JPH08326511A - Direct injection type diesel engine - Google Patents

Abstract

PURPOSE: To miniaturize a direct injection type diesel engine and improve the reliablity of cam bearing parts. CONSTITUTION: Cam bearing parts 10A-10G are arranged in bore center corresponding positions after shifting pressure contact parts 18 onto the cylinder bore center part side from the longitudinal view of an engine 1 in relation to cam contact parts 17 in an intake locker arm 19 and an exhaust locker arm 16, and head bolt holes are arranged only in the positions out of the cylinder bores from the longitudinal view of the engine 1 so that the cylinder bore centerline lies in between, thus facilitating the arrangement of the cam bearings 10A-10G into the bore center corresponding positions. A cam shaft 6 can thereby be disposed as close as possible to the cylinder bore center part from the cross direction view of the engine 1, so that the cross direction dimension of the engine 1 becomes as small as possible. As a result, the engine 1 can be miniaturized in the cross direction, and the reliability of the cam bearing parts can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection diesel engine.

[0002]

2. Description of the Related Art Recently, in diesel engines,
Various measures have been taken in order to achieve both improvement of engine output and improvement of exhaust emission. For example, in a fuel supply system, a swirl chamber type diesel engine, which has been a mainstream for a relatively small engine such as an engine for a passenger car in the past, tends to shift to a direct injection type diesel engine in which fuel is directly injected into a combustion chamber. It is in. In addition, in the intake / exhaust system, the number of valves is increased (for example, two intake valves and two exhaust valves). Then, such a multi-valve diesel engine, for example, each cylinder is provided with two intake valves and two exhaust valves, and these valve actuations are driven by one cam shaft via corresponding rocker arms. In a diesel engine that has 2 cylinders,
It is customary to employ a so-called double rocker arm system, in which one intake valve is driven by one intake rocker arm, while two exhaust valves are driven by one exhaust rocker arm. (See, for example, JP-A 64-12009).

On the other hand, regarding the arrangement structure of the head bolts for fastening the cylinder block and the cylinder head, in a large-sized diesel engine which generally employs a direct injection type fuel injection mechanism, it is relatively difficult to seal a cylinder bore having a large bore diameter. In order to ensure high sealing performance, it is customary to employ a head bolt arrangement structure in which six head bolts are arranged around each cylinder, that is, a so-called six tightening structure. However, in a small diesel engine having a relatively small bore diameter, a head bolt arrangement structure in which four head bolts are arranged around each cylinder, that is, a so-called four-bolt structure is often adopted (for example, Japanese Patent Laid-Open No. 64
-12009). Further, in the diesel engine having such a head bolt arrangement structure of four tightening structure, as disclosed in the above-mentioned Japanese Patent Laid-Open No. 64-12009, the cam bearing portion that rotatably supports the cam shaft, It is customarily arranged at a position between adjacent cylinder bores (hereinafter, this position is referred to as "inter-cylinder bore position") when viewed in the longitudinal direction (front-back direction) of the engine, that is, the direction in which the axis of the cam shaft extends.

[0004]

However, while two intake valves are driven by one intake rocker arm in each cylinder, as disclosed in, for example, Japanese Patent Application Laid-Open No. 64-12009, there are two intake valves. One exhaust valve
In the conventional diesel engine driven by two exhaust rocker arms and the cam bearing portion is arranged at the position between the cylinder bores like the head bolt, the following problems occur.

First, since the cam bearing portion is arranged at the position between the cylinder bores, the cam bearing portion located at the front end portion of the engine, that is, driven by the engine output shaft, receives a tensile force from the engine output shaft side. In a cam bearing portion that supports the front end portion of a cam shaft to which a transmission member such as a drive pulley is attached in a cantilevered state, in addition to the tensile force from the engine output shaft side, the cam bearing portion is located at the frontmost side. A large reaction force is exerted on the camshaft side by each of the intake rocker arm and the exhaust rocker arm corresponding to the cylinder bore. Therefore, there arises a problem that the reliability of the cam bearing portion is lowered. In order to deal with this, it is necessary to increase the shaft diameter of the cam shaft or the bearing width of the cam bearing portion. However, this causes a problem that the compactness of the engine in the longitudinal direction is hindered. ..

Secondly, since the cam bearing portion is arranged at the position between the cylinder bores like the head bolt, when setting the position where the cam bearing portion should be arranged, in order to avoid interference with the head bolt, It is necessary to set the cam bearing portion to the outside of the position of the head bolt when seen in a direction perpendicular to the longitudinal direction (front-back direction) of the engine in a plan view, that is, in the width direction of the engine. For this reason, the camshaft is arranged at a position greatly separated from the cylinder bore as viewed in the width direction of the engine, and as a result, the compactness of the engine in the width direction is hindered.

Further, in the conventional direct injection type diesel engine, there is a problem that the tightening of the head bolt causes a stress on the water jacket wall around the valve operating mechanism, thereby lowering the durability of the wall.

The present invention has been made in order to solve the above-mentioned problems of the prior art. By devising the layout of various members around the valve operating mechanism, downsizing is promoted and the reliability of the cam bearing portion is improved. It is an object or an object to be solved to provide a direct injection type diesel engine with improved performance. Further, it is an object or object to be solved to provide a direct injection diesel engine in which the durability of the water jacket wall around the valve mechanism is sufficiently enhanced.

[0009]

The first basic aspect of the present invention, which has been made to solve the above-mentioned problems, has two cylinders for each cylinder.
One intake valve and two exhaust valves are provided. The two intake valves are a straight line passing through the center of each intake valve and a straight line passing through the center of each cylinder bore in plan view. The two exhaust valves are arranged in a staggered manner so as to intersect with a certain cylinder bore center line at a predetermined inclined angle. In a direct-injection diesel engine, which is arranged in a staggered manner so that the lines intersect with each other at a predetermined tilt angle, a pair of cylinder bores are inserted only at positions deviated from the cylinder bores when viewed in the direction in which the cylinder bores extend. Head bolt holes are provided so that four head bolt holes are arranged around each cylinder bore, and viewed in a plane perpendicular to the cylinder bore center line. The other party of one of the peripheral portion of the cylinder bore, one of the cam shaft driven rotation is arranged by the engine output shaft extends in the extending direction of the cylinder bore center line,
A cam bearing portion that rotatably supports the cam shaft is provided at a position corresponding to the center portion of the cylinder bore as viewed in the direction in which the center line of the cylinder bore extends. One intake rocker arm that is dynamically driven is opened and closed, while two exhaust valves are opened and closed by one exhaust rocker arm that is swingably driven by an exhaust cam provided on the cam shaft. It is characterized by that. Here, in the above-mentioned "position deviated from the cylinder bore", when viewed in the direction in which the center line of the cylinder bore extends, that is, in the front-back direction of the engine, a position slightly front side of the cylinder bore located on the most front side,
The positions between the cylinder bores and the positions on the slightly rear side of the cylinder bore located on the rearmost side are included. Further, the above “direction perpendicular to the cylinder bore center line in plan view” means the width direction of the engine.

In the direct injection type diesel engine according to the first basic mode, basically, the cam bearing portion is
It is located at a position that corresponds to the center of the cylinder bore (hereinafter, this position is referred to as the "bore center corresponding position") when viewed in the direction in which the cylinder bore centerline extends, that is, in the longitudinal direction of the engine (front-back direction), while the head bolt hole is displaced from the cylinder bore. Are placed in the same position. Therefore, the cam bearing portion and the head bolt screwed into the head bolt hole do not interfere with each other in layout. Therefore, the cam shaft can be arranged closer to the center of the cylinder bore when viewed in the width direction of the engine, and as a result, the engine can be made compact in the width direction.

In the direct injection diesel engine according to the first basic mode, the intake rocker arm is located at an intermediate position between the contact portion that contacts the intake cam and the center portions of the two intake valves in plan view. And a pressing portion that presses the two intake valves at the same timing, while an exhaust rocker arm has an abutting portion that abuts on the exhaust cam, and a two-dimensional view.
And a pressing portion that presses the two exhaust valves at the same timing and is located at an intermediate position between the center portions of the two exhaust valves. At least one of the rocker arms has a cylinder bore center line extending direction. In view of this, it is preferable that the pressing portion is displaced from the contact portion toward the center of the cylinder bore. Specifically, the pressing portion may be deviated from the contact portion only in the intake rocker arm. Also,
In both the intake rocker arm and the exhaust rocker arm, the pressing portion may be deviated toward the center of the cylinder bore with respect to the abutting portion. In this case, the deviation amount of the intake rocker arm is the exhaust rocker arm. It is preferable that the deviation amount is larger than the deviation amount.

Generally, two cylinder bores are provided for each cylinder bore.
One intake valve and two exhaust valves are arranged, and both intake valves are 1
In a direct-injection diesel engine having a basic configuration in which opening / closing is driven by a cam shaft via one intake rocker arm, and both exhaust valves are opened / closed by the cam shaft via one exhaust rocker arm, both intake valves and both intake valves When the exhaust valves are arranged in a staggered manner, compared with the case where both intake valves and both exhaust valves are arranged side by side in the direction orthogonal to the axis of the camshaft, the center of both intake valves is intermediate. The push contact portion of the intake rocker arm corresponding to the position and the push contact portion of the exhaust rocker arm corresponding to the intermediate position between the center portions of both the exhaust valves are deviated to the cylinder bore center side in the longitudinal direction of the engine. It becomes a state. Therefore, when each rocker arm has a shape extending in a direction perpendicular to the axial direction of the cam shaft in a plan view, that is, a straight line connecting the pressing portion and the abutting portion extends in a direction perpendicular to the axial direction of the cam shaft. In the case of the shape, the contact portions of both rocker arms are close to each other in the axial direction of the cam shaft, and it becomes difficult to dispose the cam bearing portion at a position between them, that is, a position corresponding to the bore center. Even if the cam bearing portion is intentionally arranged at the position corresponding to the bore center in spite of such difficulty, interference between the head bolt hole and the cam bearing portion will occur if the head bolt arrangement structure is a six-bolt structure. In order to avoid the above, it is necessary to separate the cam bearing portion largely in the direction opposite to the center side of the cylinder bore when viewed in the width direction of the engine.

