EP0925427B1 - Automatic decompression system - Google Patents

Description

The present invention relates to automatic decompression for an internal combustion engine, in particular a single cylinder diesel engine, with at least one outlet and one inlet valve, the of a camshaft with at least one cam can be controlled, whereby to reduce the starting resistance the exhaust valve is vented when starting is and with other features according to the preamble of claim 1.

Devices are known from the prior art, which the starting resistance when intake of internal combustion engines to reduce. This is before all about semi-automatic devices that have a manually operated lever to the exhaust valve Ventilate a few tenths of a millimeter and after one Working game when reversing start or more Working games when starting the crank using a Reset or detent mechanism from decompression switch to compression. Furthermore, from the State of the art decompression devices known, which is controlled by a centrifugal force certain, short angular range around the ignition TDC only one valve (inlet or outlet valve) a few Raise tenths of a millimeter and from a certain one Crankshaft speed from decompressed to switch compressed state. It is also from the EP 0515183 A1 a further starting aid device known that works controlled by centrifugal force. Because of the rigid connection between centrifugal weight and The bracket becomes a relatively large one in this device Installation space required.

The object of the present invention is therefore a easy to manufacture, inexpensive automatic decompression to create by a purely mechanical Regulation works fully automatically and only requires little space.

This task is done by an automatic decompression solved with the features of claim 1. It is for venting the exhaust valve below a switching speed for switching from decompression to Compression a fully automatic lifting device provided which the lifting of the exhaust valve from Valve seat causes. The lifting device causes this way venting the valve as long as the Camshaft below a defined switching speed turns. This advantageously leads to Reduce the starting resistance during the Tempering, causing the engine to either by hand using a reversing rope or a crank or electrically by means of a small starter motor is started. The is above the switching speed Lifting device inactive, i.e. the valve will not ventilated and therefore full compression given. Furthermore, the invention provides that the Lifting device an articulated, arranged between cams and a control disc Bracket with two articulated arms and one connecting them Traverse has that at speeds below the switching speed an indented decompression position occupies in the cam plane at which he protrudes beyond the cam base circle, and after Reaching the switching speed in a neutral Position in the control disc level can be disengaged. The bracket is designed such that it around one in a parallel to the cam plane Axis of rotation is pivotable and in such a way that the Bracket with slowly rotating or at a standstill located camshaft with the across Articulated arms arranged traverse in the cam plane is indented and over the cam base circle protrudes. This space-saving arrangement will the valve as long as it is in the area by the cam the traverse is controlled from its closed Position slightly ventilated, i.e. lifted off the valve seat. After reaching the defined switching speed a restoring force is exerted on the articulated arms, which leads to a pivoting movement of the bracket, whereby the crossbeam in the control disc plane is disengaged. This makes it easy fully automatic with purely mechanical means Automatic decompression created just one has a small footprint in the assembly room. Furthermore The invention provides that for speed-dependent Control of the engagement and disengagement of the bracket for Decompression or compression by at least one a preload spring in a defined rest position held and pressurized in the radial direction Flyweight is provided. Here the mass of the flyweight is dimensioned so that it is at the defined switching speed extreme radial position against the pressure of the spring occupies, i.e. that in this position on one Stop is present. The preload spring also ensures for making the flyweight independent in its rest position of the gravitational forces in one defined position is held. When dimensioning the centrifugal mass depending on the Switching speed is the preload force of the spring consider. By coupling the flyweight mechanism with the articulated bracket is in simple way the switching speed dependent on and Disengagement of the bracket realized.

An advantageous embodiment of the Invention before that the inner radius of a flyweight as a ramp for engaging the bracket against the Resistance of a release spring is formed. At this design is the swivel of the bracket approximately at the level of the longitudinal axis of the camshaft arranged parallel to the cam plane. Here the articulated arms have one running to the traverse Lever arm and one from the joint into that of the traverse lever arm running in the opposite direction. The lever arm is loaded by the release spring, causing the bracket to be in its disengaged position is maintained provided the flyweight is above the Switching speed its extreme radial position occupies. At speeds below the switching speed lies the ramp-shaped area of the inner radius of the Centrifugal weight on the crossbar and causes the Bracket against the preload of the release spring in held in its indented position.

