42results about How to "Guaranteed normal oil return" patented technology

The invention relates to the technical field of air conditioners, in particular to a control method and system for an air conditioner. The problem that the rapid cooling / heating effect is poor due tothe long frequency rising time in a starting and frequency rising control method of an existing air conditioner is solved. The control method comprises the steps that a compressor of the air conditioner is started, and grading and continuous frequency rising is conducted on the compressor according to a plurality of set speeds. By means of the control method, through grading and continuous frequency rising according to the multiple set speeds after the compressor is started, it can be ensured that normal oil return is conducted on the compressor while the frequency rising time of the compressor is sharply shortened, the purpose of rapid cooling / heating is achieved, the comfortableness of the air conditioner is improved, and the user experience is improved.

The invention relates to the technical field of air conditioners, in particular to a control method and system for an air conditioner under the low-temperature and high-humidity heating condition. Thecontrol method and system aim to solve the problems of the poor quick heating effect, the poor lubrication effect and easy frosting of an outdoor unit in the starting frequency-increasing control method of an existing air conditioner. The control method comprises the following steps that the environment temperature and the environmental humidity are obtained; when the environment temperature is smaller than the set temperature and the environment humidity is larger than the set humidity, a compressor is preheated; after preheating is finished, an outdoor fan is started, the speed of the outdoor fan is increased to a first target rotating speed; and in the process that the outdoor fan reaches the first target rotating speed, the compressor of the air conditioner is started; and the compressor is subjected to staged continuous frequency increasing according the multiple set speeds. Through the set mode, while normal oil return of the compressor is ensured, the frequency increasing timeof the compressor can be greatly shortened, the purposes of rapid heating, lubricating improving and frosting delaying are achieved, the comfort of the air conditioner is improved, and the user experience is improved.

The invention relates to the technical field of air conditioners, in particular to a control method and system for an air conditioner under a refrigerating mode in order to solve the problem that in an existing air conditioner turning-on frequency-increasing control method, the frequency increasing time is long, and thus the rapid refrigerating effect is poor. The control method comprises the steps that an external draught fan is started and speeded up till a first target rotating speed is achieved; the opening degree of an expansion valve is adjusted to be a first target opening degree; whenthe external draught fan and / or the expansion valve reach / reaches the preset conditions, a compressor is started; and the compressor is subjected to staged continuous frequency increasing according tomultiple set speeds. Through the arrangement mode, the frequency increasing time of the compressor can be greatly shortened while normal oil returning of the compressor is ensured, the purpose of rapid refrigerating is achieved accordingly, the comfort of the air conditioner is improved, and the user experience is improved.

The invention relates to the technical field of air conditioners, in particular to a control method and system for an air conditioner under a low-temperature low-humidity heating working condition inorder to solve the problems that as for an existing air conditioner turning-on frequency-increasing control method, the rapid heating effect is poor, and the lubricating effect is poor. The control method comprises the steps that the environment temperature and humidity are obtained; when the environment temperature is smaller than the set temperature and the environment humidity is not larger than the set humidity, a compressor is preheated; after preheating is finished, an external draught fan is started and speeded up till a first target rotating speed is achieved; while, before or after the external draught fan begins to be speeded up, the compressor of the air conditioner is started; and the compressor is subjected to staged continuous frequency increasing according to the multiple set speeds. Through the control method, the frequency-increasing time of the compressor can be greatly shortened while normal oil return of the compressor is ensured, the rapid heating and lubricating improving purposes are achieved, the comfort of the air conditioner is improved, and the user experience is improved.

The invention relates to the technical field of air conditioners, in particular to an air conditioner control method and system under the low-temperature heating work condition, and aims at solving the problems that an existing air conditioner is poor in rapid heating effect and lubricating effect. To achieve the purpose, the control method comprises the steps that the environment temperature is obtained; when the environment temperature is smaller than the set temperature, a compressor is preheated; after preheating is ended, an outer draught fan is started, and the speed is increased to thefirst target rotation speed; when the outer draught fan starts to accelerate or before the outer draught fan starts to accelerate or after the outer draught fan starts to accelerate, the aperture of an expansion valve is adjusted to the first target aperture; when the outer draught fan and / or the expansion valve reach / reaches the set conditions, the compressor is started; and the frequency of thecompressor is continuously increased in a staging manner according to multiple set speeds. According to the method, the compressor frequency increasing time can be greatly shortened, the purposes of rapid heating and improving lubrication are achieved, the comfort of the air conditioner is improved, and the user experience is improved.

