CN1580660A - Method for preventing indoor coiled-tube from over-low temp., and air-conditioner thereof - Google Patents
Method for preventing indoor coiled-tube from over-low temp., and air-conditioner thereof Download PDFInfo
- Publication number
- CN1580660A CN1580660A CNA031388817A CN03138881A CN1580660A CN 1580660 A CN1580660 A CN 1580660A CN A031388817 A CNA031388817 A CN A031388817A CN 03138881 A CN03138881 A CN 03138881A CN 1580660 A CN1580660 A CN 1580660A
- Authority
- CN
- China
- Prior art keywords
- temperature
- coil pipe
- indoor
- indoor coil
- critical
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- Y02B30/746—
Landscapes
- Air Conditioning Control Device (AREA)
Abstract
This is a method to prevent the indoor coil-pipe's temperature over lower, and its air conditioner. In the CPU of monotype set, install a temperature test block of the coil-pipe. Use the light-coupled silicon controlled method, according to the temperature of test value to control the alternating voltage of outdoor set, then to realize control the rotating speed of blower in the outdoor set. This invention provide a new electric-control method for fixed-frequency air conditioner, it can dynamic control the rotating speed of outdoor set's blower, to adjust the exchange efficient of this system in certain time interval.
Description
Technical field
The present invention relates to a kind of method and air conditioner that prevents that indoor coil pipe is low excessively, the technical scheme of coming dynamic adjustments outdoor fan rotating speed specifically according to indoor coil pipe.
Background technology
Along with The development in society and economy, air conditioner has obtained using more and more at present.Existing fixed frequency air conditioner machine is when refrigeration; too much for preventing that indoor coil pipe from crossing low frosting; main frame at large. the brain plate is provided with temperature sensor and relay; after the CPU on the computer plate detects temperature on the temperature sensor and meets or exceeds design temperature; compressor, outdoor fan autostop entered cold protection, thereby stopped the refrigerating operation of whole system.
Though above scheme can be controlled the frosting of indoor evaporator to a certain extent, having following shortcoming simultaneously needs to solve:
1, comparatively simply by relay control outdoor fan start-stop, system's heat exchange amount is fixed under the single prerequisite of rotation speed of fan.Can be owing to the indoor evaporator temperature be crossed the low high frequent start-stop that causes, not only increased air conditioner energy consumption, but also directly have influence on service life of compressor.
2, especially in communication base station or some commercial facility (as rink), owing to working equipment or use and to need under outdoor environment is in the situation of low temperature, to freeze, as above scheme can the frequent start-stop of outdoor fan occur not reaching under the situation of design temperature, can't in design time, reach operating temperature, also just can't guarantee to realize the job requirement under the special operation condition.
Thereby how to realize the refrigerating operation requirement of fixed frequency air conditioner machine under low temperature environment, be the technical task that institute of existing air conditioner manufacturer must solution.
Summary of the invention
Anti-low temperature method of indoor coil of the present invention and air conditioner thereof, the dynamo-electric control of a kind of new fixed frequency air conditioner control method is provided, dynamically regulate the rotating speed of outdoor fan according to indoor coil pipe, adjust the system's heat exchanger effectiveness in certain working time, thereby guaranteeing that indoor coil frosting prerequisite less or frost-free is issued to the requirement of setting cryogenic temperature.
The main hardware of existing air conditioner includes the refrigeration system that is made of compressor, condenser, evaporimeter and automatically controlled detection part and housing, the pipeline of indoor and outdoor machine.Indoor coil is provided with temperature sensor, by the unlatching or the disconnection in the dynamo-electric source of the direct control room of the relay on computer plate exogenous wind.
Correspondingly, on the host computer plate of existing air conditioner, a relay is set.In detection time, the CPU master chip is compared with the rated temperature that sets according to the signal of indoor coil pipe sensor input in unit.When indoor coil pipe T was higher than design temperature T1, relay coil conducting outdoor fan control circuit was kept the rated operational voltage of outdoor fan, and the rotating speed of outdoor fan is a certain value, the refrigeration system continuous firing; When indoor coil pipe T was equal to or less than design temperature T1, relay coil broke away from cut-out outdoor fan control circuit, and outdoor fan quits work, and whole refrigeration system is terminated, and the surface temperature of indoor coil is gone up.Have only when indoor coil pipe T is higher than design temperature T1, whether air conditioner just can reach critical value according to indoor environment temperature is selected to start refrigeration system.
