JPS63100224A - Engine with supercharger - Google Patents

Abstract

PURPOSE:To improve durability of bearings and a control valve by connecting annular spaces defined in a casing of a mechanical supercharger around support shafts of rotors thereof to atmosphere introducing passages and connecting to the passage a control valve adapted to be closed when the engine speed becomes lower than a fuel cutting speed. CONSTITUTION:A mechanical supercharger 20 such as a Roots pump provided in an intake passage 12 downstream of a throttle valve 18 includes in a casing 24 rotors 22 the support shafts 36 of which are supported through holes formed through end walls 24a of the casing 24 by bearings 28. In this case, there are defined between the end surfaces of the rotors 22 and the bearings 28 annular spaces 36 encircling the support shafts 26, and the annular spaces 36 are open to the atmosphere through atmosphere introducing passages (port 38 and pipe 40). The atmosphere introducing passages are connected to a control valve 42, which is controlled by a control unit 52 to be closed when the engine speed becomes lower than a fuel cutting speed during speed reducing drive. This avoids unnecessary on-off operation of the control valve 42, assuring improved durability.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an engine equipped with a mechanical supercharger.

[Conventional technology]

JP-A-61-16232 discloses an engine equipped with a mechanical supercharger. A portion of the boost pressure leaks from the end face of the rotor and is applied to the bearing, reducing the bearing's ability to retain lubricant. This publication discloses that in order to ensure the lubricant holding capacity of the supercharger bearing, the supercharging pressure applied to the bearing is bled to the atmosphere, and when idling, negative pressure acts together with the throttle valve throttle. Since air is additionally sucked in from this bleed passage and the engine speed increases, a control valve is provided to prevent this from occurring.

[Problem that the invention seeks to solve]

As described above, in order to ensure the lubricant retention capacity of the supercharger bearing, the supercharging pressure applied to the bearing is bled to the atmosphere,
If the bleed air was cut off during idle, a problem arose in that drivability during deceleration deteriorated. During deceleration, fuel cap is performed at a speed higher than the fuel cut speed, and when the fuel cut speed is reached, fuel is returned and supplied, but if bleed air is being conducted at the time of fuel return, the amount of intake air is reduced. Since a large amount of fuel is suddenly supplied, a torque shock is felt, and the idle speed increases more than expected.

In Japanese Patent Application No. Sho 61-26877, which is the prior application of this application, in order to improve such torque shock during deceleration,
During fuel cut during deceleration, the control valve that controls the bleed air introduced into the supercharger bearing is kept open, and during non-fuel cut, the control valve is closed when the rotation speed is below a predetermined number. There is. This predetermined rotation speed is higher than the fuel cut rotation speed during deceleration. In this way, -1 has the problem that drivability deteriorates due to torque fluctuations because the amount of intake air changes rapidly when switching between introducing and shutting off bleed air, and this deterioration of drivability occurs at low torque levels. Since the rotation speed and the load feel large when the load is low, it was necessary to set the switching rotation speed to be as large as the idle rotation speed. This switching rotation speed is higher than the fuel cut rotation speed during deceleration (this was also the case in the above-mentioned earlier application.In addition, in the above-mentioned earlier application, during non-fuel cut, a predetermined rotation speed higher than the fuel cut rotation speed is applied). The control valve is closed when the number of
Since the control valve is open during the fuel cut, the control valve is actually closed when the fuel is restored at the end of the fuel cut. However, if this switching rotation speed was set higher than the fuel cut rotation speed during deceleration, a problem occurred in that the number of times the control valve was turned on and off increased.For example, in the above-mentioned earlier application, the control valve was The control valve is opened, but a delay is provided before the fuel cut is actually executed, and when the bleed air cutoff rotation speed is detected during the delay, the control valve that was open is opened. The control valve is then closed with the release of the delay, and then the control valve is closed again with the end of the fuel cut.

In this way, the number of times the control valve is turned on and off increases, the durability of the control valve decreases, and torque fluctuations are not eliminated.

[Means for solving problems]

A supercharged engine according to the present invention includes a mechanical supercharger constituted by a Roots pump and a fuel supply means, in which an end face of a rotor of the supercharger and an end face of a rotor of the supercharger are arranged in a casing of the supercharger. An air introduction passage is connected to an annular space formed around the support shaft between a bearing that supports the support shaft of the rotor, a control valve is disposed in the middle of the cough air temperature passage, and the fuel supply The control valve is characterized in that the control valve is closed at a rotation speed below the fuel cutoff speed of the means.