The invention relates to the technical field of air conditioners, in particular to a control method and system of an air conditioner under the low-humidity heating condition. The control method and system of the air conditioner under the low-humidity heating condition aim at solving the problem that the frequency increase time of an existing air conditioner startup frequency increase control method is long and consequently the quick heating effect is poor. The control method comprises the steps that the environment humidity is obtained; when the environment humidity is no greater than the sethumidity, an outer fan is started, and the speed of the outer fan is increased to the first target rotation speed; a compressor of the air conditioner is started while or before or after the speed ofthe outer fan starts to be increased; and the frequency of the compressor is continuously increased stage by stage according to multiple set speeds. By means of the control method, the frequency increase time of the compressor can be greatly shortened while normal oil return of the compressor is ensured, so that the purpose of quick heating is achieved, the comfort of the air conditioner is improved, and user experience is improved.

The invention discloses an oil-returning control method and an oil-returning device for a compressor as well as an air conditioner. The air conditioner comprises the compressor, an oil separator, an oil-returning pipeline and a controller, wherein an inlet of the oil separator is connected with an exhaust port of the compressor and receives gas-oil mixtures exhausted by the compressor for separation; the oil-returning pipeline is connected between an oil outlet of the oil separator and the compressor and returns oil separated by the oil separator to the compressor; a plurality of throttling pipelines are arranged in the oil-returning pipeline and in parallel connection; and the controller is used for regulating the working frequencies of the compressor and carrying on gate control on the throttling pipelines according to the working frequencies of the compressor. According to the oil-returning control method and the oil-returning device for the compressor as well as the air conditioner, a plurality of throttling pipelines are arranged in parallel in the oil-returning pipeline of the compressor, and gate control on each oil-returning pipeline is carried on according to different working frequencies of the compressor, so that the compressor can be guaranteed to return oil normally in various working conditions, and the oil-returning amount is guaranteed.

The invention relates to the technical field of air conditioners, in particular to a control method and system of an air conditioner under the low-humidity heating condition. The control method and system of the air conditioner under the low-humidity heating condition aim at solving the problem that the frequency increase time of an existing air conditioner startup frequency increase control method is long and consequently the quick heating effect is poor and the lubrication effect is poor. The control method comprises the steps that the environment humidity is obtained; when the environment humidity is smaller than the set humidity, a compressor is preheated; after preheating of the compressor is completed, an outer fan is started and the speed of the outer fan is increased to the first target rotation speed; the compressor of the air conditioner is started while the speed of the outer fan reaches the first target rotation speed; and the frequency of the compressor is continuously increased stage by stage according to multiple set speeds. In this way, the frequency increase time of the compressor can be greatly shortened while normal oil return of the compressor is ensured, so that the purposes of quick heating and lubrication improvement are achieved, the comfort of the air conditioner is improved, and user experience is improved.

The invention provides a control method for uniformly distributing a refrigerant during refrigeration of a modular multi-split air conditioner. The control method comprises the following steps of a) calculating the total capacity requirement N of an indoor unit module for m outdoor unit modules connected in parallel under the refrigeration operation state; b) initially distributing the capacity requirement of each outdoor unit module; c) detecting the bottom temperature Tbi of a compressor of the ith outdoor unit module by using a first temperature sensor; d) detecting the air return temperature Tri of the compressor of the ith outdoor unit module by using a second temperature sensor; e) calculating the air return superheat SHi of the ith outdoor unit module according to a formula that Shi=Tbi-Tri; f) adjusting the capacity requirement Ni of the ith outdoor unit module according to the air return superheat Shi of the ith outdoor unit module, making the air return superheat Shi and the adjusted capacity requirement NI' meet the following function: I=1,2,3,ellipsis,m, wherein NI'=[NI']=min{n belongs to Z and NI' is less than or equal to n}, and repeating steps c, d, e and f every ten minutes. The invention also provides a modular multi-split air conditioner for uniformly distributing a refrigerant during refrigeration. By the control method, the refrigerant in outdoor unit modules is distributed uniformly.

The invention relates to the technical field of air conditioners, in particular to a method and system for controlling an air conditioner under the low-temperature and low-humidity heating working condition. The method and system aim to solve the problems that as for an existing air conditioner, the quick heating effect is poor, and the lubrication effect is poor. The control method comprises thesteps that the environment temperature and environment humidity are obtained; when the environment temperature is smaller than the setting temperature and the environment humidity is not larger than the setting humidity, a compressor is preheated; after preheating, an expansion valve is adjusted to the first target opening; in the expansion valve adjusting process, an external blower is started and accelerated to the first target rotating speed; and the compressor is started while, before or after the external blower is accelerated, and continuous frequency increasing is conducted by stages according to a plurality of set speeds. Through the method, the frequency increasing time of the compressor can be greatly shortened, the purposes of rapid heating and lubrication improving are achieved, the comfort of the air conditioner is improved, and the user experience is improved.

