EP0620361B1 - Internal combustion engine with overhead camshaft and vertical crankshaft - Google Patents

Description

The invention relates to an internal combustion engine with a vertical crankshaft in a normal position of the engine, at least one overhead camshaft and a transmission between the crankshaft and the at least one camshaft with a plane of movement perpendicular to the crankshaft axis within a transmission space.

For precise control of the valve opening times, even with small drive motors, e.g. used for lawn mowers, overhead camshafts, i.e. Camshafts that are rotatably mounted in the cylinder head for direct or indirect actuation of the hanging intake and exhaust valves. A transmission between the camshaft and crankshaft provides the required drive energy and at the same time ensures the necessary synchronization of the camshaft rotation with the crankshaft rotation. In some areas of application of internal combustion engines, the working shaft to be driven by the engine generally has a vertical orientation. An example of this is the sickle lawnmower. However, the vertical orientation is not always maintained, depending on the inclination of the surface, there is a corresponding inclination of the working wave. With regard to the simplest possible construction and high efficiency by avoiding frictional losses, a direct coupling of the crankshaft of the drive motor to the working shaft is of great advantage, at most with the interposition of a simple spur gear. The crankshaft then also assumes a vertical orientation or, depending on the inclination of the subsurface, also an orientation that is more or less inclined to the vertical.

In such an arrangement, the at least one “overhead” camshaft extends laterally and axially parallel with respect to the camshaft axis. In order to ensure reliable running, especially at high operating temperatures and high speeds, constant lubrication of the camshaft must be ensured.

From DE 40 15 610 A1 an internal combustion engine of the type mentioned is known, in which an oil pump in the area of the lower bearing point of the crankshaft for forced lubrication both of the particularly loaded crankshaft connecting rod bearing and the upper bearing point of the bearings located in the cylinder head, i.e. at the top Camshaft ensures. For this purpose, the oil pump is connected to a through-channel of the crankshaft, which both has an outlet hole to the connecting rod bearing and also merges into cooling channels of a hollow flywheel flanged to the crankshaft in the region of the upper crankshaft end. The cooling channels in turn open into a cooling channel running parallel to the cylinder axis within the hollow cylinder wall surrounding the piston. This cooling channel has both an exit point 38 (FIG. 4) which opens into the crankshaft space, and thus also an exit point 63 to the upper camshaft bearing. The oil emerging from this bearing can flow down the camshaft to lubricate both the cam surfaces and the transmission between the camshaft and crankshaft, which is formed by a belt drive. The lower camshaft bearing can also receive sufficient lubricating oil. The lubricating oil flowing back is collected in a separate, apparently lower-lying oil collecting container 20 and fed to the oil pump again.

The forced lubrication of this internal combustion engine requires a great deal of design.

From EP-0 487 960 A1 an engine with an overhead camshaft and a vertically oriented crankshaft is known, in which the one formed by a belt transmission Transmission is at the upper end of the crankshaft and camshaft. Forced lubrication is provided for the upper crankshaft bearing and the upper camshaft bearing. Oil dripping from the upper camshaft bearing lubricates both the cam surfaces and the lower camshaft bearing, from where it flows back to an oil supply annular space surrounding the crankshaft and receiving the oil pump. The transmission itself does not come into contact with the lubricating oil. Finally, an internal combustion engine for a lawnmower is known from US Pat. No. 5,000,126, in which a camshaft that is mounted above and not in the crankshaft space is used.

The invention has for its object to provide an internal combustion engine of the type mentioned, which ensures reliable lubrication of the camshaft in the operating conditions occurring with a simple structure.

This object is achieved in that the transmission space is designed as an oil storage space in such a way that in the normal position and possibly in the inclined position of the engine, the lowest section of the transmission is immersed in the oil level.

The transmission thus serves as a delivery device for the lubricating oil, which always delivers the lubricating oil away from the current oil level and thus ensures a uniform distribution of the oil both in the area of the camshaft and in the area of the crankshaft. If, for example, the engine is currently inclined in such a way that the crankshaft space is lower than the camshaft space, the transmission dips into the oil level with its end on the crankshaft side, with the result that the transmission takes oil from there and conveys it into the camshaft area. Conversely, if the camshaft space is lower, oil is transferred from the transmission to the crankshaft space.

