WO2008065881A1

WO2008065881A1 - Variable valve gear

Info

Publication number: WO2008065881A1
Application number: PCT/JP2007/071997
Authority: WO
Inventors: Akio Kidooka; Shuichi Ezaki
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2006-11-28
Filing date: 2007-11-13
Publication date: 2008-06-05
Also published as: JP2008133770A; EP2093389A1; CN101542078A; US20100089348A1

Abstract

A cam shaft (22) etc. having a cam (18) etc. for pushing and moving a valve (12), which is urged in a valve closing direction by a valve spring (17), is driven by a motor (30) etc. A valve lifter (16), in contact with the cam (18) etc., is provided between the valve (12) and the cam (18) etc. The valve lifter (16) has a top surface (16a) formed such that the line tangential to the top surface and a nose top (18c) of the cam (18) inclines relative to the direction perpendicular to the axis of a valve stem (14).

Description

Specification

Variable valve gear

Technical field

[0001] The present invention relates to a variable valve gear that drives a valve of an internal combustion engine.

Background art

Conventionally, for example, Patent Document 1 discloses an internal combustion engine having a valve drive system that opens and closes a valve by a motor. In this conventional valve drive system, when an abnormality occurs in the synchronous control between the rotation of the camshaft and the rotation of the crankshaft, the valve opening / closing operation is stopped using the lost motion mechanism, or a small By switching to a low lift cam to drive the valve with the lift amount, evacuation travel is enabled. The applicant has recognized the following documents including the above-mentioned documents as those related to the present invention.

Patent Document 1: Japanese Unexamined Patent Publication No. 2005-54732

Patent Document 2: Japanese Utility Model Publication No. 6-87605

Patent Document 3: Japanese Unexamined Patent Publication No. 2004-225562

Patent Document 4: Japanese Unexamined Patent Publication No. 2004-225610

Patent Document 5: Japanese Patent No. 3359524

Disclosure of the invention

Problems to be solved by the invention

[0004] As one aspect of a system for electrically driving a camshaft like the conventional valve drive system described above, a variable valve apparatus in which a cam drives a valve via a valve lifter is known. In such a type of variable valve device, if the variable valve device malfunctions and the motor drive may stop while the nose tip of the cam is in contact with the valve lifter, the valve lift It may remain open with the maximum lift. When such a situation occurs, interference between the valve that has stopped in the maximum lift state and the piston that continues to reciprocate can occur.

[0005] For the purpose of avoiding the above interference, the retraction control provided in the conventional valve drive system described above The mechanism for stopping the opening / closing operation of the valve and the mechanism for switching to the low lift cam are complicated in the variable valve device of the type in which the camshaft is rotationally driven by a motor. It will make it. Further, in the method using the mechanism for the retraction control described above, the interference between the valve and the piston is detected during the transition period after the abnormality of the synchronous control between the camshaft and the crankshaft is detected and switched to the retraction control. Can occur.

[0006] The present invention has been made to solve the above-described problems, and a motor is used to rotate a cam shaft provided with a cam that pushes a valve urged in a valve closing direction by a valve spring. An object of the present invention is to provide a variable valve device that can reliably eliminate interference between a valve and a piston when an abnormality occurs, using a simple structure in the variable valve device to be driven.

Means for solving the problem

[0007] A first invention is a variable valve operating apparatus for driving a cam shaft provided with a cam for pushing a valve biased in a valve closing direction by a valve spring by a motor,

A valve lifter that comes into contact with the cam is provided between the cam and the valve, and the valve lifter has a tangential direction to the nose tip of the cam as viewed from the axial direction of the cam shaft and the axis of the valve stem. It has a top surface formed so as to be inclined with respect to the orthogonal direction.

[0008] In addition, in a second invention according to the first invention, the direction of inclination of the tangent is directed toward the advancing direction of a contact point between the cam and the valve lifter during normal rotation of the cam. The distance between the tangent and the bottom surface of the valve lifter is reduced.

[0009] In addition, in a third invention according to the first or second invention, the top surface is formed in a convex curved surface that is convex toward the cam side when viewed from the axial direction of the cam shaft. It is characterized by that.

[0010] Further, in a fourth invention according to the third invention, in the third invention, an apex in which the height from the bottom surface of the valve lifter is the highest on the top surface formed in a convex curved surface that is convex toward the cam side; The contact point between the nose tip and the valve lifter is configured to be separated from each other when viewed from the axial direction of the cam shaft.

[0011] Further, according to a fifth aspect of the invention, in the third or fourth aspect of the invention, a convex curved surface that is convex toward the cam side. The top surface formed in a shape is formed such that the height from the bottom surface of the valve lifter is the highest on the central axis of the valve lifter,

The cam shaft is arranged so that the central axis of the cam shaft and the central axis of the valve lifter do not intersect when viewed from the axial direction of the cam shaft.

[0012] Further, according to a sixth aspect of the present invention, in the third or fourth aspect of the invention, the cam shaft has a central axis of the cam shaft that intersects an axis of the valve stem when viewed from an axial direction of the cam shaft. Arranged so that

The top surface formed in a convex curved shape that is convex toward the cam side has an apex force S at which the height from the bottom surface of the valve lifter is the highest, as viewed from the axial direction of the cam shaft, It is characterized by being formed so as to be offset with respect to the axis.

