JP7699085B2 - Engine bore structure - Google Patents

Description

The present invention relates to the structure of the inter-bore water passage between adjacent cylinders in the cooling water passage of the cylinder block of an engine, i.e., the inter-bore structure of the engine.

In a water-cooled engine, the cylinder block, more specifically the cylinder portion in which the piston is fitted, is provided with a cooling water passage (water jacket) for passing cooling water around the cylinder. Furthermore, in engines with multiple cylinders, such as in-line four-cylinder engines, as disclosed in Patent Document 1, many of them also have water passages between adjacent cylinders, i.e., between the bores.

The thermal conditions between the bores in the cylinder section are more severe than in other areas, and if the distance between the bores is made larger and sufficient cooling water channels are provided in an attempt to increase the thermal capacity, the engine length (the length of the cylinder section in the direction of the cylinders in series) will become bloated, and if the cooling water channels are minimized in order to reduce the distance between the bores and make the engine length compact, the thermal capacity will be insufficient. Therefore, it is inherently difficult to achieve a balance between these two when designing the space between the bores.

For example, increasing engine power output leads to an increase in heat generation and combustion pressure near the top dead center of the piston, making it necessary to improve the cooling and strength of the cylinder. Therefore, if the thickness between the bores is not changed (the engine length does not increase) in order to prioritize compact engine length, it is necessary to remove the connecting walls (connecting walls connecting adjacent cylinders between the bores; see 4b in Figure 2 of Patent Document 1) in order to improve cooling.

However, if the connecting wall were removed, the support for the liner (cylinder liner) at that point would be lost, which could lead to a decrease in the strength of the liner. In this way, the reality is that "if the inter-bore thickness is constant, there is a trade-off between cooling performance and strength."

JP 2001-164985 A

In light of the above-mentioned circumstances, the object of the present invention is to provide a more streamlined inter-bore structure for an engine, which improves cooling while maintaining the dimensions between the bores, by reviewing the structure between the bores, which is subject to strict thermal conditions, and by making new improvements, thereby enabling increased output without increasing the engine length.

The present invention provides an inter-bore structure for an engine, comprising:
The cooling water passages formed in the cylinder block are provided with interbore water passages between adjacent cylinders,
A connecting wall is provided in the interbore water passage to connect adjacent cylinders together,
the connecting wall is shaped to guide the cooling water flowing from the intake side to the exhaust side in the inter-bore water passage to the cylinder head on the exhaust side,
The inter-bore water passage is characterized in that a cross-sectional area of the inter-bore water passage is gradually reduced from the intake side to the exhaust side.

For other elements of the present invention, please refer to claims 1 to 5 .

According to the present invention, a connecting wall is provided to connect adjacent cylinders, improving the strength and rigidity of the inter-bore area of the cylinder block. Furthermore, the cooling water flowing from the intake side to the exhaust side in the inter-bore water passage is guided by the connecting wall to the cylinder head side (piston head side), greatly improving the cooling (heat dissipation) of the exhaust side and cylinder head side areas, which are subject to the most severe thermal load.

As a result, in conventional technology, it was not possible to simultaneously improve the cooling performance and strength of the upper portion between the bores by increasing the output. However, according to the present invention, it is possible to provide an inter-bore water channel structure that can simultaneously improve the cooling performance and strength of the upper portion between the bores, for example, to realize an engine with increased output without changing the length of the cylinders in series.

FIG. 1 is a side view showing an outline of the flow of cooling water in an engine; Schematic diagram showing the structure of a cooling device The flow of cooling water is shown in (A) of the cylinder section in plan view, and (B) of the cylinder head in plan view. 3A is a cross-sectional view taken along line Y-Y in FIG. 3A; FIG. 3B is a cross-sectional view taken along line B-B in FIG. 3A; and FIG. 3C is a cross-sectional view taken along line CC in FIG. Plan view of the cylinder head A cross-sectional view of the Z-Z line in FIG. 5 (a cross-sectional view showing a portion corresponding to the bores) FIG. 13 is a cross-sectional view of a main portion showing another embodiment of the inter-bore water channel;

Below, an embodiment of the engine bore structure according to the present invention will be described with reference to the drawings for an industrial diesel engine. In the industrial diesel engine (hereinafter abbreviated as engine) E, the side with the cooling fan 10 is the front, the side with the flywheel 7 is the rear, the side with the intake port 30 [the side with the intake manifold (not shown)] is the right, and the exhaust port 28 [the side with the exhaust manifold (not shown)] is the left.

