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 having a catalyst case interposed in an exhaust system. [Background technology]

[0002] Three-way catalysts are used in internal combustion engines (gasoline engines) for automobiles, etc. to purify exhaust gases. The three-way catalyst is housed in a catalyst case, the upper end of which is attached to the cylinder head or exhaust turbocharger, and the lower end is supported by the engine body, such as the cylinder block, via a bracket.

[0003] Regarding the support structure for the lower part of the catalyst case, a lower bracket is fixed by welding to the lower end of the catalyst case or the exhaust pipe connected to it, and the lower bracket and the cylinder block are fastened together by a support device. One example of the support device is a single stay that is fastened to the cylinder block with a bolt at one end and to the lower bracket with a bolt (and nut) at the other end.

[0004] The reason why the lower bracket is not fixed directly to the cylinder block but rather a stay is used is to absorb installation errors that may occur during assembly of the internal combustion engine and to absorb thermal expansion of the catalyst case. Therefore, the assembly procedure is to loosely fasten the stay to the cylinder block with bolts, loosely fasten the lower bracket and stay, and then firmly fasten the catalyst case to the cylinder head or exhaust turbocharger, and then firmly fasten the stay to the cylinder block, and firmly fasten the lower bracket and stay.

[0005] The bolts and nuts are tightened using a screwdriver tool, but since the worker works while standing on the exhaust side of the cylinder block, the fastening parts of the stay and lower bracket are designed to be exposed to the outside of the catalyst case when the catalyst case is set in the designated position, as seen by the worker.

[0006] The problem here is that catalyst cases tend to get larger due to demands for improved exhaust gas purification performance, and if the catalyst case gets larger, the catalyst case may hide the position where the stays are fastened to the cylinder block, making it impossible to fasten the stays to the cylinder block. One solution to this problem would be to change the attachment position of the stays to the cylinder block, but this would require a design change to the cylinder block, which would require changes to the die-casting mold or casting mold, increasing costs.

[0007] On the other hand, Patent Document 1 discloses a support structure for the lower part of the catalyst case, in which a base member elongated in the crankshaft direction (front-rear direction) is fixed to the upper end of the oil pan with bolts, and both front and rear ends of the base member are fixed to a lower bracket of the catalyst 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 portions between the base member and the front and rear arm members and the fastening portions between the lower bracket and the front and rear arm members are exposed outside the catalyst case. In addition, the arm members are bent in a dogleg shape so as to be recessed toward the center of the lower bracket, and in a side view, the fastening portions of the base member to the oil pan are located outboard of the fastening portions between the lower bracket and the arm members. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6984354 Summary of the Invention [Problem to be solved by the invention]

[0009] In Patent Document 1, the need for two arm members inevitably leads to increased costs and weight, and the fastening work is time-consuming. In addition, the base member is long enough that both its front and rear ends extend outside the catalyst case in a side view, and it is fastened to the oil pan with multiple bolts, further increasing costs, weight, and the time-consuming fastening work.

[0010] Furthermore, in Patent Document 1, if the catalyst case becomes too large and the fastening portions between the base portion and the oil pan and the fastening portions between the lower bracket and the arm member are hidden by the catalyst case in side view, there is a risk that the fastening work will become impossible. To address this, it is necessary to increase the front-to-rear length of the base member so that the fastening portions between the base portion and the oil pan and the fastening portions between the lower bracket and the arm member are positioned outside the front and rear of the catalyst case in side view, but in this case, the design of the oil pan must be changed, which increases costs.

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

[0012] The present invention is "It is equipped with an engine body including a cylinder block, a cylinder head, and an oil pan, and a catalyst case arranged on the exhaust side of the engine body, The upper end of the catalyst case is fixed to the cylinder head or the exhaust turbocharger, while a lower bracket is fixed to the lower end of the catalyst case directly or via an exhaust pipe, and the lower bracket is fixed to the engine body via a support device. In this basic configuration, "The support device is composed of 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 seen 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 catalyst case, and the fastening portion between the first stay and the second stay and the fastening portion between the second stay and the lower bracket are arranged so as not to overlap with the catalyst case." The structure is as follows.