Another advantageous embodiment of the present Invention provides that the flyweight with the bracket via one arranged on the articulated arm Driver is coupled. In this embodiment is the driver designed as a lever with coupled to an arm of the flyweight. At The centrifugal weight increases when the switching speed is reached the driver so far with that the bracket to the outside in its disengaged position tilts and in the control disc plane is positioned. Below the switching speed the carrier arm keeps the bracket in siner indented position, in which the traverse is in the cam level.

Finally, it is advantageous that two arches Flyweights are provided by a hinge are coupled together. This will be more advantageous Way the influence of gravitational forces by tying up two opposing centrifugal weights eliminated. This makes it very possible to achieve low shift speeds, which in particular at the start of reversing is advantageous.

Furthermore sees an advantageous embodiment before that by appropriate arc length of the bracket ventilation in the decompression position in a defined crank angle range of approximately 90 ° he follows. This is the area that after closing the inlet valve and before reaching it the ignition OT or after the ignition OT and before opening of the exhaust valve is available. For reasons the valve clearance adjustment option must be in the ignition top dead center There is an area without valve lift.

It is also advantageous that the switching speed between 300 and 600 rpm, preferably at 400 rpm lies. By switching speed selected in this way even at extremely low temperatures Carry out a manual start or the engine with a underperforming starter.

Finally, see an advantageous embodiment before that the control cam has a groove for receiving the Has bracket in the engaged position. Hereby the bracket maintains its defined position and will protected from deformation.

Another advantageous development of the present Invention provides that the inlet valve over the same cam as the exhaust valve can be actuated and in the direction of rotation of the camshaft during the phase decompression after the exhaust valve in addition this is aired. The advantage is that in connection with reversing or kick start devices the starting resistance by the proportion of charge change work to be performed for the suction stroke is reduced. This also ensures that no unfiltered suction from the exhaust tract can be done.

Finally, it is advantageous that the closing of the Exhaust valve 40 ° before TDC and opening the Inlet valve 40 ° after ignition TDC is provided. This ensures that both valves are safe in the ignition top dead center closed.

Finally, another embodiment of the present invention that a valve rocker arm is provided between the cam and the valve. This can be the valve directly or via a push rod head for.

Finally, it is advantageous that the valve rocker arm due to the lifting device by 0.2 mm - 0.6 mm, preferably 0.4 mm can be raised. This If implemented accordingly, the Valves between 0.3 and 0.8 mm.

Fig. 1

eine Vorderansicht einer ersten Ausführungsform der erfindungsgemäßen Dekompressionsautomatik;

Fig. 2

eine geschnittene Seitenansicht der Dekompressionsautomatik nach Fig. 1;

Fig. 3

eine Vorderansicht der Dekompressionsautomatik nach Fig. 1, wobei das Einlaßventil gelüftet ist;

Fig. 4

eine Dekompressionsautomatik nach Fig. 1 nach Erreichen der Schaltdrehzahl;

Fig. 5

eine geschnittene Seitenansicht der Dekompressionsautomatik nach Fig. 1 nach Erreichen der Schaltdrehzahl;

Fig. 6a - 6c

verschiedene Ausführungsformen eines erfindungsgemäßen Bügels;

Fig. 7

eine weitere Ausführungsform der erfindungsgemäßen Dekompressionsautomatik in geschnittener Seitenansicht;

Fig. 8

ein Ventilsteuerschaubild mit Dekompression.

Advantageous embodiments of the present invention are explained in more detail below with reference to the attached figures. Show:

Fig. 1

a front view of a first embodiment of the automatic decompression according to the invention;

Fig. 2

a sectional side view of the automatic decompression system according to FIG. 1;

Fig. 3

a front view of the automatic decompression of Figure 1, wherein the inlet valve is vented.

