JP2017078370A - Variable valve train - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve space saving of a mounting space in a variable valve train for switching a cam profile by sliding of a cam unit in a cam shaft axial direction.SOLUTION: In a rear side end 13b of a front piece 13 of a cam shaft 12, a groove 13a for avoiding an interference with the front side end of a cam unit 40 closest to the front piece 13. So, when the cam unit 40 slides to the side of the front piece 13, the front side end of the cam unit 40 enters the inside of the groove 13a of the front piece 13. Such a construction enables the front piece 13 and the cam unit 40 to partly overlap with each other in the axial direction of the cam shaft 12. Thus, the axial length of the cam shaft 12 can be shortened to achieve space saving of the mounting space.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a variable valve mechanism used in an engine valve system.

  As a variable valve mechanism, a cam unit (cam carrier) provided with a plurality of cams having different cam profiles (cams for driving engine valves) is slidably arranged on a cam shaft in the axial direction. A structure in which the cam profile is switched by sliding is known (for example, see Patent Document 1).

  In such a variable valve mechanism, the cam profile is switched by providing a spiral guide groove on the outer periphery of the cam unit, inserting an engagement element (solenoid pin) of the servo mechanism into the guide groove, and a camshaft (cam This is done by sliding the cam unit in the axial direction using the rotational force of the unit.

Japanese translation of PCT publication 2010-520395

  By the way, in the variable valve mechanism having the above-described structure, the cam profile is switched by sliding the cam unit in the camshaft axial direction. Installation space including it is essential. Here, in order to make the engine compact, a cylinder head having a small bore pitch and a small valve pitch is employed. In such an engine, since the distance between the cam that drives the intake valve on the front side of the first cylinder closest to the front piece (piece integrally formed at the front end of the camshaft) and the front piece is short, the structure described above is used. When the variable valve mechanism is mounted, when the cam unit of the first cylinder slides toward the front piece, the cam unit may interfere with the front piece.

  The present invention has been made to solve such a problem, and includes a cam unit having a plurality of cams having different cam profiles, and a variable motion for switching the cam profile by sliding the cam unit in the camshaft axial direction. An object of the valve mechanism is to reduce the mounting space.

  The present invention is a valve operating mechanism mounted on a multi-cylinder engine having a camshaft in which a front piece is integrally formed, and is provided to be slidable in the axial direction with respect to the camshaft, and cam profiles are mutually connected. The present invention is directed to a variable valve mechanism that includes a cam unit in which a plurality of different cams are arranged along the axial direction of the camshaft, and that switches a cam used to open and close an engine valve by sliding the cam unit. In such a variable valve mechanism, a groove for avoiding interference with the front end of the cam unit closest to the front piece is formed in the rear end of the front piece of the camshaft. A technical feature is that when the cam unit slides to the front piece side, the front end of the cam unit enters the groove of the front piece.

  According to the present invention, when the cam unit closest to the front piece slides toward the front piece side, the front end of the cam unit enters the groove of the front piece. A part can be overlapped in the axial direction of the camshaft. As a result, the axial length of the camshaft can be shortened, and a space saving of the mounting space can be achieved. Moreover, the weight reduction of the camshaft assembly can also be achieved.

  According to the present invention, in a variable valve mechanism that includes a cam unit having a plurality of cams having different cam profiles and switches the cam profile by sliding the cam unit in the camshaft axial direction, the mounting space can be saved. be able to. As a result, the variable valve mechanism can be mounted on a cylinder head having a small bore pitch or valve pitch.

It is a schematic block diagram of the valve system of the engine carrying the variable valve mechanism of this invention. It is a schematic block diagram of embodiment of a variable valve mechanism (cam switching mechanism). It is AA sectional drawing of FIG. It is sectional drawing which shows the principal part structure of the variable valve mechanism of FIG. It is sectional drawing which shows the principal part structure of the variable valve mechanism of FIG. It is BB sectional drawing of FIG. FIG. 7 is a view corresponding to FIG. 6 illustrating a modification of the embodiment.

  Embodiments in which the present invention is applied to a valve train of an engine will be described below with reference to the drawings. The engine 1 shown in FIG. 1 is an inline 4-cylinder gasoline engine, and the first to fourth cylinders 3 (# 1 to # 4) are in the longitudinal direction of a cylinder block (not shown), that is, the engine 1. Are aligned in the front-rear direction (X direction).

-Outline of valve system-
As shown in FIG. 1, a cam housing 2 is disposed in an upper portion (cylinder head) of the engine 1, and a valve operating system of an intake valve 10 and an exhaust valve 11 is accommodated therein. That is, as indicated by broken lines in FIG. 1, two intake valves 10 and two exhaust valves 11 are respectively provided in the four cylinders 3 arranged in a line in the front-rear direction (X direction) of the engine 1. They are driven by an intake camshaft 12 and an exhaust camshaft 14, respectively.

