Patent Application
20080058994
In the following, a preferred embodiment of the present invention will be described with reference to the drawings.
A cylinder head 3a of the engine 3 is connected to an intake pipe 4 (intake system) and an exhaust pipe 5, respectively, and a fuel injection valve (hereinafter called the “injector”) 6 is attached to face a combustion chamber. A fuel injection amount QINJ and an injection timing of the injector 6 is controlled by an ECU 2, later descried.
A crank angle sensor 21 (rotational speed detecting means) is provided on a crank shaft 3b of the engine 3. The crank angle sensor 21 comprises a magnet rotor 21a and an MRE pickup 21b, and generates a CRK signal which is a pulse signal as the crank shaft 3b rotates. The CRK signal is outputted every predetermined crank angle (for example, every 1°), and the ECU 2 calculates an rotational speed NE of the engine 3 (hereinafter called the “engine rotational speed”) based on the CRK signal.
The engine 3 is also provided with an EGR device (intake air amount controller) which has an EGR pipe 7a and an EGR control valve 7b. The EGR pipe 7a is connected to the intake pipe 4 and the exhaust pipe 5 so as to connect both. Part of exhaust gases of the engine 3 is fed back to the intake pipe 4 as an EGR gas through the EGR pipe 7a, thereby lowering a combustion temperature of the engine to reduce NOx in exhaust gases.
The EGR control valve 7b comprises a linear electromagnetic valve attached to the EGR pipe 7a. The duty ratio of a current supplied to the EGR control valve 7b is controlled by the ECU 2 to linearly control a valve lift amount, thereby adjusting the amount of fed-back EGR gas (hereinafter called the “EGR amount”). Specifically, as the duty ratio is larger, the valve lift amount increases, resulting in a larger EGR amount. When the duty ratio is zero, the EGR control valve 7b is controlled to fully close, resulting in the EGR amount equal to zero.
The engine 3 is further provided with a supercharger 8 (intake air amount controller) and an actuator 9 coupled to the supercharger 8. The supercharger 8 comprises a rotatable compressor blade 8a provided in the intake pipe 4 at a location upstream of a connection with the EGR pipe 7a; a rotatable turbine blade 8b and a plurality of pivotable variable vanes 8c provided in the exhaust pipe 5; and a shaft (not shown) which integrally couples the blades 8a, 8b. The supercharger 8 performs a supercharging operation for compressing intake air within the intake pipe 4 by the compressor blade 8a which is driven to rotate together with the turbine blade 8b, integrated therewith, which is driven to rotate by exhaust gases in the exhaust pipe 5.
The actuator 9 is of a diaphragm type which operates with a negative pressure, and is mechanically coupled to each variable vane 8c. The actuator 9 is supplied with a negative pressure from a negative pressure pump through a negative pressure supply passage (none of which is shown). A vane opening control valve 10 is provided halfway in the negative pressure supply passage. The vane opening control valve 10 comprises an electromagnetic valve, the opening of which is controlled by a driving signal from the ECU 2 to change the negative pressure supplied to the actuator 9. This causes the opening of the variable vane 8c (hereinafter called the “vane opening”) to change, thereby controlling a super charge pressure. Specifically, as the vane opening is smaller, exhaust gases flow into the turbine blade 8b at a lower flow rate, resulting in a reduction in the supercharge pressure. When the vane opening is fully closed, the supercharge pressure is zero.
The blow-by gas feedback device 15 feeds a blow-by gas in a crank case 3c of the engine 3 back to the intake pipe 4 as appropriate, and comprises a blow-by gas passage 16 and a PCV valve 17.
The blow-by gas passage 16 has one end connected to a cylinder head cover 3d of the engine 3, and the other end connected to the intake pipe 4 at a location upstream of the compressor blade 8a through a joint 30. The engine 3 is formed with a breather passage (not shown) from the cylinder head 3a to a cylinder block, and the blow-by gas is fed back to the intake pipe 4 through the breather passage, the cylinder head cover 3d and the blow-by gas passage 16.
The PCV valve 17 is provided at a connection of the blow-by gas passage 16 with the cylinder head cover 3d. The PCV valve 17 comprises a mechanical valve, and opens when the difference between pressures upstream and downstream thereof increases beyond a predetermined pressure, thereby feeding the blow-by gas back to the intake pipe 4.
The intake pipe 4 is provided with an intake air throttle valve (intake air amount controller) between a connection with the EGR pipe 7a and the compressor blade 8a for adjusting the intake air amount. The intake air throttle valve 11 is connected to an actuator 11a which comprises, for example, a DC motor. The opening of the intake air throttle valve 11 is variably controlled between a fully close opening and a fully open opening by controlling the duty ratio of a current supplied to the actuator 11a by the ECU 2.
