That is, the engine camshaft rotates in a certain direction, and stress always acts in the rotation direction. Therefore, when reducing the weight, it is desirable to ensure the torsional rigidity in the rotation direction as large as possible. However, the hollow portion formed in the shaft portion of the camshaft described in Patent Document 1 has the same shape in the entire circumferential direction of the shaft portion. For this reason, in the camshaft described in Patent Document 1, it is difficult to effectively reduce the weight while ensuring the torsional rigidity in the rotation direction.

  The present invention has been made in view of the above circumstances, and provides an engine camshaft that can effectively reduce the weight of a camshaft while ensuring torsional rigidity of a shaft portion during rotation of the camshaft. The purpose is to provide.

  In order to solve the above-described problems, the present invention is an engine camshaft that includes a shaft portion and a cam portion provided on an outer periphery of the shaft portion, and that rotates in a predetermined direction by receiving the rotational force of the crankshaft. The shaft portion has a thinning portion, and the thinning portion has a torsional rigidity of the shaft portion when the camshaft receives the rotational force of the crankshaft and rotates in the fixed direction. Provided is a camshaft for an engine, wherein the camshaft is formed to be larger than a torsional rigidity of the shaft when it is assumed that the camshaft rotates in a direction opposite to the constant direction. .

  Here, the “thickening part” in the present invention is a part of the shaft part having the same outer diameter so that a part of the cross-sectional area in the length direction is smaller than a cross-sectional area of a part other than the part. Hole portions (recesses and through-holes) formed on the outer peripheral surface or inner peripheral surface (inner peripheral surface in the case where a hollow portion extending in the length direction of the shaft portion is formed at the radial center of the shaft portion) Including) or notch.

  According to the present invention, the camshaft can be effectively reduced in weight while ensuring the torsional rigidity of the shaft portion when the camshaft rotates.

  More specifically, in the present invention, since the shaft portion has the thinning portion, the camshaft can be reduced in weight by a weight corresponding to the volume of the thinning portion as compared with the case where the thinning portion is not provided. it can.

  Moreover, the torsional rigidity of the shaft portion can be ensured for the following reasons. That is, the camshaft according to the present invention rotates in a certain direction in response to the rotational force of the crankshaft, and the thinning portion is when the camshaft rotates in the certain direction (forward rotation direction). The torsional rigidity of the shaft part is formed to be larger than the torsional rigidity of the shaft part when it is assumed that the camshaft is rotating in the direction opposite to the above-mentioned constant direction (reverse direction). The shaft portion is configured such that the torsional rigidity in the forward rotation direction is relatively larger than the torsional rigidity in the reverse rotation direction. For this reason, according to the camshaft according to the present invention, like the camshaft described in Patent Document 1, the hollow portion having the same shape is formed in the central portion in the radial direction of the shaft portion over the entire circumferential direction. Compared to the case where the torsional rigidity in the forward rotation direction of the shaft part and the torsional rigidity in the reverse direction of the shaft part are the same, the torsional rigidity in the forward rotation direction of the shaft part can be secured larger. Thereby, according to the camshaft which concerns on this invention, compared with the camshaft by which the axial part was simply formed in the cylindrical shape like patent document 1, it became possible to carry out a larger thickness, As a result, a axial part The camshaft can be greatly reduced in weight while ensuring the torsional rigidity in the forward rotation direction.

  In the present invention, at one end of the shaft portion, a driving mechanism connecting portion to which a rotation driving mechanism for rotating the shaft portion in the predetermined direction is connected is provided, A hole that opens in the outer peripheral surface of the shaft and extends along the axial direction of the shaft, the hole being gradually displaced in the rotation delay direction as the drive mechanism is connected to the shaft. It is preferable to be inclined with respect to the center line.

  According to this configuration, the thinned portion is a hole that opens in the outer peripheral surface of the shaft portion and extends along the axial direction of the shaft portion, and thus the thinned portion can be easily formed.

  Moreover, when the hole is inclined with respect to the center line of the shaft part so as to shift in the rotation delay direction as approaching the drive mechanism connecting part as described above, the hole part is relative to the center line of the shaft part. The torsional rigidity of the shaft during rotation in the predetermined direction is greater than when tilted to the opposite side of the tilt direction and when the hole extends parallel to the axial direction of the shaft. More specifically, when the hole portion is inclined with respect to the center line of the shaft portion so as to be shifted in the rotation delay direction as it approaches the drive mechanism connecting portion, the shaft portion is more than the other two cases described above. Since the portion other than the hole portion strongly resists torsion of the shaft portion during rotation in the fixed direction, a large torsional rigidity of the shaft portion can be ensured, and thereby, the fixed direction (positive direction) of the shaft portion can be ensured. The camshaft can be greatly reduced in weight while ensuring the torsional rigidity in the rolling direction.

  In the present invention, a drive mechanism connecting portion to which a rotation driving mechanism for rotating the shaft portion in the predetermined direction is connected to an end portion on one side of the shaft portion, and the shaft portion has a diameter of A cylindrical portion having a hollow portion extending in a length direction of the shaft portion at a central portion in the direction, and the thinning portion is formed so as to be recessed radially outward from an inner peripheral surface of the shaft portion. It is a hole extending along the axial direction of the part, and the hole is inclined with respect to the center line of the shaft so as to gradually shift in the rotation delay direction as it approaches the drive mechanism connecting part. preferable.

  According to this configuration, since the shaft portion has a hollow portion extending in the length direction of the shaft portion at the radial center portion, the volume of the hollow portion is smaller than when the hollow portion is not provided. Thus, the camshaft can be further reduced in weight by the weight corresponding to.

