JP2008019876A - Valve gear for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve gear for an internal combustion engine which limits electric power consumption and rated output demanded by a motor for driving a cam mechanism. <P>SOLUTION: Valve gears 11A, 11B for the internal combustion engine convert rotary motion of the motor 12 to linear motion by a cam mechanism 14 including two cams 21 provided rotatably as one body with a cam shaft 20, and drive valve means for opening and closing a cylinder with resisting a valve spring 28. A torque reducing mechanism 30 applying anti-torque acting to reduce torque applied on the cam mechanism 14 from the valve spring when the valve means is driven, is provided between the two cams 21. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a valve gear for an internal combustion engine.

An intake valve and an exhaust valve of a general internal combustion engine are opened and closed by power extracted from a crankshaft of the internal combustion engine. In recent years, attempts have been made to open and close intake valves and exhaust valves with an electric motor. For example, a valve gear that opens and closes an intake valve by rotating a camshaft with a stepping motor has been proposed (Patent Document 1). In addition, there is Patent Document 2 as a prior art document related to the present invention.
JP-A-8-177536 JP 59-68509 A

  When the cam mechanism is driven by an electric motor to open and close the intake valve and the exhaust valve, the torque applied to the cam mechanism by the repulsive force of the valve spring provided in each valve (hereinafter referred to as valve spring torque) is resisted. It is necessary to output the driving force from the electric motor. For this reason, when the valve spring torque increases, the power consumption increases and the motor rating increases.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a valve operating device for an internal combustion engine that can suppress a rated output required for an electric motor for driving a cam mechanism and its power consumption.

  The valve operating apparatus for an internal combustion engine according to the present invention converts a rotary motion of an electric motor into a linear motion by a cam mechanism having a plurality of cams provided so as to rotate integrally with a camshaft, and provides a valve means for opening and closing a cylinder as a valve. In a valve operating apparatus for an internal combustion engine that is driven against a spring, an anti-torque acting to reduce the torque applied from the valve spring to the cam mechanism when the valve means is driven is added to the cam mechanism. And the torque reduction mechanism is disposed between the plurality of cams to solve the above-described problem.

  In the valve operating apparatus of the present invention, when the cam mechanism opens and closes the valve means against the reaction force of the valve spring, torque that periodically varies in synchronization with the opening and closing movement of the valve is added to the cam mechanism. . When the torque reduction mechanism adds a counter torque that cancels this torque to the cam mechanism, the torque acting as a load on the electric motor can be reduced, and fluctuations thereof can also be suppressed. Further, since the torque reduction mechanism is arranged between the plurality of cams, the torque that the camshaft bears between the torque reduction mechanism and the cam as compared with the case where the torque reduction mechanism is not arranged as such. The shaft diameter of the camshaft can be reduced by reducing the diameter. If the shaft diameter of the cam shaft is reduced, the moment of inertia of the cam shaft is also reduced, and the response of the motor is improved.

  In the valve gear according to the present invention, the torque reduction mechanism rotates in conjunction with a rotational speed that is 1 / N (where N is an integer) times the rotational speed of the cam of the cam mechanism, and the cam surface is on the surface. An anti-phase cam formed on the cam surface, a cam pressing member that contacts the cam surface, and a biasing member that biases the cam pressing member toward the cam surface of the anti-phase cam. The cam surface contour may be set such that a counter torque that cancels a valve spring torque applied to the cam mechanism by a reaction force of the valve spring is applied from the biasing member to the anti-phase cam. . According to such a configuration, an anti-torque that cancels the valve spring torque can be applied by a simple configuration in which an anti-phase cam is provided and the pressing member is brought into contact with the cam surface of the cam and pressed by the urging member. it can.

  The torque reduction mechanism rotates in conjunction with a rotational speed that is 1 / N (where N is an integer) times the rotational speed of the cam of the cam mechanism, and has an antiphase in which a cam surface is formed on the outer periphery. A cam, a cam pressing member that contacts the cam surface, and a biasing member that biases the cam pressing member toward the cam surface of the anti-phase cam, the contour of the cam surface of the anti-phase cam The counter torque that counteracts the combined torque obtained by combining the valve spring torque applied to the cam mechanism by the reaction force of the valve spring and the inertia torque added to the cam mechanism as the valve means moves is the The biasing member may be set to be added to the antiphase cam. In this case, since the counter torque is set in consideration of the inertia torque, the fluctuation of the torque acting as a load on the electric motor can be further suppressed. As a result, the control accuracy of the valve means can be improved especially at the time of high rotation of the internal combustion engine where the inertia torque becomes large, and the intake or exhaust characteristic of the internal combustion engine can be accurately controlled to the target characteristic. Even when the engine speed is low, the operating characteristics of the intake valve or the exhaust valve can be changed in a more open direction, and thereby the intake efficiency and exhaust efficiency can be sufficiently improved at the time of low speed.

