Internal combustion engine

Abstract

To provide a technology that can cope with an increase in size of a catalyst case without changing the design of a cylinder block.SOLUTION: A lower bracket 8 is fixed to a lower part of a catalyst case 6 via a joint exhaust pipe 9, and a protruding portion 8b is fixed and supported to a cylinder block 1 via a first stay 20 and a second stay 21. The first stay 20 is fixed to a boss portion 22 provided on the cylinder block 1 with a first bolt 23, and the second stay 21 has an upper end fixed to the first stay 20 with a second bolt 28 and a lower end fastened to the lower bracket 8 with a stud bolt 29 and a nut 30. In a side view, the first bolt 23 is hidden behind the catalyst case 6, but the second bolt 28 and the stud bolt 29 are exposed to the outside of the catalyst case 6, so that an existing boss part 22 can be used while being fastened with a wrench, and the enlarged catalyst case 6 can be supported.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an internal combustion engine in which a catalyst case is interposed in an exhaust system.

Background Art

[0002] In an internal combustion engine (gasoline engine) for automobiles or the like, a three-way catalyst is used for purifying exhaust gas. The three-way catalyst is built into a catalyst case, and the upper end of the catalyst case is attached to a cylinder head or an exhaust turbocharger, and the lower part is supported by an engine body such as a cylinder block via a bracket.

[0003] Regarding the support structure at the lower part of the catalyst case, a lower bracket is fixed to the lower end of the catalyst case or an exhaust pipe connected thereto by welding, and the lower bracket and the cylinder block are fastened by a support device. As an example of the support device, one stay whose one end is fastened to the cylinder block with bolts and the other end is fastened to the lower bracket with bolts (and nuts) is used.

[0004] The reason for interposing the stay instead of directly fixing the lower bracket to the cylinder block is to absorb the mounting error during the assembly of the internal combustion engine and to absorb the thermal expansion of the catalyst case. Therefore, as an assembly procedure, the stay is lightly fastened to the cylinder block with bolts, and the lower bracket and the stay are lightly fastened, and after firmly fixing the catalyst case to the cylinder head or the exhaust turbocharger, the stay is firmly fastened to the cylinder block and the lower bracket and the stay are firmly fastened.

[0005] The bolts and nuts are fastened using a driver tool. However, since the operator works standing on the exhaust side surface of the cylinder block, the fastening parts of the stay and the lower bracket are designed to be exposed outside the catalyst case when viewed from the operator with the catalyst case set in place.

[0006] The problem here is that, due to the demand for improved exhaust gas purification performance, catalytic converter cases tend to become larger. When the catalytic converter case becomes larger, there is a concern that the fastening position of the stay to the cylinder block will be hidden by the catalytic converter case, making it impossible to fasten the stay to the cylinder block. One could argue that this can be resolved by changing the mounting position of the stay to the cylinder block, but this would require a redesign of the cylinder block, which would necessitate changes to the die-cast or cast mold, thus increasing costs.

[0007] On the other hand, Patent Document 1 discloses a support structure for the lower part of the catalytic converter case, in which a base member long in the crank axis direction (front-rear direction) is fixed to the upper end of the oil pan with bolts, and the front and rear ends of the base member are fixed to the lower bracket of the catalytic converter case with front and rear arm members (stays). In Patent Document 1, in a side view perpendicular to the exhaust side of the engine body, the fastening parts between the base member and the front and rear arm members, and the fastening parts between the lower bracket and the front and rear arm members are exposed on the outside of the catalytic converter case. Furthermore, the arm members are bent in a V-shape so as to be recessed toward the center of the lower bracket, and in a side view, the fastening parts of the base member to the oil pan are located further outward from the front and rear than the fastening parts between the lower bracket and the arm members. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 6984354 [Overview of the project] [Problems that the invention aims to solve]

[0009] Patent Document 1 requires two arm members, which inevitably increases costs and weight, and also makes the fastening process time-consuming. Furthermore, the base member is long enough that both its front and rear ends protrude outside the catalytic converter case when viewed from the side, and is fastened to the oil pan with multiple bolts, which further increases costs, weight, and the effort required for fastening.

[0010] Furthermore, as described in Patent Document 1, if the catalytic converter case becomes larger and the fastening parts between the base and the oil pan, and between the lower bracket and the arm member, are hidden by the catalytic converter case in a side view, there is a risk that fastening work will become impossible. To address this, it is necessary to increase the front-to-back length of the base member so that the fastening parts between the base and the oil pan, and between the lower bracket and the arm member, are located on the front and rear outer sides of the catalytic converter case in a side view. However, in this case, the design of the oil pan must be changed, which will increase costs.

