Description

Multi-Inlet Air Flow Passage Arrangement for Diesel Engines

Technical Field The invention relates to diesel engines, and more particularly to the introduction of air into the cylinder bores through a plurality of inlet air pas¬ sages formed in the cylinder heads thereof.

Background Art It is known to use a plurality of air inlet valves with corresponding air inlet ports corαmunicating with the inlet air passages for each cylinder bore of diesel engines. In the past, such air inlet passages have been helically configured to produce a swirling flow path of air into the cylinder bores. Swirling flow ^' paths are shown in U.S. Patent 3,898,966 issued to List on August 12, 1975 and in U.S. Patent 3,884,209 issued to List et al on May 20, 1975. It has been found, however, that excessive swirl in such air flow path is detrimental during start up and cold idle be¬ cause it prolongs the time of "white smoke" operation of the engine and thus prolongs the period of objection¬ able hydrocarbon emissions. Further, it has been found that excessive amounts of swirl inevitably are produced at the expense of volumetric efficiency of the engine. Throttled inlet air' passages are known to be used for stratified charge versions of some engines such as the rotary piston engines, as shown in U.S. Patents 3,905,337 issued to Shimoji et al on September 16, 1975 and 3,901,198 issued to Yamamoto on August 26, 1975. At low engine speeds or low loads the air enters through a restricted tangential passage located in the cylinder housing. This gives high entry velocity

and makes stratified charge operation possible. At high engine speeds unrestricted passages in. the end housing are opened in order to get the needed volu¬ metric efficiency. Such operation would, however, be detrimental in a direct injection diesel engine since it is advantageous at low speeds and light loads to operate with a minimum of turbulence in the air being directed into the cylinder bores.

Disclosure of Invention The present invention is directed to over¬ coming one or more of the problems as set forth above. According to the present invention there is provided an improved multi-inlet air flow passage arrangement for engines having cylinder bores covered by cylinder heads. The arrangement comprises a swirϊ type entry passage introducing air flow to a first valve port which opens to. the cylinder bore in the engine block for directing such air flow through a path substantially tangent to the cylinder bore. A second non-swirl type entry duct passage serves to introduce air flow to a second valve port which opens to the same cylinder bore through an axially extending path.

In another aspect the invention comprises a method of controlling inlet air flow to the cylinder bore of a diesel engine to minimize emission on start up and cold idle operation while retaining high volu¬ metric engine efficiency throughout the full range of engine speeds. The method comprises introducing air into the cylinder bore through a non-swirling path generally toward or parallel to the axis of the cylinder bore during start up and cold idle engine operation and introducing air through a second path substantially tangent to the cylinder bore to cause

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swirling of- the air within the cylinder bore only when. t e _u engine is operating at other than start up and cold idle.

Other features and advantages will become apparent from the following specification taken in connection with the accompanying drawings.

Brief Description of Drawings

Figure 1 is a partial perspective view of a direct injection diesel engine with inlet air passages;

Figure 2 is a partially sectioned plan view of an air flow entry arrangement with a control and sensors shown schematically;

Figure 3 is a sectional view taken along line III-III of Figure 2;

Figure 4 is a sectional view taken along line IV-IV of Figure 2;

Figure 5 is a sectional view illustrating an alternate embodiment of the structure shown in Figure 4; and

Figure 6 is a fragmentary view illustrating an alternate embodiment for the entry passage shown in Figure 2.

Best Modes for Carrying out the Invention Figures 1 and 2 illustrate a diesel engine

10 which has one or more cylinder bores 12. An im¬ proved air flow entry arrangement 14, best seen in Figure 2, includes a swirl type entry passage 16 for introducing air flow to a first generally circular valve 18. The first valve 18 opens from a head 20 to the cylinder bore 12 and has its periphery 22 sub¬ stantially tangent to the cylinder bore 12 and its axis 24 substantially parallel to an axis 26 of the cylinder bore 12.. The ^* air flow is introduced from

the first valve 18 into the cylinder bore 12 sub¬ stantially tangent to the outer wall thereof.

A non-swirl type entry passage 28 introduces air flow to a second generally circular valve 30 which opens to the head 20 of the cylinder bore 12. The air flow from the second valve 30 is introduced to the cylinder bore 12 with substantially only axial and possibly radial velocity components, i.e., sub¬ stantially-parallel to or aimed at the axis 26. Thus, the air flow from the second valve 30 has primarily an axial as opposed to a tangential flow vector.

First throttle valve means, including a first butterfly valve 32 is provided for controlling the amount of air flow through the swirl type entry passage 16. Further, means are provided for closing the first butterfly valve 32 during start up and cold idle of the engine 10. In the embodiment illustrated in Figures 1 and 2 the first throttle valve closing means comprises a control 34 which senses engine tem- perature via a temperature sensor 36 and motivates the movement of a lever 38 which opens or closes the butterfly valve 32. The swirl type entry passage 16 does not provide air flow to the cylinder bore 12 on start up or during cold idle operation under the direction of the control 34. The control 34 can also sense engine speed as via an engine speed sensor 40 for a purpose which will later be apparent.

