Patent Application
20080110337
The present invention relates to desiccant cartridges. It finds particular application in conjunction with identifying when the desiccant within the cartridge is contaminated to a point where the cartridge including the desiccant should be replaced and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other applications.
Air dryers are used in compressed air braking systems of, for example, heavy vehicles, to filter water and contaminants out of the compressed air. One way that dryer and cleaner compressed air contributes to improved performance of the braking system is by reducing failure of valves in colder weather as a result of icing.
One type of air dryer uses a desiccant material contained in a cartridge to filter the water and contaminants from the compressed air. The desiccant has a finite life. More specifically, over time, the desiccant becomes sufficiently contaminated and the performance degrades to a point that the cartridge must be replaced.
The present invention provides a new and improved apparatus and method for determining when the desiccant cartridge must be replaced.
In one aspect of the present invention, it is contemplated to determine a saturation level of moisture and/or other contaminants in a desiccant material by determining an electrical parameter across the desiccant material.
In one embodiment, an air dryer includes a housing, a desiccant in the housing, and an electrical contact in the desiccant. A level of at least one of moisture and other contaminants is determined as a function of an electrical parameter between two electrical contacts of dissimilar materials that electrically contact the desiccant.
In another embodiment, an air dryer includes a housing, a desiccant in the housing, and an optical sensor receiving reflected light from the desiccant. A level of at least one of moisture and other contaminants is determined as a function of an amount of the reflected light received by the optical sensor from the desiccant.
In the accompanying drawings which are incorporated in and constitute a part of the specification, embodiments of the invention are illustrated, which, together with a general description of the invention given above, and the detailed description given below, serve to exemplify the embodiments of this invention.
With reference to
The cartridge 20 encloses a desiccant material 24. During a charging cycle of the dryer 10, the compressed air enters the dryer 10 through the supply port 14. The compressed air is then communicated into the interior volume 22 of the housing 12 by first entering the desiccant cartridge 20. While in the cartridge 20, the compressed air passes through the desiccant material 24 as shown by the arrows. The air is cleaned and dried as it passes through the desiccant material 24. For example, moisture and/or other contaminants (e.g., oil) are trapped in the desiccant cartridge 20 by the desiccant material 24. The air is then communicated from the desiccant cartridge 20 into a purge volume 26 in the housing 12 via a check valve 30 and an orifice 32. The cleaned and dried air passes through the purge volume 26 and then exits the housing 12 and the dryer 10 via a check valve 34 and the delivery port 16. Over time, as more compressed air is cleaned and dried by the desiccant material 24, the desiccant material 24 in the desiccant cartridge 20 becomes contaminated with oil and, therefore, must be replaced.
A first electrical component 36 (e.g., an electrical contact) is in the desiccant material 24. The electrical contact 36 is electrically connected to a threshold measuring device such as a meter 40, which measures an electrical parameter of the contact 36. In one embodiment, the meter 40 is a comparator. Alternatively, the meter 40 represents an analog input to an ECU 62 that responds to the analog input.
In one embodiment, the electrical contact 36 includes an anode. It is to be understood that the anode 36 is in the desiccant material 24. A second electrical component 42 (e.g., a cathode) also electrically contacts the desiccant material 24. In one embodiment, the anode 36 and the cathode 42 are dissimilar materials (e.g., metals).
When dissimilar metals are immersed in an electrolyte, a voltage potential is self generated between the two materials. The magnitude of the electric potential is proportional to the electronegativity difference of the two materials.
Materials of particular usefulness to the automotive industry include:
Magnesium is particularly advantageous for use with other metals because it generates a larger and more easily detected electrical potential. The theoretical voltage between a magnesium anode and a carbon cathode is 2.55−1.31=1.24 Volts. However, even the voltage between magnesium and zinc is 1.65−1.31=0.34 Volts is of useful magnitude for detecting desiccant wetness. Furthermore, magnesium acts as a sacrificial anode and protects metals with greater electronegativity from corrosion by the same mechanism that zinc protects galvanized iron. A battery effect will only work if there is a conductive electrolyte between an anode and a cathode. The desiccant material 24, when wet, serves as an electrolyte. Therefore, a battery effect is present (and electricity is generated) only if the desiccant material 24 is not dry.
The desiccant material 24 becomes wet as the moisture and/or other contaminants are removed from the compressed air. Furthermore, the wetness of the desiccant material 24 is proportional to a level of the moisture and/or other contaminants trapped in the desiccant material 24.
