CA2247660A1 - Protection apparatus for compressor and controlling method of the same - Google Patents
Protection apparatus for compressor and controlling method of the same Download PDFInfo
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- CA2247660A1 CA2247660A1 CA 2247660 CA2247660A CA2247660A1 CA 2247660 A1 CA2247660 A1 CA 2247660A1 CA 2247660 CA2247660 CA 2247660 CA 2247660 A CA2247660 A CA 2247660A CA 2247660 A1 CA2247660 A1 CA 2247660A1
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- rotational frequency
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Abstract
A compressor protection apparatus and a method for controlling a compressor protection apparatus that prevents unnecessarily frequent on/off cycling of the electromagnetic clutch and, at the same time, prevents catastrophic damage of the compressor due to leakage of the refrigerant, are disclosed. In this control method, if a state of high engine rotational frequency has lasted for a certain duration, the electromagnetic clutch will be switched off temporarily. The control method takes into account the duration of high or normal engine rotational frequency, and thus prevents unnecessarily frequent on/off cycling of the electromagnetic clutch. Also the control method checks the compressor temperature when the engine rotational frequency is in a normal range. If the temperature is greater than a critical value, the electric power supply to the electromagnetic clutch is irreversibly switched off to inhibit the continued operation of the compressor. Therefore, the control method is able to stop the compressor by detecting a condition in which a refrigerant leakage is likely and, thus, prevent catastrophic damage to the compressor.
Description
PROTECTION APPARATUS FOR COMPRESSOR AND
CONTROLLrNG METHOD OF THE SAME
S BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to a protection appal~lus for a refrigerant compressor used in an automotive air-conditioning system, and its controlling method. More particularly, it relates mainly to a controlling method for stopping the electric power supply to the 10 electromagnetic clutch of the compressor.
CONTROLLrNG METHOD OF THE SAME
S BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to a protection appal~lus for a refrigerant compressor used in an automotive air-conditioning system, and its controlling method. More particularly, it relates mainly to a controlling method for stopping the electric power supply to the 10 electromagnetic clutch of the compressor.
2. Description of the Prior Art Generally, a refrigerant compressor used for a vehicular air conditioning system is driven by the engine of the vehicle. A portion of the output of the engine of the vehicle rotates a pulley of the compressor via a driving belt at all times. An electromagnetic clutch 15 provided on the compressor, controls the coupling of the pulley and the drive shaft of the compressor. Usually, if the vehicular air conditioning system is turned on when the COllll)~llllelll in the vehicle is warm, then the electromagnetic clutch is activated by receiving electric power and the pulley and the drive shaft of the compressor are coupled together.
And thus, the compressor is driven to start the operation ofthe refrigerant circuit, i.e., the 20 operation of the air conditioning system.
As long as the electrom~gnetic clutch is supplied with its activating electric power, the col,lp,essor is driven. Occasionally, if not frequently, however, something wrong occurs within the colllpl~ssor to make it difficult to rotate the compressor. In an extreme case, the compressor locks up. If the compressor is forced to rotate under such conditions, the inner 25 me~h~nicm of the coll~ressor will be destroyed, the clutch plate of the electrom~gnetic clutch will burn, and the driving belt of the compressor will break, when the worst comes to the worst.
To protect the compressor from such damage, conventional systems provide a thermal switch in the electric power line for the electromagnetic clutch.
With reference to Fig. 1, the electric power is supplied to the electromagnetic clutch 2 ofthe co"ll)lessor 1, via thermal switch S0. The thermal switch S0 may be either fixed on the body of the compressor 1, or incorporated within the electromagnetic clutch 2.
DCOI :19234Z.I - 1 -During normal operation, the thermal switch S0 is closed to activate the electromagnetic clutch 2 to enable the operation of the compressor 1 When an abnormal condition occurs within compressor 1, for example, the te-,-pe.~ re of the co-.~pressor increases to a certain te..lpe~ re Tc, the thermal switch S0 opens Then, the 5 electromagnetic clutch 2 is de-activated and the rotation of the drive shaft of the compressor 1 is stopped When the temperature of the compressor 1 decreases back to a normaltemperature, the thermal switch S0 closes spontaneously to make the operation of the compressor 1 possible again The above conventional protection method for the compressor, however, has the 10 following problems (1) Generally, the working temperature Tc of the thermal switch S0 is chosen to be rather low That is, Tc is chosen to help ensure the safety of the compressor The engine rotational frequency, however, becomes high sometimes during normal traveling of the vehicle When the rotational frequency of the engine becomes high, the temperature of the 15 co-..~)-t;ssor rises t~ )o.~ily even if there is no abnormality in compressor 1 If this occurs, the thermal switch S0 opens to de-activate electromagnetic clutch 2, and to stop the rotation ofthe drive shaft of conlplessor 1 When compressor 1 stops, the refrigerative operation of the air conditioning system also stops Thus, there is a problem that the thermal switch S0 works ~mnece,ss~rily often, and the co-..p~l-..e-lt ofthe vehicle is not cooled enough If there 20 is no abnormality in the compressor or in the refrigeratory circuit, this unnecessary working of the thermal switch S0 is a misoperation of the compressor protection appa- ~ s (2) If there is leakage somewhere in the refrigerant circuit of the air conditioning system, the refrigerant gas gradually leaks out of the refrigerant circuit Generally, the refrigerant gas is mixed with a lubricating oil for co...plessor 1 Therefore, if there is leakage 25 in the refrigerant circuit, the lubricating oil for compressor 1 also leaks out If lubricating oil for compressor 1 leaks out, the temperature of compressor 1 may rise to the working temperature of the thermal switch S0 even if the engine is rotating at a normal frequency If switch S0 is opened, the electrom~gnetic clutch 2 is de-activated and compressor 1 is stopped The opening of the thermal switch S0, by itself, does not adversely effect the 30 co...~.~ssor Nevertheless, when the compressor temperature decreases again due to a drop in the engine rotational frequency, the thermal switch S0 closes again to activate the ele~;l-on agnetic clutch 2 Then, when the engine rotational frequency rises to a normal level, DC01:192342.1 -2-the thermal switch S0 opens again due to the shortage of lubricant. Thus, if the air conditioning system is operated when there is some leakage in the refrigerant circuit, the thermal switch S0 will open and close repeatedly, even if the engine rotational frequency remains at a normal, moderate level. Meanwhile, because the passenger is not aware of the 5 malfunction, the air conditioning system continues to operate. During such operation, refrigerant and lubricating oil continue to leak, and the shortage of lubricating oil becomes extreme. With continued operation of the air conditioning system in such a condition, the co",l~lessor will break down. Specifically, the internal mech~nicm of the compressor will be destroyed, the clutch plate of the elecllo,llagnetic clutch will burn, or the drive belt will 10 break. This problem is caused by an incompleteness of the compressor protection appal~ s.