However, according to these direct-injection diesel engines of the present invention, at least one of the intake rocker arm and the exhaust rocker arm has the pressing contact portion with respect to the contact portion in the axial direction of the cam shaft. Since it is deviated to the bore center side, even if the distance between the pressing portions of both rocker arms is narrow, the distance between the contact portions is wide. Therefore, it becomes extremely easy to dispose the cam bearing portion between the two contact portions, that is, at the position corresponding to the bore center.

Further, as described above, when the cam bearing portion is arranged at the position between the cylinder bores, mutual interference between the cam bearing portion and the head bolt hole occurs. However, in the direct injection type diesel engine according to the present invention, Since the bolt holes are located only off the cylinder bore when viewed in the axial direction of the camshaft, that is, slightly forward of the frontmost cylinder bore, between cylinder bores, or slightly rearward of the rearmost cylinder bore, the camshaft There is no head bolt hole at a position corresponding to the center of the cylinder bore when viewed in the axial direction of. Therefore, it is possible to dispose the cam bearing portion as close to the cylinder bore as possible in the width direction of the engine, in other words, to dispose the cam shaft as close to the center portion of the cylinder bore as possible.

That is, according to the direct injection type diesel engine of the present invention, the two intake valves and the two exhaust valves are arranged in a staggered manner, so that when viewed in the longitudinal direction of the engine, the pressing contact portion of the intake rocker arm is provided. Although the pressing contact part of the exhaust rocker arm is close to the center of the cylinder bore, the pressing contact part of each rocker arm is deviated to the center of the cylinder bore with respect to the contact part. The contact portion and the contact portion of the exhaust rocker arm are arranged at a position relatively distant from the bore center corresponding position, and the cam bearing portion can be easily arranged at the bore center corresponding position. Thus, by disposing the cam bearing portion at the position corresponding to the bore center, the cam shaft can be brought as close to the center portion of the cylinder bore as possible, so that the widthwise dimension of the engine can be made as small as possible. The engine can be made compact in the width direction of the engine.

In each direct-injection diesel engine according to the first basic aspect of the present invention or the modification thereof, the rocker shaft that swingably supports the intake rocker arm and the exhaust rocker arm has the cylinder bore center line in plan view. It is arranged so as to extend parallel to the cam shaft at a position closer to the center of the cylinder bore than the cam shaft when viewed in a direction perpendicular to the extending direction, and the cam shaft is arranged at a position lower than the rocker shaft. preferable. In this case, the cam shaft is arranged below the intake rocker arm or the exhaust rocker arm. That is, the intake cam or the exhaust cam provided on the cam shaft comes into contact with the lower surface of the intake rocker arm or the exhaust rocker arm, respectively. With this configuration, the height of the engine is suppressed, and the vertical size of the engine is reduced.

In each direct-injection diesel engine according to the first basic aspect of the present invention or its modification, it is preferable that the cam bearing portion has a cam cap that is fastened and fixed to the cylinder head. This makes it easy to attach or detach the cam shaft to or from the cylinder head.

In the direct injection diesel engine according to the first basic aspect of the present invention or its modification, the rocker arm of the intake rocker arm and the exhaust rocker arm, which has the smaller deviation amount from the contact portion of the pressing portion, is used. The arm length of the rocker arm is preferably shorter than the arm length of the other rocker arm. By doing so, the arm length of the rocker arm having a larger deviation amount with respect to the contact portion of the pressing portion becomes longer, and the tilt of the rocker arm with respect to the direction perpendicular to the cylinder bore center line in plan view or the bending of the rocker arm. Is prevented from becoming too large, and the strength or durability of the rocker arm is enhanced.

Further, in the direct injection diesel engine according to the first basic aspect of the present invention or its modification,
It is preferable that the valve diameter of the intake valve is set larger than the valve diameter of the exhaust valve, and the lever ratio of the intake rocker arm is set larger than the lever ratio of the exhaust rocker arm. In this case, the arm length of the intake rocker arm is preferably longer than the arm length of the exhaust rocker arm. By doing so, the passage cross-sectional area of the intake port opened and closed by the intake valve is increased, the amount of air supplied to the combustion chamber is increased, and the engine output is increased.

The second basic aspect of the present invention is to provide two cylinders for each cylinder.
One intake valve and two exhaust valves are provided. The two intake valves are a straight line passing through the center of each intake valve and a straight line passing through the center of each cylinder bore in plan view. The two exhaust valves are arranged in a staggered manner so as to intersect with a certain cylinder bore center line at a predetermined inclined angle, while the two exhaust valves are a straight line passing through the center parts of both exhaust valves in plan view, and the cylinder bore center line. In a direct-injection diesel engine that is arranged in a staggered manner so that the line intersects at a predetermined inclined angle, when viewed in a direction perpendicular to the cylinder bore center line in plan view, ahead of one peripheral edge of the cylinder bore, the cylinder bore center line One cam shaft extending in the extending direction is arranged, and a transmission body drivingly connected to the engine output shaft via a winding transmission member is disposed at the front end portion of the cam shaft, and the center line of the cylinder bore extends. A cam bearing portion that rotatably supports the cam shaft is arranged at a position corresponding to the center of the cylinder bore when viewed in the direction, and two intake valves are oscillated by an intake cam provided on the cam shaft. While being opened and closed by one intake rocker arm, two exhaust valves are opened and closed by one exhaust rocker arm that is rockingly driven by the exhaust cam provided on the cam shaft, and rocks the intake rocker arm and the exhaust rocker arm. The rocker shaft that is supported so as to extend is arranged so as to be parallel to the cam shaft at a position closer to the center of the cylinder bore than the cam shaft when viewed in a direction perpendicular to the direction in which the center line of the cylinder bore extends in plan view. Of the intake rocker arm and the exhaust rocker arm corresponding to the cylinder bore located at, the lever ratio of the rocker arm located on the front side is the rear side. And it is characterized in that it is set smaller than the lever ratio of the rocker arm located.

Generally, two intake valves and two exhaust valves are arranged in each cylinder, and both intake valves are opened and closed by a cam shaft through one intake rocker arm, and both exhaust valves are used for one exhaust valve. A direct-injection diesel engine having a basic structure in which a transmission body drivingly connected to an engine output shaft via a winding transmission member is provided at the front end of the cam shaft while being opened and closed by the cam shaft via a rocker arm. The engine has the following features. That is, first, in the intake rocker arm and the exhaust rocker arm, when viewed in a plan view in a direction perpendicular to the axial direction of the cam shaft, the length between the push contact and the swing fulcrum, and the contact point and the swing rocker arm. Lever ratios defined by the ratio of lengths between fulcrums are different. here,
The push contact of the intake rocker arm is located at an intermediate position between both centers of both intake valves in a plan view, and the push contact of the exhaust rocker arm is located at an intermediate position between both centers of both exhaust valves in a plan view.
Secondly, since the transmission body drivingly coupled to the engine output shaft via the winding transmission member is arranged at the front end portion of the cam shaft, the transmission body is provided at the cam bearing portion located at the front end portion of the engine. A tensile force acts from the engine output shaft side via the, and the load condition of the cam bearing portion becomes more severe than that of the other cam bearing portions.

Thus, in the direct injection diesel engine according to the second basic aspect of the present invention, basically, the cam bearing portion is arranged at the position corresponding to the bore center, and
Among the intake rocker arm and the exhaust rocker arm corresponding to the frontmost cylinder bore, the lever ratio of the front rocker arm is set smaller than the lever ratio of the rear rocker arm. According to this structure, the rocker arm located on the front side of the cylinder bore located on the most front side is located on the front side with respect to the cam bearing portion arranged at the bore center corresponding position with respect to the cylinder bore, so that it is based on the reaction force of the rocker arm. The load acts on the cam bearing portion located at the front end of the engine. However, since the rocker arm located on the rear side of the cylinder bore is located on the rear side of the cam bearing portion arranged at the position corresponding to the bore center with respect to the cylinder bore, the load based on the reaction force of the rocker arm is placed on the front end portion of the engine. It has no effect on the cam bearings located. Further, since the lever ratio of the rocker arm located on the front side is relatively small (at least smaller than the lever ratio of the rocker arm located on the rear side), the load based on the reaction force of the rocker arm located on the front side is relatively small. Moreover, the load based on the reaction force of the rocker arm located on the front side is shared and received by the cam bearing portion located at the front end of the engine and the second cam bearing portion from the front. Therefore, the load acting on the cam bearing portion located at the front end portion of the engine based on the reaction force of the rocker arm located on the front side becomes very small.

That is, the total load applied to the cam bearing portion located at the front end of the engine is the load from the transmission side and the anti-locking force of the rocker arm having the smaller lever ratio of the two rocker arms corresponding to the frontmost cylinder bore. It is only part of the load based on force (burden part). On the other hand, for example, in a conventional direct injection diesel engine in which the cam bearing is arranged at the position between the cylinder bores, the cam bearing located at the front end of the engine has a load from the transmission body and the cylinder bore located at the most front side. And a part of the load based on the reaction force of both rocker arms (the part that bears between the second cam bearing part from the front) acts. Therefore, in this direct injection diesel engine according to the present invention, the load acting on the cam bearing portion located at the front end portion of the engine becomes smaller than that of the conventional direct injection diesel engine, and the cam bearing located at the front end portion of the engine is correspondingly reduced. The reliability of the portion can be improved, and the diameter or width of the cam bearing portion can be reduced, so that the cam bearing portion can be made compact and the diesel engine can be made compact.

