JP5071263B2 - Internal combustion engine knock sensor mounting structure - Google Patents

Description

  The present invention relates to a knock sensor mounting structure for an internal combustion engine, and more particularly to a technique for improving the detection accuracy of knocking.

  Knocking is abnormal combustion in which a part of the air-fuel mixture self-ignites in the combustion chamber without proper ignition. That is, during combustion, an unburned air-fuel mixture remains in a portion such as the periphery of the combustion chamber that is relatively far from the spark plug (also referred to as end gas). It becomes high pressure and self-ignites without waiting for flame propagation. This abnormal combustion due to self-ignition has an extremely high combustion speed as compared with combustion due to proper ignition, so that a shock wave is generated in the combustion chamber, and the vibration is transmitted to the inner wall of the cylinder, causing phenomena such as knocking noise and vibration.

  The knock sensor is attached to the engine in order to indirectly detect the resonance in the combustion chamber, particularly the primary resonance, formed by the vibration of the knocking. In general, a knock sensor is provided with a transducer that displaces on a predetermined sensor axis, and the displacement of the transducer is detected by a piezoelectric element or the like. Therefore, the detection sensitivity of the knock sensor is the sensor axis. Is higher in the direction.

  For this reason, when the knock sensor is attached to the engine, it is preferable to arrange the knock sensor so that the sensor axial direction coincides with the knocking resonance direction as much as possible.

With regard to the knock sensor mounting structure for the purpose of improving the detection accuracy of knocking, for example, the water jacket is obstructed and the vibration of knocking is difficult to be transmitted. There is a sensor mounting boss that is filled with a recess, and a knock sensor is mounted on the sensor mounting boss (Patent Document 1).
JP 2001-193520 A

  By the way, according to the examination by the present inventors, in the case of the pent roof type combustion chamber 50, as shown in FIG. 8, the direction in which the intake port 51 and the exhaust port 52 are aligned due to the influence of the shape (arrow line). Resonance due to knocking is likely to occur either in the direction indicated by X (also referred to as the supply / exhaust direction) or in the direction orthogonal to the supply / exhaust direction (the direction indicated by the arrow line Y, also referred to as the crankshaft direction). Under the general intake air flow control, the end gas is likely to be formed around the intake side or the exhaust side of the combustion chamber, and a relatively large resonance is likely to occur in the supply / exhaust direction.

  Therefore, when a knock sensor is attached to an engine equipped with a pent roof type combustion chamber, the sensor axial direction is usually arranged so as to coincide with the supply / exhaust direction. The sensor is also attached to the outer surface of the cylinder block.

  However, if the flow control of the intake air is diversified and the generation site of the end gas changes, the possibility that a large resonance occurs in the crankshaft direction rather than the supply / exhaust direction increases. If the knock sensor is arranged so as to coincide with the air supply / exhaust direction, there is a risk of knocking detection failure.

  The present invention has been made in view of the above points, and the object of the present invention is to provide a knock sensor that can detect knocking efficiently even if the formation site of the end gas varies, and can suppress the detection leakage of knocking. It is to provide a mounting structure.

  In order to achieve the above object, in the present invention, the knock sensor is arranged so that the sensor axis is oriented in a predetermined direction between the supply / exhaust direction and the crankshaft direction in which resonance due to knocking is likely to occur.

  That is, the knock sensor mounting structure for an internal combustion engine according to the present invention has a pair of side surfaces substantially parallel to the crankshaft, and includes an engine main body provided with a cylinder therein, and the knock sensor is mounted on the side surface. In an internal combustion engine, a pent roof type combustion chamber is formed in the upper part of the cylinder, and an intake port and an exhaust port are connected so that respective openings connected to the combustion chamber are arranged in a direction substantially perpendicular to the crankshaft. The knock sensor is provided with a vibrator that displaces on a predetermined sensor axis in order to detect knocking occurring in the combustion chamber, and the sensor axis is viewed in the axial direction of the cylinder. Thus, the engine body is inclined at a predetermined angle of 45 ° or more from the reference line orthogonal to the crankshaft toward the side surface of the engine body.

