EP2523780B1 - Hammer drill and/or impact hammer having cooling of equipment components - Google Patents

Description

The invention relates to a hammer drill and / or impact hammer with an internal combustion engine.

Hammer drills and / or percussion hammers with internal combustion engines - hereinafter also referred to briefly as hammers - are known in particular as relatively heavy breakers with which work is carried out essentially vertically downwards. In gasoline hammers of this type, a cooling air blower driven via the crankshaft of the internal combustion engine is provided for cooling the engine. The cooling air fan generates a cooling air flow which is guided along the outside of the cylinder of the internal combustion engine, in particular along the cooling fins provided on the outside of the cylinder. The engine cooling exhaust air discharged from the engine is usually very hot and must therefore be led away from the hammer in the shortest possible way.

The striking mechanism, which is provided for generating the working movement of the hammer and is driven by the internal combustion engine, can also heat up considerably, in particular if it is an air spring hammer mechanism, due to the air compression. To cool the striking mechanism, it is therefore known to provide an additional fan wheel, which generates a separate cooling air flow for the striking mechanism. Corresponding installation space must be provided for this additional fan wheel and design effort must be carried out.

From the DE 866 633 C a rock drilling machine is known in which a cooling air flow is generated by a cooling air blower. The cooling air flow is guided over ribs on the outer wall of an engine cylinder and subsequently emerges on the underside of the hood forming the cooling air channel.

In the GB 632,560 A. a hammer with a cooling air blower is shown, which generates a cooling air flow. The cooling air flow is led through a cladding to the outer wall of the cylinder of an internal combustion engine, the cross section of the cooling air channel tapering in the direction of flow.

The invention has for its object to provide a hammer drill and / or percussion hammer, in which an improved cooling of the components is possible.

The object is achieved by a hammer drill and / or percussion hammer according to claim 1.

Advantageous refinements are specified in the dependent claims.

A hammer drill and / or percussion hammer has an internal combustion engine with a cylinder and a piston movable in the cylinder, a cooling air blower for generating a cooling air flow and a cooling air duct for guiding the cooling air flow from the cooling air blower to an outer wall of the cylinder.

It is thereby achieved that the hammer mechanism driven by the internal combustion engine of the hammer is cooled. Downstream from the outer wall of the cylinder, the cooling air duct has a duct region in which a plurality of partial cooling air flows are branched off from the cooling air flow (main cooling air flow).

The channel area is designed such that the cross section of the channel area related to a flow direction of the cooling air flow tapers to the extent that partial cooling air flows are branched off from the cooling air flow, so that the flow rate of the cooling air flow in the channel area remains essentially constant.

While the cooling air duct is to define the entire length of the cooling air flow from the cooling air blower to the outlet from the hammer, the duct region only indicates a partial region of the cooling air duct. However, the channel area is of particular importance for the following consideration.

The cooling air duct in the area in which the cylinder or the outer wall of the cylinder is to be cooled is thus designed in such a way that the flow rate of the cooling air flow (main cooling air flow) remains constant even when partial cooling air flows have already been branched off. In the prior art, on the other hand, the cross section of the duct area is kept essentially constant, so that the flow rate of the cooling air is gradually reduced when partial cooling air flows are branched off. However, due to the fact that the flow velocity and thus the volume flow of cooling air become lower in the course of the cooling air duct, a relatively strong cooling air flow must be generated on the input side by the cooling air blower in the prior art, in order to still have enough cooling air available at the end of the cooling air duct after branching off several partial cooling air flows.

With the help of the invention it is thus possible to optimize the flow in the area of the hot cylinder by narrowing the cooling air duct upstream of the cylinder, so that z. B. in the area which is further away from the spark plug provided on the cylinder and is therefore cooler, a lot of cooling air flows past. A separate bypass, which would have a similar effect, can therefore be saved. This leads to less heating of the engine cooling exhaust air and to a lower flow resistance.

The engine cooling air can be blown through the engine with a comparatively lower flow resistance. This increases the volume flow and thus reduces the temperature of the cooling air. The engine only emits the amount of heat it needs to the cooling air, which also means that the cooling air does not heat up as much. In contrast, the prior art usually strives for a cooling air distribution in which as much heat as possible is extracted from the engine, but this is often not necessary.

