PHASE VARYING DEVICE OF ENGINE

TECHNICAL FIELD

The present invention relates to a phase varying device of an engine of an automobile that transmits rotation of a crankshaft of the automobile engine to a camshaft for opening/closing an intake valve or an exhaust valve of the engine and varies open/close timing of the intake valve or the exhaust valve according to an operating condition such as an engine load and revolutions.

BACKGROUND ART

As this type of phase varying device, one as disclosed in the following Patent Document 1 proposed by the present inventor et al. has been known. This is shown in FIG. 7.

The phase varying device is used in a manner fitted to an unillustrated engine case (a cover for the phase varying device) since the intake valve or the exhaust valve is opened/closed, and includes an annular outer casing section 10 having a sprocket 12 to which a driving force of a crankshaft of an engine is transmitted by an unillustrated chain, an annular inner casing section 20 arranged coaxially with the outer casing section 10, capable of rotating relatively to the outer casing section 10, and forming a part of a camshaft 2, an intermediate member 30 interposed between the outer casing section 10 and the inner casing section 20 while being respectively engaged with the outer casing section 10 and the inner casing section 20 through helical splines and moving in an axial direction thus varying the phase of the inner casing section 20 with respect to the outer casing section 10, and an electromagnetic brake 40 being an electromagnetic control means provided at a side of the inner casing section 20 opposite the side where the camshaft 2 is disposed and moving the intermediate member 30 in the axial direction. On the camshaft 2, provided is a cam 2a for opening/closing one of the intake valve or exhaust valve.

The outer casing section 10 is composed of the sprocket 12 provided with a ring-shaped concave portion 13 at an inner periphery thereof, an inner flange plate 14 closely adhered to a side surface of the sprocket 12 and designing a flange engagement groove 13A in cooperation with the concave portion 13, and a spline case 16 fixing the inner flange plate 14 to the sprocket 12 by tightening together and formed with a spline engagement portion 17 with the intermediate member 30 at an inner circumference thereof. By a large-diameter concave portion at an opening side of the concave portion 13 of the outer casing section 10 and a small-diameter concave portion 13b at an inner side of the concave portion 13, a step portion 13c facing directly to an outer periphery of a flange 24 at the side of the inner casing section 20 is provided between both concave portions 13a and 13b. The sprocket 12, inner flange plate 14, and spline case 16 are integrated by a tightening screw 11, which therefore facilitates formation of the flange engagement groove 13A and the spline engagement portion 17 in the spline case 16.

In addition, a small-diameter sprocket 12A is fixedly fitted to the outer casing section 10, and although not illustrated, the small-diameter sprocket 12A is coupled with a sprocket of the phase varying device for opening/closing the other of the intake valve or exhaust valve by a chain, for controlling both the intake valve and exhaust valve.

Meanwhile, female and male helical splines 32 and 33 are provided on inner and outer circumferential surfaces of the intermediate member 30, male helical splines 23 are provided on an outer peripheral surface of the inner casing section 20, and female helical splines are formed at the spline engagement portion 17 of an inner circumferential surface of the spline case 16. Moreover, the inner and outer splines 32 and 33 of the intermediate member 30 are provided as helical splines in opposite directions so that a slight movement of the intermediate member 30 in the axial direction can greatly vary the phase of the inner casing section 20 with respect to the outer casing section 10. A male screw portion 31 is formed on the outer circumferential surface of the intermediate member 30.