(Example) In FIG. 1, 10 indicates an engine main body, and the engine main body 10
As is known in the art, a piston (not shown) is inserted therein so as to be able to reciprocate, and the piston is connected to the crankshaft by a connecting rod. An intake passage 12 and an exhaust passage 14 are communicated with the combustion chamber of the engine body 10, and an intake valve and an exhaust valve are arranged in each of them.

The intake passage 12 is formed by an intake pipe, an intake manifold, and an intake port as is well known, and an air cleaner 16, an air flow meter 17, a throttle valve 18, a supercharger 20, and a fuel injection valve 21 are arranged in this order from the upstream side. The supercharger 20 is composed of a Roots pump having a cocoon-shaped rotor 22, and an electromagnetic clutch attached to the support shaft of one of the rotors 22 is connected to a crank pulley by a timing belt. It is mechanically driven by the rotation of the crankshaft.

FIG. 2 is a detailed view of the supercharger 20, in which the rotor 22 is disposed within a casing 24, and the rotor 22 is disposed within a casing 24.
The support shaft 26 extends through the end wall 24a of the casing 24, and is supported by a bearing 28 in a hole wall formed through the end wall 24a.

A lubricant is applied to the bearings 28. For example, in FIG. 2, the left bearing 28 is a grease-filled type, and the right bearing 28 is
is the type that requires oil. Seal means 30 are arranged inside these bearings 28 to prevent these lubricants from flowing towards the rotor 22. Further, a gear 32 is attached to one end of the support shaft 26 of each rotor 22, and an electromagnetic clutch 34 is attached to the opposite end of one support shaft 260. The electromagnetic clutch 34 can be connected to the crankshaft as described above, so that the supercharger 20 is driven by the engine. Further, a cover is attached to cover the gear 32, forming an oil chamber 32a.

Furthermore, as shown in FIG. 2, a support shaft 2
An annular space 36 is formed surrounding 6, and these annular spaces 36 are opened to the atmosphere through an air introduction passage.

That is, the atmosphere inlet passage consists of a port section 38 passing through the casing 24 and a pipe section 40 extending from the port to the atmosphere inlet, and as shown in FIG. It is formed.

As shown in FIG. 1, a control valve 42 is arranged in the atmosphere introduction passage 40. As shown in FIG. The control valve 42 has a valve member 4B operated by a solenoid 46, and this valve member 48 is urged by a spring 50 in the valve closing direction. Valve member 48
is normally biased toward the closing side by the action of a spring 500, and when the solenoid 46 is energized, it is pulled by the solenoid 46 and opens. A control device (ECU) 52 is provided to control the operation of this control valve 42, and this control device 52 controls several sensors representing the operating state of the engine, such as an air flow meter 17, a rotation speed sensor 54, and a throttle valve 18. A detection signal from an idle switch 56 or the like that detects the idle position is input.

FIG. 3 is a diagram showing details of the control unit (ECU) 52. The control device 52 is configured as a microcomputer and includes a central processing unit W (CPU) 5 having calculation and control functions.
8 and the read-only memory that stores the program (
ROM) 60 and a random access memory (RAM) 62 for storing data etc., which are connected to a bus 64.
are connected to each other, and receive detection signals from various sensors via an input/output interface 66.
A control signal is output to the control valve 42. As described above, the detection signal is input from the air flow meter 17, the rotation speed sensor 54, the idle switch 56, etc., and the control signal is sent to the fuel injection valve 21 and the control valve 42. In addition, the fuel injection valve 21
Since the control can be performed in a known manner, detailed explanation thereof will be omitted. However, it is clear that the fuel cut is carried out by not supplying fuel at predetermined fuel injection timings.

As schematically shown in FIG. 1, the supercharger 20 has a suction boat and a discharge boat located substantially opposite to each other in the circumferential direction of the casing 24, and performs a compression action twice for each rotation of the rotor 22. There is a small clearance space between the end face of the rotor 22 and the casing end wall 24a facing it.
This minute clearance space communicates with both the suction port and the discharge boat, and receives an intermediate pressure between the suction pressure and the boost pressure.

