GB2503979A

GB2503979A - Device for providing clean combustion air for an internal combustion engine of a working tool

Info

Publication number: GB2503979A
Application number: GB1308359.7A
Authority: GB
Inventors: Joerg Achenbach
Original assignee: Makita Corp
Current assignee: Makita Corp
Priority date: 2012-05-15
Filing date: 2013-05-09
Publication date: 2014-01-15
Also published as: GB201308359D0; CN103422963A; DE202012101780U1; US20130306007A1

Abstract

Disclosed is a device 1 for providing clean combustion air 10 to an internal combustion engine 11 of a working tool 100, in particular of a handheld working tool, such as a chainsaw, an angle grinder, a working tool for the yard and landscape maintenance or the like. The device comprises a cyclone filter 12, into which ambient air 13, which is contaminated with impurities, can be sucked. A partial air flow 14, which is contaminated with impurities, can be extracted by suction from the cyclone filter 12. A second partial air flow 15, which is clean and substantially free from impurities, is branched off from the cyclone filter 12 and can be supplied to the internal combustion engine 11 as combustion air 10. A fan 16 is provided which can provide cooling air to flow against the internal combustion engine 11. The fan 16 is at least partially accommodated in a housing 17, 17a at least one suction bore 18 is provided which leads into the housing 17, 17a. A flow element surface 19, 20 is provided to control the flow of air to create an area of low pressure. The partial air flow 14, which is contaminated with impurities, is connected to the suction bore 18.

Description

DEVICE FOR PROVIDING CLEAN COMBUSTION AIR FOR THE INTERNAL

COMBUSTION ENGINE OF A WORKING TOOL

D E Sc RI PTI ON The instant invention relates to a device for providing clean combus-tion air for the internal combustion engine of a working tool, in particular of a handheld working tool, such as a chainsaw, an angle grinder, a working tool for the yard and landscape maintenance and the like, wherein provision is made for a cyclone filter, into which ambient air, which is contaminated with impurities, can be sucked, wherein a partial air flow, which is contaminated with impurities, can be extracted by suction from the cyclone filter, wherein a partial air flow, which is substantially freed from impurities, is furthermore branched off from the cyclone filter and can be supplied to the internal combustion engine as combustion air, and wherein provision is made for a fan, by means of which cooling air can flow against the internal combustion engine and wherein the fan is at least partially accommodated in a housing.

PRIOR ART

A device for providing clean combustion air for the internal combus- tion engine of a working tool, which is embodied as an angle grinder, for exam- pIe, is known from DE 10 2004 058 136 Al. The device comprises a cyclone fil-ter, into which ambient air, which is contaminated with impurities, is sucked, wherein a partial air flow, which is contaminated with impurities, is extracted by suction from the cyclone filter, wherein the extraction by suction is created by means of a low pressure, which is created by means of the rotary motion of a fan. For this purpose, the fan encompasses a so-called rear blading, through which, in an outlet port, into which the partial air flow that is contaminated with impurities leads, is sucked. Disadvantageously, an installation space is required for the rear blading of the fan, and the front blading of the fan, which serves to provide a cooling air, by means of which the internal combustion engine, in par- ticular the cylinder of the internal combustion engine is cooled, must be embo-died so as to be smaller due to the limited installation space of the fan in a housing, whereby only a smaller quantity of cooling air can be provided to the internal combustion engine.

A further device for providing clean combustion air for the internal combustion engine of a working tool, which is also embodied as an angle grind-er, for example, is known from DE 20 2006 002 330 Ui. To create a partial air flow, which is contaminated with impurities, for a cyclone filter, a low pressure is also provided by means of a fan, which substantially serves to cool the inter-nal combustion engine and in particular the cylinder of the internal combustion engine. A bore, which is fluidically connected to the partial air flow of the cyc-lone filter, which is contaminated with impurities, is created in the central axis of rotation of the fan. In the event that the fan is rotated, for example in that iO the fan is connected to the crankshaft of the internal combustion engine, a low pressure that finally serves to extract the partial airflow, which is contaminated with impurities, from the cyclone filter by means of suction, is created in the hub of the fan. Disadvantageously, the suction effect is limited by means of such an arrangement via the hub of the fan.

iS It is thus an aim of the instant invention to further develop a device for providing clean combustion air for the internal combustion engine of a moto-rized working tool such that said device is embodied so as to save installation space and so as to be efficient. It is in particular an aim of the instant invention not to use any additional elements, by means of which the low pressure is created in the partial air flow, which is contaminated with impurities.