[0013] In addition, a seventh invention is characterized in that, in the first or second invention, the top surface is an inclined surface having a constant gradient when viewed from the axial direction of the cam shaft.

[0014] Further, in an eighth invention according to any one of the first to seventh inventions, when a command value given to the motor when the motor drives the force shaft reaches a predetermined value, The power supply control means for stopping the power supply to the motor is further provided.

[0015] In addition, a ninth invention according to any one of the first to eighth inventions, further includes a torque reduction mechanism that generates a reduced torque for reducing the drive torque of the cam shaft,

The torque reducing mechanism is characterized in that the reduced torque is configured to be smaller than the torque acting on the camshaft based on the urging force of the valve spring.

The invention's effect

[0016] According to the first aspect of the invention, even if the drive of the camshaft by the motor is stopped with the nose tip of the cam in contact with the top surface of the valve lifter, the urging force of the valve spring is reduced. It will also act in the direction of rotating the cam only in the direction of pushing the force upward. For this reason, according to the present invention, it is possible to favorably avoid that the valve remains open when an abnormality occurs, and to reliably avoid interference between the valve and the piston.

[0017] According to the second invention, even if the drive of the camshaft by the motor is stopped with the nose tip of the cam in contact with the top surface of the valve lifter, the cam is in the forward rotation direction. I will escape I will become. For this reason, according to the present invention, it is possible to easily synchronize the cam and the piston at the time of the maximum start after the occurrence of an abnormality, and it is possible to reduce the possibility of interference between the valve and the piston. In addition, it will be possible to expect a reduction in required power immediately after starting.

[0018] According to the third to seventh inventions, even if the drive of the cam shaft by the motor is stopped with the nose tip of the cam in contact with the top surface of the valve lifter, the valve spring is attached. The force also acts in the direction of rotating the cam, not only in the direction of pushing the cam upward. For this reason, according to the present invention, it is possible to satisfactorily avoid that the valve remains open when an abnormality occurs, and to reliably avoid interference between the valve and the piston.

[0019] According to the eighth aspect of the invention, even if an abnormality occurs in the variable valve device such that the driving force of the cam shaft remains in the motor, the urging force of the valve spring rotates the cam. It is allowed to be converted into torque. For this reason, the force S is used to reliably avoid interference between the valve and the piston.

[0020] According to the ninth aspect of the present invention, in the variable valve gear including a torque reduction mechanism for reducing the drive torque of the camshaft, sufficient urging force of the valve spring is ensured as a torque for rotating the cam. It is possible to reduce the interference between the valve and the piston with the force S.

Brief Description of Drawings

FIG. 1 is a perspective view showing a configuration of a variable valve operating apparatus according to a first embodiment of the present invention.

FIG. 2 is a view of the cam shaft viewed from the axial direction in order to explain the detailed configuration of the cam shaft shown in FIG. 1.

FIG. 3 is a schematic diagram showing how the valve lifter is driven by a cam.

FIG. 4 is a view showing a variable valve apparatus A having a valve lifter of a general shape to be referred for comparison with the configuration of the variable valve apparatus of Embodiment 1 of the present invention.

FIG. 5 is a diagram for explaining a characteristic configuration of the first embodiment of the present invention.

FIG. 6 is a view showing a first modification of the top shape of the valve lifter and the positional relationship between the valve lifter and the cam shaft. FIG. 7 is a view showing a second modification of the top shape of the valve lifter.

FIG. 8 is a flowchart of a routine executed in the second embodiment of the present invention.

FIG. 9 is a diagram for explaining a configuration of a torque reduction mechanism provided in the variable valve operating apparatus according to the third embodiment of the present invention.

FIG. 10 is a diagram for explaining a general setting of the reduced torque in the torque reducing mechanism having the same configuration as the torque reducing mechanism shown in FIG. 9.

FIG. 11 is a diagram for explaining setting of a reduced torque generated by the torque reduction mechanism according to the third embodiment of the present invention.

Explanation of symbols

10, 50 Variable valve gear

12 Banolev

14 Noreb stem

16, 42, 44 Noref, Lifter

16a, 42a, 44a Top surface

16b, 42b, 44b Bottom

17 Noreb Spring

18, 20 cam

18a base circle

18b Nose part

18c Nose tip (top)

22, 24 cam cars

30, 38 motor

40 ECU (Electronic Control Unit)

52 Torque reduction mechanism

54 Anti-phase cam

56 Spring

58 Energizing mechanism

BEST MODE FOR CARRYING OUT THE INVENTION [0023] Embodiment 1.

[Configuration of variable valve system]

Hereinafter, the basic configuration of the variable valve operating apparatus 10 according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG.

