Apparatus and Method for Starter RPM Detection

• US 20100101312A1
• Filed: 01/04/2010
• Published: 04/29/2010
• Est. Priority Date: 12/20/2002
• Status: Active Grant

• Current Assignee: SPX Corporation
• Original Assignee: SPX Corporation
• Inventors: Raichle, Kurt
• Granted Patent: US 7,937,993 B2
• Time in Patent Office: Days
• US Class Current: 73/114.620
• CPC Class Codes: F02N 11/10 Safety devices F02N11/08 takes precedence
• CPC Class Codes: F02N 11/14 Starting of engines by means of electric starters with external current supply F02N11/12 takes precedence
• CPC Class Codes: F02N 2200/041 Starter speed
• CPC Class Codes: F02N 2200/044 Starter current
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: H02P 7/0094 wherein the position is detected using the ripple of the current caused by the commutator

Abstract

An engine starter motor tester applies power to a motor under test at the level normally applied while that motor is installed in a vehicle and monitors the ripple in the driving current. The ripple rate, scaled by the number of windings used in the construction of the motor, provides a direct reading of the shaft speed of the unloaded motor. This number allows a valid inference concerning the state of health of the motor, and is more certain than an estimate for an unloaded motor based on operator experience and motor “sound”. A complete test apparatus includes a stored lookup table, allowing the user to key in a product brand and model number and read directly both the RPM and the test apparatus'"'"'s rating of the motor under test, expressed in terms such as percentage of life remaining.

Claims

1. An apparatus for performing vehicle engine starter motor testing tasks, comprising:

means for applying suitable DC power to vehicle engine starter motors;

means for applying control signals to starter motors;

means for sensing the current level drawn by said starter motors;

means for detecting in the sensed starter motor current level pulsation attributable to addition and removal of individual armature windings from the power circuit as the motor'"'"'s brushes make and break contact with individual segments of the motor'"'"'s commutator;

means for converting detected pulses into a pulse rate indication; and

means for displaying as an output the sensed and scaled RPM of the starter motor under test.

2. The apparatus of claim 1, further comprising:

means for accepting AC input power from public utility AC mains;

means for converting incoming AC input power to DC at a voltage and current level suitable for testing starter motors.

3. The apparatus of claim 1, further comprising:

means for establishing electrical connection between the powering means and the motor being tested.

4. The apparatus of claim 1, further comprising:

means for adjusting the pulse rate indication based on properties of the particular model of the starter motor under test in order to translate the pulse rate indication of the starter motor to RPM.

5. A method for performance of starter motor testing tasks, comprising the following steps:

converting incoming AC input power to DC at the range of levels of voltage and current required for operating vehicle engine starter motors;

applying the DC so developed to the starter motor under test;

sensing the average and transient current of the power applied to the starter motor under test;

converting the ripples in the sensed current level to a ripple rate;

scaling the ripple rate signal based on the motor design to yield an effective motor armature RPM value;

displaying the effective RPM value in human-readable form; and

displaying a summary indication of the condition of the starter motor under test.

6. The method of claim 5, further comprising:

providing electrical connectivity to integrate the starter motor testing method and the starter motor under test.

7. The method of claim 5, further comprising:

scaling the ripple rate signal based on the gear reduction characteristic of the starter motor under test to yield an effective output shaft RPM value.

8. A system for performing starter motor testing tasks, comprising:

a power supply configured to convert incoming AC power to DC at a range of levels suitable for representative vehicle engine starter motors;

a power application arrangement to apply DC at a suitable level to a vehicle engine starter motor;

a sense circuit configured to detect the current draw while the starter motor is running at an applied voltage at which it was intended to be operated;

a differentiation circuit configured to sense ripple in the sensed motor current and convert that signal to a motor winding rate;

a scaler circuit configured to correct the detected rate according to the properties of the starter motor under test, including number of rotor windings; and

an output section configured to provide an interface to a user, particularly providing an RPM indication.