  According to such a configuration, first, since a pent roof type combustion chamber is formed, the supply / exhaust direction in which the opening of the intake port and the opening of the exhaust port are aligned under the influence of the shape, and this supply / exhaust direction Resonance due to knocking is likely to occur in any of the crankshaft directions orthogonal to

  The knock sensor attached to the side surface of the engine main body has high sensitivity in the sensor axis direction due to the vibrator provided therein, so that the sensor axis is 45 ° or more from the reference line facing the supply / exhaust direction to the crankshaft side. As described later, the detection sensitivity to knocking resonance occurring in the supply / exhaust direction and the crankshaft direction can be made substantially equal. Therefore, even when the end gas generation site changes, knocking can be detected efficiently, and knocking detection omission can be suppressed. Specifically, the predetermined angle may be set within a range of 45 ° to 65 °.

  More specifically, it is effective when a plurality of intake ports are connected to the cylinder and the openings of the plurality of intake ports are aligned in the axial direction of the crankshaft.

  As the amount of intake air flowing into the combustion chamber increases, the flow of intake air formed in the combustion chamber is likely to change, so the end gas formation site is likely to change accordingly. If so, the magnitudes of resonance in the supply / exhaust direction and the crankshaft direction also change, which increases the need to detect resonance in both directions in a balanced manner.

  Further, it is more effective when at least one of the plurality of intake ports is provided with intake flow control means for changing the flow resistance of intake air.

  When the flow resistance of the intake air changes, the intake balance introduced into the combustion chamber is biased and a swirl flow swirling in the circumferential direction of the cylinder is formed. In this case, the end gas formation site is more likely to change, and the magnitude of the knocking resonance that occurs in each of the supply / exhaust direction and the crankshaft direction also changes greatly. For example, if the resonance strength in the crankshaft direction becomes large but the resonance strength in the air supply / exhaust direction becomes so small that it cannot be detected, there is a risk of detection omission in the conventional knock sensor mounting method. However, since resonance in both directions can be detected in a well-balanced manner, knocking detection omission can be suppressed.

  For example, as the intake flow control means, a valve element capable of opening and closing can be provided in the intake port.

  The engine body may be provided with a plurality of cylinders, and the plurality of cylinders may be arranged in a line in the axial direction of the crankshaft. In this case, one knock sensor can be provided for a plurality of cylinders arranged in a row.

  This is because knock sensors can be arranged in almost the same direction with respect to individual cylinders, so that knocking occurring in a plurality of cylinders can be detected efficiently.

  More specifically, when one cylinder is provided in the engine main body, such as a single cylinder engine or a V-type two cylinder engine, the predetermined angle is set within a range of 45 ° to 51 °. preferable.

  Similarly, when two cylinders are provided in the engine main body, such as an in-line two-cylinder engine or a V-type four-cylinder engine, the predetermined angle is preferably within a range of 47 ° to 53 °. When the engine main body is provided with three cylinders such as an engine or a V-6 engine, the predetermined angle is preferably in the range of 49 ° to 55 °. In the case where four cylinders are provided in the engine main body such as an engine, the predetermined angle is preferably in the range of 51 ° to 58 °. The engine main body such as an inline 5-cylinder engine or a V-type 10-cylinder engine In the case where five cylinders are provided, the predetermined angle is preferably set within a range of 54 ° to 60 °, and the engine book such as an in-line 6-cylinder engine or a V-type 12-cylinder engine When six cylinders are provided in the body, the predetermined angle is preferably set within a range of 56 ° to 62 °.

  Then, even if the end gas formation site changes, knocking can be detected with higher certainty, and knocking detection omission can be suppressed.

  As described above, according to the present invention, knocking can be detected efficiently and knocking detection omission can be suppressed even when the end gas formation site in the combustion chamber varies.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

(Entire engine configuration)
1 and 2 show an outline of a spark ignition type in-line four-cylinder three engine (internal combustion engine) to which the present invention is applied. FIG. 1 is a plan view showing the engine, and FIG. 2 is a cross-sectional view showing a structure related to one cylinder 3 of the engine. In this embodiment, an in-line engine is exemplified, but the present invention can also be applied to a single cylinder engine, a V-type engine, or the like.