[0011] The present invention was made to improve this current situation. [Means for solving the problem]

[0012] The invention of claim 1 is, "The engine body includes the cylinder block, cylinder head, and oil pan, and is located on the exhaust side of the engine body." Long and narrow Catalyst case and The EGR pipe has a vertically elongated section that is long in the vertical direction, with its lower end connected to the lower part of the catalyst case and its upper end connected to the cylinder head. of Yes, The upper end of the catalytic converter case is fixed to the cylinder head or exhaust turbocharger, while the lower end of the catalytic converter case is fixed to a lower bracket directly or via the exhaust pipe. ite The lower bracket is fixed to the engine body via a support device. Ori , The support device is attached to the engine body. 1 The first stay fixed with a screw, and the first stay It is fastened to the lower bracket with a second screw and also fastened to the lower bracket with a third screw. It consists of a second stay, and in a side view taken from a direction perpendicular to the exhaust side of the engine body, First screw It overlaps with the catalyst case, The second and third screws areIt is arranged so as not to overlap with the catalyst case An internal combustion engine, The first to third screws are positioned so that they can be rotated with a wrench from a direction opposite to the exhaust side of the engine body. Furthermore, the first and second stays are positioned such that when the EGR pipe undergoes thermal expansion, the first stay receives an external force that causes it to rotate in the screwing direction of the first screw via the second stay. 」 It has the following structure.

[0013] The invention of claim 2 is, 「 The engine body includes a cylinder block, a cylinder head, and an oil pan, and a catalytic converter case located on the exhaust side of the engine body. The upper end of the catalytic converter case is fixed to the cylinder head or exhaust turbocharger, while the lower end of the catalytic converter case is fixed to a lower bracket directly or via the exhaust pipe, and the lower bracket is fixed to the engine body via a support device. The support device comprises a first stay fixed to the engine body with screws, and a second stay fastened to the lower bracket and the first stay with screws. In a side view taken from a direction perpendicular to the exhaust side of the engine body, the fastening portion between the first stay and the engine body overlaps with the catalytic converter case, while the fastening portions between the first stay and the second stay, and between the second stay and the lower bracket, do not overlap with the catalytic converter case. In this basic configuration, 「At the lower end of the exhaust side surface of the cylinder block, a flange-shaped lower rail portion that is long in the crankshaft axis direction is formed, and the first stay is arranged so as to extend in the crankshaft axis direction along the upper surface of the lower rail portion. The first stay has a first fastening portion fastened to the cylinder block and a second fastening portion fastened to the second stay. The first fastening portion is arranged so as to overlap with the catalyst case in the side view, and the second fastening portion is located outside the catalyst case in the side view. Moreover, one end portion of the first stay located on the opposite side of the second fastening portion across the first fastening portion abuts on the lower rail portion of the cylinder block from above.」 It adopts the following structure.

Advantages of the Invention

[0014] In the present invention, since the fastening portion of the first stay with respect to the engine body is hidden behind the catalyst case in the side view, the conventional stay fastening portion (tap hole) can be used as it is. Therefore, it is possible to cope with the enlargement of the catalyst case without changing the design of the engine body, and the cost increase can be suppressed. Compared with Patent Document 1, since the number of members is small, the cost can be significantly reduced, and the deterioration of fuel consumption due to the prevention of weight increase can also be prevented.

[0015] Furthermore, regarding the first stay, since only a part of the first stay is hidden behind the catalyst case in a side view, the length in the front-rear direction is much shorter than that of the base part of Patent Document 1. Also in this regard, it can contribute to cost reduction and weight reduction.

[0016] When the catalyst case increases in size, the distance between the engine body and the lower bracket may change. However, in the present invention, the change in the position of the catalyst case can be absorbed by the second stay. It is also excellent in the function of absorbing mounting errors and has higher flexibility compared to the case where the lower bracket is fastened to one stay. When an EGR pipe is connected to the catalyst case or the exhaust pipe connected thereto, during the assembly of the internal combustion engine, the position of the catalyst case may change in relation to the EGR pipe. However, in the invention of claim 1, 2 In the invention, the change in the position of the catalyst case caused by the EGR pipe can also be firmly absorbed by the second stay.