It more than is the preference pattern of indoor coil pipe detection with the refrigeration system work of existing air conditioner.
The anti-low temperature method of indoor coil of the present invention is a kind of hommization fuzzy control method, has cancelled the mode by the direct control room of relay exogenous wind machine circuit, directly sets up a coil temperature in the CPU on single-chip microcomputer and detects control module.
In addition, in single-chip microcomputer, set up a smooth lotus root controllable silicon, judge output valve, the ac voltage in the dynamo-electric machine circuit of direct control room exogenous wind, thereby the actual speed that realization is just regulated blower fan by the voltage of blower motor according to temperature detection control module in the CPU.
Air conditioner computer plate is solidified with critical normal temperature T1 and T2 in CPU just as Installation and Debugging the time, wherein T1 is the critical-temperature that starts blower fan work, and T2 is the critical-temperature that stops blower fan work.
The T1 span is 5 ℃ to 10 ℃, and the T2 span is-5 ℃ to 5 ℃.The T1 value is higher than the T2 temperature value all the time.
The setting of T1 and T2 is decided on the running parameter of air conditioner refrigeration system itself, also can require and Iterim Change according to user's needs or operating ambient temperature.
When detecting indoor coil surface temperature T 〉=T1, the voltage of outdoor fan is kept rated value, and rotation speed of fan reaches rated maximum; When T2≤T＜T1, the voltage of outdoor fan is lower than rated value and reduces the reduction that realizes voltage with temperature, thereby rotation speed of fan is with the temperature reduction and reduce gradually; When T＜T2, the voltage of outdoor fan reaches specified minimum of a value, and rotation speed of fan is zero.
Light lotus root controllable silicon receives the signal instruction that CPU sends, and directly output AC voltage value in the blower motor circuit of being connected, and then blower motor is by this magnitude of voltage driving blower fan work.In the time of in being lower than the range of nominal tension, the big more then rotation speed of fan of voltage is big more; Otherwise then rotation speed of fan is more little; When voltage reached the setting minimum of a value, outdoor fan quit work.
When outdoor fan is worked, determine the heat exchanger effectiveness of whole refrigeration system, thereby have influence on indoor coil pipe.When coil temperature is low, can control the flow of refrigeration pipe inner refrigerant effectively by said method, make that coil temperature slowly descends in a long time, be unlikely to consume too much energy because of too much frosting.
As mentioned above, anti-low temperature method of indoor coil provided by the present invention and air conditioner thereof, can be not less than in environment temperature under-15 ℃ of situations, realize long-time indoor refrigerating operation, be compared to that prior art has the following advantages and beneficial effect guaranteeing that the indoor coil frosting is less.
1, can realize dynamically regulating the outdoor fan rotating speed, thereby realize a kind of refrigeration pipe hommization fuzzy control according to the critical-temperature that sets, effectively reduce the compressor on-off frequency, prolong the service life of compressor.
2, when indoor coil because work is former thereby when causing temperature low, delay the speed that its temperature reduces by the heat exchanger effectiveness that reduces refrigeration system, realized a kind ofly impelling the refrigeration pipe continuous firing and further reducing the pattern of environment temperature.Thereby be suitable at outdoor low temperature and the special place of indoor requirement refrigeration.
3, because indoor coil frosting speed is controlled, and can continue refrigerating operation, thereby the whole system energy loss is less, saves the air conditioner use cost effectively.
Description of drawings
Fig. 1 is an air conditioner electronic control module schematic diagram of the present invention.
Fig. 2 is that coil temperature detects the control module schematic flow sheet.
Fig. 3 is an air-conditioning unit room inner coil pipe structural representation of the present invention.
Fig. 4 is an air conditioner circuit diagram of the present invention.
