CN100538038C - The venting gas appliance of oil-engine driven working equipment - Google Patents

Abstract

The present invention relates to the venting gas appliance of the working equipment that a kind of internal-combustion engine (1) drives, especially prune the shear that hedge uses or the venting gas appliance of similar working equipment.This venting gas appliance comprises the outlet pipe (2) that is used for exhaust flow (3), and wherein said outlet pipe (2) is in communication with the outside by exhaust end (4).The inwall (5) of outlet pipe (2) be provided with make that the air-flow cross section narrows down around coagulant induction element (6).

Description

Exhaust devices for working equipment powered by internal combustion engines

technical field

The invention relates to an exhaust device for manually controlled work equipment driven by an internal combustion engine.

Background technique

Manually controlled work equipment, such as hedge shears, free cutters, chainsaws or similar equipment, is driven by an internal combustion engine, which in its usual design is deprived of lubrication. Especially when using two-stroke engine designs, the fuel/air mixture introduced into the engine contains a small amount of lubricating oil components, which after passing the engine are guided in the form of a fine mist together with the resulting exhaust gas flow lead to the outside world. In addition to the above-mentioned oil mist, combustion residues, air moisture or similar substances can also form mist, which is also seen in four-stroke motors.

Clearly, the aforementioned species in the exhaust stream tend to form a film of condensate on the interior surfaces of the exhaust. In certain configurations it can be seen that the condensate film is carried in the direction of the exhaust gas flow. Condensation accumulations can form in the region of the discharge end of the exhaust pipe, which drip down at the discharge end or even flow back on the outside of the exhaust pipe in the direction of the engine. This leads to annoying contamination, necessitating frequent cleaning of the working equipment.

Contents of the invention

The object of the present invention is to improve an exhaust system of the aforementioned type in such a way that contamination is avoided.

This task is achieved by the exhaust described below.

According to the invention there is provided an exhaust system for a working machine driven by an internal combustion engine, comprising an exhaust pipe for the flow of exhaust gas, wherein the exhaust pipe communicates with the environment via an outlet port. A circumferential condensate guide element, which narrows the flow cross-section, is arranged on the inner wall of the exhaust pipe. The exhaust pipe follows the exhaust muffler, wherein the condensate guiding element is located on the pipe section outside the exhaust muffler.

The surrounding configuration of the condensate guide element in the circumferential direction prevents a movement of the condensate film in the direction of the exhaust gas flow. A condensate directing element extends radially inwardly from the inner wall of the exhaust pipe. Condensation that builds up or deposits on the wall of the exhaust pipe accumulates in this area and is deflected radially inwards. At the same time, the surrounding condensate-guiding element narrows the free flow cross-section due to the radial inward extension of the condensate-guiding element. The velocity of the exhaust gas flow is locally increased here. Due to the increased flow velocity of the exhaust gas flow, the accumulated and inwardly directed condensate is carried along and conveyed to the environment. Condensation dripping from the exhaust pipe is avoided.

In a further preferred refinement, the exhaust line is connected downstream of an exhaust muffler, wherein the condensate guiding element is located in a line section outside the exhaust muffler. The outer pipe section of the exhaust pipe has no hot exhaust gas recirculation. Relatively cold conditions favor condensation formation. The arrangement of the condensate-guiding element in this region has the result that condensate in the exhaust gas flow acts again almost directly at the point where the condensate forms. The accumulation of further condensate and the resulting risk of droplet formation is thus reliably avoided.

The condensate guiding element is advantageously arranged directly upstream of the discharge end. Recondensation or deposition of condensed matter which is conducted back into the exhaust gas flow is prevented.

In a preferred embodiment, the condensate guide forms a separation point for the exhaust gas flow in its cross-section. The concept of separation points chosen here is not limited to angular shapes. It includes all aerodynamic shapes that narrow the airflow cross-section of the exhaust pipe and that, unlike venturi formations, produce an airflow separation effect that subsequently separates from the surface in a vortex. The flow contour of the condensate-guiding element and the subsequent swirl formation promote the entrainment of the exhaust gas flow on the condensate film on the wall side.

