WO2019054408A1

WO2019054408A1 - Variable valve timing device

Info

Publication number: WO2019054408A1
Application number: PCT/JP2018/033808
Authority: WO
Inventors: 齋藤　隆英; 佐藤　光司
Original assignee: Ntn株式会社
Priority date: 2017-09-15
Filing date: 2018-09-12
Publication date: 2019-03-21
Also published as: JP2019052601A

Abstract

Disclosed is a variable valve timing device provided with: a camshaft (1); a sprocket (2) which is disposed coaxially with the camshaft (1); and a varying mechanism part (3) which varies the phase of the camshaft (1) with respect to the sprocket (2). The varying mechanism part (3) comprises: an armature (6) that is supported so as to be movable in an axial direction; an electromagnet (7) that attracts the armature (6) in an axial direction when current is applied thereto; and a cam mechanism (8) that converts the axial movement of the armature (6) into rotation of the camshaft (1) relative to the sprocket (2).

Description

Variable valve timing device

The present invention relates to a variable valve timing device used in an engine valve system.

In an engine, a chain is bridged between a sprocket provided on a camshaft and a sprocket provided on a crankshaft, and the rotation of the crankshaft is transmitted to the camshaft through the chain, whereby a camshaft is obtained. The engine is rotationally driven, and the rotation of its camshaft drives the intake and exhaust valves of the engine.

Here, there is a time lag between the opening and closing of the intake and exhaust valves and the change of the actual gas flow, and the magnitude of the deviation varies with the flow rate of the intake and exhaust. Do. Therefore, when the engine is rotating at high speed and when it is rotating at low speed, the optimal opening / closing timing of the intake valve and the exhaust valve of the engine is different. Therefore, in order to optimize the opening and closing timings of the intake and exhaust valves of the engine, a variable valve timing device is used which changes the opening and closing timings of the intake and exhaust valves according to the rotational speed of the engine.

Variable valve timing devices generally include a camshaft that drives an intake or exhaust valve of an engine, a sprocket disposed coaxially with the camshaft, and a variable (that is, a relative angular position) of the camshaft relative to the sprocket. And a mechanical portion (see, for example, Patent Document 1).

The variable valve timing device of Patent Document 1 is an electric motor coaxially arranged with the camshaft as a variable mechanism portion for changing the phase of the camshaft with respect to the sprocket, and a difference for reducing the rotation of the electric motor and transmitting it to the sprocket And a dynamic reduction mechanism. The differential type reduction mechanism has an eccentric shaft connected to the output shaft of the electric motor, an annular internal gear connected to the camshaft, and an external gear connected to the sprocket. The ring-shaped internal gear and the external gear inscribed in the internal gear rotate relative to each other by one tooth each rotation.

When it is not necessary to change the phase of the camshaft with respect to the sprocket, the variable valve timing device of this patent document 1 rotates the electric motor at the same speed as the camshaft and uses it to make the phase of the camshaft relative to the sprocket constant. keep. On the other hand, when changing the phase of the camshaft with respect to the sprocket, the camshaft and the sprocket are rotated relative to each other by temporarily increasing or decreasing the rotation of the electric motor relative to the rotation of the camshaft. Change the phase.

JP, 2008-057349, A

The variable valve timing device of Patent Document 1 uses an electric motor and a differential reduction mechanism as a variable mechanism unit for changing the phase of the camshaft with respect to the sprocket, and manufactures such variable mechanism unit at low cost. It is difficult to do. In addition, it is necessary to change the rotation of the electric motor according to the rotation speed of the camshaft, and the control of the electric motor is complicated.

The problem to be solved by the present invention is to provide a variable valve timing device that can be manufactured inexpensively and is easy to control.

In order to solve the above-mentioned subject, in the present invention, the variable valve timing device of the following composition is provided.
With a camshaft,
A sprocket coaxially arranged with the camshaft;
A variable mechanism unit for changing the phase of the camshaft relative to the sprocket.
The variable mechanism unit
An armature movably supported in the axial direction;
An electromagnet for attracting the armature axially by energization;
A variable valve timing device, comprising: a cam mechanism for converting an axial movement of the armature to a relative rotation of the camshaft with respect to the sprocket.

In this case, since the electromagnet and the cam mechanism are used as the variable mechanism portion for changing the phase of the camshaft with respect to the sprocket, the device configuration is more efficient than using the electric motor and the differential reduction mechanism. It is simple and can be manufactured inexpensively. Further, control for arbitrarily changing the phase of the camshaft with respect to the sprocket merely switches between energization and interruption of the electromagnet, so control is easy.