  A front piece 13 (see also FIG. 2 and the like) is integrally provided at the front end (end portion on the Fr side) of the intake camshaft 12, and a VVT capable of continuously changing the valve timing. (Variable Valve Timing) mechanism 16 is assembled. A front piece 15 is also integrally provided at the front end (end portion on the Fr side) of the exhaust camshaft 14, and the VVT mechanism 16 is assembled to the front piece 15. Further, the intake camshaft 12 is provided with a variable valve mechanism (cam switching mechanism) 4 for switching the cams 41 and 42 (see FIG. 2) for driving the intake valve 10 and changing the lift characteristics for each cylinder 3. Is provided.

-Variable valve mechanism-
Next, the variable valve mechanism will be described with reference to FIGS. FIG. 2 shows the structure of the variable valve mechanism 4 of the first cylinder 3 (# 1) that is closest to the front piece 13 of the intake camshaft 12 among the four cylinders 3.

  The variable valve mechanism 4 includes a cam unit 40 provided on the intake camshaft 12, two electromagnetic solenoids 50 and 50, and the like. The two electromagnetic solenoids 50 and 50 are supported (fixed) on the cam housing 2 (see FIG. 1) by a stay (not shown), for example.

  The cam unit 40 is a cylindrical member and is externally mounted on the intake camshaft 12. As shown in FIG. 3, spline inner teeth 40 a are formed on the inner periphery of the cam unit 40. The spline inner teeth 40a of the cam unit 40 mesh with spline outer teeth 12a formed on the outer periphery of the intake camshaft 12, so that the cam unit 40 can rotate integrally with the intake camshaft 12. The cam unit 40 is slidable in the axial direction (X direction) of the intake camshaft 12 by the spline fitting. The position of the cam unit 40 is switched to a position for selecting one of two cams 41 and cams 42 described later.

  At both ends of the cam unit 40, two cams 41 and 42 having different cam profiles are provided corresponding to the intake valves 10, respectively. One of the two cams 41 or 42 drives the intake valve 10 via the rocker arm 17. The two cams 41 and 42 are provided adjacent to each other in the axial direction of the intake camshaft 12, the left side (Fr side) cam 41 in FIG. 2 is a zero lift cam (stop cam), and the right side in FIG. The cam 42 on the Rr side is a high lift cam.

  A spiral groove (guide groove) 43 is formed on the outer periphery of the central portion of the cam unit 40. The spiral groove 43 includes a left-handed groove 43a and a right-handed groove 43b formed so as to extend in the circumferential direction on the outer periphery of the cam unit 40, and a joining groove 43c where the two grooves 43a and 43b merge. And it is formed in Y shape as a whole. Two electromagnetic solenoids 50, 50 are arranged so as to face the spiral groove 43 having such a shape. When each electromagnetic solenoid 50 is turned on, the solenoid pin 51 advances, and the advanced solenoid pin 51 is inserted into the spiral groove 43.

  When the cam unit 40 is slid to the right side (Rr side) in FIG. 2, the solenoid pin 51 of one electromagnetic solenoid 50 is inserted into the left-handed groove 43 a of the spiral groove 43. When the solenoid pin 51 is inserted into the left-handed groove 43a, the cam unit 40 slides to the right side (Rr side) in FIGS. 2 and 4 by the rotation of the cam unit 40 accompanying the rotation of the intake camshaft 12. By this sliding, the cam unit 40 is disposed at the zero lift position, and the Fr side cam 41 (zero lift cam) comes into contact with the rocker arm 17 of the intake valve 10.

  On the other hand, when the cam unit 40 is slid to the left side (Fr side) in FIG. 2, the solenoid pin 51 of the other solenoid 50 is inserted into the right hand groove 43 b of the spiral groove 43. When inserted into the right-handed groove 43b, the cam unit 40 slides to the left side (Fr side: front piece 13 side) in FIGS. By this slide, the cam unit 40 is disposed at the high lift position, and the cam with which the rocker arm 17 of the intake valve 10 abuts is switched to the Rr side cam 42 (high lift cam) (cam profile is switched).

-Lock mechanism-
In the present embodiment, a lock mechanism 44 for holding the position of the cam unit 40 when the cam profile is switched by sliding the cam unit 40 is provided.

  As shown in FIGS. 4 and 5, the lock mechanism 44 is camped by annular lock ball grooves 44 a and 44 b formed on the inner peripheral surface of the cam unit 40 and a coil spring 44 d built in the intake camshaft 12. Lock balls 44c and 44c urged toward the inner surface of the unit 40 are provided.

  As shown in FIG. 4, when the cam unit 40 is in the zero lift position, the lock balls 44c and 44c are fitted in the lock ball groove 44a on the left side (Fr side) in the figure to maintain the position of the cam unit 40. The On the other hand, as shown in FIG. 5, when the cam unit 40 is in the high lift position, the lock balls 44c and 44c are engaged with the lock ball groove 44b on the right side (Rr side) in the figure to maintain the position of the cam unit 40. Is done.

-Feature part-
Next, the characteristic part of this embodiment is demonstrated.

  First, in the variable valve mechanism 4 having a structure in which the cam profile is switched by sliding the cam unit 40 in the axial direction (X direction), the amount of sliding in the axial direction of the intake camshaft 12 is a requirement for mounting on the engine 1. Installation space including is essential.

