WO2017202479A1

WO2017202479A1 - Engine data logger

Info

Publication number: WO2017202479A1
Application number: PCT/EP2016/079167
Authority: WO
Inventors: Christopher Green
Original assignee: Perkins Engines Company Limited
Priority date: 2016-05-27
Filing date: 2016-11-29
Publication date: 2017-11-30
Also published as: CN109154218B; CN109154218A; JP6861737B2; GB201609430D0; JP2019519713A; GB2550908B; GB2550908A; DE112016006815T5

Abstract

Monitoring the engine speed of an internal combustion engine may be beneficial for a number of reasons, but fitting an engine speed determination module to an internal combustion engine can be challenging, requiring an interface to a Control Area Network or additional mechanical measurement equipment. The present disclosure relates to an oil filler cap (100) comprising a vibration sensor (220) and an engine speed determination module (210) configured to determine the engine speed based on a value indicative of the vibration sense by the vibration sensor.

Description

ENGINE DATA LOGGER

Technical field The present disclosure relates to an engine oil filler cap for determining an engine speed, a data logger for mounting on or in an oil filler cap of an engine, a data logger for mounting on an engine and determining a speed of the engine and an oil filler cap for fitting to an oil filling port of an internal combustion engine. Background

Engine data loggers may be used to monitor various engine parameters over time, such as engine speed. Monitoring engine speed over time may help with analysis of various aspects of the engine and its use, for example how a machine operator is typically using the machine's engine, what likely engine wear may be, etc.

Existing engine data loggers tend to be large and costly, either requiring an interface to a Control Area Network (CAN) bus in order to obtain a reading of the current engine speed from an Engine Control Unit (ECU), or requiring additional measurement equipment (such as mechanical, magnetic or laser tachometers, or fuel measurement equipment). Establishing an interface to the CAN bus may be difficult and time consuming, and providing additional measurement equipment may be costly and inconvenient.

Furthermore, some existing engine data loggers are configured to establish an internet connection with a server, where engine speed measurements may be stored over time and/or analysed. Establishing such connections can be costly, inconvenient and potentially unreliable, for example when the machine is located at the geographical limits of an internet network (for example, at the geographical limits of a Radio Access Network (RAN) cell, or at the geographical limits of a WiFi network area, etc). Summary

In a first aspect of the present disclosure, there is provided an engine oil filler cap for determining an engine speed of an internal combustion engine, the engine oil filler cap comprising: an engine speed determination module; and a vibration sensor coupled to the engine speed determination module, wherein the vibration sensor is configured to sense a vibration of the internal combustion engine and output to the engine speed determination module a value indicative of the sensed vibration; and wherein the engine speed determination module is configured to determine an engine speed based on the value indicative of the sensed vibration.

In a second aspect of the present disclosure, there is provided a method for communicating engine data to an electronic device, the method comprising: sensing a vibration of the internal combustion engine; determining an engine speed based on the sensed vibration of the internal combustion engine; storing engine data relating to the determined engine speed in memory; and communicating the engine data to an electronic device via a

communications interface.

In a third aspect of the present disclosure, there is provided a data logger for mounting on or in an oil filler cap of an internal combustion engine, the data logger comprising an engine speed determination module; a vibration sensor coupled to the engine speed determination module, wherein the vibration sensor is configured to sense a vibration of the internal combustion engine; and a memory module coupled to the engine speed determination module; wherein the engine speed determination module is configured to: determine an engine speed based on a value received from the vibration sensor that is indicative of the sensed vibration of the internal combustion engine. In a fourth aspect of the present disclosure, there is provided a data logger for mounting on an internal combustion engine and determining a speed of the internal combustion engine, the data logger comprising: an engine speed determination module; a vibration sensor coupled to the engine speed determination module, wherein the vibration sensor is configured to sense a vibration of the internal combustion engine; a memory module coupled to the engine speed determination module; and a communications module coupled to the engine speed determination module, the communications module being suitable for supporting a communications interface with an external electronic device; wherein the engine speed determination module is configured to: determine a first engine speed based on the vibration of the internal combustion engine sensed by the vibration sensor over a first period of time; determine a second engine speed based the vibration of the internal combustion engine sensed by the vibration sensor over a second period of time; record in the memory module engine data associated with the first engine speed and the second engine speed; and output to the external electronic device, via the communications module, the engine data.

In a fifth aspect of the present disclosure, there is provided an oil filler cap for fitting to an oil filling port of an internal combustion engine, wherein the oiler filler cap comprises: a mounting point for the mounting of a data logger configured to determine a speed of the internal combustion engine.

Drawings

Some aspects of the present disclosure shall be described, by way of example only, with reference to the following drawings, in which:

Figures 1A, 1 B and 1 C show an example external design of an oil filler cap 100;

Figure 2 shows a highly schematic representation of the components of a data logger 200;

Figure 3 shows an example system 300 comprising the data logger 200 of Figure 2;

Figure 4 shows an exploded representation of an assembly of the oil filler cap 100 of Figures 1A, 1 B and 1 C.

Figure 5 shows a side-on cut through of the assembly of the oil filler cap of Figure 4;

Figure 6 shows a flow diagram representation of an example operation of the data logger 200 of Figure 2;

Figure 7 shows a plot of an example engine vibration measurement taken by the data logger 200 of Figure 2;

Figure 8 shows a plot of the frequency response of the engine vibration measurement of Figure 7;

Figure 9 shows a plot of experimental data comparing actual engine speed with engine speed determined by the data logger 200 of Figure 2;

Figure 10 shows a plot of speed error between actual engine speed and determined engine speed in the experimental data of Figure 9;

Figure 1 1 shows an example internal combustion engine 1 100 comprising the oil filler cap of Figures 1 , 4 and 5;

Figure 12 shows an example machine 1200 comprising the internal combustion engine 1 100 of Figure 1 1 ; and

Figure 13 shows an example alternative design of an oil filler cap 1300.

Detailed description

The present disclosure relates to the determination of engine speed using a sensed vibration of an internal combustion engine, and to oil filler caps that either comprise a component(s) configured to determine engine speed using a sensed vibration of an internal combustion engine, or are configured to accommodate the mounting of a component(s) configured to determine engine speed using a sensed vibration of an internal combustion engine. Figures 1 A, 1 B and 1 C are representations of an example external design of an oil filler cap 100 according to the present disclosure. Figure 1 A shows a top-down view of the oil filler cap 100, Figure 1 B shows an angled top/side view of the oil filler cap 100 and Figure 1 C shows a side-on view of the oil filler cap. The top surface 1 12 of the oil filler cap 100 may have a circular, or near-circular, shape when viewed from the top-down. It may have finger grip grooves 1 14 in the side-wall of the oil filler cap 100, to help with screwing the oil filler cap 100 onto, and unscrewing the oil filler cap 100 from, an internal combustion engine (referred to from here on as 'an engine'), such as a diesel engine or a petrol/gasoline engine. It may also have an engine engagement part 122, which is designed to engage with an oil inlet of an engine. As such, the engine engagement part 122 may have an internal or external screw thread for engaging with a corresponding screw thread on the oil inlet of the engine. Thus, the oil filler cap 100 may be screwed into place on the engine in order to cover the oil inlet to prevent dirt or other contaminants entering the engine oil. It will be appreciated that the external design of the oil filler cap 100 represented in Figures 1 A to 1 C is merely one, non-limiting, example of the external design that an oil filler cap according to the present disclosure may take. The oil filler cap 100 may alternatively have any number of different designs, for example it may exclude the finger grip grooves 1 14, and/or have a different engine engagement part 122 design, such as a push-fit design rather than a screw thread design, and/or have a different shape, such as a square or rectangular shape, etc. The dimensions and design of the oil filler cap 100 may be influenced at least in part by the design of the engine and oil inlet to which it is to be attached.

