JP4706867B2 - Variable valve operating device for internal combustion engine - Google Patents

Description

  The present invention relates to a variable valve operating apparatus for an internal combustion engine that continuously controls a valve drive output for driving a valve.

In reciprocating engines (internal combustion engines) installed in automobiles, a variable valve that continuously controls at least the valve characteristics of the intake valve at the cylinder head to prevent engine exhaust and improve pumping loss. The device is mounted.
Many of these variable valve operating apparatuses use a variable valve operating mechanism that continuously changes the valve lift amount in order to adjust the intake air amount. This variable valve mechanism has a structure that outputs the valve drive output in response to the cam displacement of the intake valve cam (rotary cam) formed on the camshaft, and the resulting valve drive output (valve lift amount and opening / closing timing). Or a valve opening period) is used in combination with a structure that continuously varies according to the rotational displacement input from the control shaft.

In many cases, the control shaft operates to drive the intake valve using only the cam profile on the top side of the intake valve cam at the minimum low lift, and at the top of the intake valve cam at the maximum high lift. The cam profile of the intake valve cam is used separately, such as driving the intake valve using the cam profile of the entire area from the base to the base circle, and continuously variable from the low lift range to the high lift range. The structure to be used is used (see, for example, Patent Document 1).
JP 2005-299536 A

By the way, the cam of the camshaft usually has a cam profile of a valve lift curve that defines the whole of the up section a and the down section b in consideration of a specific required operation of the vehicle as shown in FIG. .
However, an engine equipped with a variable valve device uses a variable valve device instead of a throttle valve. For this reason, the variable valve operating system is also required to have various performances obtained with the throttle valve. Specifically, an engine that controls the amount of intake air with a throttle valve uses a throttle valve, so that when the vehicle is traveling in an urban area (load: small), low / medium load is used to ensure stable performance. The engine output was made to follow the change of the engine quickly, and the engine output was increased as much as possible when driving at high speed and mountain road (load: high).

  However, a variable valve system using an intake valve cam with a cam profile similar to the normal one can only use different parts of the cam profile of the cam considering specific required operation, so low lift during low / medium load operation High responsiveness when being controlled at high speeds was not obtained, and sufficient engine output characteristics were not obtained when controlled at high lift during high load operation.

  Accordingly, an object of the present invention is to provide a variable valve operating apparatus for an internal combustion engine that can achieve both high response performance during low / medium load operation of the vehicle and high output performance during high load operation of the vehicle. It is in.

In order to achieve the above object, the invention according to claim 1 receives a camshaft having an intake valve cam and an intake valve cam, outputs a valve drive output, and outputs the valve drive output to the intake valve. A variable valve mechanism that continuously and variably controls from a low lift range to a high lift range by using different parts of the same cam profile for a cam, valve closing characteristics when controlled to a low lift range, and a high lift range Valve closing characteristic changing means for changing the valve closing characteristic when controlled to the required operating characteristic of the vehicle, and the valve closing characteristic changing means is a cam profile that forms a descending section of the intake valve cam. The gradient of the low lift region used at the valve closing timing at the time of low lift is A, and the gradient of the high lift region used at the valve closing timing at the time of the high lift is B, the gradients A and B are A <B In The slope A of the low lift region is set by the cam profile of the descending section where the valve is closed at the timing before the piston of the intake stroke of the internal combustion engine reaches the bottom dead center, and the slope B of the high lift region is Set in the cam profile of the descending section where the valve is closed at the timing after the piston of the intake stroke of the internal combustion engine passes the bottom dead center, and is controlled to a higher lift range than the valve closing speed when controlled to the low lift range It was decided to increase the valve closing speed when it was done .
With this configuration, it is possible to obtain appropriate valve closing characteristics that match the required driving characteristics of the vehicle when the valve is closed during low lift or during high lift.

  Preferably, the valve closing characteristic is the valve closing speed, and the valve closing at the time of low lift is performed at the closing timing of a slow valve closing speed suitable for low / medium load operation, and the valve closing at the time of high lift is high. It can be done at the closing timing of fast closing speed suitable for load operation. The actual valve lift can be obtained by combining the lever ratios of a plurality of cams and rocker arms, but it is desirable to set the valve closing characteristics first with a cam that rotates in synchronization with the crank. Here, the valve closing speed indicates a valve speed in a lift region equal to or less than 1/3 of the maximum valve lift including the time when the valve lift is lowered and the valve seat is seated.