  In the valve gear of the present invention, the cam surface to be provided on the anti-phase cam of the torque reduction mechanism can be characterized by the anti-torque change characteristic added by the present invention. That is, in the valve operating apparatus according to the present invention, the cam of the cam mechanism is positioned on the valve in the circumferential direction of the cam of the cam mechanism when the cam mechanism gives a maximum lift amount to the valve means. While located on the side pushed back in the direction opposite to the rotation direction by the reaction force of the spring, the counter torque applied from the biasing member acts in the direction to push out the anti-phase cam in the rotation direction, and the cam mechanism While the cam is positioned on the side pushed in the rotational direction by the reaction force of the valve spring, the anti-phase is applied so that the anti-torque acts in a direction to push the anti-phase cam back in the direction opposite to the rotational direction. The contour of the cam surface of the cam may be set.

  In particular, when the inertia torque is taken into consideration, the cam of the cam mechanism is delimited by the circumferential position of the cam of the cam mechanism when the cam mechanism gives the maximum lift amount to the valve means. While positioned on the side pushed back in the direction opposite to the rotation direction by the reaction force of the valve spring, the counter-torque applied from the biasing member acts in a direction to push the anti-phase cam in the rotation direction, While the cam of the cam mechanism is positioned on the side pushed in the rotation direction by the reaction force of the valve spring, the counter torque acts in a direction to push the anti-phase cam back in the direction opposite to the rotation direction, and the cam While the cam of the cam mechanism is positioned within a range in which the lift speed increases from the position where the mechanism gives the maximum lift speed to the valve means, the valve While the counter torque relatively larger than the counter torque necessary for canceling only the ring torque acts on the anti-phase cam, the cam mechanism cam is positioned in a range where the lift speed decreases. The cam surface contour of the anti-phase cam may be set so that a counter-torque that is relatively smaller than the counter-torque required to cancel only the valve spring torque acts on the anti-phase cam.

  In the valve gear of the present invention, the torque reduction mechanism rotates in conjunction with a rotation speed of 1 / N times (where N is an integer) with respect to the cam rotation speed of the cam mechanism, and the cam surface is on the surface. And a biasing member that biases the cam retaining member toward the cam surface of the opposite phase cam, and the biasing member. The compression reaction force of the member may be set to be equal to the product of the compression reaction force of the valve spring and the number of the valve means. By setting the compression reaction force of the biasing member of the torque reduction mechanism in this way, the lift characteristics of the intake valve or the exhaust valve by the anti-phase cam and the cam can be matched with each other. Accordingly, since the anti-phase cam profile can be set based on the smooth profile of the cam, there is no possibility that the radius of curvature of the anti-phase cam profile is extremely reduced.

  Further, in the valve gear according to the present invention, the torque reduction mechanism rotates in conjunction with a rotational speed of 1 / N times (where N ≧ 2 is an integer) with respect to the rotational speed of the cam of the cam mechanism, You may comprise the antiphase cam by which the cam surface was formed in the surface. In this case, the rotational speed of the antiphase cam can be reduced with respect to the rotational speed of the cam.

  In the above aspect of the present invention, the concept of “cancellation” includes both the case where the torque acting on the cam mechanism is reduced by the counter torque and the case where the torque is completely eliminated.

  According to the present invention, the torque acting on the cam mechanism from the valve spring can be reduced by the counter-torque applied to the cam mechanism by the torque reducing mechanism, so that the torque acting as a load on the motor is reduced and the torque is reduced. Variations can also be suppressed. Accordingly, the output required for the electric motor to drive the cam mechanism can be reduced, the power consumption of the electric motor can be suppressed, and the rated output required for the electric motor can be reduced. Thereby, it becomes possible to use a small electric motor compared with the case where a torque reduction mechanism is abbreviate | omitted. Further, since the torque reduction mechanism is arranged between the plurality of cams, the torque that the camshaft bears between the torque reduction mechanism and the cam as compared with the case where the torque reduction mechanism is not arranged as such. The shaft diameter of the camshaft can be reduced by reducing the diameter. As a result, the moment of inertia of the camshaft is reduced and the responsiveness of the motor is improved.

(First form)
FIG. 1 shows one embodiment of the valve gear of the present invention. 1 are incorporated in a multi-cylinder reciprocating internal combustion engine. In this internal combustion engine, two intake valves (valve means) 2 of one cylinder 1 are driven by one valve operating device 11A, and two exhaust valves (valve means) 3 of the same cylinder 1 are driven differently. The valve device 11B is driven to open and close. The other cylinders (not shown) are similarly driven to open and close by valve gears 11A and 11B having different intake valves and exhaust valves. The intake-side valve operating device 11A and the exhaust-side valve operating device 11B basically have the same configuration, and the intake-side valve operating device 11A will be described below.

