JP2007016726A - Lift-variable valve gear of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the degree of freedom of the mounting position of an actuator by preventing heat damage from occurring at the thermally embrittled part of the actuator in a lift-variable valve gear of an internal combustion engine in which the actuator rotatingly driving a control shaft installed in a lift-variable mechanism comprises an electric motor, a speed reduction mechanism, a transmission mechanism interposed between the control shaft and the speed reduction mechanism, and a default mechanism and is mounted on an engine body. <P>SOLUTION: A speed reduction mechanism storage part 59a storing the speed reduction mechanism 63 and a default mechanism storage part 59c storing the default mechanism 65 are formed in the casing 59 of the actuator 60 while holding a thermally embrittled part 71 directly coupled to the control shaft 54 from both sides. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  According to the present invention, an actuator that rotationally drives a control shaft provided in a variable lift mechanism that can change a lift amount of an engine valve includes an electric motor, a speed reduction mechanism that decelerates an output of the electric motor, and the control A transmission mechanism interposed between the shaft and the speed reduction mechanism, and a default mechanism that enables the control shaft to be biased to a position where the lift amount of the engine valve is a predetermined lift amount when the electric motor is not energized. And a lift variable valve operating apparatus for an internal combustion engine that is attached to the engine body.

An actuator that is attached to the engine body so as to drive the control shaft is connected to the electric motor, a screw shaft that is rotationally driven by the electric motor, and the other end of the lever that has one end fixed to the control shaft. In addition, for example, Patent Document 1 has already been known that includes a nut screwed onto the screw shaft.
JP 2005-42642 A

  By the way, I want to make some of the components of the actuator of such a lift variable valve operating system made of synthetic resin for weight reduction or friction reduction, or to attach sensors whose characteristics change depending on the environmental temperature to the actuator. However, such synthetic resin parts and sensors are vulnerable to heat. On the other hand, since the actuator is mounted on the engine body, depending on the mounting position of the actuator on the engine body, the actuator is exposed to the radiant heat from the back wind of the radiator or the exhaust system of the internal combustion engine, and the above-mentioned heat is weak. The degree of freedom of the mounting position of the actuator using the part is narrowed.

  The present invention has been made in view of such circumstances, and provides a variable lift valve operating system for an internal combustion engine in which the degree of freedom of the mounting position of the actuator is increased so as not to cause thermal damage to the heat-fragile portion of the actuator. The purpose is to provide.

  In order to achieve the above object, according to the first aspect of the present invention, an actuator for rotationally driving a control shaft provided in a variable lift mechanism capable of changing a lift amount of an engine valve includes an electric motor and the electric motor. A speed reduction mechanism for reducing the output of the motor, a transmission mechanism interposed between the control shaft and the speed reduction mechanism, and a control shaft to a position where the lift amount of the engine valve is a predetermined lift amount when the electric motor is not energized. In a lift variable valve operating apparatus for an internal combustion engine that is attached to an engine body with a default mechanism that can be urged to rotate, a speed reduction mechanism accommodating portion that accommodates the speed reduction mechanism in a casing of the actuator, and the Heat-fragile part where the default mechanism housing part that houses the default mechanism is directly connected to the control shaft Characterized in that it is formed by sandwiching from both sides.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect of the invention, the heat-fragile portion is a sensor that detects a rotation amount of the control shaft.

  Furthermore, in addition to the structure of the invention of claim 1, the invention of claim 3 is a synthetic resin worm wheel in which the heat-fragile portion constitutes a part of the transmission mechanism and is fixed to the control shaft. It is characterized by being.

  The intake valve 38 of the embodiment corresponds to the “engine valve” of claim 1 of the present invention.

  According to the first aspect of the present invention, since the heat fragile portion is sandwiched between the speed reduction mechanism accommodating portion and the default mechanism accommodating portion formed in the casing, the speed reduction mechanism accommodating portion and the default mechanism accommodating portion are shielded against the heat fragile portion. Acts as a thermal function, avoids heat damage to the heat-fragile part, improves the durability of the heat-fragile part, and prevents heat damage from occurring in the heat-fragile part. Can be increased.

  According to the second aspect of the present invention, the characteristics of the sensor change depending on the environmental temperature, and the sensor is not directly exposed to hot air or radiant heat by sandwiching the sensor between the speed reduction mechanism accommodating portion and the default mechanism accommodating portion. In this way, the detection accuracy of the sensor can be increased.

  According to a third aspect of the present invention, the worm wheel made of synthetic resin is used to reduce the weight of the actuator and reduce the friction, while reducing the friction between the speed reduction mechanism housing portion and the default mechanism housing portion. By sandwiching the foil, it is possible to improve reliability and durability by preventing thermal damage from being applied to the worm foil, and to prevent an increase in friction due to thermal deformation or the like, thereby saving energy.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on one embodiment of the present invention shown in the accompanying drawings.