The invention discloses a liquid impact preventing system and method. The liquid impact preventing system comprises a bypass pipeline, an adjustable switch and an electronic expansion valve, wherein the bypass pipeline is connected with an exhaust gas pipeline and a suction gas pipeline of a compressor and is provided with the adjustable switch and the electronic expansion valve; the bypass pipeline is used for extracting exhaust gas of the compressor so that the exhaust gas can sequentially pass through the adjustable switch and the electronic expansion valve to be mixed with suction gas of the compressor, the superheat degree of the suction gas is controlled to meet a preset condition, and liquid impact is prevented; the adjustable switch is used for adjusting the suction volume of the exhaust gas in the bypass pipeline; and the electronic expansion valve is used for carrying out cooling and pressure reducing treatment on the exhaust gas. In this way, the situation that the suction gas of the compressor contains liquid can be avoided, it does not need to arrange a gas-liquid separator, return oil can directly flow into the compressor, and therefore the normal oil returning of thesystem is guaranteed while the liquid impact phenomenon is avoided. The utilization efficiency of lubricating oil is improved, the charge volume of lubricating oil is reduced, and energy sources aresaved.

The invention relates to the technical field of air conditioners, in particular to an air conditioner control method and system under a low-temperature and high-humidity heating working condition. Theproblems that in an existing air conditioner starting-up and frequency-boosting control method, the rapid heating effect is poor, and the lubricating effect is poor are solved. The air conditioner control method comprises the steps that the environment temperature and the environment humidity are obtained; when the environment temperature is lower than a set temperature and the environment humidity is higher than set humidity, preheating is conducted on a compressor; after preheating is completed, the opening degree of an expansion valve is adjusted to be a first target opening degree; the compressor of an air conditioner is started in the adjusting process; and staged continuous frequency-boosting is conducted on the compressor according to a plurality of set speeds. According to the airconditioner control method and system under the low-temperature and high-humidity heating working condition, staged continuous frequency-boosting is conducted on the compressor at different frequency-boosting speeds after the compressor is started, the frequency-boosting time of the compressor can be greatly shortened while normal oil returning of the compressor is ensured, the purposes of rapidheating and lubrication improving are achieved, the comfort of the air conditioner is promoted, and the user experience is improved.

The invention provides a control method of a condensation fan of an air conditioner unit. The air conditioner unit comprises a compressor, an evaporator, a condenser and the condensation fan which areconnected through pipelines; a frequency converter is arranged on the condenser; a temperature sensor is arranged on the condenser; a master controller in signal connection with the condenser and thetemperature sensor receives a real-time temperature value of the temperature sensor, and thus selects a corresponding running frequency of the condensation fan; and the frequency converter adjusts and controls the running frequency of the condensation fan in real time. By means of the control method of the condensation fan of the air conditioner unit, continuous high-frequency running of the condensation fan can be avoided, the noise of the air conditioner unit is lowered, and the service life of the condensation fan is prolonged.

The invention relates to the technical field of air conditioners, in particular to a control method and system for air conditioner under a high-humidity heating working condition. In order to solve the problems that a start-up frequency boosting control method for an existing air conditioner is poor in quick heating effect as a result of long frequency boosting time and an outdoor unit is liable to frost when environmental humidity is relatively great, the control method comprises the following steps: obtaining ambient humidity; starting up an outer fan when the ambient humidity is greater than set humidity; increasing speed to first target rotation speed; regulating opening degree of an expansion valve to first target opening degree while or before or after the outer fan starts to increase speed; starting a compressor when the outer fan and / or the expansion valve reaches a set condition; and enabling the compressor to continuously boost frequency in stages according to multiple set speeds. In this way, frequency boosting time of the compressor can be greatly shortened while the compressor can be guaranteed to normally return oil, so that the purposes of quickly heating and delaying frosting are achieved, and therefore, the comfort of the air conditioner is improved, and the user experience is improved.

