JP2006046254A - Valve system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low cost and compact valve system capable of avoiding a problem such as noise. <P>SOLUTION: Since an opposite inclined surface 5c of a nut 5 abuts on a inclined surface of a groove G to suppress displacement in a radial direction thereof, high frequency vibration of the nut 5 is reduced. Even if relative clearance among a screw shaft 4, the nut 5 and a ball is relatively large, collision of those is mitigated to suppress generation of noise. A pair of the opposite inclined surfaces 5c abut on the inclined surface of the groove G to prevent rotation of the nut 5. Consequently, both of rotation and displacement in the radial direction of the nut 5 is compatibly achieved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a valve operating mechanism, and more particularly to a valve operating mechanism capable of changing valve opening / closing timing and the like.

  In recent years, an internal combustion engine mounted on a vehicle often uses a variable valve timing type valve operating mechanism that changes a valve opening / closing timing in accordance with an engine speed or a load. In such a valve operating mechanism, for example, by applying hydraulic pressure, the phases of the sprocket and camshaft synchronized with the crankshaft can be changed, thereby making the valve timing variable.

  However, in the valve mechanism of the prior art described above, hydraulic pressure is required to make the valve timing variable, and therefore it is necessary to provide a hydraulic pump. In an internal combustion engine, hydraulic pumps are generally installed for lubrication of each part, but if hydraulic pressure is used to achieve variable valve timing, etc., a larger capacity hydraulic pump is required. Since the power is extracted from the crankshaft, there is a problem that fuel consumption is deteriorated accordingly.

On the other hand, a mechanism for changing the valve timing or the like using the power of the electric motor is known as disclosed in, for example, Patent Document 1 below. According to such a technique, by changing the valve timing or the like using the power of the electric motor, it is not necessary to take out the power directly from the crankshaft, and the fuel efficiency can be improved.
JP 2002-256832 A Japanese Patent Publication No. 6-73797

  Incidentally, in the mechanism disclosed in Patent Document 1, the driving force of the electric motor is transmitted to a control shaft whose valve timing is variable via a ball screw mechanism including a screw shaft and a nut. Here, a high-frequency force repeated in the forward and reverse directions generated by the camshaft rotation during operation of the internal combustion engine is transmitted from the valve mechanism side to the control shaft, and further to the ball screw mechanism via the control shaft. Is done.

  However, for example, ball screw mechanisms that are mass-produced generally tend to focus on lowering the cost even if the accuracy error range is large. Therefore, in order to ensure the smooth operation of the ball screw mechanism, there is a fact that the relative clearance between the screw shaft, the nut, and the ball must be relatively large. However, as described above, when a high-frequency force is transmitted from the control shaft to the ball screw mechanism, if the relative clearance between the screw shaft, the nut, and the ball is relatively large, according to the minute high-frequency vibration between the screw shaft and the nut, The collision with the screw shaft, nut and ball is always repeated, which causes a problem of generating abnormal noise and noise.

  On the other hand, Patent Document 2 describes a configuration in which vibration in the radial direction of the screw shaft is suppressed by a damping member attached to the screw shaft. Although it is conceivable to provide such a damping member on the nut, there is a problem of how to make a relationship with the nut detent.

  The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a valve mechanism that can avoid problems such as abnormal noise while being low-cost and compact.

The valve operating mechanism of the present invention is a valve operating mechanism capable of changing the open / close state of the valve.
A control shaft that changes the open / closed state of the valve by rotational displacement;
An electric motor;
A ball screw mechanism that transmits the power of the electric motor to the control shaft;
The ball screw mechanism is opposed to a screw shaft that is rotationally driven by the electric motor and has a male screw groove formed on an outer peripheral surface thereof, and a nut that is disposed so as to surround the screw shaft and has a female screw groove formed on an inner peripheral surface thereof. It has a plurality of balls arranged so as to be able to roll between both screw grooves, and a restraining means for preventing rotation of the nut and restraining displacement in the radial direction by engaging with the nut. .

  According to the valve mechanism of the present invention, the ball screw mechanism is disposed so as to surround the screw shaft and to be surrounded by a screw shaft that is rotationally driven by the electric motor and has an external thread groove formed on the outer peripheral surface. A nut formed with a female thread groove, a plurality of balls arranged to roll between the opposing thread grooves, and engaging the nut to prevent rotation of the nut and suppression of radial displacement. And the suppression means reduces the high-frequency vibrations in the nut while achieving the rotation prevention of the nut, thereby even when the relative clearance between the screw shaft, the nut, and the ball is relatively large. , These collisions can be mitigated, and thereby the generation of abnormal noise and noise can be suppressed with a compact configuration. The “valve open / closed state” refers to valve timing, valve lift, phase, etc., but is not limited thereto.

