Patent Application
20070251502
In
A fuel filler opening 3 is formed on fuel tank 1 to be opened, which is to be sealed by means of a filler cap 2.
To the inside of fuel tank 1, a motorized fuel pump 4 is disposed,
Fuel pump 4 is a turbine type pump, and a discharge port of fuel pump 4 is connected to one end of a fuel pipe 6a is.
A check valve 7 is a one-way valve for stopping the fuel flowing from fuel injection valves 9 to fuel pump 4, and the other end of fuel pipe 5a is connected to an inlet port of check valve 7.
An outlet port of check valve 7 is connected to one end of a fuel pipe 5b, and the other end of fuel pipe 5b is connected to a fuel gallery pipe 8.
Fuel pipe 5a, fuel pipe 5b and fuel gallery pipe 8 forms fuel piping connecting between fuel pump 4 and fuel injection valves 9.
To fuel gallery pipe 8, there are disposed connecting portions 8a of the number same as the number of cylinders along an extending direction of fuel gallery pipe 8, and fuel inlet ports of fuel injection valves 9 are respectively connected to connecting portions 8a.
With regard to each of fuel injection valves 9, when a magnetic attractive force is generated due to supply of electric excitation current to an electromagnetic coil, each valve body thereof having been urged toward a valve closing direction by a spring is inversely lifted up by the magnetic attractive force to perform injection.
Fuel injection valves 9 are respectively disposed to intake port portions of the respective cylinders of engine 10, to inject the fuel to the respective cylinders.
Further, there is disposed a relief pipe 12 which communicates the inside of fuel gallery pipe 8 with the inside of fuel tank 1, and a relief valve 13 is disposed on a halfway portion of relief pipe 12.
Relief valve 13 is a mechanical pressure governor, which is driven to open when a fuel pressure in fuel gallery pipe 8 exceeds a threshold to return the fuel in fuel gallery pipe 8 into fuel tank 1, to thereby prevent the fuel pressure in fuel gallery pipe 8 from being increased to exceed the threshold.
An electronic control unit 11 incorporating therein a microcomputer outputs an injection pulse signal to each fuel injection valve 9, to thereby control a fuel injection amount and injection timing of each fuel injection valve 9.
Further, electronic control unit 11 controls a duty of a pulse width modulation (PWM) signal for fuel pump 4, to thereby control a discharge amount of fuel pump 4.
The above duty is a manipulated variable for fuel pump 4 in the present embodiment.
Furthermore, electronic control unit 11 outputs an opening control signal to an electronically controlled throttle 27 for driving a throttle valve by a motor, to thereby control an intake air amount of engine 10.
Electronic control unit 11 inputs thereto detection signals that are delivered from various sensors.
With regard to the various sensors, there are disposed an air flow meter 21 capable of detecting an intake air flow amount of engine 10, a crank angle sensor 22 capable of outputting a signal at each reference crank angle position, a water temperature sensor 23 capable of detecting the cooling water temperature Tw of engine 10, a pressure sensor 24 capable of detecting the fuel pressure in fuel gallery pipe 8, a fuel temperature sensor 25 capable of detecting the temperature of the fuel in fuel gallery pipe 8, an air-fuel ratio sensor 26 capable of detecting an air-fuel ratio based on oxygen concentration in exhaust gas of engine 10, and the like.
Then, electronic control unit 11 calculates injection pulse width, based on the detection signals detected from air flow meter 21, crank angle sensor 22, water temperature sensor 23, air-fuel ratio sensor 26 and the like. Further, since the injection amount per unit opening time of fuel injection valve 9 is changed depending on the fuel pressure in fuel gallery pipe 8, electronic control unit 11 adjusts the injection pulse width based on the fuel pressure at the time.
Further, electronic control unit 11 calculates the duty of the PWM signal for fuel pump 4, so that the fuel pressure detected by pressure sensor 24 approaches a target pressure. The target pressure is set at 350 kPa for example.
Furthermore, electronic control unit 11 has a function of determining whether pressure sensor 24 is in a normal operation state or in an abnormal operation state. Thus, when pressure sensor 24 is determined to be in the abnormal state, electronic control unit 11 executes controlling of fuel pump 4 without using the detection result by pressure sensor 24.
A flowchart of
In the flowchart of
The determination of the normality/abnormality of pressure sensor 24 is performed based on whether or not a sensor output is within a normal range, as described later. However, the determining method thereof is not restricted thereto and known various types of determining methods can be used.
