JPH0426660Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an internal combustion engine equipped with a Roots pump type supercharger, and more particularly to lubrication of a bearing supporting the rotor shaft of a Roots pump.

[Conventional technology]

The Roots pump, which constitutes a mechanical supercharger for an internal combustion engine, has bilobed rotors attached to two rotor shafts, and performs pumping action by rotating these rotors in synchronization in opposite directions. It's becoming like that. A small amount of clearance is usually provided between the rotors and between the rotors and the housing. Therefore, it is inevitable that the discharged air on the high pressure side leaks to the low pressure side through these clearances. the result,
The pressure of air leaking from the rotor side acts on the bearings that support both ends of the rotor shaft, creating pressure on both sides of the bearings. As a result, the ability to retain the grease that lubricates the bearing is reduced. In order to improve the deterioration in grease retention performance caused by such a pressure difference, Japanese Utility Model Application Publication No. 59-54785 describes a device that provides a notch to connect the clearance space and the air on the suction side of the pump. . It has also been proposed to provide a labyrinth section between the rotor and the bearing, and to communicate the space between the bearing and the labyrinth with the atmosphere to reduce the intake pressure applied to the bearing.

[Problem that the invention attempts to solve]

In Roots pumps for internal combustion engines with a supercharger, the clearance between the labyrinth and the shaft mentioned above needs to be large enough to avoid contact. It is also necessary to take a large amount. However, when this is done, in engine operating ranges where the amount of intake air is small, such as idling or decelerating, the atmospheric air is drawn into the engine through the labyrinth, which substantially increases the amount of intake air, causing the throttle to There is a problem in that the engine speed cannot be lowered sufficiently even if the valve is throttled. As a result, undesirable problems such as an excessively high idle speed, poor engine braking effectiveness during deceleration, and deterioration of fuel efficiency have arisen. Therefore, the purpose of this invention is to sufficiently reduce the intake pressure applied to the bearing by bleeding it to the atmosphere, and to prevent the engine rotation from increasing in areas where the amount of intake air is small, such as during light load and low rotation operation. do.

In particular, the present invention focuses on the fact that the supercharger (Roots pump) can be stopped in operation at light loads and low rotations as mentioned above, and its greatest feature is to control the bleed timing in accordance with the operation of the Roots pump. It is something to do.

[Means for solving problems]

In order to achieve the above object, according to the present invention,
The two rotors, which are rotatably supported by bearings in the pump housing, rotate while meshing with each other while maintaining a predetermined clearance between them and the inner peripheral surface of the housing, discharging a fixed volume of fluid from the suction side with each rotation. A Roots pump supercharger is installed downstream of the throttle valve, and the Roots pump stops operating when the load is light and at low rotation speeds. Further, an annular space formed between the end face of the rotor and the seal portion of the bearing is connected to the atmosphere via an atmosphere introduction passage, and a control valve that opens only when the Roots pump is operated is connected to the atmosphere introduction. It is provided in the passage so that the pressure acting on the seal portion can be bled to the atmosphere when the Roots pump is in operation, and the pressure acting on the seal portion can be prevented from bleeding into the atmosphere when the Roots pump is not in operation.

〔Example〕

FIG. 1 is a schematic diagram showing the entirety of an internal combustion engine equipped with a Roots pump according to the present invention.

In FIG. 1, 1 is an air cleaner, 2 is an air flow meter, 3 is a throttle valve, 4 is a supercharger consisting of a Roots pump, 5 is an intake pipe, 6 is an engine body,
9 is a control valve, and 13 is a computer. The control valve 9 includes a passage 7 that communicates with the space between the labyrinth of the supercharger 4 and the bearing, and a passage 8 that communicates upstream of the throttle valve 3 and has a pressure close to atmospheric pressure, as will be described later.
The opening and closing between the two terminals is controlled by a signal from the computer 13. Computer 13 is various sensors 1
4. The operation of the Roots pump 4 is detected using, for example, an intake air amount Q signal from an engine speed N sensor, a throttle opening sensor, an air flow meter, etc., and the control valve 9 is controlled based on the detected signal. The control valve 9 can be configured as a well-known electromagnetic valve including a valve body 10, a spring 11, and an electromagnetic coil 12.