  Moreover, when the hole is inclined with respect to the center line of the shaft part so as to shift in the rotation delay direction as approaching the drive mechanism connecting part as described above, the hole part is relative to the center line of the shaft part. The torsional rigidity of the shaft during rotation in the predetermined direction is greater than when tilted to the opposite side of the tilt direction and when the hole extends parallel to the axial direction of the shaft. More specifically, when the hole portion is inclined with respect to the center line of the shaft portion so as to be shifted in the rotation delay direction as approaching the drive mechanism connecting portion, the shaft portion is compared with the other two cases described above. Since the portion other than the hole portion in the shaft more strongly resists torsion during the rotation in the fixed direction, a large torsional rigidity of the shaft portion can be ensured. The camshaft can be greatly reduced in weight while ensuring torsional rigidity in the direction).

  As described above, according to the present invention, it is possible to effectively reduce the weight of the camshaft while ensuring the torsional rigidity of the shaft portion during rotation of the camshaft.

It is a top view which shows a cylinder head provided with the camshaft (exhaust camshaft and intake camshaft) for engines which concerns on embodiment of this invention. It is a perspective view which shows the exhaust camshaft shown by FIG. It is a top view which shows the exhaust camshaft shown by FIG. It is a side view which shows the exhaust camshaft shown by FIG. FIG. 4 is a cross-sectional view of the exhaust camshaft shown in FIG. 3 taken along line AA. FIG. 3 is a cross-sectional view of the intake camshaft shown in FIG. 1 taken along the line BB. (A) is CC sectional view taken on the line of the exhaust camshaft shown by FIG. 3, (b) is DD sectional view taken on the line of the exhaust camshaft shown in FIG. (A) is sectional drawing which shows the 1st modification of the hole part of an exhaust camshaft, (b) is sectional drawing which shows the 2nd modification of the hole part of an exhaust camshaft. FIG. 6 is a cross-sectional view showing an intake camshaft when a hollow portion is formed in the radial center portion of the shaft portion of the intake camshaft and all the hole portions opened to the outer peripheral surface of the shaft portion communicate with the hollow portion. is there. (A) is the EE sectional view taken on the line of the intake camshaft shown by FIG. 9, (b) is the FF sectional view taken on the line of the intake camshaft shown in FIG. A hollow portion is formed at the radial center portion of the shaft portion of the intake camshaft, and among the hole portions opened on the outer peripheral surface of the shaft portion, between the end portions on both sides of the shaft portion and the cam portion closest to the end portion. It is sectional drawing which shows an intake camshaft in case the hole formed in this area and the said hollow part are connecting. It is a GG sectional view taken on the line of the intake camshaft shown in FIG. FIG. 4 is a cross-sectional view showing an intake camshaft in which a shaft portion of the intake camshaft is formed in a hollow cylindrical shape and a hole portion that is recessed radially outward from the inner peripheral surface of the shaft portion is formed. (A) is the HH sectional view taken on the intake camshaft shown in Drawing 13, and (b) is the JJ sectional view taken on the intake camshaft shown in Drawing 13.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Engine structure with camshaft>
An engine including a camshaft according to an embodiment of the present invention is an in-line four-cylinder four-cycle diesel engine, and is assembled on a cylinder block (not shown) and the cylinder block as shown in FIG. And a cylinder head 72. In the engine shown in FIG. 1, although not shown, four cylinders of a first cylinder, a second cylinder, a third cylinder, and a fourth cylinder are arranged in order from the left side.

  The cylinder head 72 has, for each cylinder, two exhaust ports and two intake ports communicating with the combustion chamber, an exhaust valve for shutting off each exhaust port from the combustion chamber, and shutting each intake port from the combustion chamber. An exhaust valve drive mechanism 78 for driving each exhaust valve to open and close each exhaust port at a predetermined timing, and each intake valve for driving each intake valve. An intake valve drive mechanism 73 that opens and closes the intake port at a predetermined timing, four bearing portions 24 to 27 that rotatably support an exhaust camshaft 2 described later, and 4 that rotatably supports an intake camshaft 3 described later. And two bearing portions 74 to 77.

  The exhaust valve drive mechanism 78 and the intake valve drive mechanism 73 include an exhaust camshaft 2 and an intake camshaft 3, respectively. The exhaust camshaft 2 and the intake camshaft 3 are well-known configured from a chain, a sprocket, and the like. It is connected to the crankshaft via a power transmission mechanism. Further, the exhaust valve drive mechanism 78 and the intake valve drive mechanism 73 each include a return spring (not shown) that biases the exhaust valve in the closing direction and a return spring (not shown) that biases the intake valve in the closing direction. ing. The exhaust camshaft 2 and the intake camshaft 3 respectively open the exhaust valve and the intake valve against the urging force of the return spring by the driving force of the crankshaft. The exhaust camshaft 2 and the intake camshaft 3 correspond to the “engine camshaft” of the present invention.

<Exhaust camshaft structure>
As shown in FIGS. 1 to 3, the exhaust camshaft 2 includes a columnar shaft portion 5 extending in the cylinder row direction, and eight cam portions integrally provided on the outer periphery of the shaft portion 5 (see FIG. 1). In order from the left side, the first cam portion 6, the second cam portion 7, the third cam portion 8, the fourth cam portion 9, the fifth cam portion 10, the sixth cam portion 11, the seventh cam portion 12, and the eighth cam. Part 13), journal parts 20 to 23 (see FIG. 2) which are integrally provided on the outer periphery of the shaft part 5 and are rotatably supported by the bearing parts 24 to 27, respectively, and a sprocket around which a timing chain is wound (Not shown) is attached, and the sprocket mounting portion 4 provided integrally at one end portion of the shaft portion 5 is integrally provided at the other end portion of the shaft portion 5, and is a drive shaft of the fuel pump. And an Oldham coupling part 15 to which (not shown) is connected. . The exhaust camshaft 2 rotates in a certain direction in response to the rotational force of the crankshaft. In the example shown in FIG. 1, the exhaust camshaft 2 rotates clockwise (clockwise) when viewed from the left side. Rotate. The sprocket corresponds to the “rotation drive mechanism” of the present invention, and the sprocket mounting portion 4 corresponds to the “drive mechanism connecting portion” of the present invention.

