JP2004211687A - Valve system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce rotational resistance by improving rigidity of an abutting part of a third rocker arm 6 to a rotating second low lift cam 12. <P>SOLUTION: A mechanism has a first rocker arm 5, a second rocker arm 7 and the third rocker arm 6, and switches a driving cam for opening-closing an intake valve and a second intake valve by supply/ release of pressure oil. A third roller follower 24 of the third rocker arm 6 is formed of a double ring-shaped sliding roller structure of an inner roller 22 and an outer roller 23. Impact strength is improved: the rigidity of the abutting part of the third rocker arm 6 to the rotating second low lift cam is improved; the rotation resistance is reduced; friction is reduced by forming a second roller follower 27 to a high lift cam 20 out of a needle bearing; and the rotational resistance is reduced. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a valve train for an internal combustion engine that can open and close intake and exhaust valves of the internal combustion engine at different drive timings.

  In recent years, operating characteristics of intake valves and exhaust valves (engine valves) provided in a reciprocating internal combustion engine (engine), that is, opening / closing timing and opening period, are optimized in accordance with the load state and speed state of the engine. Switchable valve trains have been developed and put into practical use.

In such a valve train, as one of the mechanisms for switching the operating characteristics, for example, a low-speed cam having a cam profile suitable for low-speed rotation of the engine and a high-speed cam having a cam profile suitable for high-speed rotation of the engine are provided. A cam has been developed which selectively uses a cam according to the rotation state of an engine to open and close an engine valve.

  For example, Patent Documents 1 and 2 disclose a drive rocker arm that swings by a low-speed cam to drive an engine valve, a high-speed rocker arm that swings by a high-speed cam having a cam profile including a low-speed cam, There has been disclosed a technology including a connection switching mechanism that switches a connection state and a disconnection state between a drive rocker arm and a high-speed rocker arm.

  In the conventional technology, when the drive rocker arm and the high-speed rocker arm are separated from each other by the connection switching mechanism, the high-speed rocker arm swings freely, and the drive rocker arm swings by the low-speed cam to correspond to the cam profile of the low-speed cam. Activate the engine valve with the characteristic.

  On the other hand, when the drive rocker arm and the high-speed rocker arm are connected by the connection switching mechanism, the high-speed rocker arm and the drive rocker arm swing together, and the drive rocker arm operates the engine valve with characteristics according to the cam profile of the high-speed cam. .

  In the conventional valve gear, when the drive rocker arm and the high-speed rocker arm are connected to operate the engine valve, the high-speed cam has a cam profile including the low-speed cam. The lift amount by the high-speed cam is larger than the lift amount. Therefore, the operation is performed in a state where a gap is formed between the low-speed cam and the drive rocker arm.

  Since the drive rocker arm and the high-speed rocker arm are constantly urged toward the cam, if the drive rocker arm and the high-speed rocker arm are separated from each other by the connection switching mechanism in this state, for example, the drive rocker arm and the low-speed cam are disconnected during the maximum lift. Since the gap is largest, there is a possibility that the drive rocker arm may be hit against the low-speed cam. Therefore, the structure of the contact portion of the drive rocker arm with respect to the rotating low-speed cam needs to consider rigidity at present.

JP-A-63-170513 JP 2001-41017 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a valve train for an internal combustion engine in which rigidity and resistance of a support portion at a contact portion of a rocker arm with a rotating cam are optimized.

  According to a first aspect of the present invention, there is provided a valve operating apparatus for an internal combustion engine, the tip of which is linked to a first intake valve or a first exhaust valve and is swingably supported by the rocker shaft. A first rocker arm driven by the first low lift cam, and a height provided to be connectable to the first rocker arm side and swingably supported by the rocker shaft and having a greater lift amount than the first low lift cam. A second rocker arm driven by a lift cam, a first roller follower provided on a base end side of the first rocker arm and abutting on the first low lift cam of a cam shaft, and a second locker arm provided on a base end side of the second rocker arm. A second roller follower abutting on the high lift cam of the camshaft, and a connection state of the second rocker arm to the first rocker arm; Ri separated and a connection switching mechanism for switching the state, together with the first roller follower is formed as a sliding roller, the second roller follower, characterized in that it is formed as a needle bearing using a needle roller.