According to the first aspect of the invention, when controlled to a low lift, the valve can be closed with a valve closing characteristic suitable for low / medium load operation, and the variable responsiveness is enhanced. When controlled to a high lift, the valve can be closed with a valve closing characteristic suitable for high-load operation, the output is increased, and the valve lift change is optimized.
In addition , by increasing the valve closing speed when controlled to a higher lift range than the valve closing speed when controlled to a lower lift range, the engine output is affected by changes in low and medium loads during low lift operation. The engine output can be increased by increasing the valve closing speed during operation in a high lift range. Therefore, it is possible to ensure both high response performance during low / medium load operation of the vehicle and high output performance during high load operation of the vehicle.

Moreover, simply by setting the slope of each section of the cam profile of the down section of the cam intake valve (inclination) in the low lift region and the high lift region Ki out changing the valve closing speed, with easy single structure In addition, high responsiveness during low lift operation and high output performance during high lift operation can be improved.

Furthermore , by simply changing the slope of the cam profile in the descending section of the intake valve cam based on the point corresponding to the bottom dead center of the piston, high response during low lift operation and high output during high lift operation are easily achieved. Performance can be ensured .

The present invention will be described below based on the first embodiment shown in FIGS.
1 is a perspective view of a main body of an internal combustion engine, for example, an in-line four-cylinder reciprocating gasoline engine, FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIG. 3 is a rocker cover and timing chain cover in FIG. 4 is an exploded perspective view with the valve system in FIG. 3 removed, FIG. 5 is a cross-sectional view of the variable valve system along the line BB in FIG. 3, and FIG. 7 is a cross-sectional view of the variable valve operating device along line CC in FIG. 3, FIG. 7 is a valve lift performance diagram, FIG. 8 is a cam valve lift curve diagram, and FIGS. 9 to 12 are parts of the variable valve operating device. FIG.

In FIG. 1, 1 is a cylinder block constituting the engine body, 2 is a cylinder head mounted on the cylinder block 1, 3 is a rocker cover that also covers the cylinder head 2, and 4 is a lower portion of the cylinder block 1. 1 is a timing chain cover provided at the front of the cylinder block 1.
As shown in FIG. 5, the cylinder block 1 is formed with four cylinders 6 (only a part of which is shown) along the longitudinal direction of the engine. In these cylinders 6, pistons 7 are housed so as to be reciprocally movable. These pistons 7 are connected to a crankshaft 9 disposed in the front-rear direction of the cylinder block 1 via connecting rods 8 and crankpins 9a, and the reciprocating motion transmitted from the pistons 7 is converted into rotational motions to the crankshaft 9. It is trying to output.

  As shown in FIG. 5, combustion chambers 11 are formed on the lower surface of the cylinder head 2 following the four cylinders 6. A pair of intake ports 12 and a pair of exhaust ports 13 (both only one side is shown) are formed on both sides of the combustion chamber 11. The upper center of the cylinder head 2 is recessed in the front-rear direction. And the both sides of the recessed part 2a have protruded to the side, respectively. On both sides of the combustion chamber 11, an intake valve 14 that opens and closes the intake port 12 and an exhaust valve 15 that opens and closes the exhaust port 13 are provided for each cylinder 6. The intake valve 14 and the exhaust valve 15 are both normally closed types that are urged in a closing direction by a valve spring 16.

  As shown in FIGS. 2 to 6, a variable valve operating device 20 composed of a SOHC valve operating mechanism is mounted in the recess 2 a formed in the upper part of the cylinder head 2. The variable valve gear 20 is housed in the rocker cover 3. The variable valve operating device 20 includes a camshaft 26, a variable valve mechanism 21 that continuously changes the valve characteristics of the intake valve 14, and a rocker arm mechanism 22 that opens and closes the exhaust valve 15 uniquely. A structure that is integrated into a unit is used.

  1 to 6, reference numeral 25 denotes a holding member, 26 denotes a camshaft, 27 denotes an exhaust rocker shaft, 28 denotes a control shaft that also serves as an intake rocker shaft, and 29 denotes a support shaft. is there. Each of the shafts 26 to 29 is formed of a shaft member that extends in the front-rear direction of the engine. Of these, as shown in a part of FIG. 5, the camshaft 26 is arranged on each side of a cam group, for example, an intake cam 26 a (corresponding to the cam of the present application, an intake valve cam), for each cylinder. Three cams such as a pair of exhaust cams 26b (only part of which are shown in FIG. 5) are formed.

  The holding member 25 is disposed at each point on the upper part of the cylinder head 2, for example, at the frontmost part, between the cylinders, and at the rearmost part of the cylinder row. As shown in FIG. 6, the holding member 25 includes a combination of a holder portion 32 and a cap portion 33 that is assembled to the lower end portion of the holder portion 32. The camshaft 26 is sandwiched between a journal surface formed on the lower end surface of each holder portion 32 and a journal surface formed on the upper surface of the cap portion 33 and is rotatably supported. The control shaft 28 is rotatably supported on the intake side (one side in the width direction) of the middle stage of each holder portion 32. The exhaust rocker shaft 27 is fixed on the exhaust side (the other side in the width direction) opposite to the middle control shaft 28 of each holder portion 32. Further, the support shaft 29 is fixed at the upper part of each holder portion 32. As shown in FIG. 6, a pair of fixed seats 34 are formed on both sides of each holder portion 32 at positions near the exhaust rocker shaft 27 and the control shaft 28. With this structure, a frame structure that can be mounted on the cylinder head 2 is formed.