[0013] The present invention can be developed in various ways. For example, claim 2 includes the following: "A flange-shaped lower rail portion that is long in the crankshaft direction is formed at the lower end of the exhaust side of the cylinder block, and the first stay is disposed so as to extend in the crankshaft 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 disposed so as to overlap with the catalyst case in the side view, and the second fastening portion is positioned outside the catalyst case in the side view, Furthermore, one end of the first stay, which is located on the opposite side of the second fastening portion across the first fastening portion, abuts from above on the lower rail portion of the cylinder block. The following configuration is adopted. [Effects of the Invention]

[0014] In the present invention, the fastening portion of the first stay to the engine body is hidden behind the catalyst case in a side view, so the conventional stay fastening portion (tapped hole) can be used as is. Therefore, it is possible to accommodate an increase in the size of the catalyst case without changing the design of the engine body, and cost increases can be suppressed. Compared to Patent Document 1, the number of parts is reduced, so costs can be significantly reduced and a decrease in fuel efficiency due to weight increases can be prevented.

[0015] Furthermore, in terms of the first stay, only a portion of it is hidden behind the catalyst case in a side view, so its length in the front-to-rear direction is much shorter than the base portion of Patent Document 1. This also contributes to cost reduction and weight reduction.

[0016] As the catalyst case becomes larger, the gap between the engine body and the lower bracket may change, but in the present invention, this change in catalyst case position can be absorbed by the second stay. It is also excellent at absorbing installation errors, offering greater flexibility than when the lower bracket is fastened to a single stay. When an EGR pipe is connected to the catalyst case or the exhaust pipe connected to it, the position of the catalyst case may change in relation to the EGR pipe during assembly of the internal combustion engine. However, in the present invention, the second stay can firmly absorb any change in catalyst case position caused by the EGR pipe.

[0017] Although the bolt is normally a right-hand thread, it can be prevented from rotating by clamping the bolt in the first stay and placing the right end against a protruding part of the engine body (for example, the lower rail part), so it can be accurately fixed in the specified position with a single bolt.

[0018] An oil pan is usually fixed to the lower end surface of the cylinder block with a group of bolts, and therefore a flange-shaped lower rail portion (lower deck portion) is often formed at the lower end of the cylinder block, but if one end of the first stay is placed 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 (integrity of the cylinder block and oil pan) is improved, contributing to improved rigidity of the entire engine body (power plant), and as a result, effects such as vibration suppression can be enjoyed. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a side view of a main part of an internal combustion engine according to an embodiment of the present invention; [Figure 2] 1A is a perspective view showing the arrangement of the stays, and FIG. 1B is a perspective view showing the fastened state. [Figure 3] 2(B) is a cross-sectional view taken along line IIIA-IIIA in FIG. 2(B), and FIG. 2(B) is a cross-sectional view taken along line IIIB-IIIB in FIG. 2(B). [Figure 4] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] (1).Basic structure Next, an embodiment of the present invention will be described with reference to the drawings. This embodiment is applied to an internal combustion engine for an automobile.

[0021] In the following, terms such as front-rear and side view are used to specify directions, but as already mentioned, the front-rear direction is the crankshaft direction, with the side where the timing chain and crankshaft pulley (neither of which are shown) are provided being the front and the side where the transmission case is located being the rear. The left-right direction is the direction perpendicular to the vertical direction and the crankshaft direction. The side view is the state as seen from the left-right direction (the direction perpendicular to the exhaust side).

[0022] The vertical direction is, to be precise, the direction of the cylinder bore axis, but since the internal combustion engine of this embodiment is vertical, the vertical direction is almost the same as the vertical line (although the cylinder bore axis may be tilted slightly forward toward the front of the vehicle body). Directions are indicated appropriately in the drawings.

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

[0024] Although not shown, 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 cylinder head 2. The transmission case described above is fixed to the rear surface of the cylinder block 1 and 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] 1, the cylinder head 2 of this embodiment is a type that incorporates an exhaust collection section, and has one exhaust outlet 4 opening on the exhaust side, to which a catalyst case 6 is connected as part of the exhaust passage via an elbow-shaped joint pipe 5. The joint pipe 5 is equipped with a flange plate 7, and the flange plate 7 is fixed to the cylinder head 2 with stud bolts and nuts.

[0026] The catalyst case 6 has a straight section 6a with a built-in catalyst, an upper cone section 6b that tapers upward and is formed integrally with the upper end of the straight section 6a, and a lower cone section 6c that tapers downward and is formed integrally with the lower end of the straight section 6a, and a joint exhaust pipe 9 equipped with a lower bracket 8 is formed integrally with 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 a main exhaust pipe 10 is connected to the exposed downward portion.

[0027] The internal combustion engine of this embodiment is mounted on the vehicle body in a horizontal, front-exhaust orientation with the crankshaft long in the vehicle width direction and the exhaust side facing the front of the vehicle body, and the main exhaust pipe 10 extends to the rear of the vehicle body below the oil pan 3. For this reason, the portion of the oil pan 3 where the main exhaust pipe 10 is submerged has a shallow bottom.