  According to a second aspect of the present invention, there is provided a valve gear for an internal combustion engine, the tip of which is linked to a first intake valve or a first exhaust valve and is swingably supported by the rocker shaft and driven by a first low lift cam. A first rocker arm having a distal end linked to a second intake valve or a second exhaust valve, and being swingably supported by the rocker shaft and driven by a second low lift cam having a smaller lift than the first low lift cam. A third rocker arm, a second rocker arm having a distal end provided to be connectable to the first rocker arm, swingably supported by the rocker shaft, and driven by a high lift cam having a larger lift than the first low lift cam; A first roller follower provided on a base end side of the first rocker arm and abutting on the first low lift cam of a camshaft; and a third rocker arm. A third roller follower provided on the base end side of the cam shaft and in contact with a second low lift cam of the camshaft; and a second roller follower provided on the base end side of the second rocker arm and in contact with the high lift cam of the camshaft. A connection switching mechanism for switching between a connected state and a disconnected state of the second rocker arm with respect to the first rocker arm and the third rocker arm, wherein at least the second roller follower of the first roller follower and the second roller follower is a needle. The third roller follower is formed as a sliding roller, and is formed as a needle bearing using a roller.

  According to a third aspect of the invention, there is provided a valve gear for an internal combustion engine according to the first or second aspect, wherein the sliding roller is a double ring-shaped sliding roller.

  In the valve operating device for an internal combustion engine according to the first aspect, the first roller follower having a small lift amount is configured as a sliding roller structure to improve impact strength, and even if the first roller follower is hit against the low lift cam by a large force, The force is transmitted by the pressure, so that deformation and indentation do not occur, and the contact portion of the first rocker arm with respect to the rotating low lift cam has a structure considering rigidity and rotation resistance, and the second rocker arm with respect to the high lift cam has The roller follower reduces friction as a needle bearing and has a structure that takes into account rotational resistance.

  In the valve gear of the internal combustion engine according to the second aspect, the third roller follower having a smaller lift amount is formed as a sliding roller structure to improve the impact strength, and the third roller follower hits the second low lift cam with a large force. The force is transmitted by the surface pressure even when the third rocker arm rotates, so that deformation and indentation do not occur, and the contact portion of the third rocker arm with respect to the rotating low-lift side cam has a structure that considers rigidity. The second roller follower for the high lift cam reduces the friction as a needle bearing and has a structure that takes into account the rotational resistance.

  In the valve gear for an internal combustion engine according to the third aspect, friction can be reduced while considering durability.

  FIG. 1 is a plan view showing a head portion of an internal combustion engine provided with a valve train according to an embodiment of the present invention, FIG. 2 is an enlarged view of a main part in FIG. 1, and FIG. FIG. 4 is a view taken along a line IV-IV in FIG. 2, FIG. 4 is a view taken along a line VV in FIG. 2, FIG. 6 is a cross section of a piston support, FIG. 8 is a perspective view of the rocker arm from the intake valve side, FIG. 9 is a perspective view of a main part of the internal combustion engine showing the hydraulic system, FIG. 10 is a cross section showing the state of attachment of the accumulator, FIG. 2 shows a schematic circuit status of the hydraulic system.

  As shown in FIG. 1, a rocker shaft 2 on the intake side and a rocker shaft 3 on the exhaust side are fixed to the cylinder head 1 in parallel. A camshaft 4 is rotatably supported on the cylinder head 1 between the rocker shaft 2 and the rocker shaft 3. The illustrated internal combustion engine has a configuration in which two intake valves and two exhaust valves are provided for one cylinder in a series of four cylinders.

  As shown in FIGS. 1 to 5, a first rocker arm 5 and a third rocker arm 6 are supported on the rocker shaft 2 corresponding to each cylinder so as to be swingable, respectively, and are provided between the first rocker arm 5 and the third rocker arm 6. A rocker shaft 2 in which a T-shaped second rocker arm 7 is swingably supported. The first rocker arm 5 and the third rocker arm 6 are formed with a cylinder portion 8 as a connection switching mechanism. The T-shaped tips 7a and 7b of the second rocker arm 7 can be connected to the cylinder portion 8.

  The distal end of the first rocker arm 5 is linked to the first intake valve 9, and the proximal end of the first rocker arm 5 is driven by the first low lift cam 10. The distal end of the third rocker arm 6 is linked to the second intake valve 11, and the proximal end of the third rocker arm 6 is driven by a second low lift cam 12 having a smaller lift than the first low lift cam 10. That is, the first intake valve 9 and the second intake valve 11 are opened and closed with different lift amounts at predetermined timings. The shape of the second low-lift cam 12 can be substantially selected so that the second intake valve 11 is in a resting state.