The second problem maybe alleviated by replacing the thermal switch S0 with a thermal fuse. This is only advantageous when there is a leak in the refrigeratory circuit.
When there is a leak, the thermal fuse blows due to the increase of the compressor temperature. The passenger of the vehicle knows the fuse has blown and thus, knows to 15 make an inspection of the air conditioning system. By an inspection ofthe air conditioning system, the leakage may be found and fixed. On the other hand, if there is no leakage, the compressor temperature may reach the melting temperature of the thermal fuse due to the occasional high rotational speed ofthe vehicular engine, as explained in conjunction with the first problem above. Nevertheless, the thermal fuse blows out in this case also. Therefore, 20 whether there is a leak or not, the passenger of the vehicle will believe an inspection of the air conditioning system is necessary. To avoid such an Imnececs~ry inspection, a reversible thermal switch is preferable after all.
Accordingly, the compressor protection apparatus must solve both of the above described problems cimlllt~neously As explained above, neither the conventional thermal 25 switch nor the conventional thermal fuse, alone, solves both problems simultaneously.
Thus, it has long been desired to provide a compressor protection apparatus and a method for controlling a col"~"~ssor protection apparatus that solve the above two problems .cim~llt~neously.
It is the primary object of the present invention to provide a compressor protection apparatus and a method for controlling a co~ples~or protection apparatus that, in a condition DC01:192342.1 -3-of no leakage, does not misoperate even if the engine rotational frequency occasionally increases to a high range. It is another object of the present invention to provide a compressor protection apparatus and a method for controlling a compressor protection apparatus that, in a condition of leakage, disables the continued operation of the refrigeratory circuit to prevent the final catastrophic destruction of the compressor, and to oblige the passenger to inspect the air conditioning system.
The method for controlling a compressor protection apparatus according to the present invention may be implemented in software and installed in the following appal al~ls.
Specifically, a co~p~ssor protection appa~al~ls having as inputs a signal from a temperature 10 sensor ~tt~c.h~d to the compressor, and a signal representing the engine rotational frequency from an engine control apparatus. The compressor protection apparatus includes two tandemly connected switches that control the activation or de-activation of the electromagnetic clutch. Functionally, one of the two switch is a temporary (or reversible) switch that can be re-closed to make contact by the software. The second of the two 15 switches is a breaker-type switch that can not be re-closed to make contact by the software.
The method of controlling a co"lpiessor protection apparatus according to the present invention provides an algorithm for controlling the opening or closing of the two switches based a compressor temperature signal and an engine rotational frequency signal.
The method of controlling the compressor protection apparatus includes a number 20 of features. The algorithm breaks contact of a breaker-type switch in the protection apparatus to prevent contin-led operation ofthe ~ige~lo~y circuit when the engine rotation speed is in a normal range and the con,plessor temperature is abnormally high at the same time. This feature prevents the catastrophic destruction of the compressor. Moreover, if the engine rotational frequency is m~int~ined in a high range for a certain time duration, the 25 algorithm breaks contact of a temporary switch in the protection apparatus and thus temporarily prevents continued operation of the compressor. In this situation, the refrigeratory circuit can be restarted again after some time. This feature, that is based on monitoring the time duration of high rotational frequency of the vehicular engine, prevents unnecessarily frequent on/off operation of the electromagnetic clutch.
The compressor protection apparatus according to the embodiments of the present invention can be embodied in various electronic or electric circuits that are part of current electronic technology.
DC01:192342.1 -4-Other objects, features, and advantages of this invention will be understood from the following detailed description of the p~erel,ed embodiment of this invention with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a s~h~",~ic circuit of a compressor protection apparatus according to the prior art.
Figure 2 is a sehçm~tic circuit of a col~,~ressor protection apparatus according to one embodiment of the present invention.