  In the exhaust camshaft 2, the first cam portion 6 and the second cam portion 7 are eccentric cams provided corresponding to the first cylinders, and these are adjacent to each other via the journal portion 20. (See FIGS. 2 to 4). The first cam portion 6, the second cam portion 7, and the journal portion 20 are located above the first cylinder and on the exhaust side. Similarly, the third cam portion 8 and the fourth cam portion 9 are eccentric cams provided corresponding to the second cylinder, respectively, and are adjacent to each other via the journal portion 21. The third cam portion 8, the fourth cam portion 9, and the journal portion 21 are located above the second cylinder and on the exhaust side. Each of the fifth cam portion 10 and the sixth cam portion 11 is an eccentric cam provided corresponding to the third cylinder, and these are adjacent to each other via the journal portion 22. The fifth cam portion 10, the sixth cam portion 11, and the journal portion 22 are located above the third cylinder and on the exhaust side. Each of the seventh cam portion 12 and the eighth cam portion 13 is an eccentric cam provided corresponding to the fourth cylinder, and these are adjacent to each other via the journal portion 23. The seventh cam portion 12, the eighth cam portion 13, and the journal portion 23 are located above the fourth cylinder and on the exhaust side. Each of the cam portions 6 to 13 includes one nose portion 6a to 13a (see FIG. 2) that protrudes radially outward from the base circle.

  In the engine according to the present embodiment, the explosion order of each cylinder is set as follows: first cylinder → third cylinder → fourth cylinder → second cylinder, and accordingly, the cam portions 6 to 13 of the exhaust camshaft 2. Are provided with a phase difference from each other so that the exhaust valves are opened in the order of explosion described above every 90 ° rotation of the exhaust camshaft 2 (see FIG. 2).

  The shaft portion 5 of the exhaust camshaft 2 has a hole portion 16 in a section between the sprocket mounting portion 4 and the first cam portion 6, and a section between the second cam portion 7 and the third cam portion 8. A hole 17, a rotation angle adjusting part 18 in a section between the fourth cam part 9 and the fifth cam part 10, and a hole in a section between the sixth cam part 11 and the seventh cam part 12. It has a part 19 and a camshaft identification ring 14.

  As shown in FIG. 5, the hole portion 16 has a first hole portion 16 a that opens at a predetermined position on one radial side of the shaft portion 5, and a first hole portion that opens at a predetermined position on the other radial side of the shaft portion 5. 2 holes 16b. Each of the first hole portion 16a and the second hole portion 16b extends along the length direction (axial direction) of the shaft portion 5, and gradually narrows from the radially outer side of the shaft portion 5 toward the center. (See FIG. 7A).

  More specifically, each of the hole 16a and the hole 16b opens on the outer peripheral surface of the shaft portion 5 in a shape in which a semicircle is combined with both ends of a rectangle extending along the length direction of the shaft portion 5. An opening 16e (see FIG. 7 (a)), a substantially flat bottom 16d having a shape substantially the same as the opening 16e and smaller than the opening area of the opening 16e, the opening 16e and the bottom 16d And a peripheral wall portion 16c that connects the two. The bottom portion 16d has substantially the same depth over the entire length direction, and a boundary portion between the peripheral wall portion 16c and the bottom portion 16d is formed in a curved surface shape.

  Further, the first hole portion 16a and the second hole portion 16b respectively twist the shaft portion 5 when the exhaust camshaft 2 receives the rotational force of the crankshaft and rotates in the predetermined direction (forward rotation direction). The rigidity is formed so as to be larger than the torsional rigidity of the shaft portion 5 when it is assumed that the exhaust camshaft 2 rotates in a direction (reverse direction) opposite to the predetermined direction.

  Specifically, as shown in FIGS. 1, 2, and 4, the first hole portion 16 a and the second hole portion 16 b each have a shaft portion that gradually shifts in the rotation delay direction as the sprocket mounting portion 4 is approached. It inclines with respect to 5 centerline CL1. The inclination angle of the first hole portion 16a and the second hole portion 16b with respect to the center line CL1, that is, the angle formed by the length direction of the first hole portion 16a with respect to the center line CL1, and the second hole portion 16b The angle formed by the length direction with respect to the center line CL1 can be arbitrarily set in a range larger than 0 ° and smaller than 90 °, and is not particularly limited.

  The first hole portion 16a is formed in the same shape and the same size as the second hole portion 16b at a position opposite to the second hole portion 16b with respect to the center line CL1 of the shaft portion 5. The inclination angle with respect to the center line CL1 is set to be the same as the inclination angle of the second hole portion 16b. Further, as shown in FIG. 7A, the first hole portion 16a is formed on the apex side of the nose portion 6a of the first cam portion 6, and specifically, the length direction of the first hole portion 16a. The central portion is formed at a position where the apex of the nose portion 6a of the first cam portion 6 and the rotation angle (phase) are substantially the same. The second hole portion 16b is formed on the opposite side of the first cam portion 6 from the nose portion 6a. Specifically, the central portion in the length direction of the second hole portion 16b is the nose portion of the first cam portion 6. The apex of 6a is formed at a position where the rotation angle (phase) differs by approximately 180 °. The first hole 16a and the second hole 16b correspond to the “thinning portion” of the present invention.