As shown in FIG. 1, in engine E [a vertical in-line four-cylinder (multi-cylinder) water-cooled engine], a cylinder head 2 is assembled onto a cylinder block 1, a head cover 3 is assembled onto the cylinder head 2, and an oil pan 4 is assembled below the cylinder block 1. The upper part of the cylinder block 1 is a cylinder section 1A into which a piston 6 is fitted. 5 is a crankshaft, 6 is a piston, 7 is a flywheel, 8 is a transmission belt, 9 is a water pump, 10 is a cooling fan, and 11 is a radiator. The upper part of the cylinder block 1 is formed into the cylinder section 1A into which a piston 6 is fitted.

As shown in Figures 1 to 3, the cooling water w in the cooling system R of the engine E flows roughly in the following order: water pump 9 → water inlet 31 → cylinder section 1A → cylinder head 2 → water outlet 32 → thermostat 12 → upstream hose 13 → radiator 11 → downstream hose 14 → water pump 9. The water inlet 31 of the cylinder section 1A is located in the center slightly closer to the intake side in the width direction, and the water outlet 32 of the cylinder head 2 is located closer to the exhaust side in the width direction. Note that 34 in Figure 2 is a reservoir tank.

As shown in FIG. 2, when the water temperature is lower than a predetermined temperature, such as immediately after starting the engine E, the thermostat 12 is closed, so that the cooling water w from the water outlet 32 returns to the water pump 9 through the short-circuit hose 33 without passing through the radiator 11. In addition, a portion of the cooling water w also has a path that cools the oil cooler 16 from the cylinder head 2 through a dedicated supply path 15, and then returns to the water pump 9 through the discharge path 17 (see FIG. 1). In FIG. 2, the thick white arrows indicate the flow of the cooling water w, and the line arrows indicate the flow of the air k during air bleeding.

As shown in Figures 1 and 3, the cooling water w that enters the cylinder section 1A from the water inlet 31 on the front side of the cylinder section 1A flows primarily rearward, but also flows upward for each cylinder bore (cylinder) 1a. Therefore, the cooling water w flows upward from the cylinder cooling water passage 1W, which is the water jacket of the cylinder head 2, through multiple floating holes 2f into the head cooling water passage 2W, which is the water jacket of the cylinder head 2, and in the head cooling water passage 2W, it flows from rear to front toward the water outlet 32 (to the water pump 9 in the front).

As shown in Figures 3(A) and 4(A), the interbore water passage 1B formed between adjacent cylinder bores 1a, 1a of the cylinder section 1A is provided with a connecting wall a that connects and integrates the adjacent cylinder bores 1a, 1a. The connecting wall a is made up of a lower wall 35, a lower connecting wall 18, a middle connecting wall 19, an upper connecting wall 20, and an upper wall 36, and is formed to cross the interbore water passage 1B. The interbore water passage 1B and the head cooling water passage 2W above it are connected to each of the communication holes 21, 22 on the intake and exhaust sides of the cylinder section 1A, and the vertical hole water passage 21A and the oblique hole water passage 22A (both described later) of the cylinder head 2.

As shown in FIG. 4(A), the lower wall 35 is formed as an angular overhanging wall that protrudes slightly upward from the lower end of the inter-bore water passage 1B. The lower connecting wall 18 is formed as an independent wall with a roughly trapezoidal cross section and an upwardly inclined surface 18a that approaches the intake side (right side) toward the exhaust side. The left-right width of the upwardly inclined surface 18a is set to about half the left-right width of the entire lower connecting wall 18, but is not limited to this.

