Engine air intake structure

An engine air intake structure includes an electronically controlled throttle and an air intake pipe which delivers intake air to an air intake port of the engine. The electronically controlled throttle is attached to the air intake pipe. The electronically controlled throttle includes: a throttle valve which regulates the amount of air to be supplied to the engine; a throttle body which accommodates the throttle valve therein; and an electronic control unit which controls the throttle valve. The electronic control unit includes a control circuit board which is arranged to a side of the throttle body which faces away from an engine body of the engine.

BACKGROUND OF THE INVENTION

Field of the Invention

The present disclosure relates to an engine air intake structure to supply air to an engine.

Description of Related Art

An engine is often provided with an electronically controlled throttle which includes a throttle valve that regulates the amount of air to be supplied to the engine and an electronic control unit that controls the throttle valve. The electronic control unit for such an engine is often positioned to face towards the engine interior, in order to prevent foreign objects from colliding therewith during the operation of the engine. This means that the electronic control unit is arranged adjacent to an engine body of the engine. Such arrangement makes it difficult for the space around the electronically controlled throttle to be used more efficiently.

SUMMARY OF THE INVENTION

An object of the present disclosure is to provide an engine air intake structure, which structure allows the space around an electronically controlled throttle to be used more efficiently.

The present disclosure provides an engine air intake structure, which engine includes an electronically controlled throttle and an air intake pipe which delivers intake air to an air intake port of the engine. The electronically controlled throttle is attached to the air intake pipe. The electronically controlled throttle includes: a throttle valve which regulates the amount of air to be supplied to the engine; a throttle body which accommodates the throttle valve therein; and an electronic control unit which controls the throttle valve. The electronic control unit includes a control circuit board which is arranged to a side of the throttle body which faces away from an engine body of the engine.

According to this configuration, the control circuit board is arranged to a side of the throttle body which faces away from the engine body. In this way, space interference of the control circuit board with nearby components can be mitigated better than when the control circuit board is arranged between the throttle body and the engine body. For example, the throttle body can be arranged in closer relation to the engine body. In addition, a spacing can be secured between the throttle body and the engine body for installing additional components. In this way, the space around an electronically controlled throttle can be used more efficiently.

Any combinations of at least two features disclosed in the claims and/or the specification and/or the drawings should also be construed as encompassed by the present invention. Especially, any combinations of two or more of the claims should also be construed as encompassed by the present invention.

DESCRIPTION OF EMBODIMENTS

What follows is a description of preferred embodiments of the present disclosure made with reference to the drawings. The terms “upstream” and “downstream” used herein refer to the “upstream” and “downstream” in the direction of flow of intake air. The engine E in the instant embodiment is in the form of a so-called V engine in which two cylinder units6define cylinder axes AX1(FIG.3) that are open in a V shape. The term “cylinder axes” in this context refer to the central axes of the internal, cylindrical hollow bores of the cylinder units6.

In the rest of the discussions, the terms “front” and “forward(s)” refer to the V banks-side or a direction of opening of the V shape in the installed state of the engine in a work machine (e.g., a lawn mower and any type of agricultural or farming machines), whereas the terms “rear” and “rearward(s)” refer to an opposite side thereof. Also, a vertical direction VD refers to a direction of extension of the axis AX of a crankshaft2, whereas a widthwise direction WD refers to a direction perpendicular to both the vertical direction VD and a front-to-rear direction LD. In addition, in regard to the widthwise direction WD, the term “widthwise inside” refers to a side facing towards the axis AX of the crankshaft2, whereas the term “widthwise outside” refers to a side facing away from the axis AX of the crankshaft2.

Turning toFIG.1, an engine E comprising an engine air intake structure in accordance with a first embodiment of the present disclosure is in the form of a two-cylinder vertical-shaft, air-cooled engine with a rotary shaft extending in the vertical direction in the installed state of the engine. For example, the engine E is installed in a riding lawn mower. However, these are merely some of the non-limiting examples of the configuration and application of the engine E.

