Air compressor for vehicle

Abstract

An air compressor (10) for a vehicle comprises at least one cooling duct (30) arranged to convey air from outside the compressor (10), alongside a sealable chamber (28) containing an electric motor (22), alongside a cylinder (12), and through a cylinder head (18) for discharge from at least one exhaust portion (32) spaced from an air inlet (20), and a fan (34) arranged to discharge air from the air inlet (20). The fan (34) is operable to push air through the or each cooling duct (30). Alternatively or additionally, the compressor (10) includes a sensor (56) arranged to sense a critical parameter of the compressor (10) and a controller in communication with the motor (22) and the sensor (56), the controller configured to control operation of the motor (22) to adjust a rotational speed of the shaft (24) in response to receiving a sensed value from the sensor (56).

Description

[0001] This application is a divisional application of the application with the application number: 202011516347.3, the application date: December 21, 2020, and the invention title: Air Compressor for Vehicles. Technical Field

[0002] The present invention generally relates to an air compressor for a vehicle, and more particularly to an air compressor that is sealed to prevent moisture and dust from entering. Background Art

[0003] Air compressors are used to pressurize air in a range of applications, such as operating pneumatic tools.

[0004] Some air compressors are used in vehicles, including manual portable compressors and in-vehicle compressors. Such compressors are configured to be powered by the vehicle's battery. Compressed air is typically used for tire inflation, powering a pneumatic locking differential, and / or powering pneumatic tools. Such compressors are commonly used in off-road vehicles (commonly referred to as "4x4" or "4WD").

[0005] Some vehicle air compressors are sealed to prevent moisture and dust from entering, thereby improving reliability under adverse environmental conditions. Such compressors house an electric motor in a sealed chamber to prevent moisture and dust from entering the motor. However, operating the electric motor within a sealed chamber generates heat, which can damage the motor. This problem is typically solved by controlling the motor temperature by limiting the motor operating time. For example, this typically involves using a thermal cut-off switch that prevents power from being supplied to the motor when the motor temperature exceeds a specified critical threshold. The switch resumes supplying power to the motor when the motor temperature is significantly below the threshold.

[0006] Limiting the operation of the motor in this way means that such air compressors are designated as having a repeatable "duty cycle", i.e., a repeatable operating cycle without generating harmful residual heat. The duty cycle is typically expressed as the percentage of an hour period that a compressor operating at a specific ambient temperature can run continuously without reaching a critical temperature threshold (referred to as the "run time"). For example, when a compressor runs for 30 minutes before it cannot run for 30 minutes (to allow sufficient cooling to prevent damage due to heating - referred to as the "off time"), this defines a 50% duty cycle.

[0007] A compressor with a duty cycle less than 100% means that, during use, the compressor will periodically not operate. This can be inconvenient for the user. For example, if only three of the four tires are inflated with air pressurized by the compressor before the compressor must stop operating, the user must wait until the compressor is operable again to complete the task. In extremely hot conditions, such as in the desert, the high ambient temperature reduces the air density, increases the temperature of the compressor, and decreases the cooling efficiency, thus affecting the duty cycle by reducing the operating time period and increasing the shutdown time period, and this problem becomes more serious. This typically greatly extends the duration of tasks, such as inflating tires, which may dangerously increase the user's exposure to extreme environmental conditions.

[0008] Any discussion of documents, acts, materials, devices, articles, etc. included in this specification should not be taken as an admission that any or all of these matters are common general knowledge in the field relevant to the present disclosure, as they existed prior to the priority date of each appended claim. Summary of the Invention

[0009] According to some disclosed embodiments, there is provided an air compressor for a vehicle, the air compressor comprising: a cylinder defining a bore; a piston slidably disposed within the bore; a cylinder head disposed across one end of the cylinder; an air inlet arranged to convey air from outside the air compressor into the cylinder; an electric motor having a motor shaft operably connected to the piston such that rotation of the motor shaft causes the piston to reciprocate to compress the air in the cylinder; a housing defining a sealable chamber in which the electric motor is sealably received; a first sensor arranged to sense a critical parameter of the air compressor; a controller in communication with the electric motor, the first sensor, and a memory configured to store a critical parameter threshold, the controller being configured to control the operation of the electric motor to adjust the rotational speed of the motor shaft. In response to the controller receiving a sensed value from the first sensor, the controller is configured to communicate with the memory to determine the difference between the sensed critical parameter and the associated critical parameter threshold. In response to the controller determining the difference, the controller is configured to determine an adjustment factor and cause the electric motor to adjust the rotational speed of the motor shaft by the adjustment factor.