In the same frame, a variable valve mechanism 21 and a rocker arm mechanism 22 are assembled for each cylinder. For example, as shown in FIG. 5, the variable valve mechanism 21 has a structure in which a rocker arm 40, a swing cam 50, and a center rocker arm 60 are combined.
That is, as shown in FIG. 3 and FIG. 4, the rocker arm 40 is an arm member divided into two parts. As shown in FIG. 5, the central portion of the arm member is rotatably supported by the control shaft 28, and an adjustment screw portion 41 provided at the distal end portion of the arm member is projected to the side of the frame, A needle roller 42 provided at the base end is disposed on the support shaft 29 side.

As shown in FIGS. 3 to 5, the swing cam 50 is formed of a swing cam member having one end rotatably supported by the support shaft 29 and the other end protruding toward the needle roller 42 of the rocker arm 40. The The cam surface 51 formed on the other end surface is in rolling contact with the needle roller 42. A sliding roller 52 is rotatably incorporated in the lower portion of the swing cam member.
As shown in FIG. 5, the center rocker arm 60 is disposed at a point surrounded by the intake cam 26 a, the control shaft 28, and the sliding roller 52. The center rocker arm 60 is formed in an L shape by an arm portion 61 that extends toward the upper sliding roller 52 and an arm portion 62 that extends directly below the control shaft 28 in the lateral direction. A slope 61 a (for example, a surface having a low control shaft side and a high support shaft side) formed on the tip surface of the arm portion 61 is in contact with the sliding roller 52 of the swing cam 50. The sliding roller 63 supported by the intersecting portion of the arm portions 61 and 62 is brought into rolling contact with the cam surface of the intake cam 26a, and the cam displacement of the intake cam 26a as a valve drive output is passed through the arm portion 61 through the swing cam. Output to 50.

  The pin part 64 supported at the end of the arm part 62 so as to be freely bent is inserted into a through hole 65 formed in the control shaft 28 so as to be freely rotatable. By this insertion, the center rocker arm 60 is swingably supported with the bending point as a fulcrum. When the control shaft 28 is rotationally displaced by the built-in structure of the center rocker arm 60, the center rocker arm 35 changes the direction of contact with the intake cam 26a and the direction intersecting the cam shaft 16 (advance direction or delay). (Angular direction).

  Due to this displacement, the valve drive output output from the center rocker arm 60, for example, the valve lift amount and the opening / closing timing of the intake valve 14 are continuously varied simultaneously. That is, as shown in FIG. 5, the cam surface 51 has a base circle section α corresponding to the base circle of the intake cam 26a on the upper side and a lift section β continuous with the base circle section on the lower side (upward of the intake cam 26a). The area 26x and the cam profile of the descending section 26y are commonly involved).

  Thereby, when the sliding roller 63 of the center rocker arm 60 is displaced in the advance angle direction or the retard angle direction of the intake cam 26a, the posture of the swing cam 50 changes, and the region of the cam surface 51 where the needle roller 42 swings is changed. Changes. That is, the ratio of the base section α and the lift section β where the needle roller 42 swings changes. Due to the change in the ratio of the base section α and the lift section β that accompanies the phase change in the advance direction and the phase change in the retard direction, the valve lift amount of the intake valve 14 becomes, for example, as shown in FIG. From the low lift V1 provided by the top cam profile to the high lift V7 provided by the entire cam profile from the top to the base end of the intake cam 26a. At the same time, the opening / closing timing of the intake valve 14 is varied more greatly than the opening timing.

That is, the variable valve mechanism 21 is configured so that the valve lift amount and the opening / closing timing can be continuously varied with the lift variable range from low lift to high lift. A screw member 66 for adjusting the protruding amount of the pin portion 64 is screwed into the through hole 65 so as to be able to advance and retract (for adjusting the valve opening / closing timing and valve lift amount for each cylinder).
The rocker arm mechanism 22 (exhaust side) has a pair of rocker arms 67 as shown in FIG. 5 (only one side is shown). The pair of rocker arms 67 are positioned on both sides of the center rocker arm 35 and are rotatably supported by the exhaust rocker shaft 27. A roller member (not shown) at one end is brought into rolling contact with the cam surface of the exhaust cam 26b, and an adjusting screw portion 67a at the other end is projected to the side of the frame.

