Patent Description:
The following Patent Literature <NUM> (hereinafter, PTL <NUM>) discloses an engine having an EGR passage arranged inside the cylinder head thereof. Further, the following Patent Literature <NUM> (hereinafter, PTL <NUM>) discloses an engine in which an intake manifold is integrally formed with a cylinder head. The following Patent Literature <NUM> (hereinafter, PTL <NUM>) discloses an engine having a thermostat arranged inside the cylinder head thereof. Patent Literature <NUM> (hereinafter, PTL <NUM>) discloses a structure of an exhaust gas recirculation passage for recirculating a part of exhaust gas from the exhaust system of an engine to an intake system. Patent Literature <NUM> (hereinafter, PTL <NUM>) discloses a reflux apparatus for exhaust gas. Patent Literature <NUM> (hereinafter, PTL <NUM>) discloses a an internal-combustion engine provided with a recirculating system for exhaust gases. Patent Literature <NUM> (hereinafter, PTL <NUM>) discloses internal combustion engines, in particular to the water cooling system thereof.

In PTL <NUM> to PTL <NUM>, the cylinder head is integrally formed with an engine component such as the EGR passage, the intake manifold, and the thermostat. However, such a structure forms a steplike shape on the surface of the cylinder head, which makes <NUM>-face machining difficult. This requires a number of machining processes and high costs.

In view of the above problem, it is an object of the present invention to provide a cylinder head whose shape facilitates <NUM>-face machining, and an engine having such a cylinder head.

An aspect of the present invention is a cylinder head including: a plurality of exhaust ports configured to lead out exhaust gas from combustion chambers;.

The cylinder head of the present invention makes <NUM>-face machining easy, because the exhaust outlet or exhaust ports and EGR gas inlet of the EGR gas passage are arranged side-by-side on the flat first side surface, and the fresh air inlet of the intake air aggregate part and the EGR gas outlet of the EGR gas passage are arranged side-by-side on the flat second side surface.

The cylinder head of the above aspect of the present invention may further include: a thermostat case whose top part is open and communicates with a cooling water outlet pipe;.

This water jacket is formed in such a manner that its height on the exhaust side is higher than its height on the intake side. Therefore, air may be accumulated on the exhaust side. However, by forming the cooling water passage in such a manner that its height on the side of the thermostat case is equal to or higher than the height of the cooling water passage on the exhaust side, the accumulated air on the exhaust side of water jacket can be fed out to the side of the thermostat case through the cooling water passage. Therefore, the cooling efficiency of the engine can be improved.

The cylinder head of the above aspect of the present invention may be such that the thermostat case has a cooling water outlet that opens in a worked surface of a top surface machined to be flat.

This structure makes <NUM>-face machining easy, because the cooling water outlet of the thermostat case is arranged on the worked surface of the top surface machined to be flat.

An engine according to an aspect of the present invention includes the above described cylinder head, and a cooling water pump is arranged immediately below the thermostat case.

With this structure, a compact engine can be designed.

In the following, an embodiment of the present invention will be described with reference to the drawings.

First, a schematic structure of the engine <NUM> is described with reference to <FIG> and <FIG>. It should be noted that, in the following description, two sides parallel to a crankshaft <NUM> are referred to as the left and right. A side where a cooling fan <NUM> is arranged is referred to as the front side. A side where a flywheel housing <NUM> is arranged is referred to as the rear side. A side where an exhaust manifold <NUM> is arranged is referred to as the left side. A side where an intake manifold <NUM> is arranged is referred to as the right side. A side where a cylinder head cover <NUM> is arranged is referred to as the upper side. A side where an oil pan <NUM> is arranged is referred to as the lower side. These expressions are used as the references of four directions and the positional relation of the engine <NUM>.

An engine <NUM> as a motor mounted to a work machine such as an agricultural machine and a construction machine includes a crankshaft <NUM> serving as an output shaft of the engine and a cylinder block <NUM> having therein a piston (not shown). On the cylinder block <NUM>, a cylinder head <NUM> is mounted. On the right side surface of the cylinder head <NUM>, an intake manifold <NUM> is arranged. On the left side surface of the cylinder head <NUM>, an exhaust manifold <NUM> is arranged. The top surface side of the cylinder head <NUM> is covered by a head cover <NUM>. The crankshaft <NUM> has its front and rear ends protruding from front and rear surfaces of the cylinder block <NUM>. On the front surface side of the engine <NUM>, a cooling fan <NUM> is arranged. From the front end side of the crankshaft <NUM>, rotational power is transmitted to the cooling fan <NUM> through a cooling fan V-belt.