Figure 2 shows a highly schematic representation of a data logger 200 that is suitable for mounting on, or in, the oil filler cap 100. The data logger 200 comprises an engine speed determination module 210 and a vibration sensor 220 coupled to the engine speed determination module 210. The data logger 200 may also comprise a memory module 230 coupled to the engine speed determination module 210, and a communications module 240 coupled to the engine speed determination module 210. The engine speed determination module 210 may be any form of processing/control module configured to perform the functionality described below. For example, it may be a microcontroller, one or more processors (such as one or more microprocessors), configurable logic, firmware, etc. The vibration sensor 220 may be, for example, an accelerometer, such as a one-axis

accelerometer, or a two-axis accelerometer, or a three-axis accelerometer, etc, configured to sense accelerations, for example, such as that caused by vibrations of the engine. The vibration sensor 220 may be configured to sense a vibration of the engine and output to the engine speed determination module 210 a value indicative of the sensed vibration of the engine. The memory module 230 may utilise any suitable memory technology, for example it may comprise a storage disk and/or a solid-state storage device such flash memory and/or an SD (Secure Digital) card, and may comprise volatile and/or non-volatile memory. The communications module 240 may be configured to support communications with one or more electronic devices external to the data logger 200 according to any one or more communications protocols/architectures. For example, the communications module 240 may support one or more types of wired communications, such as USB, Firewire,

Thunderbolt, Ethernet, etc and/or one or more types of wireless communications, such as WiFi, Bluetooth, Bluetooth LE, Near Field Communications (NFC), Infra-red (IR) 5G, LTE, UMTS, EDGE, GPRS, GSM, or any other form of RF based data communications. The communications module 240 enables at least one communications interface 245 to be established between the data logger 200 and an external network element. For example, the network element may be an electronic device, such as an internet server and/or a mobile telephone or smartphone and/or a tablet computer and/or a laptop computer and/or a desktop computer, etc. The interface 245 may be a wired or wireless interface.

The engine speed determination module 210 may also be connected to a temperature sensor 250 and a pressure transducer 260. The temperature sensor 250 may be configured to sense the crankcase temperature of the engine and may be any suitable type of temperature sensor, for example a digital or analogue temperature sensor. The temperature sensor 250 may be configured to output to the engine speed determination module 210 a value indicative of the sensed crankcase temperature. The pressure transducer 260 may be configured to sense the crankcase pressure and may be any suitable type of pressure sensor, for example a piezoelectric sensor with a diaphragm. The pressure transducer 260 may output to the engine speed determination module 210 a value indicative of the sensed crankcase pressure. It will be appreciated that in an alternative implementation, the engine speed determination module 210 may be connected to only one of the temperature sensor 250 or the pressure transducer 260. In a further alternative implementation, the engine speed determination module 210 may not be connected to either of the temperature sensor 250 or the pressure transducer 260. The temperature sensor 250 and/or the pressure transducer 260 may be mounted on the oil filler cap 100 (as described in more detail later), or may be an on-board engine temperature sensor and/or pressure transducer.

Figure 3 shows an example system 300 comprising the data logger 200, a first electronic device 310 and a second electronic device 320. The data logger 200 and the first electronic device 310 may be coupled to each other via the interface 245. The first electronic device 310 and the second electronic device 320 may be network elements. The first electronic device 310 may be a mobile electronic device, such as a mobile telephone (a cell phone), or a smartphone, or a tablet computer, or a laptop computer. The second electronic device 320 may be a desktop computer or an internet server and may be coupled to the first electronic device 310 via an interface 315. The interface 315 may be an internet connection, or any other suitable form of data connection. As explained below, the engine speed determination module 210 may communicate engine data to the first electronic device 310 via the interface 245, which may in turn communicate at least part of the engine data to the second electronic device 320, via the interface 315. Figure 4 shows an "exploded" representation of an example assembly of the oil filler cap 100. Figure 5 shows a cross-sectional side-cut of the example assembly of the oil filler cap 100. The assembly may comprise a combined engine speed determination module and communications module 410, the vibration sensor 220 and the memory module 230. The assembly may further comprise a battery 420 and a battery brace 430. The combined engine speed determination module and communications module 410, the vibration sensor 220 and the memory module 230 may all arranged within a body cavity 465 in a filler cap body 460. A cover 450 may be fixed to the top of the filler cap body 460 in order to close and seal the body cavity 465. The body cavity 465 may therefore be a mounting point on the oil filler cap 100 for mounting the data logger 200.

The battery 420 and the battery brace 430 may also be arranged within the body cavity 465, although Figure 5 shows a configuration where the battery 420 and the battery brace 430 are located within a cavity (or space, or hollow space) within the oil filler cap 100 that is formed when the cover 450 is fixed to the top of the filler cap body 460 (for example, a cavity comprising the body cavity 465 and an opposing cavity in the cover 450). In any event, the cavity within the oil filler cap 100 may be a mounting point for the data logger 200 (and optionally also the battery 420), wherein the cavity may be sealed when the cover 450 is fixed to the top of the filler cap body 460, and exposed when the cover 450 is not fixed to the top of the filler cap body 460.

The vibration sensor 220 is located towards the bottom of the body cavity 465 in the filler cap body 460, such that when the oil filler cap 100 is fitted to the engine, the vibration sensor 220 is the closest component of the data logger 200 to the crankcase of the engine. By arranging these components in this way, the vibration sensor 220 may be positioned close to the engine, which may help to improve its accuracy of vibration sensing. Where the vibration sensor 220 is configured to sense vertical vibrations, it may be mounted horizontally within the body cavity 465, so that when the oil filler cap 100 is fitted to the engine, the vibration sensor 220 it is oriented perpendicular to the axis of vibrations that it will be measuring.

The battery brace 430 may be arranged to hold the battery 420 in place and the battery 420 may be located above the data logger 200 components, towards the top of the cavity within the oil filler cap 100, such that when the oil filler cap 100 is fitted to the engine, the battery 420 is kept as far away from the engine as possible. During use, the engine may become hot, which can have a deleterious effect on the battery 420. Therefore, by positioning the battery 420 as far from the engine as possible, the battery 420 may be better protected from the heat of the engine. Furthermore, the battery 420 may be more easily accessible for replacement or recharging by removing the cover 450. The cover 450 may be fixed to the filler cap body 460 in any suitable way, for example it may be a removable cover fixed to the filler cap body 460 using a screw thread, or by screws or pins that pass through the cover 450, into the filler cap body 460. In an alternative, the cover 450 may be removably fixed to the filler cap body 460 in any other suitable way, for example using a push-fit fixing. In a further alternative, the cover 450 may be fixed to the filler cap body in a non-removable way, for example by gluing or riveting.