  1 to 14 show an embodiment of the present invention. FIG. 1 is a side view of an internal combustion engine in a vehicle-mounted state, FIG. 2 is a view taken along arrow 2 in FIG. 1, and FIG. 4 is an exploded perspective view of the intake side valve operating device, FIG. 5 is an enlarged view of the main part of FIG. 1, FIG. 6 is a side view of the actuator, FIG. 7 is a vertical side view of the actuator, and FIG. 7 is a cross-sectional view taken along line 8-8 in FIG. 7, FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 7, FIG. 10 is a schematic diagram for explaining the configuration of the default mechanism, and FIG. 12 shows the efficiency of the electric motor, the generated torque of the electric motor, and the generated torque of the actuator, FIG. 13 shows the change of the spring force with respect to the lift amount change of the intake valve, and FIG. 14 shows the internal combustion in the vehicle mounted state. It is a top view which simplifies and shows the relative arrangement | positioning of an engine and a radiator.

  First, in FIGS. 1 and 2, a plurality of cylinders, for example, a four-cylinder engine body 22 having an axis C of a crankshaft 21 along the width direction of the vehicle is mounted on the front portion of the vehicle. The engine body 22 is provided side by side in a cylinder arrangement direction 23 parallel to the axis C.

  The engine body 22 includes a crankcase 24 that rotatably supports the crankshaft 21, a cylinder block 25 coupled to the crankcase 24, a cylinder head 26 coupled to the cylinder block 25, and a cylinder head 26. And a cam holder 28 that is coupled to the cylinder head 26 at one end on the left side along the cylinder arrangement direction 23 and forms a part of the engine body 22. It is arranged to face the outside.

  A transmission case 32 that houses a transmission at the left end of the crankcase 24 with the vehicle facing forward is configured to form an empty space on the left side of the engine body 22 and above the transmission case 32. Combined.

  One side wall 26a (see FIG. 1) facing the front side of the cylinder head 26 is provided with intake ports 33 for each cylinder, and an intake system 34 is connected to the intake ports 33. Further, the other side wall 26b (see FIG. 1) facing the rear side of the cylinder head 26 is provided with exhaust ports 35 for each cylinder, and the exhaust ports 35 are provided with heat insulating covers 36 from above. The exhaust manifold 37 to be covered is connected.

  The intake system 34 includes an air cleaner 108, an intake chamber 109 disposed in front of the cylinder head 26 in common with each cylinder, a pipe member 110 such as a hose connecting the air cleaner 108 and the intake chamber 109, an intake chamber 109 and a plurality of intake pipes 111, 111,... Connected to the cylinder head 26 for each cylinder. A pair of support legs 112 are provided in the intake chamber 109 so as to extend downward, and these support legs 112 are supported by a bracket 113 attached to the crankcase 28 via elastic members 114. The

  3 and 4, the cylinder head 26 is provided with a pair of engine valves 38... For each intake port 33... That can be opened and closed. The intake side valve operating device 39 that swings in response to the intake side camshaft 41 having the intake side valve cam 40 for each cylinder and the intake side valve cam 40 and swings for each cylinder. .., And a variable lift mechanism 43 that continuously changes the valve opening lift amount among the operating characteristics of the intake valves 38.

  Upper holders 44 are fastened to the cylinder head 26 so as to be arranged on both sides of each cylinder except for one end on the left side along the cylinder arrangement direction 23, and cooperate with each upper holder 44. Caps 45 that rotatably support the intake side camshaft 41 are fastened to the upper surface of the upper holders 44. The end of the intake camshaft 41 is rotatably supported between the camshaft 28 and the head cover 27 at one end on the left side along the cylinder arrangement direction 23.

  One end portion of the intake side rocker arm 42 is provided with a valve connecting portion 42a into which tappet screws 46 abutting from above on the upper ends of the stems 38a of the pair of intake valves 38 are screwed so that the advance / retreat position can be adjusted. The other end portion of the intake side rocker arm 42 is provided with a first support portion 42b and a second support portion 42c disposed below the first support portion 42b so as to be connected to each other. The portions 42b and 42c are formed in a substantially U shape that opens on the opposite side to the intake valves 38.

  A roller 47 that is in rolling contact with the intake side valve cam 40 of the intake side camshaft 41 is pivotally supported on the first support portion 42 b of the intake side rocker arm 42 via a first connecting shaft 48 and a needle bearing 49. The roller 47 is disposed so as to be sandwiched between first support portions 42b having a substantially U shape.

  The variable lift mechanism 43 has a first link arm 51 that has one end rotatably connected to the first support portion 42 b of the intake side rocker arm 42 and the other end rotatably supported by a fixed support shaft 50. A second link arm 52 having one end rotatably connected to the second support portion 42c of the intake side rocker arm 42 and the other end rotatably supported by a movable support shaft 53; A control shaft 54 connected to the movable support shaft 53 is provided so that the support shaft 53 can be angularly displaced about an axis parallel to the axis.