As shown in Figure 1, the anti-low temperature method of coil pipe of the present invention and air-conditioning machine thereof are at the main frame electricity Be provided with CPU, data signal processor DSP, memory ROM/RAM etc. on the brain plate, on computer board Increase light lotus root controllable silicon is set. Call and judge the temperature value signal of coil pipe sensor input by CPU, With the ac voltage of control light lotus root controllable silicon output, regulate the rotating speed of outdoor fan.
As shown in Figure 2, the anti-low temperature method of coil pipe of the present invention and air-conditioning machine thereof, detected Indoor coil surface temperature T compares with critical-temperature T1, T2 respectively, thereby determines outdoor wind The voltage of machine, and finally determine the rotating speed height of blower fan.
On the indoor coil evaporimeter, be provided with temperature sensor 1 as shown in Figure 3, splash guard 2, cover Pipe 3, feed tube group 4, escape pipe group 5, instlated tubular 6.
Be circuit diagram of the present invention as shown in Figure 4, wherein the single-chip microcomputer model is TMP876PH46N.
The specific embodiment
With reference to Fig. 1-shown in Figure 4, coil pipe of the present invention is prevented low temperature method, is the relay on the existing air conditioner host computer plate of cancellation, and a kind of control method of dynamic adjustments is provided.
In the singlechip CPU of air conditioner, be solidified with a coil temperature and detect control module, at the computer plate just as when installing, be solidified with critical normal temperature T1 and T2 in CPU, wherein T1 is the critical-temperature that starts blower fan work, and T2 is the critical-temperature that stops blower fan work.
Wherein, the T1 value is 7 ℃, and the T2 value is 0 ℃.
On the computer plate, set up a smooth lotus root controlled silicon chip.
After the air conditioner energising work, call coil temperature by CPU and detect control module, and receive the coil surface temperature value T of temperature sensor input.
As shown in Figure 2, at first whether judge T 〉=T1.If T 〉=T1, higher not frosting of indoor coil pipe or refrigeration system refrigeration work not as yet is described.Then CPU exports to light lotus root controlled silicon chip with this judged result, and light lotus root controllable silicon is exported specified high-voltage value, and promptly 220 volts, by specified high speed rotating, rotating speed is a certain value to outdoor fan under 220 volts of voltages drive.
If T＜during T1, then continue whether judge T＜T2.If T＜T2 illustrates that then indoor coil has been lower than the critical-temperature of frosting, then can cause frosting too much if continue refrigeration.If continue refrigeration, then can cause and freeze or direct bursting by freezing pipeline equipment.At this moment, CPU directly exports to light lotus root controllable silicon command for stopping, and light lotus root controllable silicon is exported specified low voltage value, and outdoor fan stops operating, and rotating speed is zero.
Have only when T2≤T＜T1, call coil temperature by CPU and detect control module, this module compares (T1-T) and difference size (T-T2) respectively, when (T1-T)＞(T-T2), illustrate that coil temperature T more approaches T2, then the magnitude of voltage of light lotus root controllable silicon output is lower.Difference is big more, and magnitude of voltage is low more, and rotation speed of fan is more little; When (T1-T)＜(T-T2), illustrate that coil temperature T more approaches T1, then the magnitude of voltage of light lotus root controllable silicon output is higher.Difference is more little, and magnitude of voltage is high more, and rotation speed of fan is big more.
The air conditioner that prevents that indoor coil pipe is low excessively of the present invention comprises the refrigeration pipe that is made of compressor, condenser, evaporimeter and indoor and outdoor machine housing pipe fitting.And as shown in Figure 1, the main automatically controlled detection module that constitutes by computer plate, sensor.
On air conditioner computer plate, set up a smooth lotus root controlled silicon chip, and connect with the outdoor fan circuit.
In singlechip CPU, be solidified with a coil temperature and detect control module, and critical normal temperature T1 and T2, wherein T1 is the critical-temperature that starts blower fan work, T2 is the critical-temperature that stops blower fan work.T1 is higher than T2.