This oil distribution function of the transmission is also effective, for example, when the internal combustion engine is suddenly stopped or suddenly accelerated, so that the supply oil is currently jammed at the corresponding end of the oil storage space due to corresponding mass forces. A lack of oil at the other end of the oil reservoir is therefore ruled out by the transmission.

Common transmissions, e.g. Helical gearbox, in question. According to the invention, a transmission which is formed by an endless chain which runs via a gearwheel connected to the camshaft and a gearwheel connected to the crankshaft is particularly preferred on account of the simple structure and high oil output. This chain can be a roller chain or a tooth chain.

The transmission can equally well be formed by an endless belt, preferably a toothed belt, which runs over a belt pulley connected to the camshaft and over a belt pulley connected with the crankshaft. The toothed belt is characterized by its low weight and quiet running with good running precision. Both when using the chain and when using the belt, the inventive design of the transmission space as an oil reservoir promotes quiet running, since the oil bath for the chain or the belt contributes to significantly increased smoothness.

In order to ensure reliable lubrication of the corresponding parts without further measures, it is provided that in the region of the crankshaft-side end and / or the camshaft-side end of the transmission at least one impact surface for oil thrown away from the transmission is provided for the production of spray oil or oil mist. The spray oil or the oil mist easily gets to more distant lubrication points.

In order to further improve the lubrication of bearing points, it is proposed that at least one oil channel be provided in the area of a bearing point of the crankshaft or camshaft for guiding deposited oil mist or spray oil to the respective bearing point.

In many cases, especially in the case of low-stress engines or engines which are particularly cost-effective to produce, lubrication of the crankshaft by the spray oil or oil mist generated by the transmission is sufficient. In other cases, in particular in engines for professional use, the use of an oil pump is proposed, the inlet of which is connected to the oil reservoir and the outlet of which is connected to a crankshaft connecting rod bearing. In this way, reliable lubrication of the most heavily loaded bearing point is ensured.

It is proposed here that the outlet of the oil pump is connected to a through-channel of the crankshaft with an outlet hole on the connecting rod bearing. The through-channel can end at the connecting rod bearing, since the camshaft is lubricated independently of this due to the promotional effect of the transmission.

Many designs are conceivable for the oil pump, but it is preferably provided that the oil pump is a rubber vane cell pump driven by the crankshaft.

In a further development of the invention, it is proposed that part of the oil reservoir is an annular space surrounding the crankshaft. The annular space can be produced inexpensively, since only a housing part to be attached to the crankcase needs to be modified accordingly.

In the case of the use of an oil pump, it is proposed that the inlet of the oil pump via a feed line with the Annular space is connected, which opens into the annular space in the area of the annular space floor. It can be provided that the supply line opens into the annular space on the side of the crankshaft axis diametrically opposite the camshaft. This position of the supply line ensures that the oil pump continues to be supplied with oil even in larger inclined positions of the engine. The arrangement of the feed line on the side of the crankshaft axis facing away from the camshaft is intended for those cases in which a strong engine inclination in the sense of a higher-lying camshaft is permissible, but not a strong inclination in the opposite direction. For example, in lawnmowers, the camshaft is usually in front in relation to the direction of travel and, if the slope is steep, the lawnmower is allowed to go uphill, but not downhill. The specified position of the oil pump intake opening ensures reliable bearing lubrication with compressed oil for driving uphill with a steep slope.

In order to prevent the oil pump from running dry even with extreme engine tendencies, it is proposed that the annular space be provided with a cover arranged below the transmission. When the engine is tilted appropriately, the cover prevents the oil from flowing out of the annular space to such an extent that the intake opening of the oil pump reaches outside the oil level.

In order to ensure that sufficient oil always flows back into the annular space during operation, it is proposed that the cover be provided with at least one oil passage opening.

In order to ensure a sufficient oil level in which the transmission is at least partially immersed. It is proposed that the at least one oil passage opening protrude upwards Circumferential band is provided. The circumferential collar ensures that an oil pool with a depth corresponding to the circumferential collar height is formed on the cover.

For the sake of simplicity, it can be provided that the cover has a central opening through which the crankshaft passes.