  One end portion of the first link arm 51 is formed in a substantially U shape so as to sandwich the first support portion 42b of the intake side rocker arm 42 from both sides, and a first connection that pivotally supports the roller 47 on the intake side rocker arm 42. The shaft 48 is rotatably connected to the first support portion 42b. A fixed support shaft 50 that rotatably supports the other end of the first link arm 51 is supported by the upper holder 44.

  One end portion of the second link arm 52 disposed below the first link arm 51 is disposed so as to be sandwiched between the second support portions 42 c of the intake side rocker arm 42, and is second supported via the second connecting shaft 55. The part 42c is rotatably connected.

  The two intake valves 38 are spring-biased in the valve closing direction by a valve spring (not shown), and the two intake valves 38... That are spring-biased in the valve closing direction are opened by the intake side rocker arm 42 in the valve opening direction. The roller 47 of the intake-side rocker arm 42 is in contact with the intake-side valve cam 40 by the spring biasing force of the valve spring while the intake valve 38 is in the closed state. The spring biasing force of the spring does not act on the intake side rocker arm 42, and the roller 47 is separated from the intake side valve cam 40, and the control accuracy of the valve lift amount when the intake valves 38 are minutely opened decreases. There is a possibility that. Therefore, the rocker arm biasing spring 56 different from the valve spring biases the intake-side rocker arm 42 in a direction in which the roller 47 is brought into contact with the intake-side valve cam 40.

  The control shaft 54 is a single shaft common to a plurality of cylinders arranged in a row, and the webs 54a disposed on both sides of the intake-side rocker arm 42 and the shafts that are perpendicular to the outer surfaces of the proximal ends of both webs 54a. 54b... And connecting portions 54c that connect the webs 54a... Are formed in an integral crank shape for each cylinder and have an axis parallel to the fixed support shaft 50 and the shaft portion 54b. The support shaft 53 is connected to the control shaft 54 so as to connect the two webs 54a. In addition, the shaft portions 54b are rotatably supported by the upper holders 44 and lower holders 57 fastened to the lower surfaces of the upper holders 44.

  By the way, the second connecting shaft 55 that connects the second link arm 52 to the intake side rocker arm 42 when the intake valves 38 are closed is coaxial with the shaft portion 54b of the control shaft 54. Oscillates around the axis of the shaft portion 54b..., The movable support shaft 53 moves on an arc centering on the axis of the shaft portion 54b.

  When the control shaft 54 rotates in the direction in which the movable support shaft 53 descends and the roller 47 is pressed by the intake side valve cam 40 of the intake side camshaft 41, the fixed support shaft 50, the first connecting shaft 48, The four-bar link connecting the two connecting shafts 55 and the movable support shaft 53 is deformed, the intake side rocker arm 42 swings downward, the tappet screws 46... Press the stems 38 a of the intake valves 38, and the intake valves 38. Open the valve with a low lift.

  When the control shaft 54 is rotated in the direction in which the movable support shaft 53 is raised and the roller 47 is pressed by the intake side valve cam 40 of the intake side camshaft 41, the four-bar link is deformed and the intake side rocker arm is deformed. 42 swings downward, the tappet screws 46 press the stems 38a of the intake valves 38, and the intake valves 38 open with high lift.

  One end portion of the control shaft 54 along the cylinder arrangement direction 23, that is, of the plurality of shaft portions 54b provided in the control shaft 54, the shaft portion on one end side along the cylinder arrangement direction 23 is formed relatively long as a connecting shaft portion 54d. The connecting shaft portion 54d protrudes to the left side of the cylinder head 26, and the connecting shaft portion 54d is inserted into the casing 59 of the actuator 60 attached to the outer surface of the left end wall of the cylinder head 26. .

  5-7, the actuator 60 includes an electric motor 62, a speed reduction mechanism 63 that decelerates the output of the electric motor 62, and a transmission mechanism 64 provided between the speed reduction mechanism 63 and the connecting shaft portion 54d of the control shaft 54. The connection shaft portion 54d, that is, the main portion of the default mechanism 65 for maintaining the control shaft 54 in a predetermined rotation position when the electric motor 62 is not energized is housed in a casing 59. The casing main body 61 includes a first cover 74, a lid member 82, and a second cover 88 fastened to the casing main body 61.

  The speed reduction mechanism 63 is provided between the output shaft 66 of the electric motor 62 that can rotate forward and backward with the default position set by the default mechanism 65 as the zero point position, and the drive shaft 67 parallel to the axis of the output shaft 66. And includes a drive gear 68 fixed to the output shaft 66 and a driven gear 69 meshed with the drive gear 68 and fixed to the drive shaft 67, from the maximum lift amount to the minimum lift amount, for example, fully closed. As the electric motor 62 rotates within an operating range in which the lift amount of the intake valves 38 is changed, the drive shaft 67 rotates in a range of one rotation or more. The transmission mechanism 64 includes a worm gear 70 provided on the drive shaft 67 and a worm wheel 71 that meshes with the worm gear 70 and is fixed to the connecting shaft portion 54d of the control shaft 54.