  As shown in FIG. 5, the hole 17 has a first hole 17 a that opens at a predetermined position on one side in the radial direction of the shaft 5 and a first hole that opens at a predetermined position on the other side in the radial direction of the shaft 5. 2 holes 17b. Each of the first hole portion 17a and the second hole portion 17b extends along the length direction of the shaft portion 5, and is formed so as to gradually narrow from the radially outer side of the shaft portion 5 toward the center. (See FIG. 7B).

  More specifically, each of the first hole portion 17a and the second hole portion 17b has a semicircle combined with both ends of a rectangle extending along the length direction of the shaft portion 5 on the outer peripheral surface of the shaft portion 5. An opening 17e (see FIG. 7 (b)) opening in a shape, and extending along the length direction of the shaft portion 5 with a narrower width than the opening 17e and gradually deeper from both ends in the length direction to the center portion In other words, the shaft portion 5 is formed so as to gradually become shallower from the longitudinal center portion to both longitudinal end portions, and both longitudinal end portions are continuous with the opening 17e. It has a slope portion 17d (see FIG. 5) having a substantially V-shaped cross section, and a side wall portion 17c rising from both widthwise end portions of the slope portion 17d and continuing to the widthwise end portion of the opening 17e. The bottom portion (the lower end portion of the V-shape) of the slope portion 17d is formed in a curved surface shape.

  Further, the first hole portion 17a and the second hole portion 17b are respectively twisted of the shaft portion 5 when the exhaust camshaft 2 is rotated in the predetermined direction (forward rotation direction) by receiving the rotational force of the crankshaft. The rigidity is formed so as to be larger than the torsional rigidity of the shaft portion 5 when it is assumed that the exhaust camshaft 2 rotates in a direction (reverse direction) opposite to the predetermined direction.

  Specifically, as shown in FIGS. 1, 2, and 4, the first hole portion 17 a and the second hole portion 17 b each have a shaft portion that gradually shifts in the rotation delay direction as it approaches the sprocket mounting portion 4. It inclines with respect to 5 centerline CL1. The inclination angles of the first hole portion 17a and the second hole portion 17b with respect to the center line CL1 can be arbitrarily set in a range larger than 0 ° and smaller than 90 °, and are not particularly limited. In addition, the inclination angles of the first hole portion 17a and the second hole portion 17b with respect to the center line CL1 may be the same as or different from the inclination angles of the first hole portion 16a and the second hole portion 16b. Also good.

  The first hole portion 17a is formed in the same shape and the same size as the second hole portion 17b at a position opposite to the second hole portion 17b with respect to the center line CL1 of the shaft portion 5. The inclination angle with respect to the center line CL1 is set to be the same as the inclination angle of the second hole portion 16b. Further, as shown in FIG. 7B, the central portion in the length direction of the first hole portion 17a is formed at a position where the rotation is delayed by about 90 ° with respect to the apex of the nose portion 8a of the third cam portion 8. The central portion in the length direction of the second hole portion 17b is formed at a position where the rotation has advanced by approximately 90 ° with respect to the apex of the nose portion 8a of the third cam portion 8. The first hole 17a and the second hole 17b correspond to the “thinning portion” of the present invention.

  The rotation angle adjusting portion 18 is a portion protruding in a hexagonal cross section (regular hexagon) from the outer periphery of the shaft portion 5 to the radially outer side. The rotation angle adjusting unit 18 is used by being engaged with a spanner during engine inspection or the like. That is, at the time of engine inspection or the like, by rotating the spanner by engaging the rotation angle adjusting portion 18 with the opening portion of the spanner, the shaft portion 5 can be rotated and the exhaust port can be closed by the exhaust valve. Thereby, it is possible to prevent foreign matters such as dust from entering from the exhaust port during engine inspection or the like.

  As shown in FIG. 5, the hole 19 has a first hole 19 a that opens at a predetermined position on one side in the radial direction of the shaft portion 5, and a first hole that opens at a predetermined position on the other side in the radial direction of the shaft portion 5. 2 holes 19b. The first hole portion 19a and the second hole portion 19b are formed so as to gradually narrow toward the center from the radially outer side of the shaft portion 5, and more specifically, the hole portion 17a and the hole portion 17b Similarly, it is formed in a substantially V-shaped cross section, but in order to avoid interference with the camshaft identification ring 14, it is formed shorter in the length direction of the shaft portion 5 than the hole portion 17a and the hole portion 17b. .

  Further, as shown in FIGS. 1, 2, and 4, the first hole 19 a and the second hole 19 b are each centered on the shaft portion 5 so as to gradually shift in the rotation delay direction as approaching the sprocket mounting portion 4. It is inclined with respect to the line CL1. The inclination angles of the first hole portion 19a and the second hole portion 19b with respect to the center line CL1 can be arbitrarily set in a range larger than 0 ° and smaller than 90 °, and are not particularly limited. Further, the inclination angles of the first hole portion 19a and the second hole portion 19b with respect to the center line CL1 may be the same as or different from the inclination angles of the first hole portion 16a and the second hole portion 16b. Also good.