FIG. 1 is a perspective view showing a configuration of variable valve operating apparatus 10 according to the first embodiment of the present invention. A variable valve operating apparatus 10 shown in FIG. 1 is an apparatus for driving a valve of an internal combustion engine. Here, it is assumed that the internal combustion engine is configured as a straight IJ 4-cylinder engine. In FIG. 1, # 1 to # 4 represent the first to fourth cylinders of the internal combustion engine, respectively. The explosion order in this internal combustion engine is assumed to be # 1 → # 3 → # 4 → # 2, as in a general internal combustion engine. In the present embodiment, the variable valve operating device 10 functions as a device for driving the intake valve of each cylinder, and in FIG. 1, the exhaust valve side is not shown. However, the variable valve operating apparatus 10 may be configured as a device that drives the exhaust valve of each cylinder instead of or in addition to the intake valve.

The configuration shown in FIG. 1 is provided with two valves 12 functioning as intake valves for each cylinder. Valve stems 14 are fixed to the valves 12 respectively. A valve lifter 16 is attached to the upper end of the knob stem 14. A biasing force of a valve spring 17 (see FIG. 5) acts on the valve stem 14, and the valve stem 14 is biased in the valve closing direction by the biasing force. The variable valve operating apparatus 10 of the present embodiment is characterized by the shape of the top surface 16a of the valve lifter 16 and the positional relationship between the valve lifter 16 and cams 18 and 20 described later. The characteristic part will be described later with reference to FIG.

A corresponding cam 18 or 20 is disposed on the upper part of each valve lifter 16. As shown in Fig. 1, here, the cam corresponding to the valve lifter 16 disposed in the # 1 and # 4 cylinders is referred to as a cam 18, and the cam corresponding to the valve lifter 16 disposed in the # 2 and # 3 cylinders. Is called Cam 20. The cam 18 corresponding to # 1 cylinder and # 4 cylinder is fixed to the camshaft 22. The cams 20 corresponding to the # 2 and # 3 cylinders are fixed to a camshaft 24 that is rotatable with respect to the camshaft 22 and is arranged coaxially with the camshaft 22. In other words, in the configuration shown in FIG. 1, the camshaft is shared by the cylinders whose explosion times differ by 360 ° CA. And those camshafts, ie # The camshaft 22 corresponding to the 1 and # 4 cylinders and the camshaft 24 corresponding to the # 2 and # 3 cylinders are configured to be capable of rotating or swinging in the circumferential direction independently of each other. Yes. The cam shaft 22 and the cam shaft 24 are rotatably supported by a support member such as a cylinder head (not shown).

A first driven gear 26 is coaxially fixed to one camshaft 22. A first output gear 28 is meshed with the first driven gear 26. The first output gear 28 is fixed to the output shaft of the first motor 30. The first motor 30 is a servo motor capable of controlling the rotation speed and the rotation amount. As the first motor 30, for example, a DC brushless motor or the like is preferably used. The first motor 30 includes a rotation angle detection sensor such as a resolver and a rotary encoder for detecting the rotation position (rotation angle). With such a configuration, the torque of the first motor 30 can be transmitted to the camshaft 22 via these gears 26 and 28.

A second driven gear 32 is coaxially fixed to the other cam shaft 24. A second output gear 36 is meshed with the second driven gear 32 via an intermediate gear 34. The second output gear 36 is fixed to the output shaft of the second motor 38. The specific configuration of the second motor 38 is the same as that of the first motor 30. According to such a configuration, the torque S of transmitting the torque of the second motor 38 to the camshaft 24 through these gears 32, 34, and 36 is reduced.

The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 40! /. Various sensors (not shown) such as a crank angle sensor and a cam angle sensor, and various actuators such as a first motor 30 and a second motor 38 are connected to the ECU 40. The ECU 40 can control the rotational speed and the rotational amount of the first motor 30 and the second motor 38 based on the sensor outputs. More specifically, by giving a drive command to the motor 30 or the like so that the cam shaft 22 or the like is continuously driven in one direction, the cam shaft 22 or the like can be rotated. Further, the ECU 40 can swing the camshaft 22 and the like by giving a drive command to the motor 30 and the like so that the rotation direction of the motor 30 and the like is reversed while the valve 12 is open.

FIG. 2 shows the camshaft 22 in order to explain the detailed configuration of the camshaft 22 shown in FIG. It is the figure seen from the axial direction. As described above, the cam 18 (# 1) and the cam 18 (# 4) are fixed to the camshaft 22! /. As shown in FIG. 2, the # 1 cylinder cam 18 (# 1) has two cam surfaces 18a and 18b having different profiles. The base circle portion 18a, which is one cam surface, is formed so that the distance from the center of the cam shaft 22 is constant. The nose portion 18b, which is the other cam surface, is formed such that the distance from the center of the cam shaft 22 gradually increases and the distance gradually decreases after exceeding the top portion 18c (the nose tip portion 18c). The # 4 cylinder cam 18 (# 4) also has a base circle portion 18a and a nose portion 18b similar to the cam 18 (# 1). The top 18c of the cam 18 (# 1) and the top 18c of the cam 18 (# 4) are arranged so as to be shifted from each other by 180 ° in the circumferential direction of the cam shaft 22. Although the detailed explanation is omitted here, cam 20 (# 2) and cam 20 (# 3) are also different from cam shaft 22 in cam shaft 24 corresponding to # 2 cylinder and # 3 cylinder. It shall be structured in the same way as the case.