On the rear surface side of the engine <NUM>, a flywheel housing <NUM> is arranged. The flywheel housing <NUM> accommodates therein a flywheel <NUM> pivotally supported at the rear end side of the crankshaft <NUM>. The rotational power of the engine <NUM> is transmitted from the crankshaft <NUM> to operating units of the work machine through the flywheel <NUM>. An oil pan <NUM> for storing an engine oil is arranged on a lower surface of the cylinder block <NUM>. The engine oil in the oil pan <NUM> is supplied to lubrication parts of the engine <NUM> through an oil pump in the cylinder block <NUM>, and then returns to the oil pan <NUM>.

A fuel supply pump <NUM> is arranged below the intake manifold <NUM> on the right side surface of the cylinder block <NUM>. Further, the engine <NUM> includes injectors <NUM> for four cylinders. Each of the injectors <NUM> has a fuel injection valve of electromagnetic-controlled type. By controlling the opening/closing of the fuel injection valves of the injectors <NUM>, the high-pressure fuel in a common rail is injected from the injectors <NUM> to the respective cylinders of the engine <NUM>.

On the front surface side of the cylinder block <NUM>, a cooling water pump <NUM> for supplying cooling water is arranged. The rotational power of the crankshaft <NUM> drives the cooling water pump <NUM> along with the cooling fan <NUM>, through the cooling fan V-belt. With the driving of the cooling water pump <NUM>, the cooling water in a radiator (not shown) mounted to the work machine is supplied to the cylinder block <NUM> and the cylinder head <NUM> and cools the engine <NUM>. Then the cooling water having contributed to the cooling of the engine <NUM> returns to the radiator. Above the cooling water pump <NUM>, an alternator <NUM> is arranged.

The cooling water pump <NUM> is disposed below the intake manifold <NUM>, and a cooling water inlet pipe <NUM> in communication with the cooling water outlet of the radiator is arranged on the right side surface of the cylinder block <NUM>, at a height equal to the height of the cooling water pump <NUM>. A cooling water outlet pipe <NUM> that is in communication with a cooling water inlet of the radiator is fixed to an upper right side surface of the cylinder head <NUM>.

The intake manifold <NUM> is connected to an intake throttle member <NUM>. The fresh air (outside air) suctioned by the air cleaner is subjected to dust removal and purification in the air cleaner, and fed to the intake manifold <NUM> through the intake throttle member <NUM>, and then supplied to the respective cylinders of the engine <NUM>.

In an upper portion of the intake manifold <NUM>, an EGR device <NUM> is arranged. The EGR device <NUM> is a device that supplies part of the exhaust gas of the engine <NUM> (EGR gas from the exhaust manifold <NUM>) to the intake manifold <NUM>, and includes an EGR pipe <NUM> connecting to the exhaust manifold <NUM> through an EGR cooler <NUM> and an EGR valve case <NUM> that communicates the intake manifold <NUM> to the EGR pipe <NUM>.

A downwardly-open end portion of the EGR valve case <NUM> is bolt-fastened to an inlet of the intake manifold <NUM> protruding upward from the intake manifold <NUM>. Further, a rightwardly-open end portion of the EGR valve case <NUM> is coupled to an outlet side of the EGR pipe <NUM>. By adjusting the opening degree of the EGR valve member (not shown) in the EGR valve case <NUM>, the amount of EGR gas supplied from the EGR pipe <NUM> to the intake manifold <NUM> is adjusted. The EGR valve member is driven by an actuator <NUM> attached to the EGR valve case <NUM>.

In the intake manifold <NUM>, the fresh air supplied from the air cleaner to the intake manifold <NUM> through the intake throttle member <NUM> is mixed with the EGR gas (part of exhaust gas from the exhaust manifold <NUM>) supplied from the exhaust manifold <NUM> to the intake manifold <NUM> through the EGR valve case <NUM>. As described, by recirculating part of the exhaust gas from the exhaust manifold <NUM> to the engine <NUM> through the intake manifold <NUM>, the combustion temperature is lowered and the emission of nitrogen oxide (NOX) from the engine <NUM> is reduced.

The EGR pipe <NUM> is connected to the EGR cooler <NUM> and the EGR valve case <NUM>. The EGR pipe <NUM> includes a first EGR pipe 21a arranged on the right side of the cylinder head <NUM>, a second EGR pipe 21b formed in a rear end portion of the cylinder head <NUM>, and a third EGR pipe 21c arranged on the left side of the cylinder head <NUM>.

The first EGR pipe 21a is generally an L-shaped pipe. The first EGR pipe 21a has its inlet side coupled to an outlet side of the second EGR pipe 21b, and has its outlet side coupled to the EGR valve case <NUM>.

