JP5119916B2 - Blow-by gas processing equipment - Google Patents

Description

  The present invention relates to a blow-by gas processing apparatus for a gasoline engine that returns blow-by gas leaking into a crankcase of the gasoline engine to an intake system.

  In a gasoline engine, there is a problem that the deterioration of lubricating oil is promoted by blow-by gas leaking into the crankcase. Conventionally, fresh air is introduced into the crankcase and blow-by gas is taken out from the crankcase to take in the air. A blow-by gas processing apparatus is used which is returned to the system. This blow-by gas processing device generally has a fresh air passage between the upstream side of the throttle valve of the intake system and, for example, the cylinder head of the engine body, and between the downstream side of the throttle valve of the intake system and the crankcase. A blow-by gas passage is provided therebetween, and the blow-by gas passage is provided with a flow rate control valve (so-called PCV valve) whose opening degree changes according to the negative pressure on the downstream side of the throttle valve. In this case, under normal operating conditions excluding the high load region, sufficient negative pressure is generated in the intake system on the downstream side of the throttle valve, so that the new air passage passes through the cylinder head and enters the crankcase. The blow-by gas returns to the intake system on the downstream side of the throttle valve via the blow-by gas passage and is introduced into the combustion chamber in such a manner that the air is introduced and pushed out by the fresh air. That is, the inside of the crankcase is always ventilated with fresh air, and deterioration of the lubricating oil due to blow-by gas is suppressed.

  However, in recent years, it has been practically used in part to control the intake air amount without relying on the throttle valve by controlling the intake valve opening / closing timing with a variable valve operating device. There is a case where a negative pressure sufficient for ventilation of blow-by gas cannot be generated, and the blow-by gas concentration in the crankcase becomes high, which may promote deterioration of the lubricating oil.

Therefore, in Patent Document 1, a negative pressure pump that sucks blow-by gas from the crankcase and discharges it to the intake system side is provided in the blow-by gas passage. In the embodiment of Patent Document 1, the negative pressure pump is a mechanical type that is always driven in conjunction with the crankshaft of the engine, so that blow-by gas can be reliably supplied regardless of the negative pressure situation downstream of the throttle valve. Can be processed.
JP 2001-164918 A

  However, in the mechanical negative pressure pump as described above, the negative pressure pump always operates during engine operation regardless of the blowby gas concentration in the crankcase, that is, the NOx concentration, and the NOx concentration is low. However, unnecessary energy loss may be caused by unnecessarily operating the negative pressure pump.

  The present invention has been made in view of such a problem, and introduces fresh air into the crankcase from the upstream side of the intake system and a blow-by gas passage communicating the crankcase of the gasoline engine and the intake system. A fresh air passage provided so as to perform, an air pump that is provided in the blow-by gas passage or the fresh air passage and that pumps the blow-by gas or fresh air, and NOx concentration acquisition means that acquires the NOx concentration in the crankcase And pump control means for controlling the operation of the air pump based on the NOx concentration.

  According to the present invention, the inside of the crankcase can be reliably ventilated even when the intake pump cannot sufficiently obtain the suction negative pressure, and the operation of the air pump is controlled in accordance with the NOx concentration. While keeping the blowby gas concentration at a low level and suppressing deterioration of the lubricating oil, unnecessary operation of the air pump can be suppressed and energy loss can be suppressed.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a first embodiment in which the present invention is applied to a vehicular gasoline engine 1. The gasoline engine 1 is configured, for example, as an in-cylinder direct injection type in which a fuel injection valve (not shown) is disposed toward a cylinder, and can realize ultra lean combustion. The intake passage 2 connected to the intake port of the gasoline engine 1 includes a throttle valve 3, and an air cleaner 4 is interposed on the upstream side thereof. One end of the fresh air passage 5 is connected between the throttle valve 3 and the air cleaner 4, and the other end is connected to the cylinder head cover 6. The space in the cylinder head cover 6 and the space in the crankcase 7 are in communication with each other via a lubricating oil dropping hole, a chain passage or the like (not shown). Further, one end of the blowby gas passage 8 is connected to the crankcase 7 so as to take out blowby gas from the crankcase 7, and the other end is connected to the intake passage 2 downstream of the throttle valve 3.

  An air pump 9 is interposed in the fresh air passage 5. That is, the fresh air passage 5 includes an upstream fresh air passage 5a and a downstream fresh air passage 5b. The upstream fresh air passage 5a communicates the upstream side of the throttle valve 3 of the intake passage 2 and the intake side of the air pump 9. The downstream fresh air passage 5 b communicates between the discharge side of the air pump 9 and the inside of the cylinder head cover 6. The air pump 9 is an electric type driven by a motor.

