JP2874074B2 - Fuel pump driving method for internal combustion engine using blended fuel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a fuel pump of an internal combustion engine which can be operated using either one of two types of fuels having different properties or a blended fuel obtained by mixing them. The present invention relates to a fuel pump driving method capable of improving engine startability when restarting an engine once stopped immediately after a sudden change in a blend ratio.

[0002]

BACKGROUND OF THE INVENTION It is known to use alternative fuels to vehicles to replace gasoline in order to cope with the exhaustion of vehicle fuel or to improve the exhaust gas characteristics of internal combustion engines. As an alternative fuel, for example, a blended fuel obtained by mixing gasoline and methanol is known. In a vehicle using a blended fuel, a blending rate sensor for detecting a blending rate of gasoline and methanol in the blended fuel is provided in a fuel piping system, and fuel supply control is performed in accordance with the blending rate detected by the sensor. I have to.

[0003]

However, there is a time lag in the fuel supply between the blend ratio sensor disposed in the fuel piping system and the fuel supply device disposed downstream of the sensor in the fuel piping system. Therefore, when blended fuels of various blending rates are used in the internal combustion engine, the blending rates of the blended fuel near the blending rate sensor and the blended fuel actually supplied to the engine from the fuel supply device are not necessarily the same. is not.

[0004] For example, if the engine is operated only for a short period of time from the time when the blended fuel having a different blending ratio from the remaining blended fuel in the fuel tank is supplied to the fuel tank, and then the driving of the fuel pump is stopped simultaneously with stopping the engine, the fuel In the piping system, the upstream section from the fuel tank to the blend ratio sensor is filled with a newly refueled new blend fuel, while the downstream section from the blend rate sensor to the fuel supply device is the old blend that was refueled last time. Will be filled with fuel. When the engine is restarted in such a state, for example, the engine start control is performed based on the blend ratio of the new blend fuel detected at the time of the previous engine stop, while the old blend fuel is actually It is supplied to the engine from the supply device. As a result, the engine start control may be improper, and the engine may not be started smoothly.

For example, a blended fuel having a methanol mixing ratio of zero and a stoichiometric air-fuel ratio of 14.7, ie, gasoline, is newly supplied and the blending ratio sensor detects that the blending ratio is zero. When a blended fuel having a mixing ratio of 85% and a stoichiometric air-fuel ratio of about 7 is actually supplied to the engine, the amount of the blended fuel supplied at the time of starting the engine becomes too small, which hinders the engine starting. Will be.

It is an object of the present invention to provide a method for driving a fuel pump of an internal combustion engine using a blended fuel, which can improve the engine startability when restarting an engine once stopped immediately after a sudden change in the blending ratio. Aim.

[0007]

In order to achieve this object, a blended fuel is pumped to a fuel supply device by a fuel pump, and the fuel supply device is supplied in accordance with a blend ratio detected by a blend ratio sensor disposed in a fuel piping system. In the internal combustion engine using the blended fuel for controlling the driving of the fuel pump, the fuel pump driving method according to the present invention is configured such that when the detected blending ratio changes more than a predetermined change height, the engine operation is performed within a predetermined time from the time when the blending ratio changes. Is stopped, the driving of the fuel pump is continued for at least a predetermined time from the time when the blending ratio changes.

[0008]

The fuel supply control is performed according to the blend ratio detected by the blend ratio sensor during the pressure feeding of the blend fuel to the fuel supply device. When the blend ratio detected by the blend ratio sensor changes more than a predetermined change height, it is determined whether or not the engine operation has been stopped within a predetermined time from the time when the blend ratio has changed. Is stopped, the fuel pump is continuously driven. This fuel pump drive is continued for at least a predetermined time from the blending change point, whereby the downstream side of the fuel piping system from the blending rate sensor to the fuel supply device is filled with the blended fuel which is the latest blending rate detection target. . as a result,
The blend ratio of the blend fuel actually supplied from the fuel supply device to the engine at the next engine start is the same as the blend ratio detected by the blend ratio sensor,
Fuel supply control based on the detected blend rate is performed properly,
Thus, there is no hindrance to starting the engine.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a vehicle using a blended fuel includes a fuel tank 1 for storing the blended fuel and a fuel tank 1 connected to the fuel tank 1 via a fuel piping system 3 to supply the blended fuel to an engine (not shown). A fuel injection device 2 for supplying the fuel, and the fuel injection device 2 has a plurality of injectors 2a corresponding to each cylinder of the engine. The blended fuel is obtained, for example, by mixing gasoline and methanol, and contains, for example, 0% to 85% of methanol. A fuel pump 4 for pumping the blended fuel from the fuel tank 1 to the fuel injection device 2, a blending rate sensor 5 for detecting a blending rate of gasoline and methanol in the blended fuel, A pressure regulating valve 6 for adjusting the fuel pressure so that the fuel pressure falls within a predetermined pressure range is provided. The fuel pump 4 is, for example, an electromagnetic plunger pump that can operate independently of the engine. The operating power to the fuel pump 4 and the blend rate sensor 5 is supplied from a battery (not shown) via an opening / closing circuit (not shown) that can be turned on and off independently of the on / off state of the ignition key. , The pump 4 and the sensor 5 are driven independently of turning on / off the ignition key and stopped.

