Crankcase ventilation system and vehicle

Abstract

The crankcase ventilation system comprises an air filter, a crankcase, an oil-gas separator, a first pressure sensor, a motor and a controller, the crankcase is connected with the air filter through an air inlet manifold, the input end of the oil-gas separator is connected with the crankcase, the output end of the oil-gas separator is connected with the air inlet manifold, and the first pressure sensor is connected with the motor. The first pressure sensor is arranged in the crankcase and used for detecting pressure in the crankcase, the motor is connected to the oil-gas separator and used for driving the oil-gas separator to rotate so as to suck engine oil and gas mixed in the crankcase into the oil-gas separator to be separated, and the controller is connected with the first pressure sensor and the motor. The control module is used for controlling the rotating speed of the motor based on a detection result of the first pressure sensor to enable the pressure in the crankcase to be within a preset negative pressure range. The oil-gas separation efficiency is improved, the requirement that the pressure in the crankcase is always kept negative under the whole universal characteristic is met, and the economical efficiency of an engine is improved.

Description

Technical Field

[0001] The present application relates to the field of vehicle technology, and in particular to a crankcase ventilation system and a vehicle. Background Art

[0002] When the engine is running, the high-pressure combustible mixture and burned gas in the combustion chamber will more or less leak into the crankcase through the gap between the piston group and the cylinder, causing blowby.

[0003] The existing crankcase ventilation system generally uses the negative pressure in the intake manifold or before the supercharger as the power source of the crankcase ventilation system. However, under the universal characteristic working conditions, the negative pressure in the intake manifold or before the supercharger is small in some working conditions, resulting in poor oil-gas separator effect and reduced oil-gas separation efficiency. In addition, for the whole vehicle cycle working conditions, it is required that the pressure in the crankcase is always kept negative under the entire universal characteristic, and the current conventional crankcase ventilation system is difficult to meet this requirement. Summary of the invention

[0004] In order to overcome the problems existing in the above-mentioned prior art, the main purpose of the present application is to provide a crankcase ventilation system and a vehicle that can improve the oil-gas separation efficiency.

[0005] In order to achieve the above objectives, this application specifically adopts the following technical solutions: A crankcase ventilation system comprising: Air filter; A crankcase, wherein the crankcase is connected to the air filter through an intake manifold; An oil-gas separator, wherein an input end of the oil-gas separator is connected to the crankcase, and an output end of the oil-gas separator is connected to the intake manifold; a first pressure sensor, the first pressure sensor being disposed in the crankcase and used for detecting the pressure in the crankcase; a motor, the motor being connected to the oil-gas separator and being used to drive the oil-gas separator to rotate so as to suck the oil and gas mixed in the crankcase into the oil-gas separator for separation; A controller is connected to the first pressure sensor and the motor respectively, and is used to control the rotation speed of the motor based on the detection result of the first pressure sensor so that the pressure in the crankcase is within a preset negative pressure range.

[0006] In some embodiments, the crankcase ventilation system further includes a supercharger, a second pressure sensor and a third pressure sensor, the inlet end of the supercharger is connected to the air filter through an intake pipe, the outlet end of the supercharger is connected to the intake manifold, the second pressure sensor is arranged at the intake manifold, and is used to detect the pressure in the intake manifold, the third pressure sensor is arranged at the inlet end of the supercharger, and is used to detect the pressure at the inlet end of the supercharger, and the controller is respectively connected to the second pressure sensor and the third pressure sensor, and is used to control the start of the motor based on the detection results of the first pressure sensor, the second pressure sensor and the third pressure sensor. In some embodiments, the crankcase ventilation system also includes an ambient pressure sensor, which is used to detect the pressure of the external atmosphere. The controller is connected to the ambient pressure sensor and is used to control the motor to turn on or off based on the detection results of the first pressure sensor and the ambient pressure sensor.

[0007] In some embodiments, the crankcase ventilation system also includes a cylinder head, an oil pan and a front cover, the cylinder head is arranged above the crankcase, the oil pan is arranged below the crankcase, the front cover is respectively connected to the cylinder head, the crankcase and the oil pan, the oil-gas separator is integrated in the front cover, and the crankcase is connected to the intake manifold through the cylinder head.