[0028] When viewed from the side, the catalyst case 6 is inclined at a slight angle relative to the vertical so that it shifts rearward as it goes downward. When viewed from the front, the catalyst case 6 is almost parallel to the exhaust side of the cylinder block 1. When viewed from the front, it is also possible to incline the catalyst case 6 so that it moves slightly away from the cylinder block 1 as it goes downward, or to incline it slightly in the opposite direction.

[0029] The lower end (upstream end) of an EGR pipe 11 that extracts EGR gas is connected by welding or the like to the upper part of the lower cone portion 6c of the catalyst case 6. The lower end of the EGR pipe 11 is connected to the end of the lower cone portion 6c that is farthest from the cylinder block 1, and then extends outward to the left and right, before changing direction and reaching the rear end of the exhaust side of the cylinder head 2.

[0030] The EGR pipe 11 has a lower horizontal portion 11a that forms its lower end, a vertically elongated portion 11b that extends upward in a bent, L-shaped incline, and an upper horizontal portion 11c that is connected to the upper end of the vertically elongated portion 11b, and a bracket plate 12 fixed to the end of the upper horizontal portion 11c is fastened to the cylinder head 2 with bolts. Therefore, an EGR internal passage that communicates with the upper horizontal portion 11c is formed at the rear end of the cylinder head 2 and is long in the left-right direction (the direction perpendicular to the plane of the drawing). The upper horizontal portion 11c is bent in 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] A flange-shaped lower rail portion (lower deck portion) 16 is formed at the lower ends of the exhaust side and intake side of the cylinder block 1, and a flange 17 of the oil pan 3 is fixed to the lower rail portion 16 with a group of bolts (not shown). In addition, an upper rail portion (upper deck portion) 18 is formed at the upper end of the cylinder block 1.

[0033] Although not shown in the drawings, the exhaust side and intake side of the cylinder block 1 basically reflect the shape of the cylinder in a plan view, and the exhaust side and intake side are recessed toward the interior of the cylinder block 1 between the bores. Therefore, the upper surface of the lower rail portion 16 is shaped like a bay that recesses into the interior of the cylinder block 1 between the bores. As shown in Figure 1, the upper cone portion 6b of the catalyst 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 for catalyst case The lower bracket 8 of the catalyst case 6 has a disc-shaped portion 8a that surrounds the joint exhaust pipe 9, and a protruding portion 8b that is continuous with the front portion of the disc-shaped portion 8a and protrudes toward the cylinder block 1. The protruding portion 8b has an inclined surface that becomes taller 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 that is fixed to the cylinder block 1 and a second stay 21 that is fixed to the first stay 20. The first stay 20 and the second stay 21 form a support device.

[0035] Both stays 20, 21 are made of processed sheet metal, and their shapes and positional relationship are as shown in Figure 2, for example. First, the first stay 20 is a strip-like plate that is long from front to back and is positioned so that it lies belly-down on the exhaust side of the cylinder block 1 and overlaps the lower rail portion 16 of the cylinder block 1 from above, with its front and rear intermediate portions fixed to boss portions 22 formed on the cylinder block 1 by first bolts 23. In addition, a stopper portion 25 is bent and formed at the rear end of the first stay 20, overlapping the lower rail portion 16 of the cylinder block 1 from above and fitting into a recess 24 in the cylinder block 1. The recess 24 is, for example, a recess that faces the portion between the bores.

[0036] The first stay 20 has a first through hole 26 through which the first bolt 23 is inserted, and 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 width portion 20a by removing material from its upper end, and the stopper portion 25 is formed in the narrow width portion 20a. The first stay 20 is made of steel plate or stainless steel, but is thick, at 5 mm or more, so forming the narrow width portion 20a makes it easy to bend the stopper portion 25.

[0038] The second stay 21 is basically in the form of a belt of equal width, and as clearly shown in Figure 3(A), it has an upper part 21a that overlaps with the first stay 20, a sloping lower part 21b that is overlapped laterally by the protruding part 8b of the lower bracket 8, and a middle part 21c that connects the two. A stud bolt 29 protrudes laterally from the sloping 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.

[0039] Because the middle portion 21c is curved so as to approach the cylinder block 1, the inclined lower portion 21b can be brought closer to the cylinder block 1, and the catalyst case 6 can be brought as close as possible to the cylinder block 1. 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 that the catalyst case 6 can be temporarily held (temporarily supported) on the second stay 21.