The third basic aspect of the present invention is the first aspect of the present invention.
In the direct-injection diesel engine according to the basic mode of 1., the intake rocker arm is located at an intermediate position between the cam contact portion that contacts the intake cam and both central portions of the two intake valves in plan view. The exhaust rocker arm is located at an intermediate position between the cam contact portion that contacts the exhaust cam and the center portions of the two exhaust valves in plan view, while the press contact portion that presses the valve at the same timing is provided. And a pressing portion that presses the two exhaust valves at the same timing. In at least one of both rocker arms, the pressing portion has a center of the cylinder bore with respect to the contact portion when viewed in the direction in which the center line of the cylinder bore extends. The rocker shaft, which is biased toward the side of the cylinder, supports the intake rocker arm and the exhaust rocker arm in a swingable manner. The cam bearing has a cam cap that is fastened and fixed to the cylinder head, and is arranged to extend so as to be parallel to the cam shaft at a position near the center of the double bore, and corresponds to the frontmost cylinder bore. Among the intake rocker arm and the exhaust rocker arm, the lever ratio of the rocker arm located on the front side is set to be smaller than the lever ratio of the rocker arm located on the rear side.

In the direct injection diesel engine according to the third basic aspect of the present invention, in addition to the actions and effects obtained by the direct injection diesel engine according to the first basic aspect, the following unique action effects are obtained. To be That is, basically, the cam bearing is arranged at the position corresponding to the bore center, and of the intake rocker arm and the exhaust rocker arm corresponding to the frontmost cylinder bore, the lever ratio of the rocker arm located on the front side is set to the rear side. Since it is set smaller than the lever ratio of the rocker arm located,
Compared with the conventional direct injection diesel engine in which the cam bearing is located between the cylinder bores, the load applied to the cam bearing located at the engine front end is smaller, and the cam bearing located at the engine front end is correspondingly smaller. It is made compact, and thus the engine is made compact. Further, since the cam bearing portion is fastened and fixed to the cylinder head by using the cam cap, the cam shaft can be easily attached to or removed from the cylinder head. The first aspect of the present invention
As in the case of the direct injection diesel engine according to the modified example of the basic mode, since the push contact is displaced toward the center of the cylinder bore with respect to the contact point, it is easy to dispose the cam bearing at the position corresponding to the bore center. Becomes

In the direct injection diesel engine according to the second or third basic aspect of the present invention, it is preferable that the lever ratio of the exhaust rocker arm is set smaller than the lever ratio of the intake rocker arm. By doing so, in addition to the actions and effects of the direct injection diesel engine according to the second or third basic mode, the following unique actions and effects are obtained. That is, in general, in an engine, the diameter of the intake port is set to be larger than the diameter of the exhaust valve in order to improve the intake charging efficiency.
As a result, the diameter of the intake valve is inevitably larger than the diameter of the exhaust valve, and the driving force of the valve is also larger in the intake valve than in the exhaust valve. Therefore, of the exhaust rocker arm and the intake rocker arm provided for each cylinder bore, the lever ratio of the exhaust rocker arm corresponding to the exhaust valve with the smaller valve driving force is set to the intake rocker arm with the larger valve driving force. By making it smaller than the lever ratio and arranging this exhaust rocker arm in front of the cam bearing located at the bore center corresponding position, the load on the cam bearing located at the front end of the engine can be further reduced. Will be. Thus, in this direct-injection diesel engine, the cam bearing portion located at the front end portion of the engine is further enhanced in reliability and the compactness of the engine is further promoted by the above configuration.

In each of the above direct injection diesel engines according to the present invention, when the cam bearing portion has a cam cap that is fastened and fixed to the cylinder head, the rocker shaft is fixed by a bolt that fastens the cam cap. While being fixed together with the cam cap by tightening together, the head bolt hole of the head bolt hole, which is arranged on the cam shaft side of the cylinder bore center line, is arranged at a position where it overlaps with the rocker shaft in plan view. preferable.

By doing so, the following unique actions and effects can be obtained. That is, according to the above configuration, the rocker shaft can be brought closer to the bore center side regardless of the presence of the head bolt hole. Further, when the rocker shaft is attached to the cylinder head by using a mounting member different from the cam cap, the cam cap and the mounting member are arranged apart from each other in the width direction of the engine to avoid mutual interference. There is a need. However, in this direct-injection diesel engine according to the present invention, the rocker shaft is fixed together with the cam cap by the bolt for fastening the cam cap, so that the above-mentioned inconvenience does not occur. The rocker shaft and the cam shaft can be brought closer to the center of the cylinder bore. Due to these synergistic effects, size reduction of the engine in the width direction is further promoted.

Further, in each of the above direct injection diesel engines according to the present invention, the front end portion of the rocker shaft extends in the direction in which the cylinder bore center line extends with respect to the support portion provided in the cam bearing portion located at the engine front end. It is preferably fitted and fixed.

In this way, the following unique actions and effects can be obtained. That is, since the front end of the rocker shaft is fitted and fixed in the axial direction of the rocker shaft with respect to the support portion provided in the cam bearing located at the front end of the engine, for example, the front end of the rocker shaft is bolted. As compared with the case where the rocker shaft is fixed to the cylinder head by the above, the structure is simplified, and the workability when mounting or removing the rocker shaft is improved. Further, for example, when the head bolt is arranged near the front end of the rocker shaft, if the front end of the rocker shaft is fastened to the cylinder head with a bolt, interference between the bolt and the head bolt is avoided. Therefore, it is necessary to shift the position of the cam bearing portion located at the front end portion of the engine forward to secure a space for arranging the bolts, and as a result, the size of the engine in the longitudinal direction increases. However, as in the direct injection diesel engine according to the present invention, if the front end of the rocker shaft is fitted and fixed to the support portion provided in the cam bearing portion located at the engine front end, such a bolt can be arranged. It is not necessary to secure the space of. Therefore, the cam bearing portion located at the front end portion of the engine can be brought close to the cylinder bore located at the frontmost side, and the engine can be made compact in the longitudinal direction by that amount.

A fourth basic aspect of the present invention is a direct injection diesel engine according to the above-mentioned basic aspect of the present invention or a modification thereof, in which four cylinders are arranged around each cylinder bore.
Square 1 with each head bolt hole centering at the top
On one diagonal line, an opening portion of one intake port to the combustion chamber and an opening portion of one exhaust port to the combustion chamber are arranged, and the exhaust port is located on the diagonal line and faces the exhaust port. A rib protruding from the bottom wall of the water jacket into the water jacket is provided between the head bolt hole and the bolt boss portion. In this direct-injection diesel engine, the wall of the intake port is joined to the upper wall of the water jacket on the upstream side in the intake flow direction, while there is a space between the wall of the exhaust port and the upper wall of the water jacket. It is preferably formed.

Generally, in a direct injection diesel engine, since the wall of the intake port is connected to the upper wall of the water jacket on the upstream side in the intake flow direction on the intake port side, the rigidity of the water jacket wall around the intake port is compared. High On the other hand, on the exhaust port side, since a space is formed between the wall of the exhaust port and the upper wall of the water jacket, the rigidity of the water jacket wall around the exhaust port is relatively low. Therefore, in these direct injection diesel engines according to the present invention,
Ribs are provided on the exhaust port side to increase the rigidity of the water jacket wall around the exhaust port, thereby improving the sealing performance of the cylinder bore on the exhaust port side.

On the other hand, on the intake port side, the fastening force of the head bolt causes tensile stress in the water jacket wall around the intake port, and this tensile stress may cause cracks in the water jacket wall around the intake port. is there. Therefore, in order to relieve the tensile stress applied on the intake port side, it is better not to increase the rigidity of the water jacket wall around the intake port too much. Therefore, in this direct injection type diesel engine according to the present invention, no rib is provided on the intake port side. On the other hand, on the exhaust port side, the fastening force of the head bolt causes compressive stress in the water jacket wall around the exhaust port. Since this compressive stress rather acts to suppress the generation of cracks, even if ribs are provided on the exhaust port side to increase the rigidity thereof, the generation of cracks in the water jacket wall is not promoted.

Further, in each direct injection type diesel engine according to the present invention, a cross drill hole extending from the exhaust side side portion of the cylinder head toward the intake port inward of the cylinder head and supplying / discharging cooling water to / from the water jacket is provided. It is preferably provided. More preferably, such a cross drill hole is provided only on the exhaust side of the cylinder head. With this configuration, the cross drill does not have to be provided with a rib projecting into the water jacket between the intake port and the bolt boss portion of the head bolt hole located on the diagonal line and facing the intake port. The peripheral wall of the hole reinforces the water jacket wall around the intake port. Further, when the cross drill hole is provided only on the exhaust side of the cylinder head, the sub-chamber type (vortex chamber type) diesel engine and the cylinder block can be shared.

A fifth basic aspect of the present invention is the direct injection diesel engine according to the basic aspect of the present invention or a modification thereof, in which a fuel injection nozzle is arranged in the center of the cylinder bore in plan view, and the fuel injection nozzle is provided. The nozzle pressing member for fixing the fuel injection nozzle is arranged between the intake valve shaft and the exhaust valve shaft at a position opposite to the cam shaft with respect to the fuel injection nozzle. In this direct injection type diesel engine, it is preferable that the inlet pipe for supplying fuel to the fuel injection nozzle is arranged above the nozzle pressing member, and in this case, the direction in which the nozzle pressing member extends in plan view and the inlet pipe It is more preferable that the direction of extension is deviated. Further, it is preferable that the inlet pipe extends near the fuel injection nozzle in a direction perpendicular to the extending direction of the cylinder bore center line.

In these direct injection diesel engines, the nozzle pressing member can be easily arranged. That is, the fuel injection nozzle is arranged near the center of the cylinder bore in plan view, and the nozzle pressing member is arranged relatively close to the fuel injection nozzle. Thus, in the direct injection diesel engine according to the present invention, the cam bearing portion is arranged at the position corresponding to the bore center, so that the layout is very difficult when the nozzle pressing member is arranged on the cam shaft side. However, since the nozzle pressing member is arranged on the side opposite to the cam shaft in this way, the layout of the nozzle pressing member becomes extremely easy. Also, when the inlet pipe is arranged above the nozzle pressing member,
Since the nozzle pressing member does not interfere with the inlet pipe, the layout of the nozzle pressing member becomes easier. The layout of the nozzle pressing member becomes even easier when the extending direction of the nozzle pressing member and the extending direction of the inlet pipe are misaligned, or when the inlet pipe extends in the width direction of the engine near the fuel injection nozzle. .