  With these structures, the camshaft 26, the variable valve mechanism 21, and the rocker arm mechanism 22 are integrated into one. Each fixed seat 34 of the unitized variable valve apparatus 20 is installed on the boss portion 17 protruding from the bottom surface of the recess 2a (cylinder head 2) as shown in FIGS. Each fixed seat 34 is fixed together with the cylinder head 2 by a cylinder head bolt 18 screwed into the cylinder block 1 through the fixed seat 34 and the cylinder head 2 as shown in FIGS. Tighten together). The foremost and rearmost holding members 25 are also fixed to the cylinder head 2 with other fixing bolts 18a.

  As shown in FIG. 5, the adjustment valve portion 41 of each rocker arm 40 (for intake air) is disposed at the stem end of the intake valve 14 assembled to the cylinder head 2 as shown in FIG. An adjusting screw portion 67 a of the rocker arm 67 is disposed at the stem end of the exhaust valve 15 assembled to the cylinder head 2. A pusher 68 is assembled to the swing cam 50. The pusher 68 is a component that presses the center rocker arm 60 against the intake cam 26 a via the swing cam 50.

  Further, one end portion of the camshaft 26 protrudes forward through a penetrating portion 1b provided on an end wall surrounding the concave portion 2a of the cylinder head 1 as shown in FIG. A cam sprocket 70 is provided at the protruding end of the camshaft 26 as shown in FIGS. An endless timing chain 72 is stretched between the cam sprocket 70 and a crank sprocket 71 provided at one end of the crankshaft 9 so that the camshaft 26 is rotated by crank output.

  By the cooperation with the camshaft 26, the intake air can be effectively sucked into the cylinder 6 in the range of low lift to high lift, for example, as shown by the valve lift characteristics in FIG. The closing of the lift or middle lift is performed at a timing before the piston 7 in the intake stroke reaches the bottom dead center, and the closing of the high lift such as V4 to V6 has passed the bottom dead center of the piston 7 in the intake stroke. It is performed at the following timing.

  On the other hand, as shown in FIG. 3, a drive device 80 that drives the control shaft 28 is provided at the foremost portion of the cylinder head 1. The drive device 80 is a device that constitutes the variable valve mechanism 20 together with the variable valve mechanism 21, and includes, for example, an electric motor 81 as a rotational drive source, and a transmission mechanism separate from the electric motor 81, for example, a worm gear reduction mechanism 82. A combined structure is used. For the worm gear reduction mechanism 82, for example, a combination of a fan-shaped worm wheel gear 83 and a worm shaft gear 84 meshing therewith is used. Of these, the portion including the worm shaft gear 84 is unitized as a worm shaft gear unit 85 separate from the worm wheel gear 83.

  That is, the fan-shaped worm wheel gear 83 has a large number of gear teeth 87 on the outer peripheral edge portion of the fan-shaped plate-shaped main body 86 as shown in FIGS. A plate-shaped part is used. This fan-shaped component mounting seat 88 is fixed to the shaft end of the control shaft 28 facing forward from the foremost holder portion 32 by a fixing bolt 89, and the gear teeth 87 are arranged above the cylinder head 2.

  The worm shaft gear unit 85 has a frame 90 as shown in FIGS. The frame 90 includes a base portion 90a extending in the width direction of the cylinder head 2 and a pair of arm portions 90b extending in the front-rear direction of the cylinder head 2 from both end portions of the base portion 90a. A bearing hole 90c (shown in FIG. 2) is formed at the tip of the arm portion 90b. As the worm shaft gear 84, a shaft 84b having worm gear teeth 84a in the middle is used. Both end portions of the shaft 84b are rotatably supported by the bearing holes 90c, and the worm gear portion 84b is disposed between the pair of arm portions 90b. Then, one of the male part 91a and the female part 91b constituting the Oldham coupling 91, for example, the male part 91a is connected to the end of the shaft 84b protruding from the arm part 90b. In addition, installation seats 92 for mounting on the cylinder head 2 are formed at both ends of the base portion 90a.

As shown in FIG. 4, these installation seats 92 are installed on a receiving seat 94 formed on the upper portion of the foremost holder portion 32 using a fixing bolt 93, and the worm shaft gear unit 85 is attached to the cylinder head 2. It is installed sideways. At this time, the worm shaft gear 84 meshes with the worm wheel gear 83 as shown in FIG.
Thereby, the control rotation (rotation that determines the valve lift amount and the required valve characteristics of the opening / closing timing) input from the male portion 91a of the Oldham coupling 91 is transmitted to the control shaft 28 through the meshing portion 95 of both the gears 83 and 84. To be. Specifically, for example, when the worm wheel gear 83 is rotationally displaced in the direction toward the exhaust rocker shaft 27 as shown by an arrow in FIG. 2, the control rotation for controlling to the high lift side is controlled by the control shaft 28. On the other hand, when it is rotationally displaced in the direction toward the Oldham coupling 91, the control rotation for controlling to the low lift side is transmitted to the control shaft 28.

