Valve timing controller

Abstract

A valve timing controller has an electric motor, a control circuit which controls the motor, a first rotor that rotates along with a crankshaft, and a second rotor that is rotates along with a camshaft. A phase adjusting mechanism adjusts the rotational phase between the first rotor and the second rotor according to the rotation of the motor. On condition that the rotating speed of the crankshaft exceeds a threshold value, the control circuit stops the energization of the electric motor. Thereby, the phase adjusting mechanism varies the rotational phase to the most retard phase.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2006-275513 filed on Oct. 6, 2006, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a valve timing controller which adjusts valve timing of an inlet valve and/or an exhaust valve of an internal combustion engine.

BACKGROUND OF THE INVENTION

The valve timing controller varies the rotational phase between two rotors which respectively rotate along with a crankshaft and a camshaft to adjust the valve timing. JP-9-60509A and JP-2005-48706A, for example, disclosure the valve timing controller which adjusts the rotational phase between the rotors according to the rotation of the electric motor.

In such an electric valve timing controller, the electric motor is driven in the same phase as the rotors when holding the rotational phase. Therefore, when the rotating speed of the internal combustion engine increases, the rotating speed of the electric motor also increases. Moreover, generally in the high-rotation speed range of the engine, there are many cases where the rotational phase of the rotor is held to the phase suitable for the internal combustion engine. Since the electric motor is continuously driven by high current in the high-rotation range of the engine, there is a possibility of increasing of power consumption and generating heat of the motor control circuit, which may cause breakage of the circuit.

The present invention is made in view of the above matters, and it is an object of the preset invention to provide an electric valve timing controller which realizes valve timing suitable for the internal combustion engine, restraining power consumption and the malfunction.

SUMMARY OF THE INVENTION

According to the present invention, a valve timing controller adjusting a valve timing of an intake valve and/or an exhaust valve of an internal combustion engine, includes an electric motor which rotates by energization, and an energizing control circuit which controls the energization of the electric motor. The controller further includes a phase adjusting mechanism including a first rotor which rotates along with one of a crankshaft and a camshaft of the internal combustion engine, and a second rotor which rotates along with the other. The phase adjusting mechanism adjusts a rotational phase between the first rotor and the second rotor according to the rotation of the electric motor. In a case that a rotating speed of the internal combustion engine exceeds a threshold value, the energizing control circuit stops the energization of the electric motor so that the phase adjusting mechanism varies the rotational phase to an end phase which is one of a most retard phase and a most advance phase.

Since the energizing control circuit stops the energization of the electric motor in a high rotation range of the internal combustion engine, a power consumption of the electric motor is reduced and a malfunction due to heat generation is restricted. Furthermore, the energizing control circuit stops the energization of the electric motor so that the phase adjusting mechanism varies the rotational phase to an end phase. Hence, the end phase suitable for an engine in high speed range can be obtained in spite of deenergization of the electric motor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view showing a valve timing controller according to an embodiment of the present invention, taken along a line I-I in FIG. 2.

FIG. 2 is a cross sectional view taken along a line II-II in FIG. 1.

FIG. 3 is a cross sectional view taken along a line III-III in FIG. 1.

FIG. 4 is a diagram for explaining the fluctuation torque.

FIG. 5 is a graph for explaining actuation of the energizing control circuit.

FIG. 6 is a graph for explaining the characteristic of the phase adjusting mechanism.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, a first embodiment of the present invention is described. FIG. 1 shows the valve timing controller 1 according to the first embodiment of the present invention. The valve timing controller 1 is provided in the transmission system which transmits engine torque to the camshaft 2 from the crankshaft (not shown) of the internal combustion engine. The valve timing controller 1 includes a torque generating system 4 and a phase adjusting mechanism 8. In the present embodiment, the camshaft 2 opens/closes the intake valve (not shown), and the valve timing controller 1 adjusts the valve timing of the intake valve.

First, the torque generating system 4 is explained. The torque generating system 4 is provided with an electric motor 5 and a control circuit 6.

The electric motor 5 is, for example, a brushless motor. When energized, the electric motor generates controlling torque on its motor shaft 7. The control circuit 6 includes a microcomputer and a motor driver, and is arranged in exterior and/or interior of the electric motor 5. The control circuit 6 is electrically connected with the electric motor 5 to control the energization of the electric motor 5 according to the operation condition of the internal combustion engine.

