JP2017115670A - Internal combustion engine with exhaust turbocharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a phenomenon that oil is sucked into a compressor chamber of an exhaust turbocharger by using existing devices.SOLUTION: Such oil leakage that oil is sucked into a compressor chamber occurs in a low-load high-rotation region. Then, a risk region is set about a throttle opening and intake pressure, a risk region is also set about an engine rotation number in advance, and when both the regions reach the risk regions, it is determined that countermeasures should be taken, and a pressure boosting measure such as the opening of a waste gate valve (or a rise of an opening) is taken. Since it is not necessary to newly add a control element, a rise of a cost can be prevented.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an internal combustion engine provided with an exhaust turbocharger, and is suitable for an internal combustion engine for a vehicle.

  A turbocharger used for an internal combustion engine includes a turbine blade that rotates with exhaust gas, and a compressor blade that pressurizes clean air in an intake system. The turbine blade and the compressor blade are fixed to a rotating shaft. Yes. The rotating shaft is arranged in a substantially horizontal posture. As a means for bearing the rotating shaft, a floating metal (floating bearing) disposed on the bearing portion provided in the housing via an oil layer is used in terms of durability, smoothness of rotation, prevention of heat generation, and the like. There are many.

  For example, as disclosed in Patent Document 1 and shown in FIG. 3, the compressor blade 1 is disposed in an annular compressor chamber 2, and a cavity 4 that opens downward is provided between the compressor chamber 2 and the bearing portion 3. Is formed. Therefore, the partition wall 5 exists between the cavity 4 and the compressor chamber 2. Further, a bush 7 exposed to the cavity 4 is fixed to the rotary shaft 6, and the bush 7 is rotatably held by the partition wall 5 via a ring body 8 and an oil seal 9. Further, the bush 7 is formed with a flange 10 facing the one end surface 5 a of the bearing portion 3.

  The rotating shaft 6 is held by the bearing portion 3 via the floating metal 11, but since there is a slight gap between the bearing portion 3 and the floating metal 11, the oil flows into one end surface 3 a of the bearing portion 3. Spills towards Therefore, a hollow portion 5 is formed between the partition wall 5 and the bearing portion 3 so that the oil that has flowed out flows downward from the hollow portion 5.

  However, when the rotary shaft 6 rotates at a high speed, oil may leak into the compressor chamber 2 from a slight gap between the bush 7 and the oil seal 9 despite the provision of the cavity 5. There was a risk of lowering the output and worsening the exhaust gas.

  This phenomenon of oil leakage (oil suction) is caused by the negative pressure in the compressor chamber. Therefore, it is considered to prevent oil leakage. As an example, Patent Document 2 provides a bypass passage that communicates the upstream side and the downstream side of the compressor chamber, and an on-off valve is provided in the bypass passage. A configuration is disclosed in which an on-off valve is opened when it is determined that the compressor chamber has negative pressure.

JP2013-155668A JP 2012-67614 A

  Japanese Patent Application Laid-Open No. 2004-228561 attempts to suppress negative pressure in the compressor chamber, but has a problem that the structure becomes complicated and cost increases because a pressure sensor, a bypass passage, and an on-off valve must be newly added. In addition, when the throttle valve is squeezed, if the bypass passage is opened, the amount of air to the compressor chamber decreases, and on the contrary, there is a concern that the negative pressure increases (to the vacuum side).

  The present invention has been made in view of such a current situation, and is intended to enable oil leakage prevention without adding a new element.

  The oil leakage into the compressor chamber is caused by the negative pressure in the compressor chamber. However, the inventors of the present application have studied that the negative pressure in the compressor chamber does not simply depend on the engine speed, and the compressor outlet It was found that there was a close relationship between pressure and compressor blade speed. For example, if the compressor blades rotate at a high speed with a small amount of air flowing into the compressor chamber, the compressor blades act like a vacuum pump, and the compressor chamber reaches negative pressure. This means that a negative pressure in the compressor chamber occurs remarkably in the high rotation region.

  The amount of intake air into the compressor chamber is closely related to the opening of the throttle valve, but the opening of the throttle valve can be detected by a rotation angle sensor for so-called electronic throttle control. In addition, the pressure of the intake system (intake negative pressure) can be conventionally detected by an intake pressure sensor.

  The present invention has been made on the basis of such knowledge, and has been conceived that oil leakage to the compressor chamber can be suppressed using existing control elements, and the present invention has been completed.

  That is, the present invention is an internal combustion engine provided with an exhaust turbocharger, and the internal combustion engine has at least one of intake pressure, throttle opening, engine speed, and wastegate valve opening. From the plurality of values, a comparative numerical value is obtained as to whether or not the compressor chamber in the exhaust turbocharger has reached a range that requires countermeasures against oil leakage, and when the comparative numerical value reaches a preset reference range, the comparative numerical value Is controlled so as to be a value outside the reference range.