FIG. 2 is a sectional view of the supercharger 4 consisting of a Roots pump. In FIG. 2, 50 is a housing body, 51 is a rear plate that closes one open end of the housing body, and the housing body 50 and the rear plate 51 form a pump housing. Inside this pump housing, there are two rotors 2 that have a bilobed shape unique to Roots pumps.
1 and 40 are the respective rotor shafts 22 and 23
is supported and placed. 24 is a pin for fixing the rotor 21 to the rotor shaft 22.
A rotor shaft 22 supporting the rotor 21 on the upper side of FIG. 2 is rotatably supported at both ends by bearings 28 and 37, and at the same time, a pulley 43 is fixed via a well-known electromagnetic clutch 60.
Another lower rotor 40 is similarly fixed to the rotor shaft 23, and this rotor shaft 23 is also rotatably supported by bearings at both ends.
Each rotor shaft 22, 23 is gear 2
Rotation is transmitted at 9 and 30.

That is, each rotor shaft 22, 23 is supported by bearings on both sides of the rotor. Each of the rotor shafts 22, 23 extends further to the right than the bearing on the right side as viewed in FIG. 2, and similar gears 29, 30 are respectively attached to the extended ends thereof.
In the illustrated structure, the inner rings of the bearings engage with the stepped portions of the respective rotor shafts, the inner peripheries of the gears 29 and 30 engage with these inner rings, and the inner rings of the bearings engage with the stepped portions of the respective rotor shafts.
0 is fastened to each rotor shaft 22, 23 with a washer 32, a screw 44, or the like. gear 29,
30 and the bearing, covering the tip of the rotor shaft,
A cover 33 is attached to the rear plate 51,
Forms an oil chamber. A suitable amount of oil is sealed in the oil chamber to lubricate the gears 29, 30 and bearings. The rotation of the engine crankshaft is transmitted to the pulley 43 by a belt (not shown), and the rotation of the rotor 2 is transmitted only when the electromagnetic clutch 60 is turned on.
1 and 40 to supercharge the intake air to the engine.

Next, the structure of the bearing portion that rotatably supports the rotor shafts 22, 23 will be described in detail using the bearing 28 on the right side of FIG. 2 as an example. The bearing 28 is an oil-lubricated type bearing, and an oil seal 27 is provided on the rotor 21 side to prevent oil from leaking out. End face of rotor 21 and rear plate 5
1, there is a gap in the axial direction, forming a so-called labyrinth portion 46. A port 48 is connected to the annular space 47 between the labyrinth portion 46 and the bearing oil seal 27, and this port 48 is further connected to the control valve 9 via the passage 7. , communicates with the atmosphere upstream of the throttle valve 3 (FIG. 1) via a passage 8.

The signal that turns on the electromagnetic clutch 60 of the housing 50 is directly used to turn on the solenoid valve 9 (step 30).
7) If used as a signal, Roots Pump 4
The solenoid valve 9 can be turned ON and OFF according to the ON and OFF conditions. Intake pressure acts on the bearing oil seal 27 internally, that is, through the rotor chamber and the labyrinth 46, but during normal operation, the control valve 9
is in an energized state, and the force of the electromagnetic coil 12 overcomes the spring 11 and attracts the valve body 10, causing the passage 7
Since the passage 8 and the passage 8 communicate with each other, the atmospheric pressure upstream of the throttle valve 3 (FIG. 1) is introduced into the annular space 47 and bled, so that the pressure becomes sufficiently small.

