JP2004353547A - Variable valve system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent dispersion of the valve lift between cylinders by preventing the inclination of a control shaft when assembling an actuator with the control shaft. <P>SOLUTION: A variable valve system comprises a drive cam fixed to an outer circumference of a drive shaft 3, and a rocker arm 13 with one end part thereof connected to the drive cam via a link arm 14. The rocker arm is supported by an outer circumferential surface of an offset control cam fixed to an outer circumference of a control shaft 17 in a rocking manner, and rocking cams 7 and 7 to drive an intake valve are connected to the other end part. There are provided an engagement groove 39 notched in an end part 17a of the control shaft along the radial direction and an engagement projecting part 40 facing the engagement groove 39 and formed on an end part of a shaft part 26 of an actuator 22. The engagement projecting part is engaged with the engagement groove in the radial direction, and a moving means 38 to permit free movement of the shaft part in the upper and lower radial directions of the control shaft is provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a variable valve apparatus for an internal combustion engine that can vary at least a valve lift of an intake valve or an exhaust valve as an engine valve according to an engine operating state.
[0002]
[Prior art]
As this kind of conventional variable valve device, there is one described in Patent Document 1 filed by the present applicant earlier.
[0003]
In brief, this variable valve apparatus is applied to the intake valve side, and the axis is eccentric from the axis of the drive shaft on the outer periphery of the drive shaft that rotates in synchronization with the rotation of the crankshaft. A drive cam is provided, and the rotational force of the drive cam is transmitted through a multi-node link transmission mechanism, and the cam surface slides on the upper surface of the valve lifter at the upper end of the intake valve so that the intake valve is moved. It has a swing cam that opens to oppose the spring force of the valve spring.
[0004]
The transmission mechanism includes a rocker arm disposed above the swing cam and swingably supported by the control shaft, an annular end fitted to the outer peripheral surface of the drive cam, and the other end connected to one end of the rocker arm. A link arm rotatably connected to the portion via a pin, and one end rotatably connected to the other end of the rocker arm via a pin, and the other end via a pin to a cam nose portion of the swing cam. And a link rod that is rotatably connected to the link rod.
[0005]
The control shaft is rotatably supported by a bearing provided at the upper end of the cylinder head, and a control cam whose axis is eccentric by a predetermined amount from the axis of the control shaft is fixed to an outer peripheral surface thereof. Have been.
[0006]
Then, the pivot position of the rocker arm is changed by changing the rotation position of the control cam via the control shaft by an actuator including an electric motor and a screw transmission means according to the engine operating state, thereby changing the swing cam. By changing the rolling contact position of the cam surface with respect to the upper surface of the valve lifter, the valve lift amount of the intake valve is variably controlled according to the engine operating state.
[0007]
[Patent Document 1]
JP 2002138716 A
[Problems to be solved by the invention]
By the way, the above-described variable valve apparatus for an internal combustion engine requires many components such as the transmission mechanism using a multi-joint link mechanism, and each component is caused by a manufacturing error or an assembly error. Variations in the valve lift of the intake valve are likely to occur, and in particular, variations in the valve lift between cylinders are likely to occur.
[0009]
Therefore, after assembling these components such as the transmission mechanism on the cylinder head by mounting it on the bearing with the valve spring acting on the drive shaft and control shaft in the radial direction on the cylinder head, and then using the adjustment mechanism, The valve lift of each intake valve is adjusted by changing the length of the link rod.
[0010]
However, when the actuator is assembled to the control shaft after the adjustment of the valve lift, the clearance between the outer peripheral surface of the control shaft and the inner peripheral surface of the bearing is different from the mounting clearance between the control shaft and the actuator. Further, since the spring force of the valve spring acts on the control shaft in the radial direction in advance, there is a possibility that the control shaft may be inclined by the different clearance by the spring force of the valve spring. . As a result, at the time of assembling (connecting) the control shaft and the actuator, which is the final assembling operation, there is a possibility that the valve lift amounts of the respective intake valves may vary.