Fig. 4

an automatic decompression according to Figure 1 after reaching the switching speed.

Fig. 5

a sectional side view of the automatic decompression according to Figure 1 after reaching the switching speed.

6a-6c

different embodiments of a bracket according to the invention;

Fig. 7

a further embodiment of the automatic decompression according to the invention in a sectional side view;

Fig. 8

a valve timing diagram with decompression.

Fig. 1 shows a front view of a first embodiment the automatic decompression according to the invention with arranged on the camshaft 20 Cam 1 and a control disc 2. In the control disc level are a first flyweight 3, which stored in a point 4 and by a spring 5 in radial direction is pressed inwards second flyweight 6 with another bearing point 7 and the common joint 8 and the driving arm 9 and the bracket 22 stored. The driver 10, the connected articulated arm 11, the second articulated arm 13 and the cross member 14 form the bracket 22. Die Tooth 15 of the control disc 2 and the cam base circle 19 are by a dash-dotted line indicated. Furthermore, are indicated by dash-dotted lines Lines of the rocker arms 16 for the exhaust valve and the rocker arm 17 shown for the inlet valve. In addition, the nose 18 of the first flyweight 3 and the nose 19 of the second flyweight 6 are shown, each at the bearing points 4 and 7 opposite ends of the arcuate flyweights are arranged.

The following are the same parts with the same Provide reference numerals.

Fig. 2 shows a sectional side view of the Automatic decompression system according to FIG. 1 the rocker arm 16 of the exhaust valve shown. This has a sliding surface 21, which rests on the cam 1 and depending on it Lifting movement opens or closes the exhaust valve. The bracket 22 with the cross member 14 and the articulated arm 11 and the driver 10 is in on both articulated arms a bearing 23 pivotable in the control disk 2 stored. Furthermore, the camshaft 20, the first centrifugal weight 3 and the second centrifugal weight 6 and the toothing 15 of the control disk 2 is shown.

1 and 2 describe a state of the automatic decompression at standstill or at speeds below the switching speed. In this state the first flyweight 3 by the spring 5 in pressed radially inward and the second Centrifugal weight 6 also via the articulated connection 8 held in the radius direction. This keeps the driving arm 9 the driver 11 in one of the Camshaft axis 24 remote position, whereby the cross member 14 of the bracket 22 in an indented State is in the camshaft plane. When a switching speed is reached, the centrifugal force is of the two flyweights 3 and 6 larger than that radially inward force of the spring 5, whereby the centrifugal weights are pushed radially outwards until the lugs 18 and 19 against the groove base 25 the control disc. In this state the driver 10 in one of the axes 24 of the camshaft approximate position moves, causing the bracket 22 in a neutral position in the control disc plane is disengaged. This state is in FIGS. 4 and 5 shown.

In the engaged state, the cross member 14 engages a groove 26 of the cam 1, whereby the crossbar 14 of the bracket 22 over the cam base circle N. protrudes a few tenths of a millimeter. Now turns the control disk of Fig. 1 clockwise further, the indented bracket first lifts the Rocker arm 17 of the intake valve by a few tenths of a millimeter where the effective crank angle range by the arc length of the bracket 22, i.e. through the Length of the cross member 14 is determined. That state is shown in Fig. 3. Opens when turning further the cam 1 first the exhaust valve, then that Inlet valve and lifts the outlet valve after the Closing again slightly thanks to the indented bracket on. The bracket is engaged and disengaged thereby, as already described, controlled by centrifugal force, only then indenting when re-engaging can take place when the bracket is not straight located at the level of a rocker arm.

6a to 6c show side views of different Embodiments of an inventive Bracket. In addition to the articulated arm 11 and Traverse 14 of the driver 10 and one as a joint serving cutting edge 23 shown. 6b shows one Bracket, in which the bearing by a ball 60th is formed. 6c finally shows the side view an embodiment of an inventive Bracket, in which the bearing is formed by an axis 61 becomes.