[0017] Note that the bolts are usually right-handed. However, since the right end portion of the first stay sandwiching the bolt can be stopped from rotating by abutting it against the protruding portion (for example, the lower rail portion) of the engine body, it can be accurately fixed in a predetermined posture by one bolt.

[0018] And usually, an oil pan is fixed to the lower end surface of the cylinder block by a group of bolts. Therefore, a flange-shaped lower rail portion (lower deck portion) is often formed at the lower end of the cylinder block. However, when one end portion of the first stay is abutted against the lower rail portion of the cylinder block from above as in claim 2, the function of pressing the lower rail portion against the oil pan (the integrality between the cylinder block and the oil pan) is improved, which can contribute to the improvement of the rigidity of the entire engine body (power plant). As a result, effects such as vibration suppression can be enjoyed.

Brief Description of the Drawings

[0019] [Figure 1] It is a side view of the main part of the internal combustion engine according to the embodiment. [Figure 2](A) is a perspective view showing the arrangement of the stays, and (B) is a perspective view showing the fastened state. [Figure 3] (A) is a cross-sectional view of IIIA-IIIA in Figure 2(B), and (B) is a cross-sectional view of IIIB-IIIB in Figure 2(B). [Figure 4] This is a perspective view of the stay. [Modes for carrying out the invention]

[0020] (1).Basic structure Next, embodiments of the present invention will be described based on the drawings. These embodiments are applied to an internal combustion engine for an automobile.

[0021] In the following, terms such as front / rear and side view will be used to specify direction. As already mentioned, the front / rear direction is the direction of the crank axis, with the side containing the timing chain and crank pulley (neither of which are shown) being considered the front, and the side where the transmission case is located being considered the rear. The left / right direction is the direction perpendicular to the vertical direction and the crank axis direction. The side view is the view from the left / right direction (perpendicular to the exhaust side).

[0022] The vertical direction is precisely the direction of the cylinder bore axis, but since the internal combustion engine in this embodiment is vertical, the vertical direction is almost the same as the vertical direction (the cylinder bore axis may be slightly tilted forward towards the front of the vehicle body). The direction is indicated as appropriate in the drawings.

[0023] The basic configuration of the internal combustion engine is the same as in conventional engines. As shown in Figures 1 and 2, the engine body comprises a cylinder block 1 with multiple cylinder bores (not shown), a cylinder head 2 fixed to its upper surface, and an oil pan 3 fixed to the lower surface of the cylinder block.

[0024] Although not shown in the diagram, a head cover is fixed to the top surface of the cylinder head 2, and a front cover that covers the timing chain is fixed to the front of the cylinder block 1 and the cylinder head 2. The transmission case described above is fixed on top of the cylinder block 1 and the rear surface of the oil pan 3. In this embodiment, the head cover, front cover, and transmission case can also be considered as components of the engine body.

[0025] As can be seen from Figure 1, the cylinder head 2 of this embodiment is of a type that incorporates an exhaust manifold, and one exhaust outlet 4 is opened on the exhaust side, and a catalytic converter case 6 is connected to this exhaust outlet 4 via an elbow-shaped joint pipe 5 as part of the exhaust passage. The joint pipe 5 is equipped with a flange plate 7, and the flange plate 7 is fixed to the cylinder head 2 by stud bolts and nuts.

[0026] Catalyst case 6 It has a long shape in the vertical direction. The exhaust pipe has a straight section 6a containing a catalyst, an upper cone section 6b that tapers upwards and is integrally provided at the upper end of the straight section 6a, and a lower cone section 6c that tapers downwards and is integrally provided at the lower end of the straight section 6a. A joint exhaust pipe 9 equipped with a lower bracket 8 is integrally provided at the lower end of the lower cone section 6c. Therefore, in this embodiment, the lower bracket 8 is attached to the catalyst case 6 via the joint exhaust pipe 9. The joint exhaust pipe 9 is also exposed below the lower bracket 8, and the main exhaust pipe 10 is connected to the downward-facing exposed portion.

[0027] In this embodiment, the internal combustion engine is mounted in the vehicle in a transverse orientation with the crankshaft positioned longer in the vehicle width direction and the exhaust side facing the front of the vehicle, resulting in a transverse, front-exhaust configuration. The main exhaust pipe 10 passes under the oil pan 3 and extends to the rear of the vehicle. For this reason, the portion of the oil pan 3 under which the main exhaust pipe 10 passes is shallow.