  The gasoline engine 1 also detects the NOx concentration sensor 11 that directly detects the NOx concentration in the crankcase 7 and the temperature of the engine oil, that is, the oil temperature as one of sensor values related to the engine temperature. An oil temperature sensor 12 is provided. The control unit 10 outputs a control signal to an actuator such as the air pump 9 based on detection signals from the sensors 11 and 12 and controls the operation thereof.

  In FIG. 1, the flow of fresh air is indicated by white arrows, and the flow of blow-by gas is indicated by black arrows. As indicated by these arrows, when the air pump 9 operates in response to a signal from the control unit 10, fresh air is forcibly sent from the upstream side of the throttle valve 3 into the cylinder head cover 6 through the fresh air passage 5. The fresh air scavenges the space in the cylinder head cover 6 and then enters the crankcase 7. Blow-by gas is introduced into the intake passage 2 from the crankcase 7 through the blow-by gas passage 8 together with the fresh air, and finally. Sent to the combustion chamber. According to the configuration in which the blow-by gas is forcibly sent to the intake system using the air pump 9 as described above, the blow-by gas can be reliably processed regardless of the negative pressure state downstream of the throttle valve 3, and the crankcase 7 The blowby gas concentration inside can be kept low.

  In this embodiment, the operation of the air pump 9 is controlled according to the NOx concentration in the crankcase 7. More specifically, the operating voltage of the air pump 9 is increased as the NOx concentration increases, and the load / driving force of the air pump 9 is set higher. In this embodiment, as shown in FIG. 2, the operating voltage of the air pump 9 is switched in three stages according to the NOx concentration. Further, an appropriate hysteresis H1 is provided between the switching to the lowering side and the switching to the increasing side so that the operating voltage is not switched excessively.

  In the above embodiment, the NOx concentration is directly detected by the NOx concentration sensor 11, but without using such a special sensor, the NOx can be more simply used by using the engine load, the engine speed, and the like. The concentration may be estimated. For example, as shown in FIG. 3, the NOx generation amount is sequentially calculated from the map (A) based on the engine load and the engine speed and accumulated (B), and the accumulated NOx generation amount is accumulated to obtain the NOx concentration. Can be estimated (C).

  In addition to the NOx concentration, the operation of the air pump 9 may be controlled according to the oil temperature, water temperature, intake air temperature, and the like, which are engine temperature indicators. More specifically, since the engine oil is more likely to adsorb NOx as the engine temperature becomes lower, the load / driving force of the air pump 9 is set to be higher. In this embodiment, as shown in FIG. 4, the minimum operating voltage of the air pump 9 is switched in three stages according to the oil temperature detected by the oil temperature sensor 12. Then, the higher operating voltage obtained based on the minimum operating voltage and the NOx concentration is selected as the operating voltage of the air pump 9. Further, an appropriate hysteresis H2 is provided between the switching to the lower side and the switching to the increasing side so that the minimum operating voltage is not excessively switched. Or you may make it correct | amend the operating voltage calculated | required based on NOx density | concentration according to engine temperature. For example, the coefficient may be multiplied so that the NOx concentration increases as the engine temperature decreases.

  According to this embodiment, in addition to reliably ventilating the inside of the crankcase by the air pump 9, the operation of the air pump 9 is appropriately controlled according to the NOx concentration and further the engine temperature, and the flow rate of blow-by gas is thereby controlled. The energy loss can be suppressed by optimizing and unnecessary operation of the air pump 9 can be suppressed, and it can be avoided that the blow-by gas is excessively circulated and the combustion becomes unstable.

  FIG. 5 shows a blow-by gas processing apparatus according to a second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and a duplicate description is omitted as appropriate. In this second embodiment, the air pump 9 is a secondary air pump that introduces secondary air into the exhaust passage 13, and a master back pump that applies a brake negative pressure to the master back 14 of the vehicle brake system. And it is comprised so that it may be combined. The negative pressure take-out passage 15 connected to the master back 14 joins in the middle of the upstream fresh air passage 5a connected to the suction side of the air pump 9, and the master back throttle 16 is located upstream from this joining portion. It is intervened. The upstream side of the secondary air passage 17 connected to the exhaust passage 13 on the downstream side branches off from the downstream fresh air passage 5b connected to the discharge side of the air pump 9, and the secondary air passage is connected to this branching portion. A secondary air switching valve 18 that opens and closes 17 is provided.

  FIG. 6 is a flowchart schematically showing an example of control of the throttle 16 and the switching valve 18 by the control unit 10. In step S1, it is determined whether or not the master back pressure Pm detected by the pressure sensor 19 that detects the pressure (negative pressure) of the master back 14 is equal to or higher than a predetermined threshold value P0. If it is equal to or greater than the threshold value P0, the process proceeds to step S2, and the master back throttle 16 is closed. Thus, when the air pump 9 is operated, air is sucked only through the negative pressure extraction passage 15 on the master back 14 side, and the negative pressure in the master back 14 is strengthened. In the subsequent step S3, the operating voltage Vm necessary for the required negative pressure of the master back 14 is set.