The entrained condensate droplets are carried into the inner, adaxial region of the exhaust gas flow, which makes it difficult to generate new deposits on the following tube walls.

In a suitable refinement, the condensate guiding element extends helically along the inner wall of the exhaust pipe. The axially extending helical shape allows, to a limited extent, the deposited condensate film condensed on the wall side to move axially and thus to distribute over the axial extension of the condensate guiding element. If the condensate is distributed over the length of the condensate guiding element, the condensate guiding element can more effectively guide deposited condensate back into the exhaust gas flow. When the structural dimensions are small, the number of helices required for a sufficient guiding action is between two helices and six helices, wherein an embodiment with four helices is preferred.

In an advantageous embodiment, the condensate guiding element is introduced with its downstream end into the region of the center axis of the exhaust pipe. The remaining condensate that is not guided back into the exhaust gas flow over the structural length of the condensate guiding element flows in the exhaust gas flow direction at the condensate guiding element until it reaches the downstream end of the condensate guiding element. In this case, the condensate is guided to the region of the center axis, which is better taken up and carried away by the exhaust gas flow. The formation of residual condensate is avoided.

In a reasonable embodiment, the condensation guiding element is made in the form of a helical wire spring. The circular shape of the wire cross-section is effective both for collecting the deposited condensate stream and for draining it in a vortex-forming way with the exhaust gas flow. This advantageous effect is also accompanied by a simple and inexpensive construction.

Preferably the upstream end of the wire spring is bent radially inwardly. This inwardly bent wire end can be used in a simple manner as an assembly aid. At the same time, this wire end protruding into the gas flow cross-section serves to create a vortex for better re-acceptance of the condensate.

In an advantageous embodiment, the wire spring is fastened radially pretensioned in the exhaust pipe. The radial pretensioning, in addition to producing a secure positional fixation, also results in a compression force between the spring and the inner wall. In this area, it is worth noting the sealing effect. The condensate film cannot penetrate between the wire spring and the tube wall. Furthermore, the condensate film is deflected radially inwards around the wire cross-section of the wire spring, wherein the characteristics of the reintroduction into the exhaust gas flow are optimized.

Description of drawings

Embodiments of the present invention are further described below in conjunction with the accompanying drawings. The picture shows:

Figure 1 is a schematic diagram of a manual working device taking the example of hedge shears with an exhaust device represented as a block diagram;

Fig. 2 is a three-dimensional transparent view of the exhaust pipe of the structure shown in Fig. 1 and the condensate guiding element arranged therein;

Figure 3 is an enlarged cross-sectional schematic diagram of the flow characteristics at the line cross-sectional area of the condensate guiding element of the structure shown in Figure 2;

Figure 4 is a three-dimensional part view of the condensate guide element in the form of a wire spring shown in Figure 2;

FIG. 5 is a deformation of the wire spring shown in FIG. 4 with the wire ends stretched in the region of the central axis.

Detailed ways

FIG. 1 shows a perspective view of a manual working device driven by an internal combustion engine 1 , for example hedge shears. In addition to shears for hedge trimming, free cutters, grinders, chain saws or similar equipment can also be used.

The internal combustion engine 1 , which is not shown in any further detail, is fixed in a housing 17 and is almost completely covered by the housing 17 . In the view shown here, only the spark plug 20 of the internal combustion engine 1 and the starter handle 19 for starting the internal combustion engine 1 are visible.

For guiding the hedge shears, a front handle 15 and a rear handle 16 are provided, whereby the scissors blade 18 driven by the internal combustion engine 1 can be guided along the vegetation to be cut.

In the illustrated embodiment, the internal combustion engine 1 is a two-stroke internal combustion engine with loss lubrication, the fuel with which it operates has a lubricant oil component mixed therein. Also possible are independent lubrication and at least virtually loss-free lubrication with separate lubricant tanks on engines such as four-stroke engines.

