Abstract:
The present invention is directed to an apparatus for testing a plurality of on/off solenoid valves and a plurality of proportional solenoid valves of an automotive transmission. The apparatus includes an on/off valve switch for each of the on/off solenoid valves and a series of preset current switches for each of the proportional solenoid valves. An on/off solenoid circuit is electrically connected to the on/off valve switches and includes a plurality of outputs for connection to the on/off solenoid valves. In response to actuation of the on/off valve switches, the on/off solenoid circuit is operable to generate electrical actuation signals for transmission through the outputs to the on/off solenoid valves, respectively. Proportional solenoid circuits are electrically connected to the series of the preset current switches, respectively. Each proportional solenoid circuit has an output for connection to one of the proportional solenoid valves. Each proportional solenoid circuit is operable in response to selective actuation of the associated series of preset current switches to generate and transmit electrical preset current signals to one of the proportional solenoid valves through the output, wherein said preset current signals have different preset current levels.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention is directed toward automotive transmission testing and, more particularly, toward an apparatus for testing on/off solenoid valves and proportional or linear solenoid valves of an automotive transmission.  
         [0002]     An automatic transmission for an automotive vehicle automatically shifts gears based on certain operating conditions, such as crankshaft speed, accelerator pedal depression, vehicle speed, etc. The shifting of gears is performed by clutches which are actuated by pressurized hydraulic fluid. The supply of hydraulic fluid to the clutches is controlled and regulated by hydraulic circuits that include a number of control devices, such as on-off solenoid valves and proportional solenoid valves. Solenoid valves are electro-mechanical devices that utilize a solenoid to control valve activation. As is well known, a solenoid comprises a coil of wire that is wound around a movable plunger or armature that is at least partially ferromagnetic. When a given amount of current passes through the coil, the coil generates a magnetic field that moves the armature, thereby moving a seat that opens and closes the valve. In an on-off solenoid, the seat may be disposed in only two positions, namely a fully open position and a fully closed position, whereas in a proportional solenoid valve, the seat may disposed in intermediate positions between a fully open position and a fully closed position. In a proportional solenoid, the amount of movement of the armature and, thus, the position of the seat is dependent on the amount of current flowing through the coil. More specifically, the position of the seat is proportionally related to the current.  
         [0003]     In automotive transmissions, an on-off solenoid valve is used to either selectively close a hydraulic circuit to produce a maximum pressure therein, or to open a hydraulic circuit to produce a minimum pressure therein. The engagement and disengagement of a clutch to shift between gears is typically accomplished by moving between maximum and minimum pressures in a hydraulic circuit through the activation and deactivation of on-off solenoid valves. Such on-off solenoid valves are typically referred to as shift solenoid valves. Shift solenoid valves are typically actuated by electrical signals having a voltage in a range between 5 and 18 volts direct current.  
         [0004]     In automotive transmissions, a proportional solenoid valve is used to vary the fluid pressure in a hydraulic circuit. The engagement and disengagement of a start clutch, which controls motive power transmission when a vehicle is started or stopped, is often controlled by varying fluid (oil) pressure in a hydraulic circuit using proportional solenoid valves. Proportional solenoid valves may also be used for shift control and for PH-PL control (pressure high—pressure low). Such proportional solenoid valves are typically controlled by electrical signals having a current varying between 0 and 2 amps.  
         [0005]     In an automotive transmission, solenoid valves are typically mounted to a transmission valve body that includes worm trails and passages through which hydraulic fluid is routed. The transmission valve body and the solenoid valves are disposed inside a transmission case.  
         [0006]     Since defects in the solenoid valve and associated hydraulic circuits will cause an automatic transmission to malfunction, it is important to verify that all solenoid valves and associated hydraulic circuits are operating properly before they are installed in a transmission during the assembly of the transmission. It is also important to be able to identify a defective solenoid and/or associated hydraulic circuit when repairing a malfunctioning transmission. Accordingly, devices for testing automatic transmissions and automatic transmission solenoid valves have been developed. Many of these devices are operable only to test shift solenoid valves. Some of these devices, however, can test both a shift solenoid and a proportional solenoid. For example, U.S. Pat. No. 5,712,434 to Sylvis and U.S. Pat. No. 6,038,918 to Newton each disclose a testing device that can test both a shift solenoid and a proportional solenoid. Each device, however, can only test one shift solenoid or one proportional solenoid at a time. Moreover, in each device, a proportional solenoid is tested by varying the current supplied to coil of the proportional solenoid by manipulating a potentiometer knob. Thus, when testing a plurality of proportional solenoid valves, a considerable amount of time is wasted adjusting the potentiometer knob to produce the various test current levels. Moreover, many of these knob-type potentiometers are not smooth, which can lead to inaccuracies.  