  It is preferable that the restraining means is provided in the housing and includes a groove that engages with the nut and extends in the axial direction, since it is possible to prevent rotation of the nut and restrain radial displacement. In addition, if all or a part of the outer periphery of the nut is placed in contact with the housing or a slight gap is interposed, galling displacement generated in the nut is suppressed by restraining the nut with respect to the housing, Alternatively, vibration that causes noise can be suppressed. That is, the “engagement” includes not only the contact state but also a state in which the minute gap is disposed.

  The suppression means is preferably provided in the housing and includes a guide shaft that engages with the nut and extends in the axial direction, so that it is possible to prevent rotation of the nut and suppression of radial displacement. In such a case, the guide shaft may be engaged with a groove or hole formed in the nut, and if the groove or hole of the nut and the guide shaft are arranged in contact or with a slight gap therebetween, The resulting galling displacement can be suppressed by restraining the nut with respect to the guide shaft, or vibration that causes noise can be suppressed.

  When the restraining means is disposed between the nut and the housing and includes a collar having an outer peripheral surface and an inner peripheral surface, at least a part of which is non-circular when the cross section in the direction perpendicular to the axis is taken, This is preferable because rotation prevention and suppression of radial displacement can be realized. When all or part of the outer periphery of the nut is in contact with the collar or with a slight gap interposed therebetween, galling displacement generated in the nut is suppressed by restraining the nut with respect to the collar, or noise. The vibration which produces can be suppressed.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a valve mechanism that can change the valve timing and valve lift, including the ball screw mechanism according to the present embodiment. In FIG. 1, for easy understanding, two valves on the intake side of one cylinder of the internal combustion engine are illustrated.

  In FIG. 1, a drive shaft 101 rotatably attached to a cylinder head (not shown) and a control shaft 102 extend in parallel. A disc-shaped eccentric cam 101 a is formed on the drive shaft 101, and a disc-shaped eccentric cam 102 a is also formed on the control shaft 102. An upper portion of the first link 103 having a hole 103a that engages with the eccentric cam 101a of the drive shaft 101 extends to the control shaft 102 side, and a rocker having a hole 104a that engages with the eccentric cam 102a of the control shaft 102 The arm 104 is pivotally attached to one end. The upper end of the second link 105 is pivotally attached to the other end of the rocker arm 104, and the lower end of the second link 105 is attached to an output cam 106 that is swingably attached to the drive shaft 101. It arrange | positions so that it may contact | abut. The output cam 106 is in contact with the upper surfaces of a pair of cylindrical valve lifters 107, and each valve lifter 107 is in contact with the upper end of the stem of the valve 108.

  A position sensor 109 for detecting the rotational position is attached to one end of the control shaft 102, and is connected to the nut 5 via the third link 110. The nut 5 and the screw shaft 4 are coupled so as to be able to convert rotational motion and axial motion, and are further coupled to the screw shaft 4 and the rotational shaft of the electric motor 1. The ECU 111 receives a signal from the position sensor 109 and controls the drive of the electric motor 1 accordingly.

  2 is a side view of the ball screw mechanism of FIG. 1, and FIG. 3 is a view of the ball screw mechanism of FIG. 2 taken along line III-III and viewed in the direction of the arrow. In FIGS. 2 and 3, the electric motor 1 and the third link 110 are omitted.

  In FIG. 3, the screw shaft 4 whose left end is connected to an electric motor (not shown) is rotatably supported by bearings 6 and 7 with respect to the housing H in the cylindrical portions 4 a and 4 a formed at both ends and in the axial direction. It is supported immovably. A male screw groove 4 b (only a part of which is shown) is formed on the central outer peripheral surface of the screw shaft 4. The substantially cylindrical nut 5 is arranged so as to surround the screw shaft 4 and forms a female screw groove (not shown) on the inner peripheral surface. A ball (not shown) is disposed so as to be freely rollable between both screw grooves facing each other. The screw shaft 4, the nut 5, and a ball (not shown) constitute a ball screw mechanism.

  A connecting portion 5 a for connecting to the third link 110 (FIG. 1) is formed on the nut 5. A tube 5b for circulating the ball is provided at a notched portion in the lower center of the nut 5.

  The housing H is provided with a tapered groove G composed of a pair of slopes, and the nut 5 is disposed in contact with the opposing slope 5c. The length in the longitudinal direction of the groove G is longer than the entire length of the nut 5, and therefore the nut 5 can move in the axial direction along the groove G. Since the tube 5b is in a notch near the axis on the outer peripheral surface of the nut 5, it does not contact the groove G. In the present embodiment, the opposing inclined surface 5c of the nut 5 and the groove G of the housing H constitute a suppressing means.

