GB2303218A

GB2303218A - Portable dynamometer

Info

Publication number: GB2303218A
Application number: GB9513960A
Authority: GB
Inventors: Michael Andrew George; David John Palmer
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-07-08
Filing date: 1995-07-08
Publication date: 1997-02-12
Also published as: GB9513960D0

Abstract

A measured braking force is applied to a spinning disk 10 and the angular velocity of the connected shaft 11, itself connected directly to the crank shaft of the engine to be measured, calculated. The applied braking force is measured by the displacement of a linear position sensor 15, and the angular velocity of the rotating shaft is measured by the pulses from an optical sensor being processed by a microcontroller. The microcontroller calculates from these two values a third value for the instantaneous power output and sends this value, along with the corrresponding value for rpm, to a display. Once the engine is stalled or stopped the value for the greatest encountered horsepower and the corresponding rpm is displayed.

Description

PORTABLE ENGINE POWER OUTPUT COMPARATOR This invention relates to a portable engine power output comparator.

Dynamometers are mechanisms that measure the precise power output of any engine at specific speeds as a component of braking torque and angular momentum. There are various methods of applying and measuring these including the well known Prony brake and the use of a variable gap water brake.

Dynamometers of these and other sorts are, however, extremely heavy and expensive pieces of Industrial Equipment quite unsuited for the testing of power outputs of engines away from such a facility.

According to the present invention there is provided the means for "on the spot" testing of engine power outputs, for example by the side of a race circuit, where it is required that the comparison between two similar engines can be made, perhaps for the selection of an engine for a race or to see how the performance is changing, quickly and easily.The selection of a disk brake makes the possibility of miniaturising the dynamometer possible and allows the applied braking torque to be varied to keep the engine speed at certain speeds for investigåting, while an imbedded microcontroller circuit acts as a weighing unit with on chip analogue to digital conversion of the signal from a linear position sensor measuring a spring's displacement, itself a component of applied force, offering measuring and display flexibility such that the design is easily modified for various applications where it is more satisfactory to measure and compare power outputs without the need to take an engine to a specialist.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing.

Figure 1 shows in elevation the method of braking within the unit Figure 2 shows in plan the method of braking within the unit Figure 3 shows the swinging arm compressed Figure 4 shows in perspective the exterior of the unit Referring to the drawing the unit comprises of a disk 10 connected to a rotating shaft 11 which is directly linked to the engine being tested by chain or other method. The calliper disk brake 12 acts on the rotating disk when applied manually via hydraulic, pneumatic or direct actuation and the reactive force on the brake pads 13 tends to force the braking arm 14 downwards. This motion is resisted by a spring 22 with linear characteristics and hence the displacement and voltage output of the linear position sensor 15 are dependant upon the applied braking force.The value taken from this sensor is fed into the PIC microcontroller 19 together with the angular velocity dependant pulsed signal from the opto switch 16 caused by the rotation of the shaft encoder 17 connected to the rotating shaft 11. The result of the two signals is converted to give an instantaneous value for Horsepower at any speed and this is displayed along with the calculated value for rpm (revolutions per minute) on the backlit LCD display 18. The highest value of engine power output is constantly updated throughout the test and when the revs drop below a programmed threshold the micro-controller senses that the test is finished and displays this value of maximum power output and at what rpm it occurred.

The operating cycle for the unit is therefore: Attach the unit to the engine Run the engine at full speed Apply the brake Take spot values for desired rpm Stall or stop the engine Read off maximum power and speed

Claims

CLAIMS 1 A portable engine power output comparator comprising sprung swinging arm disk brake, microcontroller, linear position sensor, rotary speed sensor and display.
2 A portable engine power output comparator as claimed in Claim 1 wherein means are provided for direct connection to the chassis of a test vehicle such that engine testing could proceed without the removal of the engine from the chassis.
3 A portable engine power output comparator as claimed in Claim 1 wherein means are provided for direct connection of the engine to be tested to the power output comparator or of the power output comparator to the engine.
4 A portable engine power output comparator as claimed in Claim 3 wherein a separate bench arrangement allows the engine that is being tested to be removed from its usual position and bench tested.
5 A portable engine power output comparator as claimed in Claim 1 or Claim 2 or Claim 3 or Claim 4 wherein the provision is made for the connection of a computer to the unit for the downloading of information from the unit such that it may be displayed and compared graphically or otherwise on the computer.
6 A portable engine power output comparator substantially as described herein with reference to figures 1-4 of the accompanying drawing.