Patent Application
20090211549
This Invention relates to cam phase adjusters used for adjusting the angular relative position of the camshaft in relation to the crankshaft and, more particularly, to vane-type camshaft phasers having a stator and a rotor.
Vane-type phasers are conventional devices used especially in motor vehicles in order to adjust the angular position of a camshaft in relation to the crankshaft of the internal combustion engine. The device uses a stator and a rotor to adjust the angular position of the camshaft in relation to the crankshaft. The stator rotates on the camshaft and is rotated by a belt or chain from the crankshaft. The rotor is fixed to the camshaft. The stator has a plurality of pressure chambers, each of which are divided by the vanes of the rotor. By applying a pressure medium, typically oil, into the pressure chamber on either side of the rotor vane, the angular relationship between the stator and the rotor is changed and, hence, the relative angular position between the crankshaft and the camshaft is adjusted.
Typically, a return spring, such as a flat spiral spring, is used to return the rotor to an initial rest position when the engine is turned off. One of the problems is that when the overall camshaft drag torque is high, a single return spring is not adequate or is too slow. In certain cases, hydraulic pressure is used to assist the return spring, however, hydraulic pressure can detract from the efficiency of the engine.
It is the object of the present Invention to provide a spring design which provides an adequate level of return spring compensation for a phaser so as to have consistently balanced shifting speeds in the advanced and retard timing directions. It is also the object of the present Invention to provide a reliable unlocking of the locking mechanism of the phaser in locked position. It is furthermore, the object of the present Invention to accomplish high return spring torques in a set area of space.
These and other objects of the present Invention will be more readily understood by reference to the following description of the Invention.
The present Invention obtains these objects by an improved spring design in which a plurality of return springs is used. Furthermore, robustness and durability of the phaser is also improved by employing a plurality of return springs in the phaser. The overall working stress on each of the individual return springs can be lowered because of the plurality of return springs and therefore increase the factor of safety for the return springs as a whole.
More specifically, a plurality of return springs is assembled in parallel in the camshaft phaser. The plurality of parallel return springs provide a high return spring compensation when the overall camshaft drag torque is at levels which are too high to be compensated for by a single spring. The total summation of torque from the plurality of return springs is suitably higher than the overall camshaft drag torque.
Broadly, the present Invention can be defined as a camshaft phaser adjuster comprising:
a stator and a rotor adjustable to the stator in a circumferential direction by a pressure medium;
at least one spring chamber proximately located adjacent to the stator and the rotor; and
a plurality of return springs proximately arranged in the spring chamber, each of the springs having a rotor connecting end for connecting to the rotor and a stator connecting end for connecting to the stator, the return springs configured to rotate the rotor relative to the stator into an initial position absent pressure from the pressure medium.
In the preferred embodiment, the spring chamber is axially adjacent to the stator and rotor and the plurality of return springs are arranged axially adjacent to one another in the spring camber. Multiple spring cambers and other spring arrangements such as co-axial return springs will occur to those skilled in the art and are within the scope of the present invention.
Preferably, the number of return springs is two or more; and, more preferably, the number of return springs is two to four.
Suitably, the return springs are flat spiral springs. Each of the springs preferably has equal strength, however, equal strength springs are not required. There could be a scenario where different strengths are used. IE. 3 Nm+5 Nm=8 Nm or 4 Nm×2=8 Nm.
One of the unique aspects of the present Invention is the fact that each of the return springs is identical in both strength and size. This leads to a balance of the torque and a cost savings and simplicity because of only one type of spring component part is used for several different outputs for different assemblies.
In order to allow for the use of a plurality of return springs, the support(s) for the springs are increased in length and the spring chamber, which is defined by the spring outer housing, is increased or deepened to accommodate the side-by-side axial arrangement of the return springs.
When the phaser of the present Invention is assembled, all return springs are wound simultaneously in the same manner as a single return spring is wound. The multiple return springs supply adequate torque to counteract the high camshaft drag torque of the engine. This yields balanced shifting speeds and excellent phaser unlocking behavior. Balanced shifting velocities and excellent unlocking behavior is just one of the unique advantages of the present Invention.
These and other aspects of the present Invention may be more readily understood by reference to one or more of the following drawings which are herein presented for purposes of illustration only.
Rotor 22 is fixed to camshaft 23 as shown in
Spring chamber 30 is defined by trigger wheel 31 which acts as an outer housing and locking cover 16. Drive screws 11 fixes housing 31 to rotor 22.
Arranged adjacent to one another in spring chamber 30 are spiral springs 34 and 36. Each spiral springs 34 and 36 has a rotor connecting end 38 and 40, respectively, and a stator connecting end 42 and 44, respectively. Each of the spring ends is, in turn, connected to a respective rotor stop 46, 48 and a stator stop 50, 52.
An alternate embodiment is illustrated in
A further alternate embodiment is illustrated in
| Number | Date | Country | |
|---|---|---|---|
| 61030303 | Feb 2008 | US |
