JP7517158B2 - Turbocharger - Google Patents

Description

The present invention relates to a turbocharger.

The internal combustion engine described in Patent Document 1 is equipped with a turbocharger. The turbocharger includes a compressor wheel that supercharges the intake air, and a compressor housing that houses the compressor wheel. The compressor housing includes an accommodation space that houses the compressor wheel, and an introduction passage that communicates with the accommodation space and introduces the intake air into the accommodation space. The compressor housing also includes an annular space that surrounds the accommodation space, and a communication passage that communicates between the accommodation space and the annular space. The annular space is connected to the introduction passage.

In the turbocharger of Patent Document 1, when the pressure of the intake air in the storage space becomes higher than the pressure of the intake air in the introduction passage, a portion of the intake air in the storage space flows back to the introduction passage via the communication passage and the annular space. As a result, so-called surging, in which intake air flows back directly from the storage space to the introduction passage, is suppressed.

JP 2014-051915 A

In a turbocharger such as that described in Patent Document 1, when a portion of the intake air in the accommodation space flows back into the introduction passage through the communication passage and the annular space, the flow of the intake air can generate a resonance sound. Depending on the structure of the annular space and the communication passage in the turbocharger, the resonance sound may become excessively loud.

A turbocharger for solving the above problem is a turbocharger including a compressor wheel that supercharges intake air, a housing body that houses the compressor wheel, and a cylindrical inlet member that is fixed to the housing body and defines a passage for the intake air to be introduced into the compressor wheel, wherein the housing body includes a first wall portion that, when viewed from a direction along the rotation axis of the compressor wheel, extends in an annular shape so as to surround the rotation axis, a second wall portion that, when viewed from a direction along the rotation axis, extends in an annular shape so as to surround the first wall portion, an intermediate wall portion that connects the first wall portion and the second wall portion, a storage space that is a space surrounded by the first wall portion and that houses the compressor wheel, and a storage space that is defined by the first wall portion, the second wall portion, and the intermediate wall portion. The inlet member is adjacent to the storage space in the direction along the rotation axis, and includes an introduction passage that introduces intake air into the storage space, and a communication space that surrounds the introduction passage when viewed from the direction along the rotation axis and communicates the annular space and the introduction passage. When the resonance frequency in the annular space is the air column resonance frequency, the resonance frequency in the slit is the inlet branch resonance frequency, and the resonance frequency in the communication space is the outlet branch resonance frequency, the air column resonance frequency is smaller than the outlet branch resonance frequency, and the value obtained by dividing the inlet branch resonance frequency by the outlet branch resonance frequency is greater than 1.7.

The inventors have confirmed that the above-mentioned relationship between the inlet branch resonance frequency, the outlet branch resonance frequency, and the air column resonance frequency results in smaller resonance sounds than in other relationships. Therefore, the above-mentioned configuration can prevent excessively large resonance sounds from being generated.

FIG. 1 is a schematic diagram of an internal combustion engine. FIG. 3 is a cross-sectional view showing the peripheral configuration of a compressor housing. 3 is a cross-sectional view taken along line 3-3 in FIG. 2 . 4 is a cross-sectional view taken along line 4-4 in FIG. 2 . 5 is a cross-sectional view taken along line 5-5 in FIG. 4. FIG. 4 is an explanatory diagram showing the relationship between the outlet branch resonance frequency and the air column resonance frequency. 5 is an explanatory diagram showing the relationship between a value obtained by dividing an inlet branch resonance frequency by an outlet branch resonance frequency and the volume of a resonance sound. FIG.

<General Configuration of Internal Combustion Engine>
An embodiment of the present invention will now be described with reference to Figures 1 to 7. First, a schematic configuration of an internal combustion engine 10 of a vehicle will be described.

As shown in FIG. 1, the internal combustion engine 10 includes an intake passage 11, a plurality of cylinders 12, an exhaust passage 13, a plurality of fuel injection valves 16, and a turbocharger 20. The intake passage 11 introduces intake air from outside the internal combustion engine 10. Each cylinder 12 is connected to the intake passage 11. The fuel injection valve 16 injects fuel into the cylinder 12. There is one fuel injection valve 16 for each cylinder 12. The cylinder 12 mixes fuel and intake air and burns the mixture. The combustion in the cylinder 12 rotates a crankshaft (not shown). The exhaust passage 13 is connected to each cylinder 12. The exhaust passage 13 discharges exhaust gas from each cylinder 12. Note that FIG. 1 illustrates only one of the multiple sets of cylinders 12 and fuel injection valves 16.