The second EGR pipe 21b is formed in such a manner as to penetrate through the rear end portion of the cylinder head <NUM> in the left-and-right directions as shown in <FIG>. In other words, the second EGR pipe 21b and the cylinder head <NUM> are integrally formed. The second EGR pipe 21b has its inlet side coupled to an outlet side of the third EGR pipe 21c, and has its outlet side connected to the inlet side of the first EGR pipe 21a.

The third EGR pipe 21c is formed inside the exhaust manifold <NUM>. In other words, the third EGR pipe 21c and the exhaust manifold <NUM> are integrally formed. With the third EGR pipe 21c and second EGR pipe 21b integrally formed with the exhaust manifold <NUM> and the cylinder head <NUM>, respectively, the space needed can be saved, and the pipes less likely receive an external impact.

Next, the following describes a structure of the cylinder head <NUM> with reference to <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, and <FIG>. <FIG> and <FIG> are each an exploded perspective view of the cylinder head <NUM>, the intake manifold <NUM>, and the exhaust manifold <NUM>. <FIG> and <FIG> are views as seen in different directions. <FIG> is a perspective cross-sectional view of the cylinder head <NUM> nearby the middle relative to an up and down direction. <FIG>, <FIG>, and <FIG> are cross-sectional views showing a lower portion, a middle portion, and a top portion of the cylinder head <NUM> relative to the up and down direction, respectively.

The cylinder head <NUM> has a generally rectangular parallelepiped shape. After casting, six surfaces of the cylinder head <NUM> (four side surfaces and two surfaces that are top and bottom surfaces) are subjected to a cutting process. As shown in <FIG> and the like, the cylinder head <NUM> includes: a plurality of exhaust ports <NUM> configured to lead out exhaust gas from combustion chambers; a plurality of intake ports <NUM> configured to introduce fresh air into the combustion chambers; an intake air aggregate part <NUM> configured to aggregate the plurality of intake ports <NUM>; and a second EGR pipe 21b in which EGR gas flows (corresponding to EGR gas passage of the present invention).

Each of the exhaust ports <NUM> is in communication with an exhaust valve hole 41a (see <FIG>, <FIG>, and the like) opened in the top surface of the corresponding cylinder, and leads out exhaust gas from the corresponding combustion chamber. In the position of the exhaust valve hole 41a, a not-shown exhaust valve is provided. Each exhaust port <NUM> extends towards left from the exhaust valve hole 41a, and the exhaust outlet 41b opens in the left side surface 4a (corresponding to the first side surface of the present invention) of the cylinder head <NUM>. A plurality of the exhaust outlets 41b are arranged and aligned in a front-and-rear direction. On the other hand, the exhaust manifold <NUM> has a plurality of exhaust inlets 6a respectively communicating with the plurality of the exhaust outlets 41b, the exhaust inlets 6a being arranged and aligned in the front-and-rear direction on a right side surface to be coupled with the left side surface 4a of the cylinder head <NUM>.

Each of the intake ports <NUM> is in communication with an intake valve hole 42a (see <FIG>, <FIG>, and the like) opened in the top surface of the corresponding cylinder, and introduces fresh air into the corresponding combustion chamber. In a position of the intake valve hole 42a, a not-shown intake valve is provided. The intake port <NUM> extends to the right from the intake valve hole 42a.

On the right side surface 4b of the cylinder head <NUM>, the intake air aggregate part <NUM> that aggregates the plurality of intake port <NUM> is formed. The intake air aggregate part <NUM> is in communication with a fresh air inlet of the plurality of intake port <NUM>. A fresh air inlet 43a of the intake air aggregate part <NUM> opens in the right side surface 4b of the cylinder head <NUM> (corresponding to the second side surface of the present invention). On the other hand, the intake manifold <NUM> has a fresh air outlet 5a that communicates with the fresh air inlet 43a, on the left side surface to be coupled with the right side surface 4b of the cylinder head <NUM>.

The second EGR pipe 21b is formed in such a manner as to penetrate through the rear end portion of the cylinder head <NUM> in the left-and-right directions as described hereinabove. The second EGR pipe 21b is provided in the rear of the exhaust port <NUM> and the intake port <NUM>. The EGR gas inlet 44a of the second EGR pipe 21b opens in the rear of the left side surface 4a of the cylinder head <NUM>. On the other hand, the exhaust manifold <NUM> has an EGR gas outlet 6b of a third EGR pipe 21c. The EGR gas outlet 6b communicates with the EGR gas inlet 44a, and is arranged on the right side surface of the exhaust gas manifold <NUM> to be coupled with the left side surface 4a of the cylinder head <NUM>. The plurality of the exhaust outlets 41b and the EGR gas inlet 44a are arranged side-by-side in the front-and-rear direction on the left side surface 4a of the cylinder head <NUM> having been subjected to a cutting process to be flat. In other words, the plurality of exhaust outlets 41b and the EGR gas inlets 44a are open in the same plane.

