JP2012036829A - Blowby gas returning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a system with a simple construction by which the ventilation of a blowby gas can be suitably performed even in an operation region in which supercharging is not performed.SOLUTION: An upper stream side and a downstream side of a compressor 51 in an intake passage 3 are connected by a bypass passage 61, a jet pump 62 generating negative pressure is provided on the bypass passage 61 and a blowby passage 63 conducted from a crank chamber 7 is made to communicate with the bypass passage 61 via the jet pump 62. Furthermore, an intake throttle valve 65 is installed further upstream from a connection part of the bypass passage 61 in the intake passage 3. Upon non-supercharging, pressure on the upstream side of the compressor 51 is made negative with respect to that of the downstream side by throttling the intake throttle valve 65 and the blowby gas is sucked out of the crank chamber 7.

Description

  The present invention relates to a blow-by gas recirculation device for an internal combustion engine accompanied by a supercharger.

  In general, the crank chamber of an internal combustion engine is isolated from the combustion chamber by a cylinder and a piston. However, this isolation is not perfect, and unburned gas leaks in the compression stroke of the internal combustion engine, and combustion gas leaks into the crank chamber from the gap between the cylinder and the piston in the expansion stroke. The leaked blow-by gas may cause deterioration of the lubricating oil stored in the crank chamber and corrosion of the internal combustion engine body.

  For this reason, conventionally, it is common to implement a mechanism for ventilating blow-by gas accumulated in the crank chamber. For example, an upstream side and a downstream side of the compressor in the intake passage are connected by a bypass passage, and a jet pump that generates negative pressure is provided on the bypass passage, and the blow-by passage led from the crank chamber is bypassed via the jet pump. A blow-by gas recirculation device (ejector system) configured to communicate with a passage is known (see the following patent document).

  In the above blow-by gas recirculation device, the jet pump functions by utilizing the pressure difference generated between the upstream side and the downstream side of the compressor at the time of supercharging, and the blow-by gas in the crank chamber is sucked out by the negative pressure, Return to the upstream side of the compressor. However, at the time of non-supercharging, since the pressure difference between the upstream side and the downstream side of the compressor becomes small, there is a weakness that the blow-by gas ventilation action is not performed.

JP 2009-299645 A

  The present invention intends to realize a system capable of suitably ventilating blow-by gas even in an operation region where supercharging is not performed with a simple configuration.

  A blow-by gas recirculation device according to the present invention is a blow-by gas recirculation device applied to an internal combustion engine with a supercharger, the bypass passage connecting the upstream side and the downstream side of the compressor in the intake passage, and the bypass A jet pump on the passage for generating negative pressure; a blow-by passage for connecting an inner chamber in which blow-by gas is accumulated to the bypass passage via the jet pump; and the upstream side of the compressor in the intake passage. And an intake throttle valve installed further upstream than the bypass passage connection point. Here, the inner chamber is a concept including a crank chamber in which blow-by gas is generated, a cam chamber communicating with the crank chamber, and the like.

  At the time of non-supercharging, the intake throttle valve is throttled to make the upstream side of the compressor negative with respect to the downstream side, and blow-by gas is sucked out from the inner chamber.

  ADVANTAGE OF THE INVENTION According to this invention, the system which can ventilate blow-by gas suitably also in the driving | running area | region which does not perform supercharging is implement | achieved.

The figure which shows the structure of the internal combustion engine and blow-by gas recirculation apparatus in one Embodiment of this invention. The figure which illustrates the structure of a jet pump.

  An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, the outline | summary of the internal combustion engine 0 for vehicles to which the blowby gas recirculation apparatus 6 of this embodiment is applied is shown. The internal combustion engine 0 in this embodiment includes a plurality of cylinders 1 (one of which is shown in FIG. 1), an injector 11 that injects fuel into each cylinder 1, and intake air to each cylinder 1. An intake passage 3 for exhausting the exhaust gas, an exhaust passage 4 for discharging exhaust gas from each cylinder 1, an exhaust turbocharger 5 for supercharging intake air flowing through the intake passage 3, and an exhaust passage 4 to the intake passage 3. And an external EGR passage 2 for refluxing the EGR gas.