  A motor housing hole 72 having a circular cross section is provided in the lower part of the casing main body 61 so as to extend in the front-rear direction when the engine body 22 is mounted on a vehicle. The electric motor 62 is fitted and fixed in the motor housing hole 72. Is done. Further, when the engine body 22 is mounted on the vehicle, a first cover 74 is fastened to one side wall of the casing main body 61 as a rear side wall with a plurality of bolts 73. A speed reduction mechanism housing portion 59a configured with the first cover 74 and housing the speed reduction mechanism 63 is formed so as to extend above the electric motor 62 at a position behind the electric motor 62 when the vehicle is mounted.

  The worm gear 70 is accommodated in a worm gear accommodation hole 75 provided in the casing main body 61 in parallel with the motor accommodation hole 72 above the motor accommodation hole 72, and one end portion of the worm gear 70 is inserted into the casing via a ball bearing 76. The other end portion is provided on the outer periphery of a drive shaft 67 that is rotatably supported on the main body 61 and is rotatably supported on the casing main body 61 via a needle bearing 77.

  Referring also to FIG. 8, a worm wheel housing chamber 78 communicating with the middle portion of the worm gear housing hole 75 is formed in the upper portion of the casing main body 61, and the worm wheel 71 is placed in the worm wheel housing chamber 78. Be contained. Thus, the connecting shaft portion 54d of the control shaft 54 is inserted into the worm wheel housing chamber 78, and the worm wheel 71 is screwed into a screw hole 79 provided coaxially at the end of the connecting shaft portion 54d. The bolt 80 is tightened and fixed to the connecting shaft portion 54d.

  An opening 81 is provided on the opposite side of the cylinder head 26 from the upper portion of the casing main body 61, and a lid member 82 that closes the opening 81 is fastened to the casing main body 61 by a plurality of screw members 83. Thus, in the casing 59, a transmission mechanism accommodating portion 59b, which is constituted by a part of the casing main body 61 and the lid member 82 and accommodates the transmission mechanism 64, is located in front of the speed reduction mechanism accommodating portion 59a when the vehicle is mounted. It is formed so that it may be located in.

  Moreover, a sensor 84 that is a position sensor for detecting the amount of rotation of the control shaft 54 is attached to the lid member 82 with a plurality of screw members 85. A pair of detection holes 86, 86 for engaging the sensor 84 are provided.

  A second cover 88 is fastened to the other side wall of the casing main body 61 with a plurality of bolts 87 on the side opposite to the speed reduction mechanism accommodating section 59a with respect to the transmission mechanism accommodating section 59b. A default mechanism housing portion 59c configured by a part and the second cover 88 and housing the main part of the default mechanism 65 is formed so as to sandwich the transmission mechanism housing portion 59b between the speed reduction mechanism housing portion 59a. .

  Referring also to FIG. 9, the default mechanism 65 rotates around the axis of the default shaft 66 and a default shaft 96 which is a member different from the drive shaft 67 and has an axis parallel to the drive shaft 67. The large-diameter gear 92 that is linked and connected to the drive shaft 67, the spring holder 93 that can rotate around the same axis as the large-diameter gear 92, and the large-diameter gear 92 abuts and engages the spring holder 93. A return spring 94 (see FIG. 4) that urges the spring holder 93 in the direction to be moved, and a default spring 95 that urges the spring holder 93 in a direction opposite to the return spring 94 when the large-diameter gear 92 and the spring holder 93 are in contact with and engaged with each other. With.

  Both ends of the large diameter gear 92 are rotatably supported by a default shaft 96 supported by the casing main body 61 and the second cover 88, and mesh with a small diameter gear 97 provided at the other end of the drive shaft 67. That is, the large-diameter gear 92 is linked and connected to the electric motor 62 via the small-diameter gear 97, the drive shaft 67, and the speed reduction mechanism 63, and lifts the intake valve 38 from the maximum lift amount to the minimum lift amount, for example, fully closed. As the electric motor 62 rotates within the operating range in which the amount is changed, the large-diameter gear 92 rotates within a rotation range of less than one rotation. That is, the large-diameter gear 92 is linked and connected to the electric motor 62 so as to rotate within a rotation range of less than one rotation in accordance with the rotation of the electric motor 62 within the lift amount change range of the intake valves 38. .