The engine E in the instant embodiment includes: a crankshaft2(which is an example of the rotary shaft of the engine) defining an axis AX extending in the vertical direction VD according toFIG.3; a crankcase4(FIG.3) which supports crankshaft2; and a pair of cylinder units6protruding forwards from the front of the crankcase4. One or more power transmission elements (not shown) are attached to an end of the crankshaft2for transmission of mechanical power to a work tool. In the remaining discussions, the terms “lower” and “downward(s)” refer to one end side of the crankshaft2in the vertical direction VD where the power transmission elements are to be attached according toFIG.2, whereas the terms “upper” and “upward(s)” refer to the other end side of the crankshaft2. In other words, the lower end of the crankshaft2couples to the power transmission elements as well as the work tool.

Turning toFIG.3, each of the cylinder units6includes a cylinder8having a base end coupled to the crankcase4and a cylinder head10coupled to the protruding end of the cylinder8. The cylinder axes AX1of the cylinder units6extend at an angle to each other and outwards in the widthwise direction WD towards the front. The cylinder axes AX1of the two cylinder units6define a V shape which is open towards the front. The crankcase4, the cylinders8, and the cylinder heads10form an engine body EB.

Turning back toFIG.1, cooling fins12are formed around the outer peripheries of the cylinder units6. The cooling fins12add more surface area to enhance the cooling performance of the air-cooled engine. Head covers14are attached to the front ends of the cylinder units6.

Turning again toFIG.3, an air cooling fan16is attached to the upper end of the crankshaft2. The air cooling fan16in the instant embodiment comprises a centrifugal fan. However, this is merely one of the non-limiting examples of the air cooling fan16. The cooling air generated by the air cooling fan16facilitates the cooling of the cylinder units6. The air cooling fan16is coupled to the upper end of the rotary shaft2of the engine. A fan housing18is attached to the crankcase4. The fan housing18covers the air cooling fan16from above and from the periphery, except for the front of the air cooling fan16.

A fan cover20is fitted on a top side of the fan housing18. The fan cover20is secured to the fan housing18so as to cover the top of the air cooling fan16according toFIG.2. The fan cover20has a plurality of slits that pass air A and let it flow into the fan housing18while preventing foreign matters larger than the slits from entering the fan cover20.

As the engine E starts and the crankshaft2rotates, the air cooling fan16is rotated as well in unison with the crankshaft2. Rotation of the air cooling fan16causes the air A to be drawn from above the engine E through the fan cover into the fan housing18. The fan housing18guides the air A, which has entered the fan housing18, into a downward stream of flow that cools components including the cylinder units6.

Turning again toFIG.1, an air cleaner26is arranged spaced apart from the cylinder units6in the direction of extension of the axis AX of the crankshaft2or, in the instant embodiment, arranged above the cylinder units6. The air cleaner26includes a cylindrical cleaner casing28and a cleaner element (not shown) inside the cleaner casing28to purify (or filter) air taken in from the environment. In the instant embodiment, the axis AX2of the cleaner casing28extends in the widthwise direction WD.

The air A which has been purified by the air cleaner26flows through an air intake pipe30and an electronically controlled throttle32and is distributed among the cylinders by an air intake manifold34which separates into left and right branches as shown inFIG.3. The air intake pipe30comprises an upstream air intake pipe30aand a downstream air intake pipe30bas shown inFIG.2. In the instant embodiment, the upstream air intake pipe30aand the downstream air intake pipe30bare formed of elastic material such as rubber.

The outlet of the air cleaner26connects to the upstream end30aaof the upstream air intake pipe30a, and the downstream end30abof the upstream air intake pipe30aconnects to the inlet32aof the electronically controlled throttle32. Further, the outlet32bof the electronically controlled throttle32connects to the upstream end30baof the downstream air intake pipe30b, and the downstream end30bbof the downstream air intake pipe30bconnects to the air intake manifold34(FIG.3). Accordingly, the air intake pipe30and the electronically controlled throttle32define an air intake passage IP extending between the air cleaner26and the air intake manifold34. How the electronically controlled throttle32and the air intake pipe30are coupled to each other will be further discussed later.

