A motorcycle and a method of starting a motorcycle

Abstract

A motorcycle comprising an engine, a throttle, and a controller configured to receive an engine-start signal 312 indicative of a rider’s intention to start the motorcycle, during an initial period aft

Description

Field The present disclosure relates to motorcycles and methods of starting motorcycles. In particular, this disclosure relates to a controlled way of delivering fuel to the motorcycle during an initial period after the engine is started. Background When starting a single cylinder engine in a motorcycle, especially one with relatively low inertia, the compression of the engine can create wildly fluctuating engine speeds as the engine transitions through the stages of the four-stroke combustion cycle. Whilst the average speed may be around 500rpm, for example, the minimum engine speed and maximum engine speed within the cycle can vary hugely. Embodiments of the present disclosure control the amount of fuel that is delivered to an engine immediately after the engine is started in such a way that a quick launch can be achieved. Such a quick launch can be especially useful for motocross I enduro I cross-country motorcycles. Summary According to a first aspect of the present disclosure, there is provided a motorcycle comprising: an engine, which, when running, has an engine speed; a throttle, which is operable by a rider between a fully open amount and a fully closed amount; and a controller, wherein the controller is configured to: receive an engine-start signal, which is indicative of a rider's intention to start the motorcycle; during an initial period after receiving the engine-start signal: receive a throttle-open signal, which represents the amount that the rider has opened the throttle; determine an amount of fuel for providing to the engine based on the throttle-open signal, wherein determining the amount of fuel for providing to the engine during the initial period is independent of engine speed; and deliver the determined amount of fuel to the engine; and after expiry of the initial period: receiving the throttle-open signal, which represents the amount that the rider has opened the throttle; determining an amount of fuel for providing to the engine, after expiry of the initial period, based on the throttle-open signal and the engine speed; and deliver the determined amount of fuel to the engine. Advantageously, such a motorcycle can benefit from a cleaner start and faster launch. In addition, delivering the fuel in this way results in an improved airfuel balance during the initial period, such that the emissions balance is better too. The motorcycle may be a motorcross, a cross-country or an enduro style motorcycle. The initial period may be a predetermined number of engine revolutions. The initial period may be configurable. The controller may be configured to: during the initial period, determine the amount of fuel for providing to the engine based on the throttle-open signal by: using a look-up table or applying an algorithm with a fixed value for engine speed, wherein the fixed value for engine speed is independent of the actual engine speed. According to a further aspect of the present disclosure, there is provided a computer-implemented method of starting a motorcycle, the motorcycle comprising an engine and a throttle, wherein the method comprises: receiving an engine-start signal, which is indicative of a rider's intention to start the motorcycle; during an initial period after receiving the engine-start signal: receiving a throttle-open signal, which represents the amount that the rider has opened the throttle; determining an amount of fuel for providing to the engine based on the throttle-open signal, wherein determining the amount of fuel for providing to the engine during the initial period is independent of engine speed; and delivering the determined amount of fuel to the engine; and after expiry of the initial period: receiving the throttle-open signal, which represents the amount that the rider has opened the throttle; determining an amount of fuel for providing to the engine, after expiry of the initial period, based on the throttle-open signal and the engine speed; and delivering the determined amount of fuel to the engine. There is also provided a computer program that is configured to perform any method disclosed herein. There is also provided a controller configured to perform any method disclosed herein. There may be provided a computer program, which when run on a computer, causes the computer to configure any apparatus, including a controller, disclosed herein or to perform any method disclosed herein. The computer program may be a software implementation, and the computer may be considered as any appropriate hardware, including a digital signal processor, a microcontroller, and an implementation in read only memory (ROM), erasable programmable read only memory (EPROM) or electronically erasable programmable read only memory (EEPROM), as non-limiting examples. The software may be an assembly program. The computer program may be provided on a computer readable medium, which may be a physical computer readable medium such as a disc or a memory device, or may be embodied as a transient signal. Such a transient signal may be a network download, including an internet download. There may be provided one or more non-transitory computer-readable storage media storing computer-executable instructions that, when executed by a computing system, causes the computing system to perform any method disclosed herein. Brief Description of the Drawings One or more embodiments will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 shows an example illustration of a motorcycle; Figure 2 shows a table that can be used by the controller of the motorcycle of Figure 1 to determine how much fuel to deliver to the engine; Figure 3a shows a process flow of an improved way of starting a motorcycle by determining and delivering an amount of fuel to the engine of the motorcycle; and Figure 3b shows a table that is used by the method of Figure 3a to determine how much fuel to deliver to the engine. Detailed Description Figure 1 shows an example illustration of a motorcycle. As is well-known, the motorcycle has an engine, which in this example is a single cylinder engine. The motorcycle also has a throttle, which is operable by the rider to regulate the amount of air-fuel mixture entering the engine. The throttle is operable by the rider between a fully open amount (100%) and a fully closed amount (0%). The motorcycle in this example also has a controller which, among many other things, controls the amount of fuel that is delivered to the engine. Figure 2 shows a table that can be used by the controller of the motorcycle of Figure 1 to determine how much fuel to deliver to the engine. Such tables can also be referred to as look-up tables (LUTs). The different rows in the table indicate the amount of fuel that should be delivered for different throttle positions - that is, the degree to which the rider has opened the throttle. In this example, the figures that are shown in the table represent the length of time, in microseconds, that the fuel injector is open. It will be appreciated that this is proportional to the amount of fuel that is injected. The first row of data in the table is for a throttle position of 0%, which represents the throttle being completely closed. The last row of data in the table is for a throttle position of 100%, which represents the throttle being completely open. In this example, there are 15 rows in between the first and last rows of data, which each represent a different amount that the rider has opened the throttle. It will be appreciated that the specific throttle positions that are shown in the table (1%, 2%, 3%, 4%, 6%, 8%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, 70%, 90%) are purely illustrative, and that different values for the throttle positions that are included in the table can be used in different applications. The different columns in the table indicate the amount of fuel that should be delivered for different engine speeds, which in this example are expressed as different RPM (revolutions per minute) values. The first column of data in the table is for an RPM value of 0. The last row of data in the table is for an RPM value of 2500. In this example, there are 5 columns in between the first and last columns of data, which each represent a different RPM value. It will be appreciated that the specific RPM values that are shown in the table (200, 400, 1000, 1500, 2000) are purely illustrative, and that different values for the engine speed (RPM) values that are included in the