[0028] In a side view, the catalytic converter case 6 is tilted at a slight angle to the vertical, shifting backward as it goes downwards. In a front view, the catalytic converter case 6 is almost parallel to the exhaust side of the cylinder block 1. In a front view, it is also possible to tilt it so that it moves slightly away from the cylinder block 1 as it goes downwards, or in the opposite direction.

[0029] The lower end (upstream end) of the EGR pipe 11, which extracts EGR gas, is connected by welding or the like to the upper part of the lower cone section 6c of the catalytic converter case 6. The lower end of the EGR pipe 11 is connected to the end of the lower cone section 6c furthest from the cylinder block 1, extends outwards to the left and right, then changes direction upwards, and reaches the rear end of the exhaust side of the cylinder head 2.

[0030] Therefore, the EGR pipe 11 has a lower horizontal portion 11a that forms its lower end, and extends upward in a bent, inclined position. Long and narrow It comprises a vertically elongated section 11b and an upper horizontal section 11c connected to the upper end of the vertically elongated section 11b, and a bracket plate 12 fixed to the end of the upper horizontal section 11c is bolted to the cylinder head 2. Therefore, at the rear end of the cylinder head 2, an EGR internal passage communicating with the upper horizontal section 11c is formed in a long position in the left-right direction (direction perpendicular to the plane of the paper). The upper horizontal section 11c is bent into an L shape in plan view.

[0031] A thin plate insulator 13 is fixed to the catalyst case 6, covering the straight section 6a, the upper cone section 6b, and the joint pipe 5 from the front. The insulator 13 is fixed to an upper base 14 provided on the joint pipe 5 and a lower base 15 provided on the straight section 6a. The lower end of the insulator 13 extends to the lower end of the straight section 6a.

[0032] Flange-shaped lower rail sections (lower deck sections) 16 are formed at the lower ends of the exhaust and intake sides of the cylinder block 1, and the flange 17 of the oil pan 3 is fixed to the lower rail sections 16 by a group of bolts (not shown). In addition, an upper rail section (upper deck section) 18 is formed at the upper end of the cylinder block 1.

[0033] Although not explicitly shown in the drawings, the exhaust and intake sides of the cylinder block 1 basically reflect the plan view shape of the cylinder, and the exhaust and intake sides are recessed inward towards the cylinder block 1 in the bore section. Therefore, the upper surface of the lower rail section 16 is curved inward towards the cylinder block 1 in the bore section. As shown in Figure 1, the upper cone section 6b of the catalytic converter case 6 is provided with a sensor seat 19 for mounting an air-fuel ratio sensor or an oxygen concentration sensor.

[0034] (2) Lower support structure of the catalyst case The lower bracket 8 of the catalytic converter case 6 has a disc-shaped portion 8a that surrounds the joint exhaust pipe 9, and a protruding portion 8b that extends from the front of the disc-shaped portion 8a toward the cylinder block 1. The protruding portion 8b has an inclined surface that becomes higher as it approaches the cylinder block 1, and this inclined protruding portion 8b is fixed to the cylinder block 1 via a first stay 20 fixed to the cylinder block 1 and a second stay 21 fixed to the first stay 20. The first stay 20 and the second stay 21 constitute a support device.

[0035] Both stays 20 and 21 are sheet metal parts, and their shape and positional relationship are as shown in Figure 2, for example. Specifically, the first stay 20 is a long strip-shaped plate, positioned so as to overlap the exhaust side of the cylinder block 1 in a prone position and overlap the lower rail portion 16 of the cylinder block 1 from above, with its front and rear intermediate portions fixed to a boss portion 22 formed in the cylinder block 1 with the first bolt 23. In addition, a stopper portion 25 is bent and formed at the rear end of the first stay 20 so as to overlap the lower rail portion 16 of the cylinder block 1 from above and fit into a recess 24 of the cylinder block 1. The recess 24 is, for example, a recess toward the bore section.

[0036] The first stay 20 has a first through hole 26 through which a first bolt 23 is inserted. A fix nut 27 is welded to the back surface of the front part of the first through hole 26, and the upper end of the second stay 21 is fixed to the first stay 20 by a second bolt 28 screwed into the fix nut 27.

[0037] The portion of the first stay 20 behind the first through hole 26 is formed into a narrow section 20a by removing material from its upper end, and the stopper section 25 is formed in this narrow section 20a. The first stay 20 is made of steel plate or stainless steel, but is thick, with a thickness of 5 mm or more, so forming the narrow section 20a makes it easy to bend the stopper section 25.