  As shown in FIGS. 1 and 2, the engine main body 1 is composed of a cylinder head, a cylinder block 26, and the like, and four cylinders 3a, 3b, 3c, 3d substantially parallel to the crankshaft 2 are disposed therein. (Also simply referred to as cylinder 3) are provided in a row. In the figure, the symbol K indicates the axis of the crankshaft 2 (also referred to as the crankshaft K).

  As shown in FIG. 2, each cylinder 3 accommodates a piston 5 so as to be reciprocally displaceable in the direction of the axis P of the cylinder 3. The piston 5 is connected to the crankshaft 2 via a connecting rod 6, and is configured such that the crankshaft 2 rotates by a reciprocating displacement operation.

  A pent roof type combustion chamber 8 is formed in the upper part of each cylinder 3. The pent roof type combustion chamber 8 is defined by a triangular roof-shaped ceiling wall 7 and a top surface of the piston 5.

  A spark plug 12 is provided at the approximate center of the top portion extending in the direction of the crank axis K in the ceiling wall 7 of the combustion chamber 8, and the tip of the plug faces the combustion chamber 8.

  In addition, a pair of intake port openings 14 and 14 and a pair of exhaust port openings 15 and 15 arranged in the direction of the crank axis K are opened on each of the pair of slopes extending on both sides of the top part with the top part interposed therebetween. The intake port openings 14 and 14 and the exhaust port openings 15 and 15 are positioned so as to face each other so as to be aligned in a direction substantially orthogonal to the crankshaft 2.

  A pair of intake ports 10 and 10 and a pair of exhaust ports 11 and 11 are connected to the intake port openings 14 and 14 and the exhaust port openings 15 and 15, respectively. Each exhaust port 11 is connected to a pipe 16 and is connected to an exhaust collecting pipe 17.

  Each intake port 10 is provided with an intake valve 19 that opens and closes an intake port opening 14 by an intake cam 18, and each exhaust port 11 is provided with an exhaust valve 21 that opens and closes an exhaust port opening 15 by an exhaust cam 18. Yes.

  One of the pair of intake ports 10 and 10 is provided with a flow control valve 22 (intake flow control means) capable of opening and closing to change the flow resistance of intake air. That is, in this engine, by controlling the opening degree of the flow control valve 22 when the intake air is introduced into the combustion chamber 8, the amount of intake air introduced from one intake port 10 can be changed to a larger or smaller value. The flow of the intake air in the room can be changed.

  For example, when the opening degree of the flow control valve 22 is set large and the same amount of intake air is introduced from the two intake ports 10, 10, the upper part of the combustion chamber 8 is directed from the intake side to the exhaust side. Thus, a flow of intake air swirling in the longitudinal direction of the cylinder 3 is formed (tumble flow). When the opening degree of the flow control valve 22 is set to be small and the intake balance introduced from the pair of intake ports 10 and 10 is biased, the flow of intake air swirling in the circumferential direction of the cylinder 3 is formed in the combustion chamber 8. (Swirl style).

  An injector 23 is disposed below the pair of intake ports 10 and 10 so that fuel is directly injected into the combustion chamber 8 as the intake air is introduced so that a uniform air-fuel mixture is formed. It has become. A knock sensor 25 is disposed below the injector 23 in order to detect knocking that occurs in the combustion chamber 8.

(Knock sensor mounting structure)
FIG. 3 shows a view of the cylinder block 26 of the engine body 1 as viewed from above with the cylinder head removed.

  As shown in the figure, the cylinder block 26 (engine main body) is formed so as to extend in the direction of the crank axis K, and four cylinders 3a,. It is provided to line up. A pair of side surfaces 26a and 26b substantially parallel to the crankshaft 2 are provided so as to be close to both sides of the cylinder row.

  The knock sensor 25 is attached to a sensor attachment boss 27 formed at a substantially central portion in the longitudinal direction of the cylinder row at the upper part of the side surface 26a on the intake side of the cylinder block 26. A water jacket 28 for circulating the cooling water is formed so as to surround the cylinder row.

  Although not shown, the knock sensor 25 includes a vibrator, a piezoelectric element, an output device, and the like. The knock sensor 25 detects the displacement of the vibrator that is displaced on a predetermined sensor axis S with the piezoelectric element, and the detected displacement of the vibrator. Since the output device converts the signal into an electric signal and outputs the signal, the detection sensitivity is higher in the direction of the sensor axis S. Therefore, when the knock sensor 25 is attached to the cylinder block 26, it is preferable that the sensor sensor be disposed so that the sensor axis S direction coincides with the direction in which knocking resonance occurs.