Next, the phase adjusting mechanism 8 is explained hereinafter. The phase adjusting mechanism 8 is provided with the driving-side rotor 10, the driven-side rotor 20, the planetary carrier 40, and the planet gear 50.

The driving-side rotor 10 includes a gear member 12 and a sprocket 13 which are coaxially fixed together by a bolt. The driving-side rotor 10 has a chamber house 11 in which the driven-side rotor 20, the planetary carrier 40, and the planet gear 50 are accommodated. The peripheral wall part of the gear member 12 forms the driving-side internal gear 14 which has an addendum circle inside of a dedendum circle. The sprocket 13 has a plurality of gear teeth 16. A timing chain (not shown) is wound around the sprocket 13 and a plurality of teeth of the crankshaft so that the sprocket 13 is linked to the crankshaft. When the engine torque is transmitted to the sprocket 13 through the timing chain, the driving-side rotor 10 rotates in accordance with the crankshaft. In the present embodiment, the driving-side rotor 10 rotates in counterclockwise direction in FIGS. 2 and 3, and the rotating speed of the driving-side rotor 10 is half (½) of the rotating speed of the crankshaft.

As shown in FIGS. 1 and 2, the driven-side rotor 20 is formed in cup shape, and is concentrically arranged in the sprocket 13. The peripheral wall part of the driven-side rotor 20 forms a driven-side internal gear 22 which has an addendum circle inside of its dedendum circle. The driven-side internal gear 22 is engaged with an inner wall of the sprocket 13.

As shown in FIG. 1, the bottom wall part of the driven-side rotor 20 forms the connecting part 24 which is fixed on the camshaft 2 by a bolt. The driven-side rotor 20 is interlocked with the camshaft 2, and performs a relative rotation with respect to the driving-side rotor 10. Besides, in FIGS. 2 and 3, an arrow X shows an advance direction relative to the driving-side rotor 10, and an arrow Y shows a retard direction relative to the driving-side rotor 10.

As shown in FIGS. 1 to 3, the planetary carrier 40 is formed cylindrical and forms the input part 41 through which the controlling torque is inputted from the motor shaft 7. A plurality of engaging grooves 42 is provided for the input part 41. The planetary carrier 40 is connected to the motor shaft 7 through a joint 43 which engages with the engaging grooves 42. The planetary carrier 40 rotates along with the motor shaft 7, and performs a relative rotation with respect to the rotors 10, 20.

The planetary carrier 40 is provided with an eccentric portion 44 relative to the gears 14, 22. The eccentric portion 44 is engaged with an inner bore 51 of the planet gear 50 through a bearing 45.

The planet gear 50 is formed in a cylindrical shape with a step, and is coaxially arranged to the eccentric portion 44. That is, the planet gear 50 is eccentrically arranged with respect to the gears 14, 22. The planet gear 50 is provided with a driving-side external gear 52 and a driven-side external gear 54 on its large diameter portion and a small diameter portion. The gears 52, 54 respectively have the addendum circle outside of the dedendum circle. The driving side external-gear 52 is arranged in such a manner as to engage with the driving-side internal gear 14. The driven-side external gear 54 is arranged in such a manner as to engage with the driven-side internal gear 22. The planet gear 50 rotates around a center of the eccentric portion 44 and performs a planetary motion in a rotation direction of the eccentric portion 44.

The phase adjusting mechanism 8 is provided with a planetary mechanism 60 of the differential-gear type which reduces the speed of the electric motor and converts the rotation of the motor into a rotation of the driven-side rotor 20. And the phase adjusting mechanism 8 equipped with such a planetary mechanism 60 adjusts the rotational phase between the rotors 10 and 20 which determine the valve timing according to the rotation of the electric motor 5.

When the electric motor 5 adjusts the controlling torque in such a manner that the motor shaft 7 rotates in the same phase as the driving-side rotor 10, the planet gear 50 rotates the driven-side rotor 20 in the same phase as the driving-side rotor 10 while maintaining the engagement position with the gears 14 and 22. That is, since the electric motor 5 rotates along with the rotors 10 and 20, the rotational phase between the rotors 10 and 20 is not varied, so that the valve timing is held.

When the motor shaft 7 performs relative rotating in the advance direction X relative to the driving-side rotor 10, the planet gear 50 performs the planetary motion so that the driven-side rotor 20 performs relative rotating in the advance direction X relative to the driving-side rotor 10. That is, since the rotational phase of the driven-side rotor 20 is advanced relative to the driving-side rotor 10, the valve timing is also advanced.

