Monoblock internal combustion engine

Abstract

We provide internal combustion engines that offer excellent practical application and superior catalyst temperature control. [Solution] The internal combustion engine is a monoblock type internal combustion engine having a main body block in which a cylinder block section 1 and a cylinder head section 2 are integrally cast, and a catalyst housing section 25 into which a catalyst unit 24 can be inserted and removed is integrally formed with the main body block. The upper part of the catalyst housing section 25 is a dome section 34, and a dome section cooling water jacket 39 communicating with the head section cooling water jacket 18 is formed on the dome section 34, and a catalyst cooling water jacket 40 is formed on the catalyst housing section 25. The catalyst unit 24 is fixed to the catalyst housing section 25 with bolts 38. By switching the cooling water jackets 39 and 40 between a water-flowing state and a water-drying state, it is possible to achieve both early activation of the catalyst 26 and prevention of excessive temperature rise.

Description

Technical Field

[0001] The present invention relates to a monoblock internal combustion engine in which a cylinder head and a cylinder block are integrated.

Background Art

[0002] A monoblock internal combustion engine in which a cylinder head and a cylinder block are integrally cast is disclosed in, for example, Patent Document 1, which is a prior application of the applicant of the present application. Integrating the cylinder head and the cylinder block has advantages such as suppressing the labor of assembly and eliminating the problem of sealing between the cylinder head and the cylinder block.

[0003] On the other hand, in an internal combustion engine, there is a demand for exhaust gas purification regardless of the structure of the engine body. Therefore, in a gasoline engine, a three-way catalyst is used as a purification means. The catalyst is usually supported on a sintered body of a ceramic-based honeycomb structure, wrapped with an inorganic buffer material, and further incorporated in a metal catalyst case. The catalyst case generally has a straight body portion surrounding the catalyst, an upper cone portion fixed to the upper end of the body portion, and a lower cone portion fixed to the lower end of the body portion. The upper cone portion is fixed to an exhaust manifold, an exhaust side surface of a cylinder head, or a turbine housing of an exhaust turbocharger.

[0004] That is, the catalyst case is configured to be retrofitted and is also surrounded by an insulator because it becomes hot. Patent Documents 2 and 3 disclose arranging a catalyst in a catalyst chamber provided in a cylinder block in a general internal combustion engine in which a cylinder head and a cylinder block are separated. Patent Document 2 also discloses providing a cooling water jacket so as to surround the catalyst.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] Catalysts have the characteristic of not becoming active unless they are heated to a certain temperature. Therefore, when operating an internal combustion engine, it is necessary to quickly heat up the catalyst after starting the engine. In particular, when starting in a low-temperature environment, it is strongly required to quickly heat up the catalyst in order to purify the exhaust gas.

[0007] On the other hand, catalysts have the characteristic that their function deteriorates if they get too hot. Therefore, once steady-state operation is reached in which coolant circulates to the radiator, it is preferable to cool the catalyst to prevent it from getting too hot. In the case of a separate catalyst case, methods such as surrounding it with an insulator or cooling it with airflow are used to prevent heat damage, but from the standpoint of preventing heat damage, it can be said that forcibly cooling the catalyst with coolant, as in Patent Document 2, is preferable.

[0008] While there are advantages to integrating the catalyst into the cylinder block, Patent Documents 1 and 2 show that the catalyst chamber is narrowed at the top and bottom, making it unclear how the catalyst is fitted. Therefore, its feasibility is questionable. Furthermore, Patent Document 3 shows exhaust gas being guided to the catalyst chamber by an external exhaust manifold, and Patent Document 2 appears to be similar. However, using such an aftermarket exhaust manifold not only complicates the structure and increases costs and weight, but also presents problems such as the extra effort required to prevent sealing failures.