The oil filler cap 100 assembly further comprises a sensor module 470 comprising the temperature sensor 250 and/or the pressure transducer 260. The sensor module 470 may be mounted on an external surface of the filler cap body 460, on a surface on the underside of the oil filler cap 100, such that when the oil filler cap 100 is fitted to the engine, the sensor module 470 is exposed to the crankcase of the engine so that crankcase temperature and/or crankcase pressure may be sensed by the sensor module 470. The top surface 1 12 of the oil filler cap 100 may be considered to be a first surface of the oil filler cap 100, and the opposing surface on the underside of the oil filler cap 100, where the sensor module 470 is mounted, may be considered to be a second, opposing surface of the oil filler cap 100.

The sensor module 470 may therefore be physically isolated from the components of the data logger 200. In this way, the components of the data logger 200 may be protected from exposure to oil or debris from the crankcase, and insulated to some extent from heat generated by the engine, whilst still allowing the sensor module 470 to be exposed to the crankcase. The sensor module 470 may be connected to the combined engine speed determination module and communications module 410 by a wired connection through the filler cap body 460, or by a wireless connection, in order to output the values indicative of the sensed crankcase pressure and/or crankcase temperature. It will be appreciated that the assembly represented in Figures 4 and 5 is only one, non- limiting, example of an assembly of the oil filler cap 100 in accordance with the present disclosure. In an alternative, the components of the data logger 200 may be arranged in any way on or within the oil filler cap 100. For example, the data logger 200 may be formed as a single unit comprising the components represented in Figure 2, such as a single circuit board, and designed to be fitted to a mounting point anywhere on the oil filler cap 100. For example, the components of the data logger 200 may be arranged on a single circuit board to be mounted in a cavity in the oil filler cap 100. Alternatively, the components of the data logger 200 may be housed within a unit comprising a magnetic element and the mounting point may comprise a ferromagnetic material (such as iron) on the top of an oil filler cap (or the unit may comprise a ferromagnetic material and the mounting point may comprise a magnetic element on top of the oil filler cap). Alternatively, the components of the data logger 200 may be housed within a unit designed to push-fit onto a mounting point on the top of an oil filler cap, or designed to screw onto a mounting point on the top of an oil filler cap, etc.

The oil filler cap 100 represented in Figures 4 and 5 may also comprise an electrical power connection point, for connecting a power lead from the engine electrical system (for example, the engine battery) to the oil filler cap 100 for providing power to the components within the oil filler cap 100. This may be in addition, or as an alternative, to including the battery 420. For example, where an electrical power connection point is provided in addition to the battery 420, the combined engine speed determination module and communications module 410, the vibration sensor 220 and the memory module 230 may all be powered by the engine electrical system when the engine is turned on (and optionally the battery 420 also charged) and the memory module 230 may be powered by the battery 420 when the engine is turned off (for example, when the memory module 230 comprises volatile memory). Where an electrical power connection point is provided as an alternative to the battery 420, the combined engine speed determination module and communications module 410, the vibration sensor 220 and the memory module 230 may all be powered by the engine electrical system when the engine is turned on, and none of the components powered when the engine is turned off (for example, if the memory module 230 comprises non-volatile memory).

Figure 6 shows an example flow diagram for an operation of the data logger 200. In Step S610, the engine speed determination module 210 receives from the vibration sensor 220 a value indicative of the sensed vibration of the engine and over time makes a record of the values indicative of the sensed vibration of the engine. The vibration may be a vibration of the engine in any direction, for example horizontal and/or vertical vibration. Engine vibrations may be largest in the vertical direction, (the difference between the peaks and troughs in vibration in the vertical direction may be greater than in other directions), resulting in a determination of engine vibration with lower 'noise'. Consequently, it may be preferable to configure the vibration sensor 220 to sense vertical engine vibrations, such that the engine speed determination module 210 may make a record of values indicative of the sensed vertical vibration of the engine.

The engine speed determination module 210 records the values indicative of sensed engine vibration for a determination period of time, which may be any period of time that is sufficient for obtaining a reliable measurement of engine speed. For example, the determination period of time may be any period of time between 0.01 seconds to 10 minutes, such as 0.1 seconds, or 1 second, or 5 seconds, or 1 minute, or 8 minutes, or any period of time between 0.1 seconds to 1 minute, such as 0.3 seconds, or 3 seconds, or 10 seconds, or any period of time between 1 second to 1 minute, such as 8 seconds, or 42 seconds, etc. The data logger 200 may comprise a clock for counting the determination period of time, such as a processor clock, or a crystal clock, or a GPS synchronised clock. The engine speed determination module 210 may record the values indicative of sensed vibration of the engine by periodically sampling the value output from the vibration sensor 220. For example, it may sample the output from the vibration sensor 220 every 2ms (which is a sampling frequency of 500Hz) and record each of the sampled values during the determination period of time in order to obtain a record of the values indicative of sensed vibration of the engine (referred to from hereon as the recorded engine vibration). The sampling frequency may be any suitable frequency, for example any frequency between 50Hz-10,000Hz, such as 200Hz, or 1000Hz, or 8000Hz, or any frequency between 100Hz-5000Hz, such as 150Hz, or 800Hz, or 2000Hz, or any frequency between 100Hz-1000Hz, such as 400Hz, or 600Hz, etc. The sampling frequency may be chosen in consideration of the maximum dominant frequency expected for the engine vibration (for example, a sampling frequency that is sufficiently high to accurately measure the maximum expected dominant frequency in the engine vibration).

Figure 7 shows an example plot of the sensed engine vibration recorded in Step S610. In this example, the sampling frequency is 500Hz, the determination period of time is 0.5 seconds (i.e., 250 samples), the vibration sensor 220 is an accelerometer configured to sense vertical acceleration of the engine and the engine is a four cylinder straight (in-line) engine. The x-axis on the plot is the sample number (which might equally be viewed as 'time') and the y-axis on the plot is the vertical acceleration of the engine in units of m/s². In Step S620, the engine speed determination module 210 determines the engine speed based on the recorded engine vibration. The engine speed determination module 210 may do this by first determining the dominant frequency in the recorded engine vibration, for example by performing a time-to-frequency domain transformation on the recorded engine vibration, such as a Fourier transform, or a Fast Fourier Transform (FFT), or a Laplace transform, etc.

Figure 8 shows a plot of the frequency response (i.e., the time-to-frequency transformation) of the recorded engine vibration represented in Figure 7. The x-axis of the plot in Figure 8 is frequency in units of Hz and the y-axis of the plot in Figure 8 is a dimensionless measure of magnitude.

