GB2081809A

GB2081809A - Direct Fuel Injection Internal Combustion Engine

Info

Publication number: GB2081809A
Application number: GB8026552A
Authority: GB
Original assignee: Yanmar Diesel Engine Co Ltd
Current assignee: Yanmar Co Ltd
Priority date: 1980-08-14
Filing date: 1980-08-14
Publication date: 1982-02-24
Also published as: GB2081809B

Abstract

The area of the two intake ports 2 and 3 is 1.1 to 1.7 times the area of the exhaust port 4 and the fuel injector receiving bore 11 has an axis inclined to and spaced from the cylinder axis 0 at the base of the cylinder head 1. Relationships between the diameters of the intake and exhaust ports and the cylinder are given in the specification. A water chamber 20 between the walls defining the intake and exhaust passages and the bore 11 receives water from the cylinder jacket through a drilled bore 23 and a further drilled bore (24), Figure 6 (not shown), extends through a wall 26 between the bore 11 and the exhaust passage (18) adjacent the base of the cylinder head. <IMAGE>

Description

SPECIFICATION Direct Fuel Injection Type Internal Combustion Engine The present invention relates to a direct injection type internal combustion engine, of either the petrol or diesel type.

A typical conventional two-valve type engine having a direct fuel injection system, i.e. an engine having one air intake port and one exhaust port disposed within the projected area of the cylinder head, is provided with an intake passage which is intended to generate a flow of air which swirls around the axis of the cylinder to make more effective use of the intake air. In this type of engine, the intake air encounters a larger flow resistance due to generation of the swirl than that encountered in ordinary internal combination engines so that the flow rate of the intake air is correspondingly reduced and the engine power output is limited in spite of the low fuel consumption characteristics.

Such engines also suffer from the problem that the fuel injection valve tends to get clogged as it is heated during engine operation. Furthermore, cracking is liable to occur in the portion of the cylinder head between the intake and exhaust ports or between these ports and the bore for receiving the fuel valve, due to thermal distortion of the surface of the cylinder head facing the combustion chamber.

According to the present invention there is provided a direct fuel injection type internal combustion engine having an exhaust port, two air intake ports and an fuel injection valve which are disposed in the cylinder head within the projected area of the cylinder and offset from the center of said area, the ratio of the combined areas of the intake ports to the area of the exhaust port being between 1.1 and 1.7.

With the invention, the flow rate of intake air is increased to give a higher engine power output, while preserving relatively small fuel consumption and the swirling of air in the suction stroke. The fuel injection valve in the engine is less likely to be clogged and cracking of the cylinder head surface is less likely.

Preferably, the engine includes a cooling jacket at a central portion of the cylinder head with said exhaust port, said intake ports and said injection valve being spaced therearound. The ratio of the total area of two intake ports to the area of the exhaust port is maintained at a suitable value, while preserving as large area as possible for these ports. The bore for receiving the fuel injection valve and the intake ports preferably have respective common walls, while the central cooling jacket portion between the fuel valve receiving bore and the exhaust and intake ports can be provided with a drilled water conduit for forcible water cooling of the cylinder head.

The invention will be more clearly understood from the following description which is given by way of example only with reference to the accompanying drawings in which: Fig. 1 is a partly sectioned plan view of a direct fuel injection type internal combustion engine in accordance with the present invention:: Fig. 2 is a sectional view taken along the line Il-Il of Fig. 1; Fig. 3 is a sectional view taken along the line Ill-Ill of Fig. 1; Fig. 4 is a schematic plan view showing the positional relationship of the ports such as intake ports in relation to the cylinder; Fig. 5 is a schematic sectional plan view of the cylinder head of an internal combustion engine in accordance with the present invention; Fig. 6 is a sectional view of another embodiment taken along the line VI--VI of Fig. 5; Fig. 7 is a vertical sectional view of another embodiment of the invention; and Fig. 8 is a schematic sectional plan view of the cylinder head in another embodiment of the invention.

As shown in Figs. 1 to 5, first intake port 2, a second intake port 3, an exhaust port 4 and an inclined fuel valve receiving bore 11 are formed in the portion of a cylinder head 1 within the projection area A of a cylinder 5. The axes 0,.

