1. Technical Field
The present invention relates to a variable valve timing device which changes a rotational phase of a camshaft relative to a crankshaft of an engine, for example, and changes opening and closing timing of an inlet valve and an exhaust valve.
2. Background Art
Recently, in an engine of a car, in order to prevent overlap of an inlet valve and an exhaust valve, enhance output, and realize low fuel consumption, there has been often employed an engine provided with a variable valve timing device which changes a rotational phase of a camshaft relative to a crankshaft of an engine and changes opening and closing timing of an inlet valve and an exhaust valve actuated by a cam of the camshaft.
For this type of conventional variable valve timing device, there has been proposed a variable valve timing device which is provided with an outer gear capable of transmitting a rotative power to a crankshaft of an engine, an inner gear transmitting the rotative power to a camshaft, a planet gear disposed between the outer gear and the inner gear and revolving around the inner gear while meshed with the outer gear and the inner gear, and a motor which is a drive source changing a revolution speed of the planet gear (for example, see Patent Literature 1).
When the variable valve timing device is actually used, the planet gear revolves around the inner gear while meshed with the outer gear and the inner gear, the rotative power of the outer gear is transmitted to the inner gear, and, at the same time, the revolution speed of the planet gear is changed using a motor, whereby the rotational phase of the inner gear relative to the outer gear is changed, and the rotational phase of the camshaft relative to a crankshaft is changed.
Patent Literature 1: Japanese Patent Application
Laid-Open No. 2008-267174
However, although the conventional variable valve timing device has an advantage that the revolution speed of the planet gear is changed by the motor to easily change the rotational phase of the inner gear relative to the outer gear, energization control means of the motor as a drive source, rotation detection means and the like are required in order to suitably change the rotational phase of the inner gear relative to the outer gear, whereby the device structure is naturally complicated, and, at the same time, cost may be increased.
The present invention was developed to effectively solve the problem with the conventional variable valve timing device. A variable valve timing device according to the present invention changes a rotational phase of a camshaft relative to a crankshaft of an engine and changes opening and closing timing of at least one of an inlet valve and an exhaust valve actuated by a cam of the camshaft, a first motion gear to which a rotative power is transmitted from a crankshaft and a second motion gear which transmits the rotative power to the camshaft are independently rotatably arranged on a first shaft, a first variable gear meshed with the first motion gear and a second variable gear meshed with the second motion gear are integrally rotatably arranged on a second shaft spaced apart from and in parallel with the first shaft, setting is performed so that the number of teeth of the first variable gear and the number of teeth of the second variable gear are different from each other, a gear case which holds the second shaft and rotates the second shaft around the first shaft is provided, rotation control means which controls continuous rotation of the gear case is provided, the rotation control means is constituted of a sliced veneer provided on a side surface of the gear case, an arm whose front end is mutually rotatably connected to the sliced veneer, and an eccentric disc supporting rotatably a base end of the arm and rotating in synchronization with the crankshaft, the second shaft is rotated by the gear case to shift positions of the first and second variable gears, and, thus, to change the rotational phase of the second motion gear relative to the first motion gear and change the rotational phase of the camshaft relative to the crankshaft, and, at the same time, a base end of an arm is displaced by rotation of an eccentric disc of the rotation control means to continuously rotate the gear case in a clockwise direction or a counter clockwise direction, and, thus, to continuously change the rotational phase of the camshaft relative to the crankshaft.
Thus, according to the present invention, in a process that a rotative power is transmitted from a first motion gear, to which the rotative power is transmitted from a crankshaft, to a second motion gear which transmits the rotative power to a camshaft, first and second variable gears with different number of teeth as so-called different gears are integrally rotatably interposed, and the positions of the first and second variable gears are just shifted by a gear case, whereby the rotational phase of the second motion gear relative to the first motion gear can be easily changed. Thus, simplification of the device structure and cost reduction can be realized because the device does not require complex control means, and, at the same time, the rotational phase of the camshaft relative to the crankshaft can be reliably changed, so that a reliable change of the valve opening and closing timing can be secured.
Further, since the positions of the first and second variable gears are easily shifted just by rotating the gear case to allow the rotational phase of the camshaft relative to the crankshaft to be changed, when the gear case is continuously rotated, the rotational phase can be continuously changed, so that not only the valve opening and closing timing but also valve opening and closing times can be changed.