The invention relates to the technical field of air conditioners, in particular to a method and a system for controlling an air conditioner in a refrigeration mode. The method and the system aims to solve the problem that in an existing method for controlling start-up and frequency rising of an air conditioner, the fast refrigerating effect is poor because the frequency rising time is long. The control method comprises the following steps: the opening degree of an expansion valve is adjusted to a first target opening degree; in the process of adjusting the opening degree of the expansion valveto the first target opening degree, a compressor of the air conditioner is started; the compressor is enabled to continuously raise frequency in stages according to a plurality of set speeds. According to the method and the system, the compressor is enabled to continuously raise frequency at different frequency rising speeds in stages after being started, the frequency rising time of the compressor can be greatly shortened while the normal oil return of the compressor is guaranteed so that the purpose of rapid refrigeration can be achieved, the comfort of the air conditioner can be improved,and the user experience can be improved.

The invention relates to the technical field of air conditioners, in particular to an air conditioner control method and system under the low-temperature and high-humidity heating work condition and aims at solving the problems that an existing air conditioner is poor in rapid heating effect and poor in lubricating effect, and an outdoor unit is not prone to frosting. To achieve the purpose, the control method comprises the steps that the environment temperature and the environment humidity are obtained; when the environment temperature is smaller than the set temperature and the environment humidity is larger than the set humidity, a compressor is preheated; after preheating is finished, an outer draught fan is started, and the speed is increased to the first target rotation speed; when or before or after the speed of the outer draught fan starts to be increased, the aperture of an expansion valve is adjusted to the first target aperture; when the outer draught fan and / or the expansion valve reach / reaches the set conditions, the compressor is started; and staging continuous frequency increasing of the compressor is conducted according to multiple set speeds. According to the abovemethod, the compressor frequency increasing time can be greatly shortened, the purposes of rapid heating, improving lubricating and delaying frosting are achieved, the comfort of the air conditioneris improved, and the user experience is improved.

The invention provides an air conditioner control method and device, an air conditioner and a storage medium and relates to the technical field of air conditioners. The control method comprises the steps of acquiring the current outdoor environmental temperature when receiving an instruction of the air conditioner operating in an oil return mode; determining the operating frequency of a compressorand the opening degree of an electronic expansion valve of an indoor unit according to the current outdoor environmental temperature; and correcting the operating frequency of the compressor according to the obtained high pressure. Compared with the prior art, the air conditioner control method has the advantages that reversing and oil return are carried out not through a four-way reversing valve, and the oil return purpose is achieved by correcting operating parameters of the compressor and the opening degree of the indoor electronic expansion valve; and the situation that the indoor temperature fluctuation is too large due to reversing and oil return and the comfort degree of users is affected is avoided.

The invention relates to the technical field of air conditioners, in particular to a control method and system of an air conditioner under the high-humidity heating condition. The control method and system of the air conditioner under the high-humidity heating condition aim at solving the problems that as the frequency increase time of an existing air conditioner startup frequency increase controlmethod is long, the quick heating effect is poor, the environment humidity is high, and thus an outdoor unit is prone to frosting. The control method comprises the steps that the environment humidityis obtained; when the environment humidity is larger than the set humidity, an outer fan is started, and the speed of the outer fan is increased to the first target rotation speed; a compressor of the air conditioner is started while the outer fan reaches the first target rotation speed; and the frequency of the compressor is continuously increased stage by stage according to multiple set speeds.In this way, the frequency increase time of the compressor can be greatly shortened while normal oil return of the compressor is ensured, so that the purposes of quick heating and frosting delay areachieved, the comfort of the air conditioner is improved, and user experience is improved.

The invention relates to the technical field of a screw water chilling unit, particularly to a dual parallel compressor screw water chilling unit. An evaporator (3) is a falling film evaporator. A first overflow pipe (10) for redundant lubricating oil output is arranged on a first compressor (4) and a second overflow pipe (11) for redundant lubrication oil output is arranged on a second compressor (5). The first overflow pipe (10) communicates with a first exhaust pipe (8) and the second overflow pipe (11) communicates with a second exhaust pipe (9). A partition (12) for isolating the lubricating oil separated from the two compressors is arranged in a twice oil separator (1).The dual parallel compressor screw water chilling unit has the advantages of having a nice oil return effect, a simple structure, a reliable work, an energy conservation, an environment friendliness and a low cost.

