JP2007023814A - Variable valve gear for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to change a valve opening characteristic with higher flexibility in a variable valve gear for an internal combustion engine. <P>SOLUTION: A first cam 56 and a second cam 50 are rotatingly driven by a same motor and have the same cam shapes but have different rotational phases with respect to the motor, and the cam shape is symmetrical with respect to a straight line passing through the cam center and cam noses 56a, 50a. With such a cam shape, when the rotational direction of the motor is alternately switched in the case where the first cam 56 drives a valve to open/close using an opening side ramp part 56b out of its two ramp parts 56b, 56c and the second cam 50 drives a valve to open/close using a closing side ramp part 50c out of its two ramp parts 50b, 50c, each of the valves can be operated to be lifted with a smaller lift amount than the maximum lift amount without generating a difference between the lift curves of the two valves. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a variable valve apparatus that opens and closes an intake valve and an exhaust valve of an internal combustion engine with a cam, and more particularly to a variable valve apparatus that uses an electric motor as a drive source for the cam.

  2. Description of the Related Art Conventionally, as described in, for example, Patent Document 1, an internal combustion engine including a variable valve gear that can change valve opening characteristics (lift amount, opening timing, closing timing, etc.) of an intake valve and an exhaust valve has been proposed. . This variable valve operating device drives a cam by an electric motor instead of the power extracted from the crankshaft, and can freely control the rotational speed and direction of the cam independently of the rotation of the crankshaft. it can.

According to the conventional variable valve operating apparatus described above, for example, if the rotational speed of the cam during the valve closing period is increased or decreased, the phase can be changed (phase variable control), and conversely during the valve opening period. If the rotational speed of the cam is increased or decreased, the operating angle can be changed (variable operating angle control). If the cam rotation direction is reversed before the maximum lift amount is reached during the valve opening period, the valve lift amount can be controlled to be smaller than the maximum lift amount (lift amount variable control). . Thus, according to the conventional variable valve operating apparatus, the valve opening characteristic of the valve can be changed with a high degree of freedom.
JP 2004-183612 A JP-A-9-105314

  Incidentally, one electric motor for rotating the cam can be provided for all the cylinders, or can be provided for each cylinder. Further, the cylinders can be divided into a plurality of groups, and one electric motor can be provided for each group. When two cylinders are used as one group, grouping may be performed so that two cams having different rotation phases are driven to rotate by one electric motor. In that case, it is considered that the above-described variable lift amount control can be executed simultaneously for two cylinders if the rotation directions of the electric motor are alternately switched to drive each cam in a swinging manner. Specifically, the cam of one cylinder uses only the ramp portion on the open side during normal rotation of the two ramp portions to drive the valve, and the cam of the other cylinder has a positive polarity. The rotation direction of the electric motor is alternately switched so that the valve is driven to open and close using only the lamp portion on the closed side during rotation.

  However, normally, the shape of the cam used in the valve gear of the internal combustion engine is different on the opening side and the closing side with respect to the cam nose. On the cam opening side, a steeply ramped portion is provided in order to quickly open the valve to reduce the working angle and improve the time area at the same working angle. On the other hand, on the cam closing side, a ramp portion having a gentle slope is provided in order to slowly close the valve to lower the seating speed and reduce vibration and noise during seating.

  For this reason, when the lift amount variable control is executed simultaneously for the two cylinders as described above, the valve of one cylinder is quickly opened and closed by the ramp portion having a steep slope, and the valve of the other cylinder is slowly driven by the ramp portion having a gentle slope. It will be opened and closed. As a result, a difference in valve lift curves causes a difference in intake air amount between cylinders, resulting in torque fluctuations throughout the internal combustion engine.

  As described above, the conventional variable valve device can change the valve opening characteristic with a high degree of freedom. However, if the cam rotation direction is changed, the valve lift curve also changes. There were restrictions in increasing the degree of freedom regarding the valve opening characteristics.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a variable valve operating apparatus for an internal combustion engine that can change the valve opening characteristics of the valve with a higher degree of freedom. To do.