  As shown in FIGS. 3, 4, 7, and 8, the first rocker arm 5 and the third rocker arm 6 are each formed with a cylinder portion 8, and each cylinder portion 8 has a T-shape of the second rocker arm 7. Openings 13a, 13b are formed opposite to the tips 7a, 7b of the openings. Pistons 14a, 14b are slidably provided in the cylinder portion 8, and the pistons 14a, 14b are provided with cylindrical portions 15a, 15b slidably in contact with the inner wall of the cylinder portion 8 and are continuously opened above the cylindrical portions 15a, 15b. Cutout portions 16a and 16b are formed by cutting out portions 13a and 13b.

  The pistons 14a, 14b are urged downward by return springs 17a, 17b, and the cutouts 16a, 16b are always in a state of facing the openings 13a, 13b (the state of FIG. 4). An oil passage 18 is formed in the shaft center of the rocker shaft 2, and pressure oil is supplied to the oil passage 18 at a predetermined timing by a hydraulic supply mechanism described later. The pressure oil supplied to the oil passage 18 is supplied to the cylinder portion 8 from the passage 19, and the pressure oil is supplied to the cylinder portion 8, whereby the pistons 14a and 14b rise against the urging force of the return springs 17a and 17b. I do. The cylinders 15a, 15b face the openings 13a, 13b due to the rise of the pistons 14a, 14b due to the supply of the pressure oil (the state of FIG. 3).

  As shown in FIGS. 1 to 5, the T-shaped tips 7 a and 7 b of the second rocker arm 7 are linked to the inside of the openings 13 a and 13 b, and the base end of the second rocker arm 7 is driven by the high lift cam 20. . The high lift cam 20 has a larger lift amount than the first low lift cam 10 and the second low lift cam 12, and has a cam profile including the first low lift cam 10 and the second low lift cam 12.

  The pistons 14a, 14b are urged downward by the return springs 17a, 17b, and the notches 16a, 16b face the openings 13a, 13b (the state in which the pressure oil is not supplied). When driven by the lift cam 20, the T-shaped tips 7a and 7b of the second rocker arm 7 face the notches 16a and 16b in the openings 13a and 13b. For this reason, when the second rocker arm 7 is driven and rocked by the high lift cam 20, the tips 7a and 7b of the second rocker arm 7 enter the cutouts 16a and 16b (in a separated state), and the rocking of the second rocker arm 7 is prevented. It is not transmitted to the first rocker arm 5 and the third rocker arm 6.

  Therefore, by releasing the pressure oil of the cylinder portion 8, the first intake valve 9 and the second intake valve 11 are lifted at different timings at predetermined timings by the swinging of the first rocker arm 5 and the third rocker arm 6, respectively. Is opened and closed.

  When the pressure oil is supplied to the cylinder portion 8 and the pistons 14a, 14b rise against the urging force of the return springs 17a, 17b and the cylindrical portions 15a, 15b face the openings 13a, 13b, the second rocker arm. The T-shaped tips 7a, 7b of 7 face the cylindrical portions 15a, 15b in the openings 13a, 13b. For this reason, when the second rocker arm 7 swings by being driven by the high lift cam 20, the T-shaped tips 7a, 7b of the second rocker arm 7 come into contact with the cylindrical portions 15a, 15b (connected state). The swing of 7 is transmitted to the first rocker arm 5 and the third rocker arm 6 via the cylinder portion 8.

  Therefore, by supplying the pressure oil to the cylinder portion 8, the first intake valve 9 and the second intake valve 11 are raised by the swing of the first rocker arm 5 and the third rocker arm 6 caused by the swing of the second rocker arm 7. The lift cam 20 is simultaneously opened and closed with a large lift according to the cam profile.

  The supply and release of the pressurized oil to and from the cylinder portion 8, that is, the switching between the connected state and the disconnected state of the second rocker arm 7, the first rocker arm 5, and the third rocker arm 6 are determined by the running state of the vehicle (the rotation of the internal combustion engine). (Speed state).

