JP5915458B2 - Diesel engine combustion chamber structure - Google Patents

Description

  The present invention relates to a combustion chamber structure of a diesel engine.

  Conventionally, a combustion chamber structure of a diesel engine includes a main chamber (also referred to as a main combustion chamber), a sub chamber (also referred to as a sub combustion chamber), an injector (also referred to as a fuel injection nozzle) that injects fuel into the sub chamber, Some include a partition member having a communication hole that communicates the main chamber and the sub chamber (see, for example, Patent Documents 1 to 5). In Patent Documents 1 and 2, the partition member is fixed to the cylinder head. In Patent Document 3, the partition member can be slid along the partition direction between the main chamber and the sub chamber, the partition member is provided with a vortex chamber type communication hole and a pre-combustion chamber type communication hole, One of the communication holes is selected by sliding with an actuator. Further, in Patent Documents 4 and 5, a cylinder having a notch is provided on the side wall of the communication hole so as to be rotatable about an axis, and the opening area of the communication hole is variable by the rotation of the cylinder.

JP 2000-248939 A JP 2000-248940 A JP-A-9-324630 Japanese Patent Laid-Open No. 7-91253 JP-A-7-91254

  In the diesel engine, in the expansion stroke from the end of the compression stroke, the fuel injected from the injector into the sub chamber is ignited in the sub chamber, and combustion gas containing unburned fuel is formed. The combustion gas passes through the communication hole, is ejected into the main chamber, and burns while being further diffused. Here, the fuel injection period of the injector is determined by the required fuel injection amount. On the other hand, when the engine speed changes, the ratio of the main chamber volume in the combustion chamber changes even if the length of the fuel injection period is the same. For example, in the high engine speed range, the ratio of the main chamber volume in the latter half of the fuel injection period is increased compared to the low engine speed range. It is preferable to increase the combustion rate. By the way, in improving the combustion rate in the main chamber, the position of the communication hole with respect to the fuel spray injected from the injector, that is, the distance between the fuel spray and the communication hole is an important factor. In Nos. 1 to 5, since the distance between the fuel spray and the communication hole is constant, the combustion ratio in the main chamber could not be optimized with respect to the engine speed.

  The problem to be solved by the present invention is to provide a combustion chamber structure of a diesel engine that can improve the performance by changing the ratio of combustion in the main chamber and the sub chamber according to the operating state.

The above-mentioned problem can be solved by the combustion chamber structure of a diesel engine having the structure described in the claims.
According to the combustion chamber structure of a diesel engine according to claim 1, a main chamber, a sub chamber, an injector for injecting fuel into the sub chamber, and a partition member having a communication hole for connecting the main chamber and the sub chamber Combustion of a diesel engine with which the vortex is generated by flowing the air of the main chamber into the sub chamber through the communication hole in the compression stroke of the main chamber, and the fuel injected from the injector and the vortex are mixed It is a chamber structure, is provided with an actuator that allows the partition member to move between the main chamber and the sub chamber, moves the partition member, and a control means that controls the actuator in accordance with the operating state of the diesel engine. The means moves the partition member in a direction in which the distance of the communication hole with respect to the spray of fuel injected from the injector is closer as the speed of the diesel engine is higher. To control the sea urchin actuator. According to this configuration, the partition member is moved in a direction in which the distance of the communication hole with respect to the fuel spray is made closer by the actuator controlled by the control means as the diesel engine is on a higher rotation region side. As a result, combustion gas containing unburned fuel in the expansion stroke of the main chamber passes through the communication hole at an early stage and is injected into the main chamber, thereby increasing the combustion ratio of the main chamber compared to the combustion ratio of the sub chamber. The air utilization rate in the main room can be increased. Thereby, the generation of smoke can be reduced and the output can be improved. Therefore, by changing the combustion ratio in the main chamber and the sub chamber according to the operation state of the diesel engine, the performance in the entire region from the low rotation to the high rotation can be improved.

According to the combustion chamber structure of the diesel engine described in claim 2, the control means sets the distance of the communication hole to the spray of fuel injected from the injector in a low rotation range of the diesel engine and in a low load range. The actuator is controlled to move the partition member in a direction away from the actuator. This increases the combustion rate of the sub chamber compared to the combustion rate of the main chamber, and keeps the sub chamber at a high temperature even in a low load region where the fuel injection amount is small, thereby reducing unburned fuel and carbon monoxide emissions. Can be suppressed.