Figure 3 is flow chart of a method for controlling a compressor protection apparatus 10 according to one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In Fig. 2, a compressor 1 and a control unit 3 into which the compressor protection software according to the present invention, is installed, are schematically depicted. An engine rotational frequency signal from an engine control unit (not shown), and a compressor 15 temperature signal from complessor te"")e,~ re sensor 4, are input to control unit 3 . Power for activating the electromagnetic clutch 2 is supplied through two t~n-lçmly connected switches S1 and S2 that are provided within control unit 3. The switch S1 is opened or closed by control unit 3, while the switch S2 is a one-way switch, i.e., a breaker-type switch that can not be closed by control unit 3 once it has been opened. The switch S2 can be reset 20 (i.e., closed) m~n~l~lly during an inspection ofthe air conditioning system in a garage. The co"~plessor protection software controls the opening and closing of the two switches S 1, S2, based on information about the engine rotational frequency and compressor temperature.
Now, the method for controlling the two switches S 1, S2, i.e., the control software, will be explained with ~r~lence to Fig. 3. In the following explanation, the point of reference 25 on the flow chart is referred to as a cursor for convenience.
First, in box 11, h~""ation about the engine rotational frequency, r, and the co",p,essor temperature, t, are taken into control unit 3. Then, the cursor proceeds to box 12, in which the engine rotational frequency, r, is compared with a constant R1, where R1 is determined by experiment to be a boundary value between a high engine rotational 30 frequencv range and a normal engine rotational frequency range. Inequality r> R1 means a state in which the engine rotational frequency is higher than normal range. If the inequality r>R1 is satisfied, the cursor moves to box 13. In box 13 a determination is made as to DC01:1923421 -5-whether the r>Rl state has lasted for a certain time T1. The time constant Tl is determined experim~nt~lly to be an appropriate value. If the answer to this question is No, the cursor retums to box 11, and the same operations are repeated. This sequence comprised of boxes 11-12-13-11 conitit-1tes a closed loop Ll indicated in Fig. 3. During loop L1, 5 electrom~netic clutch 2 remains activated.
If, in box 13, the answer is Yes, that is, the r~R1 state has lasted for a certain time T1, the cursor will move to box 14, in which the switch S1 is opened to de-activate electrom~netic clutch 2. Subsequently the cursor moves to box 15, in which the engine rotational frequency, r, is taken in the control unit 3 again. Then the cursor moves to boxes 16,17. In box 16, it is determined whether r<R2 holds, where R2 is a constant chosen to be smaller than the con~ l R1 given previously. In box 17, it is determined whether the r<R2 state has lasted for a certain time T2. The time constant T2 is determined experimentally to be an appl~)p,iate value. As can be seen from Fig. 3, the No branch from box 16 returns back to itself, and the No branch from the box 17 returns back to the box 15. Thus, during the loop conitituted by boxes 15-16-17-15, control unit 3 waits until the r<R2 state has continued for a time T2. If the r<R2 state has continued for a time T2, then the cursor moves to box 18, in which the switch S 1 is closed to activate the electromagnetic clutch 2 again. Then the cursor retums to box 11. This control sequence comprised of boxes 11-12-13-14-15-16-17-18-11 constitutes a large closed loop L2 indicated in Fig. 3. During one cycle of loop L2, the electrom~gnPtic clutch 2 is temporarily opened and closed again.
Retuming now to box 11, in which il~o~ lion about the engine rotational frequency, r, and the conlpl essor temperature, t, are taken into the control unit 3, the renn~inder of the control functionality is explained. From box 11, the cursor moves to the box 12 as before.
This time, consider the case in which the answer to the question whether r>R1 or not, is No.
That is, it is determined in box 12 that the engine rotational frequency is in a normal range.
Then the cursor moves to box 19, in which the compressor temperature, t, is compared with a certain constant Tc. If the answer to the question whether t>Tc or not, is No, the cursor retums back to the box 11. If it is determined that t>Tc does not hold, then the compressor t~ lalllre, t, is lower than the critical temperature Tc, i e., there is no abnormality within the colllplessor. As indicated in Fig. 3, the sequence comprised of boxes 11-12-19-11 constitutes a third closed loop L3. During loop L3, electromagnetic clutch 2 remains activated.
DC01:192342.1 -6-For the final case, control is returned to box 1 1 again. In box 1 1, information of the engine rotational frequency, r, and the compressor temperature, t, are taken into control unit 3. The cursor then moves to box 12 as before. Now consider the case in which the answer to the question whether or not r>R1 is No, in order to explain the final control path. If the 5 answer to the question in box 12 is No, then the cursor moves to box 19, in which the compressor temperature, t, is compared with the critical temperature Tc. If there exists a leakage in the refrigeratory circuit, and the leakage has progressed to some degree, the compressor temperature increases due to the shortage of lubricating oil in the compressor even though the compressor is driven at moderate engine rotational frequency. In such a 10 case, compressor temperature rises and the answer to the question whether or not t>Tc is Yes. The cursor proceeds to the boxes 20 and 21, and finally reaches the END of the control flow. In box 20, breaker switch S2 is opened to de-activate electromagnetic clutch 2, and disable continued operation of the air conditioning system. Box 21 represents a procedure of inspection and repair for the system. The breaker switch S2 can only be closed m~n~1~11y 15 during such an inspection and repair procedure. Unless the procedure of inspection and repair is made, the air conditioning system can not be operated again. Thus, the method of controlling a compressor protection apparatus end with a one-way path, P, comprised of boxes 11-12-19-20-21, as indicated in Fig. 3.