         [0007]     Based on the foregoing, there exists a need in the art for an improved test apparatus for testing shift solenoid valves and proportional solenoid valves of an automatic transmission. The present invention is directed to such a test apparatus.  
       SUMMARY OF THE INVENTION  
       [0008]     In accordance with the present invention, an apparatus is provided for testing a proportional or linear solenoid valve of an automotive transmission. The apparatus includes a plurality of preset current switches and a proportional solenoid circuit electrically connected to the preset current switches and having an output for connection to the proportional solenoid valve. The proportional solenoid circuit is operable in response to selective actuation of the preset current switches to generate and transmit electrical preset current signals to the proportional solenoid valve through the output, respectively. The preset current signals have different preset current levels.  
         [0009]     In accordance with another aspect of the present invention, a variable current switch is electrically connected to the proportional solenoid circuit and a potentiometer is provided for manipulation by an operator. The potentiometer is electrically connected to the proportional solenoid circuit. The proportional solenoid circuit is operable in response to actuation of the variable current switch to generate and transmit an electrical variable current signal to the proportional solenoid valve through the output. The electrical variable current signal has a current level chosen by operator manipulation of the potentiometer.  
         [0010]     In accordance with still another aspect of the present invention, the apparatus is also operable to test an on/off solenoid valve of an automotive transmission. An on/off solenoid circuit is provided and is electrically connected to an on/off valve switch. The on/off solenoid circuit includes an output for connection to the on/off solenoid valve. The on/off solenoid circuit is operable to generate an electrical actuation signal for transmission through the output to the on/off solenoid valve in response to actuation of the on/off valve switch.  
         [0011]     Advantageously, the apparatus of the present invention may, in accordance with another aspect of the present invention, be operable to test a plurality of on/off solenoid valves and a plurality of proportional solenoid valves. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:  
         [0013]      FIG. 1  is a schematic view of a test assembly for testing shift solenoid valves and proportional or linear solenoid valves of an automatic transmission;  
         [0014]      FIG. 2  shows a circuit diagram of connections to operator interface devices on a front panel of a solenoid control module of the test assembly;  
         [0015]      FIG. 3A  shows a diagram of a first portion of a shift solenoid circuit of the solenoid control module;  
         [0016]      FIG. 3B  shows a diagram of a second portion of the shift solenoid circuit of the solenoid control module;  
         [0017]      FIG. 4  shows a diagram of a first portion of a proportional solenoid circuit of the solenoid control module; and  
         [0018]      FIG. 5  shows a diagram of a second portion of the proportional solenoid circuit. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     It should be noted that in the detailed description that follows, identical components have the same reference numerals, regardless of whether they are shown in different embodiments of the present invention. It should also be noted that in order to clearly and concisely disclose the present invention, the drawings may not necessarily be to scale and certain features of the invention may be shown in somewhat schematic form.  
         [0020]     Referring now to  FIG. 1 , there is shown a test assembly  10  for testing four shift solenoid valves  12   a,b,c,d  and four proportional solenoid valves  14   a,b,c,d . It is noted that the proportional solenoid valves are sometimes referred to as linear solenoid valves in the art. The shift solenoid valves  12   a - d  are on/off solenoid valves, each having an armature movable between open and closed positions. The test assembly  10  includes a hydraulic fluid source  16 , a valve test stand  18  and a solenoid control module  20 . The shift solenoid valves  12   a - d  and proportional solenoid valves  14   a - d  may be mounted to a transmission valve body  22 . The valve test stand  18 , the transmission valve body  22 , the shift solenoid valves  12   a - d  and the proportional solenoid valves  14   a - d  are shown in a highly schematic manner.  