The material of the air dryer 10 housing 12 is non-conductive (e.g., non-conduction painted steel). The desiccant cartridge 20 includes a base portion 44 (e.g., a zinc coated steel plate or a crushed aluminum oil separator), which acts as the cathode 42. The base portion 44 is not in electrical contact with a wall 50 of the desiccant cartridge 20. Therefore, in one embodiment in which the anode 36 is a magnesium button fastened to an upper plastic perforated plate 52 in the cartridge 20, a battery effect is created between the magnesium anode 36 and the cathode 42. The meter 40 is electrically connected to the anode 36 and the cathode 42 for measuring an electrical parameter between the anode 36 and the cathode 42. In one embodiment, the electrical parameter is a voltage differential between the anode 36 and the cathode 42. Furthermore, the voltage differential between the anode 36 and the cathode 42 changes as a function of the level of moisture and/or other contaminants in the desiccant material 24. For example, the voltage differential between the anode 36 and the cathode 42 increases as the level of moisture and/or other contaminants in the desiccant material 24 increases.
A wire 54 (electrical conductor) is electrically and removably connected between the meter 40 and the anode 36. The wire 54 exits the housing 12 of the air dryer 10 via a fitting 56. Another wire 60 (electrical conductor) is electrically and removably connected between the cathode 42 and the meter 40. In this configuration, the meter 40 is electrically connected to both the cathode 42 and the anode 36. The meter 40 detects the voltage differential between the cathode 42 and the anode 36.
In one embodiment, the meter 40 electrically communicates with the electronic control module 62 (ECU). The ECU 62 monitors the electrical parameter (e.g., the voltage differential between the anode 36 and the cathode 42). The ECU 62 also communicates a signal indicating the level of moisture and other contaminants in the desiccant material 24 over a communication line 64 (e.g., a J1939 communication line on a heavy vehicle). In order to indicate a level of saturation of the desiccant material 24, a dash light 66 illuminates once the amount of the moisture and/or other contaminants exceeds a predetermined level. It is also contemplated that the ECU 62 communicates raw data of the meter readings to a memory device 68 so that historical data of the level of moisture and other contaminants in the desiccant material 24 is available to be analyzed.
Once it is determined that the level of moisture and other contaminants in the desiccant material 24 is above a predetermined level, the anode 36 and the cathode 42 are electrically disconnected from the wires 54, 60. Then, the desiccant cartridge 20 is removed from the housing 12 and replaced with a new cartridge including desiccant that is less saturated. The new desiccant cartridge is then electrically connected to the anode 36 and the cathode 42 via the wires 54, 60.
With reference to
In one embodiment, the first optical sensor 110 includes a light source 120 (e.g., a light emitting diode (LED)) and a light detector 122 (e.g., a photodiode or photocell) electrically connected by a connector 117. It is contemplated that the light source 120 is a colored (e.g., red) LED. However, other embodiments including light sources of any other color are also contemplated. An optional window 115 provides an external view of the LED 120 (e.g., to confirm the LED is functioning). The light source 120 directs light onto the desiccant 114 and the detector 122 receives the light from the source 120 that is reflected by the desiccant 114. The amount of light reflected by the desiccant 114 is indicative of the contamination of the desiccant 114. For example, as the desiccant 114 becomes more contaminated, less of the light from the source 120 is reflected to the detector 122. The detector 122 changes an electrical parameter such as voltage as a function of the reflected light received from the desiccant 114. In addition to, or instead of, monitoring voltage, other parameters that may be monitored include current, inductance, capacitance, conductance, or digital signals. For example, the optical sensor 110 acts as a light-to-voltage sensor that produces a relatively higher voltage when the desiccant 114 is not contaminated and relatively lower voltage when the desiccant 114 is contaminated. An electrical connector 124 on the cartridge 116 provides a pin 126 for supplying power for illuminating the light source 120, a pin 128 electrically connected to ground, and a pin 130 electrically connected to the detector 122. The pin 130 transmits the voltage output by the detector 122 to an electrical measuring device (not shown) (e.g., a meter). A pin 132 is electrically connected to a detector 134 of the second optical sensor 112.
In another embodiment, it is contemplated that the first optical sensor 110 is an integrated circuit chip (e.g., the TAOS chip TRS1722).
Although two optical sensors 110, 112 are illustrated in the desiccant material 114, it is to be understood that any number of optical sensors (e.g., one (1) optical sensor or more than two (2) optical sensors) are contemplated.
While the present invention has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant's general inventive concept.