[0011]
Even if the variation in the valve lift amount is corrected in consideration of the tilt of the control shaft, there is also an error in mounting the actuator, so that the valve lift amount shifts every time the actuator is attached or detached, for example, for maintenance. There is a risk that it will.
[0012]
[Means for Solving the Problems]
The present invention has been devised in view of the technical problem of the conventional variable valve operating device, and the invention according to claim 1 controls the actuator when assembling the control shaft and the actuator. A moving means for allowing free movement in the radial direction of the shaft is provided, and a rotational driving force from the actuator is provided to be transmitted to the control shaft via the moving means.
[0013]
Therefore, according to the present invention, when the actuator is connected (assembled) to the control shaft after assembling the components, if the moving means is displaced in the radial direction of the axis between the two components, the control shaft is displaced. For example, the shaft portion of the actuator moves in the radial direction to absorb the radial displacement. For this reason, the occurrence of the tilt of the control axis can be prevented.
[0014]
As a result, it is possible to prevent the valve lift amount of the engine valve, particularly the minute valve lift amount at the time of the minimum lift control, from varying among the cylinders.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a variable valve device for an internal combustion engine according to the present invention will be described in detail with reference to the drawings.
[0016]
In this embodiment, the variable valve device is applied to the intake valve side, as in the related art, and is provided with two intake valves per cylinder, and the valve lift amount of the intake valve is variable according to the engine operating state. It is supposed to.
[0017]
That is, as shown in FIGS. 1, 3 and 4, a variable valve train in this embodiment comprises a pair of intake valves 2, 2 slidably provided on a cylinder head 1 via a valve guide (not shown). An internal hollow drive shaft 3 arranged in the front-rear direction of the engine, a camshaft 4 arranged for each cylinder and rotatably supported coaxially on the outer peripheral surface of the drive shaft 3, A drive cam 5 fixed at a predetermined position on the shaft 3 and valve lifters 6 and 6 provided integrally at both ends of the camshaft 4 and disposed at the upper ends of the intake valves 2 and 2, respectively. A pair of oscillating cams 7, 7 which are in contact with each other to open the respective intake valves 2, 2, and are linked between the driving cam 5 and the oscillating cams 7, 7 so that the rotating force of the driving cam 5 is A transmission mechanism 8 for transmitting the oscillating power (valve opening force) of the transmission mechanism 7; And a control mechanism 9 that.
[0018]
The intake valves 2, 2 are moved in the closing direction by valve springs 10, 10 elastically mounted between the bottom of a substantially cylindrical bore housed in the upper end of the cylinder head 1 and a spring retainer at the upper end of the valve stem. Being energized.
[0019]
The drive shaft 3 is arranged along the front-rear direction of the engine, and both ends are rotatably supported by bearings 11 provided on the upper part of the cylinder head 1 and are provided at one end with an unshown one. The rotational force is transmitted from the crankshaft of the engine via a driven sprocket, a timing chain wound around the driven sprocket, and the like.
[0020]
Each of the camshafts 4 is formed in a substantially cylindrical shape along the axial direction of the drive shaft 3, and a shaft hole rotatably supported on the outer peripheral surface of the drive shaft 3 is formed in the inner axial direction. At the same time, a large-diameter cylindrical journal portion 4 a formed at the center position is rotatably supported by a cam bearing 12.
[0021]
The drive cam 5 is formed in a substantially disk shape, and as shown in FIG. 3, a fixing tubular portion 5a is integrally provided on one side thereof, and the tubular portion 5a is Are fixed integrally to the outer periphery of the drive shaft 3 via fixing pins 16 at predetermined positions in the axial direction, and the outer peripheral surface 5b is formed in an eccentric cam profile so that the axis Y is Is offset from the axis X by a predetermined amount in the radial direction.
[0022]
As shown in FIG. 3, each of the swing cams 7 has substantially the same shape as a raindrop, and the base end thereof swings about the axis X of the drive shaft 3 via the camshaft 4. A cam surface 7a is formed on the lower surface of the swing cam 7, respectively, a base circular surface on the base end side, and a ramp surface extending in an arc shape from the base circular surface to the cam nose portions 7b, 7b. A lift surface is formed from the ramp surface to a top surface of a maximum lift provided on the distal end side of the cam nose portion 7b. The base circle surface and the ramp surface, the lift surface, and the top surface form a swing cam 7 swinging. The upper surface of each valve lifter 6 comes into contact with a predetermined position in accordance with the moving position.