table can be used in different applications. In this way, the table of Figure 2 provides a 2-dimensional array of fuel amounts, one of which can be selected by the controller for a specific combination of throttle position and engine speed values. As indicated above, when starting the engine, the engine speed can wildly fluctuate as the engine transitions through the stages of the four-stroke combustion cycle. This would mean that application of the table of Figure 2 can result in fluctuating fuel amounts being determined, even when the throttle is fully closed. This is represented by the dashed arrow 210 in Figure 2. In order to improve the consistency of a normal start, it is possible to use a fixed fuel amount value for an initial period after the engine is started. During the initial period, the fixed fuel amount is delivered to the engine. This is irrespective of the actual throttle position and the engine speed. Then, after the engine has fired and the engine speed is faster and more consistent, the controller can use the table of Figure 2 to determine the amount of fuel to deliver to the engine. In this example, the fixed fuel amount that is used is the one that is shown in the top left-hand corner of the table of Figure 2, which reflects an expectation that the throttle is fully closed when the engine is started. On motocross and enduro style motorcycles, in particular, there can be a requirement to "start-and-go", during some races or when encountering obstacles. The rider can want to launch the motorcycle from a standstill as quickly as possible, and as a result they can sometimes start the motorcycle whilst already applying some throttle opening. However, this throttle opening can result in the fuelling being incorrect, especially when a fixed fuel amount is used during an initial period (as discussed above). This can result in lean running, a poor start and an un-competitive launch. Figure 3a shows a process flow of an improved way of starting a motorcycle by determining and delivering an amount of fuel to the engine of the motorcycle. In particular, to improve the launch of the motorcycle when the throttle is at least partially open when the engine is started. The process flow of Figure 3a can be performed by the controller of Figure 1, and therefore it can be considered as a computer-implemented method. Figure 3b shows a table that is used by the method of Figure 3a to determine how much fuel to deliver to the engine. At step 312, the method involves receiving an engine-start signal, which is indicative of a rider's intention to start the motorcycle. The immediately subsequent steps, steps 313 to 315 are performed during an initial period after receiving the engine-start signal at step 312. As will be appreciated from the discussion that follows, once the initial period has expired, the method moves on to step 317. The initial period can be defined in any suitable way, such as: a predetermined number of revolutions of the engine. In some examples, the length of the initial period can be configurable, for instance by the manufacturer before the motorcycle is provided to the rider. In this way, the steps 313 to 315 of Figure 3a can be considered as a start routine. Once the start routine has been completed, the subsequent steps represent normal operation of the motorcycle. As will be discussed below, the amount of fuel that is to be delivered to the engine is calculated differently during the initial period and the during normal operation. At step 313, the method involves receiving a throttle-open signal, which represents the amount that the rider has opened the throttle. The throttleopen signal is continuously or periodically updated based on how the rider is operating the throttle of the motorcycle. As discussed above, the amount that the rider has opened the throttle can be expressed as a percentage value between 0% and 100%. At step 314, the method involves determining an amount of fuel for providing to the engine based on the throttle-open signal. Determining the amount of fuel for providing to the engine during the initial period, at step 314, is independent of engine speed. Turning to Figure 3b, this means that step 313 of the method determines the fuel amount as one of the fuel amounts that are in a single column of the table. In this example, the engine speed is effectively fixed as 0 RPM when determining the amount of fuel during the initial period, such that only fuel amount values that are shown in the dashed arrow 320 in Figure 3b can be selected. In other examples, the table of Figure 3b can be used with the engine speed fixed at any other suitable value. In further examples still, a completely different table, which is only indexed by the amount that the rider has opened the throttle, can be used during the initial period. Then, at step 315, the method involves delivering the determined amount of fuel to the engine. At step 316 in the method, a check is performed as to whether or not the initial period has expired. For example, as to whether or not a predetermined number of engine revolutions have occurred since the engine-start signal was received at step 312. In one non-limiting example, the initial period can be 16 revolutions. If the initial period has not expired, then the method returns to step 313 such that the start routine can continue by determining, and then delivering, an amount of fuel that is based on an updated throttle position, which may or may not be the same as the previous throttle position (but not based on engine speed). I.e., an instantaneous value for the throttle position. If the initial period has expired, then the method moves on to step 317. Method step 317, and each subsequent step, is therefore performed after expiry of the initial period. At step 317, the method involves receiving a throttle-open signal. This is the same signal that was received at step 313, although, of course it can represent a different throttle position. At step 318, the method involves determining an amount of fuel for providing to the engine (after expiry of the initial period) based on the throttle-open signal and the engine speed. The instantaneous value of engine speed can be received by the method as an engine-speed signal. Determining the amount of fuel in this way is different to the determination that was performed during the initial period at step 314 because, during the initial period, the determination was independent of engine speed. Turning to Figure 3b, this means that step 318 of the method can determine the fuel amount for delivery as any of the fuel amounts that are shown in the table. I.e., it is not restricted to only those values that are shown in the dashed arrow 320. Then, at step 319, the method involves delivering the determined amount of fuel to the engine. Since this represents normal operation of the motorcycle, the method then loops back to step 317 such that the fuel that is delivered to the engine continues to be controlled according to the entire table that is shown in Figure 3b. The strategy that is represented by Figures 3a and 3b allows the fuelling value to be fixed against the zero RPM column of the fuel map (which is another name for the table of Figure 3b), which remains important for the consistency of starts, but now allows the throttle position to be indexed, resulting in a proportional fuel change with differing throttle openings. During the initial period, in one example the 0 RPM index is fixed for an adjustable amount of engine rotations, before allowing movement across the fuel map in the horizontal (RPM) axis. The advantageous result is a cleaner start and launch, which provides a more competitive dead-engine race start. In addition, because there is an improved air-fuel balance during the initial period, the emissions balance is better too. The examples that are described above utilise a look-up table for determining the amount of fuel that is to be delivered to the engine. It will be appreciated that, in other examples, algorithms can be used instead. In such examples, during the initial period an algorithm can be applied to a value that represents the amount that the rider has opened the throttle to determine the amount of fuel for delivering to the engine. After the initial period, an algorithm can be applied to both: a value that represents the amount that the rider has opened the throttle; and an engine speed value to determine the amount of fuel for delivering to the engine. In some examples, the same algorithm can be used during the initial period and after the initial period, but a fixed value is used for the engine speed during the initial period (wherein the fixed value is independent of the actual engine speed).