The middle connecting wall 19 has an intake side inclined wall 19a with approximately the same angle as the ascending inclined surface 18a, and an exhaust side horizontal wall 19b, and is formed as a flat, bent wall with an upward convex "V" shape as a whole. The upper connecting wall 20 has a starting end downward wall portion 20a with a gentler inclination angle and shorter left and right length than the intake side inclined wall 19a, and a horizontal main body wall portion 20b. The upper wall 36 is a downwardly extending wall with a downwardly convex flat shape, and communication holes 21, 22 are formed at both left and right ends.

The inter-bore water passage 1B is therefore formed with a first horizontal passage 41 between the lower wall 35 and the lower connecting wall 18, a second passage 42 between the lower connecting wall 18 and the middle connecting wall 19, which is bent and generally higher towards the exhaust side, a third passage 43 between the middle connecting wall 19 and the upper connecting wall 20, which is inclined upward only at the intake side end, and a fourth passage 44 between the upper connecting wall 20 and the upper wall 36, which is flat and has a small vertical width. In other words, the connecting walls 35, 18-20, 36 are generally shaped to guide the cooling water w flowing from the intake side to the exhaust side in the inter-bore water passage 1B, which is made up of the first to fourth passages 41-44, to the exhaust side of the cylinder head 2.

The cross-sectional area of the bore-to-bore water passage 1B is configured to be smaller from the intake side to the exhaust side by mainly setting the cross-sectional area (the area of the cross section cut by a plane extending in the vertical direction and the cylinder serial direction) of the lower connecting wall 18 and the middle connecting wall 19 to be larger from the intake side to the exhaust side. The lower connecting wall 18 and the middle connecting wall 19 are configured to be curved to be convex toward the cylinder head 2 side when viewed in the front-rear direction (when viewed in the cylinder arrangement direction), and the cross-sectional area of the five connecting walls 35, 18-20, 36 as a whole is set so that the cross-sectional area of the upper half (half on the cylinder head 2 side) is smaller than the cross-sectional area of the lower half (half on the opposite side to the cylinder head 2 side). In addition, the diameter of the exhaust side communication hole 21 is set larger than the diameter of the intake side communication hole 22, so that the flow area of the exhaust side communication passage (an example of an exhaust side communication passage) 21 is set to be larger than the flow area of the intake side communication passage (an example of an intake side communication passage) 22.

As shown in Figures 1 and 5, the cylinder head 2 is internally formed with a head cooling water passage 2W through which cooling water w passes, and Figures 3(B) and 4 show the inter-bore corresponding portion 2b located directly above the inter-bore water passage 1B between adjacent cylinder bores 1a, 1a in the cylinder head 2. In the inter-bore corresponding portion 2b, the area between a pair of left and right insertion walls 24 having insertion holes 2c through which fastening bolts 23 pass, and surrounded by the cylinder head bottom wall 26 and the head top wall 25, is formed as the head cooling water passage 2W.

The bottom surface 26a of the cylinder head bottom wall 26 is the surface that is placed on the top surface 1b of the cylinder section 1A via a gasket G, and the head top wall 25 is the top wall of the cylinder head on which the head cover 3 is placed. In addition, 28 in Figures 5 and 6 is an exhaust port, and head cooling water channels 2W are formed above and below it, and on the right side of the right insertion wall 24.

In other words, as shown in Figures 3 to 6, the cylinder head 2 is assembled onto the cylinder block 1 with a plurality of tightening bolts 23. The cylinder head 2 is provided with insertion walls 24, 24 for passing the tightening bolts 23, 23 arranged on both sides between the adjacent cylinder bores 1a, 1a in the cylinder block 1, a head upper wall 25 connecting the upper ends of the pair of insertion walls 24, 24, and a cylinder head bottom wall 26. A head cooling water passage 2W is formed by the pair of insertion walls 24, 24, the head upper wall 25, and the cylinder head bottom wall 26. A vertical wall 27 is formed between the pair of insertion walls 24, 24, straddling the head upper wall 25 and the cylinder head bottom wall 26, and extending in the direction connecting the pair of insertion walls 24, 24 to block the head cooling water passage 2W.