         [0021]     The solenoid control module  20  includes a power management circuit comprising a shift solenoid circuit  24  ( FIGS. 3A-3B ) for testing shift solenoid valves  12   a - d  and four proportional solenoid circuits  26  ( FIGS. 4-5 ) for testing proportional solenoid valves  14   a - d , respectively. The power management circuit further comprises a step-down transformer  28  ( FIG. 3A ), which is for connection to a 120 VAC power source and which is operable to drop the incoming voltage to 18 VAC. The shift solenoid circuit  24  and the proportional solenoid circuits  26  are provided on circuit boards, respectively. In the description that follows, only the proportional solenoid circuit  26  for the proportional solenoid valve  14   a  is shown (in  FIGS. 4 and 5 ), it being understood that the proportional solenoid circuits  26  for proportional solenoid  14   b - d  are substantially the same as the proportional solenoid circuit  26  for the proportional solenoid valve  14   a.    
         [0022]     The power management circuit is mounted inside a housing  30  having a front panel  32  with a plurality of operator interface devices mounted thereto. The operator interface devices include a vertical row of four shift solenoid pushbuttons  34   a,b,c,d  and four horizontal rows a, b, c, d of seven proportional solenoid pushbuttons  36 ,  38 ,  40 ,  42 ,  44 ,  46 ,  48  each. The shift solenoid pushbuttons  34   a - d  are latching pushbuttons, while the proportional solenoid pushbuttons  36 - 48  are momentary pushbuttons. At the end of each row a, b, c, or d of the proportional solenoid pushbuttons  36 - 48 , a potentiometer  56  and a digital display  58  are mounted to the front panel  32 . The shift solenoid pushbuttons  34   a - d  are connected into the shift solenoid circuit  24 , while the four rows a-d of proportional solenoid pushbuttons  36 - 48  are connected into the four proportional solenoid circuits  26 , respectively. Each of the shift solenoid pushbuttons  34   a - d  and the proportional solenoid pushbuttons  36 - 48  becomes illuminated upon actuation. The shift solenoid pushbuttons  34   a - d  control the provision of electrical signals to shift solenoid valves  12   a - d , respectively, whereas the rows a-d of the proportional solenoid pushbuttons  36 - 48  control the provision of electrical signals to the proportional solenoid valves  14   a - d , respectively. Each row a, b, c or d of the proportional solenoid pushbuttons  36 - 48  is dedicated to providing an electrical signal with a selected current level to one of the proportional solenoid valves  14   a, b, c , or  d . In each row a, b, c, or d of the proportional solenoid pushbuttons  36 - 48 , the proportional solenoid pushbuttons  36 - 46  are for providing different preset currents for the signal to a proportional solenoid valve  14   a, b, c  or  d , while the proportional solenoid pushbutton  48  is for providing a variable current for the signal to the proportional solenoid  14   a, b, c  or  d . The potentiometer  56  at the end of each row a, b, c or d is operable to select the variable current for the proportional solenoid pushbutton  48 . The display  58  at the end of each row a, b, c or d displays the actual current drawn by the proportional solenoid  14   a, b, c  or  d  associated with the row a, b, c or d.  
         [0023]     Four panel terminal strips  64  and four panel terminal strips  66  are provided on the rear of the front panel  32 . Each panel terminal strip  64  is provided for a shift solenoid  12   a,b,c  or d and a proportional solenoid  14   a,b,c  or d, while each panel terminal strip  66  is for a proportional solenoid  14   a,b,c  or d. For purposes of brevity, only the panel terminal strips  64 ,  66  for the shift solenoid valve  12   a  and the proportional solenoid valve  14   a  are shown in  FIG. 2 , it being understood that panel terminal strips  64 ,  66  for the shift solenoid valves  12   b - d  and the proportional solenoid valves  14   b - d  are substantially the same as the panel terminal strips  64 ,  66  for the shift solenoid valve  12   a  and the proportional solenoid valve  14   a.    