  The internal combustion engine 0 in this embodiment is a two-cylinder four-cycle engine, and there is a phase difference of 360 ° CA (crank angle) between the stroke of the first cylinder 1 and the stroke of the second cylinder 1. In other words, the piston 12 of the first cylinder 1 and the piston 12 of the second cylinder 1 are simultaneously raised and simultaneously lowered. Therefore, the volume of the crank chamber 7 in the crankcase of the internal combustion engine 0 is greatly expanded / reduced compared to a multi-cylinder engine having three or more cylinders.

  The intake passage 3 takes in air from the outside and guides it to the intake port of the cylinder 1. On the intake passage 3, an air cleaner 31, an intake throttle valve 65, a compressor 51 of the supercharger 5, an intercooler 32, a throttle valve 33, and a surge tank 34 are arranged in this order from the upstream.

  The exhaust passage 4 guides exhaust generated as a result of burning fuel in the cylinder 1 from the exhaust port of the cylinder 1 to the outside. A drive turbine 52 and a three-way catalyst 41 of the supercharger 5 are disposed on the exhaust passage 4.

  The exhaust turbocharger 5 is configured such that the drive turbine 52 and the compressor 51 are connected and linked in a coaxial manner. Then, the driving turbine 52 is rotationally driven by using the energy of the exhaust gas, and the compressor 51 is pumped by using the rotational force, whereby the intake air is pressurized and compressed (supercharged) and sent to the cylinder 1.

  The external EGR passage 2 realizes a so-called low pressure loop EGR. The pressure loss in the low-pressure loop EGR passage 2 is as small as several hundred Pa. The inlet of the external EGR passage 2 is connected to a predetermined location downstream of the three-way catalyst 41 in the exhaust passage 4. The outlet of the external EGR passage 2 is connected to a predetermined location in the intake passage 3 downstream of the intake throttle valve 65 and upstream of the compressor 51. An EGR cooler 21 and an EGR valve 22 are provided on the external EGR passage 2.

  In the low-pressure loop EGR, low-pressure exhaust gas close to atmospheric pressure is recirculated to the intake passage 3 through the EGR passage 2. For this purpose, the pressure around the outlet of the EGR passage 2 is reduced to a negative pressure by restricting the intake throttle valve 65 upstream of the outlet of the EGR passage 2. It should be noted that the pressure upstream of the intake throttle valve 65 in the intake passage 3 becomes substantially atmospheric pressure or somewhat negative pressure due to the operation of the compressor 51. Incidentally, if the intake throttle valve 65 is throttled when the internal combustion engine 0 is decelerated, the intake throttle valve 65 becomes a resistance and the pressure around the outlet of the EGR passage 2 is disturbed, and the EGR gas flowing through the EGR passage 2 The amount vibrates greatly. Therefore, when the internal combustion engine 0 is decelerated, the intake throttle valve 65 is fully opened once, and the transient control is performed to return to the original opening after the engine torque is reduced.

  An ECU (electronic control unit) 9 that controls operation of the internal combustion engine 0 is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like. The input interface includes a vehicle speed signal a output from the vehicle speed sensor that detects the vehicle speed, a rotation speed signal b output from the rotation speed sensor that detects the engine rotation speed, and a throttle position sensor that detects the opening of the throttle valve 33. The output throttle opening signal c, the intake pressure signal d output from the pressure sensor for detecting the intake pressure (supercharging pressure) in the surge tank 34, the water temperature signal e output from the water temperature sensor for detecting the cooling water temperature, etc. Is entered. From the output interface, the fuel injection signal f for the injector 11, the ignition signal g for the ignition plug (ignition coil thereof), the opening operation signal h for the EGR valve 22, and the opening degree for the intake throttle valve 65. An operation signal i or the like is output.

  The processor of the ECU 9 controls the operation of the internal combustion engine 0 by interpreting and executing a program stored in the memory in advance. The ECU 9 acquires various information a, b, c, d, and e necessary for controlling the operation of the internal combustion engine 0 via the input interface, and based on them, the intake air amount, the required fuel injection amount, the ignition timing, the target EGR Calculate the rate, etc. Then, various control signals f, g, h, i corresponding to the calculation result are applied through the output interface.