Exhaust gases generated during operation of the internal combustion engine 1 are discharged to the environment via an exhaust system which is covered by the housing 17 and is schematically represented as a block diagram in the drawing. For this purpose, the exhaust system comprises an exhaust muffler 7 and an exhaust pipe 2 downstream in the flow direction. The exhaust gas flow indicated by the arrow 3 first passes through the exhaust muffler 7 and then through the exhaust pipe 2 until it flows to the environment at the free outlet end 4 of the exhaust pipe 2 . In order to form the flow-guiding connection, the inner pipe section 9 of the exhaust pipe 2 protrudes into the exhaust muffler 7 . A pipe section 8 downstream of this exhaust pipe 2 runs outside the housing of the exhaust muffler 7 . Immediately adjacent to the exhaust gas end 4 , upstream of this in the outer pipe section 8 , there is a schematically indicated condensate guide element 6 which will be explained in more detail below.

FIG. 2 is an enlarged transparent view of the exhaust pipe 2 shown in FIG. 1 . The exhaust pipe 2 has a circular cross section and runs along a central axis 12 . Arranged at the discharge end 4 is a condensate guide 6 which, in the exemplary embodiment shown, is in the form of a helical wire spring 14 . The helical wire spring 14 or helical spring is pushed into the free end of the exhaust pipe 2 next to the outlet end 4 under radial pretension. Due to the radial pretension, the wire spring is fixed in place frictionally and positively, and bears on the inner side against the inner wall 5 of the exhaust pipe 2 . In order to fix the axial position of the wire spring 14 , a schematically indicated axial positioning device 21 is provided at the discharge end 4 of the exhaust pipe 2 .

The exhaust pipe 2 provides the exhaust gas flow 3 with an undisturbed circular gas flow cross section upstream of the condensate guiding element 6 . The flow cross-section is narrowed by wire springs 14 which run around multiple times in the circumferential direction of the exhaust pipe 2 and are lifted radially inwards from the inner wall 5 .

The air flow behavior at the condensate guide element 6 is shown schematically enlarged in FIG. 3 . The circular cross-section of the wire 22 of the wire spring 14 ( FIG. 2 ) is pressed against the inner wall 5 of the exhaust pipe 2 . The flow direction of the exhaust gas flow 3 is indicated by flow lines, here only two flow lines 27 close to the wall are indicated for better clarity. Upstream along the line 22 , a condensate film 23 is deposited on the inner wall 5 . As a result of the exchange with the exhaust gas flow and, if applicable, the force of gravity, the condensate film 23 is displaced in the direction of the exhaust gas flow 3 in the direction of the discharge end 4 ( FIG. 2 ). As can be seen from FIG. 3 , the condensate film 23 is consequently blocked upstream of the line 22 , and the condensate guiding element 6 is guided away from the inner wall 5 in the direction of the central axis 12 ( FIG. 2 ).

The chosen aerodynamic shape of the circular cross-section of the line 22 leads to a laminar interruption of the exhaust gas flow 3 . Upstream, at the greatest distance from the inner wall 5 , there is formed a separation point 26 behind which the gas flow separates from the surface of the condensate guide element 6 and the subsequent section of the inner wall 5 . This forms the vortex 25 shown. The separation point 26 associated with the cross-section of the wire 22 forms a separation line about the median axis ( FIG. 2 ) along the length of the wire, so that at least a considerable part of the exhaust gas flow 3 close to the wall is swirled downstream of the condensate guiding element 6 . In addition to the circular cross-section of the line 22 shown, other suitable cross-sectional shapes can also be used, for example an angular cross-sectional shape which forms an aerodynamic separation point 26 .

The narrowing of the free flow cross-section due to the action of the condensate guiding element 6 results in a local acceleration of the exhaust gas flow 3 represented by the reduced spacing of the flow lines 27 in the figure, and this local acceleration of the exhaust gas flow 3 is approximately at the condensate guiding element 6 Its maximum value is reached in the region of the maximum radial projection relative to the inner wall 5 . The exhaust gas flow 3 and/or gravity guides the condensate film 23 around the cross-section of the wire 22 until reaching the aforementioned area. There, the high gas flow velocity together with the separating eddies separates the condensate film 3 into individual, schematically indicated droplets 24 which are pushed forward by the exhaust gas flow 3 but do not deposit again on the inner wall 5 . The separation point 26 and the droplet 24 are spaced at a radial distance from the inner wall 5 in order to avoid new agglomerations.