  The spring holder 93 is supported on the default shaft 96 so as to be able to rotate relative to the large-diameter gear 92. An arcuate groove 98 centering on the axis of the default shaft 96 is provided on the surface of the large-diameter gear 92 that faces the spring holder 93, and an engagement protrusion that is inserted into the groove 98 is provided on the spring holder 93. 99 is projected. Thus, the engagement protrusion 99 is rotated in the circumferential direction of the large-diameter gear 92 in response to the rotation of the large-diameter gear 92 while changing the lift amount of the intake valves 38 between a predetermined lift amount and a minimum lift amount. When the large-diameter gear 92 is rotated so as to change the lift amount of the intake valves 38 between a predetermined lift amount and a minimum lift amount. The spring holder 93 rotates together with the large diameter gear 92 around the same axis. Moreover, the restricting protrusion 100 protruding from the spring holder 93 is provided on the second cover 88 according to the rotation of the spring holder 93 when the lift amount of the intake valves 38 is changed from the minimum lift amount to the predetermined lift amount. The rotation of the spring holder 93 is restricted by contacting the provided stopper 101 (see FIG. 10), and the rotation range of the spring holder 93 is restricted between the predetermined lift amount and the minimum lift amount. become.

  One end of the spiral default spring 95 is engaged with the spring holder 93, and the other end is engaged with a pin 88 a implanted in the second cover 88. Thus, the default spring 95 exhibits a spring force that urges the spring holder 93 from the minimum lift amount side to the predetermined lift amount side, and the spring load is set larger than that of the return spring 94.

  Referring to FIG. 4, a cylindrical spring holder 102 surrounding the connecting shaft portion 54d is fixed to the connecting shaft portion 54d of the control shaft 54 in the cylinder head 26, and a return spring which is a torsion coil spring. 94 is wound around the spring holder 102. Moreover, one end of the return spring 94 is engaged with the cylinder head 26, and the other end of the return spring 94 is engaged with the spring holder 102.

  That is, the return spring 94 has a function of absorbing the backlash between the worm wheel 71 and the worm gear 70 as well as a function of urging the large-diameter gear 92 in a direction in which the large-diameter gear 92 is brought into contact with and engaged with the spring holder 93. 54 between the connecting shaft portion 54d and the cylinder head 26.

  In this way, the main part excluding the return spring 94, that is, the large diameter gear 92, the spring holder 93, and the default spring 95 among the large diameter gear 92, the spring holder 93, the return spring 94, and the default spring 95 constituting the default mechanism 64. Is housed in the default mechanism housing portion 59 c of the actuator 60, and only the return spring 94 is disposed in the cylinder head 26. In addition, the default mechanism accommodating portion 59c is filled with grease 103.

  The operation of the default mechanism 65 will be described with reference to FIG. 10 schematically showing the configuration of such a default mechanism 65. The large-diameter gear 92 is a return spring 94 that springs from the maximum lift position toward the minimum lift position. The spring holder 93 that is energized and whose rotation range is restricted to the range from the minimum lift position to the default position that is the predetermined lift amount of the intake valves 38 is the minimum lift by the default spring 95 that has a larger spring load than the return spring 94. The spring is biased from the position toward the default position. Therefore, when the electric motor 62 is in a non-energized state, the large-diameter gear 92 is rotated and biased by the return spring 94 to a position where the engagement protrusion 99 of the spring holder 93 is brought into contact with and engaged with one end of the engagement groove 98. The spring holder 93 is rotated to the default position by the default spring 95, and the large diameter gear interlocked and connected to the control shaft 54 via the small diameter gear 94, the drive shaft 67, the worm gear 70 and the worm wheel 71. 92 is also a default position, and the lift amount of the intake valves 38 is maintained at a predetermined amount.

  By the way, at least one of the worm wheel 71 and the worm gear 70 which constitute part of the actuator 60 and mesh with each other in a pair is made of synthetic resin. In this embodiment, the worm wheel 71 is made of, for example, nylon or It is made of a synthetic resin such as PEEK (trade name; Victrex).

  As clearly shown in FIG. 8, the casing main body 61 of the casing 59 is provided with a cylindrical tube portion 61 a communicating with the worm wheel housing chamber 78, and the left end wall of the cylinder head 26 has a control shaft 54. A cylindrical tube portion 26c that coaxially surrounds the connecting shaft portion 54d is provided so as to be fitted to the tube portion 61a, and an O-ring that elastically contacts the inner periphery of the tube portion 61a on the outer periphery of the tube portion 26c. 104 is mounted. That is, the casing main body 61 and the cylinder head 26 are fitted to each other in a direction along the axis of the connecting shaft portion 54d provided in the control shaft 54.

  The casing 59 of the actuator 60 is attached over the cylinder head 26 and the cam holder 28 which are engine body components constituting a part of the engine body 22, and the cylinder head 26 has a plurality of bolts 105 (FIG. 5). The casing main body 61 of the casing 59 is attached to the cam holder 28 with a bolt 106 (see FIG. 5).

  Mounting bosses 107 having insertion holes 106 are provided in the casing main body 61 of the casing 59 at four locations around the electric motor 62 that is fitted and fixed in the motor housing hole 68, and are inserted into the insertion holes 106. The casing main body 61 is fastened to the cylinder head 26 by the bolts 105.