  Thus, the blow-by gas recirculation device 6 of this embodiment is for sending blow-by gas generated in the inner chambers 7 and 8 of the internal combustion engine 0 to the intake passage 3, and includes a bypass passage 61, a jet pump 62, The blow-by passage 63, the fresh air passage 64, the intake throttle valve 65, and the PCV passage 66 are provided.

  The bypass passage 61 connects the upstream side and the downstream side of the compressor 51 in the intake passage 3. In particular, the outlet of the bypass passage 61 is connected to a location upstream of the compressor 51 and downstream of the intake throttle valve 65.

  The jet pump 62 is on the bypass passage 61 and generates a negative pressure. As illustrated in FIG. 2, the jet pump 62 includes a nozzle 621 provided on the inlet side connected to the downstream side of the compressor 51, and a diffuser 622 provided on the outlet side connected to the upstream side of the compressor 52. The decompression chamber 623 interposed between the nozzle 621 and the diffuser 622 serves as an element. When the pressure at the inlet of the bypass passage 61 is higher than the pressure at the outlet, air is ejected from the nozzle 621 toward the diffuser 622, and a negative pressure is generated in the decompression chamber 623. The magnitude of the negative pressure varies depending on the pressure difference between the inlet and the outlet of the bypass passage 61, that is, the pressure difference between the upstream side and the downstream side of the compressor 51.

  The blow-by passage 63 allows the crank chamber 7 of the internal combustion engine 0 to communicate with the bypass passage 61. One end of the blow-by passage 63 is connected to the decompression chamber 623 of the jet pump 62. When the internal combustion engine 0 is a two-cylinder engine, it is preferable to provide a reed valve 631 on the blow-by passage 63. The reed valve 631 is operated by a differential pressure before and after that. The reed valve 631 is opened when the volume of the crank chamber 7 is reduced (when the piston 12 of each cylinder 1 is lowered) and closed when the volume of the crank chamber 7 is enlarged (when the piston 12 of each cylinder 1 is raised).

  The fresh air passage 64 allows the cam chamber 8 in the cylinder head cover of the internal combustion engine 0 to communicate with the intake passage 3. The cam chamber 8 is connected to the crank chamber 7 via an internal passage (not shown), and fresh air and blow-by gas can be exchanged with the crank chamber 7. One end of the fresh air passage 64 is connected to a location upstream of the intake throttle valve 65 in the intake passage 3.

  The PCV passage 66 allows the crank chamber 7 of the internal combustion engine 0 to communicate with the intake passage 3. One end of the PCV passage 66 is connected to the surge tank 34. A PCV valve 661 is provided on the PCV passage 66. The PCV valve 661 is closed when the intake pressure in the surge tank 34 is equal to or higher than the atmospheric pressure, and the opening degree of the PCV valve 661 increases as the intake pressure in the surge tank 34 decreases (as the negative pressure with respect to atmospheric pressure). However, when the intake pressure in the surge tank 34 is significantly reduced and falls below a predetermined threshold, such as during idling, the opening is reduced.

  Oil separators 632, 641, 662 exist near the other ends of the blow-by passage 63, the fresh air passage 64, and the PCV passage 66. The oil separators 632, 641, 662 have a labyrinth structure and perform a gas-liquid separation action to separate the lubricating oil contained in the flowing gas from the gas, and prevent the lubricating oil from being lost from the crank chamber 7. To do.

  In the supercharging region (or positive pressure region) in which the supercharger 5 performs work, the pressure on the downstream side of the compressor 51 is naturally higher than the pressure on the upstream side of the compressor 51. Due to the pressure difference between the upstream side and the downstream side of the compressor 51, a negative pressure is generated in the decompression chamber 623 of the jet pump 62. Due to this negative pressure, the blow-by gas in the crank chamber 7 is sucked into the decompression chamber 623 through the blow-by passage 63 and flows back from the outlet of the bypass passage 61 to the upstream side of the compressor 51 in the intake passage 3. At the same time, fresh air flows from the intake passage 3 via the fresh air passage 64 into the cam chamber 8 and the crank chamber 7, and expells blow-by gas in the crank chamber 7.