An air flow meter 22 (intake air amount sensor) is also provided in the intake pipe 3 at a location upstream of the joint 30 with the blow-by gas passage 16. The air flow meter 22 detects an intake air amount QA, and outputs its detection signal to the ECU 2.
The ECU 2 is applied with a detection signal indicative of a speed of the vehicle (hereinafter called the “vehicle speed”) VP from a vehicle speed sensor 23.
The ECU 2 is based on a micro-computer which comprises an I/O interface, a CPU, a RAM, a ROM and the like. The detection signals from a variety of the aforementioned sensors 21-23 are inputted to the CPU after they have undergone A/D conversion and reshaping in the I/O interface.
The CPU determines the operating condition of the engine 3 in accordance with a control program and the like stored in the ROM in response to the input signals, controls the engine 3 including the fuel injection amount QINJ, and executes an abnormality determination process for the blow-by gas feedback device 15. In this embodiment, the ECU 2 implements abnormality determining means, changing degree calculating means, rotational speed detecting means, intake air amount correcting means, operating condition detecting means, and control means.
When the result of the determination at step 1 is NO, the EGR control valve 7b, the variable vane 8c, and the intake air throttle valve 11 are respectively controlled to be in their normal states (hereinafter called the “normal control”) (step 24), and a valve close control flag F_EBC, a throttling control flag F_THC, and an accumulation flag F_SCQA are all set to “0” (step 25). In addition, a post-correction intake air amount accumulation value SCQA is reset to zero (step 26), followed by the termination of this process.
On the other hand, when the result of the determination at step 1 is YES, indicating that the engine 3 is in the predetermined operating condition, it is determined whether or not the valve close control flag F_EBC is “1” (step 2).
When the result of this determination is NO, the openings of the EGR control valve 7b and the variable vane 8c are held at predetermined small openings (for example, 0° and 5°, respectively) which do not affect the intake air amount at step 3 (hereinafter called the “valve closing control”), and the intake air throttle valve 11 is once controlled to a predetermined large opening (valve opening control). Next, the valve close control flag F_EBC is set to “1” (step 4), and a first timer value TMDLY1 of a down-count type delay timer (not shown) is set to a first predetermined time TMREF1 (for example 1.5 sec) (step 5), followed by the termination of this process.
When the aforementioned step 4 is executed, the result of the determination at step 2 is YES, in which case it is determined whether or not the first timer value TMDLY1 is zero (step 6). When the result of this determination is NO, this process is terminated.
On the other hand, when the result of the determination at step 6 is YES, i.e., when the valve closing control has continued for the first predetermined time TMREF1 for the EGR control valve 7b and variable vane 8c, it is determined whether or not the throttling control flag F_THC is “1” (step 7) on the assumption that the intake air amount has been stabilized.
When the result of this determination is NO, the intake air throttle valve 11 is controlled to a predetermined opening smaller than that in the normal control (hereinafter called the “throttling control”). In this way the intake air amount is controlled to decrease. The predetermined opening is controlled, for example, to a predetermined idle opening during a fuel cut operation, and to a predetermined opening larger than the idle opening during a cruising operation.
Next, the throttle valve control flag F_THC is set to “1” (step 9), and a second timer value TMDLY2 is set to a second predetermined time TMREF2 (for example, 0.3 sec) (step 10), followed by the termination of this process.
When the aforementioned step 9 is executed, the result of the determination at step 7 is YES, in which case it is determined whether or not the second timer value TMDLY2 is zero (step 11). When the result of this determination is NO, this process is terminated.
On the other hand, when the result of the determination at step 11 is YES, i.e., when the second predetermined time TMREF2 has elapsed after the start of the throttling control for the intake air throttle valve 11, it is determined whether or not the accumulation flag F_SCQA is “1” (step 12) on the assumption that no influence is exerted by response delays of the intake air throttle valve 11 and the intake air amount associated with the throttling control.
When the result of this determination is NO, the accumulation flag F_SCQA is set to “1” (step 13), a third timer value TMDLY3 is set to a third predetermined time TMREF3 (for example, 2.0 sec) (step 14), and the process goes to step 15. Also, when the step 13 is executed, the result of the determination at step 12 is YES, in which case the flow goes directly to step 15.
At step 15, an intake air amount correction coefficient KQA is calculated by searching a table shown in
Next, the post-correction intake air amount CQA is calculated by multiplying the intake air amount QA detected by the air flow meter 22 by the intake air amount correction coefficient KQA (step 16). This correction is intended for a conversion of the intake air amount QA to a value when the engine rotational speed NE is at the reference rotational speed NEO. This is because the intake air amount QA increases more as the engine rotational speed NE is higher.