  Moreover, the casing main body 61 is provided with ribs 118 to 125 that are continuous with the mounting bosses 107. The ribs 118 and 119 are arranged between the upper mounting boss 117 and the lower mounting boss 117. The ribs 120 are formed so as to cross each other in a letter shape, and the ribs 120 are formed so as to connect the lower mounting bosses 117, and the ribs 121 connect between the mounting bosses 117 arranged on the left and upper sides in FIG. The ribs 122 and 123 are formed so as to extend obliquely upward on the extension of the ribs 118 and 119 in connection with the upper mounting bosses 117, and the ribs 124 and 125 are obliquely formed with the ribs 122 and 123. It is formed to extend obliquely upward from the upper mounting bosses 124 and 125 so as to intersect.

  The casing main body 61 is attached to the cam holder 28 of the engine body 22 at a portion corresponding to at least one of the speed reduction mechanism 63, the transmission mechanism 64, and the default mechanism 65. In this embodiment, the portion corresponding to the default mechanism 65 is used. Thus, the casing main body 61 is fastened to the cam holder 28 with bolts 106.

  In FIG. 11, the casing main body 61 is provided with a mounting boss 127 having an insertion hole 126 at a portion corresponding to the default mechanism 65, and a bolt 106 passing through the slide bush 128 inserted into the insertion hole 126 is connected to the cam holder. 28. That is, the casing main body 61 is fastened to the cam holder 28 via the slide bush 128 at a portion corresponding to the default mechanism 65.

  Incidentally, the actuator 60 for controlling the lift amount of the intake valves 38 is basically interlocked with the accelerator operation of the vehicle driver. For example, the accelerator operation is frequently performed in a short time when traveling on a circuit or on a winding road. If it repeats, the electric motor 62 of the actuator 60 will also operate | move according to it, the effective current which flows into the electric motor 62 becomes large, and the electric motor 62 may generate | occur | produce heat. Therefore, the speed reduction ratio of the speed reduction mechanism 63 is determined so that the efficiency of the electric motor 62 is maximized when the electric motor 62 responds at the highest speed in response to the frequently repeated accelerator operation.

  Here, the efficiency of the electric motor 62 in the actuator 60, the generated torque of the electric motor 62, and the generated torque of the actuator 60 change as shown in FIG. Is set to 10 Nm, for example, the torque generated by the actuator 60 is determined so that the rotation speed of the electric motor 62 becomes the highest rotation speed, for example, 6200 rpm, when overcoming the required drive torque and responding at the highest speed. . Thus, the generated torque of the actuator 60 is obtained by (the generated torque of the electric motor 62 × the reduction ratio of the speed reduction mechanism 63). When the rotation speed of the electric motor 62 is determined to be 6200 rpm, for example, the speed is reduced. The reduction ratio of the mechanism 63 is set to 69.3, for example.

  Next, the operation of this embodiment will be described. The actuator 60 that rotationally drives the control shaft 54 provided in the variable lift mechanism 43 that can change the lift amount of the intake valves 38 is transmitted to the control shaft 54. A drive shaft 67 that is linked and connected via a mechanism 64 and an electric motor 62 that exerts power to rotate the drive shaft 67 so as to rotate one or more revolutions within the range of change in the lift amount of the engine valve 38. At the same time, at least the main part of the default mechanism 65 that enables the control shaft 54 to be biased to a position where the lift amount of the intake valves 38 is set to a predetermined lift amount when the electric motor 62 is not energized is provided. However, the default mechanism 65 has an axis parallel to the drive shaft 67 as a separate member from the drive shaft 67. A default shaft 96, a large-diameter gear 92 that can be rotated around the axis of the default shaft 96 and linked to the drive shaft 67, and a default spring 95 that urges the large-diameter gear 92 to rotate. And.

  Accordingly, the large-diameter gear 92 that rotates about the axis of the default shaft 96 is rotated within a rotation range of less than one rotation in accordance with the rotation of the electric motor 62 within the lift amount change range of the intake valves 38. Thus, it is possible to interlock and connect to the drive shaft 67, and it is possible to employ a default mechanism 65 that is conventionally used and has high durability and reliability.

  Since the default spring 95 is of a spiral type, the default mechanism 65 can be made compact in the direction along the axis of the default shaft 96.

  By the way, as shown in FIG. 13, the default mechanism 65 maintains the lift amount of the intake valve 38 at, for example, 1.8 mm during its operation, and the inclination of the spring constant of the spiral default spring 95 is as shown in FIG. Since it is relatively small as shown by the solid line, the load applied to the electric motor 62 is relatively small. On the other hand, when the default spring 95 has a coil, the slope of the spring constant becomes relatively large as shown by the chain line in FIG. The amount of work will increase.