Light lotus root controllable silicon receives the signal instruction that CPU sends, and directly output AC voltage value in the blower motor circuit of being contacted, and then blower motor is by this magnitude of voltage driving blower fan work.
Coil temperature detects the control module operation method as mentioned above.
Claims (8)
1, a kind of method that prevents that indoor coil pipe is low excessively, it is characterized in that: curing is provided with a coil temperature and detects control module in the CPU on the air conditioner single-chip microcomputer, this module is transferred the temperature value T that judges the input of coil pipe sensor, controls the outdoor fan rotating speed by a smooth lotus root controllable silicon that is provided with on the single-chip microcomputer.
2, the method that prevents that indoor coil pipe is low excessively according to claim 1, it is characterized in that: in coil temperature detects control module, be solidified with critical normal temperature hole and T2, wherein T1 is the critical-temperature that starts blower fan work, and T2 is the critical-temperature that stops blower fan work.The T1 temperature value is higher than the T2 temperature value.
3, the method that prevents that indoor coil pipe is low excessively according to claim 2 is characterized in that: the T1 span is 5 ℃ to 10 ℃, and the T2 span is-5 ℃ to 5 ℃.
4, the method that prevents that indoor coil pipe is low excessively according to claim 3, it is characterized in that: when indoor coil pipe T 〉=T1, coil temperature detects control module control light lotus root controllable silicon and exports specified high-voltage value, and outdoor fan is by specified high rotational speed.
5, the method that prevents that indoor coil pipe is low excessively according to claim 3 is characterized in that: when indoor coil pipe T＜T2, coil temperature detects control module control light lotus root controllable silicon and exports specified low voltage value, and the outdoor fan rotating speed is zero.
6, the method that prevents that indoor coil pipe is low excessively according to claim 3 is characterized in that: when indoor coil pipe T2≤T＜T1, detect control module relatively (T1-T) and difference size (T-T2) by coil temperature; When difference was big more, then the magnitude of voltage of light lotus root controllable silicon output was lower, and rotation speed of fan is more little; When difference more hour, then the magnitude of voltage of light lotus root controllable silicon output is higher, rotation speed of fan is big more.
7, application rights requires 1 described application to prevent that indoor coil pipe from crossing the air conditioner of low method, comprise the refrigeration pipe that constitutes by compressor, condenser, evaporimeter and indoor and outdoor machine housing pipe fitting, and the automatically controlled detection module that mainly constitutes by computer plate, sensor, it is characterized in that: in singlechip CPU, be solidified with a coil temperature and detect control module, and critical normal temperature T1 and T2, wherein T1 is the critical-temperature that starts blower fan work, T2 is the critical-temperature that stops blower fan work, and the T1 temperature value is higher than the T2 temperature value.
8, air conditioner according to claim 7 is characterized in that: substitute relay with a smooth lotus root controllable silicon on the computer plate, and connect with the outdoor fan circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB031388817A CN1260531C (en) | 2003-08-06 | 2003-08-06 | Method for preventing indoor coiled-tube from over-low temp., and air-conditioner thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB031388817A CN1260531C (en) | 2003-08-06 | 2003-08-06 | Method for preventing indoor coiled-tube from over-low temp., and air-conditioner thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1580660A true CN1580660A (en) | 2005-02-16 |
| CN1260531C CN1260531C (en) | 2006-06-21 |