  In this regard, in the case of the pent roof type combustion chamber 8, it is recognized that knocking resonance tends to occur in either the supply / exhaust direction or the crank axis K direction orthogonal to the direction due to the influence of the shape (FIG. 8). reference).

  In a high-load operation region of an engine where knocking is likely to occur, usually, a large amount of intake air is introduced into the combustion chamber 8 to form a tumble flow that swirls vertically in the supply / exhaust direction. Since the end gas is formed at the end of the combustion chamber 8 on the intake side or the end of the exhaust side due to the influence of the flow, a relatively large resonance is likely to occur in the supply / exhaust direction. A knock sensor 25 is attached so as to face.

  However, when a swirl flow is formed in the combustion chamber 8, the end gas generation site changes in the circumferential direction of the cylinder 3, and accordingly, the direction in which a relatively large resonance occurs also changes. As described above, when the knock sensor 25 is disposed with the sensor axis S direction directed toward the air supply / exhaust direction, there is a risk of knocking detection failure.

  Therefore, the present inventors have intensively studied how to install the knock sensor 25 so that knocking detection failure does not occur even in such a case, and as a result, as a result, the axis P direction of the cylinder 3 (the vertical direction of the cylinder block 26 in FIG. 3). ), The knock sensor 25 is attached in a state where the sensor axis S is inclined at a predetermined angle θ (also referred to as an inclination angle θ) of 45 ° or more from the reference line L orthogonal to the crank axis K toward the side surface 26a of the cylinder block 26. Thus, it was found that knocking can be detected in a well-balanced manner and detection omission can be suppressed.

  This point will be described in detail. First, in order to detect in a well-balanced manner the resonance that occurs in the supply / exhaust direction, that is, the reference line L direction and the crank axis K direction orthogonal thereto, the reference line L and the crank axis K If the sensor axis S is tilted from the reference line L toward the side surface 26a of the cylinder block 26 by 45 °, which is obtained by dividing the center angle of the cylinder into two equal parts, the intensity components decomposed in the sensor axis S direction in the resonance intensity in each direction are equal. Therefore, it should be possible to detect resonance occurring in both directions with the same sensitivity.

  However, as a result of detailed examination, it was found that the resonance generated in both directions cannot always be detected with the same sensitivity only by tilting 45 °.

  First of all, due to the shape of the combustion chamber 8, a difference occurs in the intensity of resonance transmitted to the inner wall of the cylinder 3.

  Specifically, as indicated by the arrow lines a to d in FIG. 4, vibrations of the same strength are generated in four different directions with respect to the pent roof type combustion chamber 8, and the reference line L direction of the inner wall of the cylinder 3 The intensity of resonance (unit: Pa) transmitted in the direction of the crank axis K was calculated by CAE (Computer Aided Engineering). The results are shown in Table 1.

  As shown in Table 1, the intensity ratio (A / B) between the resonance (A) transmitted in the crank axis K direction and the resonance (B) transmitted in the reference line L direction is about 0.9, and is transmitted in the crank axis K direction. There was a tendency that the intensity of resonance was relatively small. The intensity ratio between the excitation directions a and b is expressed as the resonance intensity in the crank axis K direction of b / the resonance intensity in the reference line L direction of a.

  Secondly, a difference occurs in the intensity of vibration transmitted to the knock sensor 25 due to the influence of the shape of the cylinder block 26.

  That is, when the number of cylinders increases and the cylinder block 26 becomes relatively long in the direction of the crank axis K, the rigidity in that direction becomes relatively high and vibrations are hardly transmitted. Therefore, the actual measurement of how much the transmission sensitivity ratio representing the ease of transmission of the vibration transmitted in the direction of the reference line L in the cylinder block 26 and the vibration transmitted in the direction of the crank axis K is affected by the shape of the cylinder block 26. Based on the data. The results are shown in FIG. The transmission sensitivity ratio is represented by the ratio (C / D) of the ease of transmission between the vibration (C) transmitted in the crank axis K direction and the vibration (D) transmitted in the reference line L direction.