Further, the EGR gas outlet 44b of the second EGR pipe 21b is open at the rear of the right side surface 4b of the cylinder head <NUM>. The fresh air inlet 43a of the intake air aggregate part <NUM> and the EGR gas outlet 44b are arranged side-by-side on the right side surface 4b of the cylinder head <NUM> having been subjected to a cutting process to be flat. That is, the fresh air inlet 43a and the EGR gas outlet 44b are opened in the same plane.

In a front portion of the right side surface 4b of the cylinder head <NUM>, there is provided a thermostat case <NUM> whose upper portion is open and which communicates with the cooling water outlet pipe <NUM>. The thermostat case <NUM> is provided in front of the intake manifold <NUM>. Inside the thermostat case <NUM>, a not-shown thermostat is arranged. The cooling water outlet 45a of the thermostat case <NUM> is opened in the worked surface of the top surface 4c of the cylinder head <NUM> machined to be flat.

Inside the cylinder head <NUM>, a water jacket <NUM> is provided. The water jacket <NUM> is formed around the exhaust ports <NUM> and the intake ports <NUM>. As shown in <FIG> and <FIG>, the water jacket <NUM> is provided on both the exhaust side and the intake side from the lower surface side of the cylinder head <NUM> to the vicinity of the middle portion relative to the up and down direction. As shown in <FIG>, the water jacket <NUM> is provided only on the exhaust side, in the upper surface side of the head <NUM>. That is, the height of the water jacket <NUM> on the exhaust side is higher than the height of the water jacket <NUM> on the intake side. The cooling water in the water jacket <NUM> flows in a direction from the exhaust side to the intake side as indicated by an arrow W in <FIG> and <FIG>.

In the cylinder head <NUM>, a cooling water passage <NUM> communicating with the thermostat case <NUM> and the water jacket <NUM> is provided. The cooling water passage <NUM> is formed at a front part of the cylinder head <NUM>. The height of the cooling water passage <NUM> on the side of the thermostat case <NUM> is equal to or higher than the height of the cooling water passage <NUM> on the exhaust side. In the present embodiment, the height of the cooling water passage <NUM> on the side of the thermostat case <NUM> and the height of the cooling water passage <NUM> on the exhaust side are substantially the same as shown in <FIG>. This way, the cooling water in the cooling water passage <NUM> flows from the exhaust side towards the thermostat case <NUM>. As a result, the air accumulated on the exhaust side of the water jacket <NUM> can be fed to the side of the thermostat case <NUM>, and the cooling efficiency of the engine <NUM> can be increased.

<FIG> is a cross-sectional view of the cylinder block <NUM> and the cylinder head <NUM> cut in the up and down direction at a position of the thermostat case <NUM>. The cooling water pump <NUM> is arranged immediately below the thermostat case <NUM>. More specifically, the thermostat case <NUM> and the cooling water inlet 15a of the cooling water pump <NUM> are arranged side by side in the up and down direction. To a lower portion of the thermostat case <NUM>, a bottom bypass <NUM> in which cooling water flows when the thermostat is closed is connected. The bottom bypass <NUM> is formed at the front of the cylinder block <NUM>. The bottom bypass <NUM> extends in the up and down direction and communicates with the cooling water inlet 15a of the cooling water pump <NUM>. By arranging the cooling water pump <NUM> immediately below the thermostat case <NUM>, the bottom bypass <NUM> can be formed in a simple shape. Therefore, a compact design of the engine <NUM> can be possible.

Claim 1:
A cylinder head (<NUM>) of an engine (<NUM>), comprising:
a plurality of exhaust ports (<NUM>) configured to lead out exhaust gas from combustion chambers;
a plurality of intake ports (<NUM>) configured to introduce fresh air into the combustion chambers;
an intake air aggregate part (<NUM>) configured to aggregate the plurality of intake ports (<NUM>); and
an EGR gas passage in which EGR gas flows, wherein
exhaust outlets (41b) of the plurality of exhaust ports (<NUM>) and an EGR gas inlet (44a) of the EGR gas passage are arranged side-by-side on a flat first side surface,
a fresh air inlet (43a) of the intake air aggregate part (<NUM>) and an EGR gas outlet (44b) of the EGR gas passage are arranged side-by-side on a flat second side surface which is a side opposite to the first side surface, charaterized in that
the EGR gas passage and the cylinder head (<NUM>) are formed integrally, and
the EGR gas passage is connected to an exhaust manifold (<NUM>) through an EGR cooler (<NUM>).