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A direct injection diesel engine according to the present invention will be specifically described below with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, a four-cylinder direct injection diesel engine 1 for an automobile (hereinafter, simply referred to as "engine 1") according to an embodiment of the present invention includes a cylinder block 2 and A cylinder head 3 attached to the upper side of the cylinder block 2 and a head cover 4 (see FIG. 3) attached to the upper side of the cylinder head 3 are provided. In the following, for convenience, the cylinder arrangement direction, that is, the direction in which the cylinder bore center line, which is a straight line passing through the center of each cylinder bore in plan view, extends, that is, the direction in which the axis of the engine output shaft extends (left and right in FIG. 1).
Is referred to as “engine longitudinal direction”, and a direction perpendicular to the engine longitudinal direction in plan view is referred to as “engine width direction”. Further, when viewed in the longitudinal direction of the engine, the belt pulley 41
The side on which is arranged (left side in FIG. 1) is called "front", and the opposite side is called "rear". further,
The side on which the camshaft 6 is arranged as viewed in the engine width direction is called "right", and the opposite side is called "left".

The engine 1 is a so-called SOHC (single over head cam) type multi-valve direct injection diesel engine, and is located at a position deviated to the left of the center of the cylinder head 3 in the engine width direction. The four cylinders 5A to 5D are arranged in a row at a predetermined interval in the longitudinal direction of the cylinder head 3, that is, the engine longitudinal direction (engine front-rear direction), while the cam is located at a position offset to the right. The shaft 6 is arranged such that its axis is oriented in the longitudinal direction of the engine, that is, parallel to the cylinder bore center line. The engine 1 has a head bolt arrangement structure of four tightening structure, and surrounds each of the cylinders 5A to 5D in a square shape, and the head bolts 2 are respectively arranged at positions between the cylinder bores.
5 are arranged.

Further, each cylinder 5A of the cylinder head 3
The fuel injection valve 26 (fuel injection nozzle) has its injection hole facing the combustion chamber, and its axis extends in the direction (vertical direction) of the cylinder axis at positions corresponding to the center of the cylinder bore of 5D. They are arranged so that they face each other. In each of the cylinders 5A to 5D, two exhaust ports 33 and two intake ports 34 are open to the combustion chamber 13 around the fuel injection valve 26. Each exhaust port 33 is provided with an exhaust valve 35, while each intake port 34 is provided with an intake valve 36 having a larger valve diameter than the exhaust valve 35. The exhaust valves 35 and the intake valves 36 are cammed via the exhaust rocker arm 16 and the intake rocker arm 19 which are attached to the rocker shaft 15 at predetermined positions corresponding to the cylinders 5A to 5D. Axis 6
It is designed to be opened and closed by the. Here, the rocker shaft 15 is seen in the engine width direction and each cylinder 5A to 5D.
It is arranged so as to be parallel to the cam shaft 6 at an intermediate position between the center of the cylinder bore and the cam shaft 6.

The positional relationship between each exhaust valve 35 and each intake valve 36 in the cylinder bore will be described below. The two exhaust valves 35 are located in front of the center of the cylinder bore in the engine longitudinal direction (cylinder arrangement direction). The two exhaust valves 35 are arranged such that the straight line connecting the centers of the two exhaust valves 35 has a predetermined inclination angle with respect to the cylinder bore center line.
They are arranged side by side diagonally. On the other hand, the two intake valves 36
Is located behind the center of the cylinder bore in the longitudinal direction of the engine. The intake valves 36 are arranged obliquely so that the straight line connecting the centers of the intake valves 36 has a predetermined inclination angle with respect to the cylinder bore center line. Here, the exhaust valve 35 and the intake valve 36, which are arranged so as to sandwich the center of the cylinder bore as viewed in the longitudinal direction of the engine, rotate clockwise by a predetermined angle about the center of the cylinder bore in plan view. It is located in the position Therefore, the exhaust valves 35 and the intake valves 36 are staggered in the engine longitudinal direction (cylinder arrangement direction).

As described above, since the two exhaust valves 35 and the two intake valves 36 are arranged in a staggered manner, the intermediate positions of the two exhaust valves 35 (the pressing portion 18 of the exhaust rocker arm 16 described later) are arranged.
The position corresponding to (1) is closer to the cam shaft 6 than the center of the cylinder bore (a position separated from the axis of the rocker shaft 15 by a distance R ₁ ). On the other hand, an intermediate position of both intake valves 36 (a position corresponding to the press contact portion 21 of the intake rocker arm 19 described later)
Is a position farther from the camshaft 6 than the center of the cylinder bore.
It comes to a position (a distance R ₂ from the axis of the rocker shaft 15). Further, the intermediate position of both exhaust valves 35 and the intermediate position of both intake valves 36 are arranged such that both exhaust valves 35 and both intake valves 36 are aligned in the engine width direction, that is, in the direction perpendicular to the cylinder bore center line in plan view. In comparison with the case of being arranged in (1), it is deviated to the cylinder bore center side by a predetermined dimension in the engine longitudinal direction.

The camshaft 6 is provided with seven journal portions 7a to 7g at predetermined positions in the axial direction at predetermined intervals. In addition, the camshaft 6 is provided with each cylinder 5A.
An exhaust cam 8 and an intake cam 9 are provided in front of and behind the four journal portions 7b to 7e corresponding to the center portion of the cylinder bore of 5D. Further, a front end portion 6a of the cam shaft 6 is driven by an engine output shaft (not shown) through a timing belt (not shown) (corresponding to a "winding transmission member" described in claims). A belt pulley 41 (corresponding to the “transmission body” described in the claims) that is driven to rotate is attached. A drive gear 44 is attached to the camshaft 6 between the journal portion 7f and the journal portion 7g near the rear end portion 6b. Here, the belt pulley 41 projects forward from the front end portion of the engine near the upper surface of the cylinder head 3. The drive gear 44 is housed in a gear housing chamber 50 provided in the cylinder head 3. In such a state, the cam shaft 6 is arranged so that its axis is oriented in the engine longitudinal direction, that is, the cylinder arrangement direction. The cam shaft 6 has cam bearing portions 10A to 10G corresponding to the respective journal portions 7a to 7g.
It is attached to the cylinder head 3 while being rotatably supported by.

Hereinafter, the first to seventh cam bearing portions 10A to 10 will be described.
G will be described. These cam bearing portions 10A-10
Of G, the first cam bearing portion 10A is arranged at the front end portion of the engine. And the 2nd-5th cam bearing part 10B-
10E is for each cylinder 5A in the longitudinal direction of the engine.
It is arranged at a position corresponding to the center of the cylinder bore of 5D, that is, at a position corresponding to the bore center. The sixth cam bearing portion 10F and the seventh cam bearing portion 10G are arranged in front of and behind the gear storage chamber 50, respectively.

As shown in FIGS. 3 and 4, the first cam bearing portion 10A is provided with a first type cam cap 11A which is fastened and fixed to the cylinder head 3 using a pair of cap bolts 12. . The cam cap 11A of the first type is provided with a semicircular cam shaft support portion 27 for supporting the cam shaft 6 on the lower surface thereof. Then, in the first cam bearing portion 10A, at a position diagonally above the cam shaft support portion 27, a front end portion 15a of the rocker shaft 15 is press-fitted and fixed by a recessed hole-like recess 28 (patented). (Corresponding to the “support portion” described in the claims) is provided.
An end of an oil passage 29, which communicates with an oil passage 39 in the cylinder head 3, is open in the press-fitting recess 28. The arc-shaped outer peripheral surface of the first type cam cap 11 </ b> A is a sealing surface for the head cover 4. The formation position of the press-fitting concave portion 28 in the width direction of the first type cam cap 11A is such that the press-fitting concave portion 28 is fixed to the cylinder head 3 when the first type cam cap 11A is fastened and fixed to the cylinder head 3. It is set at a position close to each head bolt 25 located on the 6 side (see FIGS. 1 and 3).

On the other hand, the second to sixth cam bearing portions 10B-10
Each F has a second type cam cap 11B. As shown in FIGS. 1 and 2, these second type cam caps 11B are provided with a semicircular cam shaft support portion 10Ba for supporting the cam shaft 6 on the lower surface thereof. Further, the second type cam cap 11B has a rocker shaft support portion 10 on which the rocker shaft 15 is mounted and supported on the upper surface side thereof.
It has Bb. The second type cam cap 11B is fastened and fixed to the cylinder head 3 by a pair of cap bolts 12. Of the pair of cap bolts 12, the cap bolt 12 located closer to the center of the cylinder bore in the engine width direction penetrates the rocker shaft 15 mounted on the rocker shaft support portion 10Bb in the vertical direction. And the rocker shaft 1
5 and the second type cam cap 11B are fastened together to the cylinder head 3 (co-tightening structure).

The seventh cam bearing portion 10G supports the rear end portion 6b of the cam shaft 6 on the rear side of the drive gear 44. The seventh cam bearing portion 10G is a third type cam cap 11
Equipped with C. This third type cam cap 11C
Since the structure is similar to that of the first type cam cap 11A from which the press-fitting recess 28 is removed, detailed description of the structure of the third type cam cap 11C is omitted.

Further, at the rear end 6b of the cam shaft 6, a vacuum pump 4 arranged at the rear end of the cylinder head 3 is provided.
2 are connected so that the vacuum pump 42 is driven by the engine output shaft via the camshaft 6. Further, a driven gear 45 connected to a power steering hydraulic pump 43 attached to the rear end portion of the cylinder head 3 is engaged with the drive gear 44, and as a result, the hydraulic pump 43 also passes through the camshaft 6. Driven by the engine output shaft.

