VEHICLE ODOMETER USING ON BOARD DIAGNOSTIC INFORMATION

SPECIFICATION

Field of the Invention

The invention relates to apparatuses and methods for providing odometer information.

Background of the Invention

Odometers indicate distance traveled by vehicles. Odometers are typically mechanical or electrical. Mechanical odometers utilize a system of gears. A gear engages the output shaft to the vehicle transmission. As the vehicle moves, the gear is turned. The gear rotates a cable contained in a flexible sheath. The cable is connected to the odometer indicator, which is a series of dials turned by gears. Thus, for each predetermined number of cable revolutions, the lowest number dial on the odometer will turn to indicate distance traveled. The lower dial will turn the next place dial after a predetermined number of revolutions and so on.

Electrical odometers have a toothed wheel mounted to the transmission output shaft. A magnetic sensor produces a pulse for each tooth passing by. Alternatively, a slotted wheel with an optical sensor to detect the slots and produce a corresponding pulse may be used. The distance the vehicle travels between pulses is known. The electrical odometer counts the pulses to determine the overall distance traveled by the vehicle.

Vehicle odometers have indicators mounted on the dashboard inside the passenger compartment. The driver can easily see the odometer indication.

Obtaining automatic odometer readings, such as for use in an automated system, is difficult.

Vehicle odometer readings are useful in determining when repair or service to a vehicle is required. For example, oil changes, tire rotation and brakes are all serviced according to the odometer reading of the vehicle. As a further example, engine oil may need to be changed every few thousand miles.

Automated systems require the automatic acquisition of odometer readings. Automated systems allow maintenance tasks to be flagged and scheduled based on usage of a vehicle.

Prior art odometers are present on vehicle dashboards and are easily readable by a person sitting in the passenger compartment of a vehicle. However, obtaining odometer readings automatically, such as for use in an automated system, is difficult. One way is to use a visual system that reads the odometer indicator on the dashboard. For example, a mechanical odometer indicator could be read by a visual system. However, such a system is complicated and expensive. Electrical odometers could be tapped into. However, tampering with or altering an odometer circuit is illegal or discouraged. Because odometer readings affect the value of the vehicle, the integrity of those readings and the circuitry must be maintained. Still another way involves placing sensors in the transmission or on the driveshaft to obtain an odometer measurement independently of the vehicle odometer. However, this

involves substantial installation skill and expense and requires calibration. Furthermore, the sensors require service.

Summary of the Invention

It is an object of the present invention to automatically provide odometer readings for a vehicle.

It is another object of the present invention to provide automatic odometer readings for a vehicle in such a way that does not affect the integrity of the existing on-board odometer.

The present invention provides a vehicle that comprises an engine and a transmission. There is a vehicle speed sensor and a first processor with an input connected to the vehicle speed sensor. The first processor has an output that provides the vehicle speed. A first odometer has an indicator in a passenger compartment of the vehicle. A second odometer comprises a second processor. The second processor has an input of the vehicle speed from the first processor. The second odometer comprises an integrator that operates on the vehicle speed and provides an output of distance traveled by the vehicle.

In accordance with one aspect of the present invention, the first processor comprises an electronic control module that controls the engine.

In accordance with another aspect of the present invention, the first processor output of vehicle speed is independent of the first odometer.

In accordance with another aspect of the present invention, the integrator comprises adjustable sampling intervals of the vehicle speed.

In accordance with still another aspect of the present invention, a transceiver is connected to the second processor output.

The present invention provides a vehicle odometer that comprises a vehicle speed sensor. A first processor comprises an input that is connected to the vehicle speed sensor and an output that provides instantaneous vehicle speed. The first processor has another output that controls the function of an engine. A second processor has an input that is connected to the first processor output. There is also a second processor output. The second processor samples the instantaneous vehicle speed and integrates the sampled vehicle speed to determine the distance traveled by the vehicle. The second processor provides the distance traveled at the second processor output.

In accordance with another aspect of the present invention, the second processor changes the frequency of sampling the instantaneous vehicle speed according to the vehicle speed.

In accordance with another aspect of the present invention, a transceiver is connected to the second processor output.

The present invention also provides a method of determining distance traveled by a vehicle. The operation of an engine in the vehicle is controlled as the vehicle travels. Diagnostic information on the operation of the engine is provided. The diagnostic information comprises vehicle speed. The vehicle speed is sampled and then it is integrated to determine the distance traveled by the vehicle.

In accordance with one aspect of the present invention, the step of sampling the vehicle speed further comprises sampling the vehicle speed at changing intervals of time that correspond to the vehicle speed.

In accordance with still another aspect of the present invention, the distance information is transmitted to a location off of the vehicle by a wireless communications link.

In accordance with still another aspect of the present invention, an odometer is provided in the passenger compartment of the vehicle. The odometer is independent of the steps of sampling and integration.

Brief Description of the Drawings

Fig. 1 is a schematic diagram showing a vehicle and the apparatus of the present invention, in accordance with a preferred embodiment.