  The intake side valve gear 11A includes an electric motor (hereinafter referred to as a motor) 12 as a drive source, a gear train 13 as a transmission mechanism for transmitting the rotational motion of the motor 12, and the rotation transmitted from the gear train 13. And a cam mechanism 14 for converting the movement into a linear opening / closing movement of the intake valve 2. As the motor 12, a DC brushless motor or the like capable of controlling the rotation speed is used. The motor 12 incorporates a position detection sensor (not shown) such as a resolver and a rotary encoder for detecting the rotational position. The gear train 13 transmits the rotation of the motor gear 15 attached to the output shaft (not shown) of the motor 12 to the cam drive gear 17 via the intermediate gear 16. The gear train 13 may be configured such that the motor gear 15 and the cam drive gear 17 rotate at equal speeds, or may be configured to increase or decrease the speed of the cam drive gear 17 relative to the motor gear 15. .

  As shown in FIG. 2, the cam mechanism 14 includes a cam shaft 20 provided coaxially with the cam drive gear 17 so as to be integrally rotatable, and two cams 21 provided integrally with the cam shaft 20. A pair of rocker arms 24 are provided corresponding to the respective cams 21 so as to be swingable around the rocker arm shafts 23. The cam 21 is formed as a kind of plate cam in which a nose 21a is formed by inflating a part of an arc-shaped base circle 21b coaxial with the cam shaft 20 radially outward. The profile of the cam 21 is set so that a negative curvature does not occur over the entire circumference, that is, a convex curved surface is drawn outward in the radial direction.

  Each cam 21 faces one end 24 a of the rocker arm 24. Each intake valve 2 is urged toward the rocker arm 24 by the compression reaction force of the valve spring 28, whereby the intake valve 2 comes into close contact with the valve seat (not shown) of the intake port and the intake port is closed. The other end 24 b of the rocker arm 24 is in contact with the adjuster 29. When the adjuster 29 pushes up the other end 24 b of the rocker arm 24, the rocker arm 24 is kept in a state where its one end 24 a is in contact with the upper end of the intake valve 2.

  In the cam mechanism 14 described above, when the rotational movement of the motor 12 is transmitted to the cam shaft 20 via the gear train 13, the cam 21 rotates integrally with the cam shaft 20 and the nose 21 a passes over the rocker arm 24. The rocker arm 24 swings around the rocker arm shaft 23 within a certain range. As a result, the one end 24 a of the rocker arm 24 is pushed down, and the intake valve 2 is driven to open and close against the valve spring 28.

  As shown in FIG. 1, a torque reduction mechanism 30 is provided in the valve gear 11A. The torque reduction mechanism 30 is provided to reduce a torque (referred to as a valve spring torque) acting on the cam mechanism 14 based on a force with which the valve spring 28 pushes the intake valve 2 back in the closing direction. As shown in detail in FIG. 3, the torque reduction mechanism 30 includes an antiphase cam 31 that can rotate integrally with the camshaft 20, and a torque applying device 32 that is disposed to face the antiphase cam 31. . The outer peripheral surface of the antiphase cam 31 is configured as a cam surface 31a. The torque applying device 32 is compressed between the housing 33, a lifter 34 as a pressing member accommodated in the housing 33 so as to be able to protrude from the housing 33 toward the antiphase cam 31, and between the lifter 34 and the housing 33. And a spring 35 as an urging member that is mounted in a state and presses the lifter 34 against the cam surface 31 a of the anti-phase cam 31.

  As shown by a solid line in FIG. 4, the cam surface 31a of the anti-phase cam 31 has an arc portion 31b extending in a circular arc having a constant radius coaxial with the camshaft 20 (referred to as a base circle), and the arc portion. And a receding portion 31c that recedes more toward the center than 31b. The shape of the cam surface 31a (cam profile) is set based on the valve spring torque. Hereinafter, the design of the cam surface 31a will be described.

The valve spring torque Tv (N · m) is obtained when the compression reaction force of the valve spring 28 is Fs (N) and the lift speed of the intake valve 2 when the camshaft 20 rotates by a unit angle is Vv (m / rad). Is calculated from the following equation (1).
[Equation 1]

      Tv = Fs × Vv (1)

  Since the lift speed Vv varies depending on the rotational speed of the internal combustion engine, it is necessary to use the lift speed Vv at any rotational speed as a representative. Since the valve spring torque Tv increases as the lift speed Vv increases, it is desirable to use the lift speed Vv when the internal combustion engine is rotating at a speed as high as possible in order to reduce the absolute load of the motor 12. It is preferable to use the lift speed Vv at the maximum rotational speed allowed in the internal combustion engine.