  According to the combustion chamber structure of a diesel engine according to claim 3, a plurality of partition members are stacked so as to be movable in the same direction, and the actuator is provided for each partition member, and the control means includes a plurality of partition members. By controlling the plurality of actuators so as to move the members synchronously, the distance of the communication hole with respect to the spray of fuel injected from the injector is varied, while the plurality of partition members are relatively moved. By controlling the actuator, the opening area of the series of communication holes by the plurality of partition members is varied. According to this configuration, the distance of the communication hole for the spray of fuel injected from the injector can be varied by moving the plurality of partition members synchronously by the plurality of actuators controlled by the control means. Further, by moving the plurality of partition members relatively by the plurality of actuators controlled by the control means, it is possible to vary the opening area of the series of communication holes formed by the plurality of partition members. That is, the swirl ratio can be increased by increasing the inclination of the series of connection holes as the opening area of the series of connection holes is reduced. As a result, it is possible to expect an improvement in exhaust performance and a startability improvement by reducing smoke and unburned gas at low loads. Further, the swirl ratio can be reduced by decreasing the inclination of the series of connection holes as the opening area of the series of connection holes is increased. As a result, it is possible to reduce the aperture loss and improve the fuel consumption and output performance at high loads.

  According to the combustion chamber structure of the diesel engine described in claim 4, the partition member is rotatable with the circumferential direction as the moving direction. Therefore, the position of the communication hole can be moved by rotating the partition member.

  According to the combustion chamber structure of the diesel engine described in claim 5, the number of communication holes of the partition member is the same as the number of injection holes of the injector. Therefore, the spray of fuel injected from each injection hole of the injector can be quickly mixed with the vortex flow that has flowed into the sub chamber from each communication hole.

It is sectional drawing which shows the combustion chamber structure of the diesel engine concerning Embodiment 1. FIG. It is sectional drawing which shows a subchamber. It is a top view which shows a subchamber. It is explanatory drawing which shows the change of the distance of the communication hole with respect to spray of fuel. It is explanatory drawing which shows the change of the opening area of a series of connecting holes. It is explanatory drawing which shows the change of the opening area of a series of connection holes concerning Embodiment 2. FIG. It is explanatory drawing which shows the state which made small the opening area of a series of connecting holes. It is a top view which shows the partition member concerning Embodiment 3.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[Embodiment 1]
Embodiment 1 will be described. As shown in FIG. 1, the sub-chamber diesel engine 10 has a cylinder head 14 mounted on a cylinder block 12. In the cylinder wall 12a of the cylinder block 12, that is, in the cylinder bore, a piston 16 is disposed so as to be capable of reciprocating in the axial direction (vertical direction in FIG. 1). A main chamber 18 is formed by the cylinder wall 12 a of the cylinder block 12, the cylinder head 14 and the piston 16. The cylinder head 14 is formed with a hollow cylindrical sub chamber 20. The main chamber 18 and the sub chamber 20 are concentric. The diesel engine 10 is a two-cycle diesel engine, for example, and is mounted on a vehicle, for example.

  An injector 22 for injecting fuel into the sub chamber 20 is provided on the upper wall portion of the sub chamber 20 of the cylinder head 14. The injector 22 is disposed concentrically with respect to the sub chamber 20. The tip (lower end) of the injector 22 is exposed in the sub chamber 20. In the lower end portion of the injector 22, four (two are shown in FIG. 2) injection holes 23 are formed at equal intervals in the circumferential direction. The injector 22 injects fuel from each injection hole 23 radially and outward in the radial direction of the sub chamber 20 (see arrow Y1 in FIG. 2). Further, the fuel spray F injected from each injection hole 23 of the injector 22 is shown by a two-dot chain line in FIG.