The rocker shaft 15 is composed of a pipe (hollow member) having a predetermined diameter, and is located at a position closer to the center of the cylinder bore center than the cam shaft 6 when viewed in the engine width direction.
It is arranged so as to extend in the engine longitudinal direction (cylinder arrangement direction). And, the front end portion 1 of this rocker shaft 15
5a is press-fitted / fitted into the press-fitting recess 28 of the first type cam cap 11A. On the other hand, the rear end portion 15b of the rocker shaft 15 is closed by a blind cap (not shown), and is fixed to the cylinder head 3 together with the cam cap 11B of the sixth cam bearing portion 10F. Also, the rocker shaft 15 when viewed in the longitudinal direction of the engine
The four intermediate portions of the second to fifth cam bearing portions 10 are, respectively.
It is fixed to the cylinder head 3 together with the corresponding second type cam cap 11B at the positions corresponding to B to 10E by co-tightening.

In the mounting structure of the rocker shaft 15, as is apparent from FIGS. 1, 3 and 4, the head bolts 25 are arranged below the rocker shaft 15 at a predetermined interval. Further, the rocker shaft 15 functions as a supply passage of the lubricating oil to the valve operating mechanism. Thus, the lubricating oil introduced into the rocker shaft 15 from the oil passage 39 of the cylinder block 2 through the oil passage 29 of the first type cam cap 11A is inside the rocker shaft 15 (hollow portion).
Through the cylinders 5A to 5D and distributed to the rocker arms 16 and 19 and the like.

As seen in the longitudinal direction of the engine, an exhaust rocker arm 16 and an intake rocker arm 19 provided for each cylinder are swingable at predetermined positions corresponding to the cylinders 5A to 5D of the rocker shaft 15. It is installed. The exhaust rocker arm 16 and the intake rocker arm 19 are
Since the basic structure is common, the specific structure will first be described below by taking the exhaust rocker arm 16 as an example, and then the structure of the intake rocker arm 19 will be described with reference to this, and thereafter both rocker arms 16 will be described. , 19 will be described relative to each other.

As shown in FIGS. 1 and 2, at one end (right end portion) of the exhaust rocker arm 16, there is a cam roller 17 which comes into contact with the exhaust cam 8 provided on the cam shaft 6 (see the claims). (Corresponding to the “contact portion”), and the other end (the left end portion) is provided with two exhaust valves 3 via the pressing member 23.
A pressing portion 18 for pressing the 5 together is provided.

As shown enlarged in FIGS. 5 to 7, in the exhaust rocker arm 16, the cam roller 17 is
It is rotatably supported by a shaft member 62 attached to one end 61. Further, a hole 64 for inserting the rocker shaft 15 is provided at a substantially central portion of the exhaust rocker arm 16. Further, the exhaust rocker arm 16 is provided with an oil passage 65 whose one end opens into the hole 64 and extends toward the other end 63 of the exhaust rocker arm 16.

Again, as shown in FIGS. 1 and 2, the pressing member 23 has a substantially T-shape, and is erected on the cylinder head 3 at a central position between the two axial centers of the two exhaust valves 35. The guide shaft 24 is arranged so that it can reciprocate in the vertical direction. And both ends of the pressing member 23 are
Each of them is in contact with one corresponding head of the two exhaust valves 35. Therefore, the rocker arm 16 for exhaust is attached to the camshaft 6
When the exhaust valves 35 swing with the rotation, the exhaust valves 35 are opened and closed together at the same timing.

On the other hand, one end (right end portion) of the intake rocker arm 19 is in contact with the intake cam 9 provided on the cam shaft 6 and corresponds to the cam roller 20 (corresponding to the "contact portion" described in the claims). Is provided at the other end (left end) of the exhaust rocker arm 16 and a pressing member (not shown) having the same structure and function as the exhaust rocker arm 16 is used to press the two intake valves 36 together. A section 21 is provided.

As shown in the enlarged view of FIGS. 8 to 10, in the intake rocker arm 19, the cam roller 20 is provided.
Are rotatably supported by a shaft member 68 attached to one end 67. A hole 70 for inserting the rocker shaft 15 is provided at a substantially central portion of the intake rocker arm 19. Further, the intake rocker arm 19 is provided with an oil passage 71 whose one end opens into the hole 70 and extends toward the other end 69 of the intake rocker arm 19. Thus, when the intake rocker arm 19 swings along with the rotation of the cam shaft 6, the intake valves 36 are opened and closed together at the same timing.

The exhaust rocker arm 16 and the intake rocker arm 19 are as shown in FIG.
The pressing portions 18 and 21 are respectively connected to the cam rollers 17 and 20.
On the other hand, when viewed in the longitudinal direction of the engine, that is, in the axial direction of the rocker shaft 15, it has a planar shape that is offset toward the center of the cylinder bore.

The engine 1 according to the present invention having such a structure has the following unique advantages which conventional engines of the same type do not have.

That is, first, in the engine 1, the two exhaust valves 35 and the two intake valves 36 provided for each of the cylinders 5A to 5D are arranged in the engine longitudinal direction (axial direction of the camshaft 6). In a zigzag pattern, and the exhaust valves 35 and the intake valves 36 are disposed via one exhaust rocker arm 16 and one intake rocker arm 19, respectively.
The basic structure is driven by the cam shaft 6. Thus, in each rocker arm 16 and 19,
The positions in the engine longitudinal direction of the pressing portions 18, 21 for pressing the pressing members 23 arranged at the intermediate positions between the shaft centers of the exhaust valves 35 or the intermediate positions between the shafts of the intake valves 36 are equal to each other. Compared with the case where the exhaust valve 35 and both intake valves 36 are arranged side by side in the engine width direction (direction perpendicular to the axial direction of the cam shaft 6 in plan view), the state of being displaced toward the center of the cylinder bore is Become. Therefore, if the rocker arms 16 and 19 are arranged so as to extend in the engine width direction in a plan view, that is, the straight lines connecting the pressing portions 18 and 21 and the cam rollers 17 and 20 are arranged so as to extend in the engine width direction. Both rocker arms 16 and 19
The cam rollers 17 and 20 are close to each other in the longitudinal direction of the engine, and it is difficult to arrange the second to fifth cam bearing portions 10B to 10E between them, that is, at positions corresponding to the bore centers. In addition, in spite of this difficulty, the second to fifth cam bearing portions 10B to 10 are intentionally placed at positions corresponding to the bore center.
When arranging E, if the arrangement structure of the head bolts 25 is a six-tightening structure, it is necessary to avoid mutual interference between the head bolts 25 and the cam bearing portions 10B to 10E. When the parts 10B to 10E are viewed in the engine width direction, it is necessary to largely separate the parts 10B to 10E in the direction opposite to the center of the cylinder bore. In addition, each head bolt 2
5 is a head bolt hole 38 using the head bolt seat 30.
Is screwed into.

However, in the engine 1 according to this embodiment, the press contact portions 18 and 21 of the exhaust rocker arm 16 and the intake rocker arm 19 are centered on the cylinder bore in the engine longitudinal direction with respect to the cam rollers 17 and 20, respectively. Since it is deviated to the part side, the interval between both cam rollers 17 and 20 becomes wide. Therefore, it becomes easy to dispose the cam bearing portions 10B to 10E at the positions corresponding to the bore centers.

Further, when the second to fifth cam bearing portions 10B to 10E are arranged at the bore center corresponding positions as described above, if a part of the head bolt 25 is arranged at the bore center corresponding positions, the second to fifth cam bearing portions 10B to 10E are arranged. 5 The cam bearings 10B to 10E and the head bolt 25 interfere with each other. However, the engine 1 according to this embodiment
Then, the arrangement position of the head bolt 25 is a position deviated from the cylinder bore as viewed in the longitudinal direction of the engine, that is, slightly forward of the first cylinder 5A located at the frontmost side, the position between the cylinder bores, and the fourth cylinder located at the rearmost side. The head bolt 25 does not exist at a position corresponding to the center of the cylinder bore as viewed in the engine longitudinal direction (axial direction of the camshaft 6) because it is only arranged slightly rearward of the 5D.

Therefore, the second to fifth cam bearing portions 10B are
It is possible to dispose 10E to 10E as close as possible to the cylinder bore center side in the engine width direction, in other words, to dispose the camshaft 6 as close to the cylinder bore center side as possible. Therefore, the size of the engine 1 in the width direction can be made as small as possible, and the engine 1 can be made compact in the engine width direction.

Secondly, generally, as in the engine 1 according to this embodiment, a belt pulley 41 drivingly connected to the engine output shaft through a timing belt is arranged at the front end portion 6a of the cam shaft 6. In this case, a tensile force acts on the first cam bearing portion 10A located at the front end portion of the engine from the engine output shaft side via the belt pulley 41. Further, the first cam bearing portion 10A has a second cam bearing portion 10B.
A part (loading part) of the load caused by the reaction force of the rocker arm located on the front side of the rocker arm acts. For this reason,
The load condition of the first cam bearing portion 10A becomes more severe than that of the other cam bearing portions 10B to 10G.

Thus, in the engine 1 according to this embodiment, the second cam bearing portion 10B is arranged at the position corresponding to the bore center, and among the exhaust rocker arm 16 and the intake rocker arm 19 corresponding to the first cylinder 5A. The lever ratio of the exhaust rocker arm 16 located on the front side is set smaller than the lever ratio of the intake rocker arm 19 located on the rear side. According to this configuration, the exhaust rocker arm 16 of the first cylinder 5A is located on the front side of the second cam bearing portion 10B, so that the load based on the reaction force of the exhaust rocker arm 16 is applied to the first cam bearing portion 10A. To work. However, since the intake rocker arm 19 of the first cylinder 5A is located rearward of the second cam bearing portion 10B, the load based on the reaction force of the intake rocker arm 19 does not act on the first cam bearing portion 10A. . Further, since the lever ratio of the exhaust rocker arm 16 is smaller than the lever ratio of the intake rocker arm 19, the load based on the reaction force of the exhaust rocker arm 16 is relatively small. Moreover, the load based on the reaction force of the exhaust rocker arm 16 is shared and received by the first cam bearing portion 10A and the second cam bearing portion 10B. Therefore, the first cylinder 5
The load acting on the first cam bearing portion 10A based on the reaction force of the exhaust rocker arm 16 of A is extremely small.