Further, the controller 10 is provided in the internal combustion engine.
The controller 10 determines a vehicle operating state based on the blend ratio sensor 5 and sensor outputs from various sensors including a throttle opening sensor (not shown), an accelerator opening sensor, an intake air amount sensor, an engine water temperature sensor, and the like. In addition, various vehicle operation controls are performed. In particular, in connection with the present invention, under the control of the controller 10, the fuel injection device 2 and the ignition timing adjustment device are adjusted so as to achieve a fuel injection amount, ignition timing, and the like that match the blend ratio detected by the blend ratio sensor 5. 7 is driven so that the fuel pump 4
Is operated, and the operation of an opening / closing circuit related to the supply of the operating power to the pump 4 and the sensor 5 is controlled so that the operating power is supplied to and cut off from the pump 4 and the sensor 5. In order to perform various vehicle operation controls including fuel pump control, the controller 10 includes a processor having functions of calculation and discrimination, a memory for storing data, and various peripheral elements including a timer 11 used for fuel pump control and a controller. And an input / output circuit for transmitting and receiving signals to and from the terminal. The aforementioned memory includes a battery backup memory that does not lose its stored contents after the engine is stopped.

Hereinafter, the drive control of the fuel pump and the blend ratio sensor in the fuel pump drive method according to one embodiment of the present invention applied to the internal combustion engine having the above configuration will be described with reference to FIGS. The drive control of the fuel pump and the blend ratio sensor is executed by the controller 10 in parallel with other various engine controls after the ignition key is turned on.

When the ignition key is turned on, the supply of operating power to the fuel pump 4 and the blend rate sensor 5 is started, and the operation of the pump 4 and the sensor 5 is started (step S1). As a result, the blended fuel is supplied from the fuel tank 1 to the fuel supply device 2 by the fuel pump 4, and the blending rate of the blended fuel in the vicinity thereof is detected by the blending rate sensor 5.

In each cycle of the drive control of the fuel pump and the blend ratio sensor, the controller 10 reads the blend ratio detected in the previous cycle from the memory of the controller 10 and outputs the blend ratio from the blend ratio sensor 5 representing the blend ratio in the current cycle. The output is read, and the blend ratio change amount in the current cycle is calculated based on the blend ratio detected in the previous cycle and the current cycle (step S).
2) Further, the current blend ratio is stored in the memory so as to be used for calculating the blend ratio change height in the next cycle (step S3).

Next, the controller 10 determines whether or not the blending rate has changed suddenly by determining whether or not the blending rate change amount in the current cycle is equal to or greater than a predetermined change amount (step S4). If it is determined in step S4 that the blending ratio has not suddenly changed, the controller 10 refers to the storage contents of the related ones of the registers built in the controller, and the index i is measuring the elapsed time from the time when the blending ratio suddenly changes. It is further determined whether or not the value is “1” indicating the presence (step S5). If the index i is not the value "1", it is further determined whether or not the ignition key is turned off (step S6), and if not, the current fuel pump control cycle is ended. As a result, as long as the ignition key is on and the blend ratio does not change suddenly, the operation of the fuel pump 4 and the blend ratio detection by the blend ratio sensor 5 started simultaneously with the ignition key on are continued.