  Here, the valve reaction force acts on the control shaft 28 only in one rotational direction by assembling or setting each part of the variable valve mechanism 21. Here, for example, the valve reaction force of the intake valve 14 is applied only in the low lift direction. That is, the valve reaction force in the thrust direction acts on the worm shaft gear 84 only in one axial direction. In order to receive the valve reaction force in the thrust direction, as shown in FIGS. 2 to 4, only one thrust receiver 96 is provided on the shaft portion of the worm shaft gear 84, for example, the shaft portion on the Oldham coupling 91 side.

  On the other hand, as shown in FIGS. 2 and 3, the electric motor 81 uses an electric motor body 81a in which a rotor and a stator (not shown) are combined. That is, the electric motor 81 includes an electric motor portion 81a having a cylindrical insertion portion 81d at the tip and a mounting bracket 81b attached to the body. The motor shaft 81c of the electric motor portion 81a extends forward through the center of the insertion portion 81d. The remaining part of the Oldham coupling 91, that is, the female portion 91b is attached to the front end portion of the motor shaft 81c extending forward. The mounting bracket 81b is formed of an L-shaped bracket member that can be attached to a motor mounting surface 2b (shown in FIG. 2) formed on the side of the cylinder head 2. Moreover, the insertion part 81d has comprised the shape which can be inserted in the cylindrical insertion port part 3a formed in the side wall of the rocker cover 3, as FIG.1 and FIG.2 shows. An annular oil seal member 98 is attached to the outer peripheral surface of the insertion portion 81d so as to protrude outward from the outer peripheral surface.

  Using these structures, the electric motor 81 is detachably assembled to the worm shaft gear unit 85. Specifically, as shown in FIGS. 1 and 2, the electric motor 81 includes an insertion portion 81d inserted into the insertion portion 3a, and the female portion 91b at the tip is used as a guide for the worm shaft gear unit. Then, the mounting bracket 81b is bolted to the motor mounting surface 2b of the cylinder head 2 to be assembled in a direction crossing the control shaft 28. However, when the insertion portion 81d is inserted into the insertion port portion 3a, only the oil seal member 98 is brought into elastic contact with the inner surface of the insertion port portion 3a, and the other outer peripheral surface portion is separated from the inner surface of the insertion port portion 3a (FIG. 2).

  The variable valve operating apparatus 20 responsible for adjusting the intake air amount improves responsiveness during low / medium load operation of the vehicle, such as when a throttle valve is used, and engine output performance during high load operation of the vehicle. Ingenuity is adopted. The same technique is used to change the valve closing timing when the intake valve 14 is controlled to the low lift range and the valve closing timing when the intake valve 14 is controlled to the high lift range according to the required driving characteristics of the vehicle. It has been.

  In this technique, as shown in FIG. 5, a structure in which a part of the cam profile of the descending section 26y of the intake cam 26a is changed is used. Specifically, after the cam profile forming the descending section 26y of the intake cam 26a, the cam profile portion in the low lift region S1 used at the valve closing timing at the time of low lift and the high lift used at the valve closing timing at the time of high lift. A structure is adopted in which the gradient with the cam profile portion of the region S2 is different.

The point of the gradient will be described using the valve lift curve of the intake cam 26a. The gradient setting method shown in FIG. 8 is used for this.
That is, the diagram shown in FIG. 8 includes a low lift region S1 used at the low lift valve closing timing and a high lift region S2 used at the high lift valve closing timing on the Z line as the boundary line. A valve lift curve of the divided intake cam 26a is shown.

  In setting the gradient, as shown in FIG. 8, among the cam profiles forming the descending section 26y of the intake cam 26a, the gradient E1 of the low lift region S1 used at the timing of closing the low lift (in the gradient A of the present application). The slope E2 of the high lift region S2 used at the valve closing timing of the high lift is made gentler than that of the normal intake cam indicated by the two-dot chain line (corresponding to the diagram of FIG. 15). Is equivalent to the gradient B of FIG. 15), compared to a normal intake cam indicated by a two-dot chain line (corresponding to the diagram of FIG. 15). Thus, the low lift region S1 and the high lift region S2 have a relationship of gradient E1 <E2.