A plurality of cooling fins running parallel to one another can be formed on the outer wall of the cylinder, a partial channel being formed in each case between two mutually adjacent cooling fins for guiding a partial cooling air flow, the partial cooling air flow being branched off from the cooling air flow brought up by the cooling air blower. The cooling fins are provided on the outer wall of the cylinder in a known manner and are usually cast in one piece with the cylinder housing or subsequently attached as cooling elements on the outer wall of the cylinder. One of the subchannels into which a respective partial cooling air flow is introduced is formed between the adjacent cooling fins. The respective partial cooling air flows are gradually branched off from the main cooling air flow when the main cooling air flow passes the cooling fins of the cylinder becomes.

In particular, the channel area can be guided upstream of the cooling fins past the cooling fins and thus past the subchannels or the initial areas of the subchannels. The duct area can be designed in such a way that the cross section of the duct area tapers in its course along the initial areas of the respective subchannels to the extent that partial cooling air flows are branched off from the cooling air flow, so that the above requirement is met that the flow velocity of the cooling air flow in the channel area remains essentially constant.

The flow rates of the partial cooling air flows in the sub-channels can be essentially the same. In particular, they can also be the same as the flow rate of the remaining cooling air flow in the duct area. In this way, an equalization and optimization of the cooling air flow is achieved with the lowest possible flow resistance. An indication of an unnecessary flow resistance would be e.g. a strong change in the flow velocity in the cooling air duct.

According to the invention, a cooling air duct is provided for guiding the cooling air flow from the cooling air blower along an outer wall of the cylinder, the cooling air duct having a duct section downstream of the outer wall of the cylinder for guiding the cooling air flow to an exhaust system of the internal combustion engine and / or to the striking mechanism.

This ensures that the cooling air, which has already warmed up as it flows past the cylinder, can continue to be used to cool other hot components whose temperature during operation is above the temperature that the Has cooling air flow downstream of the cylinder. These components include in particular the exhaust system of the internal combustion engine or the striking mechanism.

In this solution, the engine cooling exhaust air is thus used to further components of the hammer, namely in particular the exhaust system, for. B. the silencer, and to cool the hammer mechanism. The exhaust system and the striking mechanism in particular are subject to high thermal loads during operation of the hammer. On the one hand, their waste heat can be problematic for the components themselves. On the other hand, the waste heat can also lead to excessive heating of other components of the hammer, e.g. B. lead the carburetor or the tank system, which can impair reliable operation.

It has been found that the cooling air (engine cooling exhaust air) coming from the engine, that is to say from the outer wall of the cylinder, is still relatively cool and can therefore be used to cool the other components. Thus e.g. in a variant of this engine cooling exhaust air flow divided downstream of the outer wall of the cylinder and supplied in the form of two separate cooling air flows to the exhaust system and the hammer mechanism.

By cleverly designing the cooling air duct, it is thus possible to conduct a cooling air flow suitable for the respective device. Thus, e.g. the cooling air flow either only to the exhaust system or only to the striking mechanism or to both assemblies. It is also possible to control the cooling air flow e.g. first lead to the striking mechanism and then downstream of the striking mechanism to the exhaust system. Conversely, the cooling air flow can also be directed first to the exhaust system and then to the striking mechanism. The cooling air flow can also be divided into two parallel cooling air flows, which flow parallel to the exhaust system and the striking mechanism.

Mixed forms are also possible, for example the cooling air flow downstream of the outer wall of the cylinder is divided into two cooling air flows, one cooling air flow being led directly to the exhaust system and a second cooling air flow first to the striking mechanism and only then to the exhaust system.

The exact design of the cooling air duct and thus the routing of the cooling air flow depends on the temperature distributions in the hammer and on the desired cooling effect.

According to the invention, the cooling air duct has a first duct section downstream of the outer wall of the cylinder, for guiding the cooling air flow to the striking mechanism. Downstream of the striking mechanism, the cooling air duct has a second duct section for guiding the cooling air flow to the exhaust system. In this way, the cooling air flow is first routed to the striking mechanism and then to the exhaust system.