In order to achieve the above object, the first invention provides
A variable valve operating device for an internal combustion engine,
An electric motor capable of switching the rotation direction;
A first cam rotated by the electric motor;
A second cam having the same cam shape as that of the first cam and driven to rotate by the electric motor, the second cam having a rotational phase different from that of the electric motor;
A first valve that is opened and closed by the first cam;
A second valve that is opened and closed by the second cam;
Control means for controlling the rotation of the electric motor,
The first cam and the second cam have a symmetric cam shape with respect to a straight line passing through a cam center and a cam nose.

According to a second invention, in the first invention,
The control means drives the first valve to open / close using the lamp portion on the open side when the electric motor rotates in a predetermined direction, out of the two lamp portions of the first cam, and The rotation direction of the electric motor is alternately changed so that the second valve is driven to open and close using the lamp portion on the closed side when the electric motor rotates in the predetermined direction among the two lamp portions of the two cams. It is characterized by switching.

According to a third invention, in the first or second invention,
The control means is configured such that the opening of the first valve and the opening of the second valve are more initiated than the opening end of the first valve and the opening end of the second valve. It is characterized by increasing the rotational speed of the.

4th invention is 1st or 2nd invention,
The control means may be configured such that the opening end of the first valve and the opening end of the second valve are more open than the start of opening of the first valve and the opening of the second valve. It is characterized in that the rotational speed of the is reduced.

Further, the fifth invention achieves the above object,
A variable valve operating device for an internal combustion engine,
An electric motor capable of switching the rotation direction;
A cam that is rotationally driven by the electric motor;
A valve that is opened and closed by the cam;
Control means for controlling the rotation of the electric motor,
The cam has a symmetric cam shape with respect to a straight line passing through the cam center and the cam nose.

According to a sixth invention, in the fifth invention,
The control means is characterized in that the rotation direction of the electric motor is alternately switched so as to open and close the valve using only one of the two lamp portions of the cam.

According to a seventh invention, in the fifth or sixth invention,
The control means is characterized in that the rotation speed of the electric motor is increased at the beginning of opening of the valve than at the end of opening of the valve.

The eighth invention is the fifth or sixth invention, wherein
The control means is characterized in that the rotation speed of the electric motor is lower at the end of opening of the valve than at the start of opening of the valve.

  According to the first invention, since the first cam and the second cam have a symmetrical cam shape with respect to a straight line passing through the cam center and the cam nose, the cam can be rotated in either the left or right direction. The same valve lift curve can be obtained. In addition, since the electric motor is used as a drive source for rotationally driving each cam, the rotational direction and rotational speed of each cam can be freely set. Therefore, according to the first invention, the valve opening characteristics of the first valve and the second valve can be changed with a higher degree of freedom.

  According to the second invention, the first valve is driven to open and close by using the ramp portion on the opening side of the first cam, and the second valve is used by using the ramp portion on the closing side of the second cam. It is opened and closed. In this way, by opening and closing the valve using only the ramp portion on one side of each cam, each valve can be opened with a smaller lift than when the cam is rotated in one direction and opened and closed using the entire cam. Lifting operation can be performed. In addition, since the first cam and the second cam have the same cam shape and are symmetrical with respect to the straight line passing through the cam center and the cam nose, the different cams (the first cam is the open side, the second cam is Even if the valve is driven to open and close using the ramp portion on the cam closed side, there is no difference between the lift curves of the two valves.

  According to the third aspect of the present invention, the opening operating angle of each valve can be reduced and the time area of the same operating angle can be increased by increasing the rotational speed of the motor at the beginning of opening of each valve than at the end of opening. . Therefore, when the shape of the ramp portion of each cam is a gentle slope that places importance on the seating speed of each valve, it is possible to realize a valve lift curve that opens quickly and closes slowly.