[0009] The present invention was made against this backdrop, and focuses on monoblock internal combustion engines such as those described in Patent Document 1, aiming to improve an exhaust gas purification system using a catalyst while taking advantage of the characteristics of monoblock internal combustion engines. [Means for solving the problem]

[0010] The present invention is, "It has a main body block in which the cylinder head and cylinder block are integrated, and a catalytic converter unit that purifies the exhaust gas discharged from the cylinder head." This is aimed at monoblock internal combustion engines. "The main body block includes a catalyst housing section with a downward-facing opening into which the catalyst unit is fitted from below, an exhaust gas collection passage for introducing exhaust gas into the catalyst housing section from above, and a catalyst cooling water jacket surrounding at least the upper part of the catalyst housing section." It possesses the following characteristics.

[0011] The present invention can be implemented in various ways. As one example, claim 2 states: "The main body block has a plurality of cylinder bores formed in it via a bore-interval, and the catalyst housing is formed such that its centerline is located to the side of the bore-interval," Between the bore section and the catalyst housing section, an oil drain hole is provided to allow oil collected in the internal space of the cylinder head to flow down into the oil pan. It possesses the following characteristics.

[0012] In the present invention, it is also possible to provide a cooling water jacket for cooling the upper part of the cylinder bore. It is preferable to provide a cooling water jacket for the cylinder head for cooling the upper part of the cylinder bore and the exhaust port (collection port), but it is preferable that the cooling water jacket for cooling the upper part of the cylinder bore communicates with the cooling water jacket provided on the cylinder head.

[0013] The crankcase is fixed to the underside of the main block, but it is preferable that the catalytic converter housing is not blocked by the crankcase. In other words, a structure that allows the catalytic converter unit to be inserted into and removed from the catalytic converter housing while the crankcase is fixed is preferable. [Effects of the Invention]

[0014] In the present invention, the catalyst housing is open at the bottom of the main body block, allowing the catalyst unit to be inserted into and removed from below. Therefore, there are no practical problems, and it is highly practical. As described above, adopting a configuration in which the catalyst housing is not blocked by the crankcase is preferable because it facilitates the assembly of the internal combustion engine and the replacement of the catalyst unit.

[0015] Furthermore, in the present invention, since the exhaust gas collection passage that directs exhaust gas into the catalyst storage section is integrally formed with the main body block, the number of components can be significantly reduced, thereby lowering costs, and heat dissipation can be suppressed, contributing to the rapid temperature rise of the catalyst during startup.

[0016] On the other hand, during steady-state operation after warm-up, cooling the catalyst housing with coolant prevents excessive temperature rise of the catalyst, thus maintaining high exhaust gas purification performance. Furthermore, since the catalyst unit can be forcibly cooled with coolant, an insulator is unnecessary, and therefore, heat damage can be suppressed while simplifying the structure.

[0017] Furthermore, in order to quickly raise the temperature of the catalyst, it is preferable to disable the function of the catalyst cooling water jacket at least during startup and warm-up. This can be addressed, for example, by configuring the water pump to be electrically operated so that the entire main block is not cooled until the internal combustion engine reaches a steady temperature, or by using a system in which the water pump is driven by the crankshaft, but a clutch is installed in the path that transmits power from the crankshaft to the water pump so that the water pump is not driven until the internal combustion engine reaches a predetermined temperature.

[0018] A remote switching valve can be installed to turn the water flow to the catalytic converter's cooling water jacket on and off, so that water does not flow to the catalytic converter's cooling water jacket until the catalyst reaches its activation temperature. In this case, water can still flow to the cylinder head's cooling water jacket, so if the cooling water is used as the heat source for the in-vehicle heater in an automobile's internal combustion engine, the cooling water heater can be used immediately after starting the internal combustion engine.

[0019] Since the area between the bores and the catalyst storage part becomes a state where heat accumulates, if an oil drain passage is provided between the inter-bore part and the catalyst storage part as in claim 2, there is an advantage that the oil can be heated up early to reduce mechanical loss. On the other hand, since at least the upper part of the catalyst storage part is surrounded by a cooling water jacket, after shifting to steady operation, the oil can be cooled with cooling water to prevent excessive temperature rise.