  However, if the default spring 95 is of a spiral type, the sliding frictional force tends to increase due to interference between adjacent parts of the default spring 95 in the radial direction, but the casing 59 of the actuator 60 has a default spring of the default mechanism 65. The default mechanism accommodating portion 59c that accommodates the main portion including 95 is formed, and the grease 103 is filled in the default mechanism accommodating portion 59c. Therefore, the sliding frictional force should be reduced and the electric motor 62 should be exerted. Power can be reduced to save energy, which in turn can save fuel.

  The casing 59 of the actuator 60 is attached to the engine body 22 at a plurality of locations corresponding to the electric motor 62, and corresponds to at least one of the speed reduction mechanism 63, the transmission mechanism 64, and the default mechanism 65 (this embodiment). The portion corresponding to the default mechanism 65 is attached to the engine body 22, and the portion corresponding to the electric motor 62 that is the vibration generation source of the actuator 60 is firmly fixed to the engine body 22. In addition, it is possible to suppress vibration by firmly fixing the relatively heavy portion to the engine body 22. Therefore, the vibration resistance and durability of the actuator 60 attached to the engine body 22 can be improved, and the control accuracy of the control shaft 54 and the controllability of the exhaust property can be improved.

  Incidentally, the casing 59 is provided with mounting bosses 117 through which bolts 105 for fastening the casing 59 to the cylinder head 26 of the engine body 22 are inserted in four locations around the electric motor 62. A plurality of ribs 118 to 125 that are connected to the mounting bosses 117... Are projected, and the ribs 118 to 125 can prevent the casing 59 from being distorted. Of these, it is possible to avoid an increase in the sliding friction force between the parts supported by the casing 59 and in contact with each other, thereby reducing the driving force to be exhibited by the electric motor 62 and saving energy. .

  In addition, a portion corresponding to the electric motor 62 of the casing 59 is attached to the cylinder head 26 that constitutes a part of the engine body 22, and the cam holder 28 that constitutes a part of the engine body 22 and is coupled to the cylinder head 26. Since the casing 59 corresponding to the default mechanism 65 is fastened via the slide bush 128, even if the mounting surface facing the actuator 60 of the cylinder head 26 and the cam holder 28 coupled to each other is displaced. The casing 59 can be attached to the cylinder head 26 and the cam holder 28 so as not to be distorted, and the sliding friction force increases between the parts constituting the actuator 60 supported by the casing 59 and in contact with each other. To reduce the driving force that the electric motor 62 should exert It is possible to achieve an energy reduction, it is possible to improve the controllability of the control accuracy and exhaust emission of the control shaft 54.

  By the way, the speed reduction ratio of the speed reduction mechanism 63 provided in the actuator 60 is set to a value at which the maximum efficiency of the electric motor 62 can be obtained when the fastest response is made to the required drive torque.

  With such a setting, for example, the variable lift mechanism 43 in which the electric motor 62 is operated in response to frequent acceleration in a short time when driving on a circuit or on a winding road is subjected to the most severe operating conditions. At some point, the amount of heat generated by the electric motor 62 can be minimized. Therefore, it is possible to reduce the thermal effect exerted on the control shaft 54 from the electric motor 62 and to prevent the phase difference due to the twist of the control shaft 54 due to the heat generation of the electric motor 62 from being increased. Variations in the intake air amount due to the difference in the lift amount of the valves 38 can be kept small, and air-fuel ratio control and output control can be simplified.

  Further, the casing 59 of the actuator 60 includes a speed reduction mechanism accommodating portion 59a for accommodating the speed reducing mechanism 63 and a default mechanism accommodating portion 59c for accommodating the default mechanism 65. The worm wheel 71 and the sensor are heat-fragile portions directly connected to the control shaft 54. 84 is sandwiched from both sides.

  Therefore, as shown in FIG. 14, in the state where the engine main body 22 is horizontally placed behind the radiator 131 and mounted on the vehicle, the back wind from the radiator 131 indicated by the arrow 132 is attached to one end wall of the engine main body 22. Even if the radiant heat from the exhaust manifold 37 indicated by the arrow 133 hits the actuator 60 from the rear, the worm wheel 71 is interposed between the speed reduction mechanism accommodation portion 59a and the default mechanism accommodation portion 59c formed in the casing 59. Therefore, the speed reduction mechanism accommodating portion 59a and the default mechanism accommodating portion 59c perform a heat shielding function with respect to the worm wheel 71 and the sensor 84, thereby avoiding thermal damage to the worm wheel 71 and the sensor 84. Resistance of the worm wheel 71 and the sensor 84 It is possible to increase the sex.

  In particular, the sensor 84 that detects the amount of rotation of the control shaft 54 changes its characteristics depending on the environmental temperature, and the sensor 84 is not directly exposed to hot air or radiant heat, so that the detection accuracy of the sensor 84 can be improved. .

  The synthetic resin worm wheel 71 that constitutes a part of the transmission mechanism 64 and is fixed to the control shaft 54 can reduce the weight of the actuator 60 and reduce the friction. It is possible to increase the reliability and durability by preventing heat damage from being applied to 71 and to prevent the increase of friction due to thermal deformation or the like and to save energy.