In order to reliably ensure sufficient residual oil volume in the annular space in the case of the admissibility of a strong inclination only in the direction of a higher-lying camshaft, it is proposed that at least one oil passage opening be arranged on the side of the crankshaft axis facing the at least one camshaft.

Inexpensive producibility is ensured in that the cover is formed by a cover plate.

To increase the effective oil supply, a recess underneath the camshaft can be proposed.

It is particularly preferred to use the internal combustion engine described above in a lawn mower, although other types of application are also possible.

Fig. 1

einen vereinfachten Vertikalschnitt längs der Zylinderachse eines erfindungsgemäß ausgebildeten Brennkraftmotors;

Fig. 2

eine weiter vereinfachte vertikale Schnittansicht einer Version des Brennkraftmotors gemäß Fig. 1 ohne Ölpumpe, wobei einige Ölpegel bei unterschiedlichen Neigungen des Motors angedeutet sind;

Fig. 3

einen Vertikalschnitt im Bereich der Kurbelwelle der Brennkraftmaschine gemäß Fig. 1 mit Ölpumpe; und

Fig. 4

eine Draufsicht auf die Transmission der Brennkraftmaschine gemäß Fig. 1 und 3 (Schnittlinie IV-IV in den Figuren 1 und 3).

The invention is explained below using a preferred embodiment with reference to the drawing. It shows:

Fig. 1

a simplified vertical section along the cylinder axis of an internal combustion engine designed according to the invention;

Fig. 2

a further simplified vertical sectional view of a version of the internal combustion engine according to Figure 1 without an oil pump, some oil levels are indicated at different inclinations of the engine.

Fig. 3

a vertical section in the region of the crankshaft of the internal combustion engine according to FIG. 1 with an oil pump; and

Fig. 4

a plan view of the transmission of the internal combustion engine according to FIGS. 1 and 3 (section line IV-IV in Figures 1 and 3).

Small, light, single-cylinder 4-stroke engines, like these e.g. for driving lawn mowers and similar devices have recently been fitted with a valve control with overhead, i.e. Camshaft mounted in the cylinder head, which actuates the intake and exhaust valves.

Such a structure can be found in the basic drawing according to FIG. 1. The internal combustion engine designated 10 thus has a crankshaft 12, the crankshaft axis 14 of which is oriented vertically in a normal position of the engine. A camshaft 16 with an axis 18 parallel to the crankshaft axis 14 is rotatably mounted on a cylinder head 20 for the direct actuation of the hanging valves 22, in the example shown via bucket tappets 24, each of which engages around a valve spring 26.

For the general structure of the internal combustion engine 10, it should also be added that the crankshaft 12 is connected via a connecting rod 28 and a piston pin 30 to a cylinder 32 which is mounted in a cylinder crankcase 34 such that it can be moved back and forth. The engine 10 shown is air-cooled, for which purpose corresponding cooling fins 34a and 20a are provided on the cylinder crankcase 34 and on the cylinder head 20 are. However, the oil lubrication system to be described in more detail below can also be used with liquid-filled engines.

1 of the internal combustion engine 10 are a cable pull starter 36 and a magneto ignition device 37. The cable pull starter 36 has the usual structure. It comprises a pull rope 36a, which is wound onto a rope sheave 36b, with the inner rope end fixed to this sheave. The outer end of the rope carries a handle, not shown. A rope tension spring 36c pretensions the rope pulley 36b in the sense of keeping the rope 36a wound up. Via a freewheel, not shown, the pulley 36b is coupled to a magnet wheel 38, which in turn is connected in a rotationally fixed manner (nut 39) to the upper end of the crankshaft 12.

The pole wheel 38 is formed with cooling fins 38a. Furthermore, the magnet wheel 38 carries at least one permanent magnet 38b as part of the magnetic ignition device 37. Each time the permanent magnet 38b passes an excitation unit 40 shown on the left of the magnet wheel 38 in FIG. 1, the required ignition voltage for the spark plug, not shown, is generated in the latter. Anchor plates 40a can be seen which increase the induction effect.

1, a conventional centrifugal governor 42 is also indicated, which acts on a throttle valve (not shown) for speed control. A carrier part 42a for centrifugal weights 42b is provided with a circumferential toothing. This engages in a gearwheel 42c, which is attached in a rotationally fixed manner to a lower shaft journal 12b of the crankshaft 12 between a lower crank web 12a of the crankshaft 12 and a lower crankshaft bearing 44. The centrifugal weights 42b serve to axially adjust an actuator 42d, which is in turn connected to the throttle valve by means not shown.