  As shown in FIG. 5, as the number of cylinders in the cylinder block 26 increases, the transmission sensitivity ratio tends to decrease, and there are some variations depending on the shape of the cylinder block 26. It was found that when the number is four, the transmission sensitivity ratio is approximately 0.8.

  Based on these results, the detection intensity ratio (E / F) between the intensity (E) in the crank axis K direction and the intensity (F) in the reference line L direction, which is detected by the knocking sensor 25, is calculated. did. The results are shown in Table 3.

  Table 3 shows the detected intensity ratio for each number of cylinders. For example, if the number of cylinders is 2, the intensity ratio 0.9 that is the first correction value and the second correction value that is the second correction value. The detection sensitivity ratio 0.840 is calculated by multiplying the transmission sensitivity ratio 0.933.

  Next, based on the calculated detection intensity ratio, an inclination angle θ at which the knock sensor 25 can detect the resonance in the crank axis K direction and the resonance in the reference line L direction with the same sensitivity was calculated.

  Specifically, as shown in FIG. 6, for example, if the number of cylinders is four, the detection intensities (reference values) that are the reference of 1 and 0.72 in the reference line L direction and the crank axis K direction, respectively. The angle at which the magnitude of the intensity component in the sensor axis S direction is the same is calculated for each of these reference intensities. For example, the reference intensity cos (90−θ) in the crank axis K direction may be obtained as θ satisfying the reference intensity cos θ in the reference line L direction.

  The inclination angle θ thus obtained is shown in Table 4 including the case where the detected intensity ratio varies by ± 10%.

  As shown in the table, for example, even when 10% variation is taken into consideration, the smallest inclination angle θ is 45.3 ° (when the number of cylinders is one), and is preferably set to 45 ° or more. It has been found that it is preferable to set the inclination angle θ larger as the number of cylinders increases.

  Specifically, as shown in FIG. 3, when the sensor axis S is tilted from the reference line L toward the side surface 26 a of the cylinder block 26 when viewed from above the cylinder block 26 in the axis P direction of the cylinder 3, the knock is performed. The sensor 25 may be attached to the side surface of the cylinder block 26 and set so that the inclination angle θ is within a range of at least 45 ° to 65 °.

  Further, for example, in the case of the present embodiment having four cylinders, the variation in Table 4 is varied according to the number of cylinders of the engine to be applied so that the inclination angle θ is set within a range of 51 ° to 58 °. What is necessary is just to set based on the considered range.

  By doing so, even if the end gas formation location in the combustion chamber 8 varies, the resonance of knocking occurring in either the reference line L direction or the crank axis K direction can be detected with the same sensitivity. Detection omission can be suppressed.

  In addition, this invention is not limited to said embodiment, Various other structures are included.

  That is, in the above embodiment, the inline engine has been described as an example. However, for example, a V-type engine may be used. In that case, since the upper part of the cylinder block is branched and formed in a V shape in the rear bank and the front bank having the same structure as the cylinder block 26 of the above embodiment, the same as the above embodiment for each bank. The knock sensor 25 may be attached as described above.

  In the above embodiment, the knock sensor 25 is attached to the side surface 26a on the intake side of the cylinder block 26, but it may be attached to the side surface 26b on the exhaust side as shown in FIG. Further, as shown in the figure, the sensor axis S may be inclined to either side of the reference line L. Moreover, since the engine main body referred to in the present invention is a concept including a cylinder head, a knock sensor 25 may be attached to the cylinder head.

  In the above embodiment, the flow rate control valve 22 is exemplified as the intake flow control means. However, the present invention is not limited to this, and for example, the flow of intake air may be controlled by controlling the opening degree of one intake valve 19.

It is a schematic plan view of the engine in this embodiment. It is a schematic sectional drawing of the engine in this embodiment. It is a top view showing the cylinder block part of the engine in this embodiment. It is a figure for demonstrating the excitation direction to a combustion chamber. It is a figure which shows the relationship between the number of cylinders provided in the cylinder block, and a transmission sensitivity ratio. It is a figure for demonstrating calculation of an inclination angle. It is a figure for demonstrating the attachment structure of another knock sensor. It is a figure for demonstrating the direction where the resonance of knocking generate | occur | produces.