  According to the fourth aspect of the present invention, the opening speed of each valve lowers the rotational speed of the motor than the start of opening, thereby reducing the seating speed of each valve and reducing vibration and noise at the time of seating. Therefore, when the shape of the ramp portion of each cam is steeply inclined with an emphasis on the time area at the same operating angle, it is possible to realize a valve lift curve that opens quickly and closes slowly. .

  According to the fifth aspect of the invention, the valve is driven by a cam having a symmetrical cam shape with respect to a straight line passing through the cam center and the cam nose, so that the same valve lift curve can be obtained regardless of which direction the cam is rotated. Can be obtained. Moreover, since the electric motor is used as a drive source for rotationally driving the cam, the rotational direction and rotational speed of the cam can be freely set. Therefore, according to the fifth aspect, the valve opening characteristic of the valve can be changed with a higher degree of freedom.

  According to the sixth aspect of the present invention, the valve is driven to open and close using only one of the two lamp portions of the cam, thereby rotating the cam in one direction and opening and closing using the entire cam. Each valve can be lifted with a lift amount smaller than that of the case.

  According to the seventh aspect, by increasing the rotational speed of the electric motor at the beginning of opening of the valve than at the end of opening, the opening operating angle of the valve can be reduced and the time area of the same operating angle can be expanded. Accordingly, when the shape of the ramp portion of the cam is a gentle slope that places importance on the seating speed of the valve, it is possible to realize a valve lift curve that opens quickly and closes slowly.

  According to the eighth invention, the opening end of the valve lowers the rotational speed of the electric motor than the beginning of opening, thereby reducing the seating speed of the valve and reducing vibration and noise during the seating. Therefore, when the shape of the ramp portion of the cam is steeply inclined with an emphasis on the time area at the same operating angle, a valve lift curve that opens quickly and closes slowly can be realized.

Embodiment 1 FIG.
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS.

[Configuration of variable valve gear]
FIG. 1 is a perspective view showing a configuration of a variable valve operating apparatus as a first embodiment of the present invention. A variable valve operating apparatus 10 shown in FIG. 1 is an apparatus for driving an intake valve and an exhaust valve of the internal combustion engine 1. Here, it is assumed that the internal combustion engine 1 is configured as an in-line four-cylinder engine. In FIG. 1, # 1 to # 4 represent the first to fourth cylinders of the internal combustion engine 1, respectively. The explosion order in the internal combustion engine 1 is assumed to be # 1 → # 3 → # 4 → # 2 similarly to a general internal combustion engine. In the present embodiment, it is assumed that the variable valve gear 10 functions as a device for driving the intake valve of each cylinder. In FIG. 1, the illustration of the configuration on the exhaust valve side is omitted. 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 internal combustion engine 1 shown in FIG. 1 includes two valves 12 for each cylinder. A valve shaft 14 is fixed to each of the valves 12. A valve lifter 16 is attached to the upper end portion of the valve shaft 14. A biasing force of a valve spring (not shown) acts on the valve shaft 14, and the valve 12 is biased in the valve closing direction by the biasing force.

  A corresponding cam 50, 52, 54 or 56 is arranged 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 cylinder is referred to as a cam 50, and the cam corresponding to the valve lifter 16 disposed in the # 2 cylinder is referred to as a cam 52. The cam corresponding to the valve lifter 16 disposed in the # 3 cylinder is referred to as a cam 54, and the cam corresponding to the valve lifter 16 disposed in the # 4 cylinder is referred to as a cam 56, respectively.