It is preferable to provide a rotor connected to the sprocket so as to have a disk portion of a magnetic body positioned between the electromagnet and the axially opposed surface of the armature and to rotate integrally with the sprocket.

Thus, when the electromagnet is energized, the armature is attracted to the disc portion of the rotor that rotates integrally with the sprocket, and the armature rotates integrally with the sprocket. Therefore, the armature can be supported not on the side of the non-rotating electromagnet but on the side of the camshaft, which simplifies the device configuration.

The rotor may be configured to further include an inner diameter side cylindrical portion that axially extends from a radially inner end of the disk portion and is rotatably supported on an outer periphery of the camshaft. Here, the inner diameter side cylindrical portion may be supported on the outer periphery of the camshaft via a bearing, or may be supported directly on the outer periphery of the camshaft.

A rotation stopper may be provided between the rotor and the cam shaft to limit relative rotation of the cam shaft relative to the rotor to a predetermined angular range.

In this way, since the stop position of relative rotation when changing the phase of the camshaft with respect to the sprocket can be determined by the rotation stopper, it is possible to accurately manage the phase of the camshaft with respect to the sprocket.

As the cam mechanism,
A slide cam which is supported on the outer periphery of the camshaft so as to be axially movable and relatively non-rotatable with respect to the camshaft, and which is axially opposed to the sprocket;
A cam groove formed on the surface of the sprocket facing the slide cam;
A cam groove formed on the surface of the slide cam facing the sprocket;
A ball incorporated between the cam groove of the sprocket and the cam groove of the slide cam;
The slide cam may be one connected to the armature so as to move integrally with the armature in the axial direction.

In this way, it is possible to obtain a compact variable valve timing device in which the axial length of the cam mechanism is short.

The slide cam may adopt a spline fitted on the outer periphery of the camshaft.

Preferably, the slide cam is connected to the armature so as to move axially integrally with the armature in such a manner as to be rotatable relative to the armature.

In this way, when the armature is attracted to the rotor, the slide cam can rotate relative to the armature, so that the operation of the slide cam becomes stable.

An axial stopper can be provided on the outer periphery of the cam shaft to restrict an axial movement range of the slide cam.

Since the variable valve timing device according to the present invention uses the electromagnet and the cam mechanism as the variable mechanism portion for changing the phase of the camshaft with respect to the sprocket, it is possible to use the electric motor and the differential type reduction mechanism. The device configuration is simple and can be manufactured inexpensively. Further, control for arbitrarily changing the phase of the camshaft with respect to the sprocket merely switches between energization and interruption of the electromagnet, so control is easy.

Sectional view showing a variable valve timing device according to an embodiment of the present invention Sectional view along the line II-II in FIG. 1 The figure which expands and shows the vicinity of the connection part of the armature of FIG. 1, and a slide cam. Sectional drawing which shows the state which cut off electricity supply of the electromagnet shown in FIG. Sectional view along the line V-V in FIG. 4 Sectional drawing which shows the modification which provided the rotation stopper between the rotor and cam shaft of FIG. Sectional view along line VII-VII in FIG. 6 FIG. 7 is a cross-sectional view showing a state in which the phase of the camshaft in FIG.

FIG. 1 shows a variable valve timing device according to an embodiment of the present invention. This variable valve timing device changes the phase (relative angular position) of the camshaft 1 with respect to the sprocket 2 and the sprocket 2 coaxially arranged with the camshaft 1 for driving the intake or exhaust valve of the engine. And a variable mechanism unit 3.

A plurality of teeth 4 are formed on the outer periphery of the sprocket 2. The teeth 4 mesh with a chain (not shown) that transmits the rotation of a crankshaft (not shown) to the camshaft 1. The sprocket 2 is annular, and the shaft end of the camshaft 1 is inserted through the inside. The axial end of the camshaft 1 protrudes from the sprocket 2 to the side of the housing 5. The housing 5 is a stationary system.

The variable mechanism unit 3 includes an armature 6 axially movably supported with respect to the camshaft 1, an electromagnet 7 for attracting the armature 6 in the axial direction by energization, and axial movement of the armature 6 with respect to the sprocket 2. And a cam mechanism 8 for converting the relative rotation of the camshaft 1.

The electromagnet 7 is formed in an annular shape surrounding an axial end of the camshaft 1. The electromagnet 7 is fixedly attached to the housing 5. The electromagnet 7 has a field core 9 formed of a magnetic material and a coil 10 wound around the field core 9. The field core 9 includes an inner cylindrical portion 9a facing the inner diameter of the coil 10, an outer cylindrical portion 9b facing the outer diameter of the coil 10, and an end of the inner cylindrical portion 9a and the outer cylindrical portion 9b on the housing 5 side. And an annular plate portion 9c connecting the two. The coil 10 is composed of a wire wound annularly around the camshaft 1.

