Throttle opening control device, motorcycle, and method for producing control map

A throttle opening control device for a vehicle having an engine with an electronically controlled throttle valve and an accelerator operated by a rider is provided. The throttle opening control device includes an accelerator opening acquisition module for acquiring an opening of the accelerator, an engine rotation speed acquisition module for acquiring a rotation speed of the engine, and a throttle opening control module for controlling an opening of the throttle valve based on the opening of the accelerator and the rotation speed of the engine. The throttle opening control module is configured to limit the opening of the throttle valve when the rotation speed of the engine is lower than a pre-determined idle rotation speed to prevent reverse rotation of the engine.

PRIORITY INFORMATION

This patent application is based on and claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2008-067042, filed on Mar. 17, 2008, the entire contents of which is hereby expressly incorporated by reference.

TECHNICAL FIELD

The present invention relates to a throttle opening control system, engine control unit, motorcycle, and method for producing a control map, and in particular to control means for preventing the reverse rotation of an engine.

BACKGROUND

It has been known that in an engine mounted in a motorcycle or the like, if the gas pressure in a combustion chamber increases when an engine rotation speed decreases to a speed lower than an idle rotation speed, there is a possibility that the engine will be reversely rotated.

Japanese Unexamined Patent Application Publication No. 2006-207565 discloses an engine ignition control device for preventing the reverse rotation of the engine by forcibly making the engine misfire when the revolution speed of the engine becomes lower than a threshold value determined according to a present engine load. However, it would be preferable to prevent the gas pressure itself in the combustion chamber from increasing than to forcibly make the engine misfire, because useless fuel consumption is decreased.

SUMMARY

The present invention has been made in view of the above-mentioned circumstances. One object of the present invention is to provide a method for producing a control map that can prevent the occurrence of a reverse rotation of an engine. Other objects of the present invention include the provision of a throttle opening control device implementing the same as well as a motorcycle equipped with such a throttle opening control device.

To this end, in one aspect, a throttle opening control device includes an accelerator opening acquisition module for acquiring an opening of an accelerator operated by a rider of a vehicle, an engine rotation speed acquisition module for acquiring a rotation speed of an engine mounted in the vehicle, and a throttle opening control module for controlling the opening of a throttle valve of the engine on the basis of the opening of the accelerator and the rotation speed of the engine. The throttle control device is further characterized in that the throttle opening control module limits the opening of the throttle valve when the rotation speed of the engine is lower than a pre-determined idle rotation speed to prevent reverse rotation of the engine.

Moreover, a motorcycle of the present invention is provided with the above-mentioned throttle opening control device.

Further, a method for producing a control map according to another aspect of the present invention relates an opening of the accelerator operated by a rider of a vehicle and the rotation speed of the engine to an opening of the throttle valve of the engine. The control map is stored in a throttle opening control device for controlling a throttle-valve of an engine. The method is characterized in that the control map is produced on the basis of determining whether reverse rotation of the engine will occur when the opening of the throttle valve is increased in a state where the rotation speed of the engine is lower than a pre-determined idle rotation speed.

According to the present invention, the opening of the throttle is limited when the rotation speed of the engine is lower than the predetermined idle rotation speed. With this setup, an increase in the gas pressure in the combustion chamber of the engine can be prevented. As a result, it is possible to prevent the occurrence of a reverse rotation of the engine.

DETAILED DESCRIPTION

FIG. 1is a side view of a motorcycle1according to an embodiment of the present invention. As shown in the drawing, in the motorcycle1, an engine6is suspended by a main frame8extending rearward and downward from a head pipe that steerably supports a front fork2. The power of the engine6is transmitted to a rear wheel4by a chain. The front fork2rotatably supports a front wheel3and has a steering handlebar9fitted on its top. The steering handlebar9has an accelerator grip5fitted to its right end portion. A rider varies the direction of the front wheel3by the use of the steering handlebar9and can adjust the output of the engine6by twisting the accelerator grip5.

FIG. 2is a block diagram of an exemplary throttle opening control system10mounted in the motorcycle1. As shown in the drawing, the throttle opening control system10includes an engine control unit (ECU)7as a throttle opening control device according to an embodiment of the present invention. ECU7comprises one or more microprocessors, and executes a control program, preferably, stored in ROM (Read-Only Memory) to realize a throttle opening control according to this embodiment.