  A cam 50 corresponding to the # 1 cylinder and a cam 56 corresponding to the # 4 cylinder are fixed to the camshaft 22. The cam 52 corresponding to the # 2 cylinder and the cam 54 corresponding to the # 4 cylinder are rotatable to the camshaft 22 and are fixed to the camshaft 24 disposed coaxially with the camshaft 22. ing. That is, in the configuration shown in FIG. 1, the camshaft is shared for each cylinder whose explosion timing differs by 360 ° CA. These camshafts, that is, the camshaft 22 corresponding to the # 1 and # 4 cylinders, and the camshaft 24 corresponding to the # 2 and # 3 cylinders rotate or swing in the circumferential direction independently of each other. It is configured to be able to operate. The camshaft 22 and the camshaft 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 coaxially with the output shaft of the first motor 30. According to 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 camshaft 24. A second output gear 36 is engaged with the second driven gear 32 through an intermediate gear 34. The second output gear 36 is fixed coaxially with the output shaft of the second motor 38. According to such a configuration, the torque of the second motor 38 can be transmitted to the camshaft 24 via these gears 32, 34 and 36.

  FIG. 2 is a view of the camshaft 22 viewed from the axial direction in order to explain the detailed configuration of the camshaft 22 shown in FIG. As described above, the cam 50 for the # 1 cylinder and the cam 56 for the # 4 cylinder are fixed to the camshaft 22. As shown in FIG. 2, the two cams 50 and 56 are arranged such that the cam noses 50 a and 56 a are shifted from each other by 180 ° in the circumferential direction of the camshaft 22.

  As shown in FIG. 2, the cam 50 has two ramp portions 50b and 50c extending from the basic circle portion to the cam nose 50a. Here, the side that contacts the valve lifter 16 first when the camshaft 22 rotates forward, that is, the lamp portion that opens the valve 12 (# 1) is referred to as the opening side ramp portion 50b, and the side that contacts the valve lifter 16 later. That is, the lamp portion on the side that closes the bulb 12 is referred to as a closed-side lamp portion 50c. Similarly, the lamp portion on the side of the cam 56 that opens the valve 12 (# 4) is referred to as an open-side lamp portion 56b, and the lamp portion on the side that closes the valve 12 is referred to as a closed-side lamp portion 56c.

  The two cams 50 and 56 have the same shape, and have a symmetrical cam shape with respect to a straight line passing through the cam center and the cam nose. FIG. 3 is a diagram showing a cam lift curve of the cam 50 for the # 1 cylinder. In FIG. 3, the horizontal axis indicates the circumferential position of the cam, and the vertical axis indicates the cam height (height relative to the cam base circle). Further, in FIG. 3, a cam lift curve is shown with a straight line connecting the cam center and the cam nose 50a as the Y axis. In FIG. 3, the left side with respect to the Y axis shows the cam lift curve of the open side ramp portion 50b, and the right side with respect to the Y axis shows the cam lift curve of the closed side ramp portion 50c. Since the cam 50 is symmetrical with respect to a straight line passing through the cam center and the cam nose 50a, as shown in FIG. 3, the cam lift curve of the open side ramp portion 50b and the cam lift curve of the close side ramp portion 50c are left and right with respect to the Y axis. It becomes symmetric. Although illustration is omitted, the cam lift curve of the cam 56 for the # 4 cylinder also becomes a cam lift curve as shown in FIG. 3 like the cam 50 for the # 1 cylinder.

  Here, although detailed explanation thereof is omitted, in the camshaft 24 corresponding to the # 2 cylinder and the # 3 cylinder, the cam 52 for the # 2 cylinder and the cam 54 for the # 3 cylinder are 180 °. They are arranged so as to be displaced. The cams 52 and 54 have the same shape as the cam 50 for the # 1 cylinder and the cam 56 for the # 4 cylinder, and have a symmetrical cam shape with respect to a straight line passing through the cam center and the cam nose.

  The operation of the variable valve gear 10 is controlled by 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 the first motor 30 and the second motor 38 are connected to the ECU 40. The ECU 40 gives drive commands to the first motor 30 and the second motor 38 based on the sensor outputs, and controls the rotation of the motors 30 and 38.