[0008] In some embodiments, the crankcase ventilation system further includes an oil pipe and an umbrella valve, one end of the oil pipe is connected to the oil-gas separator, the other end of the oil pipe is connected to the oil pan, and the umbrella valve is connected to the oil pipe.

[0009] In some embodiments, the crankcase ventilation system also includes an air supply pipe and a first one-way valve, one end of the air supply pipe is connected to the output end of the air filter, the other end of the air supply pipe is connected to the crankcase, and the first one-way valve is arranged on the air supply pipe.

[0010] In some embodiments, the crankcase ventilation system also includes an air pipe, a first branch pipe and a second one-way valve, one end of the air pipe is connected to the oil-gas separator, the other end of the air pipe is connected to the intake manifold through the first branch pipe, and the second one-way valve is arranged on the first branch pipe.

[0011] In some embodiments, the crankcase ventilation system further includes a second branch pipe and a third one-way valve, one end of the second branch pipe is connected to the air pipe, the other end of the second branch pipe is connected to the intake pipe, and the third one-way valve is arranged on the second branch pipe.

[0012] In some embodiments, the crankcase ventilation system further includes an intercooler, which is disposed at an outlet end of the supercharger and is used to reduce the temperature of the gas flowing out of the outlet end of the supercharger.

[0013] A vehicle comprises a vehicle body, a plurality of wheels and a crankcase ventilation system as described in any one of the above items, wherein the plurality of wheels are respectively connected to the vehicle body, and the crankcase ventilation system is arranged on the vehicle body.

[0014] Compared with the prior art, the crankcase ventilation system provided by the present application has at least the following beneficial effects: The present application is provided with a motor, which is connected to an oil-gas separator and is used to drive the oil-gas separator to rotate. The power of the motor rotation forces the mixed oil and gas in the crankcase to flow into the oil-gas separator for separation, thereby providing sufficient power for the crankcase ventilation system, improving the oil-gas separation efficiency, and reducing oil consumption. The controller is respectively connected to the first pressure sensor and the motor, and is used to control the speed of the motor based on the detection result of the first pressure sensor, so that the pressure in the crankcase is within a preset negative pressure range, satisfying the requirement that the pressure in the crankcase is always kept at negative pressure under the entire universal characteristics, thereby improving the economy of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of a crankcase ventilation system provided in an embodiment of the present application.

[0016] Reference numerals: 1. Cylinder head; 2. Crankcase; 3. Oil pan; 4. Front cover; 5. Air filter; 6. Intake pipe; 7. Supercharger; 8. Intake manifold; 9. Oil-gas separator; 10. Motor; 11. Oil pipe; 12. Umbrella valve; 13. First three-way valve; 14. Air supply pipe; 15. First non-return valve; 16. Air pipe; 17. Second three-way valve; 18. First branch pipe; 19. Second non-return valve; 20. Third three-way valve; 21. Second branch pipe; 22. Third non-return valve; 23. Intercooler. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0018] In the description of this application, unless otherwise clearly specified and limited, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance; unless otherwise specified or explained, the term "multiple" refers to two or more, and the term "multiple" refers to two or more; the terms "connected", "fixed", etc. should be understood in a broad sense, for example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0019] In the description of this specification, it should be understood that the directional words such as "upper" and "lower" described in the embodiments of the present application are described at the angles shown in the accompanying drawings and should not be understood as limiting the embodiments of the present application. In addition, in the context, it should also be understood that when it is mentioned that an element is connected to another element "upper" or "lower", it can not only be directly connected to another element "upper" or "lower", but also indirectly connected to another element "upper" or "lower" through an intermediate element.