That is, the total load applied to the first cam bearing portion 10A is the same as the load from the belt pulley 41 and the first cylinder 5A.
Of the two rocker arms 16 and 19 having a small lever ratio, only a part (loading part) of the load based on the reaction force of the exhaust rocker arm 16. On the other hand, when the cam bearing portion is arranged at the position between the cylinder bores as in the conventional engine, the first cam bearing portion 10A has two loads, the load from the belt pulley 41 and the first cylinder 5A. A part (loading part) of the load based on the reaction force of the rocker arms 16 and 19 acts. Therefore, the engine 1 according to the present embodiment has a first
The load acting on the cam bearing portion 10A is reduced, and the reliability of the first cam bearing portion 10A is increased accordingly, and at the same time,
The diameter dimension or width dimension of the first cam bearing portion 10A can be reduced, and the first cam bearing portion 10A and thus the engine 1 can be made compact.

Thirdly, in the engine 1 according to this embodiment, in each of the cylinders 5A to 5D, of the exhaust rocker arm 16 and the intake rocker arm 19, the lever ratio of the exhaust rocker arm 16 located on the front side is rear. It is set smaller than the lever ratio of the intake rocker arm 19 located on the side, and the umbrella diameter of the exhaust valve 35 is set smaller than the umbrella diameter of the intake valve 36. Therefore, the passage cross section of the intake port 34 opened and closed by the intake valve 36 becomes large, and the intake charging efficiency and thus the engine output are increased.

Fourth, in the engine 1 according to this embodiment, the head bolt 25 located on the cam shaft 6 side in the engine width direction is arranged below the rocker shaft 15. For this reason, the rocker shaft 15 is attached to the head bolt 25.
Can be brought closer to the center side of the cylinder bore regardless of the presence of. By the way, if the rocker shaft 15 is mounted on the cylinder head 3 using a mounting member different from the cam cap 11B.
If it is fastened, it is necessary to dispose the cam cap 11B and the mounting member so as to be separated from each other in the engine width direction to avoid mutual interference between the two. However,
In this engine 1, the rocker shaft 15 has the cap bolt 1
It is fixed together with the cam cap 11B by 2 together. Therefore, the above-mentioned inconvenience does not occur, and the rocker shaft 15 and the cam shaft 6 can be moved closer to the center side of the cylinder bore as viewed in the engine width direction.
These synergistic effects further promote compactification of the engine 1 in the width direction.

Fifth, in the engine 1 according to this embodiment, the front end portion 15a of the rocker shaft 15 is fitted into the press-fitting recess 28 provided in the first cam bearing portion 10A.
5 is fitted and fixed in the axial direction (engine longitudinal direction). Therefore, the front end portion 15a has the cylinder head 3
The structure is simplified and workability is improved when the rocker shaft 15 is attached or detached as compared with a conventional engine in which bolts are fastened. Further, for example, when the head bolt 25 is arranged in the vicinity of the front end portion 15a of the rocker shaft 15, the front end portion 1
When 5a is fastened to the cylinder head 3 using a fastening bolt or the like, in order to avoid mutual interference between the fastening bolt and the head bolt 25, the position of the first cam bearing portion 10A is shifted forward and the fastening is performed. It is necessary to secure a space for arranging the bolt for use, and as a result, the size of the engine 1 in the longitudinal direction becomes large. However, in this engine 1, since the front end portion 15a of the rocker shaft 15 is fitted and fixed in the press-fitting recess 28 provided in the first cam bearing portion 10A, there is a space for disposing such fastening bolts. No need to secure. Therefore, when viewed in the longitudinal direction of the engine, the first cam bearing portion 10A is connected to the first cylinder 5A.
You can get closer to the side. Therefore, as shown in FIG. 1, the distance L ₁ between the first cam bearing portion 10A and the second cam bearing portion 10B can be made smaller than the inter-bore distance L ₂ , and as a result, the engine 1 Further miniaturization is achieved in the longitudinal direction.

By the way, in the cylinder head 3 of the engine 1 according to this embodiment, various measures have been taken in order to increase the strength or durability of the cylinder head wall or the water jacket wall in the vicinity of the cylinders 5A to 5D. This will be explained below. 11-
As shown in FIG. 15, in the cylinder head 3 of the engine 1, as seen in the engine longitudinal direction (that is, the cylinder head longitudinal direction), a pair of head bolts are inserted only at positions deviated from the cylinder bores so as to sandwich the cylinder bore center line. The holes 38 are provided so that the four head bolt holes 38 are located around each cylinder bore in plan view. Here, each cylinder 5A-5D
In Fig. 4, the four head bolt holes 38 located around the cylinder bore are arranged at positions such that when viewed in plan, a quadrangle with the central portion of these as the apex is a square. The head bolts 25 are screwed into the head bolt holes 38, respectively.

For example, for the first cylinder 5A, among the four head bolt holes 38, a straight line Y (the above-mentioned straight line passing through the center portion of the head bolt hole 38 located on the left front and the center portion of the head bolt hole 38 located on the right rear). (One diagonal of the square)
An opening portion of the first intake port 34 to the combustion chamber 13 and an opening portion of the first exhaust port 33 to the combustion chamber 13 are arranged on the above. Here, the first intake port 34
Of the two intake ports 34 is the intake port 34 located farther from the left side surface of the cylinder head 3, that is, the intake side surface when viewed in the engine width direction. The first exhaust port 33 is one of the two exhaust ports 33 that is located farther from the right side surface of the cylinder head 3, that is, the exhaust side surface when viewed in the engine width direction. The intake passage 32 is connected to both intake ports 34.
Combustion air is supplied from. Also,
The exhaust gas is exhausted from both exhaust ports 33 to the exhaust passage 31. The other cylinders 5B to 5D
Also has a similar structure.

In the cylinder head 3, a water jacket 7 for cooling (cooling) the engine 1 is introduced (or discharged) through a cross drill hole 74 or the like.
2 is formed. A fuel injection valve insertion hole 73 into which the fuel injection valve 26 (fuel injection nozzle) is fitted is formed in the cylinder head 3 at a position corresponding to the center of the cylinder bore in plan view. Further, in the cylinder head 3, the exhaust port side vertical wall portion 75 and the intake port side vertical wall portion 7 that swell into the water jacket 72 are provided in order to preferably control the flow of the cooling water in the water jacket 72.
7 are provided.

Further, as shown in FIG. 16, the cylinder head 3 has a shaft hole 79 through which the valve shaft of the intake valve 36 passes.
And a shaft hole 80 for passing the valve shaft of the exhaust valve 35. Further, the cylinder head 3 is provided with a lubricating oil passage 82 for passing lubricating oil.

Further, as shown in FIGS. 12 and 17, in this cylinder head 3, the wall portion of the intake port 34 or the intake passage 32 is the upper wall (middle deck) of the water jacket 72 on the upstream side in the intake flow direction. Is bound to. On the other hand, as shown in FIGS. 12 and 18, a water jacket space is formed between the wall of the exhaust port 33 or the exhaust passage 31 and the upper wall (middle deck) of the water jacket 72.

The cylinder head 3 has cylinders 5A to 5D.
In the vicinity, it extends upward from the bottom wall (lower deck) of the water jacket 72 over the space between the first exhaust port 33 and the bolt boss portion of the front left head bolt hole 38 arranged at a position facing the exhaust port 33. A rib 76 is provided. On the other hand, such a rib 76 is provided between the first intake port 34 and the bolt boss portion of the right rear head bolt hole 38 arranged at a position facing the intake port 34. Absent.

As described above, in the engine 1, the intake port 34 or the wall portion of the intake passage 32 is connected to the upper wall of the water jacket 72 on the upstream side in the intake flow direction on the intake port side. The rigidity of the surrounding water jacket wall is relatively high. On the other hand, on the exhaust port side, since there is a space between the wall of the exhaust port 33 or the exhaust passage 31 and the upper wall of the water jacket 72, the rigidity of the water jacket wall around the exhaust port 33 is Relatively low. Therefore, a rib 76 is provided on the exhaust port side to provide the exhaust port 33.
The rigidity of the surrounding water jacket wall is increased, which improves the sealing performance of the cylinder bore on the exhaust port side.

On the other hand, on the intake port side, the head bolt 2
Due to the axial force (fastening force) of 5, tensile stress is induced in the water jacket wall around the intake port 34, and this tensile stress may cause cracks in the water jacket wall around the intake port 34. Therefore, in order to relieve the tensile stress applied on the intake port side, it is better not to increase the rigidity of the water jacket wall around the intake port 34 so much. Therefore, in this engine 1, no rib is provided on the intake port side.

The reason why the rib 76 is provided only on the exhaust port side will be described in more detail below. That is, as shown in FIGS. 16 to 18, in the cylinder head 3,
On the exhaust port side, the exhaust port 33 or the exhaust passage 31
The upper wall of the water jacket 72 and the upper wall of the water jacket 72 (middle deck) are not connected. That is, since there is a water jacket space between both walls, the exhaust port 3
At around 3, the rigidity of the water jacket wall or the cylinder head wall becomes relatively low. Therefore, it is necessary to increase the rigidity of the wall on the exhaust port side.

On the other hand, on the intake port side, the intake port 34
Or the upper wall of the intake passage 32 and the water jacket 72
Since it is connected to the upper wall from the middle, intake port 3
At around 4, the rigidity of the water jacket wall or the cylinder head wall is originally high. Therefore, it is basically not necessary to provide the rib on the intake port side. In addition, if the rigidity of the water jacket wall or the cylinder head wall on the intake port side is too high, the following problems will occur.