  Here, in order to make the engine compact, a cylinder head having a small bore pitch and a small valve pitch is employed. In such an engine, the distance between the cam that drives the intake valve on the front side (Fr side) of the first cylinder 3 (# 1) closest to the front piece and the front piece is short. Therefore, when the variable valve mechanism 4 having the above-described structure is mounted, when the cam unit 40 of the first cylinder 3 (# 1) slides toward the Fr side (front piece side), the cam unit 40 is There is a risk of interference with the piece 13.

  In the present embodiment, in order to solve such a problem, as shown in FIGS. 4 to 6, the end portion 13 b on the Rr side of the front piece 13 of the intake camshaft 12 is closest to the front piece 13. Fr side end portion (cylindrical end portion) of the cam 41 at a position corresponding to the Fr side end portion of the Fr side cam 41 (zero lift cam) of the cam unit 40 arranged in the first cylinder 3 (# 1). It is characterized in that a ring-shaped groove 13a for avoiding interference with the groove 13a is formed. The groove width of the ring-shaped groove 13 a is larger than the thickness of the front end portion of the cam 41 on the Fr side of the cam unit 40. Further, the depth of the groove 13a (the depth in the axial direction (X direction)) is deeper than the amount of penetration of the end portion of the cam 41 into the groove 13a by the sliding of the cam unit 40.

  By providing the front piece 13 with the interference avoiding groove 13a in this way, when the cam unit 40 of the first cylinder 3 (# 1) slides toward the Fr side (front piece 13 side). 5, the Fr side end of the cam unit 40 (the end of the Fr side cam 41) is in the groove 13a of the front piece 13, and the Fr side end of the front piece 13 and the cam unit 40 is as shown in FIG. Therefore, the front piece 13 and a part of the cam unit 40 can overlap in the axial direction (X direction) of the intake camshaft 12. As a result, the axial length of the intake camshaft 12 can be shortened, and the mounting space can be saved. Also, the weight reduction of the intake camshaft assembly can be achieved.

  Since the space saving of the mounting can be achieved in this way, the variable valve mechanism 4 of the present embodiment is the cylinder head with the above-described compactness, that is, the bore pitch and the valve pitch are small and closest to the front piece. The first cylinder 3 (# 1) can be mounted on a cylinder head having a short distance between the intake valve cam on the front side (Fr side) and the front piece.

-Other embodiments-
In addition, embodiment disclosed this time is an illustration in all the points, Comprising: It does not become a basis of limited interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description of the scope of claims. Further, the technical scope of the present invention includes all modifications within the scope and meaning equivalent to the scope of the claims.

  For example, in the above embodiment, the example of the variable valve mechanism including the cam unit 40 in which the zero lift cam 41 and the high lift cam 42 are formed has been described, but the present invention is not limited thereto.

  For example, the present invention can be applied to a variable valve mechanism including a cam unit in which a low lift cam 141 (see FIG. 7) is formed on the Fr side and a high lift cam is formed on the Rr side. In this case, as shown in FIG. 7, the front end portion of the low lift cam 141 is located at the Rr side end portion of the front piece 113 at a position corresponding to the front end portion of the low lift cam 141 on the Fr side of the cam unit. A groove 113a for avoiding interference with the front end of the low lift cam 141 is formed in a shape corresponding to the front end. Thus, by forming the groove 113a (groove for avoiding interference) of the front piece 113 in a shape corresponding to the front end of the low lift cam 141, the thickness of the broken line portion shown in FIG. The strength against the cam load can be ensured.

  In the above embodiment, the cam switching mechanism for switching the lift characteristic of the intake valve 10 in the DOHC type valve system of the engine 1 has been described. However, the present invention is not limited to this, and the lift characteristic of the exhaust valve 11 is not limited thereto. The present invention can also be applied to a cam switching mechanism for switching between. Further, the present invention is not limited to a DOHC type valve system, and the present invention can be applied to, for example, an SOHC type valve system.

  The present invention is effective for a variable valve mechanism having a structure in which a cam unit provided with a plurality of cams having different cam profiles is slidable in the axial direction with respect to a camshaft, and the cam profile is switched by sliding of the cam unit. Can be used.

1 Engine 3 Cylinder 4 Variable valve mechanism (Cam switching mechanism)
40 Cam unit 41, 42 Cam 43 Spiral groove 50 Electromagnetic solenoid 51 Solenoid pin 10 Intake valve (engine valve)
11 Exhaust valve (engine valve)
12 Intake camshaft 13 Front piece 13a Groove (for interference avoidance)
13b Rear end of front piece

Claims (1)

A valve operating mechanism mounted on a multi-cylinder engine having a camshaft integrally formed with a front piece, wherein the camshaft is slidable in the axial direction with respect to the camshaft and has a plurality of cam profiles different from each other In a variable valve mechanism that includes a cam unit disposed along the axial direction of the camshaft, and switches a cam used to open and close an engine valve by sliding the cam unit.
A groove for avoiding interference with the front end of the cam unit closest to the front piece is formed at the rear end of the front piece of the camshaft, and the cam unit slides toward the front piece. When this is done, the variable valve mechanism is configured so that the front end of the cam unit enters the groove of the front piece.

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