  For example, when the rotation speed of the internal combustion engine is low, the supply of the pressure oil to the cylinder section 8 is released, and the first rocker arm 5 and the third rocker arm 6 swing, thereby causing the first intake valve 9 and the second intake valve to rotate. 11 are opened and closed at predetermined timings with different lift amounts. This promotes swirl and enhances combustion. When the rotation speed of the internal combustion engine is high, pressure oil is supplied to the cylinder section 8 and the first rocker arm 5 and the third rocker arm 6 swing by the swing of the second rocker arm 7 to cause the first intake valve 9 and The second intake valve 11 is simultaneously opened and closed with a large lift amount. As a result, a large amount of intake air is secured and the output is enhanced.

  As shown in FIGS. 3 and 7, a first roller follower 21 is provided at the base end side of the first rocker arm 5 in contact with the first low lift cam 10, and the first roller follower 21 rotates with respect to the rotating first low lift cam 10. The base end of the first rocker arm 5 is in contact with the minimum resistance through the first roller follower 21. As shown in FIG. 7, the first roller follower 21 is a needle bearing in which an outer roller 26 is rotatable via a number of needle rollers 25, and the outer roller 26 is brought into rolling contact with the first low lift cam 10. I have.

  As shown in FIGS. 4 and 7, a third roller follower 24 is provided at the base end side of the third rocker arm 6 in contact with the second low lift cam 12. The base end of the third rocker arm 6 is in contact with the third roller follower 24 without resistance. As shown in FIG. 7, the third roller follower 24 is formed as a double ring-shaped sliding roller of the inner roller 22 and the outer roller 23. The inner roller 22 and the outer roller 23 are rotatably fitted to each other concentrically, and the outer roller 23 is in rolling contact with the second low lift cam 12. The double ring-shaped sliding roller has a large friction when the roller rotation is low as compared with a needle bearing using a needle roller. Therefore, in order to reduce friction, the surface of the inner roller 22 is subjected to, for example, a finish for smoothing the surface or a lubrication surface treatment (sol vest treatment). As a result, the double ring-shaped sliding roller is more expensive than the needle bearing, and has high friction when the roller rotates at a low speed.

  As shown in FIGS. 5 and 7, a second roller follower 27 is provided at the base end side of the second rocker arm 7 in contact with the high lift cam 20, and the second roller follower 27 is provided for the rotating high lift cam 20. The base end of the second rocker arm 7 abuts without resistance via 27. The second roller follower 27 is a needle bearing in which an outer roller 29 is rotatable via a number of needle rollers 28, and the outer roller 29 is in rolling contact with the high lift cam 20. Accordingly, when the high lift cam 20 requiring high output is used, the first intake valve 9 and the second intake valve 11 are driven via the second roller follower 27 (needle bearing) having small friction, so that friction loss is reduced. The output can be reduced and the output can be further improved.

  The first roller follower 21 is composed of an inner roller 22 and an outer roller 23 (a double ring-shaped sliding roller), similarly to the third roller follower 24, and the outer roller 23 is rotatably connected to the first low lift cam 10. It is also possible to make it.

  As shown in FIG. 1, exhaust rocker arms 31a and 31b are swingably supported on the exhaust side rocker shaft 3, and the respective exhaust rocker arms 31a and 31b are driven by exhaust cams.

  Incidentally, for example, the lift amount of the first intake valve 9 and the second intake valve 11 by the high lift cam 20 is large, and the lift amount of the first intake valve 9 by the first low lift cam 10 is smaller than the lift amount by the high lift cam 20. The lift amount of the second intake valve 11 by the second low lift cam 12 is set to be considerably smaller than that by the high lift cam 20.

  Therefore, the first intake valve 9 and the second intake valve 9 are supplied by supplying the pressure oil to the cylinder portion 8 (in a connected state) and the first rocker arm 5 and the third rocker arm 6 being swung by the swinging of the second rocker arm 7. When the intake valve 11 is simultaneously opened and closed with a large lift, the lift by the high lift cam 20 is larger than the lift by the second low lift cam 12 and the first low lift cam 10. Therefore, a large gap is formed between the second low lift cam 12 and the third roller follower 24, and between the first low lift cam 10 and the first roller follower 21, the second lift cam 12, the third roller follower 24 The operation is performed in a state where a gap narrower than the interval is generated.