[0023]
On the cam nose portion 7b side of the swing cam 7, a pin hole through which a pin 21 connected to the other end portion 15b of the link rod 15 described later is inserted is formed to penetrate in both side directions.
[0024]
As shown in FIG. 3, the transmission mechanism 8 includes a rocker arm 13 disposed above the drive shaft 3, a link arm 14 that links one end 13 a of the rocker arm 13 and the drive cam 5, A link rod 15 is provided for linking the end portion 13b and the cam nose portion 7b of the one swing cam 7.
[0025]
The rocker arm 13 has a support hole 13c formed in the center of the cylindrical base portion so as to penetrate from the lateral direction, and is swingably supported by a control cam 18 to be described later via the support hole 13c. One end 13a extending from the outer end of the cylindrical base has a pin 19 integrally protruding from the side of the tip, while the other end 13a extending from the inner end of the cylindrical base. 13b is formed with a pin hole into which a pin 20 which is a first pivot supporting portion connected to one end 15a of the link rod 15 is fitted inside the distal end portion.
[0026]
The link arm 14 includes a relatively large-diameter annular portion 14a and a protruding end 14b protruding at a predetermined position on an outer peripheral surface of the annular portion 14a. A fitting hole 14c rotatably fitted to the outer peripheral surface 5b of the driving cam 5 is formed, while a pin hole 14d through which the pin 19 is rotatably inserted is formed through the protruding end 14b.
[0027]
The link rod 15 is formed integrally by press molding, has a central portion formed in a substantially U-shaped cross section, and has an inner side bent in a substantially U-shaped shape in order to achieve compactness. Both ends 15a and 15b are rotatably connected to the other end 13b of the rocker arm 13 and the cam nose 7b of the swing cam 7 via the pins 20 and 21.
[0028]
As shown in FIGS. 1, 3, and 4, the control mechanism 9 includes a control shaft 17 disposed above the drive shaft 3 and a rocker arm 13 which is integrally fixed to the outer periphery of the control shaft 17. A control cam 18 serving as a fulcrum and an actuator 22 for controlling the rotation of the control shaft 17 are provided.
[0029]
The control shaft 17 is disposed in the engine front-rear direction in parallel with the drive shaft 3, and is rotatably supported by a bracket 11 a provided at the upper end of the bearing 11 shared with the drive shaft 3. On the other hand, the control cam 18 has a cylindrical shape, and the axial center position is deviated from the axial center of the control shaft 17 by a predetermined amount by the thickness portion.
[0030]
As shown in FIGS. 1 and 5, the actuator 22 includes a housing 23 fixed to the rear end of the cylinder head 1, and an electric motor 24 serving as a rotational force applying mechanism fixed to one end of the housing 23. And a screw transmission means 25 provided inside the housing 23 for transmitting the rotational driving force of the electric motor 24 to the control shaft 17.
[0031]
The housing 23 has a cylindrical portion 23 a disposed substantially perpendicular to the axial direction of the control shaft 17, and projects upward at the center of the upper end of the cylindrical portion 23 a to internally include one end of the control shaft 17. The bulging portion 23b faces the shaft portion 26 connected to the shaft 17a, and the side wall 23c closes one side of the cylindrical portion 23a and the bulging portion 23b.
[0032]
The electric motor 24 is constituted by a proportional type DC motor, and a distal end of a substantially cylindrical motor casing is fixed to an opening at one end of the cylindrical portion 23a by a bolt 27 from an axial direction.
[0033]
The electric motor 24 is driven by a control signal from a controller (not shown) that detects the operating state of the engine. The controller includes various sensors such as a crank angle sensor that detects the engine speed, an air flow meter that detects the intake air amount, a water temperature sensor that detects the engine water temperature, and a potentiometer that detects the rotational position of the control shaft 17. Is fed back to detect the current engine operating state by calculation or the like, and a control signal is output to the electric motor 24.