[0020] Reference Figure 1 As shown, Figure 1The schematic diagram of the crankcase ventilation system provided in the embodiment of the present application. The present embodiment discloses a crankcase ventilation system, which includes a cylinder head 1, a crankcase 2, an oil pan 3, a front cover 4, an air filter 5, an intake pipe 6, a supercharger 7, an intake manifold 8, an oil-gas separator 9, a first pressure sensor (not shown in the figure), a motor 10 and a controller. The cylinder head 1 is arranged above the crankcase 2. The oil pan 3 is arranged below the crankcase 2, and the front cover 4 is connected to the cylinder head 1, the crankcase 2 and the oil pan 3 respectively. The air filter 5 is connected to the outside atmosphere. The inlet end of the supercharger 7 is connected to the air filter 5 through the intake pipe 6, and the outlet end of the supercharger 7 is connected to the cylinder head 1 through the intake manifold 8. The intake manifold 8 is connected to the combustion chamber, and the combustion chamber is connected to the crankcase 2. The input end of the oil-gas separator 9 is connected to the crankcase 2, and the output end of the oil-gas separator 9 is connected to the intake manifold 8. The first pressure sensor is arranged in the crankcase 2, and is used to detect the pressure in the crankcase 2. The motor 10 is connected to the oil-gas separator 9, and is used to drive the oil-gas separator 9 to rotate, so as to suck the mixed oil and gas in the crankcase 2 into the oil-gas separator 9 for separation. The motor 10 is controlled by PWM, i.e., pulse width modulation, and is not affected by the vacuum degree of the intake manifold 8 and the inlet end of the supercharger 7. The controller is connected to the first pressure sensor and the motor 10 respectively, and is used to control the speed of the motor 10 based on the detection result of the first pressure sensor, so that the pressure in the crankcase 2 is within the preset negative pressure range, so as to reduce the situation that the oil seal fails when the pressure in the crankcase 2 is less than the minimum value of the preset range, the environmental impurities enter the crankcase 2, and the kinematic pair wears, and also reduces the situation that the exhaust gas enters the atmosphere and pollutes the environment when the pressure in the crankcase 2 is greater than the maximum value of the preset range, so as to ensure the normal operation of the crankcase ventilation system. By maintaining the crankcase ventilation system at a negative pressure at all operating conditions, the gas in the crankcase 2 can be pumped out, reducing the leakage of oil from the oil seal and gasket due to excessive pressure, thereby ensuring the sealing of the engine. The negative pressure helps to more thoroughly extract the combustion exhaust gas and oil vapor that have entered the crankcase 2, and then send them into the intake system for recirculation and combustion, reducing the emission of pollutants and the possibility of them condensing into sludge in the crankcase 2, thereby ensuring the cleanliness of the crankcase 2 and facilitating the normal operation of the engine.

[0021] In this embodiment, the oil-gas separator 9 is a centrifugal separator, which has high separation efficiency and does not require heating and pressurization, thereby reducing energy consumption and improving the working efficiency of the crankcase ventilation system.

[0022] In this embodiment, the oil-gas separator 9 includes a housing and a separation assembly, and the separation assembly is coaxially connected to the motor 10, so that the motor 10 drives the separation structure to rotate, thereby sucking out the exhaust gas in the crankcase 2 through centrifugal force. The housing is integrated with the front cover 4 to reduce the number of connecting parts, simplify the overall structure, and reduce the cost.

[0023] The present embodiment is provided with a motor 10, which is connected to the oil-gas separator 9 and is used to drive the oil-gas separator 9 to rotate. The power generated by the rotation of the motor 10 forces the mixed oil and gas in the crankcase 2 to flow into the oil-gas separator 9 for separation, thereby providing sufficient power for the crankcase ventilation system, improving the oil-gas separation efficiency, and reducing oil consumption. The controller is respectively connected to the first pressure sensor and the motor 10, and is used to control the rotation speed of the motor 10 based on the detection result of the first pressure sensor, so that the pressure in the crankcase 2 is within a preset negative pressure range, satisfying the requirement that the pressure in the crankcase 2 is always kept at negative pressure under the entire universal characteristic, thereby improving the economy of the engine.