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

[0041] For example, as can be seen from FIG. 2(B), in a side view, the first bolt 23 (and the boss portion 22 and first through hole 26) are hidden behind the catalyst case 6, but the second bolt 28 and the stud bolt 29 are exposed in front of the catalyst case 6. Therefore, an operator can use a power wrench 33 to tighten the second bolt 28 and the nut 30. Therefore, a large catalyst case 6 can be installed while still using the boss portion 22 that has been used conventionally.

[0042] To further explain the procedure for installing the catalyst case 6, first, the first stay 20 is firmly fixed to the cylinder block 1, while the second stay 21 is hand-tightened and overlaps the first stay 20. Then, 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 finally fixed to the cylinder head 2, and then the bracket plate 12 of the EGR pipe 11 is finally 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 rotated with a wrench 33 to fully tighten them. At this time, it is preferable to perform both hand tightening and wrench tightening to prevent twisting between the first stay 20 and the second stay 21. For example, the front-to-back and left-to-right position of the catalyst case 6 may not be consistent due to the precision or installation error of the EGR pipe 11. However, because the second stay 21 is provisionally fastened to the first stay 20 and the lower bracket 8, the difference in the position of the catalyst case 6 can be absorbed by aligning the position of the second stay 21 with the position of the catalyst case 6.

[0044] In this embodiment, the EGR pipe 11 extends in a position that intersects with the axis of the catalyst case 6 in a side view. Therefore, due to thermal expansion of the EGR pipe 11, the lower end of the catalyst case 6 tends to be pushed in the longitudinal direction of the EGR pipe 11, as shown by dotted arrow 34. As a result, the external force caused by 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 FIG. 2(B)). In other words, the thermal expansion of the EGR pipe 11 acts in a direction that screws in the first bolt 23. This prevents the first bolt 23 from loosening.

[0045] Furthermore, because 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 firmly pressed down by the first stay 20, improving adhesion to the oil pan 3. As a result, the rigidity of the entire power plant (entire engine body) is improved, contributing to vibration suppression.

[0046] In the first stay 20 and the second stay 21, the through holes for inserting the bolts are formed by punching, and as shown by arrow 36 in Figures 4(B) and 4(D), the punching direction 36 of the punch is aligned with the insertion direction of the bolts 23, 28. In sheet metal processing, sagging due to punching is likely to occur, but in this embodiment, a roundness 37 due to sagging is provided on the opening edge on the side where the heads of the bolts 23, 28 come into contact, thereby preventing stress concentration and improving strength.

[0047] Although the embodiments of the present invention have been described above, the present invention can be embodied in various other ways. For example, the catalyst case can be fixed to the oil pan. The specific shapes of the first stay and second stay can be changed as appropriate depending on the actual situation, such as the arrangement of the catalyst case. The lower bracket can also be fixed to the lower cone portion of the catalyst case. If an exhaust turbocharger is provided, the upper end of the catalyst 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, and is therefore industrially applicable. [Explanation of symbols]

[0049] 1. Cylinder block that forms part of the engine body 2 Cylinder head that forms part of the engine body 3 Oil pan, which forms part of the engine body 5. Joint pipe 6 Catalyst case 8 Lower Bracket 8b Protruding part 9 Exhaust pipe joint 11 EGR pipe 13 Insulator 16 Lower rail part of cylinder block (lower deck part) 20 1st Stage 21 Second Stage 22 Boss section 23 First Bolt 25 Stopper part 28 Second bolt 29 Stud bolt 30 nuts 33 Wrench (power tool)

Claims

1. The engine comprises an engine body including a cylinder block, a cylinder head, and an oil pan, and a catalyst case disposed on the exhaust side of the engine body, an internal combustion engine in which an upper end of the catalyst case is fixed to the cylinder head or an exhaust turbocharger, while a lower bracket is fixed to a lower end of the catalyst case directly or via an 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 seen from a direction perpendicular to the exhaust side of the engine body, a fastening portion between the first stay and the engine body overlaps with the catalyst case, and a fastening portion between the first stay and the second stay and a fastening portion between the second stay and the lower bracket are arranged so as not to overlap with the catalyst case. Internal combustion engine.

2. a flange-shaped lower rail portion that is long in the crankshaft axis direction is formed at a lower end of an exhaust side surface of the cylinder block, and the first stay is disposed so as to extend in the crankshaft axis direction along an 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 disposed so as to overlap with the catalyst case in the side view, and the second fastening portion is positioned outside the catalyst case in the side view, and one end of the first stay located on the opposite side of the second fastening portion with the first fastening portion sandwiched therebetween abuts against the lower rail portion of the cylinder block from above.

2. An internal combustion engine according to claim 1.

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