  “Obtaining a comparative value of whether or not the compressor chamber in the exhaust turbocharger has reached the required range for oil leakage measures” does not necessarily mean estimating the absolute value of the pressure. It is obtained (calculated) as some numerical value to determine whether or not the operation situation that requires countermeasures against leaks is reached (however, the absolute value of pressure is estimated, the pressure inside or outside of the seal is estimated, and the pressure difference) Is not to be excluded.)

  As described above, the negative pressure in the compressor chamber appears significantly in the low load / high rotation range, but the load (or torque) is closely related to the fuel injection amount, throttle opening, and intake pressure. Can be equated with supercharging pressure. Further, the exhaust turbocharger is provided with a waste gate valve that bypasses the exhaust gas downstream, but the opening degree of the waste gate valve is also closely related to the rotation speed and torque of the compressor blades. Further, the rotational speed of the compressor blade is proportional to the flow rate of the exhaust gas, but the flow rate of the exhaust gas is closely related to the rotational speed of the engine.

  Accordingly, it is possible to predict a situation in which the compressor chamber becomes negative pressure by combining a plurality of these elements (variables). Therefore, using a plurality of elements as variables, create a map of the dangerous area where the compressor chamber is estimated to be negative pressure, and when multiple elements reach a combination of dangerous areas, control to increase the pressure in the compressor chamber .

  The control for increasing the pressure in the compressor chamber includes a method for reducing the rotational torque of the compressor blades and a method for increasing the amount of air flowing into the compressor chamber, and either one or both can be employed. The simplest and most effective method for reducing the rotational torque of the compressor blades is to open the waste gate valve (or increase the opening) to reduce the amount of exhaust gas flowing into the turbine chamber.

  The rotational torque of the compressor blades (or the rotational torque of the turbine blades) is proportional to the kinetic energy of the exhaust gas, but the exhaust gas has a higher kinetic energy as the temperature is higher. Therefore, when the temperature of the exhaust gas is reduced, the pressure in the compressor chamber can be increased through a reduction in the rotational torque of the compressor blades.

  Further, when the ignition timing is advanced, the time during which the combustion gas is exposed to the cylinder and the cylinder head becomes longer, so that the heat is absorbed by the cylinder block and the cylinder head and the temperature of the exhaust gas is lowered. It can contribute to the pressure increase in the compressor chamber through the torque reduction.

  Recent vehicle internal combustion engines are equipped with a valve timing adjusting device. However, if the closing timing of the intake valve is delayed in the intake stroke, the temperature of the exhaust gas tends to decrease because it becomes close to the Atkinson cycle and the thermal efficiency increases. . Therefore, in this case as well, the pressure in the compressor chamber can be increased through a decrease in the torque of the compressor blades. The suppression of the fuel injection amount also causes the temperature of the exhaust gas to decrease, and thus acts to increase the pressure in the compressor chamber.

  When the throttle opening is increased, the intake pressure (supercharging pressure) increases and the amount of air flow to the compressor chamber increases, so that the compressor chamber pressure is increased.

  In the present invention, since the pressure in the compressor chamber (more precisely, the pressure difference between the compressor chamber and the bearing portion side) can be controlled so as not to fall below a predetermined value, oil suction (leakage) into the compressor chamber is suppressed. It is possible to prevent output reduction and exhaust gas component deterioration. Also, oil consumption can be suppressed.

  Since the pressure in the compressor chamber can be estimated using existing control elements, it is not necessary to add a new member, and an increase in cost can be prevented. In addition, the countermeasure for increasing the pressure in the compressor chamber can also use the control of the normal internal combustion engine as it is, so that there is no cost for taking the countermeasure.

  As described above, the present invention can be easily applied to an existing internal combustion engine, and thus has excellent versatility.

1 is a schematic diagram of an internal combustion engine to which the present invention is applied. (A) is a graph showing the relationship between the internal / external differential pressure of the seal portion of the rotating shaft and the compressor blade rotational speed, (B) is a graph showing an area where oil leakage occurs in a combination of engine torque and rotational speed, C) is a schematic graph for showing an example of a control method. It is a partial sectional view of an exhaust turbocharger.

(1) Configuration of Internal Combustion Engine Next, an embodiment of the present invention will be described based on the drawings. First, the configuration of the internal combustion engine will be described with reference to FIG. The internal combustion engine includes an engine body 21 in which a cylinder block and a cylinder head are integrally displayed. The engine body 21 includes a crankshaft 22, and a rotation sensor 23 that detects the number of rotations (rotational speed) of the crankshaft 22 is provided at one end surface of the engine body 21.

  An intake manifold 25 is fixed to the intake side surface 24 of the cylinder head constituting the engine body 21, and a surge tank 26 is connected to the intake manifold 25. The surge body 26 is fixed with a throttle body having a throttle valve 27 built therein, and the throttle body and the air cleaner 28 are connected by an intake passage 29. An injector 31 corresponding to each cylinder 30 is attached to the cylinder head constituting the engine body 21.

