BRIEF DESCRIPTION OF THE DRAWINGS
Two embodiments of the invention are shown in the drawing and are described in more detail below in comparison with a previously known valve train. Shown in each of the Figures in a longitudinal section are:
FIG. 1 is a longitudinal cross-sectional view of a lash adjuster according to the invention in a first construction;
FIG. 2 is a longitudinal cross-sectional view of a lash adjuster according to the invention in a second construction;
FIG. 3 is a longitudinal cross-sectional view of a valve train installed in an internal combustion engine with a previously known lash adjuster;
FIG. 4 is a partial representation in a longitudinal cross-sectional view of the previously known lash adjuster enlarged relative to FIG. 3;
FIG. 5 and FIG. 6 are longitudinal cross-sectional views of the one-way valve of the lash adjuster shown in FIG. 3 and FIG. 4, respectively, in an enlarged representation.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The hydraulic lash adjuster 1 shown in FIGS. 3 and 4 according to the previously known state of the art is installed in a valve train 2 of an internal combustion engine 3, which can be actuated via tappet push rods 4. The adjuster 1 is constructed as a switchable cam follower and is comprised of an outer cylindrical section 5, which encloses in its interior 6 an inner cylindrical section 7. The section 7 can move axially relative to the outer section 5 and forms with this outer section a circular cylindrical housing.
The outer section 5 is closed with one end facing a cam 8 of a camshaft and by a base 9. In the area of the base 9 there is a roller 10, whose outer surface is used as a contact surface for the cam 8. The roller 10 is supported on a pin via a roller bearing. This pin is led in the area of the base 9 diametrically through the outer section 5 and fixed there with its end in the outer section 5 by stamping. With its end located outside of the outer section 5, the inner section 7 faces the tappet push rod 4, which here is supported with its end 12 on a dome-shaped bearing surface 11 of the inner section 7.
Hydraulic medium can be led to an outer end of a switching element 13 causing the switching process of the adjuster 1. For this purpose, a channel 14 is provided in the internal combustion engine 3. For achieving a large stroke of a gas-exchange valve 15 of the internal combustion engine 3, wherein said gas-exchange valve is connected to the adjuster 1 via a valve lifter 16 and the tappet push rod 4, the coupling of the outer section 5 to the inner section 7 of the element 1 is required. The switching element 13 is produced as a piston-like slide, which is held in the coupling position by a compression spring.
If it is desired to disconnect the gas-exchange valve 15, then hydraulic medium is led out of the channel 14 in front of the outer end of the switching element 13. If the adjuster 1 is located in its base-circle phase, in which the outer section 5 and the inner section 7 are not fixed relative to each other, then for sufficient pressure of the hydraulic means, the switching element 13 can be displaced radially completely into the inner section 7 against the force of its compression spring. In the subsequent cam stroke, the outer section 5 is then displaced relative to the inner section 7 against the force of a compression spring 17 arranged in the outer section 5. In this case, the tappet push rod 4 and the gas-exchange valve 15 are not displaced, because the force of the compression spring 17 of the outer section 5 is smaller than the counteracting force of a compression spring 20 of the gas-exchange valve 15.
As a hydraulic lash adjuster, the adjuster 1 requires the supply of oil as the hydraulic medium. For this purpose, a feed line 18 is arranged in the tappet push rod 4. Instead of this feed line, however, a feed line for hydraulic medium is also conceivable, which leads in the internal combustion engine 3 into the receptacle space 19 for the outer cylindrical section 5.
The inner cylindrical section 7 of the lash adjuster 1 is a rotationally symmetric housing part. It has a pocket hole, which forms a high-pressure chamber 21. A hollow cylindrical piston 22 is guided with seal lash in the housing part. This has a lower piston head and an upper piston head. Underneath the lower piston head is the high-pressure chamber 21. Above the lower piston head is a low-pressure chamber 23, which is formed by the interior of the piston 22 and which is used as an oil storage space.
The high-pressure chamber 21 is connected to the low-pressure chamber 23 via a central through-opening 24 (FIGS. 5 and 6), which is arranged in the lower piston head. It is part of a one-way valve 27 provided with a closing body 25 and a compression spring 26. This extends into the high-pressure chamber 21 underneath the lower piston head, wherein the through-opening 24 ends at a valve seat 28 of the piston 22 for a sealing contact on the closing body 25 in the closed state of the one-way valve 27. Another compression spring 29 is supported in the high-pressure chamber 21 at its base. It applies force to the piston 22 via a valve cap 30 surrounding the closing body 25 with its compression spring 26.
The lash adjusters according to the invention shown in FIGS. 1 and 2 differ from this previously known element by the modified construction of each one-way valve.
In FIG. 1, the one-way valve 31 has a mushroom-shaped closing body 32. This contacts the valve seat 28 of the piston 22 due to the effect of its compression spring 33 with an approximately spherical, convexly vaulted bearing surface 34 and therefore closes the through-opening 24 of the piston. The compression spring 33, which is arranged with the mushroom-shaped closing body 32 in a corresponding valve cap 35 contacting the piston 22 and which is supported on this cap with one end, surrounds the shaft of the closing body 32 coaxially over part of its length. It has a cylindrical, helical compression spring construction and is supported with its other end on the bottom side of the mushroom head of the closing body 32. In this way, the overall height h2 of the one-way valve 31 in FIG. 1 is less than the overall height h1 of the previously known one-way valve 27 in FIG. 5 by the difference h3.
In FIG. 2, the one-way valve 36 has a dome-shaped closing body 37, which contacts the valve seat 28 of the piston 22 due to the effect of its compression spring 38 with a similarly approximately spherical, convexly vaulted bearing surface 39 and therefore closes the through-opening 24 of the piston. The compression spring 38 is arranged together with the dome-shaped closing body 37 in a corresponding valve cap 40 contacting the piston 22. It is supported on this cap with one end and projects with a part of its length into the dome-shaped closing body 37, with which it is arranged coaxially. With its other end, the compression spring 38 is supported on the inside of the closing body 37 in the area of its vaulted bearing surface 39. In this way, the overall height h4 of the one-way valve 36 in FIG. 2 is less than the overall height h1 of the previously known one-way valve 27 in FIG. 6 by the difference h5.
The present solution was designed as one possible construction for the installation of a switchable tappet for a tappet push-rod motor, but can also be applied in the development of other lash adjusters.
LIST OF REFERENCE SYMBOLS
1 Lash adjuster
2 Valve train
3 Internal combustion engine
4 Tappet push rod
5 Outer cylindrical section
6 Interior
7 Inner cylindrical section
8 Cam
9 Base
10 Roller
11 Bearing surface
12 End of tappet push rod
13 Switching element
14 Channel
15 Gas-exchange valve
16 Valve lifter
17 Compression spring
18 Feed line
19 Receptacle space
20 Compression spring
21 High-pressure chamber
22 Piston
23 Low-pressure chamber
24 Through-opening
25 Closing body
26 Compression spring
27 One-way valve
28 Valve seat
29 Additional compression spring
30 Valve cap
31 One-way valve
32 Closing body
33 Compression spring
34 Bearing surface
35 Valve cap
36 One-way valve
37 Closing body
38 Compression spring
39 Bearing surface
40 Valve cap
- h1 Overall height
- h2 Overall height
- h3 Difference
- h4 Overall height
- h5 Difference
Patent Application
20070272185