As shown in Figures 4(A), 5, and 6, the vertical wall 27 is continuously connected to and integrated with the left end of the right-side (intake port side) insertion wall 24, and the right end 27a (the end on the opposite side of either side) of the vertical wall 27 is formed so that the left-right position i is in the central region C between the pair of insertion walls 24, 24. As an example of the range of the central region C, when the center distance between the left and right insertion walls 24 is D, ±10% of the left-right center (C: 0.4D≦i<0.6D) is given, but other ranges (such as a range of 30% to 70%) are also acceptable.

If the width of the vertical wall 27 is the length d between the center of the right-side through-wall 24 and the left end 27a, then the length d of the vertical wall 27 is set to the distance between the pair of through-walls 24, 24, i.e., about half the center distance D (0.4D≦d≦0.6D). As shown in FIG. 6, it is advantageous to form a reinforcing wall 29 in the form of an upwardly protruding rib extending left and right (in the direction connecting the pair of through-walls 24, 24) on the cylinder head bottom wall 26 in the inter-bore corresponding portion 2b.

The left end of the reinforcing wall 29 rises diagonally upward and connects to the left insertion wall 24, and a vertical hole water passage (hole-shaped cooling water passage) 21A is formed in the diagonal reinforcing wall portion 29a (see Figures 4(A), (C) and 6). The vertical hole water passage 21A is connected to the communication hole 21 on the left side of the cylinder portion 1A via a gasket G, and the vertical hole water passage 21A and the communication hole 21 connect the cylinder cooling water passage 1W and the head cooling water passage 2W vertically.

As shown in Figs. 4(A), (B) and 6, the head cooling water passage 2W on the front (one side) of the vertical wall 27 and the bottom surface 26a directly below the vertical wall 27 are connected by an oblique hole water passage 22A formed by extending forward and upward from the bottom surface 26a. In other words, an oblique hole water passage 22A (a cooling water passage with an oblique hole) that straddles the head cooling water passage 2W on one side separated by the vertical wall 27 and the lower end of the vertical wall 27 or the bottom surface 26a of the cylinder head bottom wall 26 on the other side is provided in the lower part of the vertical wall 27. The cylinder cooling water passage 1W and the head cooling water passage 2W are also connected vertically by the oblique hole water passage 22A and the right communication hole 22, which are connected via a gasket G.

[About the effects]
Because the increased combustion pressure caused by the increased power output increases the stress on the upper part of the cylinder, it is necessary to reduce the stress on the upper part of the cylinder bore 1a (liner) where the wall thickness is thin by narrowing the wall spacing (the spacing between adjacent cylinder bores 1a, 1a). However, narrowing the wall spacing causes a problem of worsening the cooling performance of the upper part of the bore, where the cooling performance must be improved. Therefore, in order to increase the cross flow (the flow of cooling water w from the intake side to the exhaust side) in the upper part of the bore, which is being deteriorated, the following configurations 1) to 3) seem to be effective.

1) Reducing or eliminating the cross flow in the lower portion between the bores where there is a cooling margin; 2) Providing a guide wall that enhances the water flow to the portion choked by the boss (insertion wall 24) of the fastening bolt 23; 3) In order to promote the cross flow in the upper portion between the bores, making the floating water passage (intake side communication hole 22) to the cylinder head 2 on the intake side small and making the floating water passage (exhaust side communication hole 21) to the cylinder head 2 on the exhaust side large.

In the present invention, configuration 1) is achieved by setting the overall cross-sectional area of the connecting walls 35, 18-20, 36 so that the cross-sectional area of the upper half is smaller than the cross-sectional area of the lower half. Configuration 2) is achieved by directing the cooling water w flowing from the intake side to the exhaust side in the inter-bore water passage 1B to the exhaust side cylinder head by mainly designing the shapes and dimensions of the lower connecting wall 18 and the middle connecting wall 19. Configuration 3) is achieved by making the flow area of the exhaust side connecting passage 21 larger than that of the intake side connecting passage 22.