  The operation of the valve mechanism of the present embodiment will be described. When the drive shaft 101 rotates in synchronization with a crankshaft (not shown), the eccentric cam 101a performs an eccentric motion to reciprocate the first link 103 up and down. When the first link 103 reciprocates up and down, the rocker arm 104 swings accordingly. As the rocker arm 104 swings, the second link 105 reciprocates up and down to swing the output cam 106. As the output cam 106 swings, the valve 108 reciprocates via a valve lifter 107 that abuts on the output cam 106.

  As described above, the electric motor 1 is driven by the drive control of the ECU 111, and the screw shaft 4 rotates together with the rotation shaft thereof. Therefore, the rotation is smoothly converted into the axial movement of the nut 5, and the third link. As the 110 moves, the control shaft 102 is rotationally displaced. Since the eccentric cam 102a is rotationally displaced according to the rotational position of the control shaft 102, and thereby the rocker arm 104 is displaced, a desired valve timing or the like can be set accordingly.

  FIG. 4 is a diagram illustrating changes in the position of the rocker arm 104 and the lift amount of the valve 108. For example, Δ1 (FIG. 4B), which is the difference between the top dead center (a) and the bottom dead center (b) when the control shaft 102 is set to the positions of FIGS. Compared to Δ2 (FIG. 4 (d)), which is the difference between the top dead center (c) and the bottom dead center (d) when the control shaft 102 is set to the position of FIGS. 4 (c) and 4 (d). can do. Furthermore, by rotating the control shaft 102 in synchronism with the drive shaft 101, the valve timing and phase can be changed.

  Here, a high-frequency force repeated in the forward and reverse directions generated by the rotation of the drive shaft 101 during operation of the internal combustion engine is transmitted from the valve mechanism side to the control shaft 102, and further via the control shaft 102, It is also transmitted to the mechanism. According to the present embodiment, the inclined surface of the groove G abuts on the opposed inclined surface 5c of the nut 5 to suppress the radial displacement thereof, thereby reducing high-frequency vibrations in the nut 5, and the screw shaft 4, the nut 5, Even when the relative clearance between the balls is relatively large, the collision between them can be mitigated, and the generation of abnormal noise and noise can be suppressed. Further, the nut 5 can be prevented from rotating by the pair of opposed inclined surfaces 5c coming into contact with the inclined surface of the groove G. That is, the rotation prevention of the nut 5 and the suppression of the displacement in the radial direction can be achieved at the same time.

  FIG. 5 is a side view of a ball screw mechanism according to a second embodiment that can be used in the valve mechanism shown in FIG. 1, and FIG. 6 is a cross-sectional view of the ball screw mechanism of FIG. And it is the figure seen in the direction of an arrow. 5 and 6, the electric motor 1, the third link 110, and the bearings 6 and 7 are omitted.

  The ball screw mechanism of the present embodiment differs from the embodiment of FIGS. More specifically, a guide shaft GS is spanned between a pair of pillar portions P, P formed in the housing H. Further, a raised portion 5d 'bulging in the radial direction is formed on the outer peripheral surface of the nut 5', and the guide shaft GS is inserted into the through hole 5e 'of the raised portion 5d'. Therefore, the nut 5 'can move in the axial direction along the guide shaft GS. In the present embodiment, the through hole 5e 'of the nut 5' and the guide shaft GS constitute a suppressing means. Further, the nut 5 'can be prevented from rotating by the engagement between the through hole 5e' and the guide shaft GS. Other configurations are the same as those in the embodiment shown in FIGS.

  According to the present embodiment, since the guide shaft GS is inserted through the through hole 5d ′ of the nut 5 ′ and the radial displacement thereof is suppressed, high-frequency vibration in the nut 5 ′ is thereby reduced, and the screw shaft 4 and nut 5 ′, even when the relative clearance between the balls is relatively large, the collision between them can be mitigated, and therefore the generation of abnormal noise and noise can be suppressed. Further, when the through hole 5e 'engages with the guide shaft GS, the nut 5' can be prevented from rotating. That is, the rotation prevention of the nut 5 ′ and the suppression of the radial displacement can be achieved at the same time.

  FIG. 7 is a side view of a ball screw mechanism according to a third embodiment that can be used in the valve mechanism shown in FIG. FIG. 8 is a view of the configuration of FIG. 7 taken along line VIII-VIII and viewed in the direction of the arrow. In FIG. 7, the electric motor 1 and the third link 110 are omitted.