         [0024]     With reference now to  FIGS. 3A and 3B , the shift solenoid circuit  24  includes a terminal strip  68  that is connected to the transformer  28  to receive 18 VAC power therefrom. The terminal strip  68  has output terminals connected to four 3 amp bridge rectifiers  72 ,  74 ,  76 ,  78  with capacitor filters and two 5 amp bridge rectifiers  80 ,  82  with capacitor filters. The bridge rectifiers  72 - 82  are operable to convert the 18 VAC output from the transformer  28  to 18 VDC outputs. The filtered 18 VDC outputs from the bridge rectifiers  72 - 78  are provided to terminal strips  86 ,  88 ,  90 ,  92 , which are respectively connected to terminal strips  96  in the proportional solenoid circuits  26  ( FIG. 4 ) by cables (not shown).  
         [0025]     The 18 VDC filtered output of the bridge rectifier  80  is provided to a voltage regulator  98  ( FIG. 3A ) which drops and regulates the 18 VDC so as to produce a regulated 12 VDC output. The regulated 12 VDC output from the voltage regulator  98  is provided to contacts on relays  100   a,b,c,d  ( FIG. 3B ), which are preferably 16 amp miniature relays with 12 VDC coils. The contacts on relays  100   a - d  are connected to an output terminal strip  102  which is connected by a wiring harness  104  (shown in  FIG. 1 ) to the shift solenoid valves  12   a - d  and the proportional solenoid valves  14   a - d  at the valve test stand  18 . The 18 VDC filtered output of the bridge rectifier  82  is provided to voltage regulators  106 ,  108 ,  110  ( FIG. 3A ). The voltage regulators  106 ,  108  drop and regulate the 18 VDC so as to have regulated 12 VDC outputs, while the voltage regulator  110  drops and regulates the 18 VDC so as to have a regulated 5 VDC output. The regulated 12 VDC outputs of the voltage regulators  106 ,  108  and the regulated 5 VDC output of the voltage regulator  110  are provided to each of the terminal strips  86 ,  88 ,  90 ,  92 . The regulated 12 VDC output from the voltage regulator  106  is provided to fans (not shown) mounted inside the housing  30 , the regulated 12 VDC output from the voltage regulator  108  is provided to the proportional solenoid circuits  26 , and the regulated 5 VDC outputs from the voltage regulator  110  is provided to the digital displays  58  mounted to the front panel  32 .  
         [0026]     With brief reference now to  FIGS. 4-5 , the 12 VDC output from the voltage regulator  108  is provided to terminal strip  96 , which is connected to a terminal strip  112  and thence a terminal strip  114 . The terminal strip  114  is connected by a cable (not shown) to the panel terminal strip  64  (shown in  FIG. 2 ) for the shift solenoid valve  12   a  on the front panel  32 .  
         [0027]     Referring now to  FIG. 2 , the panel terminal strip  64  is connected to the contacts of the shift solenoid pushbutton  34   a  and a phototransistor  118  for lighting the shift solenoid pushbutton  34   a.  12 VDC from the voltage regulator  108  is connected across the contacts of the shift solenoid pushbutton  34   a  such that actuation of the shift solenoid pushbutton  34   a  closes the contacts and generates a 12 VDC “shift high” signal that is supplied to the phototransistor  118  through the terminal strip  114  in the proportional solenoid circuit  26 , thereby lighting the phototransistor  118 .  
         [0028]     Referring back to  FIGS. 3A and 3B , the “shift high” signal is also provided to the coil of the relay  100   a  in the shift solenoid circuit  24  through the terminal strips  114 ,  96  in the proportional solenoid circuit  26  and the terminal strip  68  in the shift solenoid circuit  40 . In this manner, the actuation of the shift solenoid pushbutton  34   a  energizes the coil of the relay  100   a . Energization of the coil of the relay  100   a  closes the contacts of the relay  100   a , thereby providing the regulated 12 VDC from the voltage regulator  98  to the shift solenoid valve  12   a  as an actuation signal  120   a . The actuation signal  120   a  is provided to the shift solenoid valve  12   a  through the terminal strip  102  and the wiring harness  104 . It should be appreciated that selective actuation of the shift solenoid pushbuttons  34   b - d  similarly causes the coils of the relays  100   b - d  to become energized, respectively, and to close their corresponding contacts, thereby providing regulated 12 VDC power as actuation signals  120   b,c,d  to the shift solenoid valves  12   b - d , respectively. The actuation signals  120   a - d  have sufficient current to actuate or “pull in” the armatures of the shift solenoid valves  12   a - d , respectively, to open (or close) the seats of the shift solenoid valves  12   a - d , respectively. Such a pull-in current is typically between 1 and 3 amps and more typically between 1 and 2 amps. The shift solenoid pushbuttons  34   a - d  may be actuated simultaneously to simultaneously actuate the shift solenoid valves  12   a - d.    