When the motor shaft 7 performs relative rotating in the retard direction Y relative to the driving-side rotor 10, the planet gear 50 performs the planetary motion so that the driven-side rotor 20 performs relative rotating in the retard direction Y relative to the driving-side rotor 10. That is, since the rotational phase of the driven-side rotor 20 is retarded relative to the driving-side rotor 10, the valve timing is also retarded.

Next, the characterizing portion of the valve timing controller 1 is explained in detail.

(Stopper Structure)

As shown in FIGS. 1 and 2, a plurality of stopper groove portions 70 are provided for the sprocket 13 at its inner periphery in a circumferential direction. Moreover, the driven-side internal gear 22 is provided with a plurality of stoppers 72 which radially protrude along its circumferential direction. Each stopper 72 is respectively positioned in the corresponding stopper groove portion 70, and moves in the advance direction X and the retard direction Y. When at least one of these stoppers 72 is brought into abutment with edges 74 and 76 of the stopper groove portion 70, the adjustment end of the rotational phase between the rotors 10 and 20 will be decided uniquely.

Specifically, when at least one stopper 72 is contact with the edge 74 of advance direction X, the driven-side rotor 20 is stopped at the most advance phase relative to the driving-side rotor 10.

Meanwhile, when at least one stopper 72 is contact with the edge 76 of retard direction Y, the driven-side rotor 20 is stopped at the most retard phase relative to the driving-side rotor 10. Therefore, when the motor 5 is deenergized and the phase adjusting mechanism 8 varies the rotational phase of the driven-side rotor 20 in the retard direction, as shown in FIG. 2, the rotational phase reaches and is held at the most retard phase.

Here, in this embodiment, the most retard phase is established as a start up phase which permits start up of the internal combustion engine. So, even if the abnormalities of the control circuit 6 arise and the electric motor 5 is deenergized during the operation of the internal combustion engine, the rotational phase of the driven-side rotor 20 can be varied to the start up phase by the phase adjusting mechanism 8 for a next start up of the internal combustion engine.

(Lubrication Structure)

As shown in FIG. 1, a plurality of supply passages 80 which penetrate the connecting part 24 of the driven-side rotor 20 are formed in its circumferential direction. The inlet port of each supply passage 80 communicates with the introductory passage 3 where lubricant is introduced from the pump 9. Moreover, the outlet of each supply passage 80 communicates to the chamber houses 11. By this structure, the lubricant introduced during operation of the internal combustion engine to the introductory passage 3 is supplied to the planetary mechanism 60 through each supply passage 80, and lubrication is performed between the gear parts 22 and 54 and between the gear parts 14 and 52.

Thus, in the phase adjusting mechanism 8 equipped with the planetary mechanism 60 to which the lubricant is supplied, when the viscosity of the lubricant rises at the time of the low temperature, the controlling torque required to rotate the driven-side rotor 20 by the electric motor 5 increases. So, since the load of the electric motor 5 becomes excessive when required controlling torque increases according to other factors, it is not desirable. However, as shown in FIG. 4, the fluctuation torque is generated according to the drive reaction force of the intake valve during engine operation. When the fluctuation torque is transmitted to the driven-side rotor 20 from the camshaft 2 and acts on the motor shaft 7 through the phase adjusting mechanism 8, the required controlling torque is increased in order to rotate the driven-side rotor 20.

So, in the phase adjusting mechanism 8, the actual reduction ratio Rr between the motor shaft 7 and the driven-side rotor 20 expressed by the following formula (1) is established so that the required controlling torque due to the fluctuation torque is S % or less of the required controlling torque due to increment of viscosity. Besides, in the formula (1), Z1, Z2, Z3, and Z4 express the number of teeth of each gear parts 14, 22, 52, and 54, respectively.

Rr=(Z2/Z4·Z3/Z1)/(Z2/Z4·Z3/Z1−1)  (1)

Specifically, the required controlling torque due to the viscosity increment is denoted by Tc, the average torque of the fluctuation torque in the camshaft 2 is denoted by Tv (refer to FIG. 4), and the torque transmission efficiency from the driven-side rotor 20 to the motor shaft 7 is defined as E %. And the reduction ratio RI, which is required to rotate the driven-side rotor 20 against the average torque Tv of the fluctuation torque and to realize S %, is computed according to the following formula (2), and the actual reduction ratio Rr is established as the value more than the required reduction ratio RI. For example, in a case that Tc=0.4 Nm, Tv=3 Nm, E=60%, and S=5%, since it is computed that RI=90, the actual reduction ratio Rr is established greater than or equal to 90 (Rr≧90). Therefore, according to such a configuration, the load of the electric motor 5 can be reduced.