[0010] The controller can be configured such that, in response to the controller determining that the sensed critical parameter is greater than the associated critical parameter threshold, the controller determines a negative adjustment factor and causes the electric motor to reduce the rotational speed of the motor shaft by the adjustment factor.

[0011] The controller can be configured such that, in response to the controller receiving a sensed value from a first sensor, the controller compares the sensed value with a historical sensed value stored in the memory to determine a rate of change, and is further configured such that determining the adjustment factor includes evaluating the rate of change.

[0012] The first sensor can be arranged to sense the current taken by the electric motor, and the air compressor can further include a second sensor arranged to sense the temperature of the air compressor, and wherein the controller communicates with the second sensor to receive the sensed temperature.

[0013] The second sensor can be arranged to sense the temperature of the cylinder head, and at least one of the memory and the controller is arranged on a printed circuit board (PCB), and the air compressor can further include a third sensor arranged to sense the temperature of the PCB, and wherein the controller communicates with the third sensor to receive the sensed temperature value. In such an embodiment, the PCB can be hermetically contained within a sealable chamber of the housing.

[0014] The controller can be configured to communicate with each sensor to evaluate the sensed values and determine a plurality of adjustment factors, each adjustment factor being associated with one of the sensed critical parameters.

[0015] The controller can be configured such that in response to the controller determining a plurality of adjustment factors, the controller causes the electric motor to adjust the rotational speed of the motor shaft in accordance with a maximum reduction factor.

[0016] The controller can be configured such that in response to the rotational speed of the motor shaft being adjusted, the controller repeats communication with each sensor to effect operations in a cyclic program.

[0017] The air compressor can further include at least one cooling duct arranged to convey air from outside the air compressor, alongside the electric motor and the cylinder, and through the cylinder head for discharge from at least one exhaust portion spaced from the air inlet.

[0018] According to other disclosed embodiments, there is provided an air compressor including: a cylinder defining a bore; a piston slidably disposed within the bore; an air inlet arranged to convey air from outside the air compressor into the cylinder; an electric motor having a motor shaft operably connected to the piston such that rotation of the motor shaft causes the piston to reciprocate to compress air within the cylinder; a housing defining a sealable chamber within which the electric motor is hermetically received; at least one cooling duct arranged to convey air from outside the air compressor, alongside the sealable chamber and alongside the cylinder, for discharge from at least one exhaust portion spaced from the air inlet; and a fan operable to urge air through the cooling duct or each cooling duct.

[0019] The air inlet may be arranged to receive air in a first direction, and the exhaust portion or each exhaust portion is arranged to discharge air in a second direction perpendicular to the first direction.

[0020] The exhaust portion or each exhaust portion is operably arranged above the air inlet.

[0021] The exhaust portion or each exhaust portion is operably arranged above the cylinder.

[0022] The housing may define at least one passage extending parallel to and spaced apart from the chamber to convey air along the chamber and through the housing.

[0023] The housing may define at least one conduit arranged to convey air from the at least one passage to the cylinder head at a right angle.

[0024] The housing may include a plurality of bodies, wherein a first body defines the sealable chamber and the at least one passage, and a second body defines the at least one conduit.

[0025] The air compressor may further include a cylinder head configured to receive and surround the cylinder, the cylinder head defining at least one cooling chamber extending parallel to the cylinder to convey air alongside the cylinder, wherein the at least one cooling chamber is arranged to convey air from the at least one conduit and through the cylinder head to the at least one exhaust portion.

[0026] The air compressor may further include: a sensor arranged to sense a critical parameter of the air compressor; a controller in communication with the motor, the first sensor, and a memory, the memory being configured to store a critical parameter threshold and being configured to control the operation of the motor to adjust the rotational speed of the motor shaft; and wherein, in response to the controller receiving a sensed value from the first sensor, the controller is configured to communicate with the memory to determine the difference between the sensed critical parameter and the associated critical parameter threshold, and in response to the controller determining the difference, the controller determines an adjustment factor and causes the motor to adjust the rotational speed of the motor shaft according to the adjustment factor.