Family
ID=34579124
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB031388817A Expired - Lifetime CN1260531C (en) | 2003-08-06 | 2003-08-06 | Method for preventing indoor coiled-tube from over-low temp., and air-conditioner thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1260531C (en) |
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102519112A (en) * | 2011-11-30 | 2012-06-27 | 四川长虹电器股份有限公司 | Fan control method for modular water chilling unit |
| CN103292419A (en) * | 2013-05-30 | 2013-09-11 | 四川长虹电器股份有限公司 | Device and method for preventing refrigerants from gathering |
| CN103398444A (en) * | 2013-07-01 | 2013-11-20 | Tcl空调器(中山)有限公司 | Air conditioner low-temperature refrigeration method and device |
| CN103712308A (en) * | 2012-09-28 | 2014-04-09 | 美的集团股份有限公司 | Air conditioner capacity regulating and controlling method and system |
| CN103836766A (en) * | 2012-11-27 | 2014-06-04 | 美的集团股份有限公司 | Air conditioner indoor unit and automatic static pressure regulating method and device thereof |
| CN105276773A (en) * | 2015-11-30 | 2016-01-27 | 广东美的制冷设备有限公司 | Work control method and device of air conditioner |
| CN106123287A (en) * | 2016-06-30 | 2016-11-16 | 青岛海尔空调器有限总公司 | A kind of air-conditioner and control method thereof |
| CN106765939A (en) * | 2016-12-16 | 2017-05-31 | 江苏海创电气科技有限公司 | A kind of intelligence two dimension wind-heat control energy-saving control system |
| CN106839326A (en) * | 2017-02-28 | 2017-06-13 | 广东美的制冷设备有限公司 | Air conditioner fault reminding method, device and air-conditioner |
| CN107238183A (en) * | 2017-06-26 | 2017-10-10 | 广东美的暖通设备有限公司 | Outdoor fan control method, device and computer-readable recording medium |
| CN107917516A (en) * | 2017-10-31 | 2018-04-17 | 青岛海尔空调器有限总公司 | A kind of control method and device of outdoor fan of air-conditioner rotating speed |
| CN108168028A (en) * | 2018-01-04 | 2018-06-15 | 芜湖美智空调设备有限公司 | Method, mobile air conditioner and the storage medium of mobile air conditioner refrigeration defrosting |
| CN109945397A (en) * | 2019-03-29 | 2019-06-28 | 广东美的制冷设备有限公司 | Air conditioner and its dewing-proof method and device |
| CN110779176A (en) * | 2019-11-11 | 2020-02-11 | 广东美的制冷设备有限公司 | Electronic equipment, air conditioner and control method and control device of air conditioner |
| CN112033073A (en) * | 2020-07-23 | 2020-12-04 | 常州慧聪电动门配件科技有限公司 | Air curtain control belt fan protection control system special for refrigeration house |
-
2003
- 2003-08-06 CN CNB031388817A patent/CN1260531C/en not_active Expired - Lifetime
Cited By (21)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102519112A (en) * | 2011-11-30 | 2012-06-27 | 四川长虹电器股份有限公司 | Fan control method for modular water chilling unit |
| CN102519112B (en) * | 2011-11-30 | 2014-04-16 | 四川长虹电器股份有限公司 | Fan control method for modular water chilling unit |
| CN103712308A (en) * | 2012-09-28 | 2014-04-09 | 美的集团股份有限公司 | Air conditioner capacity regulating and controlling method and system |
| CN103712308B (en) * | 2012-09-28 | 2016-12-21 | 美的集团股份有限公司 | A kind of air-conditioner capacity regulating control method and system |
| CN103836766A (en) * | 2012-11-27 | 2014-06-04 | 美的集团股份有限公司 | Air conditioner indoor unit and automatic static pressure regulating method and device thereof |
| CN103292419B (en) * | 2013-05-30 | 2016-06-22 | 四川长虹电器股份有限公司 | A kind of apparatus and method preventing coolant from assembling |
| CN103292419A (en) * | 2013-05-30 | 2013-09-11 | 四川长虹电器股份有限公司 | Device and method for preventing refrigerants from gathering |
| CN103398444B (en) * | 2013-07-01 | 2016-12-28 | Tcl空调器(中山)有限公司 | Air conditioner low-temperature refrigeration method and device |
| CN103398444A (en) * | 2013-07-01 | 2013-11-20 | Tcl空调器(中山)有限公司 | Air conditioner low-temperature refrigeration method and device |
| CN105276773A (en) * | 2015-11-30 | 2016-01-27 | 广东美的制冷设备有限公司 | Work control method and device of air conditioner |
| CN106123287A (en) * | 2016-06-30 | 2016-11-16 | 青岛海尔空调器有限总公司 | A kind of air-conditioner and control method thereof |