The engine speed determination module 210 may then determine the dominant frequency by identifying the frequency with the greatest magnitude in the frequency response plot. The engine speed determination module 210 may consider only a particular range of frequencies within the frequency response when finding the dominant frequency. The range may be defined by a lower frequency limit and an upper frequency limit, both of which may be set in consideration of expected engine vibration frequencies, in order to exclude any frequencies that fall outside of expected engine operation. For example, if the idling speed of the engine is expected to generate a vibrational frequency of about 35Hz and the maximum possible engine speed is expected to generate a vibrational frequency of about 90Hz, the considered range may be 30Hz (lower frequency limit) to 100Hz (upper frequency limit). Of course, the maximum and minimum frequencies that an engine should generate will vary for different types of engine, for example with cylinder configuration (straight cylinder, V cylinder, Boxer, etc), engine speed limits and engine idle speeds. Therefore, the range of frequencies considered during determination of the dominant frequency may be set to any suitable range in consideration of the engine being assessed.

The dominant frequency may be the frequency corresponding to the peak frequency response. Where there are two or more peaks in the frequency response (for example, because the engine speed changed during the measurement period of time), the dominant frequency may be the frequency corresponding to the peak with the greatest magnitude. Thus, the dominant frequency may be the frequency of vibration that was generated by the engine for the longest period of time during the measurement period of time.

The engine speed determination module 210 may then determine the engine speed based on the dominant frequency. For example, the dominant frequency may be converted into a measurement of engine speed, such as Revolutions Per Minute (RPM). A measure of frequency in Hertz is a measure of the number of vibration cycles per second. To convert vibrational frequency in Hz to the number of vibration cycles per minute, the dominant frequency may be multiplied by 60. The relationship between vibration cycles and engine revolutions may depend on the configuration of the engine. Vibration cycles may be caused by cylinder combustion events, thus the dominant frequency may also be thought of as the firing frequency of the engine. The number of cylinder combustion events, or firing events, per engine revolution may depend on the configuration of the cylinders. For example, for a four cylinder straight (in-line) engine, there may be two combustion events per engine revolution. Consequently, the firing frequency would be double the engine speed. However, for a three cylinder straight (in-line) engine, there may be 3 combustion events for every two engine revolutions (i.e., 1.5 combustion events per engine revolution), and for a six cylinder straight (in-line) engine, there may be three combustion events per engine revolution.

Consequently, the firing frequency would be one and a half times the engine speed.

The engine speed may therefore be determined from the dominant frequency as follows:

Dominant frequency (in Hz) x 60

Engine speed (in RPM) =

Number of combustion events per engine revolution

Therefore, for a four cylinder straight engine with two combustion events per engine revolution, the engine speed in RPM may be calculated as follows:

Dominant frequency (in Hz) x 60

Engine speed =

For a three cylinder straight engine with one and a half combustion events per engine revolution, the engine speed in RPM may be calculated as follows:

Dominant frequency (in Hz) x 60

Engine speed = —

The recorded engine vibration represented in the plot of Figures 7, and corresponding frequency domain plot of Figure 8, were made on a four cylinder straight engine. As can be seen, the dominant frequency in the frequency response represented in Figure 8 is 65Hz. Therefore, the determined engine speed is: 65 X 60

Engine speed =

Engine speed = 1950 RPM

Experimentation using a four cylinder straight engine has been performed to determine the accuracy of this process. An engine was swept from 800rpm to 3024rpm with a 'real' engine speed (measured by an engine dynamometer, or 'dyno') being compared with the engine speed determined using the above described process. Figure 9 shows a graphical plot representing the actual engine speed (the dotted line) and the determined engine speed (the solid line). The x-axis of the plot in Figure 9 is the test time and the y-axis of the plot in Figure 9 is engine speed in rpm. Figure 10 shows a graphical plot of speed error between the actual engine speed and the determined engine speed. The x-axis of the plot in Figure 10 is the engine speed in rpm and the y-axis of the plot in Figure 10 is the speed error in rpm between the determined engine speed and the actual engine speed. For some engine speeds, there are two engine speed error values (for example, at 10OOrpm, there is a speed error of 20rpm and 80 rpm). This is caused by two different engine speeds being determined during the period of time for which the engine was held at a particular speed during the experiment. For example, if engine speed is determined every 0.5 seconds (because the determination period of time is 0.5 seconds), but the engine is held at a particular speed for 4 seconds, the engine speed will be determined eight consecutive times (once every 0.5 seconds). This may be seen in Figure 9, where at some engine speeds two different engine speeds are determined (for example, at 10OOrpm, an initial speed of

1020rpm is determined, which then increases to 1080rpm and then fluctuates between the two values). These fluctuations may occur for any number of experimental reasons, which may include the resolution accuracy of the time-to-frequency domain transformation (as explained below). As explained below, even with these fluctuations, the accuracy of engine speed determination may still be within acceptable limits.

As can be seen from Figure 10, the determined engine speed was found always to be within 80rpm of the actual engine speed. The time-to-frequency domain transformation used for this experiment was a Fourier transform with a resolution of 1 .9Hz, which equates to approximately 60rpm. It may be anticipated that by using different and/or better tuned time- to-frequency domain transformation techniques, this resolution may be improved and the engine speed error therefore reduced. However, in any event, for most applications, engine speed determinations within +/- 100rpm of the actual engine speed may be expected to be sufficient. In Step S630, the engine speed determination module 210 may record the determined engine speed in the memory module 230. There are a number of different ways in which the determined engine speed may be recorded in the memory module 230. Examples of the ways in which the determined engine speed may be recorded in the memory module 230 are explained below. It will be appreciated that the engine speed determination module 210 may utilise any one or more of these example techniques.

Example 1 : the determined engine speed may be saved in the memory module 230, optionally along with an identifier of the time at which the determination was made (for example, the date and time of determination). In this way, over time a plurality of engine speeds may be saved in the memory module 230, optionally each with an identifier of the time at which the determination was made. Optionally, the determination period of time may also be saved in the memory module 230 with the determined engine speed. By doing so, a record of each determined engine speed, and the period of time for which the engine was determined to be operating at that speed, may be kept. These data may be recorded in the memory module 230 in any suitable way, for example by using any standard database or matrix techniques. Example 2: the engine speed determination module 210 may look up an engine speed/time record in the memory module 230. The engine speed/time record may comprise a plurality of engine speed ranges and the cumulative time for which the engine has been determined to be operating within each of the engine speed ranges. A non-limiting example engine speed/time record is set out below:

1900 rpm - 1999 rpm 6.25

2000 rpm - 2099 rpm 4.62

It will be appreciated that the engine speed/time record may comprise any number of engine speed ranges, and the ranges may be of any suitable size and spread. The engine speed determination module 210 may determine which of the plurality of engine speed ranges the determined engine speed lies within and then add the determination period of time to the cumulative time for that engine speed range. Thus, a picture of the operation of the engine may be built up over time. In the example described above in respect of Figures 7 and 8, if the determined engine speed is 2600 rpm, the engine speed determination module 210 may determine that the determined engine speed lies within the range 2600-2699 rpm. The engine speed determination module 210 may then add the determination period of time to the cumulative time recorded for that engine speed range in the engine speed/time record. For example, if the cumulative time recorded in the engine speed/time record for 2600-2699rpm is 1 .23 hours, and the determination period of time is 0.5 seconds, the cumulative time recorded in the engine speed/time record for 2600-2699rpm will be updated to 1 .23 hours + 0.5 seconds. Having added the determination period of time to the cumulative time for the determined engine speed range, the engine speed determination module 210 may then write the updated engine speed/time record to the memory module 230.