This aim is solved based on a device for providing clean combustion air according to claim 1, based on a method for providing clean combustion air ac-cording to the preamble of claim 9 and based on a working tool comprising a device for providing clean combustion air according to claim 11. Advantageous further developments of the invention are specified in the dependent claims.

The invention includes the technical teaching that provision is made in the housing for at least one suction bore, which leads into the housing and that provision is made in the area of the suction bore for a flow element for creating a low pressure, wherein the partial air flow, which is contaminated with impuri-ties, is connected to the suction bore.

The invention is based on the idea of forming a Venturi nozzle, by means of which a low pressure can be created in the known manner, by means of a suction bore and a flow element in the housing, in which the fan is accom-modated. For this purpose, provision is made according to the invention in the housing for a suction bore, which leads into the area, in which the fan is ac-commodated in the housing. In the event that the internal combustion engine of the working tool is operated, the fan typically rotates permanently about an axis, which is formed by means of the crankshaft of the internal combustion en-gine, for example. A low pressure is thus permanently provided in the suction bore, which can be connected to the cyclone filter. The connection between the suction bore of the Venturi nozzle in the housing and the cyclone filter can be established by means of a hose connection or by means of a pipe connection, by means of which the partial air flow, which is contaminated with impurities, is created. The contaminated partial air flow can thus be extracted by suction from the cyclone filter and can be guided into the housing, and the air flow in the housing, which is created by means of the fan, only serves to cool the inter- nal combustion engine, in particular the cylinder of the internal combustion en- gine. This does not disadvantageously impact the function of the internal com-bustion engine and the formed Venturi nozzle does not require any additional installation space. An effective separation of impurities from the partial air flow, which is supplied to the internal combustion engine as combustion air, for ex-ample after passing through a further filter for fine-dedusting, can be ensured due to the high suction effect in the suction bore by utilizing the Venturi nozzle effect.

For example, the housing can encompass a flow chamber, in which the fan is arranged so as to rotate about an axis, wherein the suction bore leads into the flow chamber, in particular wherein the fan creates an air flow in the mouth area of the suction bore. The flow chamber can encompass a snail shell-like con-tour, for example, and the suction bore can be embodied so as to be oriented radially towards the axis of the fan, for example. In the alternative, the suction bore in the bottom wall of the housing can extend parallel to the axis of the fan.

The fan can be embodied as tangential fan, so that the fan wheel is flown against approximately axially, for example, and the air to be supplied to the in-ternal combustion engine is initially accelerated into a rotary motion about the axis, so that the air flow is created in the mouth area of the suction bore. The air flow can subsequently leave the fan area approximately tangentially, wherein at least one suction bore can preferably be introduced into an area in the housing, in which the air flow is particularly strong, so as to create a correspondingly strong suction effect in the suction bore.

By providing the low pressure for the partial air flow, which is conta- minated with impurities, according to the invention by arranging a Venturi noz-zle in the housing for accommodating the fan, the construction of a fan is made possible, which is only equipped on one side with fan blades, which serve to create the airflow in the mouth area of the suction bore. By means of the one-sided blading of the fan, the air flow for cooling the internal combustion engine can be embodied in a particularly strong manner, because the fan blades can be embodied so as to be larger than when the fan encompasses a rear blading, which would only serve to create a low pressure.

According to a possible advantageous embodiment of the flow ele- ment, it can form a constriction contour in a housing part of the housing, in par- ticular in the housing part, into which the suction bore leads, and/or the con- striction contour is embodied so as to be located opposite the mouth of the suc-tion bore in the housing. In both arrangements, a low pressure can be created in the mouth area of the suction bore, because the air flow in the housing is acce-lerated by means of the flow constriction, whereby the suction effect is created.

The flow element, which is embodied as constriction contour, can en-compass the profile of an upper wing side of an airfoil wing, for example, wherein the suction bore leads into the flow chamber, downstream from the highest profile point in the upper wing side. A particularly strong suction effect is utilized through this, because the strongest low pressure prevails downstream from the highest profile point in the upper wing side. The constriction contour in the form of an upper wing side can already be embodied in the injection molding of a plastic housing, for example, so that the housing itself forms the constriction contour. In the alternative, an additional component can be ar-ranged on the inner side of the housing, into which the suction bore has already been introduced for forming the constriction contour.