         [0029]     Referring now to  FIGS. 4 and 5 , the proportional solenoid circuit  26  for the proportional solenoid valve  14   a  will be described. Once again, it should be understood that the proportional solenoid circuits  26  for proportional solenoid  14   b - d  are substantially the same as the proportional solenoid circuit  26  for the proportional solenoid valve  14   a . The proportional solenoid circuit  26  comprises a switching section  122  (shown in  FIG. 5 ), a voltage regulating section  124  (shown in  FIG. 4 ) and a current regulating section  126  (shown in  FIG. 4 ). The voltage regulating section  124  and the current regulating section  126  determine the current and voltage of an output signal  128  of the proportional solenoid circuit  26  in response to operation of the switching section  122 .  
         [0030]     The voltage regulating section  124  and the current regulating section  126  are connected to the output of a voltage regulator  130 , which, in turn, is connected to the terminal block  96 . The voltage regulator  130  drops and regulates the 18 VDC filtered output of the bridge rectifier  78  so as to produce a regulated 15 VDC output. The output signal  128  of the proportional solenoid circuit  26  is connected to the terminal block  102  in the shift solenoid circuit  24  through the terminal block  96  and the terminal block  86  in the shift solenoid circuit  24 .  
         [0031]     The voltage regulating section  124  includes a voltage regulator  132 , a PNP transistor  134  and an error amplifier  136 . The voltage regulator  132  is connected to the output of the voltage regulator  130  and is operable to produce a positive 5 volt reference voltage output. The output from the voltage regulator  132  is connected through a variable resistor  140  to a non-inverting input of the error amplifier  136 , which is preferably a portion of a quad operational amplifier, such as is commercially available from Semiconductor Components Industries LLC under the trade name LM324. The variable resistor  140  is operable to adjust the voltage of the output from the error amplifier  136 . Resistors  142  and  144  form a voltage divider, which is applied to an inverting input of the error amplifier  136  and which performs output voltage sensing. If the voltage of the output signal  128  is too low, the output of the error amplifier  136  will go positive, thereby applying base current to an NPN transistor  146 . As a result, the NPN transistor  146  pulls base current through the PNP transistor  134 , which causes the current and, thus, the voltage of the output signal  128  to increase. The output of the error amplifier  136  drives in such a way as to keep the two voltages at its inputs in equilibrium. A stabilizing capacitor  148  is connected into a negative feedback loop of the error amplifier  136  to prevent oscillation.  
         [0032]     Preferably, the variable resistor  140  of the voltage regulating section  124  is adjusted to a maximum and the voltage reduction that is necessary to maintain the proper current limiting is managed entirely by the current regulating section  126 . The current regulating section  126  includes a low-value precision resistor  150  connected between the negative voltage output from the contacts of a relay  152  and ground. The resistor  150  is used for sensing current. More specifically, the voltage drop across the resistor  150  produces a voltage signal corresponding to the amount of current of the output signal  128 . This voltage signal is provided to the display  58  through the terminal strip  114  and the panel terminal strip  64  on the front panel  32 . The voltage signal is also provided to a non-inverting input of a current sensing amplifier  156 , which is preferably a second portion of the quad operational amplifier. The current sensing amplifier  156  is configured to produce an output voltage gain of ten times the input voltage. The output of the current sensing amplifier  156  is connected to a non-inverting input of a comparator  158 , which is preferably a third portion of the quad operational amplifier. An inverting input of the comparator  158  is connected to a voltage regulator  160  through a selected one of a plurality of variable resistors or potentiometers  162 ,  164 ,  166 ,  168 ,  170 ,  172  and the potentiometer  56 , which function as voltage dividers. The voltage regulator  160  is connected to the output of the voltage regulator  130  and is operable to produce a positive 5 volt reference voltage output. The 5 volt reference voltage from the voltage regulator  160  is reduced to one of a plurality of different voltage values through the selection of one of the potentiometers  162 - 172  or the potentiometer  56 , as will be discussed further below. The reduced voltage values are voltage setpoint values that correspond to current setpoint values. The potentiometers  162 - 172  are variable resistors that can be adjusted to have different values, and the potentiometer  56  can be manually manipulated to change the resistance of the potentiometer  56 . The potentiometers  162 - 172  are set to produce different preset currents ranging from about 0 to about 1.2 amps.  