It will be appreciated that the engine speed ranges and cumulative times may be saved in the memory module 230 in any suitable way, for example using any standard database or matrix techniques.

After recording the determined engine speed to the memory module 230 in accordance with example 1 and/or example 2, the engine speed determination module 210 may return to Step S610. In this way, the engine speed may be regularly determined, or sampled, (for example, every 0.5 seconds) and then stored in memory, such that extensive engine speed data are stored over time. It will be appreciated that after recording of the values indicative of sensed engine vibration over the determination period of time is completed in Step S610 and the process proceeds to Step S620, recording of values indicative of sensed engine vibration for the next determination period of time may immediately begin whilst Steps S620 and S630 are being performed, such that there is no period of operation of the engine that does not contribute to a determination of the engine speed. Consequently, whilst Steps S620 and S630 are being carried out in respect of the most recently completed recording of the values indicative of sensed engine vibration, the next recording of values indicative of sensed engine vibration may already be underway.

The engine speed determination module 210 may be configured to reset (for example, set to zero) the cumulative time for all of the engine speed ranges. The engine speed

determination module 210 may reset the cumulative times periodically (for example, every 100 days) and/or after engine data comprising the engine speed/time record has been output from the data logger 200 via the interface 245 and/or in response to a user reset command received via the interface 245 (for example, when the engine is serviced, the service operator may instruct the engine speed/time record to be reset).

At any suitable time, the data logger 200 may output engine data to the first electronic device 310 via the interface 245. The engine data may comprise the most recently determined engine speed (and optionally also the measurement time period) such that a 'current' determined engine speed may be output and/or the recorded data from example 1 above and/or the recorded data from example 2 above. Thus, the engine data may comprise the engine speed/time record. The engine data may be output periodically to the first electronic device 310 via the interface 245 (for example, 'pushed' to the first electronic device 310), or may be output after the engine speed determination module 210 receives a request for engine data from the first electronic device 310 via the interface 245 (for example, 'pulled' by the first electronic device 310). In an example, the interface 245 may utilise Bluetooth LE and the engine data may be output to the first electronic device 310 if the first electronic device 310 is paired with the data logger 200 and requests, i.e., 'pulls', the engine data. Likewise, in a further example, if the interface 245 utilises TCP/UDP over WiFi, the first electronic device 310 may be allowed to pull the engine data from the data logger 200.

The first electronic device 310 may save at least part of the engine data and/or display at least part of the engine data to a user (for example, via a display screen on the first electronic device 310). The engine data may be displayed as raw data, or in any suitable graphical format, such as a bar chart, etc. If the engine data are stored on the first electronic device 310, the first electronic device 310 may also append location data to the engine data, for example using a built-in GPS module on the first electronic device 310. The first electronic device 310 may also be configured to perform an analysis of the engine data, for example using the engine data to calculate engine wear metrics and/or to analyse the way in which the engine is being used and/or to calculate number of hours until next required engine service, etc. Any one or more of these calculated items of information may be displayed to the user, for example via a display screen on the first electronic device 310.

Additionally, or alternatively, the first electronic device 310 may communicate at least part of the engine data to the second electronic device 320 via the interface 315, for example upon request of the user of the first electronic device 310. In this way, the interface 315 need only be active at times when a data transfer is requested, such that a permanent interface (such as a permanent internet connection) is not required. The at least part of the engine data may be communicated along with any other suitable data, for example location data and/or calculated engine wear metrics and/or calculated time until next required engine service. The second electronic device 320 may store the received data, for example keeping a backup for access by the user of the engine, or by servicing personnel, at a later date.

Additionally, or alternatively, the second electronic device 320 may perform an analysis on the received data, for example to calculate engine wear metrics and/or calculate the number of hours until next required engine service, etc. The second electronic device 320 may make data, such as the engine data and/or any determined data like engine metrics or number of hours until next engine service or histograms etc, available to an owner/operator of the engine, and/or a dealer or service personnel, for example via a web page interface. The second electronic device 320 may additionally or alternatively email data, such as the engine data and/or any determined data like engine metrics or number of hours until next engine service or histograms etc to any authorised parties, such as an owner/operator of the engine, and/or a dealer or service personnel.

In addition to determining the engine speed, the engine speed determination module 210 may also determine the crankcase temperature by reading from the temperature sensor 250 a value indicative of the sensed crankcase temperature and/or determine the crankcase pressure by reading from the pressure transducer 260 a value indicative of the sensed crankcase pressure. The engine speed determination module 210 may record the value indicative of the sensed crankcase temperature and/or the value indicative of the sensed crankcase pressure in the memory module 230 along with the determined engine speed. The crankcase temperature and/or crankcase pressure may be determined at the same time that the engine speed is determined, such that for each determined engine speed there is a corresponding crankcase temperature and/or crankcase pressure. Alternatively, the crankcase temperature and/or crankcase pressure may be determined more or less frequently than the engine speed is determined. Analogously to examples 1 and 2 described above with respect to recording the determined engine speed, the determined crankcase temperature and/or crankcase pressure may be recorded in the memory module 230 using any one or more of the following example techniques:

Example A: the value indicative of the sensed crankcase temperature and/or the value indicative of the sensed crankcase pressure may be saved in the memory module 230, optionally along with an identifier of the time at which the determination was made (for example, the date and time of determination). In this way, a plurality of determined engine temperatures and/or crankcase pressures may be saved in the memory module 230 over time, optionally each with an identifier of the time at which the determination was made. Optionally, the determination time period may also be saved in the memory module 230 with the determined crankcase temperature and/or crankcase pressure. By doing so, a record of each crankcase temperature and/or crankcase pressure, and the period of time for which the engine was operating at that crankcase temperature and/or crankcase pressure, may be kept. These data may be recorded in the memory module 230 in any suitable way, for example by using any standard database or matrix techniques. Example B: the engine speed determination module 210 may look up a crankcase temperature/time record and/or crankcase pressure/time record in the memory module 230. The crankcase temperature/time record may comprise a plurality of crankcase temperature ranges and the cumulative time for which the engine has been operating within each of the crankcase temperature ranges. The crankcase pressure/time record may comprise a plurality of crankcase pressure ranges and the cumulative time for which the engine has been operating within each of the crankcase pressure ranges. A non-limiting example of a crankcase temperature/time record is set out below:

It will be appreciated that the crankcase temperature/time record may comprise any number of crankcase temperature ranges, and the ranges may be of any suitable size and spread.

Analogously to example 2 above, the engine speed determination module 210 may determine which of the plurality of crankcase temperature ranges the determined crankcase temperature lies within and then add the determination period of time to the cumulative time for that crankcase temperature range. Having added the determination period of time to the cumulative time for the determined crankcase temperature range, the engine speed determination module 210 may write the updated crankcase temperature/time record to the memory module 230.

A non-limiting example of a crankcase pressure/time record is set out below:

It will be appreciated that the crankcase pressure/time record may comprise any number of crankcase pressure ranges, and the ranges may be of any suitable size and spread.