  The central portion in the length direction of the first hole portion 19a is formed at a position where the rotation has advanced by approximately 90 ° with respect to the apex of the nose portion 11a (see FIG. 2) of the sixth cam portion 11, and the second hole portion The central portion in the length direction of 19b is formed at a position where the rotation is delayed by approximately 90 ° with respect to the apex of the nose portion 11a of the sixth cam portion 11. The first hole portion 19a and the second hole portion 19b correspond to the “thinning portion” of the present invention.

  The camshaft identification ring 14 is a portion protruding in a ring shape radially outward from the outer periphery of the shaft portion 5. The arrangement position of the camshaft identification ring 14 in the length direction of the shaft portion 5 differs depending on the vehicle type. When the engine is assembled, the camshaft identification sensor reads the position of the camshaft identification ring 14, so that the engine assembly apparatus The corresponding vehicle type of the exhaust camshaft 2 can be identified.

  As shown in FIG. 5, a hole 45 extending in the axial direction (length direction) is formed in the central portion in the radial direction of the sprocket mounting portion 4. Further, the Oldham coupling portion 15 is formed with a hole portion 43 penetrating the inside thereof in the axial direction (length direction). Further, the journal portion 23 extends from the end portion of the shaft portion 5 on the Oldham coupling portion 15 side. A hole 44 extending in the length direction thereof and communicating with the hole 43 is formed over the portion corresponding to.

<Structure of intake camshaft>
As shown in FIG. 1, the intake camshaft 3 includes a columnar shaft portion 48 extending in the cylinder row direction, and eight cam portions integrally provided on the outer periphery of the shaft portion 48 (from the left side in FIG. 1). In order, the first cam portion 30, the second cam portion 31, the third cam portion 32, the fourth cam portion 33, the fifth cam portion 34, the sixth cam portion 35, the seventh cam portion 36, and the eighth cam portion 37. ), Journal portions 49 to 52 (see FIG. 6) that are integrally provided on the outer periphery of the shaft portion 48 and are rotatably supported by the bearing portions 74 to 77, respectively, and a sprocket (not shown) around which a timing chain is wound. The sprocket mounting portion 28 provided integrally with one end portion of the shaft portion 48 is connected to the drive shaft (not shown) of the fuel pump, and the other end portion of the shaft portion 48 is attached. Oldham coupling unit Has a 0 and. The intake camshaft 3 receives a rotational force of the crankshaft and rotates in a certain direction. In the example shown in FIG. 1, the intake camshaft 3 is clockwise (clockwise) when viewed from the left side. Rotate.

  In the intake camshaft 3, the first cam portion 30 and the second cam portion 31 are eccentric cams provided corresponding to the first cylinders, respectively, and these journal portions 49 (see FIG. 6). Are adjacent to each other. The first cam portion 30, the second cam portion 31, and the journal portion 49 are located above the first cylinder and on the intake side. The third cam portion 32 and the fourth cam portion 33 are eccentric cams provided corresponding to the second cylinder, respectively, and these are adjacent to each other via the journal portion 50. The third cam portion 33, the fourth cam portion 34, and the journal portion 50 are located above the second cylinder and on the intake side. The fifth cam portion 34 and the sixth cam portion 35 are eccentric cams provided in correspondence with the third cylinder, respectively, and are adjacent to each other via the journal portion 51. The fifth cam portion 34, the sixth cam portion 35, and the journal portion 51 are located above the third cylinder and on the intake side. The seventh cam portion 36 and the eighth cam portion 37 are eccentric cams provided corresponding to the fourth cylinder, respectively, and these are adjacent to each other via the journal portion 52. The seventh cam portion 36, the eighth cam portion 37, and the journal portion 52 are located above the fourth cylinder and on the intake side. Each of the cam portions 30 to 37 includes one nose portion 30a to 37a (see FIGS. 1 and 6) that protrudes radially outward from the base circle.

  As described above, the cam parts 30 to 37 of the intake camshaft 3 take in the intake air as the explosion order of each cylinder changes from the first cylinder → the third cylinder → the fourth cylinder → the second cylinder. The camshaft 3 is provided with a phase difference from each other so that the intake valve is opened in the above-described explosion order every 90 ° rotation of the camshaft 3.

  The shaft portion 48 of the intake camshaft 3 has a hole 38 in a section between the sprocket mounting section 28 and the first cam section 30, and a section between the second cam section 31 and the third cam section 32. Camshaft identification ring 53 and hole 39, between the fourth cam portion 33 and the fifth cam portion 34, between the rotation angle adjusting portion 40 and between the sixth cam portion 35 and the seventh cam portion 36. And a hole 42 in a section between the eighth cam section 37 and the Oldham coupling section 90.

  As shown in FIG. 6, the hole 38 has a first hole 38a that opens at a predetermined position on one side in the radial direction of the shaft 48 and a second hole that opens at a predetermined position on the other side in the radial direction of the shaft 48. And a hole 38b. The first hole portion 38a and the second hole portion 38b each extend along the length direction of the shaft portion 48, and the radial direction of the shaft portion 48 is the same as the hole portion 16 of the exhaust camshaft 2. It is formed so as to gradually narrow from the outside toward the center.

  Further, the first hole 38a (see FIGS. 1 and 6) and the second hole 38b (see FIG. 6) are each centered on the shaft portion 48 so as to gradually shift in the rotation delay direction as the sprocket mounting portion 28 is approached. It is inclined with respect to the line CL2. The inclination angle of the first hole 38a and the second hole 38b with respect to the center line CL2 can be arbitrarily set in a range larger than 0 ° and smaller than 90 °, and is not particularly limited.