  More specifically, the predetermined point is based on a point on the cam profile at the boundary between the low lift region S1 and the high lift region S2, which coincides with the timing when the piston 7 in the intake stroke shown in FIG. 7 reaches the bottom dead center. As the point G, the inclination of the low lift region S1 with respect to the reference point G is made gentle by, for example, θ1 with respect to the cam profile of a normal intake cam. Further, the slope of the high lift region S2 with respect to the reference point G is set to be steep by, for example, rising by θ2 with respect to the cam profile of a normal intake cam. That is, the gradient E1 <E2 is determined based on a point corresponding to the bottom dead center in consideration of the specific movement of the variable valve gear 20.

Next, through the action of the variable valve device 20, the setting of the gradients E1 and E2 ensures high response during low / medium load operation of the vehicle and high engine output during high load operation of the vehicle. Describe the points.
Now, it is assumed that the camshaft 26 is driven (rotated) by the shaft output of the crankshaft 9 transmitted from the timing chain 72 as shown in the direction of the arrow in FIGS.

At this time, as shown in FIG. 5, the sliding roller 63 of the center rocker arm 60 receives the cam displacement of the intake cam 26a. As a result, a valve drive output is output from the center rocker arm 60. That is, the center rocker arm 60 swings in the vertical direction with the pin portion 64 as a fulcrum according to the cam displacement.
The sliding roller 52 of the swing cam 50 receives the swinging displacement of the center rocker arm 60 through an inclined surface 61 a that is in rolling contact with the sliding roller 52. For this reason, the swing cam 50 repeats the swinging motion that is pushed up or lowered by the slope 61a while rolling on the slope 61a. As the swing cam 50 swings, the cam surface 51 of the swing cam 60 reciprocates in the vertical direction.

At this time, since the cam surface 51 is in rolling contact with the needle roller 42 of the rocker arm 40, the cam surface 51 periodically presses the needle roller 42. In response to this pressing, the rocker arm 40 is swung with the control shaft 28 as a fulcrum to open and close the pair of intake valves 14.
On the other hand, each exhaust rocker arm 67 receives the exhaust cam 26b and is driven in accordance with the cam profile of the cam 26b. Accordingly, each exhaust rocker arm 67 swings around the exhaust rocker shaft 27 as a fulcrum, and opens and closes the exhaust valve 15, respectively.

  At this time, it is assumed that the electric motor 81 is actuated to increase the lift amount according to a command from a control unit (not shown). Then, the rotation of the electric motor 81 is transmitted to the worm shaft gear 84 through the Oldham coupling 91, and the fan-shaped worm wheel gear 83 engaged with the worm shaft gear 84 is rotationally displaced (in the high lift direction in FIG. 2). . Thereby, the rotation of the electric motor 81 is transmitted to the control shaft 28 while being decelerated, and the control shaft 28 is rotated to the point of the required valve lift.

Due to this rotational displacement, the position of the center rocker arm 60 is displaced. As a result, the sliding roller 63 of the center rocker arm 60 is displaced along the rotational direction on the intake cam 26a, and the cam surface 51 of the swing cam 50 has an angle close to vertical as shown in FIGS. Position the posture.
Due to the posture of the cam surface 51, the region (ratio) of the cam surface 51 where the needle roller 42 crosses is set to a region that provides a high lift amount. That is, the ratio is set to a short base circle section α and a long lift section β, and the needle roller 42 crosses the sections α and β.

As a result, for example, the intake valve 14 is driven at a high lift amount as shown in the characteristics such as V5, V6, and V7 in FIG. 7, and the opening timing is substantially the same as that at the maximum lift. The valve is closed at a timing after passing the bottom dead center of the intake stroke while maintaining.
Since the high lift region S2 of the intake cam 26a used at the valve closing timing here has a large gradient (inclination: large) as shown in FIG. 8, the intake valve 14 can increase the valve closing speed. Due to this increase in the valve closing speed, the intake valve 14 is instantaneously closed while maintaining a high lift up to the immediate vicinity of the valve closing position.

That is, due to the increase in the valve closing speed caused by the gradient E2, the intake valve 14 earns a state where it is kept at a high lift for a long time and increases the intake air amount, so that the engine output can be increased.
Thereby, a high engine output can be obtained in high load driving such as high speed driving and mountain driving in which high lift is frequently used. In particular, when the valve closing speed is increased, the intake valve 14 can be closed at a quick closing speed in accordance with the timing of the inertia intake of the engine and the intake pulsation, so that the supercharging effect can be achieved over the entire engine rotation range. The engine output can be expected to increase.

  On the other hand, a low lift amount is used. At this time, the electric motor 81 is actuated in the opposite direction to that of the high lift, and the required valve lift is output. Then, the rotation of the electric motor 81 is transmitted to the worm shaft gear 84 through the Oldham coupling 91, and the fan-shaped worm wheel gear 83 is rotationally displaced in the opposite direction (low lift direction in FIG. 2). Thereby, the rotation of the electric motor 81 is transmitted to the control shaft 28 while being decelerated, and the control shaft 28 is rotated to a required valve drive output, for example, a point of low valve lift.