FIG. 3 is a schematic diagram showing how the valve lifter 16 is driven by the cam 18.

Here, the description will be made using the configuration on the cam 18 side, but the configuration on the cam 20 side is the same. In this specification, in the drawings from FIG. 3 onward, if there is no substantial difference between the configuration on the cam 18 side and the configuration on the cam 20 side, only one of them will be explained. The description of the other may be omitted.

As shown in FIG. 3, a valve lifter 16 that contacts the cam 18 is disposed between the cam 18 and the valve 12 (see FIG. 1). The valve lifter 16 has a top surface 16 a that contacts the cam 18. When the base circle portion 18a of the cam 18 and the valve lifter 16 are in contact with each other, the valve is brought into close contact with the valve seat (not shown) by the urging force of the valve spring 17, and the port is closed.

[0032] When the rotational motion of the first motor 30 is transmitted to the camshaft 22 via the gears 26 and 28, the cam 18 rotates integrally with the camshaft 22, and the nose portion 18b gets over the valve lifter 16. In the meantime, the valve lifter 16 is pushed down, and the valve 12 lifts (opens) against the urging force of the valve spring 17.

FIGS. 3A and 3B show two drive modes of the cam 18. The forward drive mode, one of the drive modes, continuously rotates the first motor 30 in one direction. As shown in FIG. 3 (A), the cam 18 is moved in the forward rotation direction beyond the maximum lift position, that is, beyond the position where the nose tip 18c (top 18c) of the cam 18 contacts the valve lifter 16. This is a drive mode for continuous rotation. The other drive mode, the swing drive mode, is as shown in FIG. 3 (B) by switching the rotation direction of the first motor 30 before reaching the maximum lift position in the forward drive mode. In this mode, the cam 18 is reciprocated.

In the forward rotation drive mode, the operating angle of the valve 12 is controlled by controlling the rotational speed of the cam 18. In the swing drive mode, the operating angle of the valve 12 and the maximum lift amount can be controlled by controlling the rotational speed of the cam 18 and the angle range in which the cam 18 swings.

[Characteristics of this embodiment]

Next, the characteristic part of this embodiment will be described with reference to FIG. 4 and FIG. FIG. 4 is a view showing a variable valve apparatus A having a generally shaped valve lifter that is referred to for comparison with the configuration of the variable valve apparatus 10 of the present embodiment, as viewed from the axial direction of the camshaft. It is a figure. As shown in FIG. 4, a variable valve apparatus A to be compared with the variable valve apparatus 10 of the present embodiment is a general top surface formed so as to be a plane perpendicular to the axis of the valve stem. A valve lifter having

[0036] If any abnormality such as asynchronous rotation of the camshaft and crankshaft occurs in the variable valve apparatus A, the motor may be stopped. When the motor is stopped, the friction between the force and the valve lifter, the friction between the gears arranged between the motor and the camshaft, and the inertia of the motor! /, The rotation of the camshaft Although there are elements that act as resistance, the camshaft is basically rotatable. Therefore, when an abnormality occurs in the variable valve device A, if the cam is in contact with the valve lifter at the nose portion other than the tip of the nose (for example, as shown in FIG. 3 (B)), The cam is rotated by the valve spring reaction force, and the valve is returned to the closed state.

[0037] However, when the top surface of the valve lifter has such a planar shape! /, As shown in FIG. 4, the motor with the nose tip of the cam in contact with the top surface of the valve lifter. When the camshaft drive by is stopped, the lift amount of the valve becomes the maximum lift May remain open in a state.

[0038] In the case of the configuration shown in Fig. 4, the above situation occurs when the nose tip end of the cam contacts the top surface of the valve lifter and the tangent line between the nose tip and the top surface Since the direction of is perpendicular to the axis of the valve stem, the valve spring reaction force (see arrow in Fig. 4) acts only in the direction in which the camshaft is pushed upward, and in the direction in which the cam is rotated. It is because it does not. In addition, the configuration in which the above situation occurs is not limited to the case where the top surface of the valve lifter is a flat surface, and even if the top surface is a curved surface other than a flat surface, This is true as long as the direction of the tangent when contacting the surface is a configuration that is perpendicular to the axis of the valve stem.

[0039] If the above situation may occur, interference between the valve that remains open and the piston that continues to reciprocate may occur. Thus, in this embodiment, the configuration shown in FIG. 5 below is used so that the valve does not stop in the maximum lift state.

FIG. 5 is a view for explaining a characteristic configuration of the present embodiment, and is a view seen from the axial direction of the cam shaft 22. As shown in FIG. 5, in this embodiment, when viewed from the axial direction of the cam shaft 22, the tangential force between the nose tip 18c of the cam 18 and the top surface 16a of the valve lifter 16 is orthogonal to the axis of the valve stem 14. The shape of the top surface 16a of the valve lifter 16 is determined so as to be inclined with respect to the direction in which the valve lifter 16 is inclined, and the positional relationship between the valve lifter 16 and the cam shaft 22 is adjusted.