The turbocharger 20 includes a compressor housing 21, a bearing housing 22, a turbine housing 23, a compressor wheel 31, a shaft 32, and a turbine wheel 33.

The compressor housing 21 is located midway through the intake passage 11. The turbine housing 23 is located midway through the exhaust passage 13. The bearing housing 22 is connected to each of the compressor housing 21 and the turbine housing 23. In other words, the compressor housing 21 and the turbine housing 23 are connected via the bearing housing 22. In this way, the turbocharger 20 is provided across the intake passage 11 and the exhaust passage 13.

The turbine housing 23 houses the turbine wheel 33. The bearing housing 22 houses the shaft 32. The bearing housing 22 rotatably supports the shaft 32 via a bearing (not shown). A first end of the shaft 32 is connected to the turbine wheel 33. The compressor housing 21 houses the compressor wheel 31. The compressor wheel 31 is connected to a second end of the shaft 32. That is, the compressor wheel 31 is connected to the turbine wheel 33 via the shaft 32.

When the turbine wheel 33 rotates due to the flow of exhaust gas inside the turbine housing 23, the compressor wheel 31 rotates together via the shaft 32. As the compressor wheel 31 rotates, the intake air inside the compressor housing 21 is supercharged.

The turbine housing 23 is provided with a bypass passage 23A. The bypass passage 23A connects the space upstream of the turbine wheel 33 with the space downstream of the turbine wheel 33.

The turbocharger 20 includes a wastegate valve 41, a link mechanism 42, and an actuator 43. The wastegate valve 41 is located near the bypass passage 23A. The actuator 43 is connected to the wastegate valve 41 via the link mechanism 42. The actuator 43 transmits driving force to the wastegate valve 41 via the link mechanism 42. The wastegate valve 41 opens and closes the bypass passage 23A. As a result, the amount of exhaust gas flowing through the turbine wheel 33 is adjusted, and the rotational speed of the turbine wheel 33 is adjusted.

<Compressor housing peripheral configuration>
Next, a specific description will be given of the peripheral configuration of the compressor housing 21. In the following, as shown in Fig. 2, among the directions along the rotation axis 31Z of the compressor wheel 31, the direction toward the bearing housing 22 side as viewed from the compressor housing 21 is referred to as a first direction, and the opposite direction is referred to as a second direction. In addition, the direction perpendicular to the rotation axis 31Z as viewed from the rotation axis 31Z is abbreviated to a radial direction.

2, the compressor wheel 31 includes a shaft portion 31A and a plurality of wings 31B. The shaft portion 31A is connected to the shaft 32. The shaft portion 31A extends along the shaft 32. The diameter of the shaft portion 31A increases toward the first direction. The rotation axis 31Z of the shaft portion 31A is coaxial with the rotation axis of the shaft 32. The wings 31B protrude radially from the shaft portion 31A. The wings 31B extend over substantially the entire area of the dimensions of the shaft portion 31A along the rotation axis 31Z. The wings 31B are positioned at equal intervals so as to be spaced apart from each other in the circumferential direction of the rotation axis 31Z. In this embodiment, the number of wings 31B is six. Note that the wings 31B are not shown in FIG. 4.

As shown in FIG. 2, the compressor housing 21 includes a housing body 60 and an inlet member 80. The housing body 60 includes a first wall portion 61, a second wall portion 62, a plurality of intermediate wall portions 63, a cylindrical wall portion 64, and an arc portion 65.

