Snap-on Technologies, Inc.

Snap-on Tools Corporation

Snap-on Inc.

Michael B Meeker

Craig F Govekar

Michael C Putrow

James R Piehl

Gary D Jonker

John C Sniegowski

Dennis M Mutzabaugh

Dean P Pfefferle

Larry G Moller

Robert D DeCarlo

Nicolaas M J Stoffels

Ronald M J Lammers

Gary S Wollert

Tyrone J Moritz

Thomas Loewe

Ross A Niemi

An engine diagnostic system is provided that enables a service technician to evaluate engine cylinder contribution to output power. The service technician couples one or more signal leads to the vehicle's battery, alternator, or accessory receptacle (e.g., cigarette lighter receptacle) to provide an alternator output signal to a signal analyzer. The signal analyzer processes the alternator output signal to generate an engine signature, which represents engine cylinder contribution to engine output power.

Determining engine cylinder contribution from indexed engine data

A method and system for discharging refrigerant, such as carbon dioxide, from an air conditioning system. The discharge rate of the refrigerant from the air conditioning system is controlled by a discharge rate controller, even as refrigerant pressure at the system input varies. By maintaining discharge rate at a controlled value, the discharge time of the refrigerant from the air conditioning system is reduced.

Arrangement and method for controlling the discharge of carbon dioxide for air conditioning systems

Method and apparatus for displaying ignition coil waveforms. The method includes disposing a plurality of capacitive elements adjacent a plurality of coil-over-plug ignition coils. Signals detected by the capacitive elements are supplied to an adapter in which signal gain, polarity, and range are selected according to a particular vehicle tested, and displayed.

Ignition signal pickup interface box

In a refrigerant recycling system non-condensables are purged from a recovery vessel which stores refrigerant recovered from a vehicular refrigeration system. A programmed controller controls operation of a purge valve for purging to atmosphere non-condensables in the recovered refrigerant in accordance with a purge routine, wherein the temperature in the recovery vessel is measured, and a look-up table is consulted to ascertain a target pressure corresponding to the measured temperature plus an offset, and the pressure in the recovery vessel is measured. If the measured pressure exceeds the target pressure, the purge valve is opened until the measured pressure drops to the target pressure. Immediately after a recovery operation, the purge routine is operated to purge the vessel to a target pressure based on an offset of 1&deg; F. and, at a later time, after the vessel has cooled, the purge routine is operated to purge the vessel to a target pressure based on an offset of zero.

Non-condensable purge technique using refrigerant temperature offset

An automatic refrigerant handling apparatus has a compressor pump for withdrawing a refrigerant from an associated refrigeration system to be serviced, a condenser for liquefying the refrigerant and a storage vessel for storing the recovered refrigerant, the compressor pump also being capable of evacuating the refrigeration system to a first refrigeration system pressure. The apparatus has a connection jack for receiving a connector of an associated optional vacuum pump, the connector including a jumper which interconnects two terminals on the jack when the vacuum pump is connected so that the control circuitry of the apparatus can recognize the presence of the vacuum pump, whereupon the program routine of the control processor utilizes the vacuum pump instead of the compressor pump to draw a vacuum on the associated refrigeration system.

Refrigerant recycling system with automatic detection of optional vacuum pump

A breakout lead includes a length of insulated conductor having a bare uninsulated portion, and an insulating tubular sleeve coaxially and frictionally fitted around said insulated conductor and slidably movable therealong for covering and uncovering the bare insulated portion. Male and female terminals are respectively connected to the ends of the conductor length and are preferably covered by insulating boots.

Sensor breakout lead

A calibrating pickup circuit detects, using primary and secondary pickups, the primary and secondary voltages of an ignition coil of known turns ratio. The pickup circuit includes a programmable gain amplifier, responsive to the detected secondary voltage waveform signal and to a gain control feedback signal for generating an amplified secondary voltage waveform signal wherein the feedback signal has an initial predetermined value in calibration mode and has a calibration value in signal monitor mode. A waveform multiplexing circuit is selectively operable in calibration mode to alternately sample the primary and the amplified secondary voltage waveform signals over a predetermined period to generate a single interlaced waveform signal. Waveform comparison is then performed by evaluating the single interlaced waveform signal and a secondary-to-primary ratio calculated representative of the signal strength difference between analogous portions of the primary and the amplified secondary voltage waveform signals A calibration value is then determined on the basis of the secondary-to-primary ratio and the known turns ratio of the ignition coil.