  On the other hand, when the turbocharger 5 is in a light load range (or negative pressure range) where no work is performed, an opening operation signal i is input from the ECU 9 to the intake throttle valve 65, and the opening degree of the intake throttle valve 65 is set. Perform the squeezing operation. Then, a negative pressure is generated on the upstream side of the compressor 51, and the pressure on the downstream side of the compressor 51 is relatively higher than the pressure on the upstream side of the compressor 51. Accordingly, a negative pressure is generated in the decompression chamber 623 of the jet pump 62, and blow-by gas in the crank chamber 7 is sucked out and recirculates from the outlet of the bypass passage 61 to the upstream side of the compressor 51 in the intake passage 3. Also in this case, it goes without saying that fresh air flows into the cam chamber 8 and the crank chamber 7 via the fresh air passage 64.

  Furthermore, since the PCV valve 661 is opened unless the intake pressure in the surge tank 34 is extremely reduced in the light load region, blow-by gas can be discharged also through the PCV passage 61.

  In this embodiment, the present invention is applied to the internal combustion engine 0 accompanied by the supercharger 5, and a bypass passage 61 connecting the upstream side and the downstream side of the compressor 51 in the intake passage 3, and the negative pressure on the bypass passage 61. Are connected to the upstream side of the compressor 51 in the intake passage 3, the jet pump 62 for generating air, the inner chambers 7 and 8 in which the blow-by gas is accumulated, and the bypass passage 61 via the jet pump 62. The blow-by gas recirculation device 6 including the intake throttle valve 65 installed further upstream than the connection portion of the bypass passage 61 is configured.

  According to this embodiment, even during non-supercharging, the intake throttle valve 65 is throttled so that the upstream side of the compressor 51 becomes negative with respect to the downstream side, and the blow-by gas is passed from the inner chambers 7 and 8 through the blow-by passage 63. Can be sucked out. As a result, it becomes possible to ventilate the blow-by gas suitably regardless of whether it is supercharged or non-supercharged.

  At the time of idling, the intake pressure in the surge tank 34 is remarkably lowered and the PCV valve 661 is closed. At this time, the blowby gas can be recirculated from the blowby passage 63 to the intake passage 3 via the bypass passage 61. In other words, since it is not necessary to open the PCV valve 611 during idling for the purpose of ventilation of blow-by gas, idling operation is stabilized.

  Since the pressure in the crank chamber 7 can be sufficiently reduced, the resistance to the downward movement of the piston 12 is reduced, the pump loss is reduced, and the fuel efficiency is improved. In addition, fluctuations in the lubricating oil level stored in the oil pan, leakage of lubricating oil between the oil pan and the cylinder block, and the like can be suppressed.

  The present invention is not limited to the embodiment described in detail above. For example, when the internal combustion engine 0 is a multi-cylinder engine having three or more cylinders, the volume of the crank chamber 7 does not expand or contract so much, and the reed valve 631 is unnecessary.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to an internal combustion engine with a supercharger mounted on a vehicle or the like.

DESCRIPTION OF SYMBOLS 0 ... Internal combustion engine 3 ... Intake passage 5 ... Supercharger 51 ... Compressor 6 ... Blow-by gas recirculation device 61 ... Bypass passage 62 ... Jet pump 63 ... Blow-by passage 65 ... Intake throttle valve 7, 8 ... Inner chamber (crank chamber, cam) Room)

Claims (1)

A blowby gas recirculation device applied to an internal combustion engine with a supercharger,
A bypass passage connecting the upstream side and the downstream side of the compressor in the intake passage;
A jet pump on the bypass passage for generating negative pressure;
A blow-by passage that allows an internal chamber in which blow-by gas is accumulated to communicate with the bypass passage via the jet pump;
A blow-by gas recirculation device comprising: an intake throttle valve installed further upstream than a connection portion of the bypass passage connected to the upstream side of the compressor in the intake passage.

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