The cylindrical wall portion 64 has a generally cylindrical shape. The central axis of the cylindrical wall portion 64 is generally along the rotation axis 31Z. The second wall portion 62 has a generally cylindrical shape, similar to the cylindrical wall portion 64. Therefore, as shown in FIG. 4, the second wall portion 62 extends in an annular shape when viewed from a direction along the rotation axis 31Z. As shown in FIG. 2, the central axis of the second wall portion 62 is generally along the rotation axis 31Z. The second wall portion 62 is connected to the end of the cylindrical wall portion 64 in the first direction, i.e., the right end in FIG. 2. The inner diameter of the second wall portion 62 is smaller than the inner diameter of the cylindrical wall portion 64. Therefore, a step is generated at the boundary between the second wall portion 62 and the cylindrical wall portion 64. The arc portion 65 extends in a generally arc shape so as to surround the outer periphery of the cylindrical wall portion 64 and the second wall portion 62.

As shown in FIG. 4, the first wall portion 61 extends in an annular shape when viewed from the direction along the rotation axis 31Z. As shown in FIG. 2, the end of the first wall portion 61 in the first direction is connected to the end of the second wall portion 62 in the first direction. The end of the first wall portion 61 in the second direction is radially separated from the end of the second wall portion 62 in the second direction. That is, at the end of the first wall portion 61 in the second direction, the diameter of the first wall portion 61 is smaller than the diameter of the second wall portion 62. Therefore, as shown in FIG. 4, the first wall portion 61 is surrounded by the second wall portion 62 when viewed from the direction along the rotation axis 31Z. As shown in FIG. 2, the end of the first wall portion 61 in the second direction coincides with the end of the second wall portion 62 in the second direction in the direction along the rotation axis 31Z.

As shown in FIG. 4, the intermediate wall portion 63 is located between the first wall portion 61 and the second wall portion 62. The intermediate wall portion 63 connects the outer surface of the first wall portion 61 and the inner surface of the second wall portion 62. As shown in FIG. 2, the first direction end of the intermediate wall portion 63 is connected to the bottom surface of the first wall portion 61. The second direction end of the intermediate wall portion 63 coincides with the second direction ends of the first wall portion 61 and the second wall portion 62 in the direction along the rotation axis 31Z. As shown in FIG. 4, each intermediate wall portion 63 is located at equal intervals so as to be spaced apart from each other in the circumferential direction of the rotation axis 31Z. In this embodiment, the number of intermediate wall portions 63 is three.

As shown in FIG. 2, the housing body 60 has an internal space including a large diameter space 71, an accommodating space 72, a connecting passage 73, a scroll passage 74, a slit 76, and a number of annular spaces 77.

The accommodation space 72 is a space surrounded by the first wall portion 61. The accommodation space 72 accommodates the compressor wheel 31. The large diameter space 71 is located in the second direction as viewed from the accommodation space 72. The large diameter space 71 is a space surrounded by the cylindrical wall portion 64. The shape of the large diameter space 71 is approximately cylindrical.

The scroll passage 74 is located inside the arc portion 65. The scroll passage 74 extends in the circumferential direction so as to surround the compressor wheel 31. The downstream end of the scroll passage 74 is connected to the intake passage 11 downstream of the compressor housing 21.

The connecting passage 73 is located between the storage space 72 and the scroll passage 74, and connects the storage space 72 and the scroll passage 74. A part of the wall that defines the connecting passage 73 is formed by the end face of the bearing housing 22. When viewed from the direction along the rotation axis 31Z, the shape of the connecting passage 73 is approximately annular.

As shown in FIG. 4, the annular space 77 is a space partitioned by the first wall portion 61, the second wall portion 62, and the intermediate wall portion 63. In this embodiment, the annular space 77 is divided by three intermediate wall portions 63, and there are three annular spaces 77 in total. In addition, when viewed from a direction along the rotation axis 31Z, the shape of each annular space 77 is approximately arc-shaped.

As shown in FIG. 2, the slit 76 penetrates the first wall portion 61 in the radial direction. The slit 76 extends over the entire circumferential area of the first wall portion 61 and has a generally annular shape. As shown in FIG. 5, the slit 76 reaches halfway in the radial direction of the intermediate wall portion 63. Therefore, the slit 76 divides a portion of the intermediate wall portion 63 in the direction along the rotation axis 31Z.