Turning back toFIG.3, the electronically controlled throttle32includes a throttle valve36which regulates the amount of air to be supplied to the engine E and an electronic control unit38which controls the throttle valve36. Hence, in addition to the throttle valve36and the electronic control unit38, the electronically controlled throttle32includes a throttle body40in which the air intake passage IP is defined and inside which the throttle valve36is positioned, and a valve stem42for the throttle valve36. In the instant embodiment, the throttle valve36, the electronic control unit38and the throttle body40are integrally constructed. The phrase “integrally constructed” in this context means that they are constructed in an inseparable manner and may even encompass an inseparable assembly of distinct components.

The throttle valve36comprises, for example, a butterfly valve and regulates the amount of air A that flows through the air intake passage IP in accordance with a command from the electronic control unit38. Turning toFIG.4, the electronic control unit38includes: a control circuit board44on which an electronic circuit is arranged; a motor46which actuates the throttle valve36; and a gearbox48accommodating a gearing which changes the speed of rotation from the motor46. Thus, rotation from the motor46is transmitted to the valve stem42with a speed changed by means of the gearing in the gearbox48to drive the throttle valve36shown inFIG.3into rotation. It should be understood that a butterfly valve is merely one of the non-limiting examples of the throttle valve36.

A fuel pump50is disposed on one of the opposite sides of the engine E in the widthwise direction WD on the front of the engine. The fuel pump50supplies fuel to fuel nozzles52located in the air intake manifold34. In other words, the fuel pump50is a piece of equipment in a fuel system of the engine E. In the instant embodiment, the fuel pump50and the electronically controlled throttle32are arranged aligned in the widthwise direction WD. Further, the fuel pump50and the electronically controlled throttle32are arranged substantially at the same position both in the vertical direction VD and in the longitudinal direction LD.

The fuel pump50is bolted to the engine body EB through a parts mounting plate69. The parts mounting plate69is configured with a bent metal sheet and bolted to the cylinder heads10. The parts mounting plate69extends in the widthwise direction WD and, for example, has a relay box, an ignition coil, and other components of the fuel pump50attached thereon.

Discussions on how the air cleaner26, the air intake pipe30, and the electronically controlled throttle32may be arranged and supported will follow.

Turning toFIG.1, the air cleaner26is detachably mounted to the air intake manifold34. In turn, the air intake manifold34is detachably mounted to the cylinder heads10(FIG.3). Accordingly, the air cleaner26is supported by the cylinder heads10(or the engine body EB) via the air intake manifold34.

More specifically, a bracket49is attached to the lower side of the air cleaner26, and the air cleaner26is bolted, through the bracket49, to threaded holes of bosses formed on the upper side of the air intake manifold34. However, this is only one of the non-limiting examples of how the air cleaner26may be mounted to the air intake manifold34.

Turning toFIG.2, the upstream air intake pipe30aextends forwards from the air cleaner26and in the widthwise direction WD of the engine E and is, then, curved downwards and extends onwards to connect to the inlet32aof the electronically controlled throttle32. The downstream air intake pipe30bextends downwards from the outlet32bof the electronically controlled throttle32and is, then, curved and extends rearwards to connect to the air intake manifold34. Accordingly, the electronically controlled throttle32is fitted with the air intake pipe30at a part of the air intake pipe30where it extends in the vertical.

The electronically controlled throttle32is arranged below the air cleaner26and above the cylinders8of the engine E. Further, as illustrated inFIG.3, the electronically controlled throttle32is arranged between the two cylinders or cylinder units6when viewed in the direction of extension of the axis AX of the crankshaft2. In the instant embodiment, the electronically controlled throttle32is arranged between the two cylinder units6,6in the widthwise direction WD when viewed in a plan view.