[0027] According to a further disclosed embodiment, there is provided an air compressor assembly including a pair of air compressors and a cylinder head housing as described above, the shape of which is adapted to accommodate the cylinders of each compressor to connect the air compressors together.

[0028] Throughout the specification, the word "comprising" or variations such as "having" or "including" will be understood to imply the inclusion of the stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0029] It should be understood that the embodiments may include the steps, features and / or wholes disclosed herein or pointed out individually or jointly in the specification of this application, and any and all combinations of two or more of said steps or features. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0031] Figure 1 is a top perspective view of an air compressor;

[0032] Figure 2 is Figure 1 a cross-sectional side view of the compressor shown;

[0033] Figure 3 is an exploded top perspective view of the compressor shown in the previous figures, with some components of the compressor hidden;

[0034] Figure 4 and Figure 5 are respectively Figures 1 to 3 a top perspective view and an end view of the housing forming part of the compressor shown;

[0035] Figures 6 to 8 are respectively Figures 1 to 3 a top perspective view, a side view and a top view of another housing forming part of the compressor shown;

[0036] Figure 9 and 10 are respectively Figures 1 to 3 a bottom perspective view and a bottom view of the cylinder head forming part of the compressor shown;

[0037] Figure 11 is a perspective view of an alternative air compressor;

[0038] Figure 12 is a flow chart illustrating the operating phases of the disclosed compressor; and

[0039] Figure 13 is a graph of output flow rate (liters per minute) against time, showing the operation of the disclosed compressor and a prior art compressor. DETAILED DESCRIPTION

[0040] In the drawings, reference numeral 10 generally denotes an air compressor 10 for a vehicle (not shown). The air compressor 10 is configured as a portable compressor or an in-vehicle compressor. It should be understood that the air compressor 10 is not limited to use in vehicles, but can be used in other applications, such as driving pneumatic tools in construction or maintenance situations.

[0041] The air compressor 10 includes: a cylinder 12 that defines a bore 14; a piston 16 slidably disposed within the bore 14; a cylinder head 18 disposed across one end of the cylinder 12; an air inlet 20 arranged to convey air from outside the air compressor into the cylinder 12; an electric motor 22 having a motor shaft 24 operably connected to the piston 16 such that rotation of the motor shaft 24 causes the piston 16 to reciprocate to compress the air in the cylinder 12; a housing 26 that defines a sealable chamber 28 within which the electric motor 22 is sealably received; at least one cooling conduit 30 arranged to convey air from outside the air compressor 10, alongside the sealable chamber 28, alongside the cylinder 12, and through the cylinder head 18 for discharge from at least one exhaust portion 32 spaced from the air inlet 20; and a fan 34 operable to push air through the cooling conduit 30 or each cooling conduit 30.

[0042] Figures 1 to 3 An embodiment of the air compressor 10 is shown. The compressor 10 is configured to be powered by a DC power source, which is typically a battery greater than 40A, such as commonly found in a vehicle. The compressor 10 includes an electrical connector 40 for connection to a cable harness (not shown) that is connected to the battery.

[0043] The compressor 10 is designated as being small enough and lightweight enough to be manually carried by a user, such as in a case, or can be mounted to a vehicle, such as in an engine compartment or the bed of a multi-purpose vehicle. The compressor 10 can be mounted in a vertical direction (as Figure 1 shown) or in a horizontal direction via a mounting bracket (not shown), where the cylinder head 18 is rotated 90 degrees to be adjacent to the mounting bracket and / or the mounting surface. In some embodiments, the compressor 10 is mounted horizontally next to another identical compressor and operates in series to provide additional output.

[0044] The cylinder head 18 is connected to a manifold 35, which in turn is connected to a manifold cap 36. The cylinder head 18 includes an exhaust portion 38 arranged to convey compressed air from the cylinder 12 to the tube 35 and the cap 36. The cap 36 is configured to connect to a hose (not shown). The hose can be directly connected to an application component such as a tire to convey air to the application component, or can be connected to a storage tank (not shown) to convey air into the storage tank, which is subsequently supplied to the application component.