In other words, by providing connecting walls 35, 18-20, 36 in the interbore water passage 1B consisting of the first through fourth passages 41-44, the strength between the bores of the cylinder section 1A is improved, while the water flow in the interbore water passage 1B, mainly on the exhaust side and cylinder head side, is also improved. As a result, while in the conventional technology, it was not possible to simultaneously improve the cooling performance and strength of the upper part between the bores by increasing the output, the present invention makes it possible to improve both at the same time, and has the advantage of being able to provide an engine that can increase the output without straining it while maintaining the engine length. In addition, because the cross-sectional area of the interbore water passage becomes smaller from the intake side to the exhaust side, the flow rate of the cooling water becomes faster from the intake side to the exhaust side, which also has the effect of further improving the cooling performance on the exhaust side.

[Another embodiment]
The connecting wall a provided in the inter-bore water passage 1B may be a triangular connecting wall 37, 38 whose cross-sectional area (the area of a cross section cut by a surface extending vertically and longitudinally) increases toward the exhaust side, or a combined wall a consisting of an obliquely oriented lower wall 39 of constant thickness and an inverted triangular upper wall 40 that is slightly thicker toward the intake side, as simply shown in Figure 7. In this case, a fifth passage 45 (1B) is formed between the upper wall 40 and the upper wall 36.

As shown in FIG. 7, the upper side 37a of the lower connecting wall 37 may be a concave curved surface that is concave upward. The number of connecting walls a may be one (single) or two or more (multiple).

1 Cylinder block 1B Bore water passage 1W Cooling water passage 1a Cylinder (cylinder bore)
2 Cylinder head 2W Head cooling water passage 21 Exhaust side communication passage 22 Intake side communication passage a Connecting wall w Cooling water

Claims (5)

The cooling water passages formed in the cylinder block are provided with interbore water passages between adjacent cylinders,
A connecting wall is provided in the inter-bore water passage to connect and integrate adjacent cylinders, and the connecting wall is shaped to guide the cooling water flowing from the intake side to the exhaust side in the inter-bore water passage to the cylinder head on the exhaust side,
The inter-bore water passage is formed such that a cross-sectional area of the inter-bore water passage becomes smaller from the intake side to the exhaust side,
The connecting wall has a curved shape that is convex toward the cylinder head when viewed in the cylinder arrangement direction . The bore-to-bore structure of the engine according to claim 1, in which the cross-sectional area of the connecting wall is set to increase from the intake side to the exhaust side, so that the cross-sectional area of the bore-to-bore water passage is configured to decrease from the intake side to the exhaust side. The cooling water passages formed in the cylinder block are provided with interbore water passages between adjacent cylinders,
A connecting wall is provided in the inter-bore water passage to connect and integrate adjacent cylinders, and the connecting wall is shaped to guide the cooling water flowing from the intake side to the exhaust side in the inter-bore water passage to the cylinder head on the exhaust side,
The inter-bore water passage is formed such that a cross-sectional area of the inter-bore water passage becomes smaller from the intake side to the exhaust side,
An engine bore-to-bore structure in which an intake side connecting passage and an exhaust side connecting passage are provided in the cylinder block, which are connected to the intake side and exhaust side at the cylinder head side end of the bore-to-bore water passage and to a head cooling water passage provided in the cylinder head, and the flow path area of the exhaust side connecting passage is set larger than the flow path area of the intake side connecting passage . 4. The bore-to-bore structure of an engine according to claim 3, wherein the cross-sectional area of the connecting wall is set to increase from the intake side to the exhaust side, so that the cross-sectional area of the inter-bore water passage is configured to decrease from the intake side to the exhaust side. 5. The bore structure of an engine according to claim 1 , wherein the cross-sectional area of the connecting wall is set so that the cross-sectional area of the half on the cylinder head side is smaller than the cross-sectional area of the half on the opposite side to the cylinder head side.

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