As shown in FIG. 2, the inlet member 80 is located in the large diameter space 71 in the housing body 60. The inlet member 80 has an overall annular shape. The inlet member 80 includes an annular portion 81, an outer peripheral wall portion 82, an inner peripheral wall portion 83, and a plurality of vanes 84. The outer diameter of the annular portion 81 is approximately the same as the inner diameter of the large diameter space 71. The inner diameter of the annular portion 81 is approximately the same as the inner diameter of the first wall portion 61. The central axis of the annular portion 81 approximately coincides with the rotation axis 31Z.

The outer peripheral wall portion 82 protrudes from the end face of the annular portion 81 in the first direction. The outer peripheral wall portion 82 extends over the entire circumferential area of the annular portion 81 so as to follow the outer peripheral edge of the annular portion 81. In this embodiment, the annular portion 81 and the outer peripheral wall portion 82 are inserted into the large diameter space 71, thereby fixing the inlet member 80 to the housing main body 60. One example of a fixing configuration of the inlet member 80 and the housing main body 60 is a press fit of the annular portion 81 and the outer peripheral wall portion 82 into the large diameter space 71.

2, the inner circumferential wall portion 83 protrudes from the end face of the annular portion 81 in the first direction. As shown in FIG. 3, the inner circumferential wall portion 83 extends over the entire circumferential area of the annular portion 81 so as to follow the inner peripheral edge of the annular portion 81. Therefore, the inner circumferential wall portion 83 is spaced apart from the outer circumferential wall portion 82 in the radial direction. As shown in FIG. 2, the end of the inner circumferential wall portion 83 in the first direction is located on the second direction side relative to the end of the outer circumferential wall portion 82 in the first direction. In other words, there is a gap between the end of the inner circumferential wall portion 83 in the first direction and the end of the first wall portion 61 in the second direction.

As shown in FIG. 2, the vanes 84 protrude from the end face of the annular portion 81 in the first direction. The end of the vane 84 in the first direction is at the same position as the end of the outer peripheral wall portion 82 in the first direction in the direction along the rotation axis 31Z. As shown in FIG. 3, the vanes 84 extend to connect the outer peripheral wall portion 82 and the inner peripheral wall portion 83. The vanes 84 are positioned at equal intervals while being spaced apart from each other in the circumferential direction centered on the rotation axis 31Z. In this embodiment, the number of vanes 84 is nine.

As shown in FIG. 2, the inlet member 80 has an introduction passage 91 and a communication space 92 as the internal space of the inlet member 80. The introduction passage 91 is a space on the radially inner side defined by the annular portion 81 and the inner circumferential wall portion 83. The introduction passage 91 is adjacent to the accommodation space 72 in the second direction. The upstream end of the introduction passage 91 is connected to the intake passage 11 upstream of the compressor housing 21. Therefore, the introduction passage 91 introduces intake air into the accommodation space 72 via the introduction passage 91.

The communication space 92 is a space partitioned by the annular portion 81, the outer peripheral wall portion 82, the inner peripheral wall portion 83, and the vanes 84. In this embodiment, the communication space 92 is divided by nine vanes 84, and there are a total of nine communication spaces 92. The communication space 92 communicates with the annular space 77 and the introduction passage 91.

<Configuration regarding resonance frequency>
Next, the configuration of the compressor housing 21 with respect to the resonance frequency will be specifically described. In the following, as shown in FIG. 4, the volume of the annular space 77 is defined as volume VB. The volume VB is the total volume of the annular space 77 divided into three. As shown in FIG. 3, the volume of the communication space 92 is defined as volume VC. The volume VC is the total volume of the communication space 92 divided into nine. As shown in FIG. 4, the opening cross-sectional area of the annular space 77 at the end in the second direction is defined as area S. The area S is the total opening cross-sectional area of the annular space 77 divided into three. As shown in FIG. 5, the radial length of the slit 76 is defined as inlet length HA. The inlet length HA is the length from the radial inner end to the radial outer end of the slit 76. In this embodiment, the position of the radial inner end of the slit 76 is the same as the position of the inner circumferential surface of the first wall portion 61. The radial outer end of the slit 76 is the radial outer end of the portion of the slit 76 that is provided in the intermediate wall portion 63. As shown in Fig. 2, the radial length of the communication space 92 is defined as the outlet length HC. The outlet length HC is the radial length from the inner peripheral surface of the inner peripheral wall portion 83 to the inner peripheral surface of the outer peripheral wall portion 82. As shown in Fig. 2, the distance between the slit 76 and the communication space 92 in the direction along the rotation axis 31Z is defined as the center-to-center distance L. Here, the center of the gap between the first direction end of the inner peripheral wall portion 83 and the second direction end of the first wall portion 61 in the direction along the rotation axis 31Z is defined as the gap center. In this case, the center-to-center distance L is the distance between the center of the slit 76 in the direction along the rotation axis 31Z and the gap center.