Generally speaking, the operating range of the Roots pump, that is, the range in which supercharging is performed, is as shown in Figure 4, when the engine speed N is above a predetermined value N ₀ (for example, N ₀ ≒ 3500 rpm) or when the load (intake air amount Q /rotational speed N) is equal to or greater than a predetermined value A ₀ (for example, A ₀ ≈0.6).
In other words, as shown in FIG. 3, when Q/N≧A ₀ (step 301) or N≧N ₀ (step 303), the electromagnetic clutch 60 is turned on (step 305), and the rotation of the crankshaft is controlled by the roots pump 4.
is transmitted to the rotor shaft. Therefore, in other words, only when the engine speed N is below a certain set value N ₀ and the load is below a predetermined value A ₀ (light load and low rotation), in step 309, the energization to the solenoid valve 9 is cut off and turned OFF. Make it. As a result, the valve body 10 of the control valve (electromagnetic valve) 9 blocks off the passages 7 and 8 by the force of the spring 11. That is, the valve is closed. As a result, intake pressure acts on the bearing oil seal, but since the rotation speed is low, there is no adverse effect on the characteristics of the oil seal. This prevents the amount from increasing, and therefore prevents the engine speed from increasing.

The same applies to the other bearings of the rotor shafts 22 and 23, and the annular space between the labyrinth part and the bearing oil seal part is connected to the housing body 50 and the rear plate 51.
It is connected to the passageway 7 through a port 48 formed inside. As a result, as described above, the annular space is bled with the atmosphere during normal operation (high load or high rotation) when the Roots pump is in operation. In addition, in FIG. 2, the reference numeral 36 indicates the port 48.
It is a seal that closes the end of the

[Effect of idea]

As described above, according to the present invention, by controlling the bleed in accordance with the operation of the Roots pump, the intake pressure acting on the bearing is bleed to the atmosphere during high load or high rotation when the Roots pump is operating, and the bearing is The oil seal sufficiently maintains its function of retaining the grease that lubricates the bearing by reducing the pressure difference that acts thereon. Also, during light loads and low rotations when the Roots pump is stopped,
Since the influence of the intake pressure acting on the bearing is small, the bleed is actively cut to prevent an increase in intake air volume and engine speed (especially noticeable during idling and deceleration), and to improve the engine braking effect. It is possible to improve fuel efficiency while reducing fuel consumption.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a supercharged internal combustion engine equipped with a Roots pump according to the present invention, Fig. 2 is a sectional view of a supercharger comprising a Roots pump, and Fig. 3 is a diagram of a bleed control valve according to the present invention. FIG. 4 is a flowchart diagram showing one mode of control, and FIG. 4 is a diagram explaining the operating range of the Roots pump. 4...supercharger (roots pump), 7, 8... passage, 9... control valve, 13... computer, 2
1, 40... Rotor, 22, 23... Rotor shaft, 27... Oil seal, 28... Bearing, 4
7...Annular space, 48...Port, 50...Housing, 51...Rear plate.

Claims (1)

[Scope of utility model registration request] The two rotors 21 and 40, which are rotatably supported by bearings in the pump housing 50, rotate while meshing with each other while maintaining a predetermined clearance between them and the inner peripheral surface of the housing, discharging a fixed volume of fluid with each rotation. A Roots pump type supercharger 4 that sucks and discharges air from the suction side to the discharge side is provided downstream of the throttle valve 3, and the Roots pump 4 stops operating when the load is light and the rotation speed is low.
In an internal combustion engine that operates under high load or high rotation, around the rotor shafts 22, 23 and
The annular space 47 formed between the end surfaces of the rotors 21, 40 and the seal portion 27 of the bearing 28 is connected to the atmosphere via the atmosphere introduction passages 7, 8, 48, and only when the roots pump is operated. A control valve 9 that opens is provided in the atmosphere introduction passage to bleed the pressure acting on the seal portion to the atmosphere when the Roots pump is in operation, and to prevent the pressure acting on the seal portion from bleeding into the atmosphere when the Roots pump is not in operation. An internal combustion engine equipped with a Roots pump supercharger, which is characterized by being able to perform