  Thus, heat damage is not caused to the worm wheel 71 and the sensor 84, and the degree of freedom of the mounting position of the actuator 60 can be increased. For example, as in the first modification shown in FIG. When the main body 22 is mounted vertically on the rear side of the radiator 131 and mounted on the vehicle, even if the radiant heat from the exhaust manifold 37 indicated by the arrow 134 strikes the actuator 60 from the side, the speed reduction mechanism accommodating portion 59a is connected to the worm wheel 71 and A heat shielding function for the sensor 84 can be achieved.

  FIG. 16 shows a second modification of the present invention. An engine body 22 ′ having a pair of banks BA and BB and configured in a V shape is mounted on a vehicle in a horizontal position behind the radiator 131. In the state where the actuators 60, 60 are attached to one end of both banks BA, BB, the actuators 60, 60 have the backflow from the radiator 131 and the radiant heat from the exhaust manifold 37A as indicated by the arrow 135. The radiant heat from the exhaust manifold 37B as shown by the arrow 136 hits the actuators 60, 60 from the rear, but the speed reduction mechanism accommodating portions 59a of the casings 59 in both the actuators 60 ... and the default mechanism. The housing portions 59c ... perform the heat shielding function in the same manner as described above.

  Further, as in the third modification of the present invention shown in FIG. 17, in the state where the engine body 22 'configured in a V shape is vertically mounted behind the radiator 131 and mounted on the vehicle, both banks BA, BB When the actuators 60, 60 are attached to the rear ends, the radiant heat from the exhaust manifold 37A and the exhaust manifold 37B hits the actuators 60, 60 from the side as indicated by arrows 137, 138. The speed reduction mechanism accommodating portion 59a and the default mechanism accommodating portion 59c of the casing 59 in FIG.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. It is.

  For example, the present invention can be implemented in connection with an exhaust valve that is an engine valve.

It is a side view of an internal combustion engine in a vehicle mounting state. FIG. 2 is a view taken in the direction of arrow 2 in FIG. 1. It is a vertical side view of an intake side valve operating apparatus. It is a disassembled perspective view of an intake side valve operating apparatus. It is a principal part enlarged view of FIG. It is a side view of an actuator. It is a vertical side view of an actuator. FIG. 8 is a cross-sectional view taken along line 8-8 in FIG. 7. FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 7. It is a schematic diagram for demonstrating the structure of a default mechanism. FIG. 11 is a cross-sectional view taken along line 11-11 in FIG. 5. It is a figure which shows the efficiency of an electric motor, the generated torque of an electric motor, and the generated torque of an actuator. It is a figure which shows the change of the spring force with respect to the lift amount change of an intake valve. It is a top view which simplifies and shows relative arrangement | positioning of the internal combustion engine and a radiator in a vehicle mounting state. It is a top view corresponding to Drawing 14 of the 1st modification. It is a top view corresponding to Drawing 14 of the 2nd modification. It is a top view corresponding to Drawing 14 of the 3rd modification.

Explanation of symbols

22, 22 '... engine body 38 ... intake valve 43 as engine valve ... lift variable mechanism 54 ... control shaft 59 ... casing 60 ... actuator 62 ... electric motor 63 .... Deceleration mechanism 64 ... Transmission mechanism 65 ... Default mechanism 59a ... Deceleration mechanism accommodation part 59c ... Default mechanism accommodation part 71 ... Warm wheel 84 which is a thermal weak part ... Thermal weak part Is a sensor

Claims (3)

  An actuator (60) that rotationally drives a control shaft (54) included in the variable lift mechanism (43) that can change the lift amount of the engine valve (38) includes an electric motor (62) and the electric motor. A decelerating mechanism (63) for decelerating the output of (62), a transmission mechanism (64) interposed between the control shaft (54) and the decelerating mechanism (63), and when the electric motor (62) is not energized. The engine main body (22, 22 ′) includes a default mechanism (65) capable of turning and urging the control shaft (54) to a position where the lift amount of the engine valve (38) is set to a predetermined lift amount. ) Attached to the casing (59) of the actuator (60), the speed reduction mechanism accommodating portion for accommodating the speed reduction mechanism (63). 59a) and the default mechanism accommodating portion (59c) for accommodating the default mechanism (65) are formed by sandwiching the heat-fragile portions (71, 84) directly connected to the control shaft (54) from both sides. A variable lift valve operating system for an internal combustion engine.   The variable lift valve operating system for an internal combustion engine according to claim 1, wherein the heat-fragile portion is a sensor (84) for detecting a rotation amount of the control shaft (54).   The said heat weak part is a worm wheel (71) made from a synthetic resin which comprises a part of said transmission mechanism (64), and is fixed to the said control shaft (54), The characterized by the above-mentioned. Variable lift valve operating system for an internal combustion engine.

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