To put together all the above explanations, the trajectory of the cursor will be as 20 follows. If there is no leakage in the l~iigel~tory circuit and the engine rotational frequency is in the normal range, the cursor circulates on the closed loop L3 and the electrom~gnetic clutch remains activated. When the engine rotational frequency increases to high range occasionally, but does not l"~ such state for a duration T1, the cursor circulates on the closed loop L1 and the electrom~gnetic clutch remains activated also. If the state of high 25 engine rotational frequency has lasted longer than the time T 1, the cursor enters the closed loop L2. During the closed loop L2, the switch S 1 is opened temporarily to de-activate the electromagnetic clutch t~lllpol~ily. That is, the compressor is disconnected from the engine and protected from possible damage. When the cursor traces the closed loop L2, the opening and closing of the switch S1 is controlled by comparing the time duration of high engine 30 rotational frequency with a time constant T1 and by colllpaling the time duration of normal engine rotational frequency state with a time constant T2. The switch S1 only opens or closes when the time duration of the high engine rotational frequency exceeds a time constant DC01:192342.1 -7-T1 or when the time duration of normal engine rotational frequency exceeds a time constant T2. Due to the introduction of con~ times T 1, T2, the opening and closing of the switch S1, i e., the on/off of the electrom~gnetic clutch is fairly stable when compared with conventional systems. That is, by circ~ tin~ around either one ofthe closed loops L1, L2 or L3, the control unit 3 prevents unnecessarily frequent turning on/off of the electrom~gnetic clutch.
During normal operation of the air conditioning system, the cursor is circ~ tingaround either one ofthe three closed loops L3, LI, or L2, for example, L3-L3-L1-L2-LI-as described above. But, if there is a leakage in the refrigeratory circuit that has progressed to some degree, the cursor goes into the one-way path P that branches at the box 19. And, then, in the box 20, breaker switch S2 is opened to de-activate the electromagnetic clutch semi-perm~nently. This path P is one-way, and, thus, the breaker switch S2 does not close automatically. The breaker switch S2 can only be closed m~nll~lly, for example, during an inspection in a garage. Namely, by providing the one-way path P in the control flow, serious damage ofthe colllplessor, which eventually occurs in conventional systems when there is leakage in the refrigeratory circuit, is prevented.
Further, with reference to Fig. 2 again, although both of the two switches are inserted tandemly in the electric power line to the electrom~ netic clutch 2, the breaker switch S2 may be anywhere within the circuit of the control unit 3 . For example, a single switch S 1, that is given both of the functions of temporary opening and irreversible opening, may be inserted in the electric power line to the electromagnetic clutch 2. In this case, breaker switch S2 is replaced with a reset switch of control unit 3. Therefore, when an irreversible opening of switch S1 has occurred (due to a leakage of refrigerant gas and lubricating oil), it only may be closed by the reset switch.
Although the present invention has been described in detail in connection with pl~r~lled embodiment, the invention is not limited thereto. It will be understood by those of ordinary skill in the art that variations and modifications may be made within the scope of this invention, as defined by the following claims.
DC01:192342.1 -8-.. .. .. . . .
And thus, the compressor is driven to start the operation ofthe refrigerant circuit, i.e., the 20 operation of the air conditioning system.
As long as the electrom~gnetic clutch is supplied with its activating electric power, the col,lp,essor is driven. Occasionally, if not frequently, however, something wrong occurs within the colllpl~ssor to make it difficult to rotate the compressor. In an extreme case, the compressor locks up. If the compressor is forced to rotate under such conditions, the inner 25 me~h~nicm of the coll~ressor will be destroyed, the clutch plate of the electrom~gnetic clutch will burn, and the driving belt of the compressor will break, when the worst comes to the worst.
To protect the compressor from such damage, conventional systems provide a thermal switch in the electric power line for the electromagnetic clutch.
With reference to Fig. 1, the electric power is supplied to the electromagnetic clutch 2 ofthe co"ll)lessor 1, via thermal switch S0. The thermal switch S0 may be either fixed on the body of the compressor 1, or incorporated within the electromagnetic clutch 2.