  Although the description is omitted, the second rocker arm 7 is constantly urged toward the cam by urging means (not shown). A state in which the first intake valve 9 and the second intake valve 11 are opened and closed by the supply of pressure oil to the cylinder section 8 and the swing of the first rocker arm 5 and the third rocker arm 6 caused by the swing of the second rocker arm 7. Then, when the supply of the pressure oil to the cylinder portion 8 is released, that is, when the intake state is switched, the transmission of the swing by the second rocker arm 7 is released, and the first rocker arm 5 and the third rocker arm 6 are pressed by the urging force. The first low lift cam 10 and the second low lift cam 12 swing.

  In this case, for example, at the time of the maximum lift, the gap between the second low lift cam 12 and the third roller follower 24 is large, so that the first rocker arm 5 and the third rocker arm 6 cause the first low lift cam 10 and When the third roller follower 24 and the first roller follower 21 are swung toward the second low lift cam 12, there is a possibility that the third roller follower 24 and the first roller follower 21 may be hit against the second low lift cam 12 and the first low lift cam 10.

  Since the gap between the first roller follower 21 and the first low lift cam 10 is small, a large force does not act. However, since the gap between the third roller follower 24 and the second low lift cam 12 is large, a large force is applied when being hit. Will work.

  For this reason, the third roller follower 24 in the present invention has a double ring-shaped sliding roller structure of the inner roller 22 and the outer roller 23. Since the third roller follower 24 has a double ring-shaped sliding roller structure, the impact strength is improved. Even if the third roller follower 24 is hit against the second low lift cam 12 with a large force, the force is generated by the surface pressure. As a result, there is no possibility that the outer roller 23 is damaged without deformation or indentation.

  Therefore, the contact portion of the third rocker arm 6 with respect to the rotating second low lift cam 12 has a structure in which rigidity and rotation resistance are considered.

  In the embodiment described above, in the internal combustion engine provided with two different types of the first rocker arm 5 and the third rocker arm 6 having a small lift amount with respect to the second rocker arm 7 having a large lift amount, the difference in the lift amount is larger. Although the example in which the third roller follower 24 has a double-ring-shaped sliding roller structure has been described, the present invention can also have the first roller follower 21 have a double-ring-shaped sliding roller structure.

  However, while the double-ring-shaped sliding roller has high rigidity, it is expensive as described above and has a large friction when the roller is rotated at a low speed. Therefore, when the double-ring-shaped sliding roller is used as the first roller follower 21, Needs to take into account cost and usage conditions. For example, when the first low lift cam 10 has a shape similar to the high lift cam 20, the distance between the first low lift cam 10 and the first roller follower 21 is small, so that it is preferable to use a needle roller. Conversely, when the first low lift cam 10 has a shape similar to the second low lift cam 12, the distance between the first low lift cam 10 and the first roller follower 21 is large, so that a double-ring-shaped sliding roller may be used. preferable. More specifically, if the distance between the first low lift cam 10 and the first roller follower 21 is less than half the distance between the second low lift cam 12 and the third roller follower 24, a needle roller is used and the first low lift cam 10 is used. If the distance between the second roller lift cam 12 and the third roller follower 24 exceeds half of the distance between the second low lift cam 12 and the third roller follower 24, a double ring-shaped sliding roller may be selected.

  Further, as shown in Japanese Patent Application Laid-Open No. 2001-41017 filed by the applicant of the present application, even in an intake single-valve type internal combustion engine having a structure in which two types of rocker arms having different lift amounts are switched, a cam having a smaller lift amount is used. It is possible to apply the present invention in which the contacting roller has a sliding roller structure as a first roller follower.

  In the above description, a double ring-shaped sliding roller is used as the sliding roller, but a single-shaped sliding roller formed only of the outer roller can be used. However, when a single-shaped sliding roller is used, the durability is inferior to that of a double-ring-shaped sliding roller, and there is a problem that the friction further increases. Therefore, when the first low-speed cam 10 and the second low-speed cam 12 are used, There is a possibility that the engine output may decrease, and when the high-speed cam 20 is used, the first intake valve 9 and the second intake valve 11 are operated via the needle bearing, so that friction loss is small. Therefore, the output deviation between the engine output when the high-speed cam 20 is used and the engine output when the low-speed cams 10 and 12 are used is further increased. There is. Therefore, it is preferable to use a double-ring-shaped sliding roller as the sliding roller.

  As shown in FIG. 8, since the notch 16 is formed in the upper part of the piston 14, the return spring 17 is arranged at a position shifted from the axial center of the piston 14. For this reason, when the piston 14 rotates around the central axis, the urging force of the return spring 17 does not become as designed. Accordingly, in the present embodiment, a mechanism for preventing the piston 14 from rotating is provided as shown in FIGS.

