Patent ID: 12215641

EMBODIMENT OF EMBODIMENT

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

First, a schematic structure of the engine1is described with reference toFIG.1andFIG.2. It should be noted that, in the following description, two sides parallel to a crankshaft2are referred to as the left and right. A side where a cooling fan8is arranged is referred to as the front side. A side where a flywheel housing9is arranged is referred to as the rear side. A side where an exhaust manifold6is arranged is referred to as the left side. A side where an intake manifold5is arranged is referred to as the right side. A side where a cylinder head cover7is arranged is referred to as the upper side. A side where an oil pan11is arranged is referred to as the lower side. These expressions are used as the references of four directions and the positional relation of the engine1.

An engine1as a motor mounted to a work machine such as an agricultural machine and a construction machine includes a crankshaft2serving as an output shaft of the engine and a cylinder block3having therein a piston (not shown). On the cylinder block3, a cylinder head4is mounted. On the right side surface of the cylinder head4, an intake manifold5is arranged. On the left side surface of the cylinder head4, an exhaust manifold6is arranged. The top surface side of the cylinder head4is covered by a head cover7. The crankshaft2has its front and rear ends protruding from front and rear surfaces of the cylinder block3. On the front surface side of the engine1, a cooling fan8is arranged. From the front end side of the crankshaft2, rotational power is transmitted to the cooling fan8through a cooling fan V-belt.

On the rear surface side of the engine1, a flywheel housing9is arranged. The flywheel housing9accommodates therein a flywheel10pivotally supported at the rear end side of the crankshaft2. The rotational power of the engine1is transmitted from the crankshaft2to operating units of the work machine through the flywheel10. An oil pan11for storing an engine oil is arranged on a lower surface of the cylinder block3. The engine oil in the oil pan11is supplied to lubrication parts of the engine1through an oil pump (not shown) in the cylinder block3, and then returns to the oil pan11.

A fuel supply pump13is arranged below the intake manifold5on the right side surface of the cylinder block3. Further, the engine1includes injectors14for four cylinders. Each of the injectors14has a fuel injection valve of electromagnetic-controlled type. By controlling the opening/closing of the fuel injection valves of the injectors14, the high-pressure fuel in a common rail is injected from the injectors14to the respective cylinders of the engine1.

On the front surface side of the cylinder block3, a cooling water pump15for supplying cooling water is arranged. The rotational power of the crankshaft2drives the cooling water pump15along with the cooling fan8, through the cooling fan V-belt. With the driving of the cooling water pump15, the cooling water in a radiator (not shown) mounted to the work machine is supplied to the cylinder block3and the cylinder head4and cools the engine1. Then the cooling water having contributed to the cooling of the engine1returns to the radiator. Above the cooling water pump15, an alternator16is arranged.

The intake manifold5is connected to an intake throttle member17. 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 manifold5through the intake throttle member17, and then supplied to the respective cylinders of the engine1.

In an upper portion of the intake manifold5, an EGR device18is arranged. The EGR device18is a device that supplies part of the exhaust gas of the engine1(EGR gas from the exhaust manifold6) to the intake manifold5, and includes an EGR pipe21connecting to the exhaust manifold6through an EGR cooler20and an EGR valve case19that communicates the intake manifold5to the EGR pipe21.

A downwardly-open end portion of the EGR valve case19is bolt-fastened to an inlet of the intake manifold5protruding upward from the intake manifold5. Further, a rightwardly-open end portion of the EGR valve case19is coupled to an outlet side of the EGR pipe21. By adjusting the opening degree of the EGR valve member (not shown) in the EGR valve case19, the amount of EGR gas supplied from the EGR pipe21to the intake manifold5is adjusted. The EGR valve member is driven by an actuator22attached to the EGR valve case19.

In the intake manifold5, the fresh air supplied from the air cleaner to the intake manifold5through the intake throttle member17is mixed with the EGR gas (part of exhaust gas from the exhaust manifold6) supplied from the exhaust manifold6to the intake manifold5through the EGR valve case19. As described, by recirculating part of the exhaust gas from the exhaust manifold6to the engine1through the intake manifold5, the combustion temperature is lowered and the emission of nitrogen oxide (NOX) from the engine1is reduced.

The EGR pipe21is connected to the EGR cooler20and the EGR valve case19. The EGR pipe21includes a first EGR pipe21aarranged on the right side of the cylinder head4, a second EGR pipe21bformed in a rear end portion of the cylinder head4, and a third EGR pipe21carranged on the left side of the cylinder head4.

The first EGR pipe21ais generally an L-shaped pipe. The first EGR pipe21ahas its inlet side coupled to an outlet side of the second EGR pipe21b, and has its outlet side coupled to the EGR valve case19.

The second EGR pipe21bis formed in such a manner as to penetrate through the rear end portion of the cylinder head4in the left-and-right directions as shown inFIG.2. In other words, the second EGR pipe21band the cylinder head4are integrally formed. The second EGR pipe21bhas its inlet side coupled to an outlet side of the third EGR pipe21c, and has its outlet side connected to the inlet side of the first EGR pipe21a.