[0041] Then, the inclination direction of the tangent is directed toward the direction of travel of the contact point between the cam 18 and the valve lifter 16 during the forward rotation of the cam 18 (left direction in FIG. 5). The shape of the top surface 16a of the valve lifter 16 is determined so that the distance from the bottom surface 16b of the valve lifter 16 is reduced, and the positional relationship between the valve lifter 16 and the cam shaft 22 is adjusted.

[0042] As a specific example of the shape of the top surface 16a and the arrangement relationship described above, in this embodiment, the top surface 16a of the valve lifter 16 is viewed from the axial direction of the cam shaft 22 as shown in FIG. Is formed into a convex curved surface that is convex toward the force 18 side, more specifically, a cylindrical shape. The top surface 16a should be separated from the apex where the height from the bottom surface 16b is the highest, the contact point P between the nose tip 18c and the top surface 16a, and the force cam shaft 22 as viewed from the axial direction. Gu cam The central axis of the shaft 22 is offset with respect to the central axis of the valve lifter 16. In addition, in the present embodiment, the top surface 16a formed in the convex curved shape is formed so that the height of the valve lifter 16 is the highest on the central axis of the valve lifter 16, and the cam shaft 22 is The center axis of the cam shaft 22 is arranged so as to be away from the center axis of the valve lifter 16 when viewed from the axial direction of the cam shaft 22.

In the configuration shown in FIG. 5, the offset direction of the central axis of the cam shaft 22 with respect to the central axis of the valve lifter 16 is the traveling direction of the contact point P between the cam 18 and the valve lifter 16 when the cam 18 rotates forward. The arrangement of the cam shaft 22 with respect to the valve lifter 16 is adjusted so as to be on the side.

In this embodiment, the valve lifter 16 is prevented from rotating with respect to the cam 18 so that the tangential direction can always maintain the above-described direction during actual operation of the valve system. A stop mechanism is provided. Here, the force of which detailed illustration is omitted. Such a detent mechanism can be realized by the following configuration, for example. That is, a pin that faces in a direction perpendicular to the axis of the valve stem is made to penetrate the valve lifter. Then, a guide groove for the pin is formed in the cylinder head which is a peripheral member of the valve lifter so as to extend in the axial direction of the valve stem, and the pin is engaged with the guide groove.

As described above, in the configuration shown in FIG. 5, the tangential force between the nose tip 18c of the cam 18 and the top surface 16a of the valve lifter 16 when viewed from the axial direction of the cam shaft 22 The shape of the top surface 16a of the valve lifter 16 is determined so as to be inclined with respect to the direction orthogonal to the axis, and the positional relationship between the valve lifter 16 and the cam shaft 22 is adjusted. According to such a configuration, even when the nose tip 18c of the cam 18 is in contact with the top surface 16a of the valve lifter 16 when the motor is stopped, the valve spring reaction force pushes the cam 18 upward. It will also act in the direction in which the cam 18 is rotated.

That is, according to the above configuration, the valve spring reaction force acting on the cam 18 is not only the component in the axial direction of the valve stem 14 but also the decomposed component inclined with respect to the axial direction of the valve stem 14 ( (See the arrows in Fig. 5). As a result, when the cam 18 rotates, the valve operates in the valve closing direction.

[0047] Therefore, according to the configuration of the present embodiment, for evacuation control as provided in the prior art. Using a simple configuration that does not rely on a mechanism, it is possible to mechanically and reliably avoid interference between the valve 12 and the piston when an abnormality occurs. Also, avoid interference between the valve and piston during the transition period until switching to such evacuation control when an abnormality in synchronous control between the camshaft 22 and the crankshaft is detected. Can do.

Further, in the configuration shown in FIG. 5 described above, the inclination direction of the tangent line is in the advancing direction (left direction in FIG. 5) of the contact point between the cam 18 and the valve lifter 16 when the cam 18 is rotating forward. The shape of the top surface 16a of the valve lifter 16 is determined so that the distance between the tangent and the bottom surface 16b of the valve lifter 16 becomes smaller as it goes, and the positional relationship between the valve lifter 16 and the camshaft 22 is determined. Has been adjusted. More specifically, such a configuration is such that the force in the offset direction of the central axis of the cam shaft 22 with respect to the central axis of the valve lifter 16 is the forward direction of the contact point P between the cam 18 and the valve lifter 16 when the cam 18 is rotating forward. This is realized by adjusting the arrangement of the camshaft 22 with respect to the nozzle lifter 16.

[0049] According to such a configuration, when the motor is stopped with the nose tip 18c of the cam 18 in contact with the top surface 16a of the valve lifter 16, the cam 18 escapes in the forward rotation direction. Will be started. As a result, the final stop position of the cam 18 after such a relief operation is a position immediately after the end of the lift operation of the valve 12 at the normal time. When consideration is given to the direction in which the cam 18 escapes, it is possible to use the force S to produce the following excellent effects.