| CN106765939A (en) * | 2016-12-16 | 2017-05-31 | 江苏海创电气科技有限公司 | A kind of intelligence two dimension wind-heat control energy-saving control system |
| CN106839326A (en) * | 2017-02-28 | 2017-06-13 | 广东美的制冷设备有限公司 | Air conditioner fault reminding method, device and air-conditioner |
| CN107238183A (en) * | 2017-06-26 | 2017-10-10 | 广东美的暖通设备有限公司 | Outdoor fan control method, device and computer-readable recording medium |
| CN107917516A (en) * | 2017-10-31 | 2018-04-17 | 青岛海尔空调器有限总公司 | A kind of control method and device of outdoor fan of air-conditioner rotating speed |
| CN107917516B (en) * | 2017-10-31 | 2020-11-03 | 青岛海尔空调器有限总公司 | Method and device for controlling rotating speed of outdoor fan of air conditioner |
| CN108168028A (en) * | 2018-01-04 | 2018-06-15 | 芜湖美智空调设备有限公司 | Method, mobile air conditioner and the storage medium of mobile air conditioner refrigeration defrosting |
| CN108168028B (en) * | 2018-01-04 | 2020-05-22 | 芜湖美智空调设备有限公司 | Method for refrigerating and defrosting of mobile air conditioner, mobile air conditioner and storage medium |
| CN109945397A (en) * | 2019-03-29 | 2019-06-28 | 广东美的制冷设备有限公司 | Air conditioner and its dewing-proof method and device |
| CN110779176A (en) * | 2019-11-11 | 2020-02-11 | 广东美的制冷设备有限公司 | Electronic equipment, air conditioner and control method and control device of air conditioner |
| CN112033073A (en) * | 2020-07-23 | 2020-12-04 | 常州慧聪电动门配件科技有限公司 | Air curtain control belt fan protection control system special for refrigeration house |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1260531C (en) | 2006-06-21 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN1260531C (en) | Method for preventing indoor coiled-tube from over-low temp., and air-conditioner thereof | |
| CN1292215C (en) | Refrigerating device | |
| CN106440241B (en) | A kind of method for controlling speed regulation of outdoor fan of air-conditioner | |
| CN1156658C (en) | Air conditioner | |
| CN109751911B (en) | Self-adaptive adjusting method for fan frequency of cooling tower and air conditioning system | |
| CN102466304A (en) | Air-conditioning system and control method of condensation fan thereof | |
| CN112660409B (en) | Enthalpy difference control method of airplane ground air conditioning system | |
| CN101714847A (en) | Method for controlling air conditioning outdoor motor | |
| CN107642879B (en) | Control method and device of air conditioning system and air conditioner | |
| CN1888646A (en) | Variable frequency air conditioner and controlling method thereof | |
| CN111306732B (en) | Control method of drainage water pump of water receiving disc of air conditioner and air conditioner | |
| CN104819541B (en) | Energy-saving control method, device and air conditioner | |
| CN1135336C (en) | Air conditioner | |
| KR960014815A (en) | Control unit of air conditioner | |
| CN208042400U (en) | A kind of full direct current solar air-conditioner system of low-voltage | |
| CN112797576B (en) | High-temperature refrigeration air conditioner control method | |
| CN107906682B (en) | Control method and device of air conditioning system and air conditioner | |
| CN111765597B (en) | Energy efficiency test control method of air conditioning system and air conditioning system | |
| CN114738955A (en) | Air conditioner and control method and control device thereof | |
| CN111120088B (en) | Vehicle control system, vehicle, and control method | |
| CN218526655U (en) | Precise air-conditioning energy-saving equipment for data center machine room | |
| CN115164635B (en) | Closed cooling tower fan control method and system | |
| CN115900007B (en) | Temperature-adjusting and dehumidifying method and device for rack-mounted air conditioner | |
| CN114893870B (en) | Predictive control method for natural cooling system operation mode | |
| KR0177691B1 (en) | Compresser operating control method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CX01 | Expiry of patent term |
Granted publication date: 20060621 |
|
| CX01 | Expiry of patent term |