And then, if pressure sensor 24 is in the normal state, the routine proceeds to step S102, where the duty of the PWM signal for fuel pump 4 is calculated based on the deviation between the pressure detected by pressure sensor 24 and the target pressure.
In the next step S103, the injection pulse width of fuel injection valve 9 is calculated based on the fuel pressure detected by pressure sensor 24, to thereby control fuel injection valve 9 based on the calculated injection pulse width.
On the other hand, when it is determined in step S101 that pressure sensor 24 is in the abnormal operation state, if fuel pump 4 and fuel injection valve 9 are controlled based on the detection result of pressure sensor 24, the fuel pressure cannot be controlled at the target pressure, and also, the fuel of required amount cannot be injected from fuel injection valve 9.
Therefore, when it is determined that pressure sensor 24 is in the abnormal operation state, the routine proceeds to step S104, where a feedback control of fuel pump 4 using the detection result of pressure sensor 24 is inhibited and the duty of the PWM signal for fuel pump 4 is fixedly maintained at 100%.
If the duty is fixedly maintained at 100%, fuel pump 4 is controlled to discharge the fuel of maximum discharge amount, and therefore, the fuel pressure in fuel gallery pipe 8 is increased.
However, when the fuel pressure exceeds a valve-opening pressure (for example 810 kPa) in relief valve 13, since relief valve 13 is opened to return the fuel into fuel tank 1, the pressure in fuel gallery pipe 8 is held in the vicinity of the valve-opening pressure.
Namely, in the state where the duty is fixedly maintained at 100%, the fuel pressure in fuel gallery pipe 8 can be estimated to be in the vicinity of the valve-opening pressure.
Therefore, in the next step S105, it is assumed that the fuel pressure in fuel gallery pipe 8 is held in the vicinity of the valve-opening pressure, and the injection pulse width is set so that a required fuel amount can be injected under such a pressure condition.
Namely, the valve-opening pressure is previously stored and the injection pulse width is set based on the stored valve-opening pressure.
According to the above described control, it is possible to increase the fuel pressure in fuel gallery pipe 8 up to the vicinity of the valve-opening pressure to hold it without being influenced by the fuel pressure at the time when pressure sensor 24 is failed.
Further, fuel injection valve 9 injects the fuel with the injection pulse width corresponding to the valve-opening pressure, so that the required fuel amount of engine 10 can be injected at a high accuracy.
Thus, even if pressure sensor 24 is failed, it is possible to control the fuel pressure at a given value to thereby determine the fuel injection pulse width, so that the required fuel amount of engine 10 can be injected from fuel injection valve 9.
Furthermore, since the pressure in fuel gallery pipe 8 is made higher, the generation of fuel vapor can be reduced, and the required fuel amount can be stably injected even in a high load region of engine 10.
A flowchart of
In the flowchart of
If pressure sensor 24 is in the normal operation state, the routine proceeds to step S202, where the duty of the PWM signal for fuel pump 4 is normally feedback controlled based on the deviation between the fuel pressure detected by pressure sensor 24 and the target pressure.
The above target pressure is set at 350 kPa for example.
On the contrary, when pressure sensor 24 falls in the abnormal operation state, the routine proceeds to step S203, where the duty of the PWM signal for fuel pump 4 is fixedly maintained at a reference duty beforehand stored in electric control unit 11.
The reference duty is that capable of obtaining a rotating force corresponding to the target pressure in the feedback control, and 0%<reference duty<100%.
Further, in the state where the duty is fixedly maintained at the reference duty, it is assumed that the fuel pressure is controlled at the target pressure in the feedback control in step S202, and the injection pulse width is calculated.
In the case where the duty is fixedly maintained at the reference duty, the fuel pressure cannot be high accurately controlled to become the target pressure, and further, there is such a possibility that a large pressure error occurs due to the lack of discharge amount particularly in a high load and high rotation region. However, it is attempted to increase the fuel pressure in the vicinity of the target pressure to hold it, and therefore, it is possible to ensure the necessary and sufficient driving performance as the driving performance for when pressure sensor 24 is in the abnormal state.
Incidentally, if the reference duty is adjusted depending on a change in the temperature of fuel at the moment of time, a more highly accurate control of the fuel pressure can be achieved with certainty.