  As shown in FIGS. 2, 6, and 8, a notch surface 34 is formed on the outer periphery of the portion of the piston 14 where the notch 16 is formed, and the first rocker arm 5 and the third rocker arm 3 correspond to the notch surface 34. A boss 35 (see FIG. 2) is formed in the cylinder 8 of the rocker arm 6. The cutout surface 34 is formed at a position avoiding the opening 13 of the cylinder portion 8 and avoiding the back side of the piston 14, and is arranged in a state where the pin 36 is fitted in the cutout surface 34 in the axial direction. The pin 36 is fixed to the boss 35 by press-fitting or the like, and the pin 36 is disposed with a central axis extending on a plane parallel to a horizontal plane along the rocker shaft 2.

  As a detent, a pin 36 may be disposed at right angles to a horizontal plane along the rocker shaft 2, but if the pin 36 is disposed at right angles or the like, the pin 36 It is necessary to form a fitting portion for the pin 36. Since the cylindrical portion 15 is a portion that fits and slides on the cylinder portion 8 to prevent oil leakage, if the fitting portion of the pin 36 is formed in the cylindrical portion 15, oil may leak. For this reason, the pin 36 is disposed with its central axis extending on a plane parallel to the horizontal plane along the rocker shaft 2.

  When the first rocker arm 5 and the third rocker arm 6 swing by the swing of the second rocker arm 7, the portion receiving the load from the second rocker arm 7 side is the rear surface of the piston 14. For this reason, the pin 36 is disposed at an oblique position avoiding the back surface of the piston 14. The pin 36 is fixed to the boss 35 at a position avoiding the opening 13 of the cylinder 8. Thus, the distal ends 7a and 7b of the second rocker arm 7 are not prevented from moving from the opening 13 toward the piston 14, and the transmission of the oscillating power via the piston 14 can be performed on the entire rear surface.

  The cutout surface 34 is formed to an intermediate portion of the cylindrical portion 15, and the pin 36 prevents the piston 14 from coming off. As shown in FIGS. 2 and 8, the boss portions 35 of the cylinder portion 8 in the first rocker arm 5 and the third rocker arm 6 are formed in the same direction, the cutout surfaces 34 of the piston 14 are in the same direction, and the pins 36 are parallel. It is arranged in a state. For this reason, the pistons 14 of the first rocker arm 5 and the third rocker arm 6 can be shared, and it is possible to reduce component costs and prevent erroneous assembly.

  A first rocker arm 5, a third rocker arm 6, and a second rocker arm 7 are supported for each cylinder on the intake side rocker shaft 2, and the first rocker arm 5 and the third rocker arm 6 have a cylinder portion 8 and a piston 14. Is provided. Therefore, the valve opening / closing mechanism on the intake side is more complicated and heavier than the valve opening / closing mechanism on the exhaust side.

  Therefore, as shown in FIG. 1, the diameter D1 of the rocker shaft 2 on the intake side is formed larger (for example, about 10%) than the diameter D2 of the rocker shaft 3 on the exhaust side. Thus, the rigidity of the increased weight is secured, and the dynamic characteristics of the valve train can be improved. Further, by increasing the diameter D1 of the rocker shaft 2, the inner diameter of the oil passage 18 can also be increased, and the pressure loss of the pressure oil flowing through the oil passage 18 can be reduced to improve the performance of the switching mechanism. .

  A mechanism for supplying and discharging pressure oil to and from the oil passage 18 of the rocker shaft 2, that is, a mechanism for driving the piston 14 of the cylinder section 8 will be described with reference to FIGS.

  An oil passage 42 through which pressure oil from an oil pump 41 (see FIG. 11) flows is formed on the end side of the cylinder head 1. The oil passage 42 controls oil supply and discharge to and from the oil passage 18. A control valve 43 is provided. A pressure accumulation path 44 is provided branching from the oil passage 42 on the upstream side of the oil control valve 43, and an accumulator 45 is connected to the pressure accumulation path 44. The accumulator 45 is fixed to the cylinder head 1 as one member.

  A second filter 46 is provided in the oil passage 42 upstream of the oil control valve 43 and upstream of the branch of the pressure accumulation path 44. Reference numeral 47 in FIG. 11 denotes a first filter provided on the discharge side of the oil pump 41, and 48 denotes a bypass which bypasses the oil pump 41, and a relief valve (not shown) is interposed.