[Operation of variable valve gear]
Next, the operation of the variable valve apparatus 10 will be described with reference to FIG. Here, the case where the cam shaft 22 is driven by the first motor 30 will be described as an example.

  According to the variable valve operating apparatus 10, the first motor 30 changes the phase of the camshaft 22 relative to the crankshaft to change the valve opening characteristics of the valve 12 as in the example shown in FIG. 4 below. It is possible to change variously. In this specification, the “valve opening characteristic” of the valve 12 is a generic expression of the lift amount (maximum lift amount), the opening timing, and the closing timing of the valve 12, and further, the opening timing and the closing timing. And the phase determined by determining the opening timing (or closing timing) while the operating angle remains constant.

  FIG. 4 is a specific example of the change of the valve opening characteristic of the valve 12 realized by the variable valve apparatus 10. More specifically, the waveform shown by the solid line in FIG. 4 is a valve lift curve obtained when the camshaft 22 is continuously rotated in the forward rotation direction at a basic speed (half the speed of the crankshaft). Show. Moreover, the waveform shown with a dashed-two dotted line in FIG. 4 has shown the valve lift curve after the operation | movement of the camshaft 22 was changed. The horizontal axis of the valve lift curve in FIG. 4 is the crank angle.

  First, the operation of changing the “phase” shown in FIG. When the drive speed of the camshaft 22 is increased from the basic speed during the valve closing period of the valve 12, the phase of the camshaft 22 relative to the crankshaft changes relatively to the advance side. For this reason, the phase shown in FIG. 4A can be changed. After changing the phase, the desired phase can be maintained by returning the driving speed of the camshaft 22 to the basic speed. Further, if the drive speed is decelerated from the basic speed while the valve 12 is closed, the phase can be changed to the retard side.

  The change of the “working angle” shown in FIG. 4B can be realized by making the driving speed of the camshaft 22 during the valve opening period higher than the basic speed. However, since the driving speed during the valve opening period is increased, the driving speed during the valve closing period is made slower than the basic speed, and the ratio of the rotation period of the camshaft 22 to the rotation period of the crankshaft is 2: 1. Do not slip. Further, if the driving speed during the valve opening period is made slower than the basic speed, the operating angle can be made larger than the basic waveform shown by the solid line. In this case, the drive speed during the valve closing period is made higher than the basic speed by the amount of the drive speed during the valve opening period being delayed.

  Next, the operation of changing the “working angle & lift amount” shown in FIG. This changing operation is an example in which the lift amount of the valve 12 is limited to be smaller than the maximum lift amount. This changing operation can be realized by controlling the drive of the camshaft 22 as shown in FIG. FIG. 5 shows the operation of the cams 50 and 56 for realizing the operation of changing the “working angle & lift amount”. In this changing operation, the driving direction of the camshaft 22 is alternately switched between the normal rotation direction and the reverse rotation direction, and the cams 50 and 56 are periodically swung.

  In the operation of changing the “working angle & lift amount”, first, as shown in FIG. 5A, the camshaft 22 rotates in the forward rotation direction, and the # 56 cylinder cam 56 is at its open side ramp portion 56b. The first motor 30 is stopped while the valve lifter 16 (# 4) is being pushed down. Thereafter, the rotation direction of the first motor 30 is switched, and the camshaft 22 is rotated in the reverse rotation direction as shown in FIG. As a result, the cam 56 swings while only the open side ramp portion 56b of the two ramp portions 56b, 56c is in contact with the valve lifter 16 (# 4), and the # 12 cylinder valve 12 is The lift operation is performed while drawing a valve lift curve determined by the cam lift curve of the open side ramp portion 56b.