[0038] The second stay 21 is basically a strip of equal width, and as clearly shown in Figure 3(A), it has an upper part 21a that overlaps the first stay 20, an inclined lower part 21b that overlaps the protruding part 8b of the lower bracket 8 from the side, and an intermediate part 21c that connects the two. A stud bolt 29 is provided protruding laterally from the inclined lower part 21b, and the protruding part 8b of the lower bracket 8 is fixed to the second stay 21 by a nut 30 screwed onto the stud bolt 29. In relation to the claims, in this embodiment, the first bolt 23 is an example of a first thread, the second bolt 28 is an example of a second thread, and the stud bolt 29 and nut 30 are examples of a third thread.

[0039] Since the intermediate section 21c is curved to approach the cylinder block 1, the inclined lower section 21b can be brought closer to the cylinder block 1, allowing the catalytic converter case 6 to be brought as close to the cylinder block 1 as possible. It is also possible to weld a fix nut to the inner surface of the lower end of the second stay 21 and screw a bolt into it, but using a stud bolt 29 as in this embodiment has the advantage of temporarily holding (temporarily supporting) the catalytic converter case 6 to the second stay 21.

[0040] The shapes of both stays 20 and 21 are clearly shown in Figure 4. As shown in Figures 4(C)(D) and 2(A), a relief recess 32 is formed in the part of the second stay 21 behind the second through hole 31 through which the second bolt 28 is inserted, recessed toward the second through hole 31. This relief recess 32 is to avoid interference with the head of the first bolt 23.

[0041] For example, as can be seen from Figure 2(B), in a side view, the first bolt 23 (and boss portion 22 and first through hole 26) is hidden behind the catalytic converter case 6, while the second bolt 28 and stud bolt 29 are exposed in front of the catalytic converter case 6. Therefore, the worker uses a power wrench 33. Rotation operation from the direction opposite to the exhaust side The second bolt 28 and nut 30 can be fastened together. (The same applies to the first bolt, 23.) Therefore, it is possible to attach a large catalyst case 6 while using the boss portion 22 that has been used conventionally.

[0042] To further describe the procedure for installing the catalytic converter case 6, as a prerequisite, the first stay 20 is firmly fixed to the cylinder block 1, while the second stay 21 is hand-tightened so that it overlaps the first stay 20. First, the flange plate 7 of the joint pipe 5 is fitted onto the stud bolts provided on the cylinder head 2, while the protruding portion 8b of the lower bracket 8 is fitted onto the stud bolts 29 of the second stay 21. In this state, the flange plate 7 of the joint pipe 5 is permanently fixed to the cylinder head 2, and then the bracket plate 12 of the EGR pipe 11 is permanently fixed to the cylinder head 2.

[0043] Then, while aligning the positions of the first stay 20 and the second stay 21, both the second bolt 28 and the nut 30 are tightened by rotating them with a wrench 33. At this time, it is preferable to tighten by hand and with a wrench to prevent twisting of the first stay 20 and the second stay 21. For example, due to the precision of the EGR pipe 11 or mounting errors, the front, rear, left, and right positions of the catalytic converter case 6 may not be constant. However, since the second stay 21 is temporarily fastened to the first stay 20 and the lower bracket 8, the position of the second stay 21 can be adjusted to match the position of the catalytic converter case 6, thereby absorbing the differences in the position of the catalytic converter case 6.

[0044] In this embodiment, since the EGR pipe 11 extends in a position intersecting the axis of the catalyst case 6 in a side view, the thermal expansion of the EGR pipe 11 causes the catalyst case 6 to tend to be pushed in the longitudinal direction of the EGR pipe 11 at its lower end, as shown by the dotted arrow 34. As a result, the external force due to the thermal expansion of the EGR pipe 11 acts to rotate the first stay 20 clockwise around the axis of the first bolt 23 (see dotted arrow 35 in Figure 2(B)). In other words, the thermal expansion of the EGR pipe 11 acts in the direction of screwing in the first bolt 23. Therefore, loosening of the first bolt 23 can be prevented.

[0045] Furthermore, since the stopper portion 25 of the first stay 20 abuts against the lower rail portion 16 of the cylinder block 1 from above in a position that crosses it, the lower rail portion 16 is strongly pressed down by the first stay 20, improving the contact with the oil pan 3. As a result, the rigidity of the entire power plant (the entire engine body) can be improved, contributing to vibration suppression.