  As shown in FIG. 1, the lower surface opening of the sub chamber 20 is partitioned by two upper and lower plate-like partition members 25 arranged concentrically with respect to the sub chamber 20. The main chamber 18 and the sub chamber 20 are partitioned by both partition members 25. Since both the partition members 25 have the same shape, the upper partition member 25 will be described below. The partition member 25 is formed in a disk shape. Four communication holes 27 are formed in the outer circumferential portion of the partition member 25 at equal intervals in the circumferential direction (see FIG. 3). The number of communication holes 27 in the partition member 25 is four, which is the same as the number of injection holes 23 in the injector 22. The communication hole 27 is inclined at a predetermined inclination angle θ1 (see FIG. 2) with respect to a straight line (straight line parallel to the axis) 27L extending in the plate thickness direction (vertical direction in FIG. 2) of the partition member 25. The upper surface opening and the lower surface opening are formed so as to be shifted in the circumferential direction (in this embodiment, linear in the tangential direction of the partition member 25) (see FIG. 3). In the present embodiment, the upper surface opening is shifted in the counterclockwise direction with respect to the lower surface opening in plan view (see FIG. 3).

  As shown in FIG. 3, the partition member 25 is arranged to be rotatable with respect to the cylinder head 14 with a circumferential direction as a moving direction. The cylinder head 14 is provided with an actuator 30 that rotates the partition member 25. For example, an air cylinder that uses negative pressure generated by a negative pressure pump mounted as a negative pressure source such as a brake booster in a vehicle is used as the actuator 30. A main body 31 of the actuator 30 is rotatably connected to the cylinder head 14 via a pin 32. Further, the distal end portion of the telescopic rod 33 of the actuator 30 is rotatably connected to a connecting portion 28 protruding from the outer peripheral portion of the partition member 25 via a pin 34.

  An electronic control device 36 composed of an ECU is electrically connected to a control device (not shown) such as an electromagnetic valve disposed in a negative pressure control circuit including the actuator 30. The electronic control unit 36 controls the actuator 30 (including the control device of the negative pressure control circuit) so as to vary the rotation position of the partition member 25 according to the operating state of the diesel engine 10. The electronic control device 36 corresponds to “control means” in this specification.

  As shown in FIG. 2, the lower partition member 25 is formed in the same shape as the upper partition member 25. For convenience of explanation, the upper partition member 25 is referred to as a first partition member 25 (reference numeral, A), and the lower partition member 25 is referred to as a second partition member 25 (reference numeral, B). The lower partition member 25B) is stacked on the lower surface side of the upper partition member 25A in a stacked manner so as to be relatively rotatable. The rotation centers of both partition members 25A and 25B are arranged on the same axis. Both partition members 25A and 25B are positioned by positioning means (not shown) in the axial direction (vertical direction in FIG. 1). Further, the communication holes 27 of the partition members 25A and 25B communicate with each other, so that a series of communication holes 27 (denoted by reference numerals and S) for connecting the main chamber 18 and the sub chamber 20 are formed. The main chamber 18, the sub chamber 20, and the series of communication holes 27S constitute a combustion chamber. Further, as described above, since the upper surface opening and the lower surface opening of the communication hole 27 are shifted in the circumferential direction, the sub chamber is passed from the main chamber 18 through the series of communication holes 27S in the compression stroke of the main chamber 18. An eddy current (see arrow Y2 in FIG. 1) due to the air flowing into 20 can be generated.

  The positional relationship between the fuel spray F injected from each injection hole 23 of the injector 22 and the series of communication holes 27S will be described. FIG. 4 is an explanatory view showing a change in the distance of the communication hole with respect to fuel spray. 4A shows a state where the distance L of the series of communication holes 27S with respect to the fuel spray F is long (long), and FIGS. 4B to 4D show that the distance L is gradually reduced (short). It shows the process. As shown in FIGS. 4A to 4D, both partition members 25 are synchronously rotated in a state where the connecting holes 27 of the partition members 25A and 25B are aligned so as to be concentric. Thus, the fuel spray F injected from the injector 22 (specifically, the spray F in the vicinity of the circumference on the upper surface of the first partition member 25A passing through the center of the upper surface opening of the communication hole 27 corresponds). The distance L between the series of communication holes 27S can be increased or decreased (see FIGS. 4A to 4D). That is, the distance L of the series of communication holes 27S with respect to the fuel spray F can be varied. Here, the distance L is between the center of the upper surface opening of the series of communication holes 27S and the center of the spray F on the circumferential line passing through the center of the upper surface opening of the communication hole 27 on the upper surface of the first partition member 25A. It means distance. Note that the distance L may be changed stepwise or gradually by the control of both actuators 30 by the electronic control unit 36.