Automatic calibration for a capacitive pickup circuit

A manifold absolute pressure (MAP) sensor emulator is used to emulate the operation of a properly functioning MAP sensor of the type under test. The test involves breaking the pneumatic connection between the vacuum hose from the intake manifold and the MAP sensor input, and breaking the electrical connection between the MAP sensor output and the vehicle on-board computer. The vacuum hose is instead connected to a vacuum probe input of the emulator and the electrical connection to the on-board computer is also connected to the emulator. Thus, the emulator is connected in place of the MAP sensor, and software in the emulator is programmed to provide a voltage or frequency output corresponding to various vacuum levels of a particular MAP sensor. Thus, the emulator can emulate the sensor and, if the engine operates properly in this mode, it indicates that the MAP sensor was bad, and, if not, it indicates that the problem may be elsewhere. The emulator can be programmed to emulate the MAP sensors of different automobiles.

Manifold absolute pressure sensor emulator

A digital engine analyzer has an oscilloscope display and is controlled by microprocessors operating under menu-driven stored program control. The analyzer receives analog input signals from an engine being analyzed and calculates and display spark plug burn time information derived from a single analog input signal, the data being displayed in both numerical and bar graph form. The measured burn time is the time that the ignition voltage signal is above a predetermined threshold level which is greater than the amplitude of the ringing portion of the ignition voltage signal.

Digital engine analyzer

A digital engine analyzer has an oscilloscope display and is controlled by microprocessors operating under menu-driven stored program control. The analyzer receives analog input signals from an engine being analyzed. The engine calculates and displays real-time cylinder time balance information by calculating for each cylinder the cylinder time period from the firing of that cylinder to the firing of the next cylinder, storing the cylinder time values for each cylinder for a number of successive engine cycles, averaging the time period values for each cylinder over that number of engine cycles, calculating an overall average of the cylinder averages, calculating the percentage difference between each cylinder average and the overall average and then displaying the percentage differences in both numerical and bar graph form along with the overall average value.

A digital engine analyzer has an oscilloscope display and is controlled by microprocessors operating under menudriven stored program control. The analyzer receives analog input signals from an engine being analyzed. Peak capture circuitry permits the display of a full cylinder period of a waveform, even though it contains very high frequency portions, by selectively switching between normal and high resolution modes. The circuitry samples the analog waveform at a very high rate and selects samples for display at a much slower display rate. The circuitry captures and stores the highest magnitude sample in each cylinder cycle by storing each sample only if its magnitude exceeds that of the previously stored sample. In the normal mode, at each display clock pulse the most recent sample is selected for display, irrespective of its magnitude. In the high resolution mode the stored peak value is selected for display at each display clock pulse.

Waveform peak capture circuit for digital engine analyzer

A digital engine analyzer has an oscilloscope display and is controlled by microprocessors operating under menu-driven stored program control. The analyzer receives analog input signals from an engine being analyzed, digitizes the signals, captures the digital peak ignition voltage values for each cylinder and stores only these values for each cylinder over a number of successive engine cycles, and then simultaneously displays all the stored values for any one cylinder over a number of engine cycles to provide a historical display. Each peak value is stored twice and displayed twice to provide width to the value display and effectively produce a bar graph-type display.

A digital engine analyzer has an oscilloscope display and is controlled by microprocessors operating under menu-driven stored program control. The analyzer receives analog input signals from an engine being analyzed. The analyzer is provided with a scanner interface, so that a scanner designed to read data from a vehicle on-board computer, can transfer this data to the analyzer for display on the analyzer oscilloscope. The analyzer processor, when operating in the scanner interface mode, operates under stored program control to reconfigure analyzer keyboard and soft key functions to duplicate scanner control functions, so that the scanner control functions can be effected from the analyzer.

Growing community of inventors

Kenosha, WI, United States of America

Michael B Meeker