The motorcycle1is provided with an accelerator opening sensor11for detecting the state of operation (degree of twist) of the accelerator grip5, that is, the degree of accelerator opening, a throttle opening sensor12for detecting the degree of opening (throttle opening) of a throttle valve (electronically controlled throttle61to be described later) of the engine6, a water temperature sensor13for detecting the temperature of cooling water of the engine6, an atmospheric pressure sensor14for detecting the atmospheric pressure, a vehicle speed sensor15for detecting the running speed of the motorcycle1, and a crank pulse sensor16for detecting a crank pulse outputted in response to the revolution of a crankshaft of the engine6. Detection results (outputs) from these detection sensors are inputted to the ECU7, as schematically depicted in reference toFIG. 2.

Moreover, the engine6of the motorcycle1is provided with electronically controlled throttle61, and the ECU7supplies the electronically controlled throttle61with a control signal on the basis of the detection results by the above-mentioned various detection devices. This electronically controlled throttle61is a throttle valve that can have its opening freely controlled by a DC motor according to the control signal input from the ECU7.

FIG. 3is a block diagram illustrating the construction of one embodiment of an ECU7. The ECU7functionally has an accelerator opening acquisition module71, an engine rotation speed acquisition module72, a throttle opening control module73, and a map memory74. The accelerator opening acquisition module71acquires an accelerator opening on the basis of the detection signal from the accelerator opening sensor11and outputs the accelerator opening to the throttle opening control module73. The engine rotation speed acquisition module72determines the rotation speed (the number of revolutions per unit time) of the engine6on the basis of the detection signal from the crank pulse sensor16and outputs the rotation speed of the engine6to the throttle opening control module73.

The throttle opening control module73determines the throttle opening of the electronically controlled throttle61on the basis of the accelerator opening and the rotation speed of the engine, which are inputted thereto, and supplies the electronically controlled throttle61with a control signal so as to realize the determined throttle opening. Specifically, the throttle opening control module73produces a control signal for reducing the deviation between the throttle opening, determined on the basis of the accelerator opening and the engine rotation speed, and the present throttle opening acquired from the throttle opening sensor12and supplies the control signal to the electronically controlled throttle61.

Here, the throttle opening control module73determines a throttle opening, which the electronically controlled throttle61needs to realize, on the basis of a control map held (stored) by the map memory74. This control map is a three dimensional map that relates the throttle opening to the accelerator opening and the engine rotation speed in a desired manner. The throttle opening control module73reads a throttle opening corresponding to the accelerator opening and the engine rotation speed with reference to the control map. The control map will be described in detail hereinbelow.

Moreover, the throttle opening control module73preferably corrects the throttle opening read from the control map on the basis of input from the water temperature sensor13and the atmospheric pressure sensor14and determines a final throttle opening.

Moreover, the map memory74holds a plurality of control maps corresponding to the respective states of the transmission of the engine6, and the throttle opening control module73determines a present transmission ratio of the transmission of the engine6from the ratio between the engine rotation speed and the vehicle speed of the motorcycle1, acquired from the vehicle speed sensor15, and refers to the control map corresponding to the transmission ratio.

FIG. 4Ais a diagram showing one example of a control map that may be used in the engine control unit7.FIG. 4Bshows an enlarged portion of the control map ofFIG. 4A. Specifically,FIG. 4Bshows a portion of the control map ofFIG. 4Acorresponding to a range in which the engine rotation speed is relatively small. The control map ofFIG. 4Aapplies to a case in which the transmission of the engine6is determined to be in neutral, for example, at the time of engine startup, to a period of time that elapses from the startup of the engine until the clutch is connected.

FIGS. 5A to 5Eare graphs showing the relationship in the control map between accelerator opening and throttle opening at specific engine rotation speeds, respectively. Further,FIGS. 6A to 6Dare graphs showing the relationship between engine rotation speed and throttle opening at specific accelerator openings in the control map ofFIG. 4B, respectively.

As shown inFIG. 4A, the control map is set up in such a way that the throttle opening roughly follows the accelerator opening in a range in which the engine rotation speed is larger than a predetermined idle rotation speed. Specifically, the throttle opening is in a linear relationship with the accelerator opening, whereas, in a range in which the accelerator opening is relatively large, the throttle opening is constant irrespective of the accelerator opening.

On the other hand, as shown in the control map ofFIG. 4B, in a range in which the engine rotation speed is lower than the predetermined idle rotation speed, the throttle opening is limited so as to prevent the reverse rotation of the engine. Specifically, the throttle opening is made small in a band-shaped region R located at the higher side of the engine rotation speed in the portion of the control map in which the engine rotation speed ranges from zero to the idle rotation speed and that covers the entire range of the accelerator opening. The throttle opening in this region R is sufficiently small when compared with the throttle opening at the idle rotation speed. By limiting the throttle opening in this manner, an increase in the gas pressure in the combustion chamber of the engine6can be prevented. With this throttle opening limitation, the occurrence of a reverse rotation of the engine6can be prevented.