  With this rotational displacement, as shown in FIGS. 11 and 12, the fulcrum position (pin portion 64) of the center rocker arm 60 is rotationally displaced in a direction approaching the intake cam 26a. Then, the sliding roller 63 of the center rocker arm 60 is displaced on the intake cam 26a in the direction opposite to the rotation direction of the intake cam 26a. As a result, the rolling contact position between the center rocker arm 60 and the intake cam 26a is shifted in the direction of advance on the intake cam 26a.

  By changing the rolling contact position, the top position of the valve lift curve moves in the advance direction. The slope 63 is also displaced in the advance direction in response to the movement of the center rocker arm 60. By the movement of the center rocker arm 60, the swing cam 50 changes to a posture in which the cam surface 51 is inclined downward as shown in FIGS. As the inclination increases, the area of the cam surface 51 where the needle rollers 42 come and go changes to a ratio in which the base circle section α is gradually longer and the lift section β is gradually shortened. Due to the change in the ratio, the intake valve 14 gradually changes from driving using the entire area of the intake cam 26a to limited driving at the cam top.

Thereby, for example, the intake valve 14 is driven to a low lift as shown by the valve lift characteristics such as V1, V2, and V3 in FIG. At the same time, the intake valve 14 is closed at a timing before the bottom dead center of the intake stroke while maintaining the timing at which the valve is opened from substantially the same timing as the maximum lift. That is, the valve characteristics are controlled to be suitable for low / medium load operation of the vehicle.
The low lift region S1 of the intake cam 26a used at the valve closing timing here has a small gradient (inclination: small) as shown in FIG. Due to the gradient E1, the valve closing speed of the intake valve 14 becomes slower than that of the intake cam as shown by a two-dot chain line in FIG.

  That is, for example, when the operation is performed at a low lift and the closing timing C0 in FIG. 8, the valve closing is performed to slightly increase the air amount in order to follow a change in some operating conditions such as slow acceleration. In order to delay the timing slightly, when the control shaft is rotated by δ to the lift point of the required valve in response to a command from a control unit (not shown), the valve closing timing changes to C1 in the downward gradient shown by the two-dot chain line in FIG. To do. However, by making the gradient E1 gentle, a change in the valve closing timing is secured at C2 later than that, and the control responsiveness becomes high. In other words, the air volume can be controlled quickly in response to driver requests and control unit commands, which not only improves vehicle response, but also suppresses engine rotation instability caused by ever-changing driving environments. be able to. Furthermore, since the seating speed of the valve is low, the seating noise is reduced, and the quietness during low / medium load operation is improved.

  Thus, the valve lift change at the time of continuously variable is optimized, and it is possible to ensure both high response performance at low / medium load operation and high output performance at high load operation with only the variable valve device 20. it can. In addition, since these performances can be ensured only by setting the gradients E1 and E2 (inclinations) of the cam profile portions of the descending section 26y of the intake valve cam 14, a simple structure is sufficient. In particular, the gradients E1 and E2 can be easily obtained by changing the cam profile gradient in the descending section of the intake valve cam with reference to the point G corresponding to the bottom dead center of the piston 7 so that high responsiveness during low lift operation can be easily achieved. High output performance during high lift operation can be ensured.

Moreover, the structure for changing the gradient of the intake valve cam 14 is applied to the variable valve operating apparatus 20 in which the up section 26x and the down section 26y of the intake valve cam 14 are replaced with the cam surface 51 of one kind of swing cam 50. There is no need to change the main structure that changes the lift and valve opening periods. For this reason, the swing-type variable valve device 20 is optimal with less burden.
That is, when the cam profile corresponding to the prior art shown in FIG. 15 is applied to the intake cam 26a, the valve closing at the time of low lift is the L region of the cam of FIG. The cam profile speed in the region becomes faster than the cam profile speed in the H region, which is the reverse of the proposal of the present application.

FIG. 13 shows another embodiment of the invention .
In the present embodiment, focusing on the amount of change in the valve closing timing per unit control angle of the control shaft 28, the valve closing speed is changed in the low lift region S1 by changing the valve closing timing as in the first embodiment. The intake air amount is increased by delaying, and in the high lift range S2, the valve closing speed is increased to increase the intake air amount.

In the present embodiment, for example, by changing the operation of the electric motor 81, or by changing the feed amount of the worm wheel gear 83 and the worm shaft gear 84, the same valve closing as in the first embodiment is performed. I'm trying to get timing.
That is, as shown in FIG. 13, for example, the amount of change in valve closing timing in the low lift region S1 per unit control angle delta Δ1 of the control shaft 28, specifically, the amount of change in valve closing timing C before the bottom dead center, The valve closing timing change amount in the high lift region S2 per unit control angle delta Δ1 of the control shaft 28, specifically, the valve closing timing amount D after the bottom dead center, The valve closing timing change amount C and the valve closing timing change amount D are set to have a relationship of C> D by making it smaller than the valve closing timing change amount.