         [0033]     As long as the non-inverting input voltage stays lower than the inverting input voltage, the output of the comparator  158  stays low. When the current of the output signal  128  rises to a level which causes the non-inverting input to exceed that of the inverting input, the output of the comparator  158  goes high, thereby applying base current to an NPN transistor  174 . As a result, the NPN transistor  174  pulls the non-inverting input of the error amplifier  136  to ground, which, in turn, stops the draw of base current through the PNP transistor  134 , thereby turning off the output signal  128  until the current of the output signal  128  drops below the current setpoint value determined by the selected one of the potentiometers  162 - 172  or the potentiometer  56 . The rapid switching of the voltage regulating section  124  and the current regulating section  126  holds the voltage of the output signal  128  to a level that, with any given load, maintains the current of the output signal  128  at the current setpoint value. A resistor  178  and a capacitor  180  filter and stabilize the output signal  128 , which is provided to the proportional solenoid valve  14   a  through the output terminal strip  102 .  
         [0034]     The output of the comparator  158  may be connected to a phototransistor  182  through an amplifier  184  so as to light the phototransistor  182  when the comparator  158  goes high, thereby indicating that current limiting is occurring.  
         [0035]     The selection of one of the potentiometers  162 - 172  or the potentiometer  56  to determine a current setpoint value for the output signal  128  is performed through the switching section  122 . The switching section  122  is connected to the proportional solenoid pushbuttons  36 - 48  on the front panel  32  and is operable in response to manipulation of the proportional solenoid pushbuttons  36 - 48  to select one of the potentiometers  162 - 168  or the potentiometer  56  and, thus, a current setpoint value. The switching section  122  is connected to the panel terminal strip  66  on the front panel  32  through a cable (not shown) connected between the panel terminal strip  66  and the terminal strip  112  in the proportional solenoid circuit  26 . As shown in  FIG. 2 , the panel terminal strip  66  is connected to contacts and phototransistors  188 ,  190 ,  192 ,  194 ,  196 ,  198 ,  200  of the proportional solenoid pushbuttons  36 - 48  for the proportional solenoid valve  14   a.    
         [0036]     The switching section  122  includes seven AND gates  204 ,  206 ,  208 ,  210 ,  212 ,  214 ,  216  associated with the seven proportional solenoid pushbuttons  36 ,  38 ,  40 ,  42 ,  44 ,  46 ,  48 , respectively. The AND gates  204 - 216  are connected to the proportional solenoid pushbuttons  36 - 48  through the terminal strip  112  such that the inputs of each AND gate are connected to all of the proportional solenoid pushbuttons, except the proportional solenoid pushbutton with which the AND gate is associated. Thus, for example, the excepted proportional solenoid pushbutton for the AND gate  204  is the proportional solenoid pushbutton  36 . The proportional solenoid pushbuttons  36 - 48  and the AND gates  204 - 216  are interconnected with the 12 VDC from the voltage regulator  108  and ground such that the actuation of a proportional solenoid pushbutton will pull the inputs of the AND gates to which the proportional solenoid pushbutton are connected to ground or “low” states. Thus, the actuation of a proportional solenoid pushbutton will create “low” outputs for all of the AND gates, except for the AND gate that is not connected to the proportional solenoid pushbutton (i.e., the AND gate associated with the proportional solenoid pushbutton), which will be “high”. Thus, actuation of a proportional solenoid pushbutton will result in the AND gate associated with the proportional solenoid having a high output and all of the other AND gates having low outputs.  