[0034]
As shown in FIG. 5, the screw transmission means 25 includes a screw shaft 28, which is an output shaft disposed substantially coaxially with the output shaft 24a of the electric motor 24 in the cylindrical portion 23a of the housing 23, and the screw shaft 28. A screw nut 29 screwed to the outer circumference of the shaft 28; a link arm 30 fixed to the outer circumference of one end of the shaft portion 26 in the housing 23; and a link member 31 for linking the link arm 30 and the screw nut 29. The link arm 30 and the link member 31 constitute a link mechanism.
[0035]
The screw shaft 28 has a male screw portion 28c continuously formed on the entire outer peripheral surface except for both end portions, and has two ball bearings each having one end portion facing the one end opening portion and the other end opening portion of the cylindrical portion 23a. It is rotatably supported by 33 and 34.
[0036]
The one-side ball bearing 33 has an end portion 28a of the screw shaft 28 press-fitted or fixed or fitted on the inner ring, and an outer ring formed in the annular groove 23d formed inside the one end opening portion from the inner axial direction. Press-fit fixed or fitted.
[0037]
The other-side ball bearing 34 is tightly held by a nut 35 as an axial fixing means in which the inner ring is screwed to the tip of the other end 28b of the screw shaft 28, and the outer ring has the other end opening. It is clamped and held in the housing 23 by a bowl-shaped cap nut 36 which closes in a liquid-tight manner.
[0038]
The screw shaft 28 has a small-diameter shaft at one end 28a and a small-diameter portion at the distal end of the output shaft 24a of the electric motor 24, which are serration-coupled by a connecting member 37 so as to be coaxially movable in the axial direction.
[0039]
The linking arm 30 is formed in a substantially raindrop shape, and a large-diameter base is positioned in the circumferential direction at one end 26a of the shaft 26 by the locating pin 42, and is bolted from the axial direction to the one end 26a by the bolt 43. Fixed. In addition, a slit is formed at the center position in the width direction of the tapered tip portion 30a, and two pin holes are formed in the tip portion 30a continuously penetrating along the control shaft 17 direction. I have. Therefore, the axis Z of the pin hole is deviated from the axis P1 of the shaft portion 26.
[0040]
The link member 31 is formed in a substantially Y-shape, and includes a flat plate-shaped one end portion 31a and a forked-shaped other end portion 31b, 31b. The one end portion 31a is inserted through a slit of the link arm 30. Then, it is rotatably connected to the distal end portion 30b of the link arm 30 by the pin hole and the pin 32 penetrating the own pin hole. On the other hand, the other ends 31 b of the forked shape are disposed on both sides of the screw nut 29, and two pin shafts 33 respectively inserted into the pin holes formed to face each other and the pin holes of the screw nut 29. , 33 and rotatably connected to the screw nut 29. Both ends of the pin 32 are fixed to both pin holes of the link arm 30, and a center portion of the pin 32 is slidable in the pin hole of the link member 31. On the other hand, each of the pin shafts 33, 33 has its outer end press-fitted into a pin hole of each link member 31, and its inner end slidable in the pin hole of the screw nut 29.
[0041]
The control shaft 17 and the shaft portion 26 on the side of the actuator 22 have substantially the same outer diameter as shown in FIGS. 1, 3 and 4, and are basically arranged substantially coaxially. A moving means 38 is provided at the opposite ends of the two members 17 and 26 so as to freely move the shaft 26 radially with respect to the radial direction of the control shaft 17.
[0042]
That is, as shown in FIGS. 1 to 4, the moving means 38 includes an engagement groove 39 formed in a diameter direction at an end of the control shaft 17 facing the shaft 26, and a control shaft of the shaft 26. An engaging projection 40 is formed on an end portion facing the opposite end portion 17 and engages with the engaging groove 39.
[0043]
The engagement groove 39 is formed in a substantially rectangular shape in the diameter direction passing through the axis, and the upper and lower ends 35a and 35b are opened in the diameter direction.