  For example, there is a correlation as shown in FIG. 5 between the compression reaction force Fs and the lift speed Vv and the phase of the cam 21 (cam angle). In this example, with respect to the compression reaction force Fs, the direction in which the intake valve 2 is pushed back to the closed position is the positive direction, and the lift speed Vv is the speed in the direction in which the intake valve 2 operates in the positive direction. Further, the valve spring torque has a positive direction in which the cam 21 is pushed back in the direction opposite to the rotation direction by the motor 12. As shown in FIG. 5, the lift speed Vv of the intake valve 2 starts to rise from a position P1 where the lift (opening operation) is started, and reaches a peak during the lift. The lift speed Vv returns to zero at the vertical axis position P2 in FIG. 5 where the maximum lift amount of the intake valve 2 is obtained, that is, at the position where the tip of the nose 21a of the cam 21 reaches the contact point with the cam follower 25. The lift speed Vv reaches a negative peak while the intake valve 2 is closed, and the lift speed Vv returns to zero at the position P3 where the intake valve 2 is completely closed. Note that the changes in the lift speed Vv are equal to each other in the two intake valves 2.

  On the other hand, since the valve spring 28 is somewhat compressed even in the initial state in which the intake valve 2 is completely closed, the compression reaction force Fs has a constant initial value in the positive direction in the initial state. The compression reaction force Fs gradually rises from the initial value from the position P1 at which the intake valve 2 opens, and the compression reaction force Fs reaches a peak at the maximum lift position P2. The compression reaction force Fs gradually decreases toward the initial value from the maximum lift position P2 to the position P3 where the intake valve 2 is completely closed. By multiplying the lift speed Vv and the compression reaction force Fs, the valve spring torque Tv as shown by the solid line in FIG. 5 is obtained. The waveform of the valve spring torque Tv is such that the positive and negative peaks are biased to the maximum lift position P2 as compared with the waveform of the lift speed Vv.

  In order to cancel the valve spring torque Tv acting on the cam mechanism 14, a counter-torque complementary to the camshaft 20 is added in reverse phase to the valve spring torque Tv as shown by the broken line in FIG. do it. Such a counter torque is such that the cam 21 is pushed back in the direction opposite to the rotational direction by the reaction force of the valve spring 28 at the position P2 of the cam 21 where the cam mechanism 14 gives the maximum lift amount to the intake valve 2. (P1 to P2) acts in the direction in which the anti-phase cam 31 is pushed in the rotational direction, and the cam 21 is located on the side pushed in the rotational direction by the reaction force of the valve spring 28 ( P2 to P3) act in a direction in which the antiphase cam 31 is pushed back in the direction opposite to the rotation direction.

  Since the reaction torque applied by the torque reduction mechanism 30 is given by the product of the compression reaction force of the spring 35 and the lift speed of the lifter 34, first, the compression reaction force (spring force) of the spring 35 is set appropriately, as shown in FIG. The lift speed of the lifter 34 by the anti-phase cam 31 can be obtained by dividing the reverse phase torque shown in FIG. Then, if the obtained lift speed is integrated, the lift amount of the anti-phase cam 31 with respect to the phase of the cam 21 can be acquired, and the shape (profile) of the cam surface 31a of the anti-phase cam 31 can be determined from the acquired lift amount. . The profile of the cam surface 31a indicated by the solid line in FIG. 4 is obtained by such a procedure.

  Further, when the antiphase cam 31 is attached to the camshaft 20, the antiphase cam 31 is set so that the lifter 34 is at the lowest position of the retracted portion 31c of the cam surface 31a when the lift amount of the intake valve 2 is maximized. May be positioned in the circumferential direction. As described above, by setting the profile of the anti-phase cam 31 and the circumferential mounting position with respect to the cam shaft 20, torque that cancels the valve spring torque Tv can be applied from the torque reduction mechanism 30 to the cam mechanism 14. . As a result, the output required for the motor 12 can be reduced, the power consumption of the motor 12 can be reduced, and the compact motor 12 with a small rated output can be used.

  In the valve operating apparatus 11A described above, the valve spring torque applied from each of the valve springs 28 of the two intake valves 2 is canceled by the torque applied to the single anti-phase cam 31. Therefore, when designing the cam surface 31a of the anti-phase cam 31, the sum of the compression reaction forces of the two valve springs 28 is used as the compression reaction force Fs.