  The opening area of the series of communication holes 27S formed by the partition members 25A and 25B will be described. FIG. 5 is an explanatory diagram showing changes in the opening area of a series of communication holes. FIG. 5A shows a state in which the opening area A of the series of communication holes 27S is small, and FIGS. 5B to 5C show a process in which the opening area A gradually increases. As shown in FIGS. 5A to 5C, the opening area A of the series of communication holes 27S can be varied by relatively rotating the partition members 25A and 25B. The smaller the opening area A is, the higher the flow velocity of the air flowing into the sub chamber. As the opening area A is increased or decreased, the swirl ratio can be increased or decreased by changing the inclination of the series of communication holes 27S, that is, the inclination angle θ2. As shown in FIG. 5A, when the opening area A is small and the inclination angle θ2 is large, the swirl ratio is large. Further, as shown in FIG. 5C, when the opening area A is large and the inclination angle θ2 is small, the swirl ratio is small. Note that the opening area A may be changed stepwise or gradually by the control of both actuators 30 by the electronic control unit 36.

  The diesel engine 10 (see FIG. 1) is compressed into the sub chamber 20 by the air in the main chamber 18 flowing into the sub chamber 20 through a series of communication holes 27S in the compression stroke of the main chamber 18. A vortex composed of high-temperature and high-pressure air (see arrow Y2 in FIG. 1) is generated, and fuel is injected from each injection hole 23 of the injector 22 into the vortex. The fuel injection starts near the end of the compression process (piston top dead center) and continues throughout the expansion stroke until the fuel injection amount reflecting the operating state, particularly the engine load, is completed. The fuel injected from the injector is ignited with a time lag in the sub chamber 20 to form a combustion gas including unburned fuel. The combustion gas is jetted into the main chamber 18 through the series of communication holes 27S, and continues to burn while being diffused using the air in the main chamber 18. Further, the piston 16 descends as the pressure in the main chamber 18 rises. Thereafter, the burnt gas that has been combusted is discharged from the main chamber 18 to an exhaust passage (not shown).

  According to the combustion chamber structure of the diesel engine 10 (see FIG. 1), when the diesel engine 10 is in a low rotation range and a low load, the actuator 30 controlled by the electronic control unit 36 (see FIG. 3) Both partition members 25A and 25B are synchronously rotated in a direction to increase the distance L of the series of communication holes 27S with respect to the spray F of the injected fuel (see FIG. 4A). Thereby, the combustion rate of the sub chamber 20 is increased compared to the combustion rate of the main chamber 18, and the sub chamber 20 can be kept at a high temperature even at a low load where the fuel injection amount is small, for example, during idling operation. Thereby, generation | occurrence | production and discharge | emission of unburned fuel and carbon monoxide can be suppressed.

Further, in the high engine speed range of the diesel engine 10, the partition members 25 </ b> A and 25 </ b> B are synchronously moved in a direction in which the distance L of the series of communication holes 27 </ b> S with respect to the fuel spray F is made closer by the actuator 30 controlled by the electronic control unit 36. (See FIG. 4D). Thereby, the combustion gas containing the unburned fuel generated from the fuel spray F and the vortex (see arrow Y2 in FIG. 1) in the expansion stroke of the main chamber 18 is quickly transferred from the sub chamber 20 to the main chamber 18. Erupts. As described above, fuel injection starts near the top dead center of the piston and ends in the middle of the expansion stroke. The ratio of the main chamber volume in the volume of the combustion chamber is, for example, 50% at the top dead center of the piston. However, since the piston 16 is going down in the latter half of the fuel injection period, the ratio of the main chamber volume is generally the sub chamber volume. Bigger than. Assuming the same fuel injection amount, that is, the same fuel injection period, the higher the rotation speed side, the lower the position of the piston in the latter half of the fuel injection period, so the ratio of the main chamber volume to the combustion chamber volume is Further increase. On the other hand, the combustion rate of the main chamber 18 is increased as compared with the combustion rate of the sub chamber 20 by ejecting the combustion gas from the sub chamber 20 to the main chamber 18 earlier as the speed increases. By increasing the air utilization rate in the main chamber 18 according to the increase in the volume ratio, the generation of smoke can be reduced and the output can be improved.
Therefore, by changing the combustion ratio in the main chamber 18 and the sub chamber 20 according to the operation state of the diesel engine 10 (see FIG. 1), the performance in the entire region from the low rotation to the high rotation can be improved. .