Claims

1. A motorcycle comprising:an engine, which, when running, has an engine speed;a throttle, which is operable by a rider between a fully open amount and a fully closed amount; anda controller, wherein the controller is configured to:receive an engine-start signal, which is indicative of a rider's intention to start the motorcycle;during an initial period after receiving the engine-start signal:receive a throttle-open signal, which represents the amount that the rider has opened the throttle;determine an amount of fuel for providing to the engine based on the throttle-open signal, wherein determining the amount of fuel for providing to the engine during the initial period is independent of engine speed; anddeliver the determined amount of fuel to the engine; and after expiry of the initial period:receiving the throttle-open signal, which represents the amount that the rider has opened the throttle;determining an amount of fuel for providing to the engine, after expiry of the initial period, based on the throttle-open signal and the engine speed; anddeliver the determined amount of fuel to the engine.

2. The motorcycle of claim 1, wherein the motorcycle is a motorcross, a cross-country or an enduro style motorcycle.

3. The motorcycle of claim 1 or claim 2, wherein the initial period is a predetermined number of engine revolutions.

4. The motorcycle of any preceding claim, wherein the initial period is configurable.

5. The motorcycle of any preceding claim, wherein the controller is configured to:during the initial period, determine the amount of fuel for providing to the engine based on the throttle-open signal by:using a look-up table or applying an algorithm with a fixed value for engine speed, wherein the fixed value for engine speed is independent of the actual engine speed.

6. A computer-implemented method of starting a motorcycle, the motorcycle comprising an engine and a throttle, wherein the method comprises:receiving an engine-start signal, which is indicative of a rider's intention to start the motorcycle;during an initial period after receiving the engine-start signal:receiving a throttle-open signal, which represents the amount that the rider has opened the throttle;determining an amount of fuel for providing to the engine based on the throttle-open signal, wherein determining the amount of fuel for providing to the engine during the initial period is independent of engine speed; anddelivering the determined amount of fuel to the engine; andafter expiry of the initial period:receiving the throttle-open signal, which represents the amount that the rider has opened the throttle;determining an amount of fuel for providing to the engine, after expiry of the initial period, based on the throttle-open signal and the engine speed; anddelivering the determined amount of fuel to the engine.

7. A computer program that is configured to perform the method of claim6.&

Images