According to a further possible embodiment, the flow element can be embodied as airfoil wing profile, which is arranged close to the mouth of the suction bore in the housing, here in particular in the flow chamber. The airfoil

S

wing profile can thereby be arranged in the flow chamber, so that the air flow can flow completely around it at least from a bottom wing side and from an up-per wing side. The flow element in the form of an airfoil wing profile thus does not only need to be embodied as contour in the housing, but the airfoil wing profile can also be arranged freely in the flow chamber, and a low pressure is created in particular on the upper wing side, so that the airfoil wing profile can be arranged in the air flow, with the upper wing side facing in the direction of the suction bore. It goes without saying that a first flow element, which is em-bodied as constriction contour in the housing, and a second flow element, which is embodied so as to be arranged freely in the flow chamber as airfoil wing profile, can be combined with one another.

The instant invention is further directed to a method for providing clean combustion air for an internal combustion engine of a working tool, in particular of a handheld working tool, such as a chainsaw, an angle grinder, a working tool for the yard and landscape maintenance and the like, wherein pro-vision is made for a cyclone filter, into which ambient air, which is contaminated with impurities, is sucked, wherein a partial air flow, which is contaminated with impurities, is extracted by suction from the cyclone filter, and wherein a partial air flow, which is substantially freed from impurities, is furthermore branched off from the cyclone filter and is supplied to the internal combustion engine as combustion air, and wherein provision is made for a fan, by means of which cooling air flows against the internal combustion engine. The fan is at least par- tially accommodated in a housing, wherein at least one suction bore is intro-duced into the housing and wherein a low pressure is created in the area of the suction bore in connection with at least one flow element, wherein the partial air flow, which is contaminated with impurities, is extracted through the suction bore by suction by means of the low pressure. The features and advantages of the above-described device can also be considered for the method according to the invention.

The invention is further directed to a working tool comprising a device according to the above-described type, in particular for operating a method for providing clean combustion air for an internal combustion engine of the work-

ing device according to the above description.

BRIEF DESCRIPTION OF THE DRAWINGS

Further measures, which improve the invention, will be illustrated in more detail below by means of the figures together with the description of pre-ferred exemplary embodiments of the invention.

Fig. 1 shows a perspective view of a working tool comprising a device for providing clean combustion air, Fig. 2 shows a top view onto a first exemplary embodiment of a device for providing clean combustion air, Fig. 3 shows a side view of the exemplary embodiment of the device according to Figure 2 and Fig. 4 shows a further exemplary embodiment of a device in a top view.

PREFERRED EMBODIMENTS OF THE INVENTION

Fig. 1 shows an exemplary embodiment of a working tool 100 compris-ing an internal combustion 11, which is not shown explicitly and which serves to drive a tool 25. The internal combustion engine 11 is supplied with an ambient air 13, which can pass through ventilating slits 26, which are introduced into a housing 17 of the working tool 100. The housing 17 serves primarily to accom-modate a fan 16 and for correspondingly guiding an air flow 23 to the internal combustion engine 11, as is illustrated in more detail in the following figures.

In a top view, Fig. 2 shows a part of the working tool 100 according to Figure 1 comprising a device 1 for providing clean combustion air to the internal combustion engine 11. The housing 17 is illustrated without the housing cover, which is shown with ventilating slits 26 in Fig. 1, and the view shows a further housing part 17a. A fan 16, which encompasses a plurality of fan blades 24, which are arranged on the front side of the fan wheel, is accommodated in this housing part ha so as to rotate about an axis 22. The axis 22 can be formed by an end of the crankshaft of the internal combustion engine 11, for example. The housing part 17a encompasses an accommodating depression for accommodat- ing the fan 16, and the accommodating depression increases in a radially ex- panding manner in the direction of the cylinder of the internal combustion en- gine 11, so that an approximately logarithmic spiral is created, and a flow cham-ber 21 is formed by means of it. A flow, which substantially rotates about the axis 22 and which is created by means of the guide blades 24 of the rotating fan 16, is created in this flow chamber 21.

According to the invention, a flow element 19 in the form of a con-striction contour 19 is embodied in the bottom area of the flow chamber 21, and two suction bores 18 lead into the constriction contour 19. The air flow 23 accelerates above the constriction contour 19, so that a low pressure is created in the air flow 23 according to Bernoulli and a suction is consequently created in the suction bores 18. A detailed illustration of the device 1 for providing clean combustion air 10 for the internal combustion engine 11 in particular in opera-tive connection with the cyclone filter 12 is shown in Fig. 3 in more detail.

Fig. 3 shows a side view of the housing 17, in which the non-illustrated fan 16 is accommodated. The cross sectional view of the housing part 17a of the housing 17 illustrates the constriction contour 19, through which the suction bore 18 extends and which leads into the flow chamber 21, viewed in flow di-rection, downstream from the highest profile point 27. The illustration of the air flow 23 shows an acceleration area of the flow above the constriction contour 19, so that a low pressure is created in the mouth area of the suction bore 18.