The electromagnetic brake 40 is composed of an electromagnetic clutch 42 for which an electromagnet (electromagnetic coil) 62 is provided in a clutch case 60 and a friction material 66 is fixedly fitted to the clutch case surface, a rotary drum 44 made of a ferromagnetic material for receiving a braking force from the friction material 66 of the electromagnetic clutch 42, and a torsion coil spring 46 axially interposed between the rotary drum 44 and the outer casing section 10. Pins 68 are engaged with holes provided in the engine case, so that the electromagnetic clutch 42 is supported on the engine case so as to be movable in the axial direction but not be rotatable. The rotary drum 44 is supported so as to be rotatable on the inner casing section 20 by a bearing 22 and is formed with a female screw portion 45 to be screwed with the male screw portion 31 of the intermediate portion 30. When the rotary drum 44 rotates relatively to the outer casing section 10, the intermediate member 30 moves in the axial direction as a result of the work of both screw sections 45 and 31.

When the electromagnetic clutch 42 is off, since the braking force does not work on the rotary drum 44, the rotary drum 44 and outer casing section 10 are fixed at their initial positions by the torsion coil spring 46, the outer casing section 10, inner casing section 20, intermediate member 30, and rotary drum 44 integrally rotate, and no phase difference occurs between the outer casing section 10 and the inner casing section 20. Then, since the inner casing section 20 has been coupled to the camshaft 2 and the outer casing section 10 has been coupled with a crank pulley provided on the crankshaft by a chain, the intake valve or exhaust valve can be opened/closed at a normal timing according to rotation of the crankshaft.

When the electromagnetic clutch 42 is turned on, a frictional braking force acts on the friction material 66 provided on the electromagnetic clutch 42 and the rotary drum 44. When the braking force acts on the rotary drum 44, the rotary drum 44 experiences a rotational delay with respect to the outer casing section 10, the intermediate member 30 moves rightward in FIG. 7 as a result of the work of the spring portions 31 and 45, and owing to the inner and outer helical splines 32 and 33 of the intermediate member 30, the inner casing section 20 rotates relatively to the outer casing section 10, so that the phase difference between both varies. Then, the rotary drum 44 is held at a position where the braking force balances with a spring force of the torsion coil spring 46. By controlling current to be supplied to the electromagnet of the electromagnet clutch 42, the inner casing section 20 and outer casing section 10 can be controlled to have a desired phase difference. Thereby, the open/close timing of the intake valve or exhaust valve can be appropriately varied.

When the electromagnetic clutch 42 is again turned off, the braking force no longer works on the rotary drum 44, the intermediate member 30 rotates to its initial position as a result of the action of the torsion coil spring 46 and moves leftward in FIG. 7 to the initial position as a result of the work of the screw portions 31 and 45. Then, the inner casing section 20 rotates to an initial position in a reverse direction with respect to the outer casing section 10 to eliminate the phase difference between both, and the intake valve or exhaust valve is opened/closed at a normal timing.

Meanwhile, friction torque adding members 51 and 55 are interposed between the flange 24 of the inner casing section 20 and sides of the flange engagement groove 13A of the outer casing section 10 so as to increase friction torque of a relative sliding portion between the outer casing section 10 and the inner casing section 20 and suppress gear rattle of the tooth portions hitting against each other from occurring at the helical spline engagement portions 23, 32, 33, and 17 between the intermediate member 30 and the outer casing section 10 and inner casing section 20.

Moreover, the phase varying device is internally supplied with engine oil through an inlet 73a of the camshaft 2, an oil channel in the camshaft 2, and an outlet 73b. The engine oil that has exited the outlet 73b is supplied to a sliding surface between the friction material 66 provided on the surface of the electromagnetic clutch 42 and the rotary drum 44 so as to prevent overheating between the friction material 66 and the rotary drum 44 owing to friction (see the following Patent Document 1 for details).

Patent Document 1: Japanese Published Unexamined Patent Application No. 2002-371814.
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention

As described above, in the abovementioned phase varying device, when the sliding surface temperature reaches a high temperature owing to frictional heat on the relative sliding surface between the friction material 66 and the rotary drum 44, there is a possibility that the surface of the friction material generally formed of a porous material clogs up with reactants and insoluble contents of additives such as an antioxidant, a friction adjuster, and a detergent/dispersant dispersed in the engine oil and friction torque generated at the friction material 66 and rotary drum 44 is lowered, so that a cooling mechanism to allow the engine oil to flow between the friction material 66 and the rotary drum 44 is indispensable. Since the cooling mechanism is formed, the phase varying device has a complicated structure, thus resulting in a high cost, wherein a problem resides.