  A series of fuel sprays injected from the injector 22 with respect to the spray F is obtained by synchronously rotating the two partition members 25A and 25B by the two actuators 30 controlled by the electronic control unit 36 (see FIG. 3). The distance L of the communication hole 27S can be varied (see FIGS. 4A to 4D). Further, the two partition members 25A and 25B are relatively rotated by the two actuators 30 controlled by the electronic control unit 36, whereby the opening area A of the series of communication holes 27S by the plurality of partition members 25 is variable. (See FIGS. 5 (a) to 5 (c)).

  For example, in a low rotation range of the diesel engine 10, both partition members 25 </ b> A and 25 </ b> B are synchronously rotated in a direction in which the distance L of the series of communication holes 27 </ b> S with respect to the fuel spray F is distanced (FIG. 4A). 2), the second partition member 25B is rotated clockwise relative to the first partition member 25A in plan view (see FIG. 3), thereby reducing the opening area A of the series of communication holes 27S. Accordingly, the swirl ratio can be increased by increasing the inclination (inclination angle θ2) of the series of communication holes 27S (see FIG. 5A). As a result, it is possible to expect an improvement in exhaust performance and a startability improvement by reducing smoke and unburned gas at low loads.

  Further, in the high speed range of the diesel engine 10, the partition members 25A and 25B are synchronously rotated in the direction in which the distance L of the series of communication holes 27S with respect to the fuel spray F is reduced (FIG. 4 (d)). 2), the second partition member 25B is rotated counterclockwise in a plan view (see FIG. 3) with respect to the first partition member 25A, thereby increasing the opening area A of the series of communication holes 27S. Accordingly, the swirl ratio can be reduced by reducing the inclination (inclination angle θ2) of the series of communication holes 27S (see FIG. 5C). As a result, it is possible to reduce the aperture loss and improve the fuel consumption and output performance at high loads.

  Further, by simultaneously changing the distance L of the series of communication holes 27S with respect to the fuel spray F and the opening area A of the series of communication holes 27S according to the operating state, the entire range from low rotation to high rotation is achieved. Appropriate combustion can be obtained, and further performance improvements such as output performance and exhaust performance can be achieved.

  Moreover, both partition members 25A and 25B can be rotated with the circumferential direction as the moving direction. Therefore, the communication hole 27 can be moved by turning both the partition members 25A and 25B.

  Further, the four communication holes 27 of the partition member 25 are the same as the four injection holes 23 (fuel spray F) of the injector 22 (see FIG. 3). Therefore, the fuel spray F injected from each injection hole 23 of the injector 22 can be quickly mixed into the vortex flow (see arrow Y2 in FIG. 1) flowing into the sub chamber 20 from each communication hole 27. it can.

[Embodiment 2]
A second embodiment will be described. Since the present embodiment is a modification of the first embodiment, the changed portion will be described and redundant description will be omitted. FIG. 6 is an explanatory diagram showing changes in the opening area of a series of communication holes. 6A shows a state in which the opening area A of the series of communication holes 27S is small, and FIGS. 6B to 6C show a process in which the opening area A increases stepwise. As shown in FIGS. 6A to 6C, in the present embodiment, the number of partition members 25 in the first embodiment is increased by one to three. The third partition member 25 is referred to as a third partition member 25 (reference numeral C). The third partition member 25C is stacked on the lower surface side of the second partition member 25B so as to be rotatable and relatively rotatable. The rotation centers of the three partition members 25A, 25B, and 25C are arranged on the same axis. Note that the third partition member 25C includes an actuator 30 (see FIG. 3) in the same manner as the other partition members 25A and 25B.

  In the present embodiment, the total thickness of the three partition members 25A, 25B, and 25C is set to be equal to the total thickness of the two partition members 25A and 25B in the first embodiment. That is, the plate thickness of one partition member 25 is set to 2/3 of the plate thickness of one partition member 25 in the first embodiment. Thereby, the level | step difference which arises between the internal peripheral surfaces by the communication holes 27 of adjacent partition member 25A, 25B, 25B, 25C can be made small, and the fall of a flow coefficient can be prevented.