On the other hand, if it is determined in step S6 that the ignition key has been turned off while the elapsed time from the point of sudden change in the blend ratio has not been counted, the controller 10
Under the above control, the supply of the operating power to the fuel pump 4 and the blend rate sensor 5 is stopped (step S7), whereby the fuel pump control of FIGS. 2 and 3 ends. While the same type of blended fuel is used, the blending rate does not usually change suddenly. Therefore, as described above, the operating power is supplied to the fuel pump 4 and the blending rate sensor 5 according to the turning on and off of the ignition key. Supply and cut off.

On the other hand, if a blended fuel of a different type from the remaining blended fuel in the fuel tank 1 is supplied, the blending rate may suddenly change while the vehicle is running or when the vehicle starts and stops. Then, when restarting the engine once stopped immediately after the sudden change of the blending ratio, a poor engine start may be caused for the above-mentioned reason. Hereinafter, the fuel pump control according to the present embodiment when the blend ratio changes suddenly will be described.

A series of steps S1 to S6 are repeatedly executed to detect a sudden change in the blending ratio while driving the fuel pump 4 while detecting the blending ratio by the blending ratio sensor 5. When the determination is made in S4, the controller 10 restarts the timer 11 and counts the elapsed time from the point of time when the blending rate suddenly changes.
1 is counted (step S8). When the timer is restarted, it takes longer than the time required for the blended fuel near the blending rate sensor 5 of the fuel piping system 3 to be pumped by the fuel pump 4 and reach the most downstream injector under the control of the controller 10. A slightly longer predetermined timer time is set in the timer 11. The predetermined timer time is predetermined according to the length of the pipe from the blend rate sensor 5 to the most downstream injector and the discharge force of the fuel pump 4, and is stored in the memory of the controller 10.

In step S9, the controller 10
Sets the index i to a value "1" indicating that the elapsed time from the point of sudden change in the blending ratio is being counted, and then determines whether the timer 11 has expired (step S10). Here, since the timer 11 has just been restarted, the determination result in step S10 is negative. In this case, the controller 10 further determines whether or not the ignition key is turned off and the operation of the engine is stopped (step S11). If the engine has not been stopped, the current control cycle is ended, whereby the fuel pump 4 is continuously driven. After that, when the predetermined timer time elapses without stopping the engine, the controller 10 sets the index i to a value “0” indicating that the elapsed time from the time of the sudden change of the blending ratio is not counted (step S12). Then, it is determined whether or not the ignition key has been turned off (step S13). If the determination result is negative, the above-mentioned step S2 and subsequent steps are repeatedly executed in the next control cycle and thereafter.

As described above, as long as the ignition key is in the ON state and the engine operation is continued, even if the blending ratio suddenly changes during the engine operation, the fuel pump drive and the blending operation started simultaneously with the ignition key ON are started. Rate detection continues. For a short time from the time when the sudden change in the blending rate is detected, a state occurs in which the blending rate detected by the blending rate sensor 5 and the blending rate of the blended fuel actually supplied from the fuel injection device 2 to the engine are different. Indeed, the control of the fuel injection amount and the control of the ignition timing by the controller 10 based on the detected blend ratio are indeed inappropriate. However, since the ignition key is in the ON state and the engine operation is continued, and the time during which the inappropriate control is performed is short, there is no hindrance to the engine operation.

If the ignition key is turned off after the elapse of a predetermined timer time from the time when the blend ratio suddenly changes during the operation of the engine, the process proceeds to step S7.
Under the control of the controller 10, the operation power supply to the fuel pump 4 and the blend rate sensor 5 is cut off at the same time as the ignition key is turned off.
Is stopped.

Now, after supplying a blended fuel having a different blending ratio from the remaining blended fuel in the fuel tank 1, the engine may be operated for a short time and then stopped. In this case, as shown in FIG.
The upstream section leading to is, for example, a methanol mixing rate of 0%
, While the downstream section from the sensor 5 to the fuel injection device 2 is filled with the old blended fuel M85 having, for example, a methanol mixing ratio of 85%. When an attempt is made to start the engine in such a state, the engine start control is performed in response to the new blended fuel detected by the sensor 5 immediately before the last stop of the engine operation, even though the old blended fuel M85 is injected and supplied from the fuel injection device 2 to the engine. This is performed based on the blending ratio of the blended fuel M0 of 0%, and therefore, the fuel injection amount may be too small to cause difficulty in starting the engine.