03,04 and 011 of the first intake port 2, second intake port 3, exhaust port 4 and the fuel valve receiving bore 11 are offset from the center 0 of the cylinder 5 so as not to overlap the latter, such that the lines connecting these axes 02,03,04 and 11 form a diamond. For a convenience's sake, the axis 0" of the fuel valve receiving bore 11 is shown as the center of the opening of that bore in the lower face of the cylinder head 1.

The fuel valve receiving port 11 is inclined toward the axis 0 of the cylinder 5, such that, when a fuel injection valve 9 is fitted to this bore, the rear end of the fuel injection valve 9 projects outwardly from the head cover 40. The angle of inclination preferably falls between 1 50 and 300.

A piston 7 has a recessed crown constituting a main combustion chamber 8, at an offset from the axis of the piston 7, i.e. from the axis 0 of the cylinder 5. The fuel valve receiving bore 11 is so located that the tip 10 of the fuel injection valve 9 is positioned substantially at the center of the main combustion chamber 8. The second intake port 3 is preferably located at the opposite side of the main combustion chamber 8 to the fuel valve receiving bore 11.

Since the fuel injection valve 9 projects at its rear end out of the head cover 40, the fuel injection valve 9 can be removed easily without necessitating the detaching of the head cover 40.

For the same reason, the connection of the highpressure fuel pipe and leak fuel pipe to the fuel injection valve 9 is facilitated considerably. Also, the protective maintenance or inspection of the fuel injection valve is very much facilitated.

By arranging the first intake port, second intake port, exhaust port and the fuel valve receiving bore in the form of a diamond as mentioned before, it becomes possible to form a cooling jacket 20 in the central portion of the cylinder head surrounded by the walls separating these ports, as shown in Figs. 2 and 5.

A first intake valve 1 2 and a second intake valve 1 3 are fitted to the first and the second intake ports 2 and 3 in such a manner as to avoid overlapping to a liner 1 7. Also, an exhaust valve 14 is attached to the exhaust port 4.

As will be seen from Figs. 1 and 5, the cylinder head 1 is provided with a branched intake passages 19, 1 9a. The intake passage 19 communicates with the first intake port 2. In order to generate a swirl, the angle a" formed between the axis X of the intake passage 1 9 and the-line X, interconnecting the axis 02 and the center 0 of the cylinder is selected to fall within the range of between 900 and 1400.

The intake passage 1 9a is in communication with the second intake port 3. In order to generate a swirl, the angle 2 formed between the axis Y and the line Y, interconnecting the axis 03 of the second intake port and the center 0 of the cylinder is selected to fall within the range of between 700 and 1000. In consequence, a socalled swirl is generated in the flow of air which comes into the cylinder 5 through these intake passages 1 9, 1 9a.

In the present invention, on the other hand, it is essential that a balance is obtained between the total area As (mm2) of the intake ports contributing to the increase of the intake air and the area AE (mm2) of the exhaust port in consideration of the exhaust resistance loss. More specifically, the ratio of the total area As to the area AE (As/AE) preferably ranges between 1.3 and 1.7. The total area As of the intake ports and the area AE of the exhaust port are determined, respectively, by the following equations.

=(0.13-O.18)Ap (2) where, Ap represents the area of the cylinder given by the following equation.

Symbols D,, D2, D3 and D4 represent, respectively, the diameters of the cylinder, first intake port, second intake port and the exhaust port. The diameter of the valve rod is represented by do.

The amount of offset or eccentricity 12 of the main combustion chamber 8 is determined in accordance with the following equation (4).

Also, the amount of the eccentricity 1, (mm) of the end 10 of the fuel injection valve from the cylinder center 0 is given by the following equation (5).

l2=(O.040. 1 O)DO (4) 1,=(0.05--0.1 5)Do (5) The angles 011,02, 03 and 04 involved by the diamond shape formed by the lines connecting the axes 02, 03, 04 and Oii of the first intake port, second intake port, exhaust port and the fuel valve receiving bore are preferably determined as follows.

011=1600+100 (6) 02=600+50 (7) 03=800+50 (8) 04=600+50 (9) Also, an exhaust passage 18 is formed in communication with the exhaust port 4, as shown in Fig. 5. Reference numerals 6, 1 5 and 35 denote, respectively, a cylinder block, valve seat and a bolt hole.

Fig. 7 shows a supercharged internal combustion engine embodying the present invention, in which a large overlap is preserved between the exhaust valve 14 and the liner 7 and the area A5 of the exhaust valve is increased in accordance with the following equation (10) to make the ratio As"AE fall between 1.1 and 1.6, whereby it is feasible to enhance the engine output and reduce the fuel consumption.

The liner 1 7 is provided at its top with a clearance recess 1 6 so as not to hinder the operation of the exhaust valve 1 4. The clearance recess 1 6 preferably has a radius R (mm) falling between 1.2 D4 and 1.7 D4.

Furthermore, for increasing the amount of the intake air, the diameter of the second intake port 3 is increased and a clearance recess is formed in ' the liner 7 so as not to obstruct the operation of the large-diameter intake valve associated with the intake port 3 of the increased diameter. It is remarkable that the aforementioned swirl is enhanced by the provision of this clearance recess.

In this case, the total area As of the first and the second intake ports is determined preferably in accordance with the following equation (1 1).

=(0.130.18)Ap (11) On the other hand, as will be seen from Fig. 5, a first drilled conduit 23 for introducing the cooling water forcibly from the outside of the cylinder head 1 is formed in the wall 25 between the second intake port 3 and the exhaust port 4, toward the jacket 20 formed at the center of the cylinder head 1 during casting of the latter.A second drilled conduit 24 is formed substantially at the center of a wall 26 of the cylinder head surrounded by the fuel valve receiving bore 11, exhaust passage 18 and the jacket 21, as shown in Fig. 6, apart from the jacket 21 between the fuel valve receiving bore 11 and the exhaust passage 1 8. This drilled conduit provides a communication between the peripheral jacket 22 and the central jacket 20 so as to prevent the overheating of the fuel valve by the heat which is transferred mainly from the wall of the exhaust port.

The outer end of the first drilled conduit 23 is closed by a plug 28, while a communication bore 29 is formed at an intermediate portion of the first drilled conduit 23 for communication with a jacket (not shown) of the cylinder block 6.

The fuel valve receiving bore 11 is separated at its other side from the first intake port 2 by a wall 27, so that the intake air flowing through the first intake port 2 carries away the heat from the wall 27.

The cooling water introduced into the first drilled conduit 23 from the communication port 29 flows in the direction indicated by an arrow W into the jacket 20 and is diffused after cooling the front side of the fuel valve receiving bore, into the jacket 22 through the water conduit 36 between the first and the second intake ports. A part of the water, however, flows into the jacket 22 through the second drilled conduit 24 and the jacket 21.

The heat transferred to the wall 25 between the second intake port 3 and the exhaust port 4 from the exhaust gas is carried away from the wall 25 by the cooling water flowing through the first drilled conduit 23. Further, the cooling water flowing through the second drilled conduit 24 carries the heat away from the wall 26 surrounded by the fuel valve receiving bore 11, exhaust passage 18 and the jacket 21, the heat having been transferred to the wall 26 from the exhaust gas.

In addition, since the fuel valve receiving bore 11 is connected to the first intake port 2 by means of the wall 27, the heat is carried away from the wall 27 by the intake air flowing through the first intake port 2.

Thus, the cylinder head 1 is effectively cooled by the cooling water flowing in the jackets 20, 21, 22 and through the drilled conduits 23, 24 as well as by the intake air flowing through the intake passages 1 9, 1 9a. In consequence, the cracking in the cylinder head surface confronting the cylinder chamber, attributable to the thermal distortion of the central region of the same, is fairly avoided to overcome the problem in the prior art. At the same time, the undesirable indirect heating of the fuel injection valve 9 fitted in the bore 11 by the exhaust gas is effectively prevented. Therefore, the problems of the prior art such as clogging or seizure of the fuel injection valve 9 due to overheating of the fuel injection valve 9 are overcome to ensure high output operation for longer period of time.