The present invention has been made in view of the problems described above and an object thereof is to prevent heat generation owing to friction in a phase varying device of an automobile engine.

Means for Solving the Problems

In order to achieve the aforementioned object, according to a first aspect of the invention, in a phase varying device of an engine including: an outer casing section having a sprocket to which rotation of a crankshaft of the engine is transmitted; an inner casing section capable of rotating relatively to the outer casing section and coupled with a camshaft for opening/closing an intake valve or an exhaust valve of the engine; and an intermediate member meshing with the outer casing section and the inner casing section through helical splines, relative rotation being generated between the outer casing section and the inner casing section by moving the intermediate member in an axial direction thus varying an open/close timing of the intake valve or the exhaust valve, the phase varying device of an engine is provided with an electromagnetic control means having a rotary drum being screwed on the intermediate member and provided as a permanent magnet and an electromagnetic clutch for braking the rotary drum.

According to a second aspect of the invention, in the first aspect of the invention, a plurality of magnetic poles are formed on the rotary drums, and by arranging electromagnets in the electromagnetic clutch so that magnetic poles corresponding to the magnetic poles are also formed and changing polarity of the electromagnets with an appropriate phase relative to the magnetic poles of the rotary drum, the rotary drum is braked or accelerated.

According to a third aspect of the invention, in the first or second aspect of the invention, the electromagnetic clutch is disposed in proximity to an interior side surface of the rotary drum.

According to a fourth aspect of the invention, in the first or second aspect of the invention, only a vicinity of an outer circumference of the rotary drum is magnetized, and the electromagnetic clutch is arranged in proximity to the vicinity of the outer circumference of the rotary drum.

Effects of the Invention

By the phase varying device according to the first aspect of the invention, since the rotary drum is braked by an electromagnetic force between the electromagnets of the electromagnetic clutch and the rotary drum being a permanent magnet, no friction material is necessary. In addition, since the phase varying device never reaches a high temperature owing to frictional heat resulting from contact between the friction material of the electromagnetic clutch and the rotary drum, an effect to reduce deterioration of an engine oil is provided. In addition, no cooling mechanism for the electromagnetic clutch and rotary drum is necessary, so that not only is the structure simplified, but also malfunction hardly occurs and life is prolonged. Furthermore, for the phase varying device, the engine oil for cooling can be reduced, and no friction material is necessary, which is economical.

By the second aspect of the invention, furthermore, a plurality of magnetic poles are formed on the rotary drums, and by arranging electromagnets in the electromagnetic clutch so that magnetic poles corresponding to the magnetic poles are also formed and changing polarity of the electromagnets with an appropriate phase relative to the magnetic poles of the rotary drum, a suction force or a repulsive force can be freely continuously generated between the electromagnetic clutch and the rotary drum, so that the rotary drum is freely braked or accelerated. Therefore, in the phase varying device, since the electromagnetic clutch 42 allows both braking and acceleration of the rotary drum 44, a torsion coil spring to return the rotary drum 44 to its initial position is no longer necessary, and the number of components can be reduced.

By the third aspect of the invention, furthermore, since the electromagnetic clutch is disposed in proximity to an interior side surface of the rotary drum, the entire length of the phase varying device can be made shorter than that of the conventional device where the electromagnetic clutch is disposed in proximity to an exterior side surface of the rotary drum. In addition, when the entire length the same as that of the conventional art is allowable, the moving range of the intermediate member in the axial direction can be increased, so that the phase can be varied in a wider range than that of the conventional art.