The control circuit board44is arranged to a side of the throttle body which faces away from the engine body EB. Also, the gearbox48is interposed between the engine body EB and the throttle body40. In the instant embodiment, the gearbox48, the throttle body40, and the control circuit board44are arranged in this order, from the engine body EB up to the front.

The motor46is arranged adjacently to the throttle body40in the widthwise direction WD. In the instant embodiment, the motor46is arranged to a side of the throttle body40which faces away from the fuel pump50in the widthwise direction WD. Hence, when viewed in the direction of extension of the axis AX of the crankshaft2, the control circuit board44, the motor46, and the gearbox48which form the electronic control unit38are arranged in a U shape configuration that is open in the widthwise direction WD. In other words, the control circuit board44and the gearbox48protrude in the widthwise direction WD on the same side relative to the motor46. In the instant embodiment, the electronic control unit38defines a cavity which is open in the widthwise direction WD towards the fuel pump50and in which the throttle body40is positioned. Moreover, a part of the control circuit board44protrudes in the widthwise direction WD relative to the motor46away from the throttle body40.

The control circuit board44has a planar shape that is substantially rectangular, and has a principal surface positioned to extend along the air intake passage IP defined inside the throttle body40. In the instant embodiment, the principal surface of the control circuit board44faces in the longitudinal direction LD. Accordingly, the throttle body40is arranged to the rear of the control circuit board44, whereas the front of the control circuit board44faces outwards of the engine.

The control circuit board44extends away from the fuel pump50which is a piece of equipment in the fuel system of the engine E. More specifically, the control circuit board44has a planar, rectangular shape and is arranged so as to define a longitudinal direction thereof oriented in the widthwise direction WD. In other words, the control circuit board44extends in a direction perpendicular to the axis AX1of the throttle body40. At the same time, the principal surface of the control circuit board44extends parallel to the axis AX2of the cleaner casing28(FIG.1). In regard to the widthwise direction WD, the control circuit board44hardly protrudes or does not protrude relative to the throttle body40towards the fuel pump50, but does protrude relative to the throttle body40away from the fuel pump50.

The control circuit board44is covered externally by a cover member54shown inFIG.5. In particular, the cover member54covers the front side of the control circuit board44. In the instant embodiment, the cover member54comprises a small cover made of resin with an external shape generally equivalent to that of the control circuit board44and a size slightly larger than that of the control circuit board44. It should be noted that the cover member54is omitted inFIGS.1to4.

As illustrated inFIG.6, the cover member54is detachably attached to the throttle body40using fasteners55such as bolts. These are merely some of the non-limiting examples of material, shape, and other qualities of the cover member54. For instance, a cover member54with a larger shape may be provided and attached to the parts mounting plate69to cover the front of the control circuit board44and fuel pump50together.

As illustrated inFIG.2, the control circuit board44has a side which faces towards the throttle body40—that is, a rear side of the control circuit board44-, and an electrical cable56is connected to the rear side of the control circuit board44. More specifically, the rear side of the control circuit board44is provided with a connector58to which the electrical cable56can be connected. As illustrated inFIG.3, the connector58is located on a part of the rear side of the control circuit board44which faces away from the fuel pump50. The electrical cable56extends in the widthwise direction WD of the engine on the front of the engine E so as to connect to a vehicle electrical system (not shown).

As discussed earlier with reference toFIG.2, the inlet32aof the electronically controlled throttle32is connected with the downstream end30abof the upstream air intake pipe30a, whereas the upstream end30aaof the upstream air intake pipe30ais connected with the air cleaner26which is supported on the air intake manifold34(FIG.3). Accordingly, the upper part of the electronically controlled throttle32is supported by the air intake manifold34through the upstream air intake pipe30awhich is formed of elastic material.

Further, the outlet32bof the electronically controlled throttle32connects to the upstream end30baof the downstream air intake pipe30b, and the downstream end30bbof the downstream air intake pipe30bconnects to the air intake manifold34. Accordingly, the lower part of the electronically controlled throttle32is supported by the air intake manifold34(FIG.3) through the lower air intake pipe30bwhich is formed of elastic material.