[0045] AsFigure 2 As shown, the electric motor 22 is disposed in a sealable chamber 28 defined by a housing 26. One end of the chamber 28 is sealed by a fan shroud 41 and the other end is sealed by a crankcase 42. A printed circuit board (PCB) 44 is disposed within the chamber 28 at one end of the electric motor 22. The motor shaft 24 extends from the other end of the electric motor 22 to engage the crankshaft 46. The piston 16 is connected to the crankshaft 46 by a piston rod 48. The piston 16 is sealed on the bore 14 by a peripheral seal 50. Rotation of the motor shaft 24 is caused by the electric motor 22, and rotation of the crankshaft 46 causes the piston 16 to reciprocate within the bore 14. The electric motor 22 is generally configured as a brushless motor to enhance control of the rotational speed of the shaft 24.

[0046] The PCB 44 includes a microprocessor 52 having a memory 54. The microprocessor 52 is configured to operate as a controller to control the operation of the electric motor 22, including regulating the rotational speed of the motor shaft 24. The memory 54 is configured to store threshold ranges related to critical parameters of the air compressor 10, as discussed in more detail below. In the illustrated embodiment, the microprocessor 52 having controller functionality and the memory 54 are integrated. In other embodiments (not shown), the microprocessor 52 may be separated from and communicatively connected to a controller module and a memory. For example, the memory may be remotely hosted and accessed via a wireless connection or the Internet.

[0047] In the illustrated embodiment, the PCB 44 carrying the microprocessor 52 is mounted within the sealable chamber 28 to be internally housed within the housing 26. In some embodiments (not shown), the PCB 44 is mounted external to the housing 26, such as fixed near the manifold 35. In other embodiments (not shown), the PCB 44 is mounted remote from the compressor 10, such as within a vehicle. In other embodiments (not shown), the controller is configured as an application executable by a computing device such as a smartphone, and the PCB 44 is configured to be replaced by a communication module communicative with the computing device to allow for remote hosting of the controller functionality.

[0048] The thresholds are defined based on measurable parameters related to the use of the compressor 10 that can cause damage to the compressor 10 or associated components. For example, in an embodiment configured to be powered by a 12V battery, the memory 54 stores a maximum current threshold corresponding to the 12V battery to limit the current that can be drawn by the electric motor 22, thereby avoiding damage to the electric motor 22. Similarly, the memory 54 stores a maximum electric motor 22 temperature threshold, which is defined as the maximum temperature at which the electric motor 22 can operate without being damaged.

[0049] The compressor 10 includes at least one sensor configured and arranged to sense at least one critical parameter of the compressor 10. In Figures 1 to 3In the illustrated embodiment, compressor 10 includes three sensors 56, 58, 60. The first sensor 56 is disposed on the PCB 44 to sense the current drawn by the electric motor 22, the second sensor 58 is disposed in the crankcase 42 to sense the temperature of the cylinder head 18, and the third sensor 60 is disposed on the PCB 44 to sense the temperature of the PCB 44.

[0050] Sensors 56, 58, 60 allow monitoring of power consumption to optimize the operation of the PCB 44 and monitoring of two critical temperatures, which if exceeded, will cause damage to components of the compressor 10, such as piston seal 50 or valves (not shown) associated with the exhaust section 32. It should be understood that in other embodiments, compressor 10 may include other sensors sensing other critical parameters, such as any of the following sensors: a torque sensor (not shown) sensing the torque applied by the electric motor shaft 24, other temperature sensors (not shown) sensing the temperature of the cylinder head 18 and / or other parts of the housing 26, and / or a tachometer (not shown) sensing the revolutions per minute of the crankshaft 46.

[0051] The microprocessor 52 is configured to communicate with each of the sensors 56, 58, 60 to receive sensed values and communicate with the memory 54 to access thresholds. The microprocessor 52 is operable to control the operation of the electric motor 22 to regulate the rotational speed of the electric motor shaft 24. The microprocessor 52 and sensors 56, 58, 60 operate together to define a closed-loop control system to regulate the operation of the compressor 10. This will be discussed in detail below.

[0052] In the illustrated embodiment, the electric motor 22 is a brushless electric motor 22. The microprocessor 52 regulates the speed of the electric motor shaft 24 by applying power to the electric motor 22 in variable pulses according to a pulse width (PWM) modulation waveform.