  When the camshaft 22 is further rotated in the reverse rotation direction, as shown in FIG. 5 (c), the # 1 cylinder cam 50 pushes down the valve lifter 16 (# 1) at its closing ramp portion 50c. Go. On the way, the first motor 30 is stopped. Then, the rotation direction of the first motor 30 is switched again, and the camshaft 22 is rotated in the normal rotation direction as shown in FIG. As a result, the cam 50 swings while only the closing lamp portion 50c of the two ramp portions 50b, 50c is in contact with the valve lifter 16 (# 1), and the # 1 cylinder valve 12 The lift operation is performed while drawing a valve lift curve determined by the cam lift curve of the closed ramp portion 50c.

  By performing the above series of operations continuously and periodically swinging the cams 50 and 56, the lift amounts of the valves 12 of the # 1 cylinder and the # 4 cylinder can be simultaneously changed. At this time, the lift amount of the valve 12 can be appropriately selected by appropriately changing the swing amount of the cams 50 and 56. Further, when the cams 50 and 56 are swung, by appropriately adjusting the driving speed of the first motor 30, as shown in FIG. Only the “amount” can be changed. It should be noted that the swing cycle of the cams 50 and 56 during the “operation angle & lift amount” changing operation and the “lift amount” changing operation is set to twice the rotation cycle of the crankshaft.

  As described above, by alternately switching the rotation direction of the first motor 30 and periodically swinging the cams 50 and 56, the valve 12 for the # 4 cylinder uses the ramp portion 56 b on the opening side of the cam 56. The # 1 cylinder valve 12 can be driven to open and close using the ramp portion 50c on the closing side of the cam 50. By opening and closing the valve 12 using only the ramp portions 50c and 56b on one side of each of the cams 50 and 56, the camshaft 22 is rotated only in the forward rotation direction, and the cams 50 and 56 are used for opening and closing. Thus, the valve 12 can be lifted with a lift amount smaller than that of the case.

  In addition, since the two cams 50 and 56 that are driven to swing simultaneously have the same cam shape and symmetrical cam shapes with respect to the straight line passing through the cam center and the cam nose, the ramp portions 50c and 56b on different sides are used. Even if each valve 12 is driven to open and close, there is no difference in the valve lift curve. Therefore, even when the lift amount of the valve 12 is changed, there is no difference in the intake air amount between the # 1 cylinder and the # 4 cylinder.

  As described above, according to the variable valve operating apparatus 10 of the present embodiment, the operation of the cams 50 and 56 can be changed variously by appropriately controlling the rotational speed of the camshaft 22 by the first motor 30. Can do. Further, the cams 50 and 56 have a symmetrical cam shape with respect to a straight line passing through the cam center and the cam nose, and the same valve lift curve can be obtained even if the cams 50 and 56 are rotated in either the left or right direction. Therefore, according to the variable valve operating apparatus 10 of the present embodiment, there is no restriction on the rotation direction of the camshaft 22, and the operation of the cams 50 and 56 is variously changed by appropriately controlling the rotation direction of the camshaft 22. You can also. Thereby, the valve opening characteristic of the valve 12 can be changed with a high degree of freedom.

  In this embodiment, in the lift amount changing operation, the # 4 cylinder cam 56 uses the opening side ramp portion 56b, and the # 1 cylinder cam 50 uses the closing side ramp portion 50c. Although it is used, the opposite lamp portions 50b and 56c may be used. Which ramp unit is used may be selected according to the rotational position of each of the cams 50 and 56 when a command for changing the lift amount is issued.

  Also, in the # 2 cylinder and the # 3 cylinder, the two cams 52 and 54 have the same shape and have a symmetrical cam shape with respect to a straight line passing through the cam center and the cam nose. The same valve lift curve can be obtained by rotating in this direction. Accordingly, although detailed description thereof is omitted here, the cams 52, # 3 and # 3 are also controlled by appropriately controlling the rotational speed and direction of the camshaft 24 by the second motor 38. 54 operation | movement can be changed variously, and, thereby, the valve opening characteristic of the valve | bulb 12 can be changed with a high degree of freedom.