Moreover, the electronically controlled throttle32is mounted, at the rear side thereof, to the engine body EB through elastic elements60such as rubber. More specifically, the rear side of the throttle body40is attached to the parts mounting plate69on the engine body EB through the elastic elements60. Thus, the electronically controlled throttle32is mounted to the engine body EB through the elastic elements60and the air intake pipe30which is formed of elastic material. Accordingly, the electronically controlled throttle32is supported by the engine body EB in a rubber-mounted configuration which will be discussed in detail below.

The engine E in the instant embodiment includes a first coupling member61coupled to the inlet40aof the throttle body40and a second coupling member62coupled to the outlet40bof the throttle body40. As illustrated inFIG.5, the first coupling member61includes a cylindrical tubular section61aand a flange section61bformed on an end of the tubular section61aand having an external diameter greater than that of the tubular section61a. The flange section61bis detachably coupled to the inlet40aof the throttle body40by means of fasteners64such as bolts. The flange section61bin the instant embodiment has a rectangular, external shape when viewed in the axial direction.

Further, the tubular section61ais fitted with the upstream air intake pipe30aand is clamped thereto with a clamp element65such as a band, as shown inFIG.2. In this manner, the upstream air intake pipe30aconnects to the inlet40aof the throttle body40through the first coupling member61. As illustrated inFIG.5, the tubular section61aof the first coupling member61has a front side which is formed with a first cylindrical boss portion61ccreating a forward protrusion. The first boss portion61cdefines a hollow bore which is formed with a female threading61ca.

As illustrated inFIG.6, the second coupling member62also includes a cylindrical tubular section62aand a flange section62bformed on an end of the tubular section62aand having an external diameter greater than that of the tubular section62a. The flange section62bis detachably coupled to the outlet40bof the throttle body40by means of fasteners66such as bolts. The flange section62bin the instant embodiment has a rectangular, external shape when viewed in the axial direction. Further, the tubular section62ais fitted with the downstream air intake pipe30band is clamped thereto with a clamp element68such as a band, as shown inFIG.2. In this manner, the downstream air intake pipe30bconnects to the outlet40bof the throttle body40through the second coupling member62.

As illustrated inFIG.6, the flange section62bof the second coupling member62has a front side which is formed with a second cylindrical boss portion62ccreating a forward protrusion. The second boss portion62cdefines a hollow bore which is formed with a female threading62ca. In addition, as illustrated inFIG.5, the flange section62bof the second coupling member62has a rear side which is formed with a third cylindrical boss portion62dproviding a rearward protrusion. In the instant embodiment, the third boss portion62dcomprises two such portions arranged adjacently in the widthwise direction WD. The third boss portions62ddefine hollow bores which are formed with respective female threadings62da(FIG.6).

A bracket70produced from a metal sheet is attached to the third boss portions62dof the second coupling member62. More specifically, as illustrated inFIG.6, fasteners72such as bolts are inserted from the rear through first insertion holes70aformed in the bracket70and are screwed into the female threadings62daof the third boss portions62d. Alternatively, the bracket70may be produced from material other than a metal sheet.

The bracket70and the parts mounting plate69are coupled to each other through the elastic elements60. As illustrated inFIG.5, each of the elastic elements60in the instant embodiment comprises a cylindrical rubber element60awhich has axial opposite end sides provided with male threadings60b,60bprotruding therefrom. One of the male threadings60bis screwed from the front into a corresponding one of attachment holes69a(FIG.1) of the parts mounting plate69. Each of the attachment hole69acomprises a weld nut, for example. The other of the male threadings60bis inserted through a corresponding one of second insertion holes70bformed in the bracket70and is tightened with a nut74. As a result, the throttle body40is supported by the engine body EB through the bracket70, the elastic elements60, and the parts mounting plate69.

As illustrated inFIG.6, the cover member54is attached to the throttle body40through the first boss portion61cof the first coupling member61and the second boss portion62cof the second coupling member62. In particular, the cover member54has upper and lower end portions which are respectively formed with upper and lower insertion holes54a,54bthat are oriented in the longitudinal direction.