  On the other hand, when the master back pressure Pm is less than the threshold value P0, that is, when the negative pressure of the master back 14 does not need to be particularly strengthened, the process proceeds from step S1 to step S4, and the master back throttle 16 is opened. Thus, when the air pump 9 is activated, air is sucked from both the upstream fresh air passage 5a of the fresh air passage 5 and the negative pressure extraction passage 15 on the master back 14 side. In step S5, the master back operating voltage Vm is initialized to zero.

  In step S6, the NOx concentration and oil temperature are read from the sensors 11 and 12, and in step S7, the operating voltage Vn is set based on the NOx concentration and oil temperature as described above.

  In step S8, it is determined whether secondary air is requested by another routine (not shown). If there is a request for secondary air, the process proceeds to step S9, where the secondary air passage 17 is opened by the secondary air switching valve 18. As a result, fresh air (air) delivered from the air pump 9 is also supplied to the exhaust passage 13 via the secondary air passage 17 as secondary air. In step S10, the secondary air operating voltage Va necessary for securing the required secondary air flow rate is set. The secondary air operating voltage Va is set in accordance with the open / close state of the master back throttle 16, that is, when the master back throttle 16 is closed, the master back operating voltage Vm is taken into account. The secondary air operating voltage Va is set.

  On the other hand, if there is no request for secondary air, the process proceeds from step S8 to step S11, and the secondary air passage 17 is closed by the switching valve 18. Thereby, even if the air pump 9 is operated, secondary air is not supplied, and all of the fresh air supplied from the air pump 9 is supplied into the cylinder head cover 6 through the fresh air passage 5. In the subsequent step S12, the secondary air operating voltage Va is initialized to zero.

  In step S13, the master back operating voltage Vm set in step S3 or S5, the operating voltage Vn set in step S7, and the secondary air operating voltage Va set in step S10 or S12. Among them, the one having the largest value is selected as the operating voltage V0 of the air pump 9. The air pump 9 is operated by the selected operating voltage V0.

  According to the second embodiment, in addition to obtaining the same effect as the first embodiment, the air pump 9 serves both as a secondary air pump and a master back pump. The configuration is simplified compared to the case where a separate pump is provided. In addition, when an air pump is provided in the blow-by gas passage as in the above-mentioned Japanese Patent Application Laid-Open No. 2001-164918, the air pump cannot be used as a secondary air pump. By providing the air pump 9 in the air passage 5, the air pump 9 can be used as a pump for secondary air.

  Further, by adjusting the opening by the master back throttle 16, it is possible to suppress the generation of excessive negative pressure and increase the driving efficiency while securing the brake negative pressure to the master back 14. Furthermore, by switching the switching valve 18 according to the demand of the secondary air, it is possible to secure the necessary secondary air and improve the exhaust performance, while eliminating the need to supply the secondary air more than necessary. Driving efficiency can be increased.

  In particular, as in the present embodiment, the master back throttle 16 is provided in the upstream fresh air passage 5a upstream of the joining portion of the negative pressure extraction passage 15, so that the master back throttle 16 is closed. Secondary air can be secured, and it is possible to achieve both high levels of securing brake negative pressure and improving exhaust performance by secondary air immediately after engine startup.

  Further, in an operation region where the fluctuation of the engine generated torque greatly affects the operating state of the air pump 9, such as during idling speed control, the operating voltage of the air pump 9, that is, the driving force, should be kept low or fixed to a constant value. Thus, the engine speed may be stabilized. In this case, in order to secure a necessary intake air amount, for example, the valve lift characteristic may be corrected by a variable valve operating apparatus (not shown).