[0050] That is, in the case of the configuration in which the intake valves of all the cylinders are driven by sharing by the two motors 30 and 38 as in the present embodiment, the next time the cam 18 is rotated at the time of restart after occurrence of an abnormality. By the start of the valve lift, a marginal force S of about 60 ° in cam angle can be achieved. By determining the cam angle phase in the section of about 60 °, it is possible to synchronize with the piston phase and reduce the possibility of interference between the valve 12 and the piston. In addition, since the rotational speed of the cam 18 can be sufficiently increased in the section of about 60 ° to impart kinetic energy to the cam 18, a reduction in required power immediately after starting can be expected.

By the way, in the first embodiment described above, the top surface 16a of the valve lifter 16 has a convex curved shape that protrudes toward the cam 18 when viewed from the axial direction of the cam shaft 22, more specifically, Cylindrical shape The top surface 16a formed in the convex curved shape is formed so that the height of the valve lifter 16 is the highest on the central shaft of the valve lifter 16, and the cam shaft 22 is In view of the axial force of the shaft 22, the cam shaft 22 is arranged so that the central axis is separated from the central axis of the valve lifter 16. However, the shape of the top surface of the valve lifter and the positional relationship between the valve lifter and the camshaft in the present invention are tangential forces between the nose tip of the cam and the top surface of the valve lifter when viewed from the axial direction of the camshaft. If consideration is given to incline with respect to the direction perpendicular to the axis of the stem, the configuration is not limited to the configuration shown in FIG. 5 described above. For example, FIG. It may be configured as shown in the figure.

[0052] FIG. 6 is a diagram showing a first modification of the top shape of the valve lifter and the positional relationship between the valve lifter and the cam shaft. In the configuration shown in FIG. 6, the cam shaft 22 is positioned so that the central axis of the cam shaft 22 is positioned on the extension line of the valve stem 14 axis (that is, the central axis of the valve lifter 42) when viewed from the axial direction of the cam shaft 22. Axis 22 is arranged. Further, the top surface 42a of the valve lifter 42 is formed in a convex curved surface that is convex toward the cam 18 as viewed from the axial direction of the cam shaft 22, more specifically, in a cylindrical shape.

[0053] However, unlike the configuration shown in FIG. 5 described above, the top surface 42a formed in a convex curved surface is the apex force at which the height from the bottom surface 42b of the valve lifter 42 is the highest. The axial direction of the cam shaft 22 From the above, it is formed so as to be offset from the axis of the valve stem 14 (that is, the central axis of the valve lifter 42).

[0054] In the configuration shown in Fig. 6, the offset direction of the apex of the top surface 42a with respect to the central axis of the valve lifter 16 is the traveling direction of the contact point Q between the cam 18 and the valve lifter 16 when the cam 18 is rotating forward. The shape of the top surface 42a is determined so as to be in the reverse direction (right direction in FIG. 6). By adopting such an offset direction, when the motor may stop while the nose tip 18c of the cam 18 is in contact with the top surface 42a of the valve lifter 42, the cam 18 is released in the forward direction. It comes to be.

It should be noted that the anti-rotation mechanism of the valve lifter 42 can have the same force as that described above.

[0055] FIG. 7 is a diagram showing a second modification of the top shape of the valve lifter. In the configuration shown in FIG. 7, the top surface 44a of the valve lifter 44 is constant in view of the axial force of the camshaft 22. It is formed so that it may become the inclined surface which has the following gradient. In addition, the inclination direction of the top surface 44a is such that the distance from the bottom surface 44b of the valve lifter 44 decreases as the direction of travel of the contact point R between the cam 18 and the valve lifter 44 during the forward rotation of the cam 18 is increased. Has been. By adopting such an inclination direction, when the motor may be stopped with the nose tip 18c of the cam 18 in contact with the top surface 44a of the valve lifter 44, the cam 18 is released in the forward rotation direction. It becomes like this.

It should be noted that the anti-rotation mechanism of the valve lifter 44 can have the same force as that described above.

[0056] Embodiment 2.

Next, Embodiment 2 of the present invention will be described with reference to FIG.

The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 8 to be described later using the hardware configuration shown in FIGS. 1 to 3 and FIG. That ’s right.

[0057] [Characteristics of Embodiment 2]

If the abnormality that occurred in the variable valve operating system 10 is that the motor power supply is completely turned off, the configuration shown in FIG. By rotating the cam 18 and the like, it is possible to reliably avoid the interference between the valve 12 and the piston S. However, depending on the state of abnormality, the power supply may not be completely turned off, and the motor may still be able to drive the cam 18. In such a state, with the cam 18 pressing the valve 12, the driving torque of the cam shaft 22 by the motor and the torque acting on the cam shaft 22 based on the biasing force of the valve spring 17 are balanced. As a result, the valve 12 stops in a lifted state.

As a result, interference between the valve 12 and the piston may occur. Therefore, in the present embodiment, even when an abnormality occurs in the above-described manner, the driving reaction force when electrically driving the sliding cam 18 is ensured so that interference between the valve 12 and the piston can be surely avoided. More specifically, the power supply to the motor is stopped when the current command value (torque command value) given to the motor by the ECU 40 reaches a predetermined value when the value exceeds the predetermined value.

FIG. 8 is a flowchart of a routine executed by the ECU 40 in order to realize the above function. In the routine shown in FIG. 8, first, whether or not the camshaft 22 is stopped. It is determined according to the force S and the output of the cam angle sensor (step 100). As a result, if it is determined that the camshaft 22 is in a stopped state, then a current command value that the ECU 40 gives to the motor is acquired (step 102).