  As shown in FIG. 10, the accumulator 45 includes a cylindrical main body 51 fixed vertically to the cylinder head 1, and a piston 53 urged downward by a spring 52 is slidably provided on the main body 51. ing. A spring seat 54 and a snap ring 55 are provided on the upper part of the spring 52, and the spring 52 is housed in the main body 51.

  A screw portion 56 is formed at a lower portion of the main body 51, and the accumulator 45 is fixed to the cylinder head 1 by screwing the screw portion 56 into a female screw portion 57 of the cylinder head 1. When the accumulator 45 is fixed to the cylinder head 1, a part of the upper portion of the main body 51 is made to protrude from the upper surface of the cylinder head 1. When the main body 51 is fixed to the cylinder head 1, the pressure accumulation path 44 communicates with the main body 51, and the pressure oil is supplied to the lower side of the piston 53, and the piston 53 rises against the urging force of the spring 52. Pressure oil is accumulated in the main body 51.

  A cover 61 is provided on the upper part of the cylinder head 1, and a baffle plate 62 and a flat plate 63 are provided inside the cover 61 for collecting mist. The flat plate 63 is in a state where the flat plate 63 exists right above the upper part of the main body 51 projecting from the upper surface of the cylinder head 1. Therefore, even if the snap ring 55 comes off, the spring seat 54, the spring 52, and the piston 53 come into contact with the flat plate 63 and are prevented from scattering outside.

  The gap S1 between the upper portion of the main body 51 and the flat plate 63 is set shorter than the length S2 of the screw portion 56. For this reason, even if the main body 51 is loosely screwed into the cylinder head 1 and the main body 51 moves in the pulling-out direction (upward), the upper part of the main body 51 is flat before the screwing of the screw portion 56 is released. The main body 51 does not come off by coming into contact with the plate 63. Therefore, the oil passage 42 or the pressure accumulation passage 44 is not opened to the outside.

  Since the main body 51 of the accumulator 45 is fixed to the cylinder head 1 with the lower screw portion 56, even if oil leakage or the like occurs in the fixed portion, it does not leak to the outside. Thereby, even if the seal of the fixed portion is simplified, oil leakage to the outside is suppressed. Note that the fixing of the main body 51 may be a configuration other than the fixing by the screw portion 65, such as press-fit fixing or fixing by a combination of a flange and a fixing screw.

  In the mechanism for supplying and discharging pressure oil to and from the oil passage 18 of the rocker shaft 2 having the above-described configuration, when pressure oil is supplied from the oil passage 42 to the pressure accumulation passage 44 by driving the oil pump 41, the pressure oil is Is filtered and supplied to the oil control valve 43, the accumulator 45, and the rocker shaft 3 on the exhaust side. When the oil control valve 43 is off (closed), pressure oil is stored in the accumulator 45 by the oil pressure in the pressure accumulation path 44.

  When the engine reaches a predetermined rotational speed, the oil control valve 43 is turned on (open) to switch to driving of the high lift cam 20. Pressure oil rapidly flows into the oil passage 18 of the rocker shaft 2 on the intake side via the oil control valve 43. At this time, since the supply amount of the pressure oil is insufficient and the oil pressure in the oil passage 42 and the pressure accumulation passage 44 is temporarily reduced, the pressure oil stored in the accumulator 45 is pushed out by the urging force of the spring 52 and the shortage is generated. Pressure oil is supplemented.

  Therefore, the pressure oil is supplied to the switching mechanism having two cylinder portions 8 in one cylinder with good responsiveness without shortage of the pressure oil.

  By providing the second filter 46 on the upstream side of the accumulator 45, it is possible to remove foreign substances contained in the pressure oil accumulated in the accumulator 45. Therefore, no foreign matter enters the main body 51 of the accumulator 45, and no stick-slip occurs in the piston 53.

  Further, the pressure oil pushed out from the accumulator 45 is sent to the oil control valve 43 without passing through the second filter 46, so that the oil passage 18 of the rocker shaft 2 is not affected by the pressure loss flowing through the second filter 46. Pressure oil with high responsiveness.