Furthermore, it may be noted that in this particular example, some of the pressure ranges are negative pressure ranges. This is because they are pressures relative to a reference pressure, for example relative to atmospheric pressure. In an alternative, the pressure ranges may comprise absolute measurements of pressure.

Analogously to example 2 above, the engine speed determination module 210 may determine which of the plurality of crankcase pressure ranges the determined crankcase pressure lies within and then add the determination period of time to the cumulative time for that crankcase pressure range. Having added the determination period of time to the cumulative time for the determined crankcase pressure range, the engine speed

determination module 210 may then write the updated crankcase pressure/time record to the memory module 230. The engine speed determination module 210 may be configured to reset (for example, set to zero) the cumulative time for all of the crankcase temperature ranges and/or crankcase pressure ranges, analogously to resetting the cumulative time for all engine speed ranges described earlier.

It will be appreciated that the crankcase temperature/time record and/or the crankcase pressure/time record may be saved in the memory module 230 in any suitable way, for example using any standard database or matrix techniques. The determined crankcase temperature and/or crankcase pressure stored in the memory module 230 in accordance with example A and/or example B may be communicated to the first electronic device 310 as part of the engine data. The engine data may therefore comprise a plurality of sets of data: engine speed data and crankcase temperature data and/or crankcase pressure data. Alternatively, the engine speed data may be combined with the crankcase temperature data and/or the crankcase pressure data into a single map or matrix, which identifies the cumulative time spent at each combination of engine speed range/crankcase temperature range/crankcase pressure range.

The above disclosed operation of the data logger 200 may be implemented by one or more computer programs (for example, one or more computer-readable media) comprising computer readable instructions. For example, the memory module 230, or some other memory unit coupled to the data logger 200 or engine speed determination module 210, may comprise one or more computer programs configured to carry out the above disclosed operations when executed on a processor (such as on the engine speed determination module 210). The computer program may alternatively be stored on any other suitable storage medium, such as a hard-disk drive and/or solid-state drive, at least one storage reading drive, such as a diskette and/or CD-ROM and/or DVD and/or Blu-ray disk and/or USB drive etc. Figure 1 1 shows a representation of an example internal combustion engine 1 100, for example a diesel or petrol engine, on which the oil filler cap 100 may be fitted.

Figure 12 shows an example machine 1200 within which the internal combustion engine 1 100 may be fitted. It will be appreciated that the machine 1200 represented in Figure 12 is only one example type of machine and that the internal combustion engine 1 100 comprising the oil filler cap 100 may be used in any suitable machine, for example a car, or a back-hoe loader, or a compactor, etc. It will also be appreciated that the internal combustion engine 1 100 comprising the oil filler cap 100 may alternatively be used in any other suitable type of machine, such as a generator, or generator set, or air compressor, etc. Therefore, the machine 1200 is only one example of a machine in which the internal combustion engine 1 100 comprising the oil filler cap 100 may be used.

The skilled person may readily appreciate that a number of alterations and/or alternatives to the aspects described above may be implemented and still fall within the scope of the present disclosure. For example, rather than store the determined engine speed in the memory module 230, the engine speed determination module 210 may instead only broadcast the determined engine speed to the first electronic device 310 via the interface 245. Thus, the term 'data logger' 200 as used in the present disclosure is intended to encompass devices that store, or log, data (such as engine speed) and also devices that simply determine data (such as engine speed), but do not themselves record, or log, data (recording, or logging, of the data, such as engine speed, may instead be performed by the first electronic device 310 and/or the second electronic device 320). Likewise, if the engine speed determination module 210 is also configured to determine crankcase temperature and/or crankcase pressure, the crankcase temperature and/or crankcase pressure may not be stored in the memory module 230, but instead only broadcast to the first electronic device 310.

In the system 300 represented in Figure 3, there is a first electronic device 310 and a second electronic device 320. However, it will be appreciated that in an alternative, there may be only the data logger 200 and one electronic device (such as an internet server) in the system 300, with an interface between the data logger 200 and the electronic device. Alternatively, the system 300 may comprise the data logger 200 and three or more interconnected electronic devices. Whilst the interfaces in Figure 3 are represented as direct interfaces, it will be appreciated that there may be one or more further intervening devices in the interfaces, such as internet routers, etc.

Whilst in the above described aspects, components of the data logger 200 are located within the oil filler cap 100, it will be appreciated that the data logger 200 may be designed to be fitted to any other part of an engine that is suitable for the mounting of the data logger 200 that enables to vibration sensor 220 to accurately measure engine vibrations, such as bolted to the outside or inside of an engine top mount cover, or integrated into an engine top mount cover, or bolted to the timing case of the engine, etc. Figures 13A, 13B and 13C show a representation of an example alternative oil filler cap 1300 in accordance with the present disclosure. Figure 13A shows a top-down view of the oil filler cap 1300, Figure 13B shows a side-on view of the oil filler cap 1300 and Figure 13C shows a side-on cut-through view of the oil filler cap 1300. It can be seen that the design of the oil filler cap 1300 is different to that of oil filler cap 100 represented in Figures 1A-1 C, 4 and 5, and is simply one example of an alternative oil filler cap design. As can be seen in Figure 13C, the oil filler cap 1300 comprises a circuit board 1310, which may comprise the components of the data logger 200 described above. In an alternative configuration, the oil filler cap 1300 may comprise two or more circuit boards, each comprising at least one of the modules of the data logger 200 described above.

In addition to the data identified in the above disclosed example implementations, the engine data may also comprise at least one of the total time for which the engine has been operating and/or the engine serial number (which may be stored in the memory module 230 and/or some other memory in the data logger 200, such as a ROM or EPROM module).

The engine speed determination module 210 may be further configured to maintain a record in the memory module 230 of the 'last run date'. The engine speed determination module 210 may periodically (for example, every minute, or every hour, or every two hours, etc) update the time and/or date of the 'last run date'. In this way, if power is lost to the data logger 200, there may be a record in the memory module 230 of the time and/or date when the data logger 200 was still operating. Optionally, the engine data may further comprise the 'last run date'. Industrial applicability

By providing an engine speed determination module and a vibration sensor in an engine oil filler cap as described above, engine speed determination may be achieved more straightforwardly. In particular, engine oil filler caps are easily accessible and easily replaceable, meaning that an old, standard engine oil filler cap may easily be removed and replaced with an engine oil filler cap in accordance with the present disclosure, for example during a routine engine service. By determining engine speed using a measurement of vibration from the vibration sensor, it is not necessary to implement an interface to a Control Area Network (CAN) bus (for engines with an ECU), or to set up additional measurement equipment such as mechanical, magnetic or laser tachometers, or fuel measurement equipment (for engines without an ECU). Thus, engine speed determination functionality may more cheaply and straightforwardly be added to any type of engine (i.e. the engine speed determination module and vibration sensor may be straightforwardly retro-fitted to engines).