By the fourth aspect of the invention, furthermore, since only a vicinity of an outer circumference of the rotary drum is magnetized and the electromagnetic clutch is arranged in proximity to the vicinity of the outer circumference of the rotary drum, the entire length of the phase varying device can be further shortened. In addition, since the electromagnetic clutch is not provided lateral to the rotary drum, the rotary drum can also be reduced in diameter to reduce the moment of inertia so as to improve the phase varying device in responsiveness. Furthermore, even when the rotary drum moves in an axial direction, the rotary drum and electromagnetic clutch are always kept at an equal distance, so that highly accurate and stable phase control becomes possible.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, embodiments of the present invention will be described based on drawings.

A first embodiment according to an electromagnetic brake of a phase varying device of the present invention is shown in FIG. 1 and FIG. 2. FIG. 1(A) is a longitudinal sectional view of the phase varying device, FIG. 1(B) is a front view of a rotary drum 44 of the phase varying device, and FIG. 1(C) is a front view of an electromagnetic clutch 42 of the phase varying device. FIG. 2 is a diagram showing a current supplying circuit to electromagnets 62 of the electromagnetic clutch 42.

The phase varying device of the present embodiment is the same as the abovementioned conventional phase varying device except for an electromagnetic control means 40a formed of the rotary drum 44 and electromagnetic clutch 42 to be described later and the current supplying circuit to the electromagnets 62 to be also described later. In the following, with respect to the present embodiment, description will be given of the electromagnetic control means 40a and current supplying circuit to the electromagnets 62 while description of parts the same as those in the conventional device will be omitted.

In the electromagnetic control means 40a of the phase varying device, as shown in FIG. 1(B), the rotary drum 44 is provided as a permanent magnet strongly magnetized toward an axial direction so that six magnetic poles N and S of an alternate N-pole and S-pole appear along a circumferential direction, and as shown in FIG. 1(C), the electromagnetic clutch 42 is arranged in proximity to an exterior side surface of the rotary drum 44, and the three electromagnets (electromagnetic coils) 62 connected in series are arranged in a clutch case at positions corresponding to the magnetic poles N and S of the rotary drum 44 along a circumferential direction. Moreover, the electromagnetic control means 40a is not provided with a torsion coil spring to urge the rotary drum 44 to its initial position, and furthermore, the electromagnetic clutch 42 is not movable in axial and radial directions with respect to the engine case 58 or not provided with a friction material that slidingly contacts the rotary drum 44.

The current supplying circuit to the electromagnets 62 is formed of, as shown in FIG. 2, four current controllers (transistors) 64a to 64d that control a current supplied from a power source Vcc to the electromagnets 62 and a controller 65 that sends control signals to the respective current controllers 64a to 64d. By alternately turning on and off a pair of the current controllers 64a and 64d located diagonally to each other and another pair of current controllers 64b and 64c located diagonally to each other by the control signals from the controller 65, polarity of the electromagnets can be alternately changed. At this time, when a relative phase of the electromagnets 62 to the magnetic poles N and S of the rotary drum 44 is detected with an unillustrated appropriate rotation detection sensor so as to synchronize polarity switching of the current supplied to the electromagnets 62 with rotation of the rotary drum 44 and carry out control with an appropriate phase (a phase lag or a phase lead) relative to the magnetic poles N and S, it is possible to make only either a suction force or a repulsive force work continuously between the respective magnets 62 and the rotary drum 44, whereby the rotary drum 44 can be freely braked or accelerated.

In addition, to the controller 65, signals from unillustrated rotation detection sensors respectively provided on an unillustrated crank pulley and camshaft 2 have been received, and the controller 65 detects a phase of the camshaft 2 with respect to the crank pulley. And, the controller 65 calculates a command phase difference according to engine revolutions, an accelerator position, and the like so as to control the phase of the camshaft 2 with respect to the crank pulley. Namely, the controller 65 sends control signals to the respective current controllers 64a to 64d to brake or accelerate the rotary drum 44 until the phase difference between the crank pulley and camshaft 2 equals the command phase difference and controls the phase difference between the crank pulley and camshaft 2 so as to coincide with the command phase difference. The rotation detection sensor used here to detect a phase of the camshaft 2 with respect to the crank pulley can also be used as a phase detection sensor of the electromagnets 62 to the magnetic poles N and S of the rotary drum 44 described above.