  A switching mechanism including a first rocker arm 5, a third rocker arm 6, and a second rocker arm 7 is provided as an internal combustion engine to which the configuration of the accumulator 45 described above is applied and an internal combustion engine to which a circuit configuration having the second filter 46 is applied. However, the present invention can be applied to an internal combustion engine provided with a switching mechanism having another configuration. For example, as shown in Japanese Patent Application Laid-Open No. 2001-41017 filed by the assignee of the present application, the configuration of the accumulator 45 is applied to an intake one-valve internal combustion engine having a structure in which two types of rocker arms having different lift amounts are switched. It is possible to apply a circuit configuration in which the second filter 46 is provided.

  In the above-described embodiment, the example in which the cam switching mechanism is provided on the rocker shaft 2 on the intake side has been described. However, the present invention can be applied to a case where the mechanism for switching the cam is provided on the exhaust side. It is possible.

It is a top view showing the head part of the internal-combustion engine provided with the valve train concerning one embodiment of the present invention. It is a principal part enlarged view in FIG. FIG. 3 is a view taken along line III-III in FIG. 2. FIG. 4 is a view taken along the line IV-IV in FIG. 2. FIG. 5 is a view taken along line V-V in FIG. 2. It is sectional drawing of a piston support part. It is a perspective view of the rocker arm from the camshaft side. It is a perspective view of the rocker arm from the intake valve side. It is a principal part perspective view of the internal combustion engine showing a hydraulic system. It is sectional drawing showing the attachment situation of an accumulator. It is a schematic circuit diagram of a hydraulic system.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Cylinder head 2, 3 Rocker shaft 4 Camshaft 5 1st rocker arm 6 3rd rocker arm 7 2nd rocker arm 8 Cylinder part 9 1st intake valve 10 1st low lift cam 11 2nd intake valve 12 2nd low lift cam 13 Opening Part 14 piston 15 cylindrical part 16 notch part 17 return spring 18 oil passage 19 passage 20 high lift cam 21 first roller follower 22 inner roller 23 outer roller 24 third roller follower (sliding roller)
25, 28 Needle rollers 26, 29 Outer roller 27 Second roller follower (needle bearing)
34 Notch surface 35 Boss portion 36 Pin 41 Oil pump 42 Oil passage 43 Oil control valve 44 Accumulator 45 Accumulator 46 Second filter 47 First filter 48 Bypass passage 51 Main body 52 Spring 53 Piston 54 Spring seat 55 Snap ring 56 Screw Part 61 cover 62 baffle plate 63 flat plate

Claims (3)

Rocker shaft,
A first rocker arm having a distal end linked to the first intake valve or the first exhaust valve and swingably supported by the rocker shaft and driven by a first low lift cam;
A second rocker arm having a distal end provided to be connectable to the first rocker arm and swingably supported by the rocker shaft and driven by a high lift cam having a larger lift than the first low lift cam;
A first roller follower provided on a base end side of the first rocker arm and abutting on the first low lift cam of the camshaft;
A second roller follower provided on a base end side of the second rocker arm and abutting on the high lift cam of the camshaft;
A connection switching mechanism for switching between a connected state and a disconnected state of the second rocker arm with respect to the first rocker arm,
A valve gear for an internal combustion engine, wherein the first roller follower is formed as a sliding roller, and the second roller follower is formed as a needle bearing using a needle roller. Rocker shaft,
A first rocker arm having a distal end linked to the first intake valve or the first exhaust valve and swingably supported by the rocker shaft and driven by a first low lift cam;
A third rocker arm having a distal end linked to a second intake valve or a second exhaust valve and swingably supported by the rocker shaft and driven by a second low lift cam having a smaller lift than the first low lift cam;
A second rocker arm having a distal end provided to be connectable to the first rocker arm and swingably supported by the rocker shaft and driven by a high lift cam having a larger lift than the first low lift cam;
A first roller follower provided on a base end side of the first rocker arm and abutting on the first low lift cam of the camshaft;
A third roller follower provided on a base end side of the third rocker arm and in contact with a second low lift cam of the camshaft;
A second roller follower provided on a base end side of the second rocker arm and abutting on the high lift cam of the camshaft;
A connection switching mechanism that switches between a connected state and a disconnected state of the second rocker arm with respect to the first rocker arm and the third rocker arm,
An internal combustion engine, wherein at least the second roller follower of the first roller follower and the second roller follower is formed as a needle bearing using a needle roller, and the third roller follower is formed as a sliding roller. Valve gear. The valve train of an internal combustion engine according to claim 1 or 2,
A valve gear for an internal combustion engine, wherein the sliding roller is a double ring-shaped sliding roller.

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