  The first hole 38 a is formed on the apex side of the nose portion 30 a of the first cam portion 30, and specifically, the central portion in the length direction of the first hole 38 a is the nose of the first cam portion 30. The apex of the portion 30a and the rotation angle (phase) are formed at substantially the same position. The second hole portion 38b is formed on the opposite side of the first cam portion 30 from the nose portion 30a. Specifically, the center portion in the length direction of the second hole portion 38b is the nose portion of the first cam portion 30. It is formed at a position where the rotation angle (phase) differs from the apex of 30a by approximately 180 °. The first hole 38a and the second hole 38b correspond to the “thinning portion” of the present invention.

  As shown in FIG. 6, the hole 39 has a first hole 39 a that opens at a predetermined position on one side in the radial direction of the shaft 48, and a first hole that opens at a predetermined position on the other side in the radial direction of the shaft 48. 2 holes 39b. The first hole portion 39a and the second hole portion 39b each extend along the length direction of the shaft portion 48, and the radial direction of the shaft portion 48 is the same as the hole portion 17 of the exhaust camshaft 2. It is formed so as to gradually narrow from the outside toward the center. The first hole 39a and the second hole 39b are formed shorter than the hole 17a and the hole 17b of the exhaust camshaft 2 in order to avoid interference with the camshaft identification ring 53.

  Further, the first hole portion 39a (see FIGS. 1 and 6) and the second hole portion 39b (see FIG. 6) are each centered on the shaft portion 48 so as to gradually shift in the rotation delay direction as the sprocket mounting portion 28 is approached. It is inclined with respect to the line CL2. The inclination angle of the first hole 39a and the second hole 39b with respect to the center line CL2 can be arbitrarily set in a range larger than 0 ° and smaller than 90 °, and is not particularly limited.

  Further, the first hole 39a is formed at a position where the rotation is advanced by approximately 90 ° with respect to the apex of the nose portion 32a (see FIG. 1) of the third cam portion 32, and the second hole 39b is formed by the third cam The rotation is formed at a position delayed by about 90 ° with respect to the apex of the nose portion 32a of the portion 32. The first hole 39a and the second hole 39b correspond to the “thinning portion” of the present invention.

  As shown in FIG. 6, the hole 41 has a first hole 41 a that opens at a predetermined position on one side in the radial direction of the shaft portion 48, and a first hole that opens at a predetermined position on the other side in the radial direction of the shaft portion 48. 2 holes 41b. The first hole portion 41a and the second hole portion 41b each extend in the length direction of the shaft portion 48, and, like the hole portion 19 of the exhaust camshaft 2, center from the radially outer side of the shaft portion 48. It is formed so as to gradually narrow toward the front.

  Further, the first hole portion 41a (see FIGS. 1 and 6) and the second hole portion 41b (see FIG. 6) are each centered on the shaft portion 48 so as to gradually shift in the rotation delay direction as the sprocket mounting portion 28 is approached. It is inclined with respect to the line CL2. The inclination angle of the first hole 41a and the second hole 41b with respect to the center line CL2 can be arbitrarily set in a range larger than 0 ° and smaller than 90 °, and is not particularly limited.

  The central portion in the length direction of the first hole portion 41a is formed at a position where the rotation is delayed by about 90 ° with respect to the apex of the nose portion 35a (see FIG. 1) of the sixth cam portion 35, and the second hole portion The central portion in the length direction of 41b is formed at a position where the rotation has advanced approximately 90 ° with respect to the apex of the nose portion 35a of the sixth cam portion 35. The first hole 41a and the second hole 41b correspond to the “thinning portion” of the present invention.

  As shown in FIG. 6, the hole 42 has a first hole 42 a that opens at a predetermined position on one side in the radial direction of the shaft 48, and a first hole 42 a that opens at a predetermined position on the other side in the radial direction of the shaft 48. 2 holes 42b. Each of the first hole portion 42a and the second hole portion 42b extends in the length direction of the shaft portion 48 and, like the hole portion 41, gradually narrows from the radially outer side of the shaft portion 48 toward the center. It is formed as follows.

  Further, the first hole portion 42a (see FIGS. 1 and 6) and the second hole portion 42b (see FIG. 6) are each centered on the shaft portion 48 so as to gradually shift in the rotational delay direction as the sprocket mounting portion 28 is approached. It is inclined with respect to the line CL2. The inclination angles of the first hole portion 42a and the second hole portion 42b with respect to the center line CL2 of the shaft portion 48 can be arbitrarily set in a range larger than 0 ° and smaller than 90 °, and are not particularly limited.

  The first hole portion 42a and the second hole portion 42b are formed shorter in the length direction of the shaft portion 48 than the hole portion 41a and the hole portion 41b. The first hole portion 42 a is formed at a position where the rotation angle (phase) differs from the apex of the nose portion 37 a of the eighth cam portion 37 by approximately 180 °, and the second hole portion 42 b is formed of the eighth cam portion 37. The rotation angle is substantially the same as the apex of the nose portion 37a. The first hole portion 42a and the second hole portion 42b correspond to the “thinning portion” of the present invention.

  In addition, the hole portions indicated by reference numerals 61, 60, and 62 in FIG. 1 are respectively a hole portion through which the shaft portion of the intake valve corresponding to the first cylinder is inserted, a hole portion through which the shaft portion of the exhaust valve is inserted, It is a hole provided with a fuel injection valve. Similarly, holes indicated by reference numerals 64, 63, and 65 are holes through which the shaft portion of the intake valve corresponding to the second cylinder is inserted, holes through which the shaft portion of the exhaust valve is inserted, and fuel injection, respectively. It is a hole provided with a valve. In addition, holes indicated by reference numerals 67, 66, and 68 are a hole through which the shaft of the intake valve corresponding to the third cylinder is inserted, a hole through which the shaft of the exhaust valve is inserted, and a fuel injection valve, respectively. Is a hole provided. The holes denoted by reference numerals 91, 69, 71 are provided with a hole portion through which the shaft portion of the intake valve corresponding to the fourth cylinder is inserted, a hole portion through which the shaft portion of the exhaust valve is inserted, and a fuel injection valve. Hole.