A cyclone filter 12, into which ambient air 13 is sucked, which is con- taminated with impurities, is furthermore shown. A partial air flow 14 is fluidi- cally connected to the suction bore 18, and air, which is contaminated with im-purities, can be extracted by suction from the cyclone filter 12 via the partial air flow 14 by means of the low pressure, which is created in the mouth area of the suction bore 18. The embodiment of a Venturi nozzle is thereby created by means of the arrangement of the suction bore 18 in combination with the con- striction contour 19, and contaminated air is extracted by suction from the cyc-lone filter 12 via the partial air flow 14 by means of the Venturi effect.

A further partial air flow 15 leaves the cyclone filter 12 in a state, which is substantially freed from impurities, and the partial air flow 15, which is pre-cleaned by means of the cyclone filter 12, is fine-dedusted by means of a further filter 28, which is embodied as paper filter or fabric filter, for example, and the combustion air 10, which is provided with this, can be supplied to the internal combustion engine 11.

Fig. 4 shows a further exemplary embodiment of a device 1 for provid-ing clean combustion air 10 for the internal combustion engine 11 of a work tool according to Fig. 1. The illustration shows the housing part ha of the hous- ing 17, as it is part of the working tool 100 according to Fig. 1. The fan 16 is ac-commodated in the housing part 17a so as to rotate about the axis 22, and the fan 16 encompasses fan blades 24 for creating an air flow 23 in the flow cham-ber 21, which is formed in the housing part 17a. A suction bore 18, which leads into the flow chamber 21 and thus into the air flow 23, is introduced into the wall of the housing part 17A. As shown in an implied manner, the suction bore 18 is in turn connected to the partial air flow 14 of the cyclone filter 12, through which ambient air 13 is sucked in. The partial air flow 14 is thereby contami-nated with impurities and the further provided partial air flow 15 is pre-cleaned and can be supplied to the internal combustion engine 11 of the working tool as combustion air 10 after passing through the filter 28.

The flow element 20 is embodied as airfoil wing profile 20 and is in-serted in the flow chamber 21 at a distance upstream of the mouth area of the suction bore 18. In the event that the air flow 23 flows completely around the airfoil wing profile 20, an acceleration of the air flow 23 is created on the upper side of the airfoil wing profile 20, which faces in the direction of the suction bore 18, whereby a low pressure is in turn created again in the mouth area of the suction bore 18. Through this, contaminated air can be extracted by suction from the cyclone filter 12 via the partial air flow 14 in the manner, which has already been described, wherein the impurities enter into the air flow 23, which substantially serves only to cool the internal combustion engine 11.

The embodiment of the invention is not limited to the exemplary em- bodiments, which have only been shown in an exemplary manner above. In-stead, a number of alternatives is possible, which utilizes the illustrated solution even in the case of embodiments, which are of a generally different type. All of the features and/or advantages, which follow from the claims, the description or the drawings, including structural details or spatial arrangements, can be sig- nificant for the invention, both alone and in a variety of combinations. In partic- ular, the flow element, embodied in an exemplary manner as constriction con-tour 19 or as airfoil wing profile 20, can be embodied in any other way so as to create a low pressure in the mouth area of the suction bore 18. In particular, provision can also be made in a flow path of the air flow 23 from the fan 16 to the internal combustion engine 1]. for a section, which is geometrically embo-died in another way such that the Venturi effect can be utilized, so as to create a low pressure on the side of the partial air flow 14 of the cyclone filter 12. The invention is thus not limited to the arrangement of a corresponding flow geo-metry in the housing part 17A, and it is possible, for example, to also provide a geometric embodiment for utilizing a Venturi effect in a bypass. For example, the cyclone filter 21 can geometrically adjoin the flow chamber 21 with only one intermediate wall such that a connection as hose line or pipeline for the partial air flow 14 is no longer necessary, and a connection between the cyclone filter 12 and the flow chamber 21 can be limited to the suction bore 18. A combina-tion of the flow elements 19 and 20 is furthermore possible, so that an airfoil wing profile 20 can be provided so as to be spaced apart from a constriction contour 19, wherein both flow elements 19 and 20 are arranged in the air flow 23.