  Although the valve gear 11A for driving the intake valve 2 has been described above, the torque reduction mechanism 30 can be similarly provided for the valve gear 11B for driving the exhaust valve 3. When a plurality of cams 21 are provided on one cam shaft 20, a single anti-phase cam 31 may be provided on the cam shaft 20, or the same number of anti-phase cams 31 as the cam 21 may be provided. Good. In the valve operating apparatus 11B, when only one anti-phase cam 31 is provided for the plurality of cams 21, the sum of the compression reaction forces of the valve springs 28 is taken as the compression reaction force Fs as described above, and the profile of the cam surface 31a. Should be designed. When the same number of anti-phase cams 31 as the cams 21 are provided on the cam shaft 20, the valve springs that generate the valve spring torque to be offset by the cam surfaces 31 a of the anti-phase cams 31 are provided. What is necessary is just to design based on the compression reaction force of 28 and the lift speed of the exhaust valve 3.

(Second form)
Next, a second embodiment of the present invention will be described with reference to FIGS. In the second mode, the cam profile of the anti-phase cam 31 is designed in consideration of the inertial force of the reciprocating parts when the intake valve 2 or the exhaust valve 3 is driven to open and close. The mechanical configuration of the valve gears 11A and 11B is the same as that in the first embodiment.

  When the intake valve 2 or the exhaust valve 3 is opened and closed via the cam mechanism 14, an inertial force is generated by the reciprocating movement of the rocker arm 24, the valve spring 28, etc. along with the valves 2 and 3, and the cam mechanism 14 In addition to the valve spring torque, inertia torque acts on the valve. When the rotational speed of the internal combustion engine is low, the inertia torque is sufficiently smaller than the valve spring torque based on the compression reaction force of the valve spring 28, but the influence of the inertia torque becomes relatively large particularly in the high rotation range, and the intake air The valve characteristics of the valve 2 and the exhaust valve 3 may be ignored. Therefore, in this embodiment, the shape of the cam surface 31a of the antiphase cam 31 is designed in consideration of inertia torque.

The cam surface 31a of the anti-phase cam 31 in consideration of the influence of the inertia torque is set to a profile as indicated by a broken line in FIG. 3, for example, based on the valve spring torque and the inertia torque. The inertia torque Ta (N · m) is calculated from the following equation (2) when the inertia force is Fa (N) and the lift speed of the cam 21 is Vv (m / rad).
[Equation 2]

      Ta = Fa × Vv (2)

The inertial force Fa is calculated from the following equation (3) when the valve-side equivalent mass is We (kg) and the acceleration (valve acceleration) of the intake valve 2 or the exhaust valve 3 is Va (m / s2). Since the valve acceleration varies depending on the rotational speed of the internal combustion engine, the acceleration at the maximum rotational speed (for example, 6000 rpm) of the internal combustion engine is used here. This is because the influence of inertia torque appears more greatly as the rotational speed is higher.
[Equation 3]

      Fa = We × Va (3)

  The valve-side equivalent mass We is the total mass of the components that are driven to reciprocate by the cam mechanism 14, and in the valve gear 11A of FIG. is there. The same applies to the valve gear 11B on the exhaust side.

  By superimposing the inertia torque Ta and the valve spring torque Tv (the same as that shown in FIG. 5) that does not consider the influence of the inertia force Fa, the waveform of the composite torque T as shown in FIG. Is obtained. 6A, the positions P1 to P3 are the same as those in FIG. 5, the position Pa is a position where the maximum lift speed in the opening direction is given to the intake valve 2 or the exhaust valve 3, and the position Pb is the intake valve 2 or the exhaust valve. 3 shows positions where the maximum lift speed in the closing direction is given. The combined torque T is the inertia torque Ta in the positive (+) direction in the region A between the positions P1 and Pa and the region C between the positions P2 and Pb with respect to the waveform of the valve spring torque Tv. In the region B and the region D between the positions Pb to P3, the negative (−) direction inertia torque Tb is overlaid.

  As apparent from the equations (2) and (3), the direction of the inertia torque Ta is determined by the product of the lift speed Vv and the valve acceleration Va. The lift speed Vv (not shown) is a maximum value at the boundary between the areas A and B in FIG. 6A (the broken line on the left side in the figure), and is almost 0 at the boundary between the areas B and C (vertical axis in the figure). On the other hand, the valve acceleration Va (not shown) obtained by differentiating the lift speed Vv is a positive value in the regions A and D, while the region B is the minimum value at the boundary between the regions C and D (the broken line on the right side in the figure). , C takes a negative value. Accordingly, the product of the lift speed Vv and the valve acceleration Va becomes a positive value in the regions A and C, and a negative value in the regions B and D, and a combined torque T as shown in FIG. 6A is obtained.