The pull starter 36 is covered on the outside by a cover cap 46. A further cover cap 48 covers the magneto ignition device 37 together with the magnet wheel 38. A cylinder head cover 50 covers the camshaft 16.

The lower crankshaft bearing 44 together with the centrifugal governor 42 are located in a separate housing part 52 which is attached to the cylinder crankcase 34. The housing part 52 also houses an annular space 54 as part of the oil lubrication system still to be described and, in one version of the engine, an oil pump 56 in the form of a vane pump. An upper crankshaft bearing 57, however, is inserted directly into the cylinder crankcase 34.

The camshaft 16 is driven synchronously with the crankshaft rotation via a transmission 60, which at the same time takes over the function of the lubricating oil distribution in order to ensure sufficient lubrication of the engine 10. In the exemplary embodiment shown, the transmission 60 is formed by an endless chain 62 (roller chain or toothed chain), which runs both via a gearwheel 64 attached to the lower end of the camshaft 16 and via a gearwheel 66 attached to the shaft journal 12b of the crankshaft 12 (see FIG. also top view according to FIG. 4). The chain 62 can be tensioned by a tensioning device, not shown, depending on the type of engine. With a simple motor design, this may also be omitted. The gearwheel 66 can form a common component with the gearwheel 42c mentioned above in the form of a gearwheel sleeve 67 pushed onto the shaft journal 12b and connected to it in a rotationally fixed manner. Instead of the chain 62, an endless belt, in particular a toothed belt, can also be used, which then runs over corresponding pulleys of the camshaft and the crankshaft.

In order to always obtain adequate engine lubrication both with an exactly vertical crankshaft axis 14 and in an inclined position of the engine, the transmission space 70 receiving the transmission 60 within the engine 10 is simultaneously designed as an oil reservoir. The chain 62 (or the belt in the case of a belt drive) is then immersed in the oil supply both in the normal position with an exactly vertical crankshaft axis 14 and in corresponding inclined positions, with the result that the chain conveys the oil away from the oil supply, i.e. in an area that currently has no standing oil.

Fig. 2 is intended to illustrate this. One can see with a solid line an oil level 62a with an exact vertical (= perpendicular) orientation of the crankshaft axis 14. The level 62a lies approximately such that the chain 60 and the gear wheels 64 and 66 are at least partially immersed in the lubricating oil. If the motor 10 is inclined, for example, by driving the lawn mower using the motor 10 up a slope, the oil level 62b is obtained, for example, with a slight inclination, provided that the usual design with the cylinder of the internal combustion engine pointing forward in the direction of travel is used.

2 that the rear gear 66 on the right in FIG. 2 is now fully immersed in the lubricating oil. The chain 60 accordingly conveys lubricating oil to the front (arrow A) to the front gear 64. There, the oil is thrown radially outward with respect to the axis 18 due to the centrifugal force generated when the chain 62 is deflected around the gear 64. This creates oil splashes and oil mist. This splash or the oil mist spreads in the interior 50a of the cylinder head cover 50 (arrows B in FIGS. 1 and 4) with the result that both an upper and a lower pivot bearing 68a or 68b of the camshaft on the cylinder head have sufficient lubricating oil be supplied, as well as to the Cup tappets 26 adjoining cam surfaces 16a and 16b of the camshaft 16. The cup tappets 26 themselves, if necessary, also receive sufficient lubricating oil within their respective guide bores in the cylinder head 20.

If, on the other hand, the motor is tilted in the opposite direction (driving downhill), e.g. an oil level 62c indicated with a dash-dot-dot line in FIG. 2. Now the front gear 64 is immersed in the lubricating oil. The chain 62 consequently conveys lubricating oil into the crankshaft space with its chain center 62a "returning to the gear 66 (arrow C in FIG. 4). The consequence in turn is that in the region of the deflection of the chain 62 around the gear 66 oil splashes are thrown radially outwards 4. The resulting oil splashes and oil mist ensure lubrication of both the crankshaft bearings 44 and 57 and generally a connecting rod bearing 72 between the connecting rod 28 and the crank pin 12c of the crankshaft 12.