RI=(Tv−E)/(Tc−S)  (2)

(Energization Control)

As shown in FIG. 1, the rotation sensor 90 which detects the rotation of the crankshaft of the internal combustion engine is electrically connected to the energizing control circuit 6. The energizing control circuit 6 deduces the rotating speed of the crankshaft from the detection signal supplied from this rotation sensor 90 successively, and uses it for the energization control of the electric motor 5. And as shown in FIG. 5, the energizing control circuit 6 stops the energization of the electric motor 5 compulsorily and makes the current the zero value in the high rotation range Wh where the rotating speed of the crankshaft exceed the threshold value Nth. Thereby, the rotational phase between the rotors 10 and 20 is varied to the most retard phase.

Here, the most retard phase is established also as a phase which is suitable for the internal combustion engine of the high rotation numerical Wh in the point of the engine output as well as the start up phase. When the electric motor 5 is deenergized, the rotors 10, 20 are automatically held at the most retard phase. Some useless power consumptions and the malfunctions due to heat generation of the energizing control circuit 6 are restrained, and the output of the internal combustion engine improves.

As long as the desired output of the engine is obtained in the high rotation range Wh, the threshold value Nth is lower than a predetermined speed Na (refer to FIG. 5) in which the electric motor 5 rotates in the same phase as the rotors 10, at the maximum rotation speed Mm. In a middle-low rotation range Wml, the rotation speed of the electric motor 5 is always lower than the maximum rotation speed Mm when the electric motor 5 rotates in the same phase as the rotors 10, 20. Thus, it can be avoided that the rotation speed of the electric motor 5 runs short and the electric motor 5 does not rotate in the same phase as the rotors 10, 20. Besides, the maximum engine speed Mm of the electric motor 5 may be established previously in mechanism as a specification of the motor itself, or may be realized by the energizing control circuit 6 in control.

The predetermined speed Na of the crankshaft, which is determined according to the engine condition, is higher than the threshold Nth. Hence, the maximum rotation speed Mm of the electric motor 5 can be established as low as possible, so that a small size electric motor 5 can be used.

However, when the maximum rotation speed Mm of the electric motor 5 becomes low excessively, there is a possibility that the responsibility of the phase adjusting mechanism 8 may be deteriorated. So, in the phase adjusting mechanism 8, the actual reduction ratio Rr is established so that minimum response speed ω as a response speed of the rotational variation of the driven-side rotor 20 at the time of the rotational variation of the electric motor 5 can be realized with the maximum speed Mm of the electric motor 5. Besides, in the present embodiment, the minimum response speed ω is expressed as relative rotating angular velocity of the driven-side rotor 20 relative to the driving-side rotor 10 at the time of the rotational variation of the electric motor 5 in order to change the rotational phase between the rotors 10 and 20.

When the rotation of the electric motor 5 changes from the same phase as the driving-side rotor 10 to the maximum speed Mm, specifically, the deviation (=Mm−Ms) of the maximum speed Mm from the rotating speed Ms shows linear relation with respect to the rotating speed of the crankshaft, as shown in FIG. 6. In order to realize the minimum response speed ω at the time when a preset speed Mss (crankshaft speed is denoted by Nss in FIG. 6) is varied to the maximum rotation speed Mm, the required reduction speed ratio Rh is calculated according to the following formula (3) and the actual reduction speed ratio Rr is established. For example, in a case that Mm=3000 rpm, Mss=1000 rpm and ω=100 CA, since Mm−Mss=2000 rpm/60 s·720 CA and Rh=240, the actual reduction ratio Rr which fills Rh≦240 is established. Therefore, according to such a configuration, even if the maximum speed Mm of the electric motor 5 becomes low, the minimum response speed ω required for the phase adjusting mechanism 8 is fully assured. Besides, “CA” is the unit showing the rotation angle of the camshaft 2 in which the rotating speed serves as half of the crankshaft.

Rh=(Mm−Mss)/ω  (3)

Other Embodiments

The present invention is not limited to the embodiment mentioned above, and can be applied to various embodiments.