  In order to cancel the combined torque T shown in FIG. 6 (a), the counter-phase counter-torque shown in FIG. 6 (b) may be applied from the torque reduction mechanism 30 to the camshaft 20. Such a counter torque has the following characteristics as compared with the counter torque (see the broken line in FIG. 5) necessary for canceling only the valve spring torque Tv described above. That is, the counter torque in FIG. 6B is the lift speed at the position where the cam mechanism 14 gives the maximum lift speed to the intake valve 2 or the exhaust valve 3 (positions Pa and Pb in FIG. 6A). While the cam 21 is located in the range where the torque increases (P1 to Pa, Pb to P3), it is relatively larger than the counter-torque required to cancel only the valve spring torque, and the range in which the lift speed decreases ( While the cam 21 is positioned at Pa to P2 and P2 to Pb), it is relatively smaller than the counter torque required to cancel only the valve spring torque Tv.

  In order to determine the profile of the cam surface 31a of the anti-phase cam 31 from the counter torque shown in FIG. 6B, the compression reaction force of the spring 35 is appropriately set as in the first embodiment, and FIG. The lift speed of the lifter 34 by the antiphase cam 31 is obtained by dividing the antiphase torque shown in FIG. If this lift speed is integrated, the lift amount of the anti-phase cam 31 corresponding to each phase of the cam 21 is acquired, and the profile of the anti-phase cam 31 can be determined.

  As described above, when the profile of the anti-phase cam 31 is designed in consideration of the inertia torque, the lift characteristics of the intake valve 2 or the exhaust valve 3 as shown in FIGS. 7A and 7B are obtained. The horizontal axis of the lift shape indicates the crank angle, and the vertical axis indicates the lift amount. FIG. 7A shows the lift characteristics in the high speed rotation range of the internal combustion engine, and FIG. 7B shows the lift characteristics in the low speed rotation range. In FIGS. 7A and 7B, the solid line indicates the lift characteristics of the intake valve 2 or the exhaust valve 3 by the anti-phase cam 31 in consideration of the combined torque T, and the broken line indicates the anti-phase cam 31 in which the inertia torque is not considered. The lift characteristics of the intake valve 2 or the exhaust valve 3 are shown respectively.

  As shown by the broken line in FIG. 7A, in the anti-phase cam 31 that considers only the valve spring torque Tv, the torque applied from the torque reduction mechanism 30 to the camshaft 20 is insufficient, so that the rotation of the motor 12 is delayed. The rise of the lift amount tends to be delayed. On the other hand, the anti-phase cam 31 that takes into account the inertia torque Ta can eliminate the delay in the rise of the lift amount (solid line in FIG. 7A). As a result, the area surrounded by the lift shape and the horizontal axis, the so-called time area, can be increased, and the control accuracy can be improved by operating the intake valve 2 and the exhaust valve 3 as intended. Can do. Further, as shown by the solid line in FIG. 7B, according to the anti-phase cam 31 in consideration of the inertia torque Ta, the time area can be increased by adding the motor torque even in the low speed rotation region, and the intake valve 2 Alternatively, intake or exhaust can be sufficiently performed from the exhaust valve 3.

  When the anti-phase cam 31 is designed in accordance with the inertia torque when the internal combustion engine is operated at the maximum rotation speed, the torque fluctuation with respect to the change in the cam angle (phase) increases, and the cam surface of the anti-phase cam 31 There exists a tendency for the curvature radius of 31a to become small. However, such a cam surface 31a having a small curvature radius may not be formed due to design restrictions. In this case, the profile of the anti-phase cam 31 is set based on a torque characteristic (solid line in FIG. 8) intermediate between the combined torque T (broken line in FIG. 8) and the valve spring torque Tv (dotted line in FIG. 8). May be. As a result, it is possible to avoid the curvature radius of the profile of the anti-phase cam 31 from becoming extremely small, so that the design constraints can be satisfied while taking the inertia torque Ta into consideration.

  The present invention is not limited to the form described above, and may be implemented in various forms. The configuration of the torque reduction mechanism 30 is an example, and various modifications can be made. The torque reduction mechanism 30 is not limited to the form arranged coaxially with the cam shaft 20, and it is sufficient that torque can be applied at any position on the rotation transmission path from the motor 12 to the cam shaft 20. For example, the anti-phase cam 31 may be provided coaxially with the intermediate gear 16 provided between the motor gear 15 and the drive gear 17. Alternatively, a shaft that rotates in mesh with the cam shaft 20 may be further added outside the rotation transmission path from the motor 12 to the cam shaft 20, and the anti-phase cam 31 may be provided on the shaft. However, the shaft on which the anti-phase cam 31 of the torque reduction mechanism 30 is to be provided needs to rotate at a rotational speed of 1 / N (where N is an integer) with respect to the rotational speed of the cam shaft 20. Since the cycle of the valve spring torque and the inertia torque acting on the camshaft 20 varies in the same cycle as the opening / closing motion of the camshaft 20, the antiphase torque from the torque reduction mechanism 30 is changed in the same cycle as those torques. In this case, the relationship that the cam shaft 20 rotates at an integral multiple speed with respect to the antiphase cam 31 needs to be established. When the antiphase cam 31 rotates at the same speed as the camshaft 20, the profile of the cam surface 31a may be set by associating one rotation of the antiphase cam 31 with one rotation of the cam 21. Is rotated at a slower speed than the cam shaft 20, that is, when N ≧ 2, the profile of the anti-phase cam 31 may be determined by associating the 1 / N circumference of the anti-phase cam 31 with one revolution of the cam 21. . For example, when N = 3, the anti-phase cam 31 is repeatedly provided with the profile corresponding to the counter torque shown in FIG. 5 or FIG. 6B three times in the circumferential direction.