LIST OF REFERENCE NUMERALS

working tool 1 device 10 combustion air 11 internal combustion engine 12 cyclone filter 13 ambient air 14 partial flow contaminated 15 partial flow clean 16 fan 17 housing 17a housing part 18 suction bore 19 flow element, constriction contour flow element, airfoil wing profile 21 flow chamber 22 axis 23 airflow 24 fan blade tool 26 ventilating slits 27 highest profile point 28 filter

Claims

CLAIMS1. A device (1) for providing clean combustion air (10) for the internal combustion engine (11) of a working tool (100), in particular of a handheld working tool, such as a chainsaw, an angle grinder, a working tool for the yard and landscape maintenance and the like, wherein -provision is made for a cyclone filter (12), into which ambient air (13), which is contaminated with impurities, can be sucked; -a partial air flow (14), which is contaminated with impurities, can be extracted by suction from the cyclone filter (12); -a partial air flow (15), which is substantially freed from impurities, is furthermore branched off from the cyclone filter (12) and can be supplied to the internal combustion engine (11) as combustion air (10); -provision is made for a fan (16), by means of which cooling air can flow against the internal combustion engine (11); -the fan (16) is at least partially accommodated in a housing (17, 17a); -provision is made in the housing (17, 17a) for at least one suction bore (18), which leads into the housing (17, ha); -provision is made in the area of the suction bore (18) for a flow ele-ment (19, 20) for creating a low pressure; and -the partial air flow (14), which is contaminated with impurities, is connected to the suction bore (18).
2. The device (1) according to claim 1, wherein the housing (17, 17a) encompasses a flow chamber (21), in which the fan (16) is arranged so as to ro- tate about an axis (22), wherein the suction bore (18) leads into the flow cham-ber (21), in particular wherein the fan (16) creates an air flow (23) in the mouth area of the suction bore (18).
3. The device (1) according to claim 1 or 2, wherein the air flow (23) serves to flow against the internal combustion engine (11) and in particular the cylinder of the internal combustion engine (11).
4. The device (1) according to one of claims 1 to 3, whereIn the tan (16) is equipped on one side with fan blades (24), which serve to create the air flow (23) in the mouth area of the suction bore (18).
5. The device (1) according to one of the afore-mentioned claims, wherein the flow element (19) is embodied as constriction contour (19) in a housing part (17a) of the housing (17), in particular into which the suction bore (18) leads and/or the constriction contour (19) is embodied so as to be located opposite the mouth of the suction bore (18) in the housing (17, 17a).
6. The device (1) according to claim 5, wherein the flow element (19), which is embodied as constriction contour (19), encompasses a profile of an upper wing side of an airfoil wing, wherein the suction bore (18) leads into the flow chamber (21), preferably downstream from the highest profile point (27) in the upper wing side.
7. The device (1) according to one of the afore-mentioned claims, wherein the flow element (20) is embodied as airfoil wing profile (20), which is arranged close to the mouth of the suction bore (18) in the housing (17, 17a), in particular in the flow chamber (21).
8. The device (1) according to claim 7, wherein the airfoil wing profile (20) is arranged so that the air flow (23) can flow completely around it at least from a bottom wing side and from an upper wing side, in particular wherein the airfoil wing profile (20) is arranged in the air flow (23), with the upper wing side facing in the direction of the suction bore (18).
9. A method for providing clean combustion air (10) for an internal combustion engine (11) of a working tool (100), in particular of a handheld working tool, such as a chainsaw, an angle grinder, a working tool for the yard and landscape maintenance and the like, wherein -provision is made for a cyclone filter (12), into which ambient air (13), which is contaminated with impurities, is sucked, -a partial air flow (14), which is contaminated wIth impuritIes, is ex-tracted by suction from the cyclone filter (12); -a partial air flow (15), which is substantially freed from impurities, is furthermore branched off from the cyclone filter (12) and is supplied to the in-ternal combustion engine (11) as combustion air (10); -provision is made for a fan (16), by means of which cooling air flows against the internal combustion engine (11); -the fan (16) is at least partially accommodated in a housing (17, 17a); -at least one suction bore (18) is introduced into the housing (17, ha); -a low pressure is created in the area of the suction bore (18) in con-nection with at least one flow element (19, 20); and -the partial airflow (14), which is contaminated with impurities, is ex-tracted by suction by means of the low pressure through the suction bore (18).
10. The method according to claim 9 for providing clean combustion air (10) for an internal combustion engine (11) of a working tool (100) compris-ing a device (1) according to one of claims 2 to 8.
11. A working tool (100) comprising a device (1) according to one of claims 1 to 8, in particular for operating a method for providing clean combus-tion air (10) for an internal combustion engine (11) of the working tool (100) according to claim 9 or 10.