Next, it is determined whether or not the current command value acquired in step 102 is equal to or greater than a predetermined value (step 104). When the camshaft 22 is in a stopped state and power is supplied to the motor, the position of the cam 18 is held while the cam 18 lifts the valve 12. If the lift amount at this time exceeds a certain amount, interference between the valve 12 and the piston that continues to reciprocate may occur. The driving reaction force caused by the valve spring reaction force when the cam 18 pushes the valve 12 increases as the valve spring reaction force increases as the lift amount of the valve 12 increases. Therefore, the current command value of the cam 18 increases as the lift amount of the valve 12 increases. The predetermined value in step 104 is set to such a value that it can be determined whether or not the lift amount of the valve 12 is increased to such an extent that the interference between the valve 12 and the piston occurs! /, The

[0061] If it is determined in step 104 that the current command value is equal to or greater than the predetermined value, the power supply to the motor is stopped (step 106).

[0062] According to the routine shown in Fig. 8 described above, the current command value of the cam 18 is greater than or equal to a predetermined value under the situation where the camshaft 22 is in a stopped state, so that the valve 12 and the piston If it is determined that there is a possibility of interference, the power supply to the motor is stopped. That is, the urging force of the valve spring 17 is allowed to be converted into torque that rotates the cam 18. Further, the shape of the valve lifter 16 of the present embodiment and the positional relationship between the valve lifter 16 and the cam shaft 22 are configured in the same manner as in FIG. Therefore, if the power supply to the motor is stopped as described above, the valve 12 related to the position of the contact point between the nose portion 18b of the cam 18 and the top surface 16a is lifted when the motor is stopped. It is possible to avoid being kept in a state. As described above, according to the control of the present embodiment, it is possible to reliably avoid the interference between the valve 12 and the piston regardless of the abnormal state of the variable valve apparatus 10.

In the second embodiment described above, the “power supply control means” according to the eighth aspect of the present invention is realized by the ECU 40 executing the routine processing shown in FIG. Yes.

Embodiment 3.

Next, Embodiment 3 of the present invention will be described with reference to FIG. 9 to FIG. FIG. 9 is a diagram for explaining the configuration of the torque reduction mechanism 52 provided in the variable valve operating apparatus 50 according to the third embodiment of the present invention. More specifically, FIG. 9 (A) shows a view of the variable valve operating device 50 viewed from the axial direction of the camshaft 22, and FIG. 9 (B) shows the variable valve operating device 50 of FIG. The figure seen from the direction of arrow A in (A) is shown. In FIG. 9, the same components as those shown in FIG. 1 are designated by the same reference numerals, and the description thereof is omitted or simplified.

[0065] The variable valve operating apparatus 50 of the present embodiment is configured in the same manner as the variable valve operating apparatus 10 of the first embodiment described above, except that the torque reducing mechanism 52 shown in Fig. 9 is provided. . The torque reduction mechanism 52 is a mechanism that generates a reduction torque for reducing the drive torque when the cam shaft 22 or the like is driven by the motor 30 or the like. As shown in FIG. 9, the torque reduction mechanism 52 includes an anti-phase cam 54 and an urging mechanism 58 that applies an urging force of a spring 56 to the anti-phase cam 54. The torque reduction mechanism 52 is provided at each end of the two cam shafts 22 and 24 provided in the variable valve operating device 50. Since such a configuration of the torque reduction mechanism 52 is known, a detailed description thereof will be omitted here.

[0066] FIG. 10 is a diagram for explaining a general setting of the reduction torque in the torque reduction mechanism having the same configuration as that of the torque reduction mechanism 52 shown in FIG. The waveform shown by the solid line in FIG. 10 shows the change in the drive torque of the cam shaft during one rotation of the cam shaft when such a torque reduction mechanism is not used. The cam shaft drive torque is mainly the torque acting on the cam shaft based on the urging force of the valve spring, excluding friction between the cam and the valve lifter. For this reason, the drive torque of the camshaft gradually increases as the cam rotates and pushes down the valve while piled on the valve spring force, and shows the maximum value before the maximum lift position. The drive torque of the camshaft then starts to decrease and instantaneously becomes zero at the maximum lift position. After exceeding the maximum lift position, the valve spring reaction force assists the cam rotation. For this reason, the camshaft torque becomes a negative value, and once it reaches the negative peak value, it approaches zero as the valve is closed. <.

[0067] The reduction torque generated by the torque reduction mechanism is generally the valve spring as shown by the waveform shown by the broken line in FIG. 10 which reduces the drive torque of the cam shaft as described above. Based on the urging force, the torque applied to the camshaft is given as a reverse torque. In other words, these torques act so as to cancel each other, as shown in FIG. Such setting of the reduction torque is realized by appropriately adjusting the profile of the anti-phase cam 54 and the biasing force of the spring 56. When such reduced torque is applied, the final camshaft drive torque by the motor is theoretically zero (excluding friction) when the cam is at an arbitrary rotational position.