[0020] In addition to the configuration of claim 2, if a cooling water jacket surrounding the cylinder bore is provided, the oil can be cooled from both the cooling water jacket for the cylinder bore and the cooling water jacket for the catalyst, so there is an advantage that the effect of preventing excessive temperature rise can be further improved.

[0021] The exhaust gas that has passed through the catalyst needs to be sent to the exhaust pipe. However, as in the embodiment, if the catalyst unit is blocked at the lower cone part from below and the lower cone part is fixed to the lower end of the main body block with bolts, the catalyst unit can be held in a non-falling state with a simple structure.

Brief Description of the Drawings

[0022] [Figure 1] It is a longitudinal sectional view cut at the center position of the cylinder bore, showing an embodiment. [Figure 2] It is a longitudinal sectional view cut at the location of the inter-bore part, showing the entire inter-bore part. [Figure 3] It is a longitudinal sectional view cut at the location of the inter-bore part, showing the entire catalyst storage part. [Figure 4] It is a schematic plan view showing the relationship between the exhaust port and the catalyst storage part. (A) is a view in the case of two cylinders, and (B) is a view in the case of three cylinders.

Modes for Carrying Out the Invention

[0023] Next, embodiments of the present invention will be described based on the drawings. This embodiment is applied to a multi-cylinder internal combustion engine for vehicles (automobiles). In the following, the terms front and rear and left and right will be used to specify directions, where the front and rear direction is the direction of the crank axis, and the left and right direction is the direction perpendicular to the crank axis and the cylinder bore axis.

[0024] (1).Basic structure The internal combustion engine, as its basic components, comprises a monoblock-type main block in which the cylinder block section 1 and the cylinder head section 2 are integrated, a crankcase section 4 fixed to the lower surface of the cylinder block section 1 by a group of bolts 3, and an oil pan (not shown) fixed to the lower surface of the crankcase section 4 by a group of bolts. As shown in Figure 2, the crankshaft 6 is rotatably held in the crankcase section 4 via a crank cap 5. The main block and the crankcase section 4 are cast or die-cast products made of aluminum.

[0025] Since the internal combustion engine of this embodiment is a multi-cylinder engine having multiple cylinder bores 7, the cylinder block 1 has front and rear end walls and one or more inter-bore sections 8. The crankcase 4 is similar, having front and rear end walls (not shown) and intermediate walls 9 corresponding to the inter-bore sections 8. The front and rear walls and the intermediate wall 9 form an upper bearing section 9a, and the crankshaft 6 is rotatably held via the upper bearing section 9a, the crank cap 5, and the bearing metal.

[0026] The cylinder head portion 2 has pent-roof-shaped recesses 11 that constitute the combustion chamber, corresponding to each cylinder bore 7, and an ignition hole 12 for mounting a spark plug (not shown) is opened in each recess 11. An iron liner 7a is cast into the cylinder bore 7, but the liner 7a is optional. The piston is denoted by reference numeral 10.

[0027] The cylinder head 2 further has a pair of intake ports 14 and exhaust ports 15, one at the front and one at the rear, facing each recess 11, on both the left and right sides of the crank axis. The outlet of the intake port 14 is opened and closed by an intake valve 16, and the inlet of the exhaust port 15 is opened and closed by an exhaust valve 17. The camshaft is omitted. A head cover (not shown) is also fixed to the cylinder head 2.

[0028] An intake manifold (not shown) is fixed to the intake side of the cylinder head section 2, where the intake port 14 is open. Although not shown, fuel injection injectors are arranged in the cylinder head section 2 at locations corresponding to each intake port 14. A head coolant jacket 18 is formed in the cylinder head section 2 to cool the upper part of the cylinder bore 7 and the area where the exhaust port 15 is located. A block coolant jacket 19 is also formed at the upper end of the cylinder block section 1, and the two are in communication with each other.