  The ball screw mechanism of the present embodiment differs from the embodiment of FIGS. This will be described more specifically. The nut 5 ″ is formed with a pair of nut surfaces 5f ″ formed by cutting the outer peripheral surface of the nut 5 ″ along a plane parallel to the axis. The other circumferential surface connected to the nut surface 5f ″ is a part of the cylindrical surface. On the other hand, the inner shape of the resin collar 8 matches the outer shape of the nut 5 ″. A pair of inner peripheral planes 8 a corresponding to 5 f ″ is formed. Further, a pair of outer peripheral planes 8 b corresponding to the side surfaces of the groove G having a rectangular cross section formed in the housing H is formed on the outer peripheral surface of the collar 8. The outer peripheral surface of the collar 8 is in contact with the side surface and the bottom surface of the groove G in at least three places, and the phases of the inner peripheral plane 8a and the outer peripheral plane 8b of the collar 8 are shifted by 90 degrees. The collar 8 is prevented from falling off the nut 5 ″ by the retaining ring 9 attached to the retaining ring groove 5g ″ of the nut 5 ″. Other configurations are the same as those in the embodiment shown in FIGS. The nut surface 5f ″ of the nut 5 ″, the collar 8, and the groove G of the housing H constitute a restraining means.

  According to the present embodiment, since the collar 8 is interposed between the outer periphery of the nut 5 ″ and the groove G of the housing H, the radial displacement of the nut 5 ″ is suppressed. Even when the relative clearance between the screw shaft 4, the nut 5 ″, and the ball is relatively large, the collision between them can be mitigated, and the generation of abnormal noise and noise can be suppressed. Further, when the collar 8 has a cross section in the direction perpendicular to the axis, it has an outer peripheral surface 8b and an inner peripheral surface 8a that are at least partially non-circular, and these correspond to the corresponding surfaces of the nut 5 '' and the groove G of the housing H. , Respectively, to prevent rotation of the nut 5 ″ and to suppress radial displacement at the same time.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate. For example, the engagement between the restraining means and the nut includes a case where the restraining means and the nut are actually brought into contact with each other with a minute gap therebetween.

It is a perspective view of the valve operating mechanism which can change the valve timing and valve lift concerning this Embodiment. It is a side view of the ball screw mechanism concerning a 1st embodiment. It is the figure which cut | disconnected the ball screw mechanism of FIG. 2 by the III-III line | wire, and looked at the arrow direction. It is a figure which shows the position of the rocker arm 104, and the change of the lift amount of the valve | bulb. It is a side view of the ball screw mechanism concerning a 2nd embodiment. It is the figure which cut | disconnected the ball screw mechanism of FIG. 5 by the VI-VI line and looked at the arrow direction. It is a side view of the ball screw mechanism concerning a 3rd embodiment. It is the figure which cut | disconnected the structure of FIG. 7 by the VIII-VIII line, and looked at the arrow direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric motor 4 Screw shaft 5, 5 ', 5 "Nut 6, 7 Bearing 8 Collar 9 Retaining ring 101 Drive shaft 101a Eccentric cam 102 Control shaft 102a Eccentric cam 103 Link 104 Rocker arm 105 Second link 106 Output cam 107 Valve lifter 108 Valve 109 Position sensor 110 Third link
C Cylindrical part G Groove GS Guide shaft H Housing P Column

Claims (4)

In the valve mechanism that can change the open / close state of the valve,
A control shaft that changes the open / closed state of the valve by rotational displacement;
An electric motor;
A ball screw mechanism that transmits the power of the electric motor to the control shaft;
The ball screw mechanism is opposed to a screw shaft that is rotationally driven by the electric motor and has a male screw groove formed on an outer peripheral surface thereof, and a nut that is disposed so as to surround the screw shaft and has a female screw groove formed on an inner peripheral surface thereof. It has a plurality of balls arranged so as to be able to roll between both screw grooves, and a restraining means for preventing rotation of the nut and restraining displacement in the radial direction by engaging with the nut. Valve mechanism.   The valve mechanism according to claim 1, wherein the suppressing means includes a groove provided in the housing and engaging with the nut and extending in an axial direction.   2. The valve operating mechanism according to claim 1, wherein the suppressing means includes a guide shaft provided in the housing and engaged with the nut and extending in the axial direction. The restraining means is disposed between the nut and the housing, and includes a collar having an outer peripheral surface and an inner peripheral surface, at least a part of which is non-circular when taken in an axial orthogonal cross section. The valve operating mechanism according to claim 1.

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