Next, a current post-correction intake air amount accumulation value SCQA is calculated by adding the calculated post-correction intake air amount CQA to the preceding value of the post-correction intake air amount accumulation value SCQA (=SCQA+CQA) (step 17). Next, it is determined whether or not the third timer value TMDLY3 is zero (step 18). The third predetermined time TMREF3 is substantially equivalent to a time required for the intake air amount to converge to a constant value after the start of throttling control for the intake air control valve 11, and is found, for example, by experiments. When the result of this determination is NO, this process is terminated.
On the other hand, when the result of the determination at step 18 is YES, indicating that the third predetermined time TMREF3 has elapsed after the start of the calculation of the post-correction intake air amount accumulation value SCQA, the post-correction intake air amount CQA at that time is set as a final value CQAF (step 19) on the assumption that the intake air amount has been converged. Next, an intake air changing amount SCQAR is calculated in accordance with the next Equation (1) using the calculated post-correction intake air amount accumulation value SCQA and the final value CQAF (step 20):
SCQAR=SCQA−(CQAF×N) (1)
where N is the number of times of accumulation in the post-correction intake air amount accumulation value SCQA, and is calculated by dividing the third predetermined time TMREF3 by a period at which this process is executed.
Next, it is determined whether or not the calculated intake air changing amount SCQAR is smaller than a predetermined threshold value QAREF (step 21). When the result of this determination is YES, an abnormality flag F_PCVNG is set to “0” (step 22), on the assumption that the plow-by gas feedback device 15 is normal, followed by the execution of the aforementioned step 24.
On the other hand, when the result of the determination at step 21 is NO, indicating SCQAR≧QAREF, the intake air changing amount is large, and the blow-by gas feedback device 15 is determined to be abnormal on the assumption that air can be flowing due to the blow-by gas passage 16 which has come off the intake pipe 4, or the like. Then, the abnormality flag F_PCVNG is set to “1” for indicating this fact (step 23), followed by the execution of the aforementioned step 24.
When the blow-by gas feedback device 15 is normal, the upstream intake air amount QA immediately decreases well in response as the throttling control is started for the intake air throttle valve 11, resulting in a smaller area of the region A, as shown in
As described above, according to this embodiment, the intake air amount at a location downstream of the joint 30 of the intake pipe 4 is forcedly changed to decrease by throttling controlling the intake air throttle valve 11 (step 8), and the intake air changing amount SCQAR is calculated based on the intake air amount QA subsequently detected by the air flow meter 22 at a location upstream of the joint 30 (step 20). Then, the intake air changing amount SCQAR is equal to or larger than the threshold value QAREF (NO at step 21), the blow-by gas feedback device 15 is determined to be abnormal, thus making it possible to appropriately determine the abnormality and improve the determination accuracy.
Also, when the intake air changing amount SCQAR is calculated based on the intake air amount QA, the intake air amount QA is corrected in accordance with the engine rotational speed NE, so that even if the engine rotational speed NE changes, the intake air amount QA can be calculated with reference to the reference rotational speed NEO, thereby further improving the accuracy of the abnormality determination.
Further, since the post-correction intake air amount accumulation value SCQA is calculated by accumulating the post-correction intake air amount CQA, it is possible to prevent erroneous determinations due to temporary fluctuations in the intake air amount QA, the influence of noise included in the detection signal of the intake air amount QA, and the like, to further improve the determination accuracy.
Also, since the intake air changing amount SCQAR is calculated by subtracting the product of the final value CQAF and the number of times N of accumulations from the post-correction intake air amount accumulation value SCQA, the abnormality determination can be made based on a net changing amount in accordance with the throttling control, thus further improving the accuracy of the abnormality determination.
Further, since the existing air flow meter 22, which is generally used for controlling the engine 3, is utilized as an intake air amount sensor for detecting the intake air amount QA, the abnormality determination can be made without adding a dedicated device for the abnormality determination.
Also, since the abnormality determination is executed under the condition that the engine 3 is in the fuel cut operation or in the cruising operation, its accuracy can be further improved by executing the abnormal determination only when the intake air amount is stable.
Further, since the EGR control valve 7b and the variable vane 8c are both controlled to close during the abnormality determination, the influence on the intake air amount due to their operations can be eliminated, thus making it possible to more appropriately perform the abnormality determination.
In this process, when the engine 3 is in a predetermined operating condition (YES at step 1), and when the valve close control flag F_EBC is not “1” (NO at step 2), the EGR control valve 7b and the variable vane 8c are controlled to close in a manner similar to the aforementioned step 3, and the intake air throttle valve 11 is also controlled once to a predetermined opening smaller than that for the normal control (valve closing operation). Then, when their valve closing control continues for the first predetermined time TMREF1 (YES at step 6), it is determined whether or not an opening control flag F_THO is “1” (step 41). When the result of this determination is NO, the intake air throttle valve 11 is controlled to a predetermined opening larger than that of the valve closing operation so far performed (hereinafter called the “opening control”), and the opening control flag F_THO is set to “1” (step 43), followed by the execution of the aforementioned step 10. In this way, the intake air amount is controlled to increase.