The technical ideas of the present invention that can be understood from the above description are listed.
(1) A blow-by gas passage 8 that communicates the inside of the crankcase 7 of the gasoline engine 1 and the intake system (intake passage 2), and a fresh air is provided into the crankcase 7 from the upstream side of the intake system. A fresh air passage 5, an air pump 9 that is provided in the blow-by gas passage 8 or the fresh air passage 5 and pumps the blow-by gas or fresh air, and NOx concentration acquisition means that acquires the NOx concentration in the crankcase 7 ( NOx concentration sensor 11) and pump control means (control unit 10) for controlling the operation of air pump 9 based on the NOx concentration. According to this configuration, the air pump 9 can reliably ventilate the crankcase 7 regardless of the engine speed, the engine load, and the like, and the operation of the air pump 9 is controlled according to the NOx concentration. 9 unnecessary operations can be suppressed and energy loss can be reduced.
(2) The air pump 9 is provided in the fresh air passage 5 and sucks fresh air from the upstream side of the intake system and discharges it into the crankcase 7. In this case, as compared with the case where an air pump is provided in the blow-by gas passage 8, only the fresh air flows through the air pump 9 without flowing the blow-by gas, so that the failure and deterioration of the air pump 9 are suppressed.
(3) In addition, by providing the secondary air passage 17 that connects the discharge side of the air pump 9 and the exhaust passage 13, the air pump 9 can also be used as an air pump for secondary air.
(4) A secondary air switching valve 18 for opening and closing the secondary air passage 17 is provided. By switching the secondary air switching valve 18 according to the engine operating conditions, it is possible to secure the necessary secondary air and improve the exhaust performance, while eliminating the need to supply the secondary air more than necessary. Driving efficiency can be increased.
(5) The suction side of the air pump 9 is further connected to a master back 14 of a vehicle brake system, and the air pump 9 also serves as a master back pump. As a result, the brake negative pressure of the master back 14 can be reliably ensured with a simple configuration without providing a separate pump.
(6) A negative pressure take-out passage 15 connected to the master back 14 is joined to an upstream fresh air passage 5a that communicates the suction side of the air pump 9 and the intake system. A master back throttle 16 is provided in the upstream fresh air passage 5a. According to this configuration, it is possible to secure secondary air even when the master back throttle 16 is closed, and it is possible to secure high brake negative pressure and improve exhaust performance by secondary air immediately after engine start. It is possible to achieve both levels.
(7) In addition to using the NOx concentration sensor 11, the NOx concentration acquiring means can more simply estimate the NOx concentration by accumulating the NOx generation amount obtained from the engine load and the engine speed.
(8) Further, a temperature detecting means (oil temperature sensor 12) for detecting the engine temperature may be provided, and the operation of the air pump 9 may be controlled based on the NOx concentration and the engine temperature. In this case, for example, the lower the engine temperature, the easier the engine oil will adsorb NOx. Therefore, by setting the load and driving force of the air pump 9 to be higher, the NOx concentration at low temperatures is lowered. Deterioration of engine oil can be suppressed / prevented.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which shows the blow-by gas processing apparatus of the gasoline engine which concerns on 1st Example of this invention. The characteristic view which shows the relationship between NOx density | concentration and an operating voltage. Explanatory drawing in the case of estimating NOx concentration from engine load and engine speed. The characteristic view which shows the relationship between engine oil temperature and the minimum operating voltage. Structure explanatory drawing which shows the blow-by gas processing apparatus of the gasoline engine which concerns on 2nd Example of this invention. The flowchart which shows the flow of control concerning the said 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Gasoline engine 5 ... Fresh air passage 7 ... Crankcase 8 ... Blow-by gas passage 9 ... Air pump 10 ... Control part (pump control means)
11 ... NOx concentration sensor (NOx acquisition means)
12 ... Oil temperature sensor (temperature detection means)
14 ... Master back 16 ... Master back throttle 18 ... Secondary air switching valve

Claims (6)

A blow-by gas passage communicating the crankcase of the gasoline engine and the intake system;
A fresh air passage provided so as to introduce fresh air into the crankcase from the upstream side of the intake system;
An air pump that is provided in the fresh air passage and sucks fresh air from the upstream side of the intake system and discharges it into the crankcase ;
NOx concentration acquisition means for acquiring the NOx concentration in the crankcase;
Pump control means for controlling the operation of the air pump based on the NOx concentration;
Equipped with a,
A blow-by gas processing apparatus for a gasoline engine, wherein a secondary air passage connecting the discharge side of the air pump and an exhaust passage is provided, and the air pump also serves as a pump for secondary air . The blow-by gas processing apparatus for a gasoline engine according to claim 1 , further comprising a secondary air switching valve for opening and closing the secondary air passage. The blow-by gas of a gasoline engine according to claim 1 or 2 , wherein a suction side of the air pump is further connected to a master back of a vehicle brake system, and the air pump also serves as a master back pump. Processing equipment. A negative pressure extraction passage connected to the master back is joined to an upstream fresh air passage communicating the suction side of the air pump and the intake system, and an upstream fresh air passage upstream of the joining portion is connected to the upstream fresh air passage. 4. A blow-by gas processing apparatus for a gasoline engine according to claim 3 , wherein a throttle for master back is provided. The blow-by gas processing for a gasoline engine according to any one of claims 1 to 4 , wherein the NOx concentration acquisition means estimates the NOx concentration by accumulating the NOx generation amount obtained from the engine load and the engine speed. apparatus. Furthermore, a temperature detection means for detecting the engine temperature is provided,
The blow-by gas processing apparatus for a gasoline engine according to any one of claims 1 to 5 , wherein the pump control means controls the operation of the air pump based on the NOx concentration and the engine temperature.

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