[0046] In the first stay 20 and the second stay 21, through holes for bolt insertion are formed by punching, but as shown by arrows 36 in Figures 4(B) and 4(D), the punching direction 36 is aligned with the insertion direction of the bolts 23 and 28. In sheet metal processing, burrs tend to occur due to punching, but in this embodiment, the rounded shape 37 caused by the burr is provided on the opening edge on the side where the heads of the bolts 23 and 28 make contact, thereby preventing stress concentration and improving strength.

[0047] Although embodiments of the present invention have been described above, the present invention can be implemented in various other ways. For example, the catalytic converter case can be fixed to the oil pan. Also, the specific shapes of the first stay and the second stay can be appropriately changed according to the actual situation, such as the arrangement of the catalytic converter case. The lower bracket can also be fixed to the lower cone portion of the catalytic converter case. If an exhaust turbocharger is provided, the upper end of the catalytic converter case is connected to the exhaust outlet of the exhaust turbocharger. [Industrial applicability]

[0048] The present invention can be embodied in an internal combustion engine equipped with a catalyst case. Therefore, it is industrially applicable. [Explanation of Symbols]

[0049] 1. Cylinder block, which constitutes part of the engine body. 2. Cylinder head, which constitutes part of the engine body. 3. Oil pan, which is part of the engine body. 5. Joint pipes 6. Catalytic converter case 8 Lower bracket 8b Overhang 9. Exhaust pipe joint 11 EGR pipe 13 Insulators 16. Lower rail section (lower deck section) of the cylinder block 20 1st Stage 21 Second Stage 22 Boss Section 23 First bolt (First screw) 25 Stopper part 28 Second bolt (Second screw) 29 Stud bolts (Third screw) 30 Nut (3rd thread) 33 Wrench (Power Tool)

Claims

1. The engine body includes a cylinder block, cylinder head, and oil pan; a vertically elongated catalytic converter case positioned on the exhaust side of the engine body; and an EGR pipe having a vertically elongated section, the lower end of which is connected to the lower part of the catalytic converter case and the upper end of which is connected to the cylinder head. The upper end of the catalytic converter case is fixed to the cylinder head or exhaust turbocharger, while the lower end of the catalytic converter case is fixed to a lower bracket directly or via the exhaust pipe, and the lower bracket is fixed to the engine body via a support device. The support device comprises a first stay fixed to the engine body with a first screw, and a second stay fastened to the first stay with a second screw and to the lower bracket with a third screw, and in a side view taken from a direction perpendicular to the exhaust side of the engine body, the first screw overlaps with the catalytic converter case, and the second and third screws do not overlap with the catalytic converter case, in an internal combustion engine. The first to third screws are positioned so that they can be rotated with a wrench from a direction opposite to the exhaust side of the engine body. Furthermore, the first stay and the second stay are positioned such that when the EGR pipe undergoes thermal expansion, the first stay receives an external force that causes it to rotate in the screwing direction of the first screw via the second stay. Internal combustion engine.

2. An engine body comprising a cylinder block, a cylinder head, and an oil pan, and a catalytic converter case disposed on the exhaust side of the engine body, The upper end of the catalytic converter case is fixed to the cylinder head or exhaust turbocharger, while the lower end of the catalytic converter case is fixed to a lower bracket either directly or via the exhaust pipe, and the lower bracket is fixed to the engine body via a support device. The support device comprises a first stay fixed to the engine body with screws and a second stay fastened to the lower bracket and the first stay with screws, and in a side view taken from a direction perpendicular to the exhaust side of the engine body, the fastening portion between the first stay and the engine body overlaps with the catalytic converter case, while the fastening portions between the first stay and the second stay and between the second stay and the lower bracket do not overlap with the catalytic converter case in this internal combustion engine. A flange-shaped lower rail portion, elongated in the direction of the crank axis, is formed at the lower end of the exhaust side surface of the cylinder block, and the first stay is arranged to extend in the direction of the crank axis along the upper surface of the lower rail portion. The first stay has a first fastening portion fastened to the cylinder block and a second fastening portion fastened to the second stay, wherein the first fastening portion is arranged to overlap with the catalyst case in the side view, and the second fastening portion is located outside the catalyst case in the side view. Furthermore, one end of the first stay that is located on the opposite side of the second fastening portion, with the first fastening portion in between, abuts against the lower rail portion of the cylinder block from above. Internal combustion engine.

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