The present invention provides a variable valve timing device which changes a rotational phase of a camshaft relative to a crankshaft of an engine and changes opening and closing timing of at least one of an inlet valve and an exhaust valve actuated by a cam of the camshaft. In the variable valve timing device, a first motion gear to which a rotative power is transmitted from a crankshaft and a second motion gear which transmits the rotative power to the camshaft are independently rotatably arranged on a first shaft, and a first variable gear meshed with the first motion gear and a second variable gear meshed with the second motion gear are integrally rotatably arranged on a second shaft spaced apart from and in parallel with the first shaft. The variable valve timing device is further provided with adjustment means which holds the second shaft and rotates the second shaft around the first shaft, and setting is performed so that the number of teeth of the first variable gear and the number of teeth of the second variable gear are different from each other. The second shaft is rotated by the adjustment means to shift the positions of the first and second variable gears, whereby the device does not require complex control means in relation to changing the rotational phase of the second motion gear relative to the first motion gear and changing the rotational phase of the camshaft relative to the crankshaft. Therefore, simplification of the device structure and cost reduction can be realized, and, at the same time, the rotational phase of the camshaft relative to the crankshaft can be reliably changed.
Hereinafter, a variable valve timing device according to a first embodiment will be described in detail in accordance with the preferred embodiments illustrating the present invention. As shown in
In this embodiment, a timing pulley 9b on the camshaft 12 side and the first motion gear 3 are integrally formed. When the rotative power of a crankshaft 11 is transmitted from a timing pulley 9a on the crankshaft 11 side to the timing pulley 9b through a timing belt 10, the rotative power is also transmitted to the first motion gear 3.
In the present invention, it is especially important to perform setting so that the number of teeth of the first variable gear 6 and the number of teeth of the second variable gear 7 are different from each other. In this embodiment, the diameter of the first variable gear 6 is smaller than the diameter of the second variable gear 7, and setting is performed so that the number of the teeth of the first variable gear 6 is smaller than the number of the teeth of the second variable gear 7. Accordingly, the diameter of the first motion gear 3 is larger than the diameter of the second motion gear 4 in relation to that a distance between the first shaft 2 and the second shaft 5 is constant.
In this embodiment, although the first variable gear 6 and the second variable gear 7 are integrally formed in order to allow both the gears 6 and 7 to be rotated integrally with each other, the present invention is not limited thereto, and both the gears 6 and 7 maybe formed separately to have connection means, and, thus, to be connected integrally with each other depending on implementation.
Accordingly, in the variable valve timing device 1, when the gear case 8 is located at a fixed reference position θ1 in
Subsequently, the rotative power is transmitted to the first variable gear 6 meshed with the first motion gear 3 and the second variable gear 7 integrally provide with the first variable gear 6 to be then transmitted to the second motion gear 4 meshed with the second variable gear 7, and, thus, to be finally transmitted to the camshaft 12 through the first shaft 2 fixed with the second motion gear 4.
A rotation ratio between the crankshaft 11 and the camshaft 12 will be now described. The camshaft 12 opens and closes inlet valves (exhaust valves) 13 and 14 by means of a cam 12a or 12b of the camshaft 12. Usually, in a four-cycle engine, since the camshaft 12 rotates once while the crankshaft 11 rotates twice, the rotation ratio between the crankshaft 11 and the camshaft 12 is 2:1. Accordingly, each number of the teeth of the first motion gear 3 and the second motion gear 4 is set so that the above rotation ratio is obtained, based on the assumption that the first variable gear 6 and the second variable gear 7 are different from each other in the number of teeth.
Next, a case where the gear case 8 is rotated around the first shaft 2 will be described. When the gear case 8 is rotated by Lθ around the first shaft 2 in a counter clockwise direction in
Accordingly, the rotational phase of the camshaft 12 is advanced, and a phase of valve operation of the inlet valves (exhaust valves) 13 and 14 actuated by the cam 12a or 12b of the cam shaft 12 is also advanced, so that, as shown in
On the other hand, when the gear case 8 is rotated by Rθ around the first shaft 2 in a clockwise direction in
Accordingly, the rotational phase of the camshaft 12 is delayed, and the phase of the valve operation of the inlet valves (exhaust valves) 13 and 14 actuated by the cam 12a or 12b of the camshaft 12 is also delayed, so that, as shown in
According to the above constitution, the rotational phase of the camshaft can be advanced or delayed according to the rotating direction of the gear case 8, and the amount of changing the rotational phase of the camshaft can be adjusted according to the rotation amount of the gear case 8. However, as shown in
In this embodiment, the diameter of the first variable gear 6 is smaller than the diameter of the second variable gear 7, and setting is performed so that the number of the teeth of the first variable gear 6 is smaller than the number of the teeth of the second variable gear 7. Accompanying this, although the diameter of the first motion gear 3 is larger than the diameter of the second motion gear 4, the present invention is not limited thereto, and the opposite configuration may be employed. Namely, the diameter of the first variable gear 6 is larger than the diameter of the second variable gear 7, and setting is performed so that the number of the teeth of the first variable gear 6 is larger than the number of the teeth of the second variable gear 7. Accompanying this, the diameter of the first motion gear 3 may be smaller than the diameter of the second motion gear 4 depending on implementation. In this case, unlike this embodiment, when the gear case 8 is rotated in the counter clockwise direction in
As described above, according to the present invention, in the process of transmitting the rotative power from the first motion gear 3, to which the rotative power is transmitted from the crankshaft 11, to the second motion gear 4 which transmits the rotative power to the camshaft 12, the first and second variable gears 6 and 7 with different number of teeth as so-called different gears are integrally rotatably interposed, and the device does not require complex control means in relation to just shifting the positions of the first and second variable gears 6 and 7 by the gear case 8 to easily change the rotational phase of the second motion gear 4 relative to the first motion gear 3. Therefore, simplification of the device structure and cost reduction can be realized, and, at the same time, the rotational phase of the camshaft 12 relative to the crankshaft 11 can be reliably changed. Consequently, the opening and closing timing of the inlet valves (exhaust valves) 13 and 14 is reliably changed, and it is possible to prevent overlap of an inlet valve and an exhaust valve, enhance output and realize low fuel consumption of an engine.