The energizing control circuit 6 stops the energization to the electric motor 5, when the crankshaft rotating speed exceeds the threshold value Nth and both other conditions are satisfied. Alternatively, when the crankshaft rotating speed exceeds the threshold value Nth and the other conditions are not satisfied, the adjustment of the control torque may be continued without deenergizing the electric motor 5. Moreover, the energizing control circuit 6 may utilizes the rotation speed of the camshaft 2 in place of or in addition to the crankshaft rotating speed in controlling the energization of the electric motor 5, especially the energization control on condition of the threshold value. In a case that the rotation speed of camshaft 2 is utilized to control the energization of the motor 5, the threshold value Nth is set as half value of the threshold of the crankshaft speed.

The rotor 10 may perform the interlocking rotation with the camshaft 2, and the rotor 20 may perform the interlocking rotation with the crankshaft. Moreover, when the motor 5 is deenergized, the rotational phase between the rotors 10 and 20 may be brought to the most advance phase. The phase adjusting mechanism 8 may be a structure in which the planet gear is engaged with the gear provided in one of the rotors.

At least one of the gears 14 and 22 and corresponding gears 52, 54 may be changed into the external gear and the internal gear, respectively. Moreover, the lubrication fluid supplied to the planetary mechanism part 60 can be other than a lubricant for the internal combustion engines.

The stopper structure which stops the rotor 20 to the rotor 10 may be another structure other than the combination of the slot 70 and the projected part 72.

And the present invention is applicable also to the apparatus which adjusts the valve timing of the exhaust valve, and the apparatus which adjusts the valve timing of the intake valve and the exhaust valve.

Claims

1. A valve timing controller adjusting a valve timing of an intake valve and/or an exhaust valve of an internal combustion engine, comprising:

an electric motor which rotates by energization;

an energizing control circuit which controls the energization of the electric motor; and

a phase adjusting mechanism including a first rotor which rotates along with one of a crankshaft and a camshaft of the internal combustion engine, and a second rotor which rotates along with the other, the phase adjusting mechanism adjusting a rotational phase between the first rotor and the second rotor according to the rotation of the electric motor, wherein

in a case that a rotating speed of the internal combustion engine exceeds a threshold value, the energizing control circuit stops the energization of the electric motor so that the phase adjusting mechanism varies the rotational phase to an end phase which is one of a most retard phase and a most advance phase.

2. A valve timing controller according to claim 1, wherein

the phase adjusting mechanism varies the rotational phase to the end phase which permits start up of the internal combustion engine when the energizing control circuit stops the energization of the electric motor.

3. A valve timing controller according to claim 1, wherein

in a case that the electric motor rotates in the same rotational phase as the first rotor, the phase adjusting mechanism rotates the second rotor in the same rotational phase as the first rotor, and

in a case that the electric motor rotates in a retard direction relative to the first rotor, the phase adjusting mechanism rotates the second rotor to the end phase relative to the first rotor.

4. A valve timing controller according to claim 3, further comprising:

a stopper means which stops the second rotor to the first rotor in the end phase.

5. A valve timing controller according to claim 3, wherein

the threshold value is established lower than the rotating speed of the internal combustion engine when assuming that the electric motor rotates in the same rotational phase as the first rotor and in a maximum speed.

6. A valve timing controller according to claim 5, wherein

in the phase adjusting mechanism which adjusts the rotational phase by reducing the rotation speed of the electric motor and converting the rotation of the electric motor into the rotation of the second rotor, an actual reduction ratio between the electric motor and the second rotor, and a minimum response speed of the rotation variation of the second rotor at the time of the rotational variation of the electric motor are established,

when the rotation speed of the electric motor changes from a rotation in which the electric motor rotates in the same rotational phase as the first rotor to a rotation in which the electric motor rotates in the maximum speed, the actual reduction ratio is less than a reduction ratio for the phase adjusting mechanism to reduce the rotation speed of the electric motor and to vary the rotation of the second rotor at the minimum response speed.

7. A valve timing controller according to claim 6, wherein

the actual reduction ratio is greater than a reduction ratio required for the phase adjusting mechanism to reduce the rotation speed of the electric motor and to rotate the second rotor against a transmitting torque from the internal combustion engine.

8. The valve timing controller according to claim 7, wherein

the phase adjusting mechanism includes a planet gear which engages with a gear provided at least one of the first rotor and the second rotor, and lubricant is supplied to an engagement part of the planet gear and the gear.