  As shown in FIG. 6, a hole 46 extending in the axial direction (length direction) is formed in the central portion in the radial direction of the sprocket mounting portion 28. Further, the Oldham coupling portion 90 is formed with a hole portion 47 penetrating the inside thereof in the axial direction (length direction).

<Operational effects of this embodiment>
According to the exhaust camshaft 2 according to the present embodiment, the following operational effects can be achieved. In addition, although the same effect is show | played also in the intake camshaft 3, since it overlaps, the description is abbreviate | omitted.

  That is, according to the present embodiment, the exhaust camshaft 2 can be effectively reduced in weight while ensuring the torsional rigidity of the shaft portion 5 when the exhaust camshaft 2 rotates.

  More specifically, in the present embodiment, since the shaft portion 5 has the hole portions 38a, 38b, 39a, 39b, 41a, and 41b, the weight corresponding to the volume of the hole portion as compared with the case where these holes are not provided. Accordingly, the exhaust camshaft 2 can be reduced in weight.

  Moreover, the torsional rigidity of the shaft portion 5 can be ensured for the following reason. In other words, the exhaust camshaft 2 according to the present embodiment is rotated in a certain direction by receiving the rotational force of the crankshaft. The torsional rigidity of the shaft part 5 when rotating in the direction is larger than the torsional rigidity of the shaft part 5 when it is assumed that the exhaust camshaft 2 is rotating in the direction opposite to the fixed direction (reverse direction). In other words, the shaft portion 5 is configured such that the torsional rigidity in the forward rotation direction is relatively larger than the torsional rigidity in the reverse rotation direction.

  Specifically, since the hole 16a and the like are inclined with respect to the center line CL1 of the shaft portion 5 so as to be shifted in the rotation delay direction as approaching the sprocket mounting portion 4, the hole portion is center line of the shaft portion. As compared with the case where the exhaust camshaft 2 is inclined in the direction opposite to the direction of the inclination and the case where the hole extends parallel to the axial direction of the shaft portion, (Direction) The torsional rigidity of the shaft portion 5 during rotation can be further ensured.

  For this reason, according to the exhaust camshaft 2, as in the camshaft described in Patent Document 1, a hollow portion having the same shape is formed in the central portion in the radial direction of the shaft portion over the entire circumferential direction. Compared to the case (the torsional rigidity of the shaft part in the forward rotation direction is the same as the torsional rigidity of the shaft part in the reverse direction), the torsional rigidity of the shaft part 5 in the forward rotation direction can be secured larger. As a result, the shaft portion 5 of the exhaust camshaft 2 can be largely thinned as compared with a camshaft in which the shaft portion is simply formed in a cylindrical shape as in Patent Document 1, and as a result, the shaft portion 5 The exhaust camshaft 2 can be further reduced in weight while ensuring torsional rigidity in the forward rotation direction.

  Moreover, according to this embodiment, since the said hole part 38a etc. are holes which open to the outer peripheral surface of the axial part 5, and are extended along the axial direction of the axial part 5, they can be formed easily.

<Other embodiments>
Although the embodiments of the exhaust camshaft 2 and the intake camshaft 3 have been described above, the embodiments can be changed as follows.

  For example, the embodiment of the intake camshaft 3 can be changed as follows, and the same change can be made for the exhaust camshaft 2.

  That is, in the intake camshaft 3 according to the above embodiment, the depth of the first hole 38a and the depth of the second hole 38b are set to be the same (see FIG. 6), but the depth of the second hole 38b. May be set shallower than the depth of the first hole 38a. In this case, the holes 38 a and 38 b can be formed at an appropriate depth according to the stress generated in the shaft portion 48, and deformation of the shaft portion 48 can be suppressed.

  Moreover, in the said embodiment, although the hole 38 (the 1st hole 38a and the 2nd hole 38b) of the intake camshaft 3 is made into the non-through-hole, the hole 380 shown by Fig.8 (a) is shown. Thus, it is good also as a hole which penetrates the axial part 48 to radial direction, and the same change is possible also about the hole 42 of the intake camshaft 3. FIG. Also in this case, the one radial side portion and the other radial side portion of the hole 380 are formed so as to gradually narrow from the radially outer side toward the center. In this case, it is possible to further reduce the weight of the intake camshaft 3 by increasing the volume of the hole as compared with the case where the hole is a non-through hole.

  In the above-described embodiment, the hole 38 of the exhaust camshaft 2 includes the first hole 38 a that is a non-through hole that opens at a predetermined position on one side in the radial direction of the shaft 48, and the other side in the radial direction of the shaft 48. The second hole portion 38b is a non-through hole that opens at a predetermined position. However, like the hole portion 381 shown in FIG. You may form only with the non-through-hole extended toward the radial direction other side. In this case, the hole 381 is formed so as to gradually narrow from the one radial side to the other radial side. In addition, the hole 381 may extend to a position exceeding the radial center as shown in FIG.