A rotor 12 is connected to the sprocket 2 via a rotor guide 11 so as to rotate integrally with the sprocket 2. The rotor guide 11 is fixed to a side surface of the sprocket 2 on the housing 5 side by a bolt 13. The rotor 12 is fixed to the inner periphery of the rotor guide 11.

The rotor 12 includes a disk portion 12a of a magnetic body disposed between axially opposed surfaces of the electromagnet 7 and the armature 6, an outer diameter side cylindrical portion 12b axially extending from the radial outer end of the disk portion 12a, and a disk And an inner diameter side cylindrical portion 12c extending in the axial direction from the radial inner end of the portion 12a. The outer diameter side cylindrical portion 12 b is press-fitted to the inner periphery of the rotor guide 11. Here, the inner diameter side cylindrical portion 12 c and the outer diameter side cylindrical portion 12 b extend in the axial direction toward the housing 5 with respect to the disk portion 12 a. Further, the outer diameter side cylindrical portion 12 b is disposed to face the outer diameter side of the outer cylinder portion 9 b of the field core 9, and the inner diameter side cylindrical portion 12 c faces the inner diameter side of the inner cylinder portion 9 a of the field core 9. Are arranged.

The inner diameter side cylindrical portion 12 c is supported on the outer periphery of the camshaft 1 via a bearing 14. Although the bearing 14 is a rolling bearing (for example, a needle roller bearing) in the drawing, a sliding bearing may be employed instead. Moreover, it is also possible to directly support the inner diameter side cylindrical portion 12 c on the outer periphery of the camshaft 1 without providing the bearing 14. In this case, it is preferable to provide a low-friction coating on one or both of the inner circumferential cylindrical surface of the inner diameter side cylindrical portion 12 c and the outer circumferential surface of the camshaft 1. An end plate 15 is fixed to the end face of the camshaft 1 by a bolt 16. The end plate 15 axially faces the end face of the inner diameter side cylindrical portion 12 c of the rotor 12 on the housing 5 side, and restricts the axial movement of the rotor 12. A low-friction treatment (for example, a low-friction coating or a low-friction layer is formed on the surface of the opposing portion between the end plate 15 and the end face of the inner side cylindrical portion 12c of the rotor 12 on the housing 5 side It is preferable to apply a plating treatment or the like, or to incorporate a thrust slide bearing or a thrust rolling bearing.

A slit 17 is formed in the disc portion 12 a of the rotor 12 at a position facing the armature 6. The slit 17 penetrates the disc portion 12 a in the axial direction. Further, the slits 17 are arc-shaped extending in a thin line on the circumference centering on the camshaft 1, and a plurality of the slits 17 are provided at intervals in the circumferential direction. By providing the slits 17, the magnetic flux flowing in the radial direction of the inside of the disk portion 12a of the rotor 12 is blocked by the slits 17 when the electromagnet 7 is energized, thereby increasing the density of the magnetic flux passing through the armature 6 It is possible to efficiently suction the armature 6 to the disc portion 12a. Between the axially opposed surfaces of the disk portion 12a of the rotor 12 and the armature 6, a separating spring 18 is incorporated which biases the armature 6 in the direction of separating it from the disk portion 12a.

The cam mechanism 8 includes a slide cam 19 disposed axially opposite to the sprocket 2, a cam groove 20 formed on the opposite surface of the sprocket 2 to the slide cam 19, and an opposite surface of the slide cam 19 to the sprocket 2. It has a cam groove 21 formed, and a ball 22 incorporated between the cam groove 20 of the sprocket 2 and the cam groove 21 of the slide cam 19.

As shown in FIGS. 2 and 5, the cam groove 20 and the cam groove 21 are formed to extend in the circumferential direction. Further, the cam groove 20 is formed to have a groove bottom inclined so as to be gradually deeper in one circumferential direction from the contact position with the ball 22, and the cam groove 21 is also circumferentially from the contact position with the ball 22. It is configured to have a groove bottom inclined so as to be gradually deeper toward the other direction. The ball 22 is, for example, a steel ball.

As shown in FIG. 1, the slide cam 19 has an outer diameter side from a cylindrical portion 19a penetrating between the outer circumference of the camshaft 1 and the inner circumference of the sprocket 2 and an end of the cylindrical portion 19a remote from the housing 5 The cam groove 21 is formed in the flange portion 19 b. The cylindrical portion 19 a of the slide cam 19 is spline-fitted to the outer periphery of the camshaft 1, and is supported on the outer periphery of the camshaft 1 so as to be axially movable with respect to the camshaft 1 and non-relatively rotatable.