In the case where the control duty for fuel pump 4 is fixedly maintained at the reference duty, if the engine operation continues to be performed in the high load and high rotation region where a required fuel flow amount is large, since the discharge amount of fuel pump 4 is smaller than the required fuel flow amount, sometimes, the fuel pressure is significantly lower than the target pressure.
In this case, if the injection pulse width is determined on the assumption that the fuel pressure reaches the target pressure, the fuel amount actually injected becomes smaller than the required fuel amount, resulting in that the air-fuel ratio becomes leaner.
Therefore, in the following, in the case where pressure sensor 24 is failed and the duty of the PWM signal is fixedly maintained at the reference duty, an engine control for preventing the air-fuel ratio from becoming leaner will be described in accordance with a flowchart of
The engine control shown in the flowchart of
The flowchart of
Here, it is possible to obtain the required fuel flow amount of engine 10 based on both the required fuel injection amount in fuel injection valve 9 and the engine rotating speed, and therefore, it is determined whether or not the control duty for fuel pump 4 is necessary and sufficient for the required fuel flow amount.
And then, if the fuel amount is not insufficient, the routine proceeds to step S212, where engine 10 is normally operated.
On the other hand, if the fuel amount is insufficient, the routine proceeds to step S213, where the fuel injection by fuel injection valve 9 is forcibly stopped.
Namely, the operation of engine 10 is inhibited in the high load and high rotation region where the fuel amount is insufficient, and engine 10 is operated only in a low load and low rotation region where the fuel amount is sufficient.
Accordingly, engine 10 is not operated in the region where the fuel pressure is lowered due to the lack of discharge amount of fuel pump 4 and accordingly the required fuel amount cannot be injected, and therefore, the operation in a lean air-fuel ratio can be avoided.
A flowchart of
The flowchart of
And then, if the fuel amount is not insufficient, the routine proceeds to step S222, where the engine is normally operated without any restriction.
On the other hand, if the fuel amount is insufficient, the routine proceeds to step S223, where it is determined whether or not the target opening TVO of electronically controlled throttle 27 exceeds an upper limit value MAX.
In the case where the target opening TVO of electronically controlled throttle 27 exceeds the upper limit value MAX, the routine proceeds to step S224, where the upper limit value MAX is set at the target opening TVO.
Therefore, it is avoided that the throttle opening is controlled to exceed the upper limit value MAX.
On the other hand, if the target opening TVO of electronically controlled throttle 27 is equal to or less than the upper limit value MAX, the routine bypasses step S224 so as not to limit the target opening TVO.
By limiting the target opening TVO of electronically controlled throttle 27 to the upper limit value MAX or less, the intake air amount of engine 10 is limited, and therefore, a maximum value of the required injection amount becomes smaller.
As a result, it is possible to prevent the operation of engine 10 in the region where the discharge amount of fuel pump 4 is insufficient.
Accordingly, as described in the above, by restricting the throttle opening, it is possible to avoid the operation of engine 10 in the lean air-fuel ratio.
A flowchart of
In the flowchart of
And then, if pressure sensor 24 is in the normal state, the routine proceeds to step S302, where the discharge amount of fuel pump 24 is feedback controlled based on the deviation between the fuel pressure detected by pressure sensor 24 and the target pressure.
In next step S303, the injection pulse width of fuel injection valve 9 is calculated based on the fuel pressure detected by pressure sensor 24, thereby driving to control fuel injection valve 9 based on the calculated injection pulse width.
On the other hand, if it is determined in step S301 that pressure sensor 24 is in the abnormal state, the routine proceeds to step S304.
In step S304, it is determined whether or not the required fuel flow amount of engine 10 is equal to or less than a predetermined amount, based on both the required fuel injection amount of fuel injection valve 9 and the engine rotating speed.
And then, if the required flow amount of fuel in engine 10 is equal to or less than the predetermined amount, the routine proceeds to step S305. Incidentally, in the case where engine 10 is operated in the low load and low rotation region, since the required fuel flow amount of engine 10 is equal to or less than the predetermined amount, it is possible to determine in step S304 whether or not engine 10 is operated in a predetermined low load and low rotation region.
In step S305, the duty of the PWM signal for fuel pump 4 is fixedly maintained a reference duty beforehand stored in electric control unit 11.
The reference duty, similar to step S203, is that capable of obtaining a rotating force corresponding to the target pressure (350 kPa) in the feedback control in step S202 in a reference operating state of engine 10.