The third EGR pipe21cis formed inside the exhaust manifold6. In other words, the third EGR pipe21cand the exhaust manifold6are integrally formed. With the third EGR pipe21cand second EGR pipe21bintegrally formed with the exhaust manifold6and the cylinder head4, respectively, the space needed can be saved, and the pipes less likely receive an external impact.

FIG.3is an exploded perspective view of the exhaust manifold6and an EGR cooler20.FIG.4A,FIG.4BandFIG.4Care a diagram providing a top view, a front view, and a bottom view of the exhaust manifold6, respectively. The exhaust manifold6includes an aggregate part61configured to aggregate the exhaust gas from exhaust ports of the cylinders to one place and discharge the exhaust gas, an attachment part62protruding downward from the rear end of the aggregate part61, and an EGR pipe unit63extended rearward from the attachment part62. The third EGR pipe21cis formed in the EGR pipe unit63.

The attachment part62of the exhaust manifold6includes a first opening62aconfigured to supply EGR gas from the exhaust manifold6to the EGR cooler20, and a second opening62bconfigured to supply EGR gas from the EGR cooler20to the third EGR pipe21c. The first opening62aand the second opening62bare aligned in the front-and-rear direction. The attachment part62has therein an EGR gas draw-out passage62ccommunicating the aggregate part61with the first opening62a.

The EGR cooler20has a substantially quadrangular prism shape extended in the up-and-down direction. The EGR cooler20is attached to the downwardly protruding attachment part62provided to the exhaust manifold6. An upper end of the EGR cooler20is bolt-fastened to the attachment part62. In the present embodiment, the exhaust manifold6is cantilevered in such a manner as to be parallel (standing posture) to the axis direction of the cylinders (not shown).

The upper end of the EGR cooler20has a supply port20ato which the EGR gas is supplied from the exhaust manifold6, and a discharge port20bfrom which the EGR gas is discharged to the third EGR pipe21c. The supply port20aand the discharge port20bare aligned in the front-and-rear direction. The supply port20ais coupled to the first opening62aof the exhaust manifold6. The discharge port20bis coupled to the second opening62bof the exhaust manifold6. Further, inside the EGR cooler20, a U-shape path connecting to the supply port20aand the discharge port20bis formed. The EGR gas, after traveling downward from the supply port20amakes a U-turn to travel upward, towards the discharge port20b. Thus, the EGR gas supplied from the supply port20ato the EGR cooler20is discharged from the discharge port20bthrough the U-shaped path.

Further, the EGR cooler20overlaps with a gear case cover23in a rear view, as shown inFIG.2. The gear case cover23is arranged to face the flywheel housing9, and covers a cam gear (not shown) together with the flywheel housing9. Covering the cam gear with the gear case cover23and the flywheel housing9blocks the sound. Therefore, gear noise can be reduced. Since the EGR cooler20overlaps with the gear case cover23, the EGR cooler20is protected from an external impact (particularly, from an impact from the rear side).

FIG.5AandFIG.5Bschematically provide a cross-sectional view of the EGR cooler20, andFIG.5Ashows a state where a switching valve201is closed, whereasFIG.5Bshows a state where the switching valve201is open. The arrow in the diagram shows the flow of the EGR gas.

The EGR cooler20includes a cooling unit20cconfigured to cool the EGR gas and the switching valve201configured to control an inflow of the EGR gas to the cooling unit20c. The cooling unit20cis arranged below the EGR cooler20. By driving the cooling water pump15, the cooling water is supplied around the cooling unit20c, thereby cooling the EGR gas passing through the cooling unit20c.

When the temperature of the EGR gas from the exhaust manifold6is not more than a predetermined temperature, the switching valve201closes the passage to the cooling unit20cas shown inFIG.5A, and blocks the inflow of the EGR gas to the cooling unit20c. This way, the EGR gas is not supplied to the cooling unit20cwhile the temperature of the EGR gas is low. Therefore, a quick warm up can be possible. On the other hand, when the temperature of the EGR gas from the exhaust manifold6is higher than the predetermined temperature, the switching valve201opens the passage to the cooling unit20cas shown inFIG.5B, and allows the inflow of the EGR gas to the cooling unit20c. This way, the EGR gas is supplied to the cooling unit20c, while the temperature of the EGR gas is high. Therefore, the temperature of the EGR gas can be appropriately controlled.

An embodiment of the present invention has been described with reference to the drawings. It, however, should be considered that specific configurations of the present invention are not limited to this embodiment. The scope of this invention is indicated by the range of patent claims as well as the description of the enforcement form described above, as well as the range of patent claims and even meaning and all changes within the range.

REFERENCE SIGNS LIST

1engine3cylinder block4cylinder head5intake manifold6exhaust manifold18EGR device20EGR cooler20ccooling unit21EGR pipe62attachment part201switching valve