Further, the positions of the first and the second variable gears 6 and 7 are easily shifted just by rotating the gear case 8, and the rotational phase of the camshaft 12 relative to the crankshaft 11 can be changed; therefore, when the gear case 8 is continuously rotated, the rotational phase can be continuously changed, so that not only the opening and closing timing of the inlet valves (exhaust valves) 13 and 14 but also the opening and closing times can be changed as the following description with reference to
An example of means that controls the rotation of the gear case 8 of the variable valve timing device 1 according to this embodiment will be described according to
Further,
Furthermore,
Furthermore,
Accordingly, in the above rotation control means, the gear case 8 can be rotated continuously, and if the support position of the base end of the arm 23 when the gear case 8 is located at the fixed reference position θ1 can be adjusted to each position shown in
For example, when the support position of the base end of the arm 23 is adjusted to a position P2 when the gear case 8 is located at the fixed reference position θ1, as shown in
Thus, the phase of the valve operation in the above case changes as shown in a P2 graph of
Accordingly, in this example, since not only the valve opening and closing timing but also the valve operation time can be changed, it is particularly effective when the valve opening and closing times are required to be adjusted.
A variable valve timing device 1 in a second embodiment is different from that in the first embodiment and is attached to the crankshaft 11 side. As shown in
As in the first embodiment, the diameter of the first variable gear 6 is smaller than the diameter of the second variable gear 7, and setting is performed so that the number of teeth of the first variable gear 6 is smaller than the number of teeth of the second variable gear 7. Accordingly, as in the first embodiment, the diameter of the first motion gear 3 is larger than the diameter of the second motion gear 4.
In this embodiment, a crank gear 28 rotating with the crankshaft 11 is provided on the crankshaft 11 side. The crank gear 28 and the first motion gear 3 are meshed with each other to transmit the rotative power of the crankshaft 11 to the first motion gear 3. Meanwhile, the second motion gear 4 and a timing pulley 9a are integrally formed, and the timing pulley 9a rotates simultaneously with the rotation of the second motion gear 4 to transmit the rotative power to the camshaft 12 through the timing belt 10 and the timing pulley 9b on the camshaft 12 side.
Accordingly, the configuration in which the rotative power is transmitted from the crankshaft 11 to the first motion gear 3 and the configuration in which the rotative power is transmitted from the second motion gear 4 to the camshaft 12 are different from those in the first embodiment in relation to changing the attachment position of the variable valve timing device 1 from the camshaft 12 side to the crankshaft 11 side.
Since the operations and effects of the variable valve timing device 1 itself are similar to those of the first embodiment, descriptions of the operations and effects will be omitted here. In this example, it is particularly effective when an attachment space of the variable valve timing device 1 cannot be defined around the camshaft 12 side.
A variable valve timing device according to the present invention can realize simplification of a device structure and cost reduction in relation to that the device does not require complex control means. At the same time, the rotational phase of a camshaft relative to a crankshaft is reliably and continuously changed, and not only the valve opening and closing timing but also the valve opening and closing times can be changed. Therefore, the variable valve timing device is extremely advantageous when utilized in an engine of a car which attempts to enhance output and realize low fuel consumption.
Number | Date | Country | Kind |
---|---|---|---|
2009 277676 | Dec 2009 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/JP2010/070395 | 11/16/2010 | WO | 00 | 5/10/2012 |