[0053] Figures 2 to 4 Figures 6 and 9 illustrate the fluid flow path defined by the cooling conduit 30. This extends through the housing 26, crankcase 42, and cylinder head 18 for discharge from the plurality of exhaust sections 32. Air indicated by the arrows is pushed by the fan 34 into the passage 64 defined by the housing 26, which passage 64 is parallel to and extends beside the sealable chamber 28, through the conduit 66 defined by the crankcase 42, bypasses the internal chamber housing the crankshaft 46 and the electric motor shaft 24, then passes through the cooling chamber 68 defined between the cylinder 12 and the cylinder head 18, and is discharged through the exhaust section 32, which in the illustrated embodiment is defined as the hole 70 in the top surface of the cylinder head 18. The air then flows around the periphery of the exhaust plate 71 ( Figure 1 ) for discharge from the compressor 10.

[0054] The exhaust portion 32 is arranged to discharge air from the cooling conduit 30 in a direction perpendicular to the direction of the air entering the air inlet 20. This is useful because it directs the hot air leaving the cooling conduit 32 away from the air inlet 20. As Figures 1 to 3 shown, this is enhanced by configuring the housing 26 such that the compressor 10 can be mounted or otherwise positioned on a vertically oriented surface. This advantageously operably arranges the exhaust portion 32 above the air inlet 20 to further enhance directing the hot air away from the air inlet 20. This improves the efficiency of the compressor 10 because it avoids or reduces the discharged hot air with reduced density entering the cylinder 12 and being compressed, which would reduce the load on the electric motor 22 and thus reduce the output. Similarly, the exhaust portion 32 is operably arranged above the cylinder 12 to optimize the cooling of the cylinder 12 by allowing air to pass through the conduit 30 along the length of the cylinder 12.

[0055] In the illustrated embodiment, the cooling conduit 30 is defined by the housings 26, 42, 18 of the compressor 10 to provide an internal conduit system. This is useful because this arrangement enhances the cooling of the housings 26, 42, 18 and the components contained therein by communicating air via the housings 26, 42, 18. It should be understood that in other embodiments (not shown), one or more external cooling conduits, such as those defined by externally mounted hoses, may be fixed to the housings 26, 42, 18 to cool the compressor 10.

[0056] As Figure 4 and Figure 5 shown, the housing 26 defines four channels 64 arranged around the sealable chamber 28 to extend through the housing 26. It should be understood that the number of channels 64 is merely illustrative, and in other embodiments, the housing 26 may define more or fewer channels 64.

[0057] Figures 6 to 8 Shown is that the crankcase 42 defines two conduits 66, each conduit 66 arranged to receive air from two of the channels 64 and deliver the air at a right angle to the cylinder head 18. Again, it should be understood that the number of conduits 66 is merely illustrative, and in other embodiments, the crankcase 42 may define more or fewer conduits 66.

[0058] In other embodiments (not shown), the housing 26 and the crankcase 42 may be integrally formed in a single body. It should be understood that in other embodiments, the housing 26 and the crankcase 42 may be configured as separate bodies, such as a pair of mirror-image bodies.

[0059] Figure 9 and 10The lower side of the cylinder head 18 is shown, showing the inner wall 72 which is arranged to partly surround the cylinder 12 to define a cooling chamber 68 between the outside of the cylinder 12 and the wall 72. As Figure 10 shown, a radial array of holes 70 extends through the top surface of the cylinder head 18 to discharge air from the cooling chamber 68. In some embodiments, each hole 70 is associated with a check valve to allow air to be discharged from the exhaust section and prevent fluid or dust from entering the hole 70.

[0060] It should be understood that in some embodiments, the compressor 10 does not include any cooling ducts 30. In such embodiments, the compressor 10 includes a microprocessor 52 and at least one sensor as described above and is operable to adjust the rotational speed of the motor shaft 24 to adjust the operation of the compressor 10, as described in more detail below.

[0061] It should also be understood that in some embodiments, the compressor 10 does not include any sensors 56, 58, 60 or PCB 44. In such embodiments, as described above, the compressor 10 only operates the fan 34 to drive air through at least one cooling duct 30 to adjust the temperature and operation of the compressor 10.