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

  The configuration of the variable valve operating apparatus as the second embodiment of the present invention is shown in FIG. 1 as in the first embodiment. The present embodiment is characterized in that the ECU 40 controls the rotational speeds of the motors 30 and 38. FIG. 6 shows a valve lift curve realized by controlling the rotational speeds of the motors 30 and 38 by the ECU 40.

  As described in the first embodiment, each of the cams 50, 52, 54, and 56 has a symmetrical cam shape with respect to a straight line passing through the cam center and the cam nose. Therefore, when the motors 30 and 38 are rotated at a constant rotational speed, the opening start speed of the valve 12 and the opening end speed coincide with each other. However, there is a demand for an internal combustion engine to quickly open the valve 12 to reduce the working angle and improve the time area at the same working angle. There is also a demand to slowly close the valve 12 to lower the seating speed and reduce vibration and noise during seating. Since these two requirements are contradictory, if the cam shape is determined so as to meet one of the requirements, the other requirement cannot be satisfied.

Therefore, in the present embodiment, the request for quickly opening the valve 12 is solved by selecting the cam shape, and the request for slowly closing the valve 12 is solved by controlling the rotational speeds of the motors 30 and 38. I am trying. Specifically, the shape of the ramp portion of each of the cams 50, 52, 54, and 56 is steeply inclined with an emphasis on the time area at the same operating angle on both the open side and the close side. In addition, the rotational speed NC _close of the motors 30 and 38 at the end of opening of the valve 12 is made lower than the rotational speed NC _{open at the} start of opening of the valve 12.

  According to this, as shown by a solid line in FIG. 6, a valve lift curve that opens quickly and closes slowly can be realized. As a result, it is possible to reduce the seating speed of the valve 12 and reduce vibration and noise during seating while reducing the opening working angle of the valve 12 and increasing the time area of the same working angle. In the case where the rotational speeds of the motors 30 and 38 are not changed between the end of opening of the valve 12 and the start of opening, the lift curve at the end of opening of the valve 12 is as shown by a broken line in FIG.

  In the above control, not only when the cams 50, 52, 54, 56 are rotationally driven in the forward rotation direction, the cams 50, 52, 54, 56 are driven to swing by alternately switching the rotational directions of the motors 30, 38. It can also be applied to.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.

  As in the second embodiment, the variable valve operating apparatus according to the third embodiment of the present invention is configured such that the request for the opening speed of the valve 12 and the request for the closing speed are selected according to the selection of the cam shape and the rotation speed of the motors 30 and 38. It is characterized by making it compatible with the control. FIG. 7 shows a valve lift curve realized by controlling the rotational speeds of the motors 30 and 38 by the ECU 40.

In the present embodiment, contrary to the second embodiment, the request for slowly closing the valve 12 is solved by selecting the cam shape, and the request for opening the valve 12 quickly is achieved by the motors 30, 38. We are trying to solve this problem by controlling the rotation speed. Specifically, the shape of the ramp portion of each cam 50, 52, 54, 56 is a gentle slope that places importance on the seating speed of the bulb 12 on both the open side and the close side. Then, the rotational speed NC _open of the motors 30 and 38 at the beginning of opening of the valve 12 is made higher than the rotational speed NC _close at the end of opening of the valve 12.

  According to this, as shown by the solid line in FIG. 7, it is possible to realize a valve lift curve that opens quickly and closes slowly as in the second embodiment. As a result, it is possible to reduce the seating speed of the valve 12 and reduce vibration and noise during seating while reducing the opening working angle of the valve 12 and increasing the time area of the same working angle. When the rotational speeds of the motors 30 and 38 are not changed between the end of opening of the valve 12 and the start of opening, the lift curve at the start of opening of the valve 12 is shown by a broken line in FIG.

  In the above control, not only when the cams 50, 52, 54, 56 are rotationally driven in the forward rotation direction, the cams 50, 52, 54, 56 are driven to swing by alternately switching the rotational directions of the motors 30, 38. It can also be applied to.