Insteadly of forming the second drilled port 24 in the wall 26 surrounded by the fuel valve receiving bore 11, exhaust passage 1 8 and the jacket 21, the bottom of the jacket 21 may be formed as a V-shaped recess reaching the position of the second drilled conduit 24.

Fig. 8 shows another embodiment of the invention which is characterized in that the fuel valve receiving bore 11 is formed between the first intake port 2 and the second intake port 3.

Namely, the fuel valve receiving bore 11 and the first intake port 2 has a common wall 31. Also, a wall 32 is formed commonly for both of the fuel valve receiving bore 11 and the second intake port 3, so as to enhance the cooling effect brought about by the intake air. At the same time, the jacket between the front wall 33 of the fuel valve receiving bore and the wall of the exhaust port is formed to have a sufficient marging so as to check the transfer of the heat. The cooling water flows through the first drilled conduit 23 formed in the wall 25 between the second intake port 3 and the exhaust port 4 to effectively cool the portion between the exhaust valve 4 and the second intake port. The first drilled bore 23 is formed to open toward the front wall 33 of the fuel valve receiving bore to positively cool the wall 33.The cooling water, after cooling the wail 33, flows through the conduit 30 between the first intake port 2 and the exhaust port 4 to positively cool the portion around the conduit 30 and comes into the peripheral jacket 22.

As has been described, according to the invention, there is provided direct fuel injection type internal combustion engine in which one exhaust port, two intake ports and one inclined fuel injection valve are provided in the portion of the cylinder head within the projection area of the cylinder at offsets from the center of the latter. A cooling jacket is formed at the central portion of the cylinder head surrounded by the exhaust port, intake ports and the fuel injection valve. At the same time, the ratio of the total area of the intake ports to the area of the exhaust port is maintained at a suitable value. The fuel valve receiving bore is connected to the intake ports by common walls.

Drilled bores or the like for the cooling water are formed between the fuel valve receiving port and the exhaust port, apart from the cooling jacket.

The present invention offers the following advantages. Namely, it is possible to obtain higher engine output thanks to the increased rate of supply of the intake air, while preserving the small fuel consumption characteristic and effective swirl of the intake mixture or air. In addition, various troubles in the conventional engines such as clogging of the fuel injection valve, seizure of the same, cracking in the cylinder head surface confronting the cylinder chamber and so forth are fairly avoided.

Claims

1. A direct fuel injection type internal combustion engine having an exhaust port, two air intake ports and an fuel injection valve which are disposed in the cylinder head within the projected area of the cylinder and offset from the center of said area, the ratio of the combined areas of the intake ports to the area of the exhaust port being between 1.1 and 1.7.

2. A direct fuel injection type internal combustion engine as claimed in claim 1, wherein the combined area of the intake ports is 13 to 1 8% of the cylinder cross section.

3. A direct fuel injection type internal combustion engine as claimed in claim 1 or 2, wherein the area of the exhaust port is 10 to 1 6% of the cylinder cross section.

4. A direct fuel injection type internal combustion engine as claimed in claim 1,2 or 3 including a cooling jacket at a central portion of the cylinder head with said exhaust port, said intake ports and said injection valve being spaced therearound.

5. A direct fuel injection type internal combustion engine as claimed in claim 1.2, 3 or 4, wherein there is a common wall between at least one of said two intake ports and the fuel valve receiving bore.

6. A direct fuel injection type internal combustion engine as claimed in any preceding claim, wherein the fuel valve receiving bore is formed between the two intake ports and respective common walls separate the bore from the two intake ports.

7. A direct fuel injection type internal combustion engine as claimed in any preceding claim, wherein a conduit for cooling water passes through the wall portion between one of said intake ports and said exhaust port and opens to a cooling jacket toward the front side of the wall surrounding said fuel valve receiving bore.

8. A direct fuel injection type internal combustion engine as claimed in any preceding claim, wherein a drilled conduit for cooling water is formed in the wall surrounded by said fuel valve receiving bore, exhaust passage and said cooling jacket.

9. A direct fuel injection type internal combustion engine as claimed in any preceding claim, wherein said fuel injection valve is inclined to the cylinder axis.

10. A direct fuel injection type internal combustion engine substantially as hereinbefore described with reference to and as iilustrated in the accompanying drawings.