[0044]
On the other hand, the engaging convex portion 40 has a rectangular shape whose width is set slightly smaller than the width of the engaging groove 39, and both side surfaces 36 a and 36 b are slidable with respect to the opposing surface of the engaging groove 39. Is formed.
[0045]
In addition, the engagement groove 39 and the engagement protrusion 40 are arranged to be rotated substantially vertically along the minimum lift control of each of the intake valves 2 and 2.
[0046]
Hereinafter, the operation of the present embodiment will be described. First, for example, in a low rotation range of the engine, the rotation torque transmitted to the electric motor 24 by the control signal from the controller is transmitted to the screw shaft 28 and rotates. With this rotation, the screw nut 29 moves from the position shown in FIG. 5 to the maximum rightward position, whereby the control shaft 17 is driven to rotate counterclockwise by the link member 31 and the link arm 30, and The side surface of the distal end portion 30a of the arm 30 abuts against a stopper pin (not shown), and further rotation is restricted.
[0047]
Therefore, the control shaft 17 rotates the control cam 18 in one direction via the shaft portion 26 and the moving means 38, and the shaft center P2 rotates around the shaft center P1 of the control shaft 17 with the same radius. The thick part moves upward away from the drive shaft 3. As a result, the pivot point between the other end 13b of the rocker arm 13 and the link rod 15 moves upward with respect to the drive shaft 3, so that each swing cam 7 is moved via the link rod 15 to the cam nose 7b. The side is forcibly raised.
[0048]
Therefore, when the drive cam 5 rotates and pushes up one end 13 a of the rocker arm 13 via the link arm 14, the valve lift amount is transmitted to the swing cam 7 and the valve lifter 16 via the link rod 15. The lift amount becomes sufficiently small.
[0049]
Therefore, in the low engine speed region of the engine, the valve lift is minimized, so that the opening timing of each intake valve 2 is delayed, and the valve overlap with the exhaust valve is reduced. As a result, improved fuel efficiency and stable rotation of the engine can be obtained.
[0050]
Further, when the engine shifts to the high engine speed region, when the electric motor 24 is further rotated in the reverse direction by the control signal from the controller and the screw shaft 28 is further rotated in the same direction, the screw nut 29 is moved as shown in FIG. As shown in the figure, the movement is largely leftward. At this time, further movement is restricted at the position where the link arm 31 abuts against the stopper pin 41, and further movement of the screw nut 29 is also restricted. Therefore, the control shaft 17 rotates the control cam 33 clockwise from the position shown in FIG. 4, and the shaft center P2 moves downward. For this reason, the rocker arm 13 moves in the direction of the drive shaft 3 in its entirety, and the cam nose portion 7b of the swing cam 7 is pressed downward by the other end portion 13b via the link rod 15 so that the rocker arm 13 Is rotated counterclockwise by a predetermined amount.
[0051]
Therefore, the contact position of the cam surface 7a of the swing cam 7 with respect to the upper surface of the valve lifter 6 moves toward the cam nose 7b (lift side). Therefore, when the drive cam 5 rotates during the opening operation of the intake valve 2 to push up the one end 13a of the rocker arm 13 via the link arm 14, the lift of the valve lifter 6 relative to the valve lifter 6 becomes sufficiently large.
[0052]
Therefore, in such a high rotation region, the valve lift amount is maximized, and the opening timing of each intake valve 2 is advanced and the closing timing is delayed. As a result, the intake charging efficiency is improved, and a sufficient output can be secured.
[0053]
According to this embodiment, after assembling the components, that is, after assembling the components such as the drive shaft 3 and the transmission mechanism 8 to the cylinder head 1 via the bearing 11 and the cam bearing 12, When the position is set to the minimum lift control state and the engaging protrusion 40 of the shaft portion 26 of the actuator 22 is engaged with the engaging groove 39 of the control shaft 17 from the radial direction and connected, the shaft centers of the two 17 and 26 are aligned. If they are displaced from each other in the radial direction, the engaging protrusion 40 moves in the engaging groove 39 in the radial direction by the amount of the displacement and absorbs the displacement. For this reason, since the control shaft 17 is held at a position previously supported by the bearing 11, the occurrence of vertical inclination is reliably prevented.