In a further embodiment, the cooling air duct is divided downstream from the outer wall of the cylinder into a first cooling air duct for a first cooling air flow and into a second cooling air duct for a second cooling air flow. The first cooling air duct serves to guide the first cooling air flow to an exhaust system of the internal combustion engine, while the second cooling air duct serves to guide the second cooling air flow to the striking mechanism.

The hammer mechanism can be an air spring hammer mechanism and a guide housing and one of the internal combustion engine in the guide housing z. B. oscillating and linearly movable drive piston, the second cooling air duct for guiding the second cooling air flow to an outside of the guide housing. The first duct section can also be designed accordingly in order to guide the cooling air flow to the outside of the guide housing. The heat in the striking mechanism arises especially in the vicinity of the air compression area inside the striking mechanism if the striking mechanism is an air spring hammer mechanism known per se. This heat is emitted to the outside via the guide housing and can be dissipated by the cooling air flow. Since the temperature generated in the hammer mechanism is higher than the temperature of the engine cooling exhaust air, the engine cooling exhaust air can still be used effectively to cool the hammer mechanism.

In a variant, the second cooling air duct can be designed such that the second cooling air flow can also be conducted downstream of the impact mechanism to the exhaust system of the internal combustion engine. It has been found that the cooling air, even if it has already cooled the engine (cylinder) and the hammer mechanism, is still at a temperature which is lower than the exhaust system of the internal combustion engine, in particular lower than the temperature of the muffler belonging to the exhaust system . For this reason, it may be advantageous to use the cooling air after cooling the striking mechanism to support the cooling of the muffler in order to improve the cooling effect.

The variants described above can be combined with one another as desired. It is thus possible to independently implement the division of the cooling air flow into a first cooling air flow and a second cooling air flow downstream from the outer wall of the cylinder. It is also possible to design the cooling air duct in the duct region located upstream from the outer wall of the cylinder in the manner described, so that the flow rate of the cooling air flow in this duct region remains essentially constant. However, the two variants can also be combined with one another in order to achieve particularly effective cooling.

Fig. 1

einen Hammer in rechter Seitenansicht;

Fig. 2

den Hammer von Fig. 1 in linker Seitenansicht;

Fig. 3

eine Schnittdarstellung des Hammers; und

Fig. 4

eine perspektivische Untersicht des Hammers.

These and further advantages and features of the invention are explained in more detail below using an example with the aid of the accompanying figures. Show it:

Fig. 1

a hammer in right side view;

Fig. 2

the hammer of Fig. 1 in left side view;

Fig. 3

a sectional view of the hammer; and

Fig. 4

a perspective bottom view of the hammer.

The Figures 1 to 4 show in different representations a schematic example of a hammer drill and / or percussion hammer according to the invention.

The hammer has an internal combustion engine 1 which drives a striking mechanism 5 via a first crank mechanism 2, a transmission 3 and a second crank mechanism 4. The striking mechanism 5 in turn acts on a tool 6, in the present example a chisel. The construction of such a hammer is widely known and therefore does not need to be explained in detail.

The internal combustion engine 1 has a cylinder 7, inside which a piston 8 is movably guided. The piston 8 drives the first crank mechanism 2 via a connecting rod 9.

The transmission 3 and thus the second crank mechanism 4 are moved via a crankshaft 10 of the crank mechanism 2.

The striking mechanism 5 is designed as an air spring hammer mechanism and has a connecting rod 11 moved by the second crank mechanism 4, which moves a drive piston 12 back and forth in a guide housing 13 belonging to the striking mechanism.

In the interior of the drive piston 12, a percussion piston 14 is guided, which is moved towards the end of the tool 6 and is returned via an air spring 15 formed between the drive piston 12 and the percussion piston 14. The function of such a striking mechanism 5 is also known and does not need to be discussed in greater detail at this point.

At the front end of the crankshaft 10, a cooling air blower 16 with a fan wheel 17, a blower housing 18 and a cooling air inlet 19 is arranged. The fan wheel 17 is driven in rotation by the crankshaft 10 and thereby sucks ambient air via the cooling air inlet 19. The cooling air is then led via a cooling air duct 20 to the components of the hammer to be cooled.

In particular, the cooling air duct 20 leads the cooling air to an outer wall of the cylinder 7, on which numerous cooling fins 21 are arranged in a known manner. In Figure 3 For reasons of clarity, only two of the cooling fins 21 are identified by the reference number 21. Of course, the outer wall of the cylinder 7 has a plurality of cooling fins 21, as well as directly Figure 3 seen.