[0068] As a result, when the torque reduction mechanism is used with the general settings as described above! /, The cam can be in contact with the valve lifter at any position of the nose portion of the cam. Even when the tip of the nose is not in contact with the valve lifter, the torque that rotates the cam in the valve closing direction is not generated in the cam shaft, and the cam may stop with the valve force S lifted. For this reason, there is a concern about interference between the valve and the piston.

[0069] FIG. 11 is a diagram for explaining the setting of the reduced torque generated by the torque reduction mechanism 52 of the present embodiment. In the present embodiment, in order to solve the above problems, the reduced torque generated by the torque reduction mechanism 52 is set as shown in FIG. More specifically, as shown in FIG. 11, the reduction torque generated by the torque reduction mechanism 52 is set to be smaller than the torque acting on the camshaft 22 based on the urging force of the valve spring 17. did. According to such a setting, a deductive torque (a waveform indicated by a thick broken line in FIG. 11), which is a composite value of the camshaft acting torque and the reduced torque, acts in a direction repelling the rotation of the cam 18. It becomes like this. In other words, a sufficient urging force of the valve spring 17 is secured as a 卜 NOREC for rotating the cam 18.

In addition, the subtraction torque force friction between the cam and the valve lifter, friction between the gears arranged between the motor and the camshaft, and resistance to rotation of the camshaft such as the inertia of the motor The reduction torque applied by the torque reduction mechanism 52 is determined so as to be a little larger than the sum of these factors.

[0071] Even when the setting shown in Fig. 11 is adopted, the difference is near the maximum lift position. There will be a place where the drag torque becomes zero. Therefore, in the present embodiment, as in the first embodiment, the shape of the top surface 16a of the valve lifter 16 and the positional relationship between the valve lifter 16 and the cam shaft 22 are configured as shown in FIG. 5 described above. I have to. For this reason, it is possible to distribute the valve spring reaction force to the torque for rotating the cam 18 even at the location where the subtraction torque becomes zero.

According to the configuration of the present embodiment described above, even in the variable valve gear 50 having the torque reduction mechanism 52 for the purpose of reducing the drive torque of the camshaft 22 and the like, a simple configuration can be used when an abnormality occurs. It is possible to reliably avoid the interference between the valve 12 and the piston regardless of the stop position of the cam 18 or the like.

Claims

The scope of the claims

[1] A variable valve operating apparatus for driving a cam shaft provided with a cam for pushing a valve biased in a valve closing direction by a valve spring by a motor,

A valve lifter that comes into contact with the cam is provided between the cam and the valve, and the valve lifter has a tangential direction to the nose tip of the cam as viewed from the axial direction of the cam shaft and the axis of the valve stem. A variable valve operating device comprising a top surface formed so as to be inclined with respect to an orthogonal direction.

[2] The inclination direction of the tangent is directed toward the traveling direction of the contact point between the cam and the valve lifter during forward rotation of the cam, and as a result, the distance force S between the tangent and the bottom surface of the valve lifter decreases. 2. The variable valve operating apparatus for an internal combustion engine according to claim 1, wherein the direction is a direction.

[3] The range according to claim 1 or 2, wherein the top surface is formed in a convex curved surface that is convex toward the cam side when viewed from the axial direction of the cam shaft. Variable valve gear.

[4] An apex where the height from the bottom surface of the valve lifter is the highest on the top surface formed in a convex curved surface projecting toward the cam side, and a contact point between the nose tip and the valve lifter are 4. The variable valve operating apparatus according to claim 3, wherein the variable valve operating apparatus is configured to be separated from each other when viewed in the axial direction of the cam shaft.

[5] The top surface formed in a convex curved shape that is convex toward the cam side is formed so that the height from the bottom surface of the valve lifter is the highest on the central axis of the valve lifter, 4. The cam shaft according to claim 3, wherein the cam shaft is arranged so that the central axis of the cam shaft and the central axis of the valve lifter do not intersect when viewed from the axial direction of the cam shaft. 4. The variable valve operating device according to item 4.

[6] The cam shaft is disposed so that a central axis of the cam shaft intersects an axis of the valve stem when viewed from an axial direction of the cam shaft,

The top surface formed in a convex curved shape that is convex toward the cam side has an apex force S at which the height from the bottom surface of the valve lifter is the highest, as viewed from the axial direction of the cam shaft, 5. The variable valve operating apparatus according to claim 3, wherein the variable valve operating apparatus is formed so as to be offset from the axis.

[7] The variable valve operating apparatus according to [1] or [2], wherein the top surface is an inclined surface having a constant gradient when viewed from the axial direction of the camshaft.

[8] The apparatus further comprises power supply control means for stopping power supply to the motor when a command value given to the motor when the motor drives the camshaft reaches a predetermined value. The variable valve operating apparatus according to any one of claims 1 to 7, wherein:

[9] A torque reduction mechanism that generates a reduction torque that reduces the drive torque of the camshaft is further provided,

The torque reduction mechanism is configured so that the reduced torque is smaller than a torque acting on the camshaft based on an urging force of the valve spring! 9. The variable valve operating apparatus according to any one of items 1 to 8.