DCOI :19234Z.I - 1 -During normal operation, the thermal switch S0 is closed to activate the electromagnetic clutch 2 to enable the operation of the compressor 1 When an abnormal condition occurs within compressor 1, for example, the te-,-pe.~ re of the co-.~pressor increases to a certain te..lpe~ re Tc, the thermal switch S0 opens Then, the 5 electromagnetic clutch 2 is de-activated and the rotation of the drive shaft of the compressor 1 is stopped When the temperature of the compressor 1 decreases back to a normaltemperature, the thermal switch S0 closes spontaneously to make the operation of the compressor 1 possible again The above conventional protection method for the compressor, however, has the 10 following problems (1) Generally, the working temperature Tc of the thermal switch S0 is chosen to be rather low That is, Tc is chosen to help ensure the safety of the compressor The engine rotational frequency, however, becomes high sometimes during normal traveling of the vehicle When the rotational frequency of the engine becomes high, the temperature of the 15 co-..~)-t;ssor rises t~ )o.~ily even if there is no abnormality in compressor 1 If this occurs, the thermal switch S0 opens to de-activate electromagnetic clutch 2, and to stop the rotation ofthe drive shaft of conlplessor 1 When compressor 1 stops, the refrigerative operation of the air conditioning system also stops Thus, there is a problem that the thermal switch S0 works ~mnece,ss~rily often, and the co-..p~l-..e-lt ofthe vehicle is not cooled enough If there 20 is no abnormality in the compressor or in the refrigeratory circuit, this unnecessary working of the thermal switch S0 is a misoperation of the compressor protection appa- ~ s (2) If there is leakage somewhere in the refrigerant circuit of the air conditioning system, the refrigerant gas gradually leaks out of the refrigerant circuit Generally, the refrigerant gas is mixed with a lubricating oil for co...plessor 1 Therefore, if there is leakage 25 in the refrigerant circuit, the lubricating oil for compressor 1 also leaks out If lubricating oil for compressor 1 leaks out, the temperature of compressor 1 may rise to the working temperature of the thermal switch S0 even if the engine is rotating at a normal frequency If switch S0 is opened, the electrom~gnetic clutch 2 is de-activated and compressor 1 is stopped The opening of the thermal switch S0, by itself, does not adversely effect the 30 co...~.~ssor Nevertheless, when the compressor temperature decreases again due to a drop in the engine rotational frequency, the thermal switch S0 closes again to activate the ele~;l-on agnetic clutch 2 Then, when the engine rotational frequency rises to a normal level, DC01:192342.1 -2-the thermal switch S0 opens again due to the shortage of lubricant. Thus, if the air conditioning system is operated when there is some leakage in the refrigerant circuit, the thermal switch S0 will open and close repeatedly, even if the engine rotational frequency remains at a normal, moderate level. Meanwhile, because the passenger is not aware of the 5 malfunction, the air conditioning system continues to operate. During such operation, refrigerant and lubricating oil continue to leak, and the shortage of lubricating oil becomes extreme. With continued operation of the air conditioning system in such a condition, the co",l~lessor will break down. Specifically, the internal mech~nicm of the compressor will be destroyed, the clutch plate of the elecllo,llagnetic clutch will burn, or the drive belt will 10 break. This problem is caused by an incompleteness of the compressor protection appal~ s.
The second problem maybe alleviated by replacing the thermal switch S0 with a thermal fuse. This is only advantageous when there is a leak in the refrigeratory circuit.
When there is a leak, the thermal fuse blows due to the increase of the compressor temperature. The passenger of the vehicle knows the fuse has blown and thus, knows to 15 make an inspection of the air conditioning system. By an inspection ofthe air conditioning system, the leakage may be found and fixed. On the other hand, if there is no leakage, the compressor temperature may reach the melting temperature of the thermal fuse due to the occasional high rotational speed ofthe vehicular engine, as explained in conjunction with the first problem above. Nevertheless, the thermal fuse blows out in this case also. Therefore, 20 whether there is a leak or not, the passenger of the vehicle will believe an inspection of the air conditioning system is necessary. To avoid such an Imnececs~ry inspection, a reversible thermal switch is preferable after all.
Accordingly, the compressor protection apparatus must solve both of the above described problems cimlllt~neously As explained above, neither the conventional thermal 25 switch nor the conventional thermal fuse, alone, solves both problems simultaneously.
Thus, it has long been desired to provide a compressor protection apparatus and a method for controlling a col"~"~ssor protection apparatus that solve the above two problems .cim~llt~neously.
It is the primary object of the present invention to provide a compressor protection apparatus and a method for controlling a co~ples~or protection apparatus that, in a condition DC01:192342.1 -3-of no leakage, does not misoperate even if the engine rotational frequency occasionally increases to a high range. It is another object of the present invention to provide a compressor protection apparatus and a method for controlling a compressor protection apparatus that, in a condition of leakage, disables the continued operation of the refrigeratory circuit to prevent the final catastrophic destruction of the compressor, and to oblige the passenger to inspect the air conditioning system.
The method for controlling a compressor protection apparatus according to the present invention may be implemented in software and installed in the following appal al~ls.
Specifically, a co~p~ssor protection appa~al~ls having as inputs a signal from a temperature 10 sensor ~tt~c.h~d to the compressor, and a signal representing the engine rotational frequency from an engine control apparatus. The compressor protection apparatus includes two tandemly connected switches that control the activation or de-activation of the electromagnetic clutch. Functionally, one of the two switch is a temporary (or reversible) switch that can be re-closed to make contact by the software. The second of the two 15 switches is a breaker-type switch that can not be re-closed to make contact by the software.
The method of controlling a co"lpiessor protection apparatus according to the present invention provides an algorithm for controlling the opening or closing of the two switches based a compressor temperature signal and an engine rotational frequency signal.
The method of controlling the compressor protection apparatus includes a number 20 of features. The algorithm breaks contact of a breaker-type switch in the protection apparatus to prevent contin-led operation ofthe ~ige~lo~y circuit when the engine rotation speed is in a normal range and the con,plessor temperature is abnormally high at the same time. This feature prevents the catastrophic destruction of the compressor. Moreover, if the engine rotational frequency is m~int~ined in a high range for a certain time duration, the 25 algorithm breaks contact of a temporary switch in the protection apparatus and thus temporarily prevents continued operation of the compressor. In this situation, the refrigeratory circuit can be restarted again after some time. This feature, that is based on monitoring the time duration of high rotational frequency of the vehicular engine, prevents unnecessarily frequent on/off operation of the electromagnetic clutch.