[0062] Figure 11 A replacement air compressor 120 embodiment is shown, which is an assembly including a pair of compressors 10 (as described above and Figures 1 - 3 shown), arranged in a mirror image direction relative to each other and connected by a common cylinder head housing 122. The cylinder head housing 122 replaces the cylinder head 18 of each compressor 10. The housing 122 is configured to receive the cylinders 12 of each compressor 10 and cooperate with the crankcase. The compressor 120 also includes a common large-capacity manifold 124 and a manifold cap 126, which replace the manifolds 35 and manifold caps 36 of each compressor 10. The inside of the cylinder head housing 122 is shaped to convey the air compressed by each compressor 10 to the manifold 104, which in turn conveys the compressed air to the manifold cap 128. The manifold cap 126 includes an air outlet (not visible) which is configured to connect to a hose (not shown) to allow the use of compressed air.

[0063] The cylinder head housing 122 defines a plurality of exhaust slots 128 and is shaped inside to direct the air received from the ducts 66 extending through each crankcase 42 to discharge from at least some of the slots 128 and away from the compressor 120. In the illustrated embodiment, the cylinder head housing 122 is configured to discharge air through two slots 128 provided closest to the intake end of the compressor 120, as Figure 11 indicated by the arrows. It should be understood that in other embodiments, the housing 122 may be configured to discharge air from alternative slots 128 or all of the slots 128.

[0064] Figure 12 Shows the operation of each stage of compressor 10 according to a closed-loop control system defined by a microprocessor 52 (including a memory 54) and sensors 56, 58, 60.

[0065] The compressor 10 is activated ("started") by using a switch or other user interface (such as a touch screen of the control system) typically installed on the dashboard at 80 by user operation and powered from a DC power source (such as a vehicle battery). This causes the microprocessor 52 to set the pulse width modulation (PMW) of the electric motor 22 to an initial value of 100% at 82, causing the electric motor 22 to rotate the motor shaft 24 at maximum rotational speed.

[0066] The microprocessor 52 communicates with the first sensor 56 at 84 to measure the current (A) taken by the electric motor 22, and communicates with the memory 54 at 86 to identify the relevant threshold (A MAX ), and determines the difference between A and A MAX

[0067] If A is greater than A MAX , at 88, the microprocessor 52 calculates a negative regulation factor, which is a variable factor based on the difference between A and A MAX , and determines a reduced PMW (PMW 1 ) based on the calculated regulation factor. This includes reducing the PWM by the reduction amount defined by the regulation factor 0 . When the compressor is initially running, PWM 0 = 100%, and PWM 1 is equal to 100% minus the reduction amount. In each subsequent operating cycle, PWM 1 is equal to the PWM 0 previously calculated by the microprocessor 52 (discussed further below) minus the reduction amount.

[0068] In the case where A is less than A MAX , at 90, the microprocessor 52 calculates a positive regulation factor and determines an increased PWM value (PWM 1 ) based on the calculated regulation factor. This includes increasing the PWM by the increment amount defined by the regulation factor 0 . When the compressor is initially running up to PWM 0 = 100%, PWM 1 remains at a value of 100%. In each subsequent operating cycle, PWM 1 is equal to the PWM 0 previously calculated by the microprocessor 52 plus the increment amount.

[0069] ​The initial stage of evaluating the current obtained from the electric motor is configured to be executed quickly to rapidly identify relevant dangerous situations, such as the electric motor 22 stopping and obtaining a very high current. This will cause PWM = 0% to be applied to the electric motor 22 to prevent damage.

[0070] At 92, the microprocessor 52 compares the time value with the defined temperature sampling interval (time period) stored in the memory 54. Initially, the time value is measured starting from "start". Subsequently, as described below, the time value is measured starting from resetting the clock at 102. If the time value is less than the interval period, the microprocessor 52 bypasses the temperature evaluation stage 94 - 102 and continues with the PWM 0 calculation at 104, and then writes it to the electric motor 22 at 106 to regulate the speed of the electric motor shaft 24.

[0071] The time sampling interval is defined as an instance for limiting temperature measurement and PMW value calculation to limit the calculation and energy. This time interval is defined as approximately 5 - 10 seconds because the temperature of the compressor 10 components does not change significantly within this time period.

[0072] When the time is greater than the sampling interval period, at 94, the microprocessor 52 communicates with the third sensor 60 to measure the temperature (T PCB ) of the PCB 44.