As the step 43 is executed, the result of the determination at step 41 is YES, in which case it is determined whether or not the second timer value TMDLY2 is zero (step 11). When the result of this determination is YES, the accumulation flag F_SCQA is “1” (step 12). When the result of this determination is NO, the accumulation flag F_SCQA is set to “1” (step 13), and a fourth timer value TMDLY4 is set to a fourth predetermined time TMREF4 (for example, 0.3 sec) significantly shorter than the third predetermined time TMREF3 (step 44). Then, the post-correction intake air amount accumulation value SCQA is calculated (steps 15-17). After the start of this calculation, when the fourth predetermined time TMREF4 has elapsed (YES at step 45), it is determined whether or not the calculated intake air amount SCQAR is larger than a predetermined threshold value QAREF (step 46).
When the result of this determination is YES, the abnormality flag F_PCVNG is se to “0” (step 22). On the other hand, when the result of the determination at step 46 is NO, indicating SCQAR≦QAREF, the intake air changing amount SCQAR is small, and the blow-by gas feedback device 15 is determined to be abnormal on the assumption that air can be flowing due to the blow-by gas passage 16 coming off the intake pipe 4. Then, the abnormality flag F_PCVNG is set to “1” for indicating this fact (step 23). At step 24 subsequent to step 22 or 23, after the EGR control valve 7b, the variable vane 8c, and the intake air throttle valve 11 are normally controlled, the valve closing flag F_EBC, the opening control flag F_THO, and the accumulation flag F_SCQA are all set to “0” (step 47), and the post-correction intake air amount accumulation value SCQA is reset to zero (step 26), followed by the termination of this process.
The post-correction intake air amount CQA abruptly rises immediately after the start of the opening control for the intake air throttle valve 11. When the blow-by gas feedback device 15 is normal, a rising amount is large as shown in
As described above, according to this embodiment, the intake air amount at a location downstream of the joint 30 of the intake pipe 4 is forcedly changed to increase by controlling the intake air throttle valve 11 to open (step 42), and when the intake air changing amount SCQAR indicative of the rising amount of the intake air amount QA, calculated based on the intake air amount QA detected immediately after the opening control, is equal to or smaller than the threshold value QAREF (NO at step 46), the blow-by gas feedback device 15 is determined to be abnormal. Accordingly, abnormalities of the blow-by gas feedback device 15 can be appropriately determined based on the rising amount immediately after the opening control for the intake air throttle valve 11, thus providing similar advantages to those of the first embodiment.
It should be understood that the present invention is not limited to the described embodiments, but can be practiced in a variety of manners. For example, while the intake air throttle valve 11 is used as an intake air amount controller for changing the intake air amount, for which the throttling control and opening control are performed in the first and second embodiments, respectively, another appropriate intake air amount controller may be used instead of or in addition to the intake air throttle valve. For example, the EGR amount may be increased/decreased by controlling the EGR control valve 7b of the EGR device 7, or the supercharge pressure may be increased/decreased by controlling the variable vane 8c of the supercharger 8. In this event, the intake air amount controller which is not used to change the intake air amount is preferably held in a predetermined operating condition so as not to affect the intake air amount, in a manner similar to the EGR control valve 7b and the variable vane 8c which are controlled to close in the embodiments.
Also, in the embodiments, the intake air amount is forcedly changed by the throttling control or the opening control for the intake air throttle valve. The present invention is not so limited, but the abnormality determination may be performed by capturing a timing at which the opening of the intake air throttle valve 11 changes to the accompaniment of a manipulation of a driver on an accelerator pedal.
Further, while the embodiments employ the accumulation value of the post-correction intake air amount CQA as a parameter for performing the abnormality determination, the present invention is not so limited, but may use the intake air amount QA or the post-correction intake air amount CQA detected at a predetermined timing after the start of the throttling control or the opening control for the intake air throttle valve 11. In the former case, the threshold value to be compared with the intake air amount QA is preferably set in accordance with the engine rotational speed NE.
Further, while the foregoing embodiment has shown an example in which the present invention is applied to a diesel engine, the present invention is not limited to this particular engine, but can be applied to a variety of engines other than the diesel engine, including an engine for vessel propeller such as an outboard engine which has a crank shaft arranged in the vertical direction. Otherwise, details in the configuration may be modified as appropriate without departing from the spirit and scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 238056/2006 | Sep 2006 | JP | national |