When the throttle valve 18 is fully open and the load is high, this intermediate pressure is approximately atmospheric pressure on the upstream side of the supercharger 20 and supercharging pressure on the downstream side, so this intermediate pressure is approximately half the supercharging pressure. On the other hand, during low load, including when the throttle valve 18 is throttled and idling, both the upstream and downstream sides of the supercharger 20 become negative and positive, so the pressure becomes negative. When the intermediate pressure is a positive pressure, the intermediate pressure is led to the atmospheric pressure portion of the intake passage 12 upstream of the throttle valve 18 through the atmospheric air introduction passage 38zn40, thereby eliminating the pressure difference before and after the bearing 28. This ensures the ability of the bearing 28 to retain lubricant. On the other hand, when the intermediate pressure is a negative pressure, air located upstream of the throttle valve 18 in the intake passage 12 is taken into the engine from the atmosphere introduction passage 382n40 through the end surface of the rotor of the supercharger 20, and passes through the throttle valve 18. Additional air will be inhaled in addition to the air inhaled.

This intake of additional air is preferable because it increases the rotation speed at low loads, such as idle rotation speed, above the controlled speed. An attempt is made to prevent such an increase in the idle speed.

FIG. 4 is a flow chart showing the control of the control 1FLL valve 42 described above. In step 70, the engine speed NE is read, and the process proceeds to step 71 to determine whether the idle switch 56 is turned on. If yes, proceed to step 72; if no, proceed to step 76. In step 72, it is determined whether or not the tube cutting is in progress; if yes, proceed to step 73, where the control valve 42
open. If no, the process proceeds to step 74, where the engine speed is set to the fuel cut speed N RT (1200
rpm)+hysteresis H (400 rpm+m). If no, it is determined that the engine speed has become lower than the fuel return speed, and the process proceeds to step 79, where the control valve is closed. In this case, step 74
Since we are looking at NRT+H, the control valve is not turned on or off depending on the hysteresis rotation speed. If YES in step 74, the process proceeds to step 73 to open the control valve. YES in step 74 indicates that there is a condition such as a delay in which fuel cant is not performed even if the fuel cut rotation speed is higher than the fuel cut speed, and in the case of a fuel cut delay, fuel cut will start immediately, so during these series of operations It is preferable to keep the control valve open during this time in order to avoid unnecessary turning on and off of the control valve.

If it is determined in step 71 that the idle switch 56 is not turned on, the process proceeds to step 76 and the control valve 4
2 is currently closed. If it is open, it is determined as no and the process proceeds to step 77, step 7
7, the engine speed NE is at the second predetermined value NA.
(for example, 1500 rpm), and if YES, proceed to step 73 and open the control valve 42, and if NO, proceed to step 79 and close the control valve 42. If YES in step 76, the process proceeds to step 7B where the engine speed NB is set to a second predetermined value (JN
A third predetermined value NB higher than A (for example, 1700 rp
m), and if yes, go to step 73; if no, go to step 79. Note that the fuel cut rotation speed NRT, which is the first predetermined rotation speed,
The relationship between the second predetermined value NA and the third predetermined value NB is shown in FIG.
This shows that the control valve 42 is opened and closed at a rotational speed with hysteresis when the control valve 42 is not turned on. That is, when the control valve is switched from open to closed when the rotational speed decreases, the lower second predetermined value NA is used, and conversely, when the control valve is switched from closed to open when the rotational speed increases, the higher second predetermined value NA is used. A third predetermined value NB is used.

〔Effect of the invention〕

As explained above, according to the present invention, the durability of the bearing of the supercharger can be increased by introducing atmospheric air, and the opening/closing conditions for the control valve disposed in the atmospheric air introducing passage during idling and deceleration are set during deceleration. Since the fuel cut-off is performed at a fuel cut-off rotation speed of 1, there is no unnecessary turning on and off of the control valve, and drivability and durability of the control valve are improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a supercharged engine to which the present invention is applied;
Figure 2 is a sectional view showing details of the turbocharger, Figure 3 is a diagram showing details of the control device, Figure 4 is a diagram showing the first example of the flowchart of the control valve, and Figure 5 is the same as Figure 4. It is a figure which shows the relationship of the predetermined rotation speed in a flowchart. 20...Supercharger, 22...Rotor, 2
6... Rotor support shaft, 28... Bearing, 36...
...Annular space, 38.40...Atmosphere introduction passage,
42...Control valve.

Claims (1)

[Claims] In an engine equipped with a mechanical supercharger constituted by a Roots pump and a fuel supply means, a bearing supporting an end face of a rotor of the supercharger and a support shaft of the rotor is provided in a casing of the supercharger. An air introduction passage is connected to an annular space formed around the support shaft, and a control valve is arranged in the middle of the air introduction passage, and the control valve is connected to the annular space formed around the support shaft. A supercharged engine characterized in that the engine is closed.