[0024] Continue to refer to Figure 1 As shown, the crankcase ventilation system also includes an oil pipe 11 and an umbrella valve 12. One end of the oil pipe 11 is connected to the oil-gas separator 9, and the other end of the oil pipe 11 is connected to the oil pan 3, so that the oil separated by the oil-gas separator 9 can flow back to the oil pan 3, thereby maintaining the normal circulation of the oil. The umbrella valve 12 is connected to the oil pipe 11. When the oil separated by the oil-gas separator 9 is accumulated at a certain height above the umbrella valve 12, the umbrella valve 12 opens under the pressure of the oil to return the oil to the oil pan 3, and then the umbrella valve 12 is closed to reduce the situation where the fluid in the oil pan 3 flows back to the oil-gas separator 9, thereby ensuring the normal operation of the oil-gas separator 9.

[0025] The crankcase ventilation system also includes a second pressure sensor, a third pressure sensor and an ambient pressure sensor. The second pressure sensor is arranged at the intake manifold 8 to detect the pressure in the intake manifold 8. The third pressure sensor is arranged at the inlet end of the supercharger 7 to detect the pressure at the inlet end of the supercharger 7. The ambient pressure sensor is used to detect the pressure of the outside atmosphere, that is, the atmospheric pressure. The controller is respectively connected to the second pressure sensor, the third pressure sensor and the ambient pressure sensor, and is used to control the motor 10 to start based on the detection results of the first pressure sensor, the second pressure sensor and the third pressure sensor, or to control the motor 10 to start or stop based on the detection results of the first pressure sensor and the ambient pressure sensor, so as to ensure that the pressure in the crankcase 2 is at a negative pressure, thereby ensuring the oil-gas separation efficiency, and the motor 10 is selectively started as needed, which reduces maintenance costs and saves energy.

[0026] During operation, when ab≤x and ac≤x or da≤x, the controller controls the motor 10 to turn on, and when ad≤y, the controller controls the motor 10 to turn off, wherein a is the pressure value of the first pressure sensor, that is, the pressure value in the crankcase 2; b is the pressure value of the second pressure sensor, that is, the pressure value of the intake manifold 8; c is the pressure value of the third pressure sensor, that is, the pressure value at the inlet end of the supercharger 7; d is the pressure value of the ambient pressure sensor, that is, the atmospheric pressure; x is the preset first pressure value; y is the preset second pressure value; the preset first pressure value x and the preset second pressure value y are safety values, which can be 1kpa, 0.5kpa, etc., and the specific numerical values ​​can be set according to needs.

[0027] Reference Figure 1 As shown, the crankcase ventilation system also includes a first three-way valve 13, an air supply pipe 14 and a first one-way valve 15. The first three-way valve 13 is connected to the air filter 5 and the intake pipe 6 respectively. One end of the air supply pipe 14 is connected to the first three-way valve 13, and the other end of the air supply pipe 14 is connected to the crankcase 2. Fresh air is introduced into the crankcase 2 from behind the air filter 5 through the air supply pipe 14, which reduces the temperature rise in the crankcase 2 due to the operation of the engine, reduces the temperature in the crankcase 2, ensures the heat dissipation of the crankcase 2, and the fresh air can make the gas in the crankcase 2 circulate better, reduces the accumulation of oil and gas in the crankcase 2, and produces harmful deposits such as sludge, slows down the aging speed of the engine oil, and saves costs. The first one-way valve 15 is arranged on the air supply pipe 14, and the input end of the first one-way valve 15 is connected to the air filter 5, and the output end of the first one-way valve 15 is connected to the crankcase 2. When the pressure at the input end of the first one-way valve 15 is greater than the pressure at the output end, the first one-way valve 15 is in an open state. When the pressure at the output end of the first one-way valve 15 is greater than the pressure at the input end, the first one-way valve 15 is in a closed state, so as to reduce the backflow of fluid in the crankcase 2 from the air supply pipe 14, so that the crankcase ventilation system can operate safely.

[0028] Reference Figure 1 As shown, the crankcase ventilation system also includes an air pipe 16, a second three-way valve 17, a first branch pipe 18, a second non-return valve 19, a third three-way valve 20, a second branch pipe 21 and a third non-return valve 22. One end of the air pipe 16 is connected to the oil-gas separator 9, and the other end of the air pipe 16 is connected to the first branch pipe 18 through the second three-way valve 17. The gas separated by the oil-gas separator 9 flows out through the air pipe 16. The first branch pipe 18 is connected to the intake manifold 8 through the third three-way valve 20. The second non-return valve 19 is arranged on the first branch pipe 18. One end of the second branch pipe 21 is connected to the second three-way valve 17, and the other end of the second branch pipe 21 is connected to the intake pipe 6. The third non-return valve 22 is arranged on the second branch pipe 21.