As shown in FIG. 3, a cylindrical surface 23 rotatably supporting the inner periphery of the armature 6 is formed on the outer periphery of the end of the cylindrical portion 19 a of the slide cam 19, and the axial end face of the cylindrical portion 19 a of the slide cam 19 The armature 6 is prevented from coming off the slide cam 19 by caulking. Thus, the slide cam 19 is connected to the armature 6 so as to move integrally with the armature 6 in the axial direction so as to be rotatable relative to the armature 6. In FIG. 3, the caulking portion 30 formed by caulking the end face in the axial direction of the cylindrical portion 19a is accommodated in the concave portion 31 formed at the radially inner end of the contact surface of the armature 6 with the disc portion 12a of the rotor 12. It is done.

As shown in FIG. 1, on the outer periphery of the camshaft 1, an axial stopper 24 that restricts the axial movement range of the slide cam 19 is provided. The axial stopper 24 is disposed opposite to the slide cam 19 on the opposite side of the housing 5.

An operation example of this variable valve timing device will be described.

When the energization to the electromagnet 7 is cut off, as shown in FIG. 4, the armature 6 is separated from the rotor 12 by the force of the separation spring 18. At this time, the axial distance between the sprocket 2 and the flange 19 b of the slide cam 19 is relatively wide, and the slide cam 19 is in contact with the axial stopper 24. Further, as shown in FIGS. 4 and 5, the ball 22 is at a shallow position of the

cam grooves

20 and 21. In this state, the phase of the camshaft 1 with respect to the sprocket 2 is the phase of the most retarded angle (the position where the relative angular position of the camshaft 1 with respect to the sprocket 2 is shifted to the rearmost side in the rotational direction of the camshaft 1). That is, when the sprocket 2 rotates, the camshaft 1 rotates integrally with the sprocket 2 at the phase of the most retarded angle.

When the electromagnet 7 is energized, as shown in FIG. 1, the electromagnet 7 attracts the armature 6, and the armature 6 is attracted to the disk portion 12 a of the rotor 12. At this time, as the armature 6 moves in the axial direction, the axial distance between the sprocket 2 and the flange portion 19b of the slide cam 19 becomes narrower, and as shown in FIG. 1 and FIG. It rolls along the

grooves

20 and 21 in the direction in which the

cam grooves

20 and 21 become deeper, the slide cam 19 rotates relative to the sprocket 2, and the camshaft 1 rotates relative to the slide cam 19. Thereby, the phase of the camshaft 1 with respect to the sprocket 2 changes to the phase of the most advanced angle (the position where the relative angle position of the camshaft 1 with respect to the sprocket 2 is shifted to the frontmost side in the rotational direction of the camshaft 1). That is, when the sprocket 2 rotates, the camshaft 1 rotates integrally with the sprocket 2 at the phase of the most advanced angle.

Since the variable valve timing device uses the electromagnet 7 and the cam mechanism 8 as the variable mechanism portion 3 for changing the phase of the camshaft 1 with respect to the sprocket 2, it is possible to use an electric motor and a differential reduction mechanism. The apparatus configuration is simpler than that of forming the variable mechanism unit, and it is possible to manufacture at low cost. Further, since control for arbitrarily changing the phase of the camshaft 1 with respect to the sprocket 2 only switches between energization and interruption of the electromagnet 7, control is easy.

Further, in the variable valve timing device, when the electromagnet 7 is energized, the armature 6 is attracted to the disk portion 12 a of the rotor 12 that rotates integrally with the sprocket 2, and the armature 6 rotates integrally with the sprocket 2. Therefore, the armature 6 can be supported not on the side of the non-rotating electromagnet 7 but on the side of the camshaft 1, and the device configuration is simple.

Further, this variable valve timing device includes a slide cam 19 disposed axially opposite to the sprocket 2, a cam groove 20 formed on the surface of the sprocket 2 facing the slide cam 19, and a sprocket 2 of the slide cam 19. Since the cam mechanism 8 having the cam groove 21 formed on the opposite surface to the ball and the ball 22 incorporated between the cam groove 20 of the sprocket 2 and the cam groove 21 of the slide cam 19 is employed, the cam mechanism 8 is It is possible to obtain a compact variable valve timing device having a short axial length.

Further, since the variable valve timing device connects the armature 6 and the slide cam 19 so that relative rotation is possible, the slide cam 19 operates stably when the armature 6 is attracted to the rotor 12.