Others.
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  In the above embodiment, the cam for two cylinders is rotationally driven by one motor, but the cam for one cylinder may be rotationally driven by one motor. Also in this case, the shape of the cam is symmetrical with respect to a straight line passing through the cam center and the cam nose. According to this, since the same valve lift curve can be obtained regardless of which direction the cam is rotated, the cam rotation direction and rotation speed can be freely set, and the valve opening characteristics are high. It can be changed with a degree of freedom.

It is a perspective view which shows the structure of the variable valve apparatus of Embodiment 1 of this invention. FIG. 2 is a view of the camshaft as viewed from the axial direction in order to explain the detailed configuration of the camshaft shown in FIG. 1. It is a figure which shows the cam lift curve of the cam shown in FIG. It is a specific example of the change of the valve opening characteristic of the valve | bulb implement | achieved by the variable valve apparatus shown in FIG. It is a figure which shows the rocking | fluctuation operation | movement of the cam for opening and closing a valve with small lift amount. The valve lift curve implement | achieved by the rotational speed control of the motor concerning Embodiment 2 of this invention is shown. 10 shows a valve lift curve realized by controlling the rotational speed of the motor according to the third embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 10 Variable valve apparatus 12 Valve 16 Valve lifters 22, 24 Camshaft 30 First motor 38 Second motor 40 ECU (Electronic Control Unit)
50, 52, 54, 56 Cam 50a, 56c Cam nose 50b, 56b Open side lamp part 50c, 56c Close side lamp part

Claims (8)

An electric motor capable of switching the rotation direction;
A first cam rotated by the electric motor;
A second cam having the same cam shape as that of the first cam and driven to rotate by the electric motor, the second cam having a rotational phase different from that of the electric motor;
A first valve that is opened and closed by the first cam;
A second valve that is opened and closed by the second cam;
Control means for controlling the rotation of the electric motor,
The variable valve operating apparatus for an internal combustion engine, wherein the first cam and the second cam have a symmetrical cam shape with respect to a straight line passing through a cam center and a cam nose.   The control means drives the first valve to open / close using the lamp portion on the open side when the electric motor rotates in a predetermined direction, out of the two lamp portions of the first cam, and The rotation direction of the electric motor is alternately changed so that the second valve is driven to open and close using the lamp portion on the closed side when the electric motor rotates in the predetermined direction among the two lamp portions of the two cams. 2. The variable valve operating apparatus for an internal combustion engine according to claim 1, wherein switching is performed.   The control means is configured such that the opening of the first valve and the opening of the second valve are more initiated than the opening end of the first valve and the opening end of the second valve. 3. The variable valve operating apparatus for an internal combustion engine according to claim 1, wherein the rotational speed of the internal combustion engine is increased.   The control means may be configured such that the opening end of the first valve and the opening end of the second valve are more open than the start of opening of the first valve and the opening of the second valve. 3. The variable valve operating apparatus for an internal combustion engine according to claim 1, wherein the rotational speed of the internal combustion engine is reduced. An electric motor capable of switching the rotation direction;
A cam that is rotationally driven by the electric motor;
A valve that is opened and closed by the cam;
Control means for controlling the rotation of the electric motor,
The variable valve operating device for an internal combustion engine, wherein the cam has a symmetrical cam shape with respect to a straight line passing through a cam center and a cam nose.   The said control means switches the rotation direction of the said electric motor alternately so that the said valve | bulb may be opened and closed using only the lamp part of one side among the two lamp parts which the said cam has. 6. A variable valve operating apparatus for an internal combustion engine according to claim 5.   The variable valve operating apparatus for an internal combustion engine according to claim 5 or 6, wherein the control means increases the rotational speed of the electric motor at the beginning of opening of the valve than at the end of opening of the valve.   The variable valve operating apparatus for an internal combustion engine according to claim 5 or 6, wherein the control means lowers the rotational speed of the electric motor at the end of opening of the valve than at the start of opening of the valve.

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