The state shown in FIG. 4 is caused by stopping the operation of the engine before a predetermined timer time has elapsed from the time when the sudden change in the blending ratio is detected in step S4 in FIG. The stop of the engine before the elapse of the predetermined timer time is detected when the determination result in step S10 is negative and the determination result in step S11 is positive. In this case, the controller 10 keeps the switching circuit related to the supply of the operating power to both the elements 4 and 5 closed so as to continue the supply of the operating power to the fuel pump 4 and the blend rate sensor 5, whereby the pump 4 Then, the driving of the sensor 5 is continued (step S14), and after the next control cycle, steps S2 and subsequent steps are executed. Then, after the predetermined timer time has elapsed from the point of time when the blending rate suddenly changes, the drive of the pump 4 and the sensor 5 is stopped (step S).
7). As described above, the drive of the pump 4 and the sensor 5 is continued until the predetermined timer time elapses from the point of the sudden change of the blending ratio, so that the fuel piping system from the blending ratio sensor 5 to the fuel injection device 2 as shown in FIG. The downstream section 3 is filled with a new blend fuel, such as the blend fuel M0, which is the latest blend rate detection target. As a result, when the engine is restarted, the blending ratio of the blended fuel actually supplied from the fuel injection device 2 to the engine, for example, 0%, becomes the same as the blending ratio, for example, 0%, detected by the sensor 5, and is based on the detected blending ratio. The fuel injection control is properly performed, so that the starting of the engine is not hindered.

As apparent from FIGS. 2 and 3, while the driving of the fuel pump 4 and the blend ratio sensor 5 is continued after the sudden change of the blend ratio, if the blend ratio suddenly changes again, the timer 11 is restarted. As a result, the pump 4 is switched for a predetermined time from the point of sudden change of the blend ratio.
And the driving of the sensor 5 is continued. In order to clarify the purpose of the fuel pump / blend rate sensor control of the present embodiment, an engine stop determination step S11 and a pump / sensor drive continuation step S14 are provided, but both steps can be omitted. The method of this embodiment is particularly suitable for a side feed injector in which the fuel amount in the injector is small.

[0024]

As described above, the blend fuel is pumped to the fuel supply device by the fuel pump, and the drive of the fuel supply device is controlled in accordance with the blend ratio detected by the blend ratio sensor disposed in the fuel piping system. In an internal combustion engine using fuel, the fuel pump driving method according to the present invention is configured such that when the detected blending ratio changes more than a predetermined change height, the engine operation is stopped within a predetermined time from the time when the blending ratio changes. Also, since the driving of the fuel pump is continued for at least a predetermined time from the time when the blending ratio changes, the engine startability when restarting the engine once stopped immediately after the blending ratio suddenly changes can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a main part of a vehicle using a blended fuel.

FIG. 2 is a flowchart showing a part of a control procedure for driving a fuel pump and a blend ratio sensor in a fuel pump driving method according to an embodiment of the present invention.

FIG. 3 is a flowchart showing the rest of the control procedure for driving the fuel pump and the blend ratio sensor.

FIG. 4 is a schematic diagram showing a state in which an upstream section and a downstream section of a fuel piping system are filled with different blended fuels.

FIG. 5 is a schematic diagram showing a state in which an upstream section and a downstream section of a fuel piping system are filled with the same blended fuel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Fuel injection device 3 Fuel piping system 4 Fuel pump 5 Blend rate sensor 6 Pressure regulating valve 7 Ignition timing adjustment device 10 Controller 11 Timer

Claims (2)

(57) [Claims] An internal combustion system using a blended fuel, wherein the blended fuel is pressure-fed to a fuel supply device by a fuel pump and the driving of the fuel supply device is controlled in accordance with a blending ratio detected by a blending ratio sensor disposed in a fuel piping system. In the engine, when the detected blend ratio changes more than the predetermined change height, the engine operation is stopped within a predetermined time from the blend ratio change point, and the engine is stopped for at least the predetermined time from the blend ratio change point. Characterized by continuing to drive the fuel pump,
A method for driving a fuel pump of an internal combustion engine using a blended fuel. 2. The blend ratio sensor continues to detect the blend ratio while the driving of the fuel pump is continued after the blend ratio change point, and when the blend ratio changes again more than the predetermined change height, the blending is stopped. 2. The fuel pump driving method for an internal combustion engine using a blended fuel according to claim 1, wherein the driving of the fuel pump is continued for the predetermined time from a point in time at which the rate changes again.