Explanation of symbols

2 Crankshaft 3 Cylinder 8 Combustion chamber 10 Intake port 11 Exhaust port 14 Intake port opening 15 Exhaust port opening 19 Intake valve 21 Exhaust valve 22 Flow control valve (Intake flow control means)
23 Injector 25 Knock Sensor 26 Cylinder Block (Engine Body)
26a Intake side surface 26b Exhaust side surface 27 Sensor mounting boss θ Inclination angle (predetermined angle)
K Crank axis L Reference line S Sensor axis P Cylinder axis

Claims (13)

In an internal combustion engine having a pair of side surfaces substantially parallel to the crankshaft, including an engine main body provided with a cylinder therein, and having a knock sensor attached to the side surface,
A pent roof type combustion chamber is formed in the upper part of the cylinder, and an intake port and an exhaust port are connected so that the openings connected to the combustion chamber are arranged in a direction substantially perpendicular to the crankshaft.
The knock sensor includes a vibrator that displaces on a predetermined sensor axis in order to detect knocking that occurs in the combustion chamber,
A knock sensor mounting for an internal combustion engine, wherein the sensor axis is inclined at a predetermined angle of 45 ° or more toward a side surface of the engine body from a reference line orthogonal to the crankshaft when viewed in the axial direction of the cylinder Construction. The knock sensor mounting structure for an internal combustion engine according to claim 1,
The knock sensor mounting structure for an internal combustion engine, wherein the predetermined angle is set within a range of 45 ° to 65 °. The knock sensor mounting structure for an internal combustion engine according to claim 2,
A knock sensor mounting structure for an internal combustion engine, wherein a plurality of the intake ports are connected to the cylinder, and the openings of the plurality of intake ports are arranged in the axial direction of the crankshaft. The knock sensor mounting structure for an internal combustion engine according to claim 3,
A knock sensor mounting structure for an internal combustion engine, wherein at least one of the plurality of intake ports is provided with intake flow control means for changing flow resistance of intake air. The knock sensor mounting structure for an internal combustion engine according to claim 4,
A knock sensor mounting structure for an internal combustion engine, characterized in that a valve element capable of opening and closing is provided in the intake port as the intake flow control means. In the knock sensor mounting structure for an internal combustion engine according to any one of claims 1 to 5,
A knock sensor mounting structure for an internal combustion engine, wherein a plurality of the cylinders are provided in the engine body, and the plurality of cylinders are arranged in a line in the axial direction of the crankshaft. The knock sensor mounting structure for an internal combustion engine according to claim 6,
A knock sensor mounting structure for an internal combustion engine, wherein one knock sensor is provided for a plurality of cylinders arranged in a row. In the knock sensor mounting structure for an internal combustion engine according to any one of claims 1 to 5,
A knock sensor mounting structure for an internal combustion engine, wherein one cylinder is provided in the engine body, and the predetermined angle is set within a range of 45 ° to 51 °. In the knock sensor mounting structure for an internal combustion engine according to claim 6 or 7,
A knock sensor mounting structure for an internal combustion engine, wherein the engine main body is provided with two cylinders, and the predetermined angle is set within a range of 47 ° to 53 °. In the knock sensor mounting structure for an internal combustion engine according to claim 6 or 7,
A knock sensor mounting structure for an internal combustion engine, wherein the engine main body is provided with three cylinders, and the predetermined angle is set in a range of 49 ° to 55 °. In the knock sensor mounting structure for an internal combustion engine according to claim 6 or 7,
A knock sensor mounting structure for an internal combustion engine, wherein the engine main body is provided with four cylinders, and the predetermined angle is set in a range of 51 ° to 58 °. In the knock sensor mounting structure for an internal combustion engine according to claim 6 or 7,
A knock sensor mounting structure for an internal combustion engine, wherein the engine main body is provided with five cylinders, and the predetermined angle is set in a range of 54 ° to 60 °. In the knock sensor mounting structure for an internal combustion engine according to claim 6 or 7,
A knock sensor mounting structure for an internal combustion engine, wherein the engine body is provided with six cylinders, and the predetermined angle is set in a range of 56 ° to 62 °.

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