[0054]
As a result, it is possible to prevent the valve lift amounts of the intake valves 2 and 2, particularly the minute valve lift amounts at the time of the minimum lift control, from varying among the cylinders.
[0055]
Further, in this embodiment, since the moving means 38 has a simple structure including the engaging groove 34 and the engaging convex portion 35, the manufacturing operation is easy and the assembling operation of the two 34, 35 is also easy. .
[0056]
The technical ideas other than the claims that can be grasped from each of the embodiments will be described below.
(B) The moving means includes an engaging groove formed along a diametrical direction at one end of the control shaft or a shaft portion of the actuator which is opposed to the control shaft in the axial direction. 2. The internal combustion engine according to claim 1, further comprising: a two-plane-width engaging portion formed in a diametrical direction at the opposite end of the diametrically engaging portion and radially engaging with the engaging groove. Variable valve gear.
[0057]
According to the present invention, since the structure is simple, the manufacturing operation is easy and the assembling operation is also easy.
(2) The variable valve operating device for an internal combustion engine according to claim 1, wherein the moving means is configured by a clearance of a component of the actuator.
[0058]
According to the present invention, since the moving means is constituted by the clearance of the components of the actuator, the structure can be simplified.
(C) a drive shaft rotatably driven by the crankshaft of the engine, a drive cam fixed to the outer periphery of the drive shaft, and a rocker arm having one end linked to the drive cam via a link arm; The eccentric control cam fixed to the outer circumference of the control shaft is swingably supported on the outer circumferential surface, and the other end is linked to a swing cam for opening and closing the engine valve via a link rod. The swing cam is swingably supported by the drive shaft, and the control shaft and the control cam are rotationally controlled in accordance with the engine operating state, thereby changing the swing fulcrum of the rocker arm, and 2. The valve train for an internal combustion engine according to claim 1, wherein the valve lift amount of the engine valve is changed by changing a sliding position of the engine valve with respect to the engine valve.
[0059]
The present invention is not limited to the configuration of the above-described embodiment. It is also possible to form the engaging groove 39 as the moving means on the shaft portion 26 side and form the engaging convex portion 40 on the control shaft 17 side. It is. Further, the moving means may have a structure like a universal joint connecting the control shaft and the actuator.
[0060]
Further, the present invention can be applied to the exhaust valve side or both valve sides in addition to the intake valve side.
[Brief description of the drawings]
FIG. 1 is a plan view showing a main part of a variable valve apparatus according to one embodiment of the present invention.
FIG. 2 is a perspective view showing a moving unit by separating a control shaft and a shaft portion in a portion A of FIG. 1;
FIG. 3 is a perspective view of a main part of the variable valve apparatus according to the embodiment.
FIG. 4 is a plan view of a main part of the variable valve apparatus according to the embodiment.
FIG. 5 is a cross-sectional view of the actuator provided in the embodiment.
[Explanation of symbols]
1: Cylinder head 2: Intake valve (engine valve)
4 camshaft 7 rocking cam 8 transmission mechanism 9 control mechanism 22 actuator 25 screw transmission means 28 screw shaft 29 screw nut 38 moving means 39 engagement groove 40 engagement protrusion

Claims (1)

A control shaft that is rotatably supported by a bearing provided on the cylinder head, and in which a spring force of a valve spring acts in a radial direction;
An actuator for controlling the rotation of the control shaft,
A variable valve apparatus for an internal combustion engine that changes a valve lift characteristic of an engine valve by controlling rotation of the control shaft by the actuator according to an engine operating state,
At the time of assembling the control shaft and the actuator, a moving means for allowing the actuator to freely move in the radial direction of the control shaft is provided, and a rotational driving force from the actuator is supplied to the control shaft via the moving means. A variable valve train for an internal combustion engine, characterized in that the variable valve train is provided so as to be able to transmit to the internal combustion engine.

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