In next step S306, it is assumed that the actual pressure reaches the target pressure, and the injection pulse width of fuel injection valve 9 is normally calculated.
On the other hand, in the case where engine 10 is operated in the high load and high rotation region and the required fuel flow amount of engine 10 exceeds the predetermined amount, the routine proceeds to step S307.
In step 8307, the duty of the PWM signal for fuel pump 4 is fixedly maintained at 100%.
In next step S308, it is assumed that the fuel pressure in fuel gallery pipe 8 is held at the valve-opening pressure of relief valve 13, and the injection pulse width is set so that the required fuel amount can be injection under such a pressure condition.
According to the above embodiment, since fuel pump 4 is driven by the reference duty in the low load and low rotation region of engine 10, it is possible to prevent engine 10 from being operated under the condition that the discharge amount of fuel pump 4 is insufficient for the required fuel flow amount, while suppressing the power consumption in fuel pump 4.
Further, it is possible to maintain the measuring accuracy in the region where the fuel injection amount is small, by restricting the fuel pressure to be lower in the low load and low rotation region.
On the other hand, since the control duty for fuel pump 4 is fixedly maintained at 100% in the high load and high rotation region where the required fuel flow amount of engine 10 is large, it is possible to ensure the discharge amount exceeding the required fuel flow amount in the high load and high rotation region, to thereby operate engine 10 in the whole operating region.
Incidentally, the starting time of engine 10 operation can be added as a condition for fixedly maintaining the duty at 100%.
A flowchart of
In step S511, the fuel pressure P detected by pressure sensor 24 is read in.
In step S512, it is determined whether a starter switch for engine 10 is turned ON or OFF.
And then, when the operation of engine 10 has been started (starter switch was turned OFF), the routine proceeds to step S513, where it is determined whether or not the fuel pressure read in step S511 is equal to or larger than a threshold SL1.
The threshold SL1 is previously stored as a value below which the detection result of fuel pressure sensor 24 is not lowered when fuel pressure sensor 24 is in the normal state.
Here, when the fuel pressure P read in step S511 is less than the threshold SL1, the routine proceeds to step S514, where it is determined whether or not a state where the fuel pressure P is less than the threshold SL1 continues for over a predetermined period of time.
And then, in the case where the fuel pressure P is less than the threshold SL1 for over the predetermined period of time, the routine proceeds to step S517, where it is determined that fuel pressure sensor 24 is in the abnormal state.
On the other hand, in the case where, even in the state where the fuel pressure P is less than the threshold SL1, duration of such a state does not reach the predetermined period of time, step S517 is bypassed and the present routine is terminated.
Further, when it is determined in step S513 that the fuel pressure P is equal to or larger than the threshold SL1, the routine proceeds to step S515.
In step S515, it is determined whether or not the fuel pressure P read in step S511 is equal to or less than a threshold SL2.
The threshold S2 is previously stored as a value over which the detection result of fuel pressure sensor 24 does not exceed when fuel pressure sensor 24 is in the normal state, and the threshold SL1 c the threshold SL2.
When it is determined in step S515 that the fuel pressure P is less than the threshold SL2, since the fuel pressure P is within a normal range between the threshold SL1 and the threshold SL2, it is determined that fuel pressure sensor 24 is in the normal state, and the present routine is terminated.
On the other hand, when it is determined in step S515 that the fuel pressure P is equal to or larger than the threshold SL2, the routine proceeds to step S516, where it is determined whether or not a state where the fuel pressure P is equal to or larger than the threshold SL2 continues for over a predetermined period of time.
And then, in the case where the fuel pressure P is equal to or larger than the threshold SL2 for over the predetermined period of time, the routine proceeds to step S517, where it is determined that fuel pressure sensor 24 is in the abnormal state.
On the other hand, in the case where, even in the state where the fuel pressure P is equal to or larger than the threshold SL2, duration of such a state does not reach the predetermined period of time, step S517 is bypassed and the present routine is terminated.
It should be appreciated that the entire contents of Japanese Patent Application No. 2006-124798 filed on Apr. 28, 2006, a priority of which is claimed, are incorporated herein by reference.
While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims.
Furthermore, the foregoing description of the embodiments according to the present invention is provided for illustration only, and not for the purpose of limiting the invention as defined in the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-124798 | Apr 2006 | JP | national |