[0029] The cooling water jacket 19 of the block section surrounds only the upper end of the cylinder bore 7. Therefore, there is almost no forced cooling of the cylinder block section 1. This is because the heat transfer between the cylinder head section 2 and the cylinder block section 1 is good, and the cooling effect of the cylinder head section 2 directly affects the cylinder block section 1.

[0030] The cylinder block has an upper deck section 20, an intermediate deck section 21, and a lower deck section 22 that protrude outward, with the lower deck section 22 fixed to the crankcase section 4. Although the cylinder head section 2 is shown as a single element in the diagram, it is also possible to separate the cylinder head section 2 into an upper head section and a lower head section, and integrate the lower head section with the cylinder block section 1 (in this case, the camshaft can be rotatably held by the upper and lower head sections).

[0031] (2) Exhaust structure and catalytic converter unit The exhaust side portion of the main block is formed with a catalyst housing section 25 that opens downwards, allowing the catalyst unit 24 to be inserted and removed from below. The catalyst unit 24 consists of a catalyst 26 on which catalytic elements are supported on a cylindrical porous support such as a ceramic honeycomb material, an inorganic buffer material 26a such as glass wool that holds the catalyst 26 in a way that prevents it from falling, and a cylindrical case 27 that holds the inorganic buffer material 26a in a way that prevents it from falling. Therefore, the catalyst 26 is held inside the case 27 via the inorganic buffer material 26a in a way that prevents it from falling.

[0032] The case 27 is made of a metal plate such as stainless steel, and a cylindrical upper end portion 28b formed on the metal lower cone portion 28 is tightly fitted to its lower end from the outside. A tapered support ring 29 is welded to the tapered portion of the lower cone portion 28, and as shown in Figure 3, a flange piece 30 is provided protruding outward from the part of the support ring 29 opposite to the cylinder block portion 1. An EGR pipe 31 is connected to the lower cone portion 28.

[0033] The exhaust pipe 32 is connected to the straight joint portion 28a at the lower end of the lower cone portion 28. However, in order to avoid interference with the crankcase portion 4, the joint portion 28a is offset away from the cylinder block portion 1 and is also inclined downward so as to move away from the cylinder block portion 1.

[0034] The catalyst housing 25 is basically formed in a cylindrical shape corresponding to the case 27 of the catalyst housing 25. Its lower end is integrally connected to the lower deck portion 22 of the cylinder block portion 1, and its upper end is integrally connected to a dome portion 34 that widens downwards. The inside of the dome portion 34 is an exhaust manifold space 35 that evenly diffuses exhaust gas and releases it to the catalyst 26.

[0035] A bracket projection 36 is formed at the lower end of the catalyst housing 25, protruding on the side opposite to the cylinder block 1. The flange piece 30 of the support ring 29 is fixed to the lower surface of the bracket projection 36 with a bolt 38. This holds the case 27 in place, preventing it from falling.

[0036] Alternatively, a tongue similar to the flange piece 30 can be welded to the lower cone section 28, and the tongue can be fixed to the bracket projection 36 with a bolt 38. Alternatively, the flange piece 30 can be fixed to the bracket projection 36 with a bolt 38 via an elastic washer. In this case, the thermal expansion of the case 27 can be absorbed by the elastic washer, preventing damage or cracking of the catalyst housing section 25 due to thermal expansion of the case.

[0037] Although not shown in the diagram, a sealing material is interposed between the upper end of the case 27 constituting the catalyst unit 24 and the dome portion 34. Therefore, exhaust gas leakage does not occur. It is preferable to make the seal from a material that can be elastically compressed and deformed, as this can absorb the thermal expansion of the case 27. It is also possible to expose the case 27 slightly above the catalyst 26, while forming an annular groove in the cylinder head portion 2 into which the exposed portion of the case 27 fits, and placing a sealing ring at the upper end of the annular groove.