  In the above embodiment, the shaft portion 48 of the intake camshaft 3 has a solid central portion in the radial direction. However, as shown in FIG. 9, the central portion in the radial direction of the shaft portion 48 is hollow. May be. In the example shown in FIG. 9, the shaft portion 48 extends in the lengthwise direction of the shaft portion 48 at the center portion in the radial direction, and both ends thereof are the hole portion 46 of the sprocket mounting portion 28 and the Oldham coupling portion. The hollow portion 91 having a circular cross section communicating with the 90 hole portions 47 is formed into a cylindrical shape. And this hollow part 91 is connected with the said hole part 38a, 38b, 39a, 39b, 41a, 41b, 42a, 42b (refer FIG. 9, 10 (a), (b)).

  In this case, it is possible to further reduce the weight of the intake camshaft 3 by a weight corresponding to the volume of the hollow portion 91 compared to the case where the hollow portion 91 is not formed.

  The intake camshaft 3 shown in FIG. 9 can be further modified as follows. 11 and 12, in place of the hole 39 (first hole 39a, second hole 39b) and hole 41 (first hole 41a, second hole 41b), respectively, A hole 390 (first hole 390a, second hole 390b) and a hole 410 (first hole 410a, second hole 410b) are formed. Of the holes 38a and the like, only the holes 38a, 38b, 42a, and 42b communicate with the hollow part 91, and the holes 390a, 390b, 410a, and 410b do not communicate with the hollow part 91. Specifically, the depth of each of the first hole 390a and the second hole 390b constituting the hole 390 and the first hole 410a and the second hole 410b constituting the hole 410 is determined by the hole 38a. , 38b and the hole 42a and the hole 42b are set to a depth which is shallower than the respective depths and does not reach the hollow portion 91.

  In this case, the facets generated when the solid shaft portion is cut can be quickly discharged to the outside through the holes 38a, 38b, 42a, 42b, and as a result, the efficiency of the cutting can be improved. it can. And between the 2nd cam part 31 and the 3rd cam part 32, and between the 6th cam part 35 and the 7th cam part 36, hole part 39a, 39b, 41a, 41b and the hollow part 91 are formed. It is possible to prevent a decrease in strength of the shaft portion 48 due to the communication.

  Further, in the embodiment shown in FIGS. 9 and 10, the shaft portion 48 of the intake camshaft 3 has a hole portion 38a or the like that opens on the outer peripheral surface. However, as shown in FIGS. Instead of the portions 38, 39, 41, 42, a hole portion 382 (first hole portion 382 a, formed so as to be recessed radially outward from the inner peripheral surface of the shaft portion 48 and extending along the axial direction of the shaft portion 48. Second hole 382b), hole 392 (first hole 392a, second hole 392b), hole 411 (first hole 411a, second hole 411b), hole 421 (first hole 421a) , A second hole 421b) may be formed. Also in this case, each of the holes 382, 392, 411, and 421 is inclined with respect to the center line of the shaft portion 48 so as to gradually shift in the rotation delay direction as the sprocket attachment portion 28 is approached. In the example shown in FIGS. 13 and 14, these hole portions 382, 392, 411, and 421 are non-through holes that do not open on the outer peripheral surface of the shaft portion 48.

  Also in the intake camshaft 3 shown in FIGS. 13 and 14, the holes 382, 392, 411, and 421 are inclined with respect to the center line of the shaft portion 48 so as to shift in the rotation delay direction as the sprocket mounting portion 28 is approached. Therefore, it is possible to greatly reduce the weight of the intake camshaft 3 while ensuring the torsional rigidity of the shaft portion 48 in the fixed direction (forward rotation direction).

  The exhaust camshaft 2 and the intake camshaft 3 according to each of the above embodiments are applied to an in-line four-cylinder diesel engine, but may be applied to a diesel engine having another number of cylinders, or a gasoline engine. May be applied.

DESCRIPTION OF SYMBOLS 1 Engine 2 Exhaust camshaft 3 Intake camshaft 5 Exhaust camshaft shaft part 6-13 Exhaust camshaft cam part 16, 17, 19, Exhaust camshaft hole part 30-37 Intake camshaft cam part 38,39 , 41, 42, 380, 381, 382, 390, 392, 410, 411, 421 Intake camshaft hole 48 Intake camshaft shaft 91 Hollow part

Claims (3)

An engine camshaft comprising a shaft portion and a cam portion provided on the outer periphery of the shaft portion, and receiving a rotational force of the crankshaft and rotating in a predetermined direction,
The shaft portion has a meat removal portion,
In the thinning portion, the torsional rigidity of the shaft portion when the camshaft rotates in the constant direction in response to the rotational force of the crankshaft is such that the camshaft is in a direction opposite to the constant direction. An engine camshaft, wherein the camshaft is formed so as to be larger than a torsional rigidity of the shaft when it is assumed to be rotating. A driving mechanism connecting portion to which a rotation driving mechanism for rotating the shaft portion in the predetermined direction is connected to one end portion of the shaft portion,
The said thinning part is a hole which opens in the outer peripheral surface of the said shaft part, and extends along the axial direction of the said shaft part, and the said hole part shifts | deviates to a rotation delay direction gradually as the said drive mechanism connection part is approached. The engine camshaft according to claim 1, wherein the camshaft is inclined with respect to a center line of the shaft portion. A driving mechanism connecting portion to which a rotation driving mechanism for rotating the shaft portion in the predetermined direction is connected to one end portion of the shaft portion,
The shaft portion has a cylindrical shape with a hollow portion extending in the length direction of the shaft portion at a radial center portion;
The thinning portion is a hole portion that is formed to be recessed radially outward from the inner peripheral surface of the shaft portion and extends along the axial direction of the shaft portion, and the hole portion is connected to the drive mechanism connecting portion. 2. The engine camshaft according to claim 1, wherein the camshaft is inclined with respect to a center line of the shaft portion so as to gradually shift in a rotation delay direction as approaching.

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