  In FIG. 2, one torque reduction mechanism 30 is provided for two intake valves 2 of one cylinder 1, but the torque reduction mechanism 30 may be provided separately for each intake valve 2. Even when a plurality of exhaust valves or intake valves are individually driven by a plurality of different cams as in the exhaust valve mechanism 11B, one torque reduction is performed for the two cams 21 as shown in FIG. A mechanism 30 may be provided. If the torque reduction mechanism 30 is shared among a plurality of cams in this way, the length of the cam shaft 20 in the axial direction can be shortened compared to the case where a torque reduction mechanism is provided for each cam, and the valve gears 11A and 11B are installed. The restrictions on space can be relaxed.

  In addition, when providing one torque reduction mechanism 30 with respect to the some cam 21, you may arrange | position the anti-phase cam 31 of the torque reduction mechanism 30 between cams 21 as shown in FIG. In this case, compared with the structure of FIG. 9, the torque which the cam shaft 20 bears between the torque reduction mechanism 30 and the cam 21 can be reduced, and the shaft diameter of the cam shaft 20 can be made small. If the shaft diameter of the cam shaft 20 is reduced, the moment of inertia of the cam shaft 20 is also reduced, and the response of the motor 12 is improved.

  The present invention is not limited to the example in which the valve gears 11A and 11B are provided for each cylinder 1. The cam shaft 20 may be shared among the plurality of cylinders 1, and one torque reduction mechanism 30 may be provided for one cam shaft 20. However, when the camshaft 20 is provided across a plurality of cylinders, the cam 21 is out of phase for each cylinder 1, and therefore, torque obtained by synthesizing the valve spring torque and inertia torque for each cylinder acting on the camshaft 20. It is necessary to determine the cam profile of the antiphase cam 31 based on the above. For example, when a camshaft 20 is shared among all cylinders 1 in a four-cylinder internal combustion engine that realizes equidistant explosions, the torque corresponding to each cylinder 1 is represented by a crank angle as shown in FIG. Since it is added to the camshaft 20 while being shifted by 180 °, the profile of the antiphase cam 31 may be set based on the combined torque shown in FIG.

  When one torque reduction mechanism 30 is provided for a plurality of intake valves 2 or exhaust valves 3, the compression reaction force of the spring 35 of the torque reduction mechanism 30 is equal to the compression reaction force of one valve spring 28 and the intake valve. 2 or the number of exhaust valves 3 is desirable. By setting the compression reaction force of the spring 35 of the torque reduction mechanism 30 in this way, the lift characteristics of the intake valve 2 or the exhaust valve 3 by the anti-phase cam 31 and the cam 21 can be made to coincide with each other. Thereby, since the profile of the anti-phase cam 31 can be set based on the smooth profile which the cam 21 has, there is no possibility that the radius of curvature of the profile of the anti-phase cam 31 is extremely reduced.

The perspective view which shows the valve gear of this invention. The perspective view which shows a cam mechanism. The figure which shows the detail of the torque reduction mechanism provided in the valve gear of FIG. The figure which shows the profile of the antiphase cam of FIG. The figure which shows an example of correlation with a cam angle and valve spring torque. The figure which shows an example of the correlation of a cam angle and synthetic | combination torque at the time of considering an inertia torque. The figure which shows an example of the correlation of the crank angle and the lift amount of an intake valve or an exhaust valve when antiphase torque is added in consideration of inertia torque. The figure which shows an example of the correlation of a cam angle and a torque at the time of setting antiphase torque to the intermediate value of valve spring torque and synthetic | combination torque. The figure which shows the example of arrangement | positioning of an antiphase cam. The figure which shows the other example of arrangement | positioning of an anti-phase cam. The figure which shows the waveform of the synthetic | combination torque at the time of sharing a cam shaft with a some cylinder.