FIG. 4 shows a perspective view of parts of the wire spring 14 shown in FIG. 2 . The wire spring 14 suitably comprises two to six threaded coils 10 . In the exemplary embodiment shown, substantially more than four coil turns of the helix 10 are provided. The wire spring 14 is bent radially inwards at its upstream end 13 so that this end 13 protrudes inwards in the flow cross-section of the exhaust gas flow 3 ( FIG. 2 ).

A variant of the wire spring 14 shown in FIG. 4 is shown in FIG. 5 , which is related to the flow direction of the exhaust gas flow 3 ( FIG. 2 ) and at the downstream end 11 from the helix 10 extending radially inwards from the circumferential side until reaching the wire spring 14 The longitudinal axis 28. There, the downstream end 11 is bent in the direction of the longitudinal axis 28 . In the assembled state, the screw 10 rests helically on the inner wall 5 of the exhaust pipe 2 as in the embodiment shown in FIGS. 2 and 4 . In this case, the longitudinal axis 28 coincides with the center axis 12 ( FIG. 2 ) of the exhaust pipe 2 . As a result, the downstream end 11 of the wire spring 14 is located at least approximately in the middle axis 12 of the exhaust pipe 2 or in the center of the flow cross-section of the exhaust gas flow 3 . The other features and reference numerals of the embodiment of FIG. 5 are the same as in FIG. 4 .

In the exemplary embodiment shown here, the condensate guiding element 6 is designed as a helical wire spring 14 . Slats, profile embossing on the peripheral wall of the exhaust pipe 2 or similar other forms can also be advantageous. In addition to the spiral curve, a circular orifice plate structure is also possible, in which several circular plates can also be arranged in series.

Claims (11)

1. the venting gas appliance by the working equipment of internal-combustion engine (1) driving comprises the outlet pipe (2) that is used for exhaust flow (3), and wherein said outlet pipe (2) is in communication with the outside by exhaust end (4),

It is characterized in that, the inwall (5) of described outlet pipe (2) be provided with make that the air-flow cross section narrows down around coagulant induction element (6), and described outlet pipe (2) is connected on exhaust silencer (7) back, and wherein said coagulant induction element (6) is positioned at the outside area under control section (8) of described exhaust silencer (7) and locates.

2. venting gas appliance as claimed in claim 1 is characterized in that, described coagulant induction element (6) is being close to described exhaust end (4) in the upstream of described exhaust end (4).

3. venting gas appliance as claimed in claim 1 is characterized in that, described coagulant induction element (6) is formed with the separation point (26) of described exhaust flow (3) on its cross section.

4. venting gas appliance as claimed in claim 1 is characterized in that, described coagulant induction element (6) extends along inwall (5) the spirality ground of described outlet pipe (2).

5. venting gas appliance as claimed in claim 4 is characterized in that, described coagulant induction element (6) has two to six spirals (10).

6. venting gas appliance as claimed in claim 5 is characterized in that, described coagulant induction element (6) has four spirals (10).

7. as each described venting gas appliance in the claim 4 to 6, it is characterized in that the downstream (11) of described coagulant induction element (6) is directed on the zone of medial axis (12) of described outlet pipe (2).

8. venting gas appliance as claimed in claim 4 is characterized in that, described coagulant induction element (6) is spiral wire spring (14).

9. venting gas appliance as claimed in claim 8 is characterized in that, described wire spring (14) (13) is at its upstream end located radially to curve inwardly.

10. venting gas appliance as claimed in claim 8 is characterized in that, is fixed in the described outlet pipe (2) described wire spring (14) radial tightening.

11. venting gas appliance as claimed in claim 1 is characterized in that, described working equipment is to prune the shear that hedge is used.

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