DE10113095A1 - Valve timing adjusting device for IC engines in motor vehicles has pivoted cams on camshaft and associated valves with pneumatic valve springs - Google Patents

Abstract

The device has gas exchange valves (16), each with a cam (12) on a camshaft (10), and with at least one cam being pivoted within limits. The spring of each valve associated with a pivoted cam, is formed as a pneumatic valve spring (18). The cams associate with individual intake valves are pivoted relative to the cam shaft. The timing of a valve is varied by internal pressure variations of the pneumatic valve spring, timing is also varied using the pivoted cam.

Description

The invention relates to a device for influencing the valve timing on a Internal combustion engine according to the preamble of claim 1 and a method for Operating this device according to claim 3.

When controlling charge exchange valves of an internal combustion engine, with rigid Cam on a camshaft the problem is known that the valve timing only allows a fixed phase relationship determined by the rigid cam arrangement, although the optimal phase relationship is variable depending on the speed. This leads to, that the valve control by the rigid cam arrangement a compromise for one represents a wide speed range from, for example, 800 to 8000 rpm. A customized one Valve timing for different load conditions is therefore not possible. It was therefore already proposed in DE 196 20 744 A1 to adapt the Valve control or the control times to different operating situations of the Internal combustion engine to form the cam with respect to the camshaft.

The invention has for its object a method and an apparatus Above type with regard to the variability of the control times for pivotable To improve cams.

This object is achieved by a device of the above. Kind of with the in Features characterized in claim 1 and by a method with the in claim 3 specified features solved. Advantageous embodiments of the invention are shown in the dependent claims.

In a device of the above. Art is provided according to the invention that the Valve spring of each valve associated with a pivotable cam as pneumatic valve spring is formed.  

This has the advantage that a change in the control time with respect to the valve opening time or Valve closing time of a valve assigned to a pivotable cam additionally can be varied by means of the pneumatic valve spring. It also results u. a. a reduced friction in the cylinder head, reduction of potential Starting noise and improved part-load behavior. Furthermore, a free one Cam design possible.

The respective intake valves are used to change the control times of the intake valves assigned cams pivotable with respect to the camshaft.

With the above The method according to the invention provides that Internal pressure variation of the pneumatic valve spring a control time of the corresponding Valve is varied.

This has the advantage that a change in the control time with respect to the valve opening time or Valve closing time of a valve assigned to a pivotable cam additionally can be varied by means of the pneumatic valve spring. It also results u. a. a reduced friction in the cylinder head, reduction of potential Starting noise and improved part-load behavior. Furthermore, a free one Cam design possible.

The control time of the corresponding valve expediently interacts varies with the respective assigned pivotable cam of the camshaft.

Further features, advantages and advantageous configurations of the invention result from the dependent claims, as well as from the following description of the Invention with reference to the accompanying drawings. This shows one in the single figure exemplary embodiment of a device according to the invention in sectional view.

The device shown in the single figure comprises a schematically illustrated camshaft 10 with cams, of which a cam 12 is shown, which acts on a tappet 14 of an inlet valve 16 . A pneumatic valve spring 18 applies force to the inlet valve 16 in the closing direction and ensures close contact between the tappet 14 and the cam 12 . The cam 12 is arranged on the camshaft 10 such that it can be pivoted to a limited extent with respect to the camshaft 10 . As a result, a control time of the valve 16 is changed as a function of the speed.

The pneumatic valve spring 18 comprises a pressure chamber 20 in which a corresponding pressure is built up to produce a spring characteristic. The characteristic of the valve spring is changed according to the invention by additional variation of this internal pressure in the pressure chamber 20 , as a result of which a corresponding influence on the pivoting of the cam 12 with respect to the camshaft 10 is possible. The control time of the valve 16 is thus additionally varied.

Different O-rings 22 provide corresponding sealing points, such as on a valve cone piece 24 . Possibly. the camshaft is additionally assigned an adjusting device which pivots the camshaft with respect to the crankshaft by a predetermined angle, so that corresponding valve timing can be shifted past "early" or "late" for an entire camshaft.

LIST OF REFERENCE NUMBERS

10

camshaft

12

cam

14

tappets

16

intake valve

18

pneumatic valve spring

20

pressure chamber

22

O-ring

24

Shuttle Pieces

Claims (4)

1. Device for influencing the valve timing on an internal combustion engine, in particular a motor vehicle, with at least one camshaft ( 10 ), which actuates gas exchange valves ( 16 ) periodically, is in driven connection with a crankshaft of the internal combustion engine, with each gas exchange valve ( 16 ) having a cam ( 12 ) on the camshaft ( 10 ), at least one cam ( 12 ) with respect to the camshaft ( 10 ) being arranged such that it can be pivoted to a limited extent, characterized in that a valve spring of each valve ( 12 ) assigned to a pivotable cam ( 12 ) 16 ) is designed as a pneumatic valve spring ( 18 ). 2. Apparatus according to claim 1, characterized in that the respective intake valves ( 16 ) associated cams ( 12 ) are pivotable with respect to the camshaft ( 10 ). 3. Method for operating a device for influencing the valve timing on an internal combustion engine, in particular a motor vehicle, with at least a camshaft, which actuates gas exchange valves periodically, in driven Connected to a crankshaft of the internal combustion engine, each Gas exchange valve is assigned a cam on the camshaft, furthermore At least one cam with respect to the camshaft can be pivoted to a limited extent is arranged and a valve spring of each a pivotable cam associated valve is designed as a pneumatic valve spring, whereby by Internal pressure variation of the pneumatic valve spring a timing of the corresponding valve is varied. 4. The method according to claim 3, characterized in that the control time of the corresponding valve in cooperation with the respectively assigned pivotable cam of the camshaft is varied.