Between the cooling fins 21, respective sub-channels 22 are formed, in which the air flow from the cooling air channel 20 can be guided past the outer wall of the cylinder 7. Each of these sub-channels 22 thus branches off a partial cooling air flow from the main cooling air flow in the channel region of the cooling air channel 20 located upstream from the cylinder 7.

As in Figure 3 Recognizable, the cooling air flow in the cooling air duct 20 flows from above, ie coming from the cooling air blower 16 in the downward direction, partial cooling air flows being branched off gradually via respective sub-ducts 22 in the duct region mentioned and being guided past the outer wall of the cylinder 7. The cooling air duct 20 tapers to the extent that cooling air is branched off from it into the respective sub-duct 22. The cross section of the cooling air duct 20 is to be reduced in such a way that the flow rate of the cooling air flow in the cooling air duct 20 provided upstream from the cylinder 7 remains constant. In Figure 3 this taper is recognizable by an obliquely extending channel cover 23.

The cross-sectional tapering of the cooling air duct in Figure 4 can be seen where the channel cover 23 begins at a channel inlet 24 - based on an operating position of the hammer with the working direction directed vertically downward - both in the vertical direction downward and in the horizontal direction, away from the channel inlet 24 and thus runs obliquely Cooling air duct 20 tapers. The channel inlet 24 is in Figure 4 only shown in broken lines, since it is of course not visible from the outside under the channel cover 23.

The cooling air flow thus effected in the cooling air duct 20 and in the various sub-ducts 22 largely has a constant, identical speed, which is positive for an optimized engine cooling.

The cooling air can be released to the environment downstream of the internal combustion engine 1, that is to say downstream of the outer wall of the cylinder 7.

In a particularly advantageous embodiment of the invention, however, as is also shown in the figures, the cooling air coming from the engine is still used to cool components which are heated during operation of the hammer. In particular, the cooling air duct 20 is divided into a first cooling air duct 26 and a second cooling air duct 27 at an outlet 25, at which the cooling air is guided away from the cooling fins 21 and the outer wall of the cylinder 7. The division takes place with the aid of baffles 28 and 29. The baffles 28, 29 can be suitably shaped in space in order to guide the respective cooling air flows to the areas to be cooled.

A first cooling air flow is led into the first cooling air duct 26 and is led to an exhaust system 30 of the internal combustion engine 1, in particular to a silencer.

The exhaust system 30 with the muffler becomes particularly hot when the hammer is in operation, so that the cooling air coming from the engine, although already heated, can still contribute to cooling the exhaust system 30. This also ensures in particular that the exhaust system 30 does not in turn other components of the hammer, such as. B. the fuel supply, the tank or the carburetor can heat up in an impermissible manner when the hammer is used for a long time.

The second cooling air duct 27 leads the second cooling air flow as cooling air to the striking mechanism 5, in particular to the outer wall of the guide housing 13 of the striking mechanism 5 and there to an area of the striking mechanism 5 in which the air spring 15 is compressed. The compression of the air spring 15 causes a strong heating in the striking mechanism 5. This heat can be dissipated by the second cooling air flow introduced in the second cooling air duct 27.

In addition, with a suitable design of the hammer, it is also possible, after flowing past the striking mechanism 5, to also feed the second cooling air stream to the exhaust system 30, so that the second cooling air stream, which was heated by the striking mechanism 5 only relatively slightly, also also for cooling the hot muffler can be used in the exhaust system 30.

By optimizing the engine air cooling by equalizing the flow velocity as described above, it is possible to lower the temperature of the engine cooling exhaust air to such an extent that it can be used to cool other components of the hammer.

Through targeted guidance and distribution of the engine cooling exhaust air, it can be achieved that it is only led into areas whose temperature is so high that it can still be cooled despite the already relatively warm engine cooling exhaust air. For example, an 80 ° C engine cooling exhaust air can still cool down the 300 ° C hot silencer without any problems.

As a result of the fact that the engine cooling exhaust air is passed directly past the further hot heat sources of the hammer and has a cooling effect there, areas on the hammer whose temperature is below the engine cooling exhaust air are also indirectly cooled. This is achieved in that less heat is conducted into surrounding components or components by cooling near the heat source, so that these also remain cooler.