[0029] During operation, when the vehicle is started, the vehicle is in a low-speed and low-load condition, the supercharger 7 does not intervene in the work, the intake manifold 8 is a negative pressure source, the pressure in the crankcase 2 is greater than the pressure in the intake manifold 8, the second one-way valve 19 is opened, and the gas separated by the oil-gas separator 9 flows into the intake manifold 8 from the first branch pipe 18 through the air pipe 16, and then enters the combustion chamber for combustion; when the vehicle engine is in a high-speed and high-load condition, the supercharger 7 intervenes in the work, the pressure at the inlet end of the supercharger 7 is less than the pressure in the intake manifold 8, the third one-way valve 22 is opened, and the intake manifold 8 is in a negative pressure state. The pressure in the pipe 8 is greater than the pressure in the crankcase 2, the second one-way valve 19 is closed, and the gas separated by the oil-gas separator 9 flows into the intake pipe 6 from the second branch pipe 21 through the air pipe 16, flows into the intake manifold 8 after being pressurized by the supercharger 7, and then enters the combustion chamber for combustion; wherein, in the process of the vehicle engine being upgraded from a low-speed and low-load operating condition to a high-speed and high-load operating condition, the pressure in the crankcase 2 will be greater than the pressure of the intake manifold 8 and the pressure at the inlet end of the supercharger 7 at a certain moment, and at this time, the second one-way valve 19 and the third one-way valve 22 are both opened.

[0030] Reference Figure 1 As shown, the crankcase ventilation system also includes an intercooler 23, which is arranged at the outlet end of the supercharger 7 and is connected to the third three-way valve 20. The intercooler 23 is used to reduce the temperature of the gas flowing out of the outlet end of the supercharger 7 after supercharging, thereby reducing the heat load of the engine, increasing the intake volume, and increasing the power of the engine.

[0031] Based on this embodiment, a vehicle is also disclosed. The vehicle includes a body, a plurality of wheels and a crankcase ventilation system according to any one of the above embodiments. The plurality of wheels are respectively connected to the body, and the crankcase ventilation system is arranged on the body.

[0032] In a specific application scenario, when the vehicle engine is in a low-speed and low-load condition, the supercharger 7 does not intervene in the work, and the air entering from the air filter 5 enters the combustion chamber from the intake pipe 6 through the intake manifold 8 for combustion. The high-pressure combustible mixture and the burned gas in the combustion chamber will leak into the crankcase 2 through the gap between the piston group and the cylinder. The exhaust gas and the engine oil in the crankcase 2 are separated by the oil-gas separator 9, and the engine oil returns to the oil pan 3 through the oil pipe 11. The gas returns to the intake manifold 8 from the first branch pipe 18 through the air pipe 16, and then enters the combustion chamber. The exhaust gas in the crankcase 2 is burned in the combustion chamber, and then it is processed by the turbocharger 7 and the three-way catalytic converter from the exhaust passage, and then it enters the atmosphere from the exhaust pipe; when the vehicle engine is in a high-speed and high-load condition, the turbocharger 7 intervenes, and the exhaust gas and the engine oil in the crankcase 2 are separated by the oil-gas separator 9, and then the gas flows from the second branch pipe 21 to the intake pipe 6 through the air pipe 16, and then after being pressurized by the turbocharger 7, the temperature is reduced by the intercooler 23, and then it enters the combustion chamber through the intake manifold 8 for combustion, and then it passes through the turbocharger 7 and the three-way catalytic converter from the exhaust passage, and then it enters the atmosphere from the exhaust pipe. Among them, when the pressure in the crankcase 2 minus the pressure of the intake manifold 8 is less than or equal to the preset first pressure value and the pressure in the crankcase 2 minus the pressure at the inlet end of the turbocharger 7 is less than or equal to the preset first pressure value, or the atmospheric pressure minus the pressure in the crankcase 2 is less than or equal to the preset first pressure value, the controller controls the motor 10 to turn on; when the pressure in the crankcase 2 minus the atmospheric pressure is less than or equal to the preset second pressure value, the controller controls the motor 10 to turn off.