The compressor protection apparatus according to the embodiments of the present invention can be embodied in various electronic or electric circuits that are part of current electronic technology.
DC01:192342.1 -4-Other objects, features, and advantages of this invention will be understood from the following detailed description of the p~erel,ed embodiment of this invention with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a s~h~",~ic circuit of a compressor protection apparatus according to the prior art.
Figure 2 is a sehçm~tic circuit of a col~,~ressor protection apparatus according to one embodiment of the present invention.
Figure 3 is flow chart of a method for controlling a compressor protection apparatus 10 according to one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In Fig. 2, a compressor 1 and a control unit 3 into which the compressor protection software according to the present invention, is installed, are schematically depicted. An engine rotational frequency signal from an engine control unit (not shown), and a compressor 15 temperature signal from complessor te"")e,~ re sensor 4, are input to control unit 3 . Power for activating the electromagnetic clutch 2 is supplied through two t~n-lçmly connected switches S1 and S2 that are provided within control unit 3. The switch S1 is opened or closed by control unit 3, while the switch S2 is a one-way switch, i.e., a breaker-type switch that can not be closed by control unit 3 once it has been opened. The switch S2 can be reset 20 (i.e., closed) m~n~l~lly during an inspection ofthe air conditioning system in a garage. The co"~plessor protection software controls the opening and closing of the two switches S 1, S2, based on information about the engine rotational frequency and compressor temperature.
Now, the method for controlling the two switches S 1, S2, i.e., the control software, will be explained with ~r~lence to Fig. 3. In the following explanation, the point of reference 25 on the flow chart is referred to as a cursor for convenience.
First, in box 11, h~""ation about the engine rotational frequency, r, and the co",p,essor temperature, t, are taken into control unit 3. Then, the cursor proceeds to box 12, in which the engine rotational frequency, r, is compared with a constant R1, where R1 is determined by experiment to be a boundary value between a high engine rotational 30 frequencv range and a normal engine rotational frequency range. Inequality r> R1 means a state in which the engine rotational frequency is higher than normal range. If the inequality r>R1 is satisfied, the cursor moves to box 13. In box 13 a determination is made as to DC01:1923421 -5-whether the r>Rl state has lasted for a certain time T1. The time constant Tl is determined experim~nt~lly to be an appropriate value. If the answer to this question is No, the cursor retums to box 11, and the same operations are repeated. This sequence comprised of boxes 11-12-13-11 conitit-1tes a closed loop Ll indicated in Fig. 3. During loop L1, 5 electrom~netic clutch 2 remains activated.
If, in box 13, the answer is Yes, that is, the r~R1 state has lasted for a certain time T1, the cursor will move to box 14, in which the switch S1 is opened to de-activate electrom~netic clutch 2. Subsequently the cursor moves to box 15, in which the engine rotational frequency, r, is taken in the control unit 3 again. Then the cursor moves to boxes 16,17. In box 16, it is determined whether r<R2 holds, where R2 is a constant chosen to be smaller than the con~ l R1 given previously. In box 17, it is determined whether the r<R2 state has lasted for a certain time T2. The time constant T2 is determined experimentally to be an appl~)p,iate value. As can be seen from Fig. 3, the No branch from box 16 returns back to itself, and the No branch from the box 17 returns back to the box 15. Thus, during the loop conitituted by boxes 15-16-17-15, control unit 3 waits until the r<R2 state has continued for a time T2. If the r<R2 state has continued for a time T2, then the cursor moves to box 18, in which the switch S 1 is closed to activate the electromagnetic clutch 2 again. Then the cursor retums to box 11. This control sequence comprised of boxes 11-12-13-14-15-16-17-18-11 constitutes a large closed loop L2 indicated in Fig. 3. During one cycle of loop L2, the electrom~gnPtic clutch 2 is temporarily opened and closed again.
Retuming now to box 11, in which il~o~ lion about the engine rotational frequency, r, and the conlpl essor temperature, t, are taken into the control unit 3, the renn~inder of the control functionality is explained. From box 11, the cursor moves to the box 12 as before.
This time, consider the case in which the answer to the question whether r>R1 or not, is No.
That is, it is determined in box 12 that the engine rotational frequency is in a normal range.
Then the cursor moves to box 19, in which the compressor temperature, t, is compared with a certain constant Tc. If the answer to the question whether t>Tc or not, is No, the cursor retums back to the box 11. If it is determined that t>Tc does not hold, then the compressor t~ lalllre, t, is lower than the critical temperature Tc, i e., there is no abnormality within the colllplessor. As indicated in Fig. 3, the sequence comprised of boxes 11-12-19-11 constitutes a third closed loop L3. During loop L3, electromagnetic clutch 2 remains activated.