Second throttle valve means including a second butterfly valve 42 is preferably provided in the non-swirl type entry passage 28 for controlling the amount of air flow therethrough. Further, means are generally provided for closing the second butter¬ fly valve 42 at intermediate speeds of the engine 10. In the embodiment illustrated, the control 34 also includes means for closing the second butterfly valve

42. Said means can include a lever 44 motivated by the control 34. Movement of the lever 44 is controlled by the control 34 responsive to engine speed as sensed by the engine speed sensor 40 whereby the second butterfly valve 42 is closed at intermediate speeds of the engine 10. Thus, the non-swirl type entry passage 28 is generally open at start up and cold idle operation and at high engine speed operation, while being closed at intermediate engine speeds. In Figures 2 and 3, there is illustrated one preferred configuration of the swirl type entry passage 16. In this configuration a straight tube 46 has a generally circular or oval cross-section, and is angularly oriented relative to the first valve 18 so that a center line 48 of said tube 46 forms an an- gle A, in the range of about 30° to 50° with said valve axis 24. An inner wall 50 comprises that portion of the tube 46 nearest to the cylinder bore 12 and forms an angle, B, of at least about 40° with said valve axis 24. An outer wall 52 comprises that portion of said tube 46 farthest from the cylinder bore 12 and forms an angle, C, in the range of about 30° to 50° with said valve axis 24. The outer wall 52, if ex¬ tended in the direction of air flow, clears a seat 54 of said first valve 18. Preferably, the clearance of the valve seat 54 is related to the diameter, D, of the cylinder bore 12 whereby said clearance falls within a range from about 0.005D to about.0.015D. Preferably, the tube 46 has a length, L, from its intersection 56 with a plane defined by said valve seat 54 to an air entry end 58 thereof which falls within a range from about 0.5 to about 2.5 times a mean diameter, d, of said tube 46.

In the embodiment illustrated in Figure 6 the swirl type entry passage 16' has a first portion 60 extending away from the first valve 18" generally

parallel to the valve axis 24' and a second portion 62 generally perpendicular to the first portion 60 and extending away from the cylinder bore 12' . The pas¬ sage 16' has an outer generally lineraly extending wall 64 generally tangent to the cylinder bore 12* adjacent the first valve 18" and an inner wall 66 op¬ posite the outer wall 64. A section 68 of the inner wall 66 adjacent the first valve 18' has a concave surface 70 which faces the outer wall 64. In the embodiment illustrated, the concave surface 70 is formed by a vane 72 in a recess 74 in the section 68 of the inner wall 66. The vane 72 extends from a first end 76 adjacent the first valve 18' to a second end 78 spaced from the first valve 18'. A pin 80 pivotally mounts the second end 78 of the vane 72 in the recess 74. Preferably, the concave surface 70 corresponds to a surface of a cylinder which has an axis parallel to the axis of the cylinder bore 12' and has a radius of curvature which falls within a range from about 65% to about 35% of the radius of curvature of the cylinder bore.12'. A chord 82 drawn across the con¬ cave surface 70 aims substantially at the axis 24' of the first valve 18' so that a distance from said axis 24' to a nearest extension of the chord 82 is preferably no more than about 10% of the length of the diameter, D, of the cylinder bore 12'.

Figure 4 shows one embodiment of the non- swirl type entry passage 28. This passage has a curved tube 84 which bends the air path entering via the second valve 30 so that this air path enters gen¬ erally directly axially of the cylinder bore 12.

Figure 5 illustrates an alternate embodi¬ ment of the non-swirl type entry passage. In this embodiment, the non-swirl type entry passage 28' is similar to the structure illustrated in Figure 3 and as has been discussed above for the swirl type

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entry passage 16. To remain non-swirl, the entry duct 28' introduces the air through the straight tube 46' in a nontangential direction relative to the cyl¬ inder bore 12' and more particularly generally axially and somewhat radially into the cylinder bore 12*, e.g., in the position shown in Figure 5.

Method

In accordance with the method of the present invention air flow is controlled to a cylinder bore 12 of a direct injection diesel type engine 10 to minimize undesirable emission on start up and cold idle while retaining high volumetric engine efficiency at all operating speeds. A non-swirl air flow is introduced substantially parallel to or coplanar with the axis 26 of the cylinder bore 12 during start up and cold idle operation as via the second valve 30. A swirl air flow is introduced tangentially to the cyl¬ inder bore 12 as via the first valve 18 only when the engine 10 operates at other than start up and cold idle. In one embodiment introduction of the non-swirl air flow is stopped during intermediate speed operation of the engine 10 as by controlled operation of the second butterfly valve 42. In this embodiment intro¬ duction of the non-swirl air flow is preferably re- started during high speed operation of the engine 10 so that air is permitted to flow through both passages to provide optimum volumetric efficiency. This can be controlled by a control 34 operating responsive to engine speed as sensed by an engine speed sensor 40. Generally, the introducing, stopping and restarting of the non-swirl air flow comprises opening, closing and reopening of a non-swirl flow throttle valve, in the embodiment illustrated the second butterfly valve 42.

The introducing of the swirl air flow generally com¬ prises opening a swirl flow throttle valve, in the embodiment illustrated the first butterfly valve 32. The opening of the first butterfly valve 32 can be controlled, for example, through use of the control 34 operating responsive to a signal from the engine temperature sensor 36.

Through operating as just described above, engine efficiency is substantially improved and the previously mentioned problems of the prior art are substantially eliminated.

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