         [0037]     The outputs of the AND gates  204 - 216  are connected to a pair of R/S latch circuits  220 ,  222 , each of which is a cross-coupled 3-state CMOS NAND latch circuit having four latches. The latches (R, S) of the R/S latch circuit  220  are associated with the proportional solenoid pushbuttons  36 ,  38 ,  40 ,  42 , respectively, while the latches of the R/S latch circuit  222  are associated with the proportional solenoid pushbuttons, respectively  44 ,  46 ,  48 . For each proportional solenoid pushbutton and its associated latch, the set input (S) of the latch is connected to the proportional solenoid pushbutton and the reset input (R) of the latch is connected to the AND gate associated with the proportional solenoid pushbutton. Each latch is configured such that when the reset input is high and the set input is low, the output of the latch is high, and when the reset input is low and the set input is high, the output of the latch is low. Thus, the actuation of a proportional solenoid pushbutton will result in the output of the latch associated with the proportional solenoid pushbutton going high.  
         [0038]     The outputs Q 0 , Q 1 , Q 2 , Q 3  of the latches of the R/S latch circuit  220  are connected to the gates of N-channel DMOSFETs  226 ,  228 ,  230 ,  232 , respectively, and to the gates of N-channel DMOSFETs  234 ,  236 ,  238 ,  240 , respectively. In addition, the output Q 0  of the R/S latch circuit  220  is connected to the N-channel DMOSFET  244  (shown in  FIG. 4 ). The outputs Q 0 , Q 1 , Q 2  of the latches of the R/S latch circuit  222  are connected to the gates of N-channel DMOSFETs  248 ,  250 ,  252 , respectively, and to the gates of N-channel DMOSFETs  254 ,  256 ,  258 , respectively. The drains of the N-channel DMOSFETs  226 ,  228 ,  230 ,  232 ,  248 ,  250 ,  252  are connected to the phototransistors  188 ,  190 ,  192 ,  194 ,  196 ,  198   200  of the proportional solenoid pushbuttons  36 - 48 , respectively, through the terminal strip  112  and the panel terminal strip  66  on the front panel  32 , whereas the drains of the N-channel DMOSFETs  234 ,  236 ,  238 ,  240 ,  254 ,  256 ,  258  are connected to the coils of relays  260 ,  262 ,  264 ,  266 ,  268 ,  270 ,  272 , respectively, which are preferably 1 amp miniature relays with 12 VDC coils. The drain of the N-channel DMOSFET  244  is connected to the coil of the relay  152 , which is also preferably a 1 amp miniature relay with a 12 VDC coil. Each phototransistor  188 ,  190 ,  192 ,  194 ,  196 ,  198 , or  200  and its associated N-channel DMOSFET  226 ,  228 ,  230 ,  232 ,  248 ,  250 , or  252  are interconnected with the 12 VDC from the voltage regulator  108  and ground such that a “high” signal to the gate of the N-channel DMOSFET causes the N-channel DMOSFET to connect the phototransistor to ground, thereby completing the electrical circuit for the phototransistor and lighting the phototransistor. Similarly, each relay  152 ,  260 ,  262 ,  264 ,  266 ,  268 ,  270 , or  272  and its associated N-channel DMOSFET  244 ,  234 ,  236 ,  238 ,  240 ,  254 ,  256 , or  258  are interconnected with the 12 VDC from the voltage regulator  108  and ground such that a “high” signal to the gate of the N-channel DMOSFET causes the N-channel DMOSFET to connect the coil of the relay to ground, thereby completing the electrical circuit for the coil and energizing the coil. In this manner, a high signal from the output of a latch of one of the R/S latch circuits  220 , or  222 , will light the phototransistor(s) associated with the latch and energize the coil(s) of the relay(s) associated with the latch. Contacts of the relay  152  are connected to the negative voltage line of the output signal  128 , contacts of the relays  260 - 270  are connected to the potentiometers  162 ,  164 ,  166 ,  168 ,  170 ,  172  of the current regulating section  126 , and the contacts of the relay  272  are connected to the potentiometer  56 .  