[0038] The upper end portion 28b of the lower cone portion 28 is cylindrical and holds the lower end of the case 27. However, since the upper end portion 28b of the lower cone portion 28 is fitted into a large-diameter portion formed at the lower end of the catalyst housing portion 25, the case 27 can be tightly fitted or positioned close to the inner circumferential surface of the catalyst housing portion 25. Therefore, the catalyst unit 24 is firmly held in the catalyst housing portion 25 without any looseness, even if it is fixed with only one bolt 38.

[0039] A dome-shaped cooling water jacket 39 is formed in the dome-shaped section 34, communicating with the head-shaped cooling water jacket 18, and a catalytic converter cooling water jacket 40 is formed in an annular shape on the upper part of the catalytic converter housing section 25. The catalytic converter cooling water jacket 40, the dome-shaped cooling water jacket 39, and the head-shaped cooling water jacket 18 are all in communication with each other. The catalytic converter cooling water jacket 40 is formed in the upper half of the catalytic converter housing section 25, but its position (height) can be arbitrarily set according to the heating characteristics of the catalytic converter unit 24.

[0040] The dome-shaped cooling water jacket 39 is formed in a bowl shape to surround the exhaust manifold space 35, and the upper and lower sections separated by the dome-shaped cooling water jacket 39 are connected by multiple bridges (not shown) that penetrate the dome-shaped cooling water jacket 39. A mounting base 41 for attaching sensors such as an O2 sensor is formed in the dome section 34 at a position far from the cylinder head section 2.

[0041] Each exhaust port 15 is connected to the exhaust manifold space 35 of the dome section 34. However, since the exhaust manifold space 35 is separated from the cylinder bore 7, as can be seen from Figure 4, each exhaust port 15 is positioned to converge into the manifold port 42 that opens into the exhaust manifold space 35.

[0042] The oil used for lubricating the camshaft and other components accumulates at the bottom of the cylinder head section 2. As shown by the dashed line in Figure 3, it is possible to provide an oil drain hole 43 in the area between the bore section 8 and the catalyst housing section 25 of the cylinder block section 1 to allow the oil accumulated in the cylinder head section 2 to flow down into the oil pan. The oil drain hole 43 penetrates the intermediate wall of the crankcase section 4 and opens into the oil pan. In Figure 3, the oil drain hole 43 passes through the cavity of the cylinder block section 1, but it can be formed in a state enclosed by a cylindrical section, or formed in a boss section integrally provided in the catalyst housing section 25 or the bore section 8.

[0043] (3) Summary As described above, this embodiment has the above configuration, and since the catalyst unit 24 is fitted from below into the catalyst housing 25 which is integrally provided with the main body block, there are no manufacturing problems. Furthermore, since the case 27 of the catalyst unit 24 is tightly housed in the catalyst housing 25, vibration is reliably eliminated, contributing to the suppression of vibration in the internal combustion engine. Moreover, since the catalyst unit 24 is fitted into the catalyst housing 25 without any looseness, the catalyst unit 24 can be securely fixed with a single bolt 38. Therefore, the ease of assembly is improved and it has excellent adaptability to actual machines.

[0044] In this embodiment, the catalyst unit 24 can be built into the cylinder block 1, minimizing the path of exhaust gas to the catalyst. Combined with the fact that the manifold passage is built into the cylinder head 2, resulting in very little heat dissipation, the catalyst 26 can be heated up quickly even when starting in cold environments. Therefore, exhaust gas can be properly purified.