Engine speed may be determined based on the dominant frequency of the engine vibration, which results in a relatively accurate (within 80rpm) determination of engine speed, whilst utilising relatively low complexity computing processes. The dominant frequency may be determined by identifying, within a range of frequencies of a frequency response between a lower frequency limit and an upper frequency limit, a frequency corresponding to the greatest magnitude of the frequency response, wherein the frequency corresponding to the greatest magnitude of the frequency response is the dominant frequency. By looking only in a range of frequencies between a lower frequency limit and an upper frequency limit, frequencies outside of the engine operating range (for example, frequencies that would be generated by the engine operating below idle speed, or above an engine speed limit) may be excluded from the determination process. This may increase the speed of identification of the dominant frequency and/or improve accuracy by reducing the chance of the incorrect frequency being identified as the dominant frequency (for example, harmonic frequencies or other artefacts may fall outside of the frequency range and therefore may not be identified as the dominant frequency). The engine speed determination module may record the determined engine speed along with the determination period of time in a memory module. In one particular example, the engine speed determination module may determine in which of a plurality of engine speed ranges the determined engine speed falls and add the determination period of time to a cumulative period of time recorded in the memory module for which the engine has been operating in the determined engine speed range. By recording data relating to the determined engine speed and the determination period of time, a picture of engine speed operation over time may be built up, which may be useful for analysis of how the engine is being operated, what engine wear is likely to be and/or what the engine service interval should be. For example, a number of engines may have default 500 hour service intervals. However, this may not be necessary for all engines, particularly for engines that are run on low duty cycles, in which case longer service intervals (such as 1000 hours) may be determined, which will save time and money for the machine's owner.

In the above aspects of the disclosure, engine data may be stored over time in a memory module and then output to an external electronic device via a communications module. In one example, the external electronic device may issue a request for engine data to the engine speed determination module, in response to which the engine speed determination module may look-up the stored engine data in the memory module and output it to the electronic device via the communications module. For example, an operator may transfer engine data to a smartphone or tablet computer at the end of a working day, wherein the engine data comprises data relating to the engine operation for the whole working day. By outputting stored engine data in this way, it may be ensured that there is a good, reliable communications interface with the external electronic device before any data is

communicated. Thus, it is not necessary to maintain complicated and costly

communications interfaces at all times. Furthermore, there is reduced risk of any data being lost due to unreliable communications interfaces, thereby improving the reliability of the data received by the external electronic device.

The interface with the external electronic device may be a wireless interface, such as a short-range wireless interface such as Bluetooth, Bluetooth LE or WiFi, which may enable straightforward data transfer compared with a wired connection and lower cost transfer by not requiring the communications module to establish an internet connection with a server. Furthermore, the external electronic device may also comprise its own internet connection (for example, if the external electronic device is a smartphone or a tablet computer), which may be exploited to forward the engine data to a server cheaply and straightforwardly. In an aspect of the present disclosure, the oil filler cap may comprise a temperature sensor and/or a pressure transducer, such that the engine speed determination module may determine the engine crankcase temperature and/or crankcase pressure. The crankcase temperature and/or crankcase pressure may also be stored in a memory module, along with the determined speed. Having a record of the crankcase temperature and/or crankcase pressure in the engine data may help to improve the accuracy of any analysis performed using the engine speed data, for example analysis of how the engine is being operated, what engine wear is likely to be and/or what the engine service interval should be.

In a further aspect of the present disclosure, there is provided a data logger for mounting on or in an oil filler cap of an engine, wherein the data logger comprises a vibration sensor and an engine speed determination module configured to determine the engine speed based on a the vibration of the engine sensed by the vibration sensor. Engine oil filler caps are easily accessible, for example during a standard engine service, and so configuring the data logger for mounting on or in an oil filler cap means that the data logger may easily be fitted to the engine. Furthermore, by determining engine speed using the vibration sensed by the vibration sensor, it is not necessary to implement an interface to a Control Area Network (CAN) bus (for engines with an ECU), or to set up additional measurement equipment such as mechanical, magnetic or laser tachometers, or fuel measurement equipment (for engines without an ECU). Thus, engine speed determination functionality may straightforwardly be added to any type of engine. In a further aspect of the present disclosure, there is provided a data logger for mounting on an engine and determining a speed of the engine. The data logger comprises an engine speed determination module and a vibration sensor, the data logger being configured to determine a plurality of engine speeds over time based on the vibration of the engine sensed by the vibration sensor, and record in memory engine data associated with the determined engine speeds. The data logger is further configured to output to an external electronic device the engine data. By determining engine speed using the vibration sensed by the vibration sensor, it is not necessary to implement an interface to a Control Area Network (CAN) bus, or to set up additional measurement equipment such as mechanical, magnetic or laser tachometers, or fuel measurement equipment. Thus, engine speed determination functionality may straightforwardly be added to any type of engine.

Furthermore, by storing engine data in a memory module and then outputting the engine data to the external electronic device, it may be ensured that there is a good, reliable communications interface with the external electronic device before any data is

communicated. Thus, it is not necessary to maintain complicated and costly

communications interfaces at all times. Furthermore, there is reduced risk of any data being lost due to unreliable communications interfaces, thereby improving the reliability of the data received by the external electronic device. In a further aspect of the present disclosure, there is provided an oil filler cap comprising a mounting point for the mounting of a data logger configured to determine of a speed of the internal combustion engine. Engine oil filler caps may be easily accessible, for example during a routine engine service. An engine oil filler cap according to this aspect of the present invention may therefore enable straightforward attachment of a data logger to the engine. Thus, when engine speed determination functionality is desired for an engine that does not have such built in functionality (for example, so that engine speed data can be used by serving personnel, etc), the functionality may very straightforwardly be added to the engine by fitting a suitable data logger to the engine oil filler cap. The engine oil filler cap may comprise a cavity, wherein the cavity comprises the mounting point. A data logger positioned within the cavity may therefore be positioned within the engine oil filler cap, thereby protecting the data logger from damage, for example from physical impacts, oil and other fluids and dirt, and/or heat from the engine.

The oil filler cap may comprise a removable cover, such that when the removable cover is fixed in position, the cavity is a sealed, hollow cavity, and when the removable cover is removed from the body, the cavity is exposed such that at least part of a data logger and/or a battery mounted in the cavity may be accessed by a user. The removable cover may therefore enable straightforward inspection and/or replacement of the data logger and/or battery.

The oil filler cap may also comprise a data logger comprising a vibration sensor and an engine speed determination module, where the vibration sensor and engine speed determination module are arranged such that, when the oil filler cap is fitted to the oil filling port of an internal combustion engine, the vibration sensor is closer than the engine speed determination module to the crankcase of the internal combustion engine. By positioning the vibration sensor closer to the crankcase of the engine, the vibration sensor may more accurately sense the vibrations of the engine. The oil filler cap may also comprise a battery arranged such that when the oil filler cap is fitted to the oil filling port, the distance between the battery and the crankcase is greater than the distance between vibration sensor and the crankcase, and is greater than the distance between the engine speed determination module and the crankcase. In this way, the battery (which is likely to be sensitive to heat) may be better protected from heat generated by the engine. Furthermore, the battery may be more easily accessible for straightforward replacement and/or recharging.

Claims

1 . An engine oil filler cap for determining an engine speed of an internal combustion engine, the engine oil filler cap comprising:

an engine speed determination module; and

a vibration sensor coupled to the engine speed determination module, wherein the vibration sensor is configured to sense a vibration of the internal combustion engine and output to the engine speed determination module a value indicative of the sensed vibration; and wherein the engine speed determination module is configured to determine an engine speed based on the value indicative of the sensed vibration.