  Further, the cylinder head is provided with a valve timing adjusting device (VVT) 32 for controlling the opening / closing timing of one or both of the intake valve and the exhaust valve. A spark plug 33 is provided for each cylinder.

  On the other hand, an exhaust manifold 36 is fixed to the exhaust side surface 35 of the cylinder head. An exhaust passage 37 is connected to a collecting portion of the exhaust manifold 36, and a turbine chamber 39 of an exhaust turbocharger 38 is inserted into the exhaust passage 37. The upstream side and the downstream side of the turbine chamber 39 are connected by a bypass passage 40, and a waste gate valve 41 is provided in the bypass passage 40.

  A supercharging take-out passage 42 and a supercharging application passage 43 are branched from the intake passage 28, and the supercharging take-off path 42 is connected to the inlet of the compressor chamber 44 in the exhaust turbocharger 38 to provide supercharging. The passage 41 is connected to the outlet of the compressor chamber 44. Naturally, turbine blades 45 are disposed in the turbine chamber 39, and compressor blades 47 are disposed in the compressor chamber 44, and both are integrally connected by a rotating shaft 48.

  In the intake passage 28, for example, an intake pressure sensor 49 is provided in a portion downstream of the connection portion of the supercharging application passage 41. The intake pressure sensor 47 and the rotation sensor 23 are electrically connected to an ECU (Engine Control Unit). Further, the throttle valve 27, each injector 30, the wastegate valve 41, and the valve timing adjusting device 32 are each driven by a command from the ECU.

(2). Control Mode (A) in FIG. 2 shows the relationship between the value obtained by dividing the pressure at the outlet of the compressor chamber 44 by the pressure at the rotary shaft seal and the rotary shaft 48. The value obtained by dividing the pressure at the outlet of the compressor chamber 44 by the pressure at the rotary shaft seal portion is simply the pressure at the outlet portion of the compressor chamber 44 (2) divided by the pressure at the location of the oil seal 9 in FIG. It is the value. At 1.0, both pressures are balanced and there is no pressure difference. In the region where the numerical value exceeds 1, 44 (2) in the compressor chamber is negative at the bearing. doing.

  From FIG. 2A, it is shown that the compressor chamber 44 (2) becomes negative as the rotational speed of the compressor blade 46 (1) increases.

  In FIG. 2 (B), the relationship between the engine torque and the number of revolutions indicates the combination of regions where oil leakage occurs in the compressor chamber 44 (2). From this graph, the low load / rotation region is shown. It can be understood that oil leakage occurs and increases. This also matches the graph of (A). In addition, what is shown by a dotted line in FIG. 2B is a graph showing the relationship between the torque and the rotational speed in the full throttle state.

  In FIG. 2C, the throttle opening (or intake pressure) and the engine speed are divided into three areas of low (L), medium (M), and high (H), and nine operation regions as a whole. Show. As described above, since oil leakage is observed in the low load / high rotation range, dangerous areas are set for the throttle opening, intake pressure, and engine speed, both of which are dangerous. When reaching the region, it is determined that the oil leakage countermeasure necessary situation has been reached, and the countermeasures such as opening the waste gate valve 41 or increasing the opening degree are set.

  This control is so-called zone management, but instead of this, or in addition to this, the pressure difference between the inside and outside of the seal part of the rotating shaft is directly measured by the sensor, or the engine speed and intake negative pressure (supercharging) Pressure), wastegate valve opening, etc. are always calculated and detected, and if the compressor chamber reaches negative pressure (or if negative pressure is predicted from the change in differential pressure), It is also possible to control that negative pressure is prevented by this means.

  As a countermeasure, the control of the wastegate valve 41 is most effective, but the wastegate valve 41 may reach a low load / high rotation region in a fully opened state. In this case, other countermeasures such as ignition timing advance control and intake valve delay closing are taken. It is useful to set the priority of countermeasures in advance. It is also possible to set to take multiple countermeasures at the same time.

  The present invention can actually be embodied in an internal combustion engine. Therefore, it can be used industrially.

21 Engine Body 22 Crankshaft 23 Rotation Sensor 25 Intake Manifold 27 Throttle Valve 29 Intake Passage 32 Valve Taming Adjuster (VVT)
33 Spark plug 36 Exhaust manifold 37 Exhaust passage 38 Exhaust turbocharger 39 Turbine chamber 41 Wastegate valve 42, 43 Supercharge passage 44 Compressor chamber 46 Compressor blade

Claims (1)

An internal combustion engine equipped with an exhaust turbocharger,
From a plurality of values including at least one of intake pressure, throttle opening, engine speed, and wastegate valve opening, the compressor chamber in the exhaust turbocharger falls within a range that requires countermeasures against oil leakage. When the comparison numerical value is calculated and the comparison numerical value reaches a preset reference range, control is performed so that the comparison numerical value is a numerical value deviating from the reference range.
An internal combustion engine with an exhaust turbocharger.

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