As described in detail in the introduction to the description, it is also possible to design the cooling air duct in such a way that the cooling air, after flowing past the cylinder 7, is first led to the outer wall of the guide housing 13 and subsequently along the exhaust system 30. Likewise, the cooling air can also be directed exclusively to the exhaust system 30.

Claims (10)

1. Hammer drill and/or percussion hammer, having

   - a combustion engine (1), having a cylinder (7) and a piston (8) which is movable in the cylinder (7);

   - a percussion mechanism (5) which is driven by the combustion engine (3);

   - a cooling air fan (16) for generating a cooling air flow; and having

   - a cooling air duct (20) for conducting the cooling air flow from the cooling air fan (16) along an outer wall of the cylinder (7);

   characterised in that

   - the percussion mechanism (5) is driven by the combustion engine via a transmission (3);

   - the cooling air duct (20) has a first duct section downstream of the outer wall of the cylinder (7) for conducting the cooling air flow to the percussion mechanism (5).
2. Hammer drill and/or percussion hammer as claimed in claim 1, characterised in that

   - the cooling air duct (20) has a second duct section downstream of the percussion mechanism (5) for conducting the cooling air flow to an exhaust system (30) of the combustion engine (1).
3. Hammer drill and/or percussion hammer as claimed in claim 1 or 2, characterised in that

   - the cooling air duct (20) is divided downstream of the outer wall of the cylinder (7) into a first cooling air duct (26) for a first cooling air flow and into a second cooling air duct (27) for a second cooling air flow;

   - the first cooling air duct (26) is used for conducting the first cooling air flow to the exhaust system (30) of the combustion engine (1); and in that

   - the second cooling air duct (27) is used to conduct the second cooling air flow to the percussion mechanism (5).
4. Hammer drill and/or percussion hammer as claimed in claim 3, characterised in that

   - the percussion mechanism (5) has a guide housing (13) and a drive piston (12) which can be moved by the combustion engine (1) in the guide housing (13); and in that

   - the second cooling air duct (27) is used to conduct the second cooling air flow to an outer side of the guide housing (13).
5. Hammer drill and/or percussion hammer as claimed in claim 3 or 4, characterised in that the second cooling air duct (27) is designed such that the second cooling air flow downstream of the percussion mechanism (5) can be conducted to the exhaust system (30) of the combustion engine (1).
6. Hammer drill and/or percussion hammer as claimed in any one of claims 1 to 5, wherein

   - upstream of the outer wall of the cylinder (7), the cooling air duct (20) has a duct region, in which a plurality of partial cooling air flows are diverted from the cooling air flow; and wherein

   - the duct region is configured such that the cross-section of the duct region relative to a flow direction of the cooling air flow is tapered to the extent that partial cooling air flows are diverted from the cooling air flow and so the flow rate of the cooling air flow in the duct region remains substantially constant.
7. Hammer drill and/or percussion hammer as claimed in claim 6, characterised in that

   - a plurality of cooling ribs (21) running in parallel with one another are formed on the outer wall of the cylinder (7); and in that

   - a partial duct (22) is formed between in each case two cooling ribs (21) which are adjacent to one another, in order to conduct a partial cooling air flow, wherein the partial cooling air flow is diverted from the cooling air flow introduced by the cooling air fan (16).
8. Hammer drill and/or percussion hammer as claimed in claim 6 or 7, characterised in that the duct region passes the cooling ribs (21) and thus the partial ducts (22) upstream of the cooling ribs (21) and is configured such that the cross-section of the duct region is tapered in its course along the initial regions of the respective partial ducts to such an extent that partial cooling air flows are diverted from the cooling air flow, so that the flow rate of the cooling air flow in the duct region remains substantially constant.
9. Hammer drill and/or percussion hammer as claimed in any one of claims 6 to 8, characterised in that the flow rate of the partial cooling air flows in the partial ducts (22) are substantially identical.
10. Hammer drill and/or percussion hammer as claimed in any one of claims 6 to 9, characterised in that the cooling air fan (16) is driven by means of a crankshaft (10) of the combustion engine (1).

Images