Fig. 2 is a block diagram of the apparatus of the present invention.

Fig. 3 illustrates trapezoidal integration using moderate time intervals.

Fig. 4 illustrates trapezoidal integration using smaller time intervals than in Fig. 3.

Fig. 5 illustrates varying the sample rate according to vehicle speed.

Description of the Preferred Embodiment

Fig. 1 shows a vehicle 11 having a body or chassis 13, an engine 15 and wheels 17. The engine can be an internal combustion engine, an electric motor, etc. The engine includes a transmission 16. The transmission 16 drives or powers the wheels 17 (either the front wheels or the rear wheels).

An odometer 19 provides information on the distance traveled by the vehicle. The odometer 19 can be of the mechanical type, which utilizes a gear at the transmission 16, a flexible cable, and an indicator with geared dials. The indicator is located in the passenger compartment. Alternatively, the odometer 19 can be of the electrical type, which uses a sensor located at the transmission 16 and an indicator in the passenger

compartment. The odometer sensor could be a toothed wheel with a magnetic sensor, a slotted wheel with an optical sensor, etc. The indicator can be a visual display such as of the type that displays digits or numbers.

The vehicle also includes a diagnostic computer 21. The odometer 19 and diagnostic computer 21 are conventional and commercially available. Almost all vehicles come equipped with an odometer 19. In the last few years, most if not all vehicles are equipped with a diagnostic computer 21.

The diagnostic computer 21 is of the type found on vehicles. In the preferred embodiment, the computer is of the type OBD-II. which is an on-board diagnostic computer. The computer 21 is also an electronic control module (ECM). The computer 21 measures various parameters such as air intake, air intake temperature, engine speed, vehicle speed, air pressure, etc. These parameters are obtained by sensors. One such sensor is a vehicle speed sensor 22. The computer performs control functions for the engine and also provides diagnostic information on the engine and other vehicle components. The computer 21 provides one or more outputs 20 that control the engine 15 so as to maintain engine emissions within acceptable levels. Thus, the computer 21 controls the fuel and air entering the engine cylinders under a variety of operating conditions such as temperature, speed, load. etc. The computer 21 has an output, or diagnostic, port 23 that provides data to a reader or scanner console. The output port 23 is typically a connector located under the dashboard or under the hood. Currently, there are three basic protocols used for data transfer from the output port 23. One such protocol uses ISO 9141 circuitry. Another uses SAE J1850 VPW (Variable Pulse

Width Modulation). Still another uses SAE Jl 850 PWM (Pulse Width Modulation). A mechanic who is working on an engine accesses the output port 23 and obtains information on the engine operation through fault codes. The present invention can be utilized with all types of protocols and oη-board diagnostic computers or electronic control modules.

The vehicle speed sensor 22 provides speed signals to the computer 21. The computer 21 provides instantaneous vehicle speed at the output port 23. Instantaneous vehicle speed can be used to diagnose a problem with the operation of the engine. In addition, vehicle speed may be used to control other functions, such as torque converter lockup, and other control modules, such as the anti-lock brake system.

The vehicle speed sensor 22 measures transmission or transaxle output speed or wheel speed. The vehicle speed sensor 22 can be mounted in or adjacent to the transmission or transaxle and is connected directly to the computer 21. Alternatively, an intermediate module, such as a combination meter, can be connected between the vehicle speed sensor 22 and the computer 21. On a vehicle equipped with an anti-lock brake system (ABS), an ABS computer is intermediate the speed sensors 22 in the wheels and the computer 21.

The vehicle speed sensor 22 can be of various types. For example, the sensor can be of the pickup coil type, the magnetic resistance element type or the reed switch type. The pickup coil type utilizes variable reluctance and has a permanent magnet, a yoke and a coil. The sensor is mounted close to a toothed wheel. A voltage pulse is indicated in the coil each time a tooth passes by the sensor. The magnetic resistance element type uses a magnetic ring that rotates with the output shaft. The sensor

senses the changing magnetic field and produces a sinusoidal wave that is converted into a digital wave. The reed switch type of sensor utilizes a speedometer cable. A magnet is mounted to the cable. As the cable rotates, the magnet opens and closes the contacts of an adjacent reed switch. In all of these sensor types, speed is determined by the frequency of pulses.

The present invention provides an apparatus 31 that utilizes the vehicle speed data from the computer 21 to provide odometer measurements and readings in a manner that can be automatically transferred from the vehicle. The apparatus 31 is located on the vehicle 11 and is connected to the output port 23 of the computer.

The apparatus 31 , shown in Fig. 2, has a processor, or computer, 33, memory 35, an input device 37 and a transceiver 39. The memory 35 can be flash RAM (Random Access Memory) or some other storage device. The transceiver 39 provides communication between the vehicle 11 and a data collection site, which is located off of the vehicle. In the preferred embodiment, the transceiver 39 is wireless. Alternatively, data collection can be obtained from the apparatus 31 by other means, such as a cable connected to a reader or scanner console.