According to the phase varying device of the present embodiment, since the rotary drum 44 is braked or accelerated by a suction force or a repulsive force between the electromagnets 62 of the electromagnetic clutch 42 and the rotary drum 44, no friction is generated between both, and therefore no friction material is necessary for the electromagnetic clutch 42. In addition, according to the phase varying device, since the electromagnetic control means 40a never reaches a high temperature owing to frictional heat, no cooling mechanism is necessary, so that the structure is also simplified, and malfunction hardly occurs and life is prolonged. Moreover, engine oil for cooling can be reduced, and no friction material is necessary, which is economical. Furthermore, since the electromagnetic clutch 42 allows both braking and acceleration of the rotary drum 44, a torsion coil spring to return the rotary drum 44 to its initial position is no longer necessary, and the number of components can be reduced.

In FIG. 3, a second embodiment according to a phase varying device of the present invention is shown. FIG. 3(A) is a longitudinal sectional view of the phase varying device, FIG. 3(B) is a front view of a rotary drum 44 of the phase varying device, and FIG. 3(C) is a front view of an electromagnetic clutch 42 of the phase varying device.

The phase varying device is, as shown in FIG. 3(A), different from the aforementioned first embodiment in the arrangement of the electromagnetic clutch 42 and rotary drum 44 and the attaching method to an engine case 58. Namely, the electromagnetic clutch 42 is arranged in proximity to an interior side surface of the rotary drum 44 and is supported on a shaft portion 44a of the rotary drum 44 via a bearing 43 or the like. Furthermore, a pin 42a provided on the electromagnetic clutch 42 is engaged with a rotation preventing groove 58a of the engine case 58 to restrict the electromagnetic clutch 42 from rotating. As a result of the engagement between the rotation preventing groove 58a and the pin 42a, the electromagnetic clutch 42 can move in an axial direction while keeping a distance from the rotary drum 44 fixed. Other aspects are the same as those of the aforementioned first embodiment.

According to the phase varying device of the present embodiment, since the electromagnetic clutch 42 is arranged inside the rotary drum 44, the entire length can be made shorter than that of the aforementioned first embodiment. In addition, since the electromagnetic clutch 42 keeps the distance from the rotary drum 44 fixed, a braking force or an accelerating force applied to the rotary drum 44 is kept fixed, so that highly accurate and stable phase control becomes possible.

In FIG. 4, a third embodiment according to a phase varying device of the present invention is shown. FIG. 4(A) is a longitudinal sectional view of the phase varying device, FIG. 4(B) is a front view of a rotary drum 44 of the phase varying device, and FIG. 4(C) is a front view of an electromagnetic clutch 42 of the phase varying device.

The phase varying device is, as shown in FIG. 4(A), different from the aforementioned first embodiment in the point that the electromagnetic clutch 42 is arranged in proximity to an outer circumference of the rotary drum 44 and, as shown in FIG. 4(B), only a vicinity of the outer circumference of the rotary drum 44 is magnetized, and is the same as the aforementioned first embodiment in other aspects. Here, since the magnitude of a magnetic force is greatly affected by the distance between the magnetic poles, even when only the vicinity of the outer circumference of the rotary drum 44 is magnetized, a sufficient magnetic force can be obtained as the magnetic poles N and S and the electromagnets 62 are close in distance.