That is, as shown in FIGS. 16 and 19, the axial force of the head bolt 25 acts on the cylinder head 3 as shown by arrows F ₁ and F ₂ . At this time, since the side wall stands on the outer peripheral side of the cylinder bore around the intake port 34, and the lubricating oil passage 82 is provided immediately on the right side (outside) of the head bolt 25 (head bolt hole 38), The rigidity of the bolt boss portion of the head bolt hole 38 into which the head bolt 25 is inserted is increased to the right (outward), so that the bolt boss portion tends to fall in the direction indicated by arrow F ₄ . As a result, the upper wall (middle deck) of the water jacket 72 is inevitably pushed in the direction indicated by the arrow F ₃ , and is deformed into the shape exaggeratedly shown in FIG. In addition, in FIG. 19, a broken line indicates a state where the axial force of the head bolt 25 is not applied to the cylinder head 3 (a state where the cylinder head 3 is not deformed), and a solid line indicates a state where the axial force of the head bolt 25 is applied (deformed). The state is shown).

Thus, the throat portion of the first intake port 34 is deformed in the direction in which its volume increases as indicated by the arrow H ₁ . Therefore, tensile stress that promotes the occurrence of cracks is induced at the corners of the water jacket wall. Here, if the rigidity of the water jacket wall is high, the tensile stress applied thereto becomes strong and cracks are likely to occur. Therefore, if the rib 78 (see FIG. 17) is provided in this portion as indicated by an imaginary line, the tensile stress applied thereto becomes extremely large and cracks are more likely to occur. Therefore, the engine 1 according to the present embodiment
In the cylinder head 3, the ribs 78 are not provided in this portion to prevent the rigidity thereof from being excessively increased, and to prevent the occurrence of cracks.

On the other hand, around the exhaust port of the cylinder head 3, the pressing force in the direction of the arrow F ₃ caused by the water jacket wall or the cylinder head wall is applied to the corner portion of the peripheral wall of the first exhaust port 33. On the other hand, as shown by the arrow H ₂ , it acts in the compression direction, and compressive stress is induced in this portion. The compressive stress does not cause cracks. Therefore, a rib 76 is provided at this portion to increase the rigidity thereof and enhance the sealing performance of the cylinder bore. The ribs 76 not only have no adverse effect on the occurrence of cracks, but rather suppress the occurrence of cracks.

As described above, the cylinder head 3 extends inwardly from the exhaust side surface (right side surface) of the cylinder head 3 toward the first intake port 34.
Supply (or discharge) cooling water to the water jacket 72
A cross drill hole 74 is provided. For this reason,
Even if a rib is not provided between the first intake port 34 and the bolt boss portion of the right rear head bolt hole 38 that faces the intake port 34, the peripheral wall of the cross drill hole 74 prevents the surrounding of the intake port 34. Water jacket walls are reinforced. The cross drill hole 74 is not provided on the intake side surface (left side surface) of the cylinder head 3. This is because the sub-chamber (vortex chamber) diesel engine and the cylinder block are commonly used.

Further, the engine 1 according to this embodiment
Since the second to fifth cam bearing portions 10B to 10E are arranged at the positions corresponding to the bore centers, the layout of the nozzle pressing member for fixing the fuel injection valve 26 (fuel injection nozzle) is originally difficult. Become. Therefore, in this engine 1, the layout of the nozzle pressing member is devised so as to facilitate the layout, and the cylinder head 3 is made compact, which will be described below. As shown in FIGS. 20 to 23, in the engine 1, the fuel discharged at high pressure from the fuel pump 84 passes through the first to fourth inlet pipes 86A to 86D, and the first to fourth cylinders 5A to 5A, respectively. 5D fuel injection valve 2
6 is supplied. And each cylinder 5A
Excess fuel not injected by the 5D fuel injection valve 26 is passed through a fuel return pipe 85 to a fuel tank (not shown).
Alternatively, it is returned to the fuel pump 84. Here, the first to fourth inlet pipes 86A to 86D extend in the engine width direction at positions close to the fuel injection valve 26.

In each of the cylinders 5A to 5D of the engine 1, the fuel injection valve 26 is arranged at the center of the cylinder bore in plan view. Then, the nozzle pressing member 90 for fixing the fuel injection valve 26 is located at a position opposite to the cam shaft 6 with respect to the fuel injection valve 26 in the engine width direction, and the valve shaft of the intake valve 36 and the exhaust valve 35. It is arranged between the valve shaft and the. That is, in each of the cylinders 5A to 5D, the nozzle pressing member 90 is arranged immediately to the left of the fuel injection valve 26. The nozzle pressing member 90 is fixed to the cylinder head 3 with a mounting bolt 91. Further, in this engine 1, the nozzle pressing member 90
Inlet piping 86A-86D is arrange | positioned above. Then, in a plan view, the extending direction of the nozzle pressing member 90 and the extending direction of the inlet pipes 86A to 86D are slightly displaced.

Thus, in this engine 1, the nozzle pressing member 90 can be easily arranged. That is, in general, the fuel injection valve 26 is arranged near the center of the cylinder bore in plan view, and the nozzle pressing member 90 is arranged close to the nozzle of the fuel injection valve 26. Further, in this diesel engine 1, since the cam bearing portions 10B to 10E are arranged at the positions corresponding to the bore centers, the nozzle pressing member 90 is viewed from the fuel injection valve 26 to the cam shaft 6 from the fuel injection valve 26 as in the conventional engine. If it is arranged on the side, that is, on the right side of the fuel injection valve 26, its layout becomes very difficult. However, in this engine 1, since the nozzle pressing member 90 is arranged on the opposite side of the fuel injection valve 26 from the cam shaft 6, that is, on the left side of the fuel injection valve 26, the layout of the nozzle pressing member 90 is extremely easy. Becomes Further, since the inlet pipes 86A to 86D are arranged above the nozzle pressing member 90, the nozzle pressing member 90 and the inlet pipes 86A to 8D.
6D and layout do not interfere with each other. Therefore, the layout of the nozzle pressing member 90 becomes easier. Since the extending direction of the nozzle pressing member 90 and the extending direction of the inlet pipes 86A to 86D are deviated from each other, the layout of the nozzle pressing member 90 is further facilitated. By arranging the nozzle pressing member 90 in this way, the cylinder head 3 and thus the engine 1 can be made compact.

[Brief description of drawings]

FIG. 1 is a plan view of a direct injection diesel engine according to the present invention with a head cover removed.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG.

FIG. 3 is an enlarged sectional view taken along line III-III in FIG.

4 is a view taken in the direction of arrows IV-IV in FIG. 3;

FIG. 5 is a plan view of an exhaust rocker arm.

FIG. 6 is a side view of the exhaust rocker arm shown in FIG.

7 is a cross-sectional view taken along the line JJ of FIG.

FIG. 8 is a plan view of an intake rocker arm.

9 is a side view of the intake rocker arm shown in FIG. 8. FIG.

10 is a sectional view taken along line KK of FIG.

11 is a plan sectional view of a cylinder head of the engine shown in FIG.

12 is an elevational cross-sectional view around the fuel injection valve insertion hole of the cylinder head shown in FIG.

13 is an elevational sectional view around the cross drill hole of the cylinder head shown in FIG.

14 is an elevational cross-sectional view around the exhaust port side water jacket of the cylinder head shown in FIG.

FIG. 15 is an elevational sectional view around the intake port side water jacket of the cylinder head shown in FIG. 11.

16 is a plan cross-sectional view at the upper position of the water jacket in the vicinity of one cylinder of the cylinder head shown in FIG.

17 is a sectional view taken along line MM of FIG.

18 is an elevational cross-sectional view around the exhaust port of the cylinder head shown in FIG.

FIG. 19 is a cross-sectional view taken along the line LL in FIG. 16, showing exaggeratedly the state in which the deformation has occurred due to the axial force of the head bolt.

20 is a plan view of a fuel supply system of the engine shown in FIG.

FIG. 21 is a side view of the fuel supply system shown in FIG.

22 is a front view of the fuel supply system shown in FIG. 20. FIG.

FIG. 23 is a partially sectional elevation view of a fuel injection valve and a nozzle pressing member.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder block, 3 ... Cylinder head, 4 ... Head cover, 5A-5D ... 1st-4th cylinder, 6 ... Cam shaft, 7a-7g ... Journal part, 8 ... Exhaust cam, 9 ... Intake Cams 10A to 10G ... First to seventh cam bearing portions, 11A to 11C ... Cam caps, 12 ... Cap bolts, 13 ... Combustion chambers, 15 ... Rocker shafts, 16 ... Exhaust rocker arms, 17 ... Cam rollers, 18 ... Pressing part,
19 ... intake rocker arm, 20 ... cam roller, 21 ...
Pressing part, 23 ... Pressing member, 24 ... Guide shaft, 25 ... Head bolt, 26 ... Fuel injection valve, 27 ... Cam shaft support part, 2
8 ... press-fitting recess, 29 ... oil passage, 30 ... head bolt seat, 31 ... exhaust passage, 32 ... intake passage, 33 ... exhaust port, 34 ... intake port, 35 ... exhaust valve, 36 ... intake valve, 38 ... head Bolt hole, 39 ... Oil passage, 41 ...
Belt pulley, 42 ... Vacuum pump, 43 ... Hydraulic pump, 44 ... Drive gear, 45 ... Driven gear, 50 ... Gear storage chamber, 72 ... Water jacket, 74 ... Cross drill hole, 76 ... Rib, 79 ... Intake valve valve Shaft hole of shaft, 80 ... Shaft hole of valve shaft of exhaust valve, 84 ... Fuel pump, 85 ... Fuel return pipe, 86A to 86D ... First to fourth inlet pipes, 9
0 ... Nozzle pressing member, 91 ... Mounting bolt.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location F02F 1/24 F02F 1/24 J 1/36 1/36 C (72) Inventor Koji Tachikawa Fuchu, Aki-gun, Hiroshima Prefecture Machida Engineering Co., Ltd. 3-1, Machida Shinchi

Claims (22)