The modification of the said embodiment is shown in FIG.6, FIG.7, FIG.8. In this modification, a rotation stopper 25 for restricting relative rotation of the camshaft 1 with respect to the rotor 12 to a predetermined angle range is provided between the rotor 12 and the camshaft 1, and the other configuration is the same as the above embodiment. It is. Therefore, the parts corresponding to the above embodiment are given the same reference numerals and the description will be omitted.

The rotation stopper 25 is provided with a radially inward protrusion 26 provided at an end of the inner diameter side cylindrical portion 12 c of the rotor 12 on the housing 5 side, and an axial end portion of the camshaft 1 so as to accommodate the protrusion 26. It comprises with the recessed part 27 provided in the outer periphery. The recess 27 has a pair of inner side surfaces 28 and 29 opposed in the circumferential direction, and the pair of inner side surfaces 28 and 29 restricts the circumferential movement of the projection 26 within a predetermined angular range. The predetermined angle range is, for example, an angle range having a lower limit of 0 deg and a value set in a numerical range of 20 deg to 70 deg as an upper limit.

As in this modification, when the rotation stopper 25 for limiting the relative rotation of the camshaft 1 with respect to the rotor 12 to a predetermined angular range is provided between the rotor 12 and the camshaft 1, the phase of the camshaft 1 with respect to the sprocket 2 is changed. Since the stop position of relative rotation at the time of rotation can be determined by the rotation stopper 25, it is possible to accurately manage the phase of the camshaft 1 with respect to the sprocket 2. That is, as shown in FIG. 7, the position of the camshaft 1 when the phase of the camshaft 1 with respect to the sprocket 2 becomes the most advanced angle is set by the position of the camshaft 1 when the inner side surface 28 and the protrusion 26 contact. Of the camshaft 1 when the phase of the camshaft 1 with respect to the sprocket 2 is most retarded, depending on the position of the camshaft 1 when the inner surface 29 and the projection 26 come into contact with each other, as shown in FIG. You can set the position.

It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is indicated not by the above description but by the claims, and is intended to include all the modifications within the meaning and scope equivalent to the claims.

Reference Signs List 1 camshaft 2 sprocket 3 variable mechanism 6 armature 7 electromagnet 8 cam mechanism 12 rotor 12a disc 12c inner diameter side cylindrical portion 19 slide cam 20 cam groove 21 cam groove 22 ball 24 axial stopper 25 rotation stopper

Claims

With the camshaft (1),
A sprocket (2) disposed coaxially with the camshaft (1);
A variable mechanism (3) for changing the phase of the camshaft (1) with respect to the sprocket (2);
The variable mechanism unit (3)
An armature (6) axially movably supported;
An electromagnet (7) for attracting the armature (6) in the axial direction by energization;
And a cam mechanism (8) for converting the axial movement of the armature (6) into relative rotation of the camshaft (1) with respect to the sprocket (2).
It has a disk (12a) of magnetic material located between the opposing faces of the electromagnet (7) and the armature (6) in the axial direction, and is connected to the sprocket (2) so as to rotate integrally with the sprocket (2) A variable valve timing device according to claim 1, further comprising a rotor (12).
The rotor (12) further includes an inner cylindrical portion (12c) axially extending from a radially inner end of the disk portion (12a) and rotatably supported on the outer periphery of the camshaft (1). The variable valve timing device according to Item 2.
The rotary stopper (25) for restricting relative rotation of the camshaft (1) with respect to the rotor (12) to a predetermined angular range is provided between the rotor (12) and the camshaft (1). The variable valve timing device according to 3.
The cam mechanism (8) is
A slide cam (19) supported on the outer periphery of the camshaft (1) so as to be axially movable and relatively non-rotatable with respect to the camshaft (1) and axially opposed to the sprocket (2) )When,
A cam groove (20) formed on the surface of the sprocket (2) facing the slide cam (19);
A cam groove (21) formed on the surface of the slide cam (19) facing the sprocket (2);
The cam groove (20) of the sprocket (2) and a ball (22) incorporated between the cam groove (21) of the slide cam (19);
The variable valve timing device according to any one of claims 1 to 4, wherein the slide cam (19) is connected to the armature (6) so as to move axially integrally with the armature (6).
The variable valve timing device according to claim 5, wherein the slide cam (19) is splined on the outer periphery of the camshaft (1).
The slide cam (19) is connected to the armature (6) so as to axially move integrally with the armature (6) in a relatively rotatable manner with the armature (6). The variable valve timing device according to 6.
The variable valve timing device according to any one of claims 5 to 7, wherein an axial stopper (24) for restricting an axial movement range of the slide cam (19) is provided on an outer periphery of the camshaft (1).