In this way, the same characteristic as the valve lift curve of the first embodiment, that is, the low lift region S1 delays the valve closing speed, and the high lift region S2 has the characteristic of increasing the valve closing speed.
Thus, even if the method of changing the valve closing timing change amount per unit control angle of the control shaft 28 is used, it is the same as the gradient technique used in the first embodiment, and an effective valve closing timing is easily obtained. be able to.

FIG. 14 shows another different embodiment of the invention .
In the present embodiment, focusing on the acceleration caused by the cam profile in the descending section 26y of the intake cam 26a, an attempt is made to obtain the same valve closing timing as in the first embodiment.
That is, the cam profile forming the descending section 26y of the intake cam 26a has a peak negative acceleration value Q1 generated at the top of the intake cam 26a when the intake cam 26a is rotationally displaced as shown in FIG. Decreases at the low lift region S1 used at the closing timing of the low lift, increases again at the boundary between the low lift region S1 and the high lift region S2 used at the closing timing of the high lift, and thereafter at the high lift region S2. The curve which makes the characteristic which decreases again was adopted.

When a cam acceleration having two characteristics protruding in the negative direction, which is different from the acceleration curve of the normal intake cam shown in FIG. 15, is adopted, the valve is closed in the low lift region S1 as shown in the valve lift curve of FIG. Since the gradient E1 for reducing the speed is formed and the gradient E2 for increasing the valve closing speed is formed in the high lift region S2, it is the same as the gradient technique used in the first embodiment.
Therefore, as in the second embodiment, an effective valve closing timing can be easily obtained.

The present invention is not limited to the first embodiment described above, and various modifications may be made without departing from the spirit of the present invention. For example, in the above-described first embodiment, the cam type variable valve operating apparatus configured by using the rocker arm, the swing cam, and the center rocker arm is used. The present invention may be applied to a variable valve gear that can be varied .

1 is a perspective view showing an overview of an internal combustion engine according to a first embodiment of the present invention. Sectional drawing which follows the AA line in FIG. The perspective view of the internal combustion engine which removed the rocker cover and the timing chain cover, and exposed the variable valve apparatus. The perspective view which removed the variable valve apparatus from the cylinder head. Sectional drawing of the variable valve apparatus which follows the BB line in FIG. Sectional drawing of the variable valve apparatus which follows the CC line in FIG. The diagram for demonstrating a continuous variable characteristic. The diagram explaining the cam profile which changes valve closing speed in a low lift area and a high lift area. Sectional drawing for demonstrating the motion at the time of the high lift of a variable valve apparatus. Similarly sectional drawing. Sectional drawing for demonstrating the motion at the time of the low lift of a variable valve apparatus. Similarly sectional drawing. The diagram explaining the technique of the principal part of embodiment of another invention . The diagram explaining the technique of the principal part of embodiment of another different invention . The diagram explaining the characteristic of the cam used for a normal engine.

Explanation of symbols

2 Cylinder head 14 Intake valve (valve)
20 Variable valve operating device 21 Variable valve operating mechanism 26 Camshaft 26a Intake cam (Intake valve cam)
26y descending section 28 Control shaft E1, E2 Gradient (valve closing characteristic changing means)
S1 Low lift area S2 High lift area.

Claims (1)

A camshaft having an intake valve cam ;
Receives the intake valve cam and outputs a valve drive output. The valve drive output is continuously variable from a low lift range to a high lift range by using different parts of the same cam profile of the intake valve cam. A variable valve mechanism to
A valve closing characteristic changing means for changing the valve closing characteristic when controlled to the low lift range and the valve closing characteristic when controlled to the high lift range according to the required driving characteristics of the vehicle ,
The valve closing characteristic changing means sets A as the gradient of the low lift region used at the valve closing timing at the time of the low lift, among the cam profiles forming the descending section of the cam for the intake valve, and is also closed at the time of the high lift. When the gradient of the high lift region used in the valve timing is B, the gradients A and B are set to A <B,
The slope A of the low lift region is set by a cam profile in a descending section where the valve is closed before the piston of the intake stroke of the internal combustion engine reaches bottom dead center, and the slope B of the high lift region is It is set with the cam profile of the descending section where the valve is closed at the timing after the piston of the intake stroke of the engine passes the bottom dead center,
The variable valve device for an internal combustion engine, characterized that you quickly closing speed when it is controlled to the high lift region than closing speed when it is controlled to the low lift region.

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