  Further, in a state where the opening area A of the series of communication holes 27S is reduced (see FIG. 6A), the second partition member 25B is viewed in plan with respect to the first partition member 25A and the third partition member 25C. In FIG. 7, the swirl ratio can be further increased by further reducing the opening area A of the series of communication holes 27S, as shown in FIG.

[Embodiment 3]
A third embodiment will be described. Since the present embodiment is a modification of the first embodiment, the changed portion will be described and redundant description will be omitted. FIG. 8 is a plan view showing the partition member.
As shown in FIG. 8, in this embodiment, the injector 22 has nine injection holes (not shown), and nine fuel sprays F are injected radially from each injection hole. The number of communication holes 27 in the partition member 25 is nine, which is the same as the number of injection holes in the injector 22. Further, the communication hole 27 is formed such that the upper surface opening and the lower surface opening are shifted in an arc shape in the circumferential direction in the plate thickness direction of the partition member 25.

  The present invention is not limited to the above-described embodiment, and modifications can be made without departing from the gist of the present invention. For example, the present invention can be applied not only to a two-cycle diesel engine but also to a four-cycle diesel engine. Moreover, the partition member 25 can also be comprised by 1 sheet. Moreover, the some partition member 25 can also be comprised by 4 or more sheets. Further, the partition member 25 is not limited to rotation, and may move in a linear direction as long as it is along the partition direction between the main chamber 18 and the sub chamber 20. Further, the communication member 27 of the partition member 25 can be at least one. The number of communication holes 27 may not be the same as the number of sprays F. The actuator 30 is not limited to an air cylinder, and other fluid pressure cylinders, electric cylinders, electric motors, electromagnetic solenoids, or the like can be used.

DESCRIPTION OF SYMBOLS 10 ... Diesel engine 18 ... Main chamber 20 ... Sub chamber 22 ... Injector 25 ... Partition member 25A ... First partition member 25B ... Second partition member 25C ... Third partition member 27 ... Communication hole 27S ... A series of communication holes 30 ... Actuator 36. Electronic control device (control means)
F ... Fuel spray

Claims (5)

The main room,
Sub-room,
An injector for injecting fuel into the sub chamber;
A partition member having a communication hole connecting the main chamber and the sub chamber,
Diesel in which the air in the main chamber is caused to flow into the sub chamber through the communication hole in the compression stroke of the main chamber to generate a vortex and to mix the fuel injected from the injector and the vortex An engine combustion chamber structure,
The partition member is movable between the main chamber and the sub chamber,
An actuator for moving the partition member, and a control means for controlling the actuator according to the operating state of the diesel engine,
The control means controls the actuator so as to move the partition member in a direction in which the distance of the communication hole with respect to the spray of fuel injected from the injector is closer toward a higher rotation region side of the diesel engine. Diesel engine combustion chamber structure. A combustion chamber structure for a diesel engine according to claim 1,
The control means controls the actuator so as to move the partition member in a direction in which the distance of the communication hole with respect to the spray of fuel injected from the injector is increased in a low rotation range and a low load range of a diesel engine. A combustion chamber structure of a diesel engine characterized by A combustion chamber structure for a diesel engine according to claim 1 or 2,
A plurality of the partition members are stacked so as to be movable in the same direction,
The partition member includes the actuator,
The control means controls the plurality of actuators so as to move the plurality of partition members synchronously, thereby varying the distance of the communication hole with respect to the spray of fuel injected from the injector. A combustion chamber structure for a diesel engine, wherein an opening area of a series of communication holes by the plurality of partition members is varied by controlling the plurality of actuators so as to relatively move the partition members. A combustion chamber structure for a diesel engine according to any one of claims 1 to 3,
A combustion chamber structure of a diesel engine, wherein the partition member is rotatable with a circumferential direction as a moving direction. It is a combustion chamber structure of the diesel engine as described in any one of Claims 1-4,
The combustion chamber structure of a diesel engine, wherein the number of communication holes of the partition member is the same as the number of injection holes of the injector.

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