The oil-producing effect of the transmission 60, which ensures the lubrication, from the current lubricating oil pool to regions remote from the pool is also present when the motor is inclined to the side, ie an inclination about a horizontal pivot axis 74 which is contained in one of the two axes 14 or 18 Level lies. An oil level 62d is indicated in FIG. 4, which would result with a corresponding lateral inclination of the motor 10 (looking parallel to the axes 14 and 16). It can be seen that at least the front gear 64 is immersed in the oil, so that there is a conveying effect in the direction C, with oil splashes thrown in the direction of the arrows D and B when the chain rotates around the rear gear 66 and the front gear 64. Die Oil splashes or the oil mist ensures sufficient lubrication of all bearings.

A certain oil supply is necessary so that according to the invention the transmission 10 always runs partially through the standing lubricating oil even in the inclined positions mentioned. To accommodate this, the already mentioned annular space 54 is provided, which surrounds the shaft journal 12b. In addition, a recess 76 can be provided in the region of the front gear 64 to form a corresponding oil pocket for storage oil. The correspondingly large oil supply ensures, even with relatively extreme inclinations, that the transmission 60 is always partially immersed in the oil supply. In FIG. 2, an oil level 62e is indicated by a dash-dot line, which is then assumed when the engine assumes the limit slope of 35 ° (travel uphill). The rear gear 66 is still immersed in the oil reservoir. The limit angle for downhill travel, on the other hand, may be lower, because for safety reasons, downhill travel with a large incline is not permitted (risk of accident for the operator).

The constant, at least partial immersion of the transmission in the oil reservoir also has the advantage of reducing running noise.

The oil supply is dimensioned such that when the engine is inclined about the horizontal axis 74 in question by more than 90 °, the oil level 62d remains below the valves 22 and bucket tappets 24, so that hot and low-viscosity oil penetrates through the valve guides and the inlet valve in the combustion chamber or in the exhaust duct and the silencer is avoided from the outset. Such a lateral motor inclination is necessary, for example, if the knife area is to be cleaned after use of the lawnmower or if maintenance or repair work on the cutting tool (sickle knife) is to be carried out.

The oil pump 56 already mentioned can be used for highly loaded engines. As FIG. 3 shows, the pump 56 receives oil from the annular space 54 via a feed line 56a. Since the motor should be particularly suitable for extreme rearward inclination (pivoting the motor about a horizontal axis in the clockwise direction of FIGS. 1 and 3) , the mouth 56b of the channel 56a lies on the side of the crankshaft axis 14 which is diametrically opposite the camshaft 16.

The oil pump 56 is connected to a through channel 80 of the crankshaft 12 via a radial branch line 80a. The through channel 80 in turn ends at the connecting rod bearing 72 to form an outlet hole 80b. The bearing that is most heavily loaded during operation, namely the connecting rod bearing 72, is consequently lubricated. The remaining bearings are still lubricated with the aid of the delivery effect of the transmission 60.

In order to reliably ensure in the possible inclination positions of the engine that the forced lubrication of the connecting rod bearing is maintained via the oil pump 56, the annular space 54 is provided with a cover 84 in the embodiment with an oil pump. In order to maintain the oil circuit running via the oil pump 56, the cover 84 does not completely close off the annular space 54, but instead has oil passage openings which are adjusted to the oil delivery capacity of the oil pump 56. In many cases, it is sufficient to dimension a central opening 84a of the cover 84 through which the crankshaft 12 extends, so that there is a clear distance between the cover 84 and the crankshaft 12 (or sleeve 67 with the gearwheels 42c and 66).

Additional openings may be required. 3 and 4 is one Oil passage opening 86 indicated. This lies on the side of the crankshaft axis 14 facing the camshaft 18. The reason for this is again that in the case of the strong inclined position to be taken into account in the first place with an inclined cylinder (limit angle 35 ° see FIG. 3) the mouth in any case 56b of the feed line 56a is below the oil level. This oil level adjusts itself to the level 62e according to FIGS. 2 and 3 at least initially. In the case of a smaller oil supply quantity than in FIG. 2, a level 62e ′ indicated in FIG. 3 is set after some time, which is defined by the lowest point of the central opening 84a. In any case, the opening 56b of the supply line 56a always remains in the lubricating oil bath.