Explanation of symbols

1 cylinder 2 intake valve (valve means)
3 Exhaust valve (valve means)
11A, 11B Valve train 12 Motor (electric motor)
13 Gear train 14 Cam mechanism 20 Cam shaft 21 Cam 24 Rocker arm 28 Valve spring 30 Torque reduction mechanism 31 Anti-phase cam 32 Torque addition device 34 Lifter (holding member)
35 Spring (biasing member)
T Synthetic torque Ta, Tb Inertia torque Tv Valve spring torque Vv Lift speed

Claims (7)

The operation of the internal combustion engine that converts the rotary motion of the electric motor to linear motion by a cam mechanism having a plurality of cams provided so as to be rotatable integrally with the cam shaft, and drives the valve means for opening and closing the cylinder against the valve spring. In the valve device,
A torque reduction mechanism for adding to the cam mechanism anti-torque that acts to reduce the torque applied from the valve spring to the cam mechanism when driving the valve means;
The valve operating device for an internal combustion engine, wherein the torque reduction mechanism is disposed between the plurality of cams.   The torque reduction mechanism rotates in conjunction with a rotational speed of 1 / N times (where N is an integer) with respect to the rotational speed of the cam of the cam mechanism, and an anti-phase cam having a cam surface formed on the surface. A cam pressing member that contacts the cam surface; and a biasing member that biases the cam pressing member toward the cam surface of the anti-phase cam. 2. The counter torque according to claim 1, wherein a counter torque that cancels a valve spring torque applied to the cam mechanism by a reaction force of the valve spring is applied from the biasing member to the counter phase cam. The valve operating device described.   The torque reduction mechanism rotates in conjunction with a rotational speed of 1 / N times (where N is an integer) with respect to the rotational speed of the cam of the cam mechanism, and an anti-phase cam having a cam surface formed on the surface. A cam pressing member that contacts the cam surface, and a biasing member that biases the cam pressing member toward the cam surface of the anti-phase cam, and the contour of the cam surface of the anti-phase cam is: The biasing torque counteracts the combined torque obtained by combining the valve spring torque applied to the cam mechanism by the reaction force of the valve spring and the inertia torque added to the cam mechanism as the valve means moves. 2. The valve operating apparatus according to claim 1, wherein the valve operating apparatus is set so as to be added to the anti-phase cam from a member.   The cam of the cam mechanism is set in the direction opposite to the rotation direction by the reaction force of the valve spring, with the cam mechanism as a boundary when the cam mechanism gives the maximum lift amount to the valve means. While positioned on the side to be pushed back, the counter torque applied from the biasing member acts in the direction of pushing the counter phase cam in the rotation direction, and the cam of the cam mechanism is rotated by the reaction force of the valve spring. The cam surface contour of the anti-phase cam is set so that the counter-torque acts in a direction to push the anti-phase cam back in the direction opposite to the rotational direction while it is positioned on the side pushed in the direction. The valve gear according to claim 2, wherein:   The cam of the cam mechanism is set in the direction opposite to the rotation direction by the reaction force of the valve spring, with the cam mechanism as a boundary when the cam mechanism gives the maximum lift amount to the valve means. While positioned on the side to be pushed back, the counter torque applied from the biasing member acts in the direction of pushing the counter phase cam in the rotation direction, and the cam of the cam mechanism is rotated by the reaction force of the valve spring. The counter-torque acts in a direction to push the anti-phase cam back in the direction opposite to the rotation direction while the cam mechanism gives the maximum lift speed to the valve means. The counter torque required to cancel only the valve spring torque while the cam of the cam mechanism is located within the range where the lift speed increases from the position. A relatively large counter-torque acts on the counter-phase cam, and the counter-acting necessary for canceling only the valve spring torque while the cam of the cam mechanism is located in a range where the lift speed decreases. The valve operating apparatus according to claim 3, wherein a contour of the cam surface of the anti-phase cam is set so that a counter-torque relatively smaller than the torque acts on the anti-phase cam.   The torque reduction mechanism rotates in conjunction with a rotational speed of 1 / N times (where N is an integer) with respect to the rotational speed of the cam of the cam mechanism, and an anti-phase cam having a cam surface formed on the surface. A cam pressing member that contacts the cam surface; and a biasing member that biases the cam pressing member toward the cam surface of the anti-phase cam, and the compression reaction force of the biasing member is the valve. The valve operating apparatus according to claim 1, wherein the valve operating apparatus is set to be equal to a product of a compression reaction force of a spring and the number of the valve means.   The torque reduction mechanism rotates in conjunction with a rotational speed of 1 / N times (where N ≧ 2 is an integer) with respect to the rotational speed of the cam of the cam mechanism, and has an antiphase in which a cam surface is formed on the surface. The valve gear according to claim 1, further comprising a cam.

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