[0033] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A crankcase ventilation system, characterized in that: include: Air filter; a crankcase, wherein the crankcase is connected to the air filter through an intake manifold; An oil-gas separator, wherein an input end of the oil-gas separator is connected to the crankcase, and an output end of the oil-gas separator is connected to the intake manifold; a first pressure sensor, the first pressure sensor being disposed in the crankcase and used for detecting the pressure in the crankcase; a motor, the motor being connected to the oil-gas separator and being used to drive the oil-gas separator to rotate so as to suck the oil and gas mixed in the crankcase into the oil-gas separator for separation; A controller is connected to the first pressure sensor and the motor respectively, and is used to control the rotation speed of the motor based on the detection result of the first pressure sensor so that the pressure in the crankcase is within a preset negative pressure range.

2. The crankcase ventilation system according to claim 1, characterized in that The crankcase ventilation system also includes a supercharger, a second pressure sensor and a third pressure sensor. The inlet end of the supercharger is connected to the air filter through an intake pipe, and the outlet end of the supercharger is connected to the intake manifold. The second pressure sensor is arranged at the intake manifold to detect the pressure in the intake manifold. The third pressure sensor is arranged at the inlet end of the supercharger to detect the pressure at the inlet end of the supercharger. The controller is connected to the second pressure sensor and the third pressure sensor respectively, and is used to control the start of the motor based on the detection results of the first pressure sensor, the second pressure sensor and the third pressure sensor.

3. The crankcase ventilation system according to claim 1, characterized in that: The crankcase ventilation system also includes an ambient pressure sensor, which is used to detect the pressure of the external atmosphere. The controller is connected to the ambient pressure sensor and is used to control the motor to be turned on or off based on the detection results of the first pressure sensor and the ambient pressure sensor.

4. The crankcase ventilation system according to claim 1, characterized in that The crankcase ventilation system also includes a cylinder head, an oil pan and a front cover, the cylinder head is arranged above the crankcase, the oil pan is arranged below the crankcase, the front cover is connected to the cylinder head, the crankcase and the oil pan respectively, the oil-gas separator is integrated in the front cover, and the crankcase is connected to the intake manifold through the cylinder head.

5. The crankcase ventilation system according to claim 4, characterized in that The crankcase ventilation system further comprises an oil pipe and an umbrella valve, one end of the oil pipe is connected to the oil-gas separator, the other end of the oil pipe is connected to the oil pan, and the umbrella valve is connected to the oil pipe.

6. The crankcase ventilation system according to claim 1, characterized in that The crankcase ventilation system also includes an air supply pipe and a first one-way valve, one end of the air supply pipe is connected to the output end of the air filter, the other end of the air supply pipe is connected to the crankcase, and the first one-way valve is arranged on the air supply pipe.

7. The crankcase ventilation system according to claim 2, characterized in that The crankcase ventilation system also includes an air pipe, a first branch pipe and a second one-way valve, one end of the air pipe is connected to the oil-gas separator, the other end of the air pipe is connected to the intake manifold through the first branch pipe, and the second one-way valve is arranged on the first branch pipe.

8. The crankcase ventilation system according to claim 7, characterized in that The crankcase ventilation system also includes a second branch pipe and a third one-way valve, one end of the second branch pipe is connected to the air pipe, the other end of the second branch pipe is connected to the intake pipe, and the third one-way valve is arranged on the second branch pipe.

9. The crankcase ventilation system according to any one of claims 2 to 8, characterized in that: The crankcase ventilation system further includes an intercooler, which is disposed at the outlet end of the supercharger and is used to reduce the temperature of the gas flowing out from the outlet end of the supercharger.

10. A vehicle, characterized in that: It comprises a vehicle body, a plurality of wheels and a crankcase ventilation system as claimed in any one of claims 1 to 9, wherein the plurality of wheels are respectively connected to the vehicle body, and the crankcase ventilation system is arranged on the vehicle body.

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