7 shows a further embodiment of a Automatic decompression according to the invention. This it differs from the one above described embodiment that the first flyweight 70 an inner radius designed as a ramp 71 has and secondly in that the Bracket 72 around one through the center line of the camshaft leading axis 73 is pivotable. The bracket 72 points next to the articulated arm 74 and the cross member 75 a lever arm 76 which by a spring 77 is charged. This will make the bracket above the Shifting speed disengaged and in this position held. The bracket is below the switching speed against the spring pressure of the spring 77 through the ramp 71 to its indented position in the cam plane pushed and held in this position until the The centrifugal weight moves outwards again.

8 shows a valve timing diagram of decompression, with 100 the valve lift curve of the exhaust valve, with 102 the valve lift curve of the intake valve, with 103 the valve lift through the automatic decompression on the inlet valve and at 104 the valve lift through the automatic decompression is shown on the outlet valve. At 105 the ignition TDC is designated and with 106 the overlap TDC. This becomes clearly recognizable Diagram that about 40 ° before TDC and 40 ° after Ignition TDC there is no lifting of the valve.

Claims (11)

1. Automatic decompression device for an internal combustion engine and in particular for a single cylinder Diesel engine with at least one outlet and one inlet valve, controlled by a camshaft (20) and at least one cam (1) which, to reduce the starting resistance during start-up, provides for the venting of the outlet valve, for which a fully automatic lifting means is provided to activate below a control speed providing a changeover from decompression to compression, which engages into the cams (1) of the outlet valve and which effects the lifting of the outlet valve from its valve seat, where the lifting means provides a pivotal clamp (22, 72) with two pivotal arms (11, 13; 74) and a cross beam (14; 75) connecting both arms, which is arranged between the cams (1) and a control plate (2); at speeds below the changeover value this clamp takes up a meshed decompression position at the cam level, where it protrudes beyond the cam base circle (N), characterised in that the clamp (22, 72) can be disengaged into a neutral position at the control plate level after reaching the changeover speed, and in that at least one centrifugal weight (3; 70), biased by a spring (5) in a radial direction to control the engagement/disengagement depending on the [engine] speed, is flexibly coupled to the clamp.
2. Automatic decompression device according to claim 1, characterised in that the internal radius of the centrifugal weight (70) is designed as ramp (71) for engaging the clamp (72) against the resistance of the disengagement spring (77).
3. Automatic decompression device according to claim 1, characterised in that the centrifugal weight (3) is coupled to the clamp (22) via a tab (10) arranged on a pivotal arm (11).
4. Automatic decompression device according to claim 1, characterised in that two bowed centrifugal weights (3, 6; 70; 78) are provided, which are connected to each other by means of a joint (8).
5. Automatic decompression device according to claim 1, characterised in that, by an appropriate length of the clamp arch (22; 72), venting occurs in the decompression position in a defined crank angle area of approx. 90°.
6. Automatic decompression device according to claim 1, characterised in that the changeover speed lies between 300 and 600 rpm and preferably at 400 rpm.
7. Automatic decompression device according to claim 1, characterised in that a groove is provided in the control cam (24) for engaging the clamp (22) in the engaged position.
8. Automatic decompression device according to claim 1, characterised in that the inlet valve may be activated above the same cams (1) as the outlet valve and is vented, additional and subsequent to the outlet valve, during the decompression phase in the direction of the revolution of the cam shaft (20).
9. Automatic decompression device according to claim 8, characterised in that the outlet valve is closed 40° before ignition TDC and the inlet valve is opened 40° past ignition TDC.
10. Automatic decompression device according to claim 1, characterised in that a valve draw lever (16; 17) is provided between cams (1) and valve.
11. Automatic decompression device according to claim 10, characterised in that the valve draw lever (16; 17) is able to be lifted by the means of disengagement by 0.2 to 0.6 mm and preferably by 0,4 mm.

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