The fasteners55,55such as bolts are inserted from the front through the upper and lower insertion holes54a,54band screwed into the female threading61caof the first boss portion61cand the female threading62caof the second boss portion62c, respectively. As a result, the cover member54is attached to the throttle body40. The above is merely one of the non-limiting examples of how the cover member54may be mounted.

According to the configuration described so far, as illustrated inFIG.2, the control circuit board44is arranged to a side of the throttle body40which faces away from the engine body EB. Thus, a spacing can be secured between the engine body EB and the air intake passage IP for installing additional components. In this way, the space around the electronically controlled throttle32can be used more efficiently. Further, the extension of the principal surface of the control circuit board44is oriented in a direction perpendicular to the longitudinal direction LD along the throttle body40, thereby limiting the extent to which the control circuit board44sticks out forwards from the engine body EB. As a result, increase in the dimensions of the engine E can be prevented or otherwise mitigated.

In the instant embodiment, as illustrated inFIG.3, the gearbox48of the electronic control unit38is arranged so as to be interposed between the engine body EB and the throttle body40. According to this configuration, when viewed in a plan view, the control circuit board44, the motor46, and the gearbox48can be arranged in a U-shaped configuration in which these components are positioned in a conglomerated manner around the air intake passage IP.

In the instant embodiment, the control circuit board44has a rear side which faces towards the engine body EB and which is provided with the connector58to which the electrical cable56can be connected as shown inFIG.2. According to this configuration, it is possible to keep down the extent to which the electrical cable56sticks out from the engine body EB. As a result, increase in the dimensions of the engine E can be prevented or otherwise mitigated.

In the instant embodiment, the control circuit board44extends away from the fuel pump50in the widthwise direction WD. According to this configuration, it is possible to prevent space interference of the control circuit board44with the fuel pump50.

In the instant embodiment, the air intake pipe30which connects to the throttle body40as shown inFIG.2is formed of elastic material, and the throttle body40is detachably mounted to the engine body EB through the elastic elements60. The electronically controlled throttle32, which is an electronically assisted component with a considerable weight, is sensitive to vibrations. According to this configuration, the throttle body40is supported in a rubber-mounted configuration that can limit the transmission of vibrations from the engine E to the electronically controlled throttle32.

In the instant embodiment, as illustrated inFIG.5, the control circuit board44is covered externally by the cover member54. According to this configuration, the control circuit board44can be protected against obstacles and flying objects in the environment. Further, the cover member54is detachably attached to the throttle body40. According to this configuration, a small cover member54can be used to protect the control circuit board44, thereby limiting an increase in the weight of the engine E.

In the instant embodiment, as illustrated inFIG.2, the engine E is in the form of a vertical-shaft engine with a crankshaft2defining an axis AX which extends in the vertical direction and comprises an air cleaner26arranged at the upper part of the engine body EB. Further, the electronically controlled throttle32is arranged below the air cleaner26and above the cylinders8, and is fitted with the air intake pipe30at a part of the air intake pipe30where it extends in the vertical direction. According to this configuration, it is possible to prevent the control circuit board44from sticking out from the engine E in the horizontal direction.

The above described embodiments represent only some of the non-limiting configurations according to the present disclosure. Numerous additions, modifications, or omissions can be made therein without departing from the principle of the present disclosure. By way of example, while the previous embodiments have been described in connection with an example use of an engine air intake structure according to the present disclosure in a two-cylinder V engine, an engine air intake structure according to the present disclosure can also be used with engines other than two-cylinder V engines, including V engines with four or more cylinders and single-cylinder engines, for example. Moreover, an engine according to the present disclosure can be installed in any orientation in a work machine. Specifically, it can be installed in a work machine in such a way that the direction of opening of the V shape is oriented to the “side” by extending perpendicular or transverse to the direction of travel of the work machine. Hence, such variants are also encompassed within the scope of the present disclosure.