DC01:192342.1 -6-For the final case, control is returned to box 1 1 again. In box 1 1, information of the engine rotational frequency, r, and the compressor temperature, t, are taken into control unit 3. The cursor then moves to box 12 as before. Now consider the case in which the answer to the question whether or not r>R1 is No, in order to explain the final control path. If the 5 answer to the question in box 12 is No, then the cursor moves to box 19, in which the compressor temperature, t, is compared with the critical temperature Tc. If there exists a leakage in the refrigeratory circuit, and the leakage has progressed to some degree, the compressor temperature increases due to the shortage of lubricating oil in the compressor even though the compressor is driven at moderate engine rotational frequency. In such a 10 case, compressor temperature rises and the answer to the question whether or not t>Tc is Yes. The cursor proceeds to the boxes 20 and 21, and finally reaches the END of the control flow. In box 20, breaker switch S2 is opened to de-activate electromagnetic clutch 2, and disable continued operation of the air conditioning system. Box 21 represents a procedure of inspection and repair for the system. The breaker switch S2 can only be closed m~n~1~11y 15 during such an inspection and repair procedure. Unless the procedure of inspection and repair is made, the air conditioning system can not be operated again. Thus, the method of controlling a compressor protection apparatus end with a one-way path, P, comprised of boxes 11-12-19-20-21, as indicated in Fig. 3.
To put together all the above explanations, the trajectory of the cursor will be as 20 follows. If there is no leakage in the l~iigel~tory circuit and the engine rotational frequency is in the normal range, the cursor circulates on the closed loop L3 and the electrom~gnetic clutch remains activated. When the engine rotational frequency increases to high range occasionally, but does not l"~ such state for a duration T1, the cursor circulates on the closed loop L1 and the electrom~gnetic clutch remains activated also. If the state of high 25 engine rotational frequency has lasted longer than the time T 1, the cursor enters the closed loop L2. During the closed loop L2, the switch S 1 is opened temporarily to de-activate the electromagnetic clutch t~lllpol~ily. That is, the compressor is disconnected from the engine and protected from possible damage. When the cursor traces the closed loop L2, the opening and closing of the switch S1 is controlled by comparing the time duration of high engine 30 rotational frequency with a time constant T1 and by colllpaling the time duration of normal engine rotational frequency state with a time constant T2. The switch S1 only opens or closes when the time duration of the high engine rotational frequency exceeds a time constant DC01:192342.1 -7-T1 or when the time duration of normal engine rotational frequency exceeds a time constant T2. Due to the introduction of con~ times T 1, T2, the opening and closing of the switch S1, i e., the on/off of the electrom~gnetic clutch is fairly stable when compared with conventional systems. That is, by circ~ tin~ around either one ofthe closed loops L1, L2 or L3, the control unit 3 prevents unnecessarily frequent turning on/off of the electrom~gnetic clutch.
During normal operation of the air conditioning system, the cursor is circ~ tingaround either one ofthe three closed loops L3, LI, or L2, for example, L3-L3-L1-L2-LI-as described above. But, if there is a leakage in the refrigeratory circuit that has progressed to some degree, the cursor goes into the one-way path P that branches at the box 19. And, then, in the box 20, breaker switch S2 is opened to de-activate the electromagnetic clutch semi-perm~nently. This path P is one-way, and, thus, the breaker switch S2 does not close automatically. The breaker switch S2 can only be closed m~nll~lly, for example, during an inspection in a garage. Namely, by providing the one-way path P in the control flow, serious damage ofthe colllplessor, which eventually occurs in conventional systems when there is leakage in the refrigeratory circuit, is prevented.
Further, with reference to Fig. 2 again, although both of the two switches are inserted tandemly in the electric power line to the electrom~ netic clutch 2, the breaker switch S2 may be anywhere within the circuit of the control unit 3 . For example, a single switch S 1, that is given both of the functions of temporary opening and irreversible opening, may be inserted in the electric power line to the electromagnetic clutch 2. In this case, breaker switch S2 is replaced with a reset switch of control unit 3. Therefore, when an irreversible opening of switch S1 has occurred (due to a leakage of refrigerant gas and lubricating oil), it only may be closed by the reset switch.
Although the present invention has been described in detail in connection with pl~r~lled embodiment, the invention is not limited thereto. It will be understood by those of ordinary skill in the art that variations and modifications may be made within the scope of this invention, as defined by the following claims.
DC01:192342.1 -8-.. .. .. . . .
Claims (7)
1. A compressor protection apparatus for a vehicular air conditioning system comprising two switches tandemly connected and inserted in a power line for activating an electromagnetic clutch of the compressor, said switches operative in response to an engine rotational frequency signal from an engine control unit and a compressor temperature signal from a temperature sensor attached to said compressor.
2. The compressor protection apparatus according to claim 1, wherein a first switch of said two tandemly connected switches is reversible in that it is opened or closed by ordinary operation of the compressor protection apparatus, and a second switch of said two tandemly connected switches is irreversible in that it can only be opened but not closed by ordinary operation of the compressor protection apparatus.
3. A compressor protection apparatus according to claim 2, wherein said first switch opens when engine rotational frequency is higher than a first frequency value for a certain time period, and said second switch opens when engine rotational frequency is lower than said first frequency value and compressor temperature is greater than a first temperature value.