2. The engine oil filler cap of claim 1 , wherein the engine speed determination module is further configured to:

record, over a determination of period of time, a plurality of values indicative of the sensed vibration; and

determine an engine speed based on the recorded values indicative of the sensed vibration.

3. The engine oil filler cap of claim 2, wherein the engine speed determination module is configured to determine the engine speed based on the recorded values indicative of the sensed vibration by:

determining a dominant frequency of vibration from the recorded values indicative of the sensed vibration; and

determining the engine speed based on the determined dominant frequency of vibration.

4. The engine oil filler cap of claim 3, wherein the engine speed determination module is configured to determine the dominant frequency of vibration from the recorded values indicative of the sensed vibration by:

performing a time-to-frequency domain transformation on the recorded values indicative of the sensed vibration to generate a frequency response of the recorded values indicative of the sensed vibration; and

identifying, within a range of frequencies of the frequency response between a lower frequency limit and an upper frequency limit, a frequency corresponding to the greatest magnitude of the frequency response, wherein the frequency corresponding to the greatest magnitude of the frequency response is the dominant frequency.

5. The engine oil filler cap of any preceding claim, further comprising a memory module coupled to the engine speed determination module, wherein the memory module is for storing engine data.

6. The engine oil filler cap of claim 5, wherein the engine speed determination module is further configured to record the determined engine speed in the engine data.

7. The engine oil filler cap of claim 6, when dependent on any of claims 2 to 4, wherein the engine speed determination module is further configured to record in the engine data the determination period of time with an association to the recorded engine speed.

8. The engine oil filler cap of any of claims 5 to 7, when dependent on any of claims 2 to 4, wherein the engine speed determination module is further configured to

determine which of a plurality of engine speed ranges the determined engine speed falls within; and

add the determination period of time to a cumulative time recorded in the engine data for which the internal combustion engine has been operating in the determined engine speed range.

9. The engine oil filler cap of any preceding claim, further comprising a communications module coupled to the engine speed determination module, wherein the communications module is suitable for supporting a communications interface with an electronic device, and wherein the engine speed determination module is further configured to:

output to an electronic device, via the communications module, the determined engine speed and/or the engine data.

10. The engine oil filler cap of claim 9, when dependent on any of claims 5 to 8, wherein the engine speed determination module is further configured to:

receive a user reset command via the communications module; and

reset the engine data in the memory module.

1 1 . The engine oil filler cap of either claim 9 or claim 10, when dependent on any of claims 5 to 8, wherein the engine speed determination module is further configured to:

receive a request for the engine data from the electronic device via the

communications module; and

in response to receipt of the request for the engine data, output to the electronic device, via the communications module, the engine data.

12. The engine oil filler cap of any preceding claim, further comprising:

a temperature sensor coupled to the engine speed determination module, wherein the temperature sensor is configured to sense a temperature of a crankcase of the engine and output to the engine speed determination module a value indicative of the sensed crankcase temperature; and/or

a pressure transducer coupled to the engine speed determination module, wherein the pressure transducer is configured to sense a pressure of a crankcase of the engine and output to the engine speed determination module a value indicative of the sensed crankcase pressure.

13. The engine oil filler cap of claim 12, when dependent on any of claims 5 to 8, further configured to record the value indicative of sensed crankcase temperature and/or the value indicative of sensed crankcase pressure in the engine data.

14. An internal combustion engine comprising the engine oil filler cap of any of claims 1 to 13.

15. A machine comprising the internal combustion engine of claim 14.

16. A method for communicating engine data to an electronic device, the method comprising:

sensing a vibration of the internal combustion engine;

determining an engine speed based on the sensed vibration of the internal combustion engine;

storing engine data relating to the determined engine speed in memory; and communicating the engine data to an electronic device via a communications interface.

17. A software program configured to perform the method of claim 16 when executed on a speed determination module.

18. A data logger for mounting on or in an oil filler cap of an internal combustion engine, the data logger comprising

an engine speed determination module;

a vibration sensor coupled to the engine speed determination module, wherein the vibration sensor is configured to sense a vibration of the internal combustion engine; and a memory module coupled to the engine speed determination module; wherein the engine speed determination module is configured to:

determine an engine speed based on a value received from the vibration sensor that is indicative of the sensed vibration of the internal combustion engine.

19. A data logger for mounting on an internal combustion engine and determining a speed of the internal combustion engine, the data logger comprising:

an engine speed determination module;

a vibration sensor coupled to the engine speed determination module, wherein the vibration sensor is configured to sense a vibration of the internal combustion engine;

a memory module coupled to the engine speed determination module; and a communications module coupled to the engine speed determination module, the communications module being suitable for supporting a communications interface with an external electronic device;

wherein the engine speed determination module is configured to:

determine a first engine speed based on the vibration of the internal combustion engine sensed by the vibration sensor over a first period of time;

determine a second engine speed based the vibration of the internal combustion engine sensed by the vibration sensor over a second period of time;

record in the memory module engine data associated with the first engine speed and the second engine speed; and

output to the external electronic device, via the communications module, the engine data.

20. An oil filler cap for fitting to an oil filling port of an internal combustion engine, wherein the oiler filler cap comprises:

a mounting point for the mounting of a data logger configured to determine a speed of the internal combustion engine.

21 . The oil filler cap of claim 20, further comprising:

a cavity within the oil filler cap, wherein the cavity comprises the mounting point for the mounting of the data logger.

22. The oil filler cap of claim 21 , further comprising

a body; and

a removable cover for fixing to the body, wherein the body and the removable cover are configured such that: when the removable cover is fixed to the body, the cavity is a sealed cavity; and

when the removable cover is removed from the body, the cavity is exposed.

23. The oil filler cap of claim 21 or claim 22, further comprising:

a data logger mounted in the cavity within the oil filler cap, the data logger comprising:

a vibration sensor configured to sense a vibration of the internal combustion engine; and

an engine speed determination module coupled to the vibration sensor and configured to determine an engine speed based on the vibration sensed by the vibration sensor; wherein

the vibration sensor and the engine speed determination module are arranged such that, when the oil filler cap is fitted to the oil filling port of the internal combustion engine, the vibration sensor is closer than the engine speed determination module to a crankcase of the internal combustion engine.

24. The oil filler cap of claim 23, further comprising:

a battery mounted in the cavity within the oil filler cap, wherein the battery is arranged such that, when the oil filler cap is fitted to the oil filling port of the internal combustion engine, the battery is further than the vibration sensor and the engine speed determination module from the crankcase of the internal combustion engine.

25. The oil filler cap of claim 24, when dependent on claim 22, wherein when the removable cover is removed from the body, at least the battery is accessible.

26. The oil filler cap of any of claims 23 to 25, further comprising:

a temperature sensor and/or a pressure transducer coupled to the data engine speed determination module, wherein the temperature sensor and/or the pressure transducer are mounted on an external surface of the oil filler cap that is exposed to a crankcase of the internal combustion engine when the oil filler cap is fitted to the oil filling port of the internal combustion engine.