[Claims] 1. An intake valve center line, wherein two intake valves and two exhaust valves are provided for each cylinder, and the two intake valves are straight lines that pass through the central portions of both intake valves in plan view. And the center lines of the cylinder bores, which are straight lines passing through the center parts of the cylinder bores, are arranged in a staggered manner so as to intersect at a predetermined inclined angle, while the two exhaust valves are arranged so that the center parts of both the exhaust valves are seen in plan view. In a direct-injection diesel engine in which the exhaust valve center line, which is a straight line passing through, and the cylinder bore center line intersect at a predetermined inclined angle in a zigzag manner, the cylinder bore deviates from the cylinder bore when viewed in the direction in which the cylinder bore center line extends. A pair of head bolt holes are provided only at positions so as to sandwich the cylinder bore center line,
As a result, four head bolt holes are arranged around each cylinder bore, and when viewed in a plan view in a direction perpendicular to the center line of the cylinder bore, the engine extends beyond the peripheral edge of one of the cylinder bores in the direction in which the center line of the cylinder bore extends. One cam shaft that is rotationally driven by the output shaft is arranged, and a cam bearing portion that rotatably supports the cam shaft is arranged at a position corresponding to the center portion of the cylinder bore as viewed in the direction in which the center line of the cylinder bore extends. The two intake valves are opened and closed by one intake rocker arm that is rockably driven by an intake cam provided on the cam shaft, while the two exhaust valves are exhausted on the cam shaft. A direct injection diesel engine characterized by being opened and closed by a single exhaust rocker arm that is rockably driven by a vehicle cam. Jin. 2. The intake rocker arm is located at an intermediate position between the abutment portion abutting on the intake cam and the center portions of the two intake valves in plan view, and pushes the two intake valves at the same timing. The exhaust rocker arm is located at an intermediate position between the central portions of the two exhaust valves in plan view and the abutment part that abuts the exhaust cam. At least one of the rocker arms is biased toward the center of the cylinder bore with respect to the abutting portion when viewed in the direction in which the center line of the cylinder bore extends. The direct-injection diesel engine according to claim 1, characterized in that 3. Only in the intake rocker arm,
The direct injection diesel engine according to claim 2, wherein the pressing portion is deviated from the contact portion toward the center portion of the cylinder bore as viewed in the direction in which the center line of the cylinder bore extends. 4. In both of the intake rocker arm and the exhaust rocker arm, the pressing contact portion is deviated toward the cylinder bore center portion side with respect to the contact portion as viewed in the extending direction of the cylinder bore center line. The direct injection diesel engine according to claim 2, wherein the deviation amount of the intake rocker arm is larger than the deviation amount of the exhaust rocker arm. 5. A rocker shaft that swingably supports the intake rocker arm and the exhaust rocker arm is closer to the center of the cylinder bore than the cam shaft when seen in a direction perpendicular to the direction in which the center line of the cylinder bore extends in plan view. At the position of, the cam shaft is arranged so as to extend in parallel with the cam shaft, and the cam shaft is arranged at a position lower than the rocker shaft. The direct injection diesel engine described in any one. 6. The arm of the rocker arm, of the intake rocker arm and the exhaust rocker arm, which has a smaller deviation amount toward the center of the cylinder bore with respect to the contact portion of the pressing portion when viewed in the direction in which the center line of the cylinder bore extends. The direct injection diesel engine according to claim 2, wherein the length is shorter than the arm length of the other rocker arm. 7. The valve diameter of the intake valve is set larger than the valve diameter of the exhaust valve, and the lever ratio of the intake rocker arm is set larger than the lever ratio of the exhaust rocker arm. The direct-injection diesel engine according to claim 1 or 6, characterized by the above. 8. The direct injection diesel engine according to claim 7, wherein an arm length of the intake rocker arm is longer than an arm length of the exhaust rocker arm. 9. An intake valve center line which is provided with two intake valves and two exhaust valves for each cylinder, and the two intake valves are straight lines that pass through the center portions of both intake valves in a plan view. And the center lines of the cylinder bores, which are straight lines passing through the center parts of the cylinder bores, are arranged in a staggered manner so as to intersect at a predetermined inclined angle, while the two exhaust valves are arranged so that the center parts of both the exhaust valves are seen in plan view. In a direct-injection diesel engine in which the exhaust valve center line, which is a straight line passing through, and the cylinder bore center line intersect each other at a predetermined inclined angle in a zigzag manner, when viewed in a direction perpendicular to the cylinder bore center line in plan view. One cam shaft extending in the direction in which the cylinder bore center line extends is disposed in front of one peripheral edge of the cylinder bore, and the front end of the cam shaft is connected to the engine output shaft through a winding transmission member to drive the engine. And a cam bearing portion that rotatably supports the cam shaft is disposed at a position corresponding to the center of the cylinder bore when viewed in the direction in which the center line of the cylinder bore extends, and the two intake valves include: While being opened and closed by one intake rocker arm that is rockably driven by the intake cam provided on the cam shaft, the two exhaust valves are rockably driven by the exhaust cam provided on the cam shaft. A rocker shaft that is opened and closed by one exhaust rocker arm and swingably supports the intake rocker arm and the exhaust rocker arm is more than the cam shaft when viewed in a direction perpendicular to the extending direction of the cylinder bore center line in plan view. At the position near the center of the cylinder bore, it is arranged so as to extend parallel to the cam shaft and corresponds to the frontmost cylinder bore. Of the intake rocker arm and exhaust rocker arm, a direct injection diesel engine, characterized in that it is set smaller than the lever ratio of the rocker arm located on the lever ratio rear of the rocker arm located at the front side. 10. The intake rocker arm is located at an intermediate position between the contact portion abutting on the intake cam and the center portions of the two intake valves in plan view, and pushes the two intake valves at the same timing. The exhaust rocker arm is located at an intermediate position between the central portions of the two exhaust valves in plan view and the abutment part that abuts the exhaust cam. At least one of the rocker arms is biased toward the center of the cylinder bore with respect to the abutment, as viewed in the direction in which the center line of the cylinder bore extends. Rank,
A rocker shaft that swingably supports the intake rocker arm and the exhaust rocker arm is located at a position closer to the center of the cylinder bore than the cam shaft when viewed in a direction perpendicular to the extending direction of the cylinder bore center line in plan view. An intake rocker arm and an exhaust rocker arm corresponding to the cylinder bore located closest to the front are arranged so as to extend parallel to the cam shaft, and the cam bearing portion has a cam cap that is fastened and fixed to the cylinder head. The direct injection diesel engine according to claim 1, wherein the lever ratio of the rocker arm located on the front side is set smaller than the lever ratio of the rocker arm located on the rear side. 11. The direct injection diesel engine according to claim 9, wherein the lever ratio of the exhaust rocker arm is set smaller than the lever ratio of the intake rocker arm. 12. A rocker shaft for swingably supporting the intake rocker arm and the exhaust rocker arm is closer to the center of the cylinder bore than the cam shaft when seen in a direction perpendicular to the extending direction of the center line of the cylinder bore in plan view. 6. The cam bearing portion has a cam cap that is extended and arranged so as to be parallel to the cam shaft at the position of, and the cam bearing portion is fastened and fixed to the cylinder head.
Direct-injection diesel engine described in. 13. The rocker shaft is integrally fastened together with the cam cap by a bolt for fastening the cam cap, and is fixed to the cam shaft side of the cylinder bore center line in the head bolt hole. The direct-injection diesel engine according to claim 10 or 12, wherein the arranged head bolt hole is arranged at a position overlapping the rocker shaft in a plan view. 14. A front end portion of the rocker shaft is fitted and fixed in a direction in which a center line of a cylinder bore extends with respect to a support portion provided in a cam bearing portion located at a front end portion of the engine. A direct injection diesel engine according to claim 12 or 13. 15. When viewed in a plan view in a direction perpendicular to the center line of the cylinder bore, an upstream side of an intake port is opened on one side of the cylinder head, and an upstream side of an exhaust port is opened on the other side of the cylinder head. , On one diagonal of a quadrangle with the center of each of the four head bolt holes arranged around each cylinder bore as the apex of the intake port on the side far from the one side of the cylinder head side described above. An opening to the combustion chamber and an opening to the combustion chamber of the exhaust port on the side farther from the exhaust side on the other side of the cylinder head side are arranged, and are located on the diagonal line with the exhaust port. A rib projecting into the water jacket is provided on the bottom wall portion of the water jacket between the exhaust port and the bolt boss portion of the head bolt hole adjacent to the exhaust port. Direct injection diesel engine according to claim 1. 16. The wall portion of the intake port is connected to the upper wall of the water jacket on the upstream side in the intake flow direction, while the space portion is formed between the wall portion of the exhaust port and the upper wall of the water jacket. A direct injection diesel engine according to claim 15, characterized in that 17. At least one exhaust port and one intake port from the cylinder head side portion upstream of the exhaust port.
A cross drill hole that extends inwardly of the cylinder head between two adjacent combustion chamber openings and that supplies cooling water to the water jacket is provided.
The direct injection diesel engine according to claim 1. 18. The direct injection diesel engine according to claim 17, wherein the cross drill hole is provided only on the exhaust side of the cylinder head. 19. A fuel injection nozzle is disposed near a center of a cylinder bore in a plan view, and a nozzle pressing member for fixing the fuel injection nozzle is provided at a position opposite to the cam shaft with respect to the fuel injection nozzle. The direct injection diesel engine according to claim 1, wherein the diesel engine is disposed between the exhaust valve shaft and the exhaust valve shaft. 20. The direct injection diesel engine according to claim 19, wherein an inlet pipe for supplying fuel to the fuel injection nozzle is arranged above the nozzle pressing member. 21. In a plan view, a direction in which the nozzle pressing member extends is set substantially to the exhaust valve center line or the intake valve center line direction, and the direction is deviated from the extending direction of the inlet pipe. The direct injection diesel engine according to claim 20, wherein: 22. The direct injection diesel engine according to claim 20, wherein the inlet pipe extends near the fuel injection nozzle in a direction perpendicular to the extending direction of the cylinder bore center line.