In order to always ensure a minimum height of the oil level even when the cover 84 is used (oil level 62a ′ with vertical crankshaft axis 14), the oil passage openings (central opening 84a and opening 86) can each be provided with an upwardly projecting circumferential collar 88, which acts as a kind of " Overflow ". Depending on the inclination of the engine, the chain 62 always pumps oil from the oil pool formed on the cover into the areas of the engine which are more distant therefrom. No other moving parts are required for this type of lubrication, so that reliable operation with an inexpensive construction is ensured.

The small, light, single-cylinder four-stroke engine described above is suitable for driving implements, in particular a lawnmower. Other operating modes with changing inclinations are also possible.

Claims (19)

1. Internal combustion engine (10) with a crankshaft (12) which is vertical in the normal position of the engine, as least one overhead camshaft (16) and a transmission (60) between crankshaft (12) and the at least one camshaft (16) with plane of movement within a transmission cavity (70) perpendicular to the axis (14) of the crankshaft
   characterised in that
   the transmission cavity (70) is formed as an oil sump in such a way that in the normal position as well as in possible tilted positions of the engine the currently lowermost portion of the transmission (60) dips into the oil.
2. Engine according to claim 1,
   characterised in that
   the transmission 60 is formed by an endless chain (62) which passes over a sprocket (64) connected to the camshaft (16) and a sprocket (66) connected to the crankshaft (12).
3. Engine according to claim 1,
   characterised in that
   the transmission is formed by an endless belt, preferably a toothed belt, which passes over a pulley connected to the camshaft and a pulley connected to the crankshaft.
4. Engine according to one of the foregoing claims,
   characterised in that
   there is provided in the region of the crankshaft end and/or the camshaft end of the transmission (60) at least one impact surface for oil flung from the transmission (60) to generate oil sprays or an oil mist.
5. Engine according to claim 4,
   characterised in that
   at least one oil channel is provided in the neighbourhood of the bearing of the crankshaft (12) and/or of the camshaft (16) for conducting precipitated oil mist of oil spray to the bearing in question.
6. Engine according to one of the foregoing claims,
   characterised by
   an oil pump (56) of which the inlet is connected to the oil sump and the outlet is connected to a big end bearing (72).
7. Engine according to claim 6,
   characterised in that
   the outlet from the oil pump (56) is connected to a passage (80) in the crankshaft (12) having its outlet opening (80b) at the big end bearing (72).
8. Engine according to claim 6 or 7,
   characterised in that
   the oil pump (56) is a rubber vane pump driven from the crankshaft (12).
9. Engine according to one of the foregoing claim,
   characterised in that
   part of the oil sump is an annular space (54) around the crankshaft (12).
10. Engine according to one of claims 6 to 9,
    characterised in that
    the inlet to the oil pump (56) is connected to the annular space (54) through a feed pipe (56a) which opens into the annular space (54) in the region of the bottom of the space.
11. Engine according to claim 10,
    characterised in that
    the feed pipe (56a) opens into the annular space (54) on that side of the axis (14) of the crankshaft which lies diametrically opposite the camshaft (16).
12. Engine according to one of claims 9 to 11,
    characterised in that
    the annular space (54) is provided with a cover (84) arranged underneath the transmission (60).
13. Engine according to claim 12,
    characterised in that
    the cover (84) is provided with at least one opening (86) for oil .
14. Engine according to claim 13,
    characterised in that
    the at least one opening (86) for oil is provided with an upwardly projecting peripheral collar (88).
15. Engine according to claim 13 or 14,
    characterised in that
    the cover has a central opening (84a) through which the crankshaft (12) passes.
16. Engine according to one of claims 13 to 15,
    characterised by
    at least one opening (86) for oil on the side of the axis (14) of the crankshaft which is towards the at least one camshaft (16).
17. Engine according to one of claims 12 to 16,
    characterised in that
    the cover (84) is formed by a sheet metal pressing.
18. Engine according to one of the foregoing claims,
    characterised in that
    part of the oil sump is a recess (76) underneath the camshaft (16).
19. The use of an engine according to one of the foregoing claims in a lawnmower.

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