4. A control method for a compressor protection apparatus for a vehicular airconditioning system comprising two switches tandemly connected and inserted in a power line for activating an electromagnetic clutch of a compressor, said switches operative in response to an engine rotational frequency signal from an engine control unit and a compressor temperature signal from a temperature sensor attached to said compressor, said control method comprising:
a first loop in which engine rotational frequency and compressor temperature areverified to be lower than a first and a second value respectively, and said two switches remain closed, a second loop in which engine rotational frequency is verified to be greater than said first value for less than a first time period, and said two switches remain closed, a third loop in which engine rotational frequency is verified to be greater than said first value for at least the first time period, and one of said two switches is opened to temporarily de-activate the electromagnetic clutch, and a one-way path in which engine rotational frequency is verified to be lower than said first value, compressor temperature is verified to be greater than said second value, and a second one of said two switches is irreversibly opened to de-activate the electromagnetic clutch semi-permanently.
a first loop in which engine rotational frequency and compressor temperature areverified to be lower than a first and a second value respectively, and said two switches remain closed, a second loop in which engine rotational frequency is verified to be greater than said first value for less than a first time period, and said two switches remain closed, a third loop in which engine rotational frequency is verified to be greater than said first value for at least the first time period, and one of said two switches is opened to temporarily de-activate the electromagnetic clutch, and a one-way path in which engine rotational frequency is verified to be lower than said first value, compressor temperature is verified to be greater than said second value, and a second one of said two switches is irreversibly opened to de-activate the electromagnetic clutch semi-permanently.
5. A compressor protection apparatus for a vehicular air conditioning system comprising a switch inserted in a power line for activating an electromagnetic clutch of a compressor, said switch operative in response to an engine rotational frequency signal from an engine control unit and a compressor temperature signal from a temperature sensor attached to said compressor, and a reset switch, said reset switch capable of being reset only manually.
6. The compressor protection apparatus according to claim 5, wherein said switchfunctions in a reversible mode in that it is opened or closed by ordinary operation of the compressor protection apparatus and an irreversible mode in that it can only be opened but not closed again when engine rotational frequency is lower than a first constant and compressor temperature is greater than a second constant, wherein in said irreversible mode, the switch is resettable to closed only by said reset switch.
7. A control method for a compressor protection apparatus for a vehicular air conditioning system comprising a switch inserted in a power line for activating an electromagnetic clutch of a compressor, said switch operative in response to an engine rotational frequency signal from an engine control unit and a compressor temperature signal from a temperature sensor attached to said compressor, and a reset switch, said reset switch capable of being reset only manually, said control method comprising:
a first loop in which engine rotational frequency and compressor temperature areverified to be lower than a first value and a second value respectively, and said first switch remains closed, a second loop in which engine rotational frequency is verified to be greater than said first value for less than a first time period, and said first switch remains closed, a third loop in which engine rotational frequency is verified to be greater than said first value for at least the first time period, and said first switch is opened to de-activate the electromagnetic clutch temporarily, and a one-way path in which engine rotational frequency is verified to be lower than said first value and compressor temperature is verified to be greater than said second value, and said first switch is opened irreversibly to de-activate the electromagnetic clutch.
a first loop in which engine rotational frequency and compressor temperature areverified to be lower than a first value and a second value respectively, and said first switch remains closed, a second loop in which engine rotational frequency is verified to be greater than said first value for less than a first time period, and said first switch remains closed, a third loop in which engine rotational frequency is verified to be greater than said first value for at least the first time period, and said first switch is opened to de-activate the electromagnetic clutch temporarily, and a one-way path in which engine rotational frequency is verified to be lower than said first value and compressor temperature is verified to be greater than said second value, and said first switch is opened irreversibly to de-activate the electromagnetic clutch.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JPP09-255,134 | 1997-09-19 | ||
| JP25513497A JPH1194376A (en) | 1997-09-19 | 1997-09-19 | Compressor-protecting device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2247660A1 true CA2247660A1 (en) | 1999-03-19 |
Family
ID=17274564
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2247660 Abandoned CA2247660A1 (en) | 1997-09-19 | 1998-09-16 | Protection apparatus for compressor and controlling method of the same |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPH1194376A (en) |
| CA (1) | CA2247660A1 (en) |
| ID (1) | ID21081A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106152428A (en) * | 2016-09-29 | 2016-11-23 | 广东美的制冷设备有限公司 | Secondary refrigerant leakage protection control method, controller and air-conditioning |
| CN114704885A (en) * | 2022-03-11 | 2022-07-05 | 宁波德业日用电器科技有限公司 | Dehumidifier with refrigerant leakage detection function and detection method thereof |
-
1997
- 1997-09-19 JP JP25513497A patent/JPH1194376A/en not_active Withdrawn
-
1998
- 1998-09-14 ID IDP981236A patent/ID21081A/en unknown
- 1998-09-16 CA CA 2247660 patent/CA2247660A1/en not_active Abandoned
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106152428A (en) * | 2016-09-29 | 2016-11-23 | 广东美的制冷设备有限公司 | Secondary refrigerant leakage protection control method, controller and air-conditioning |
| CN106152428B (en) * | 2016-09-29 | 2019-04-19 | 广东美的制冷设备有限公司 | Secondary refrigerant leakage protects control method, controller and air-conditioning |
| CN114704885A (en) * | 2022-03-11 | 2022-07-05 | 宁波德业日用电器科技有限公司 | Dehumidifier with refrigerant leakage detection function and detection method thereof |
| CN114704885B (en) * | 2022-03-11 | 2024-02-13 | 宁波德业日用电器科技有限公司 | Dehumidifier with refrigerant leakage detection function and detection method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| ID21081A (en) | 1999-04-15 |
| JPH1194376A (en) | 1999-04-09 |
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| Date | Code | Title | Description |
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| EEER | Examination request | ||
| FZDE | Dead |