In the following, the resonant frequency in the slit 76 when intake air flows from the storage space 72 to the annular space 77 through the slit 76 is referred to as the inlet branch resonant frequency FA. The resonant frequency in the annular space 77 when intake air flows through the annular space 77 in the second direction is referred to as the air column resonant frequency FB. Furthermore, the resonant frequency in the communication space 92 when intake air flows from the annular space 77 to the introduction passage 91 through the communication space 92 is referred to as the outlet branch resonant frequency FC.

The air column resonance frequency FB has the following relationship with the above parameters: The coefficient K below is determined by the sonic speed of the flowing intake air, etc.
Formula (1): Air column resonance frequency FB = coefficient K x (area S/center distance L x (1/volume VB + 1/volume VC) ^0.5 )
The inlet branch resonance frequency FA is related to the above parameters as follows:

Equation (2): Inlet branch resonance frequency FA = coefficient K × 1 / inlet length HA
The outlet branch resonance frequency F C is related to the above parameters as follows:
Equation (3): Exit branch resonance frequency FC = coefficient K × 1 / exit length HC
In this embodiment, the compressor housing 21 satisfies the following conditions (1) and (2) by adjusting various parameters based on the relationships of the above equations (1) to (3).

Condition (1): Air column resonance frequency FB < outlet branch resonance frequency FC
Condition (2): inlet branch resonance frequency FA/outlet branch resonance frequency FC>1.7
In this embodiment, the conditions (1) and (2) are realized by adjusting the parameters as follows. For example, when the air column resonance frequency FB = the outlet branch resonance frequency FC, the condition (1) can be realized by increasing the volume VB, increasing the volume VC, and increasing the center-to-center distance L to reduce the air column resonance frequency FB. Also, for example, when the inlet branch resonance frequency FA/outlet branch resonance frequency FC = 1.7, the condition (2) can be realized by decreasing the inlet length HA and increasing the inlet branch resonance frequency FA.

<Action of this embodiment>
When intake air is introduced into the introduction passage 91 from the intake passage 11 upstream of the compressor housing 21, the intake air flows into the accommodation space 72 via the introduction passage 91. Then, the intake air in the accommodation space 72 is compressed by the rotation of the compressor wheel 31. As a result, the compressed intake air flows into the intake passage 11 downstream of the compressor housing 21 via the connection passage 73 and the scroll passage 74.

When the pressure of the intake air in the accommodation space 72 becomes higher than the pressure of the intake air in the introduction passage 91, part of the intake air in the accommodation space 72 flows through the slit 76 into the annular space 77. The intake air in the annular space 77 then flows back into the introduction passage 91 through the communication space 92. This return of the intake air through the slit 76, the annular space 77, and the communication space 92 suppresses so-called surging, in which intake air flows back directly from the accommodation space 72 into the introduction passage 91.

<Effects of this embodiment>
The inventors have confirmed that when intake air is recirculated through the slit 76, the annular space 77, and the communication space 92, the resonance sound caused by the recirculation of the intake air becomes louder due to the relationship between the inlet branch resonance frequency FA, the air column resonance frequency FB, and the outlet branch resonance frequency FC. Hereinafter, the experimental data of this embodiment that satisfies both conditions (1) and (2) is referred to as present data DA, and the experimental data that does not satisfy at least one of conditions (1) and (2) is referred to as comparison data DB.

In the graph shown in FIG. 6, the area below the solid line is the area that satisfies condition (1). Therefore, the data DA in question satisfies condition (1). On the other hand, in the graph shown in FIG. 7, the area to the right of the dashed line is the area that satisfies condition (2). Therefore, the data DA in question satisfies condition (2).