[0045] It is preferable not to circulate water through the catalytic converter coolant jacket 40 until the catalytic converter reaches its activation temperature after the internal combustion engine has started. This can be achieved by using a separate cooling system for the catalytic converter coolant jacket 40 and controlling the water flow to the jacket 40 by switching a valve, or by employing an electric water pump to reduce the overall cooling of the internal combustion engine until the catalytic converter reaches its activation temperature. Stopping the circulation of coolant throughout the engine also contributes to reducing mechanical losses due to the rapid temperature rise of the oil.

[0046] During steady-state operation after the warm-up period, the catalytic converter cooling water jacket 40 (and other cooling water jackets) can be circulated to prevent the catalytic converter 26 from becoming excessively hot and thus reducing its activation. In this embodiment, the catalytic converter housing 25 is a complete cylindrical body that covers the entire catalytic converter unit 24, but if heat dissipation is required, it is also possible to provide windows (heat dissipation holes) in the catalytic converter housing 25. It is also possible to hold the catalytic converter unit 24 only at its upper and lower ends in the catalytic converter housing 25, forming an air layer between the upper and lower holding parts. In this case, heat dissipation from the crankcase 4 to the catalytic converter housing 25 can be suppressed, which further contributes to faster temperature rise.

[0047] As shown by the dashed center line O1 in Figure 3, it is also possible to tilt the catalyst unit 24 with respect to the cylinder bore axis O2 such that its upper part approaches the cylinder head 2 and its lower part moves away from the cylinder block 1. In this case, the catalyst unit 24 can be brought closer to the cylinder bore 7 while preventing interference with the crankcase 4, resulting in a more compact and lightweight design, as well as allowing the catalyst 26 to heat up even faster by reducing the exhaust gas flow distance.

[0048] Although embodiments of the present invention have been described above, the present invention can be implemented in various other ways. For example, in the illustrated embodiment, the lower end of the catalyst storage section 25 is aligned with the lower end of the cylinder block section 1, but the position of the upper and lower ends of the catalyst storage section can be selected according to the length of the catalyst unit, and therefore the lower end of the catalyst storage section may be positioned above or below the lower end of the cylinder block section 1.

[0049] As a means of securing the catalyst unit 24, it is also possible to press the case with screws that are screwed into the catalyst housing 25 from the side. Alternatively, it is also possible to provide a nut portion with a sideways opening in the case and screw a bolt that passes through the catalyst housing into the nut portion. The catalyst unit can also be press-fitted into the catalyst housing. [Industrial applicability]

[0050] The present invention can be implemented in a monoblock internal combustion engine in which exhaust gases are purified by a catalyst. Therefore, it is industrially applicable. [Explanation of Symbols]

[0051] 1. Cylinder block section 2 Cylinder head section 4. Crankcase section 6 Crankshaft 7 Cylinder bore 8 Bore section 9 Intermediate wall 10 pistons 14 Intake Ports 15 Exhaust Ports 18. Head unit coolant jacket 19. Cooling water jacket for the block section 24 Catalyst Unit 25 Catalyst storage section 26 Catalyst 27 Cases (Holders) 28 Lower cone section 29 Support Ring 30 flange pieces 34 Dome section 35 Exhaust manifold space 39. Dome section cooling water jacket 40 Catalytic converter cooling water jacket 42 Assembly Ports 43 Oil Pitfalls

Claims

1. It has a main body block in which the cylinder head and cylinder block are integrated, and a catalytic converter unit that purifies the exhaust gas discharged from the cylinder head. The main body block includes a catalyst housing section with a downward opening into which the catalyst unit is fitted from below, an exhaust gas collection passage for introducing exhaust gas into the catalyst housing section from above, and a catalyst cooling water jacket surrounding at least the upper part of the catalyst housing section. Monoblock internal combustion engine.

2. The main body block has a plurality of cylinder bores formed in between the bores, and the catalyst housing is formed such that its centerline is located to the side of the bore section. Between the bore section and the catalyst housing section, an oil drain hole is provided to allow oil collected in the internal space of the cylinder head to flow down into the oil pan. A monoblock internal combustion engine as described in claim 1.

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