Moreover, as shown inFIGS. 5B to 5D, the throttle opening is set to be constant, irrespective of the accelerator opening, over a wide range except for a portion where the accelerator opening is near zero in the above-mentioned region R. With this setting, while the occurrence of the reverse rotation of the engine6is prevented, a throttle opening capable of supplying the quantity of fuel necessary for forward rotation of the engine6can be easily kept over the above-mentioned wide region R. That is, whether or not reverse rotation of the engine6occurs depends on the relationship between the engine rotation speed and the throttle opening, as will be described later, so that it is preferable that an appropriate throttle opening is held constant irrespective of the accelerator opening.

Further, as shown inFIGS. 6A to 6D, the throttle opening in the region R is set to be lower than the throttle opening corresponding to when the engine rotation speed is 0. For this reason, a graphical representation of the throttle opening/engine rotation speed relationship exhibits a valley shape in which the bottom portion of the valley is formed in the above-mentioned region R, located at the higher side of the engine rotation speed in the portion of the control map in which the engine rotation speed ranges from zero to the idle rotation speed. Here, the reason why the throttle opening changes linearly relative to the accelerator opening (seeFIG. 5A) when the engine rotation speed is 0 (SeeFIG. 5E) is that when the accelerator grip5is operated in a state where the engine6is stopped, a rider can visually check that the throttle valve is operated according to the operation of the accelerator5.

In this regard, the control map described above is a control map applied to a case where the transmission of the engine6is determined to be in neutral, but in addition to this, the same control map may be applied also to a case where the transmission of the engine6is in another state (e.g., a state of any transmission ratio).

FIG. 7is a diagram showing a method for producing a control map. Here, a method for producing a control map in a range where the engine rotation speed is lower than the idle rotation speed will be described. A map is produced in this range by experimentally determining the conditions under which reverse rotation of the engine6occurs, and then using the experimental results to construct the map.

Specifically, first, the electronically controlled throttle61is controlled to adjust the throttle opening in such a way that the engine rotation speed becomes lower than the idle rotation speed. Here, the idle rotation speed has been previously determined as a relatively large engine rotation speed which is sufficient to prevent the occurrence of reverse rotation of the engine6. A throttle opening for keeping the idle rotation speed is also determined in advance.

Then, the electronically controlled throttle61is controlled to increase the throttle opening in a state where the engine rotation speed is lower than the idle rotation speed. At this time, when a larger quantity of air-fuel mixture than can be compressed flows into the combustion chamber of the engine6, reverse rotation of the engine6occurs. Thus, it is determined whether or not the reverse rotation of the engine6occurs, and the engine rotation speed and the throttle opening (throttle opening after increase) are recorded in correspondence with each other. Here, whether or not reverse rotation of the engine6occurs can be determined, for example, on the basis of detection signals from the crank pulse sensor16.

The above-mentioned process is repeated a number of times while the engine rotation speed and the throttle opening are varied respectively. Thus, as shown inFIG. 7, the conditions under which reverse rotation of the engine6occurs or does not occur can be determined from the observed relationship between the engine rotation speed and the throttle opening.

Then, from the results acquired in this process, the relationship between the engine rotation speed and the throttle opening in which the reverse rotation of the engine does not occur is set in the control map. Thus, the throttle opening that can prevent the occurrence of the reverse rotation of the engine6in a range in which the engine rotation speed is lower than the idle rotation speed is set in the control map.

Here, it is preferable to set a larger throttle opening in the control map among the throttle openings to prevent the occurrence of the reverse rotation of the engine6. It is, therefore, possible to supply a quantity of fuel which is sufficient for the forward rotation of the engine6. Moreover, as described above, when the throttle opening read from the control map is corrected according to the detected water temperature and the atmospheric pressure, it is preferable to set the throttle opening in consideration of a maximum variation by the correction.

Moreover, the relationship between the engine rotation speed and the throttle opening, set in this manner, is set over nearly the entire range of the accelerator opening. The range of the control map in which the engine rotation speed is lower than the idle rotation speed is produced in the manner described above.

It is to be clearly understood that the above description was made only for purposes of example and not as a limitation on the scope of the invention as claimed herein below.