         [0039]     The potentiometers  162 - 172  and the potentiometer  56  are connected to the contacts of the relays  260 - 272  such that the energization of the coil of one of the relays  260 ,  262 ,  264 ,  266 ,  268 ,  270  or  272  will connect one of the potentiometers  162 ,  164 ,  166 ,  168 ,  170 , or  172  or the potentiometer  56  to the inverting input of the comparator  158 . More specifically, energization of the coil of the relay  260  will connect the potentiometer  162 , energization of the coil of the relay  262  will connect the resistor  164 , energization of the coil of the relay  264  will connect the resistor  166 , energization of the coil of the relay  266  will connect the resistor  168 , energization of the coil of the relay  268  will connect the resistor  170 , energization of the coil of the relay  270  will connect the resistor  172  and energization of the coil of the relay  272  will connect the potentiometer  56 . Energization of the coil of the relay  152  disconnects the negative voltage line of the output signal  128 , thereby turning off the output signal  128 , which corresponds to a zero current.  
         [0040]     In summary, for each proportional solenoid circuit  26  and its associated row a, b, c, or d of the proportional solenoid pushbuttons  36 - 48 , selective actuation of the proportional solenoid pushbuttons  38 - 46  provides the output signal  128  of the proportional solenoid circuit  26  with preset currents ranging from above 0 amps to about 1.2 amps; actuation of the proportional solenoid pushbutton  36  provides the output signal  128  of the proportional solenoid circuit  26  with a current of zero amps since the actuation of the proportional solenoid  36  pushbutton energizes the coil of the relay  152 ; and actuation of the proportional solenoid pushbutton  48  provides the output signal  128  of the proportional solenoid circuit  26  with a variable current that is determined by manual manipulation of the potentiometer  56 . The four proportional solenoid circuits  26  may simultaneously provide four output signals  12 , respectively, to the proportional solenoid valves  14   a - d , respectively, wherein the four output signals  12  have the same or different currents.  
         [0041]     Referring back to  FIG. 1 , the solenoid control module  20  is used to test the operation of the shift solenoid valves  12   a - d  and the proportional solenoid valves  14   a - d  in the context of the operation of the transmission valve body  22 . The shift solenoid valves  12   a - d  and the proportional solenoid valves  14   a - d  are connected to the solenoid control module  20  by the wiring harness  104 , while the transmission valve body  22  is hydraulically connected to the valve test stand  18  through a hose network  280 . The valve test stand  18  is connected by a hose  282  to the hydraulic fluid source  16  to receive pressurized hydraulic fluid (oil) therefrom. The valve test stand  18  controls the provision of pressurized hydraulic fluid to the transmission valve body  22  and monitors the various outlet pressures of the transmission valve body  22  in response to the provision of the output signals  120   a - d ,  128  from the solenoid control module  20 . The outlet pressures are displayed on gauges  284 .  
         [0042]     Although the solenoid control module  20  is shown testing a transmission valve body  22  with four shift solenoid valves  12   a - d  and four proportional solenoid valves  14   a - d , it should be appreciated that the solenoid control module  20  can also be used to test other transmission valve bodies having different combinations of shift solenoid valves and proportional solenoid valves. For example, in one particular application, the solenoid control module  20  is used to test a transmission valve body having the four shift solenoid valves  12   a - d  and only three proportional solenoid valves  14   a,b,c.    
         [0043]     It should also be appreciated that the solenoid control module  20  is not limited to testing the shift solenoid valves  12   a - d  and the proportional solenoid valves  14   a - d  in the context of the operation of the transmission valve body  22 . Instead, the solenoid control module  20  can be used to test the shift solenoid valves  12   a - d  and the proportional solenoid valves  14   a - d  before they are installed in the transmission valve body  22 . In this application, the shift solenoid valves  12   a - d  and the proportional solenoid valves  14   a - d  are directly connected by hoses to the valve test stand  18  or other test device for the receipt and discharge of pressurized hydraulic fluid.  
         [0044]     It should further be appreciated that the present invention is not limited to testing four or less shift solenoid valves and four or less proportional solenoid valves. Rather, the apparatus and methodology taught by the present invention may be expanded by those skilled in the art so as to be used to test more than four shift solenoid valves and more than four proportional solenoid valves.  
         [0045]     While the invention has been shown and described with respect to particular embodiments thereof, those embodiments are for the purpose of illustration rather than limitation, and other variations and modifications of the specific embodiments herein described will be apparent to those skilled in the art, all within the intended spirit and scope of the invention. Accordingly, the invention is not to be limited in scope and effect to the specific embodiments herein described, nor in any other way that is inconsistent with the extent to which the progress in the art has been advanced by the invention.