[0073] At 96, the microprocessor 52 calculates the adjustment factor (F 1 ), which is a variable function based on the difference between T PCB and the maximum temperature threshold (T PCB MAX ) stored in the memory 54 and the rate of change of T PCB relative to T PCB MAX . The rate of change of T PCB is determined by comparing the sensed T PCB value with the historical sensed T PCB values stored in the memory 54. The microprocessor 52 then calculates another PWM value (PWM 0 ) by applying the adjustment factor F1 to the PWM 2 .

[0074] Then, at 98, the microprocessor 52 communicates with the second sensor 58 to measure the temperature (T HD ) of the PCB 44.

[0075] At 100, the microprocessor 52 calculates the adjustment factor (F 2 ), which is based on T HD and T stored in the memory 52HD MAX the difference between and relative to T HD MAX of T HD a variable function of the rate of change. T HD The rate of change is determined by comparing the sensed T HD with the previously received T HD value stored in the memory 54. The microprocessor 52 then calculates another PWM value (PWM 2 by applying an adjustment factor F 0 to PWM 3 ).

[0076] At 102, the microprocessor 52 resets the clock used for temperature sampling interval calculation at 92.

[0077] At 104, the microprocessor 52 calculates the final PWM value (PWM 1 by comparing three previously calculated PWM values (PWM 2 , PWM 3 , PWM 0 ) and selecting the lowest PWM value. Since each PWM value is calculated by evaluating critical parameter values, selecting the lowest value ensures that the operation of the compressor 10 at the selected PWM can keep all monitored critical parameters below the defined safety thresholds.

[0078] At 106, the microprocessor 52 writes the selected value PWM 0 to the motor 22 to adjust the rotational speed of the motor shaft 24. It should be understood that when each of PWM 1 , PWM 2 , PWM 3 is greater than the previously written PWM 0 , this causes an increase in the rotational speed of the shaft 24. Conversely, when any of PWM 1 , PWM 2 , PWM 3 is less than the previously written PWM 0 , this causes a decrease in the rotational speed of the shaft 24.

[0079] The process is then repeated by returning to step 84 to measure the current A. The loop execution from steps 84 to 106 allows the operation of the motor 22 to be continuously adjusted by adjusting the rotational speed of the motor shaft 24 as fast as possible while avoiding damage to any components of the compressor 10.

[0080] As described above, the configuration of the microprocessor 52 and PWM 0The calculation is advantageous because it ensures that the electric motor 22 operates at a maximum safe speed, which is calculated in response to evaluating the sensed and acquired current, the temperature of the PCB 44, and the temperature of the cylinder head 18 relative to defined thresholds. It should be understood that evaluating these three critical parameters is merely illustrative, and in other embodiments, the microprocessor 52 may be configured to evaluate more or fewer critical parameters to determine the PWM 0 .

[0081] Figure 13 shows a prior art compressor and Figures 1 to 3 a graph showing the use of the compressor 10 shown. Air flow (liters per minute) and compressor temperature (°C) are defined along the y-axis, and time (minutes) is defined along the x-axis. The dashed line 110 shows the critical temperature limit, such as the critical temperature of the electric motor 22.

[0082] The first curve 112 shows the operation of a prior art compressor that has a 50% duty cycle and has a 30-minute operating time period followed by a 30-minute off time period to allow cooling. This defines a cycle of operating at 75 liters per minute and a cycle of operating at 0 liters per minute, forming a square-edge waveform.

[0083] The second curve 114 shows the temperature of the compressor during use, where starting from the ambient temperature, the temperature gradually increases until it reaches the critical temperature at which the thermal switch operates to deactivate the compressor, thereby allowing the temperature to drop to a defined low threshold at which the switch is re-powered.

[0084] The third curve 116 shows the operation of the compressor 10 with a 100% duty cycle. Due to the continuous monitoring of the critical parameters by the microprocessor 52 and the resulting incremental adjustment of the PWM and the speed of the electric motor shaft 24, this defines an initial cycle of operating at 150 liters per minute that gradually decreases to a substantially steady state of approximately 50 liters per minute. A comparison of the area below the third curve 116 with the area below the first curve 112 shows that the compressor 10 produces a greater net flow rate within a defined time period than the prior art compressor does within the same time period. Thus, this optimizes the output, for example, allowing the compressor 10 to fill a tank with compressed air faster than a prior art compressor.

[0085] The fourth curve 118 shows the temperature of the compressor 10 during use, where starting from the ambient temperature, the temperature gradually increases until it almost reaches the critical temperature at which, as described above, the temperature is kept constant by gradually adjusting the PWM and the speed of the electric motor shaft 24. This advantageously prevents damage to the compressor 10 due to overheating when operating the electric motor 22 to optimize the flow rate.

[0086] The compressor 10 is configured to operate at a 100% duty cycle while optimizing the output. This is achieved by the microprocessor 52 continuously monitoring critical operating parameters (such as amperage and critical temperature) and dynamically adjusting the speed of the electric motor 22 responsively such that the electric motor 22 can operate sustainably at or near the critical threshold without damaging the compressor 10. This advantageously improves the flow rate, the durability of the compressor 10, and / or the user experience. Additionally, this allows the operation of the compressor 10 to vary according to local environmental conditions, such as ambient temperature and pressure

[0087] Those skilled in the art will appreciate that various changes and / or modifications can be made to the above-described embodiments without departing from the broad general scope of the disclosure. Accordingly, the embodiments are to be considered in all respects as illustrative and not restrictive.

Claims

1. An air compressor for a vehicle, the air compressor comprising: a cylinder defining a bore; a piston slidably disposed within the bore; an air inlet arranged to convey air from a first location, which is external to the air compressor, into the cylinder; an electric motor having a motor shaft operatively connected to the piston such that rotation of the motor shaft causes the piston to reciprocate to compress air within the cylinder; a printed circuit board (PCB) carrying a microprocessor configured to control the operation of the electric motor; a housing defining a sealable chamber within which the electric motor and the printed circuit board (PCB) are sealably received and thus internally housed within the housing, and the PCB is disposed at a first end of the chamber, and the housing defines at least one passage extending parallel to and spaced from the chamber to convey air along the chamber and through the housing; at least one cooling duct arranged to convey air from a second location, which is external to the air compressor and adjacent to the first end of the chamber and spaced from the first location, along the sealable chamber beside and along the cylinder through the at least one passage to discharge from at least one exhaust portion spaced from the air inlet; and a fan operable to push air through the cooling duct or each cooling duct, the fan being disposed adjacent to the first end of the chamber.

2. The air compressor according to claim 1, wherein, the air inlet is arranged to receive air in a first direction, and the exhaust portion or each exhaust portion is arranged to discharge air in a second direction transverse to the first direction.

3. The air compressor according to claim 1, wherein, the exhaust portion or each exhaust portion is operatively arranged above the air inlet.

4. The air compressor according to claim 3, wherein, the exhaust portion or each exhaust portion is operatively arranged above the cylinder.

5. The air compressor according to claim 1, wherein, the housing defines at least one duct arranged to convey air from the at least one passage to the cylinder at a right angle.

6. The air compressor according to claim 5, wherein the housing comprises a plurality of bodies, wherein a first body defines the sealable chamber and the at least one passage, and a second body defines the at least one duct.

7. The air compressor according to claim 5, comprising a cylinder head configured to receive and surround the cylinder, the cylinder head defining at least one cooling chamber extending parallel to the cylinder to convey air beside the cylinder, wherein the at least one cooling chamber is arranged to convey air from the at least one duct and through the cylinder head to the at least one exhaust portion.

8. The air compressor according to claim 1, further comprising: a sensor arranged to sense critical parameters of the air compressor; a controller in communication with the electric motor, the first sensor and a memory configured to store critical parameter thresholds and configured to control the operation of the electric motor to adjust the rotational speed of the motor shaft; and Wherein, in response to the controller receiving a sensed value from the first sensor, the controller is configured to communicate with the memory to determine the difference between the sensed critical parameter and the associated critical parameter threshold, and in response to the controller determining the difference, the controller determines an adjustment factor and causes the motor to adjust the rotational speed of the motor shaft according to the adjustment factor.

9. An air compressor assembly, comprising: a pair of air compressors according to claim 1; and a cylinder head housing shaped to receive the cylinders of each compressor to couple the air compressors together.

10. The air compressor according to claim 9, wherein, the cylinder head housing defines each exhaust portion.

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