As shown in FIG. 7, in the comparison data DB in which the inlet branch resonance frequency FA/outlet branch resonance frequency FC is 1.7 or less, the volume of the noise caused by resonance is high. Moreover, as shown in FIG. 6, even though two of the five comparison data DBs satisfy condition (1), the volume of the noise is high. In other words, from the perspective of reducing the volume of the noise, it is necessary to satisfy not only condition (1) but also condition (2). Therefore, in this embodiment, by satisfying conditions (1) and (2), the generation of excessively loud resonance can be suppressed.

<Example of change>
This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

- In the above embodiment, the example of adjusting parameters to achieve condition (1) is just one example and is not limited to the above example. For example, in addition to or instead of increasing the volume VB, the volume VC, and the center-to-center distance L, the air column resonance frequency FB may be reduced by reducing the area S. In other words, to achieve condition (1), the air column resonance frequency FB can be adjusted by adjusting the volume VB, the volume VC, the center-to-center distance L, and the area S.

-Also, for example, to achieve condition (1), it is not necessary to adjust the air column resonance frequency FB, and the outlet branch resonance frequency FC may be adjusted. In this case, the outlet branch resonance frequency FC can be increased by reducing the outlet length HC.

- In the above embodiment, the example of adjusting parameters to achieve condition (2) is just one example, and is not limited to the above example. For example, to achieve condition (2), it is not necessary to adjust the inlet branch resonance frequency FA, and the outlet branch resonance frequency FC may be adjusted. In this case, the outlet branch resonance frequency FC can be reduced by increasing the outlet length HC.

In the above embodiment, the configuration of the housing body 60 may be changed. For example, the number of intermediate walls 63 may be two or less, or four or more.
In the above embodiment, the configuration of the inlet member 80 may be changed. For example, the number of vanes 84 may be eight or less, or ten or more.

- In the above embodiment, the configuration of the compressor wheel 31 may be changed. For example, the number of flying blades 31B may be five or less, or seven or more.

FA...inlet branch resonance frequency FB...air column resonance frequency FC...outlet branch resonance frequency HA...inlet length HC...outlet length L...center distance S...area VB...volume VC...volume 10...internal combustion engine 11...intake passage 12...cylinder 13...exhaust passage 20...turbocharger 21...compressor housing 31...compressor wheel 31Z...rotation axis 60...housing body 61...first wall portion 62...second wall portion 63...middle wall portion 72...accommodation space 73...connection passage 74...scroll passage 76...slit 77...annular space 80...inlet member 91...introduction passage 92...communication space

Claims (1)

A compressor wheel that supercharges the intake air;
a housing body that accommodates the compressor wheel;
a cylindrical inlet member fixed to the housing body and defining a passage for intake air to be introduced into the compressor wheel,
The housing body includes:
a first wall portion extending annularly so as to surround a rotation axis of the compressor wheel when viewed from a direction along the rotation axis;
a second wall portion extending annularly so as to surround the first wall portion when viewed from a direction along the rotation axis;
an intermediate wall portion connecting the first wall portion and the second wall portion;
an accommodation space that is a space surrounded by the first wall portion and that accommodates the compressor wheel;
an annular space defined by the first wall portion, the second wall portion, and the intermediate wall portion;
a slit penetrating the first wall portion and dividing a portion of the intermediate wall portion in a direction along the rotation axis;
Equipped with
The inlet member is
an introduction passage adjacent to the accommodation space in a direction along the rotation axis, the introduction passage introducing intake air into the accommodation space;
a communication space surrounding the introduction passage and communicating the annular space with the introduction passage when viewed from a direction along the rotation axis;
Equipped with
When the resonance frequency in the annular space is defined as an air column resonance frequency, the resonance frequency in the slit is defined as an inlet branch resonance frequency, and the resonance frequency in the communication space is defined as an outlet branch resonance frequency,
A turbocharger, wherein the air column resonance frequency is lower than the outlet branch resonance frequency, and a value obtained by dividing the inlet branch resonance frequency by the outlet branch resonance frequency is greater than 1.7.