According to the phase varying device of the present embodiment, since the electromagnetic clutch 42 is arranged at the outer circumferential side of the rotary drum 44, the entire length can be made shorter than that of the aforementioned first embodiment. In addition, since the electromagnetic clutch 42 is not arranged lateral to the rotary drum 44, the rotary drum 44 can be reduced in diameter to reduce the moment of inertia so as to improve the phase varying device in responsiveness. Furthermore, even when the rotary drum 44 moves in an axial direction, the rotary drum 44 and electromagnetic clutch 42 are always kept at an equal distance, so that highly accurate and stable phase control becomes possible.

However, the present invention is not limited to the aforementioned embodiments. For example, modifications can be made as follows.

The rotary drum 44 and electromagnetic clutch 42 can be modified as shown in FIG. 5 and FIG. 6. Here, FIG. 5(A) is a front view of the rotary drum 44 of the phase varying device, FIG. 5(B) is a sectional view along a line V-V of FIG. 5 (A), FIG. 6(A) is a front view of the electromagnetic clutch 42 of the phase varying device, and FIG. 6(B) is a side view of the electromagnetic clutch 42. Namely, it is not necessary to provide magnetic poles N and S formed on the rotary drum 44 alternately along the circumferential direction of the rotary drum 44 as in the aforementioned respective embodiments, the identical poles N (or S) may be arranged at equal intervals along the circumferential direction of the rotary drum 44 as shown in FIG. 5, it is not necessary for electromagnets 62 included in the electromagnetic clutch 42 to orient their axial directions along the circumferential direction of the electromagnetic clutch 42 as in the aforementioned respective embodiments, and these may be oriented in a direction orthogonal to the electromagnetic clutch 42 as shown in FIG. 6.

In addition, it is not necessary to provide the magnetic poles N and S formed on the rotary drum 44 as six poles as in the aforementioned respective embodiments, and the poles may be of any number equal to or more than two. As a matter of course, it is also not necessary to equalize the number of poles of the electromagnets 62 provided in the electromagnetic clutch 42 to the number of magnetic poles N and S formed on the rotary drum 44, and these may be arranged in any form with any number as long as a suction force or a repulsive force is continuously given to the rotary drum 44 by the electromagnets 62.

Furthermore, in the aforementioned second embodiment where the electromagnetic clutch 42 is arranged inside the rotary drum 44, the electromagnetic clutch 42 can move in the axial direction while keeping the distance from the rotary drum 44 fixed, however, in order to simplify the structure, the electromagnetic clutch 42 may be fixedly fitted to the engine case 58 so as not to be movable in the axial direction.

Furthermore, in the aforementioned respective embodiments, the electromagnetic control means 40a can carry out either braking or acceleration of the rotary drum 44, however, the electromagnetic control means 40a may carry out only braking. In this case, a torsion coil spring to urge the rotary drum 44 to its initial position is indispensable. Since such a torsion coil spring makes the engine drivable even when the electromagnetic clutch 42 has malfunctioned, a weak torsion coil spring may be provided in the aforementioned first to third embodiments as well.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Views explaining a phase varying device according to a first embodiment of the present invention.

FIG. 2 A diagram explaining a current supplying circuit to electromagnets of the phase varying device according to the first embodiment.

FIG. 3 Views explaining a phase varying device according to a second embodiment of the present invention.

FIG. 4 Views explaining a phase varying device according to a third embodiment of the present invention.

FIG. 5 Views explaining a modification of a rotary drum of a phase varying device according to the present invention.

FIG. 6 Views explaining a modification of an electromagnetic clutch of a phase varying device according to the present invention.

FIG. 7 A longitudinal sectional view of a conventional phase varying device.

DESCRIPTION OF REFERENCE NUMERALS

2 Camshaft

10 Outer casing section

12 Sprocket

20 Inner casing section

30 Intermediate member

40
a Electromagnetic control means

42 Electromagnetic clutch

44 Rotary drum

62 Electromagnet

N, S Magnetic pole

PHASE VARYING DEVICE OF ENGINE

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