The apparatus 31 monitors the instantaneous speed of the vehicle provided at the computer output port 23. Vehicle instantaneous speed is a generic parameter available from the on-board diagnostic computer 21. The present invention samples the instantaneous speed of the vehicle and integrates the sampled speed over time to determine the distance traveled by the vehicle. The distance, or odometer reading, is then provided externally of the vehicle by way of the transceiver 39.

In the preferred embodiment, the distance traveled by the vehicle is determined using the trapezoidal method of integration, which breaks the speed into a series of small rectangular portions, the volume of which is distance. Fig. 3 illustrates this. The distance traveled by the vehicle is determined for each sample time and these distances are then added together to determine total distance traveled. The preferred embodiment uses the equation below:

totalmiles x lθ conversion/actor

where

M= # of calculations,

N= # of samples,

A = # of calculations per sample, speedsample = measured speed in km/h,

. _ samplerate (1/ s&c ) x 3600 ( sec /hr) x 1.609344 (km/mile) conversionfactor = - - ^! - ^{! J 10}

For a sample rate of 2 times per second, conversionfactor = 2 x 3600 x 1.609344 í 10 « 1159

Fig. 3 illustrates the technique using intervals of time sampling that are of relatively moderate interval lengths. The instantaneous speed 51 is sampled 53 periodically in time. The distance is the time interval multiplied by the speed over that interval. The distances are added together to obtain the odometer reading.

Fig. 4 illustrates the technique using shorter intervals of sampling time of the vehicle speed. This is more accurate in determining odometer measurements but requires more processing capability of the computer 33.

The invention can change either the sampling time of the vehicle speed or the determination of the odometer measurement for each sample speed, depending on the travel history of the vehicle. For example, if the vehicle is traveling on a highway, the speed is unlikely to change in a significant manner. Therefore, the computer 33 detects a relatively constant speed and can choose to make the odometer measurement less frequently.

Changing the sampling time of the vehicle speed is illustrated in Fig. 5. In Fig. 5, the vehicle undergoes two periods of speed. In an early period 61, the vehicle accelerates. In the next and later period 63, the vehicle travels at a relatively constant speed. In the early period 61 of acceleration, the sampling time 65 is relatively short. Thus, more samples per unit time are taken as the speed changes. In the later period 63 of relatively constant speed, the sampling time 67 is increased. Thus, fewer samples per unit time are taken as the speed stays relatively constant.

The sampling speed is set according to the change in vehicle speed. The computer 33 determines if the vehicle speed is changing by at least a predetermined amount. This is accomplished by comparing the vehicle speed samples for a number of samples. For example, if the speed over the last five samples changes by one kilometer per hour (kph), then the sampling speed is changed by a set amount. Varying the sampling speed allows computer 33 capability to be conserved.

The vehicle speed is provided as an input to the computer 33 by way of the input device 37. The computer 33 performs its processing and stores data, whether speed data or odometer data, in memory 35. The computer 33 periodically adds the distance measurements together to obtain total distance traveled. This adding can occur with each distance measurement, or after a predetermined number of time intervals or samplings has occurred, during relatively slow sampling rates 67 or periods (which is when the computer 33 has available processing capability), or after the vehicle has stopped moving for some period of time, or after the engine has been turned off.

When the vehicle travels once again, whether by restarting the engine or releasing the brake and so on, subsequent measurements are added to the odometer reading.

The odometer reading is transferred out of the apparatus 31 and off of the vehicle 11 by the wireless transceiver 39. A communications link between the transceiver 39 and a reader is established and the odometer information is then transferred to the reader. The apparatus 31 continues to accumulate odometer readings. Alternatively, the odometer measurements can be acquired through a wired connection, such as through a connector or other output device.

The present invention has several advantages. The apparatus 31 is easy and inexpensive to install, particularly in the aftermarket. Most, if not all vehicles, come equipped with an on-board computer 21. The apparatus 31 is simply connected to the output port 23 of the on-board computer 21 and to an electrical power supply of the vehicle. There is no need to connect sensors to the transmission or the driveshaft, as required by prior art systems. Nor is there any need to tie into the existing

odometer 19. Thus the integrity of the odometer 19 continues to be maintained. The odometer 31 of the present invention is independent of the dashboard odometer 19 in the sense that the odometer 31 does not tap into or splice into any odometer circuitry. The odometer 19 uses an existing output port 23.

Furthermore, calibration is not required as it is with prior art systems. While the odometer reading of the apparatus 31 will probably not be absolutely accurate, it is accurate when compared to the dashboard odometer 19. For example, if the wrong size tires are installed on the vehicle, the speedometer will be inaccurate, thereby affecting the accuracy of the dashboard odometer 19, as well as the apparatus 31. Nevertheless, the apparatus 31 would continue to match the dashboard odometer 19.

The foregoing disclosure and showings made in the drawings are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense.