The present invention, in general, relates to manual control system for HVAC of a vehicle and, more particularly, to improved manual control for HVAC system of a vehicle having a variable thermistor.
BACKGROUND OF THE INVENTION
[002] Background description includes information that may be useful in understanding the present invention.
[003] Heating, ventilation, and air conditioning (HVAC) is a technology of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a sub-discipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, refrigeration and heat transfer.
[004] In existing arts, two technologies are available for controlling automobile HVAC system. First, in automobiles without cabin heater, AC compressor is manually switched on/off using AC switch (700) (as shown in figure 1-b) and once AC compressor is on, a variable thermistor is used to control the amount of cooling by switching the compressor on/off automatically (via a compressor clutch which is electric). A knob provided for controlling cooling process, rotates from maximum cooling to ambient air temperature. The thermistor is provided inside an evaporator connected to a compressor. However, mechanism to vary the resistance of the thermistor is provided in the knob. Generally, at maximum cooling, cut off temperature of the compressor is fixed to 2.0°C at the variable thermistor, so as to avoid icing at the evaporator.
[005] As the knob is manually rotated, resistance of the variable thermistor changes, that changes the cut off temperature of the compressor. When the

resistance of the variable thermistor increases by rotating the knob, cut off temperature of the compressor increases, thereby air at higher temperature is supplied inside the vehicle cabin. However, as there is no heater, in such cases air cannot be heated, and maximum temperature of the air supplied inside the vehicle cabin cannot be more than ambient air temperature. Therefore, such system is not applicable where air needs to be heated.
[006] In such arts, as shown in figure-l(a), cabin air (at ambient temperature) enters in the direction of arrow-1 (1) from outside and reaches into the evaporator chamber (2) where functioning of compressor on/off according to input received from knob, cools the air up to required temperature. Cooled air at required temperature is supplied to the vehicle cabin, in the direction as shown by arrow-2 (3).
[007] Figure-lb illustrates a knob (100) for manual control in such arts. The arrow arc (4) in figure-lb represents manner in which the knob (100) is rotated manually to vary resistance of the variable thermistor from a minimum to a maximum and correspondingly a coolest air to a hottest (ambient temperature) air is supplied to the vehicle cabin. When knob is rotated, the temperature at which compressor is switched off, keeps on increasing. For example, at maximum cool condition compressor will switch off at 2.0°C. As knob is rotated, the temperature keeps on increasing
(i.e., 5°C, 7°C 25°C and so on). So AC compressor is switched off earlier
and the cooled air supplied to cabin is controlled. However, such arts suffer from a drawback that only cooling is available. No provision for heating is available in such existing technology.
[008] Second, in automobiles with heater option, again AC compressor is manually switched on/off using AC switch (700) (as shown in figure 2-b) and once AC compressor is on, the AC runs at maximum cooling (up to

evaporator freezing) and then cold air coming out from evaporator is heated back again to provide comfortable cabin temperature. Such existing systems have a fixed thermistor at evaporator and the cut off temperature of the compressor is kept fixed, in general arts, is generally kept fixed at 2.0°C so as to prevent evaporator from freezing
[009] The knob can be rotated from maximum cooling (2.0 °C generally) to maximum heating. When the knob is rotated to increase the temperature of the air, a hot air damper of heater is opened, based on knob movement or position, which heats a portion of cold air from the evaporator. The cold air coming directly from the evaporator is mixed with the hot air from heater to form mixed air with desired temperature. The mixed air is then supplied to vehicle cabin.
[0010] In such arts, as shown in figure-2(a), cabin air or outside air enters in the direction of arrow-1 (1) and reaches the evaporator (201) where functioning of compressor on/off cools the air up to cut off temperature (i.e., maximum cool condition). Further, the air at maximum cool condition exiting from the evaporator (201), bifurcates in two compartments, a first compartment (206) and a second compartment (202), separated via a hot air damper (207).
[0011] The hot air damper (207) opens, closes or remains at an intermediate position between the first compartment (206) and the second compartment (202). Based on an input of desired temperature of cabin air required (which is provided by a user via rotating a knob (200) [shown by arrow-7 (7) in figure-2b]), amount of opening of the hot air damper (207) is controlled.
[0012] Amount of opening of the hot air damper (207) determines what proportion of air at maximum cool condition goes for a heating process.

Arrow-3 (3) indicates direction of the air at maximum cool condition flowing through the first compartment (206). Arrow-4 (4) indicates direction of the air at maximum cool condition flowing through the second compartment (202).
[0013] The air from the second compartment (202) enters into a heater (203). The heater (203) provides output of heated air at higher temperature in a heater chamber (204). Arrow-5 indicates direction of flow of heated air from the heater chamber (204). Further, air from heater chamber (204) mixes with air from the first compartment (206) (which is at maximum cool condition), in a passage (205) to produce air at desired temperature, which is supplied to the vehicle cabin. Air at desired temperature is supplied to the vehicle cabin, in the direction as shown by arrow-6 (6).
[0014] Figure-2b illustrates a knob (200) for manual control in such arts. The arrow arc (7) in figure-2b represents manner in which the knob (200) is rotated manually to vary amount of opening of the hot air damper (207). The opening of the hot air damper (207) is increased to achieve cabin air at higher temperature.
[0015] Thus, irrespective of required air temperature inside cabin, the air from evaporator is cooled to its maximum and then heated through heater and mixed to get air with desired temperature inside vehicle cabin. Therefore, this technology requires high energy consumption/ wastage in the process, as energy is used first to cool the air and then again to reheat the air to achieve air with required temperature.
[0016] Thus, there exists need of an improved technology for manual control of automobile HVAC to curb the energy wastage in the process while providing cabin air with required temperature.

OBJECTIVES OF THE INVENTION
[0017] It is therefore the object of the invention to overcome the aforementioned and other drawbacks existing in prior systems.
[0018] Another object of the present invention is to provide a technology for improved manual control for automobile HVAC to overcome the problem of the prior art.
[0019] Another object of the present invention is to provide technology for manual control of automobile HVAC that facilitates efficient utilization of energy in the HVAC process of a vehicle in between the maximum cooling and the maximum heating requirement.
[0020] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description.
SUMMARY OF THE INVENTION
[0021] To attain the above objects, the present invention provides a manual control system for HVAC of a vehicle. The manual control system for HVAC of a vehicle comprises a temperature knob to select a required temperature of air inside a vehicle cabin and AC switch to manually switch on/off the AC compressor. The temperature knob is rotated to select the required temperature from a range of temperature divided in a cooling zone and a heating zone.
[0022] A thermistor is connected with the temperature knob. The thermistor is designed such that it acts as a variable thermistor in cooling zone whereas it acts as a fixed thermistor in heating zone. Resistance of the variable thermistor is set by rotating the temperature knob. Air at an ambient temperature or cabin temperature enters into an evaporator. AC

compressor (not shown in figs) is switched on to reduce temperature of the air till cut off temperature of the compressor. The cut-off temperature is based on resistance of the variable thermistor set by rotating the temperature knob. The compressor is switched off at the cut-off temperature.
[0023] During heating, air from the evaporator enters into a first compartment. A second compartment is connected to a heater. A hot air damper is provided to separate the first compartment and the second compartment. The hot air damper is moved to create and to vary an opening between the first compartment and the second compartment. The portion of air entering into the second compartment from the first compartment gets heated inside the heater. Air heated inside the heater mixes with air from the first compartment in a passage to produce air with the required temperature to supply inside the vehicle cabin.
[0024] If the required cabin air temperature is selected from the cooling zone, the compressor cut off temperature is set by rotating the knob and the hot air damper remains closed ensuring that the opening between the first compartment and the second compartment remains closed and there is no hot air mixing to the air from the evaporator. In an embodiment, the hot air damper remains closed in the cooling zone of the temperature knob.
[0025] If the required cabin air temperature is selected from the heating zone, the compressor cut off temperature is set at a fixed value (2°C for example). In the heating zone, the compressor is on however can be switched off manually by user and the hot air damper varies the opening between the first compartment and the second compartment based on the knob position in heating zone.

[0026] The opening between the first compartment and the second compartment is varied by the hot air damper based on the required temperature selected by rotating the temperature knob.
[0027] The manual control system for HVAC of a vehicle comprises a spur gear to control movement the hot air damper and to vary an opening between the first compartment and the second compartment. The spur gear comprises a plurality of gear tooth on a part of circumference of the spur gear.
[0028] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.
[0029] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
[0030] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by the following detailed description.
[0031] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWING
[0032] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated

by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:
[0033] Figure la and lb altogether illustrate a technique of manual control for automobile HVAC of a vehicle having a variable thermistor and no heater, according to an embodiment of the existing art.
[0034] Figure 2a and 2b altogether illustrate a technique of manual control for FTVAC of a vehicle having a fixed thermistor and a heater, according to an embodiment of the existing art.
[0035] Figure 3 illustrates a temperature knob for manual control of FTVAC of a vehicle, according to an embodiment of the present invention.
[0036] Figures 4a and 4b illustrate a manual control system for FTVAC of a vehicle having a variable thermistor and a heater, according to an embodiment of the present invention.
[0037] Figures 5a to 5d illustrate a manual control system for FTVAC comprising a spur gear with teeth on a part of its circumference and having an integrated mechanism with the temperature knob to control movement of a hot air damper, according to an embodiment of the present invention.
[0038] Figure 6 illustrate a method for manual control of FTVAC of the vehicle.
[0039] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and

methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION OF THE INVENTION
[0040] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alterative falling within the scope of the disclosure.
[0041] As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.
[0042] The terms "comprises", "comprising", or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusion, such that a device, system, assembly that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to the system, or assembly, or device. In other words, one or more elements in a system or device proceeded by "comprises... a" does not, without more constraints, preclude the existence of other elements or additional elements in the system, apparatus or device.
[0043] Hereinafter a manual control for HVAC system of a vehicle having variable thermistor, will be explained in detail.

[0044] Referring to figure 3, which illustrates a temperature knob (300) and an AC switch (700) for manual control of HVAC of a vehicle, to select a required temperature of air inside a vehicle cabin from a range of temperature divided in a cooling zone (300a) and a heating zone (300b), according to an embodiment of the present invention.
[0045] The temperature knob (300) is provided on dashboard of a vehicle to manually select required temperature of air inside a vehicle cabin. A calibration of a range of temperature divided in a cooling zone (300a) and a heating zone (300b) is provided on the dashboard. The calibration of a range of temperature is such that temperature increases in clockwise direction. Indicator (la) indicated a lowest temperature and indicator (2a) indicates a highest temperature in the cooling zone (300a). In an example the lowest temperature in the cooling zone is not less than 2°C. The highest temperature in the cooling zone (300a) is equal to temperature of ambient air entering from outside. In the heating zone (300b) temperature calibrated, i.e., indicator (3b) to indicator (4b) are above the ambient temperature of air. Temperature in heating zone (300b) increases by rotating the temperature knob (300) in clockwise direction, i.e., from indicator (3b) to indicator (4b).
[0046] The user manually switches on/off the AC switch (700) and selects the required temperature from the range of temperature by rotating the temperature knob (300). Further, a variable thermistor [not shown in the figure] is connected in the temperature knob (300). During cooling zone, resistance of the variable thermistor varies based on the required temperature selected on the temperature knob (300). Based on the resistance of the variable thermistor, the cut off temperature of a compressor connected to an evaporator [provided in figure-4a and 4b] varies. The hot air damper (407) of the heater (403) [provided in figure-4a] remains closed in the cooling zone.

[0047] In an example, when the required temperature selected remains in the cooling zone (300a), the cut off temperature of a compressor connected to the evaporator (401) is according to the required temperature. For example, it can vary from a minimum equal of 2.0°C to a maximum equal of 30°C. When the required temperature selected remains in the heating zone (300b), the cut off temperature of a compressor connected to the evaporator is kept at a fixed value, i.e., for example 2°C.
[0048] Referring to figures 4a and 4b, which illustrate a manual control system for HVAC of a vehicle in cooling zone and heating zone respectively, according to an embodiment of the present invention.
[0049] Figure 4a illustrates manual control system for HVAC of a vehicle when the required temperature selected by the knob is in the cooling zone (300a). Figure 4b illustrates manual control system for HVAC of a vehicle when the required temperature selected by the knob is in the heating zone (300b).
[0050] The manual control system for HVAC of a vehicle comprises a temperature knob (300) to select a required temperature of air inside a vehicle cabin. The temperature knob (300) is rotated to select the required temperature from a range of temperature divided in the cooling zone (300a) and the heating zone (300b). A thermistor is connected to the temperature knob (300) [not shown in figure]. Resistance of the thermistor is changed by rotating the temperature knob.
[0051] AC compressor (not shown in figure) is switched on via AC switch (700) to reduce temperature of air till cut off temperature of the compressor. The cut-off temperature is based on resistance of the variable thermistor set

by rotating the temperature knob (300). The compressor is switched off at the cut-off temperature.
[0052] Air from the evaporator (401) enters into the first compartment (406). Further, a second compartment (402) is connected to a heater (403). A hot air damper (407) separates the first compartment (406) and the second compartment (402). The hot air damper (407) is moved to create and to vary an opening between the first compartment (406) and the second compartment (402). The air entering into the second compartment (402) from the first compartment (406) gets heated inside a heater (403).
[0053] A passage (405) is provided where air heated inside the heater (403) mixes with air from the first compartment (406) to produce air at the required temperature to supply inside the vehicle cabin.
[0054] When the required temperature selected by rotating the knob (300) is from the cooling zone (300a), the cut off temperature of the compressor is set according to the required temperature. As the required temperature varies in the cooling zone (300a), the cut off temperature of the compressor is also changed accordingly.
[0055] Also, in such condition, as shown in figure-4a, the hot air damper (407) closes the opening between the first compartment (406) and the second compartment (402). Air from cabin or outside of vehicle enters into the evaporator, in a direction represented by arrow-1 (10) where it gets cooled up to the required temperature. Cooled air from the evaporator (401) enters into the first compartment (406) in a direction represented by arrow-2 (20). Air from the first compartment (406) enters into the vehicle cabin, after passing through the passage (405) in a direction represented by arrow-3 (30).

[0056] When the required temperature is from the heating zone (300b), the cut off temperature of the compressor is set to the fixed value, for example, 2°C. In heating zone (300b), it is evident that the air entering in the evaporator is already at a low temperature and hence further cooling is not required. Thus, compressor can be kept off during heating zone by switching it off using A/C Switch (700) (as shown in figure-3). This reduces the energy wastage in operating the compressor when not required.
[0057] Also, in such condition, as shown in figure-4b, the hot air damper (407) varies amount of the opening between the first compartment (406) and the second compartment (402) based on the required temperature.
[0058] Air from cabin or outside of vehicle enters into the evaporator, in a direction represented by arrow-1 (10). As the required temperature selected is in heating zone, the resistance of the thermistor is at a fixed value and the cut off temperature of the compressor is kept at fixed value, for example 2°C. The AC compressor can be switched off via AC switch (700) and no cooling of air occurs.
[0059] Air from evaporator (401) enters into the first compartment (406). The opening between the first compartment (406) and the second compartment (402) varies based on amount of heating of air required to reach temperature of air equal to the required temperature selected by rotating knob (300) in the heating zone (300b). Higher the heating of air required, higher is the opening between the first compartment (406) and the second compartment (402) and more amount of air enters from the first compartment (406) into the second compartment (402) for heating. Arrow-4 (40) represents a portion of air entering from the first compartment (406) into the second compartment (402) through the opening. The air from the second compartment gets heated by the heater (403) and enters into a heater

chamber (404). Air heated at an elevated temperature by the heater (403), enters into the passage (405) from the heater chamber (404) in a direction represented by arrow-5 (50). Air from the first compartment (406) also enters into the passage (405) in a direction represented by arrow-2 (20). Air heated at an elevated temperature from the heater chamber (404) and air from the first compartment (406) mix in the passage (405) to produce air with the required temperature, which is supplied to the vehicle cabin in a direction represented by arrow-3 (30).
[0060] Figures 5a to 5d illustrate a manual control system for HVAC comprising a spur gear (500) with teeth on a part of its circumference, having an integrated mechanism with the temperature knob (300) to control movement of the hot air damper (407), according to an embodiment of the present invention.
[0061] Figures 5a represents the temperature knob (300), a spur gear (500) with teeth on a part of its circumference, and an assembly of a manual control system for HVAC comprising the same. The spur gear (500) is having teeth on a first part of its circumference and a circular arc shape on a second part of its circumference. An integrated mechanism is established to rotate the spur gear (500) in a clockwise direction or an anti-clockwise direction by rotating the temperature knob (300) in an anti-clockwise direction or a clockwise direction, respectively. Further, the spur gear (500) engages with the hot air damper (407) in an engagement zone (i.e., a first part of circumference having teeth) to move the hot air damper (407).
[0062] When the temperature knob (300) is in cooling zone (i.e., from la to 2a in figure 3) and rotated in clockwise direction (A), i.e., from the indicator (la) (the lowest temperature of the cooling zone) to the indicator (2a) (the highest temperature of the cooling zone), the spur gear (500) rotates in an

anti-clockwise direction (B) as shown in figures 5a and 5b. As there are no teeth on the spur gear for first half of rotation, the spur gear does not engage the hot air damper (407) and hence no movement of the hot air damper (407) occurs. An arrow-1 (10) represents direction of air entering into the evaporator (401). An arrow-2 (20) represents direction of air flowing through the first compartment (402). An arrow-3 (30) represents direction of air flowing through the passage (405) towards the vehicle cabin.
[0063] Figures 5b represents temperature knob (300) rotates from the indicator (la) (the lowest temperature in cooling zone) to the indicator (2a) (the highest temperature in cooling zone) in a clockwise direction (Al). The spur gear rotates in an anti-clockwise direction (Bl). During rotation in the cooling zone (300a), the spur gear (500) does not engage with the hot air damper (407) as the circular arc shape on the second part of the spur gear (500) remains in the disengagement zone. Therefore, the hot air damper (407) does not move and no opening is created between the first compartment (402) and the second compartment (406). The cut off temperature of the compressor is set according to the required temperature set by the user, by rotating the temperature knob (300).
[0064] Higher the rotation of the temperature knob (300) in the cooling zone in the clockwise direction (Al), higher is the cut off temperature and lesser is cooling done. The arrow-1 (10) represents direction of air entering into the evaporator (401). The arrow-2 (20) represents direction of air flowing through the first compartment (406). The arrow-3 (30) represents direction of air flowing through the passage (405) toward the vehicle cabin.
[0065] Figure 5c and Figure 5d represent rotation of the temperature knob in the heating zone (300b). Figure 5c represents the temperature knob (300) rotates from the indicator (2a) (the highest temperature in cooling zone) to

the indicator (3c) (a temperature in heating zone) in a clockwise direction (A2). Figure 5d represents rotation of the temperature knob (300) from the indicator (3c) to the indicator (4b) (the highest temperature in heating zone) in a clockwise direction (A3). As shown in figure 5c and figure 5d, the spur gear rotates in an anti-clockwise direction (B2, B3). In this duration, the teeth on the first part of the circumference of the spur gear (500) engages with the hot air damper (407) in the engagement zone. Therefore, as the hot air damper (407) rotates, the opening is created between the first compartment (402) and the second compartment (406). In the heating zone, the cut off temperature of the compressor is set to a fixed value (for example, 2°C). However, compressor can be switched off using AC switch 700 manually by user. No cooling of air occurs in the heating zone (300b). Higher the rotation of the temperature knob (300) in the heating zone in the clockwise direction (A2, A3), higher is rotation of the spur gear (500) in the heating zone and higher is heating done.
[0066] The arrow-1 (10) represents direction of air entering into the evaporator (401) from vehicle cabin or outside of vehicle. The arrow-2 (20) represents direction of air from evaporator (401) flowing through the first compartment (402) and the arrow-3 (30) represents direction of air after being heated with air flowing through the heater chamber (404) toward the passage (405). Figure 5d shows a condition of maximum heating, when all the air from the evaporator (401) is passed through the heater (403) and heated air is supplied to the cabin. As shown in figure-5c, the air after mixing of air from the first compartment (406) and air after heating from the heater chamber (404) is provided to vehicle cabin. Further, as shown in figure-5d, the air after heating from the heater chamber (404) at a maximum heating condition is provided to vehicle cabin. Therefore, the improved technology for manual control of automobile HVAC is provided that

facilitates efficient utilization of energy in the HVAC process of a vehicle to achieve require temperature inside the vehicle cabin. No energy is wasted in first cooling air and then heating air to achieve the required temperature inside the vehicle cabin.
[0067] Fig. 6 illustrate a method for controlling the HVAC of a vehicle.
[0068] At step 601, the method includes selecting a required temperature, from a range of temperature divided in a cooling zone (300a) and a heating zone (300b), of air by rotating a temperature knob (300).
[0069] At step 603, the method includes setting resistance of a thermistor connected to the temperature knob (300) by rotating the temperature knob (300).
[0070] At step 605, the method includes reducing temperature of air to a cut off temperature of a compressor connected to the evaporator (401). The cut¬off temperature is based on resistance of the thermistor set by rotating the temperature knob (300). The compressor is switched off at the cut-off temperature.
[0071] The method further includes increasing temperature of air by moving a hot air damper (407) to create and vary an opening between a first compartment (406) and a second compartment (402) and allowing entry of air from the evaporator (401) into the first compartment (406); allowing entry of air from the first compartment (406) into the second compartment (402).
[0072] The method step 607 includes heating the air by a heater (403) connected to the second compartment (402) and entering the heated air into a heater chamber (404); and mixing air from the first compartment (406) and

the heated air from the heater chamber (404) in a passage (405) to produce air at the required temperature to be supplied inside the vehicle cabin.
[0073] The method includes setting, the cut off temperature of the compressor according to the required temperature, and closing the opening between the first compartment (406) and the second compartment (402), if the required temperature is from the cooling zone (300a), and setting, the cut off temperature of the compressor equal to a fixed value, and varying, by the hot air damper (407), the opening between the first compartment (406) and the second compartment (402) based on the required temperature, if the required temperature is from the heating zone (300b).
[0074] The thermistor acts as a variable thermistor in the cooling zone (300a) and acts as a fixed thermistor in the heating zone (300b).
[0075] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0076] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/ plural permutations may be expressly set forth herein for sake of clarity.
[0077] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the

appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles, 'a', or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations).
[0078] The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and

materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.
[0079] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[0080] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
[0081] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

We claim:

1.A manual control system for HVAC of a vehicle comprising:
a temperature knob (300) to select a required temperature of air inside a vehicle cabin, the temperature knob (300) is rotated to select the required temperature from a range of temperature divided in a cooling zone (300a) and a heating zone (300b);
a thermistor connected to the temperature knob (300), wherein resistance of the thermistor is set by rotating the temperature knob (300);
an evaporator (401), wherein air from vehicle cabin or outside of the vehicle enters into the evaporator (401);
a compressor connected to the evaporator (401) to reduce temperature of air to a cut off temperature, the cut-off temperature is based on resistance of the thermistor set by rotating the temperature knob (300), wherein the compressor is switched off at the cut-off temperature;
a first compartment (406), wherein air from the evaporator (401) enters into the first compartment (406);
a second compartment (402) connected to a heater (403), wherein air entering into the second compartment (402) from the first compartment (406) gets heated by the heater (403) and enters into a heater chamber (404);
a passage (405), wherein air heated inside the heater (403) mixes with air from the first compartment (406) in the passage (405) to produce air at the required temperature to be supplied inside the vehicle cabin; and
a hot air damper (407) to separate the first compartment (406) from the second compartment (402), wherein the hot air damper (407)

is moved to create and to vary an opening between the first compartment (406) and the second compartment (402), characterized in that:
if the required temperature is from the cooling zone (300a), the cut off temperature of the compressor is set according to the required temperature and the hot air damper (407) closes the opening between the first compartment (406) and the second compartment (402), and
if the required temperature is from the heating zone (300b), the cut off temperature of the compressor is set equal to a fixed value and the hot air damper (407) varies the opening between the first compartment (406) and the second compartment (402) based on the required temperature.
2. The manual control system for HVAC of a vehicle as claimed in claim 1, wherein if the required temperature selected by the temperature knob (300) is from the cooling zone (300a), no heating of air occurs.
3. The manual control system for HVAC of a vehicle as claimed in claim 1, wherein the thermistor acts as a variable thermistor in the cooling zone (300a) and acts as a fixed thermistor in the heating zone (300b).
4. The manual control system for HVAC of a vehicle as claimed in claim 1, wherein if the required temperature selected by the temperature knob (300) is from the heating zone (300b), AC switch (700) is manually switched off and no cooling of air occurs.
5. The manual control system for HVAC of a vehicle as claimed in claim 1, wherein to increase the required temperature in the heating zone (300b) the opening is increased.

6. The manual control system for HVAC of a vehicle as claimed in claim 1, wherein a spur gear (500) having an integrated mechanism with the temperature knob (300), engages with the hot air damper (407) to control movement of the hot air damper (407), the spur gear (500) is having a plurality of tooth on one part of its circumference and a circular arc shape on another part of its circumference.
7. The manual control system for HVAC of a vehicle as claimed in claim 6, wherein the spur gear (500) is not engaged with the hot air damper (407) when the temperature knob (300) is in the cooling zone (300a).
8. The manual control system for HVAC of a vehicle as claimed in claim 6, wherein the plurality of tooth of the spur gear (500) is engaged with the hot air damper (407) to vary the opening between the first compartment (406) and the second compartment (402) when the temperature knob (300) is in the heating zone (300a).
9. A method (600) for manual control system for HVAC of a vehicle comprising:
selecting (601) a required temperature, from a range of temperature divided in a cooling zone (300a) and a heating zone (300b), of air inside a vehicle cabin by rotating a temperature knob (300);
setting (603) resistance of a thermistor connected to the temperature knob (300) by rotating the temperature knob (300);
allowing entry of air from vehicle cabin or outside of the vehicle into the evaporator (401);

reducing (603) temperature of air to a cut off temperature of a compressor connected to the evaporator (401), the cut-off temperature is based on resistance of the thermistor set by rotating the temperature knob (300), wherein the compressor is switched off at the cut-off temperature, the reducing temperature of air comprising:
moving a hot air damper (407) to create and vary an opening between a first compartment (406) and a second compartment (402),
entering air from the evaporator (401) into the first compartment (406);
entering air from the first compartment (406) into the second compartment (402);
heating the air by a heater (403) connected to the second compartment (402) and entering the heated air into a heater chamber (404); and
mixing air from the first compartment (406) and the heated air from the heater chamber (404) in a passage (405) to produce air at the required temperature to be supplied inside the vehicle cabin,
characterized in that:
setting, the cut off temperature of the compressor according to the required temperature, and closing the opening between the first compartment (406) and the second

compartment (402), if the required temperature is from the cooling zone (300a), and
setting, the cut off temperature of the compressor equal to a fixed value, and varying, by the hot air damper (407), the opening between the first compartment (406) and the second compartment (402) based on the required temperature, if the required temperature is from the heating zone (300b).
10. The method for manual control system for HVAC of a vehicle as claimed in claim 9, wherein the thermistor acts as a variable thermistor in the cooling zone (300a) and acts as a fixed thermistor in the heating zone (300b).