The invention relates to the technical field of air conditioners, in particular to a control method and system for an air conditioner under the low-humidity heating condition, and aims to solve the problem of poor quick heating effect due to long frequency boosting time with a starting frequency boosting control method for existing air conditioners. The control method comprises the steps as follows: the environment humidity is acquired; when the environment humidity is not larger than the set humidity, an expansion valve is adjusted to the first target opening degree; an external fan is started during adjustment of the expansion valve and is accelerated to the first target rotating speed; and when the external fan is accelerated, before the external fan is accelerated or after the externalfan is accelerated, a compressor is started and is subjected to stage-by-stage continuous frequency boosting at multiple set speeds. With the control method, the frequency boosting time of the compressor can be substantially shortened while normal oil return of the compressor is guaranteed, then the quick heating purpose can be achieved, the comfort of the air conditioner can be improved, and theuser experience can be improved.

The invention relates to a control method of a condensate fan of an air conditioning unit. The air conditioning unit comprises a compressor, an evaporator, a condenser and the condensate fan which areconnected through pipelines. A frequency converter is arranged on the condenser, a main controller in signal connection with the condenser selects the corresponding operation frequency of the condensate fan according to passenger capacity data of a carriage, and a frequency converter regulates the operation frequency of the condensate fan in real time. The noise of the air conditioning unit is reduced, and the service life of the condensate fan is prolonged. A certain compression ratio of a refrigerating system is maintained, so that normal oil return of the compressor is guaranteed, and theservice life of the rail air conditioning unit compressor is prolonged. Frequent fluctuation of the frequency of the fan is effectively avoided, and fluctuation of the refrigerating system is reduced.

The invention relates to the technical field of air conditioners, in particular to a control method and system for an air conditioner under a refrigerating mode in order to solve the problem that in an existing air conditioner turning-on frequency-increasing control method, the frequency increasing time is long, and thus the rapid refrigerating effect is poor. The control method comprises the steps that an external draught fan is started and speeded up till a first target rotating speed is achieved; the opening degree of an expansion valve is adjusted to be a first target opening degree; whenthe external draught fan and / or the expansion valve reach / reaches the preset conditions, a compressor is started; and the compressor is subjected to staged continuous frequency increasing according tomultiple set speeds. Through the arrangement mode, the frequency increasing time of the compressor can be greatly shortened while normal oil returning of the compressor is ensured, the purpose of rapid refrigerating is achieved accordingly, the comfort of the air conditioner is improved, and the user experience is improved.

The invention relates to the technical field of air conditioners, in particular to a control method and system of an air conditioner under the low-humidity heating condition. The control method and system of the air conditioner under the low-humidity heating condition aim at solving the problem that the frequency increase time of an existing air conditioner startup frequency increase control method is long and consequently the quick heating effect is poor. The control method comprises the steps that the environment humidity is obtained; when the environment humidity is no greater than the sethumidity, an outer fan is started, and the speed of the outer fan is increased to the first target rotation speed; a compressor of the air conditioner is started while or before or after the speed ofthe outer fan starts to be increased; and the frequency of the compressor is continuously increased stage by stage according to multiple set speeds. By means of the control method, the frequency increase time of the compressor can be greatly shortened while normal oil return of the compressor is ensured, so that the purpose of quick heating is achieved, the comfort of the air conditioner is improved, and user experience is improved.

The invention discloses a compressor oil return control method, an oil return device and an air conditioner, including a compressor, an oil separator, an oil return pipeline and a controller; the inlet of the oil separator is connected to the exhaust port of the compressor, Receive and separate the oil-air mixture discharged from the compressor; the oil return pipeline is connected between the oil outlet of the oil separator and the compressor, and returns the oil separated by the oil separator to the compressor; The oil pipeline is provided with multiple throttling pipelines, and the multiple throttle pipelines are connected in parallel; the controller is used to adjust the operating frequency of the compressor, and according to the operating frequency of the compressor, the Multiple throttling pipelines are used for gating control. The present invention designs a plurality of throttling pipelines in parallel in the oil return pipeline of the compressor, and performs gating control on each throttle pipeline according to the different operating frequencies of the compressor, thereby ensuring that the compressor can operate under various operating conditions. The oil can be returned normally, ensuring the amount of oil returned.

The invention relates to the technical field of air conditioners, in particular to a method and a system for controlling an air conditioner in a refrigeration mode. The method and the system aims to solve the problem that in an existing method for controlling start-up and frequency rising of an air conditioner, the fast refrigerating effect is poor because the frequency rising time is long. The control method comprises the following steps: the opening degree of an expansion valve is adjusted to a first target opening degree; in the process of adjusting the opening degree of the expansion valveto the first target opening degree, a compressor of the air conditioner is started; the compressor is enabled to continuously raise frequency in stages according to a plurality of set speeds. According to the method and the system, the compressor is enabled to continuously raise frequency at different frequency rising speeds in stages after being started, the frequency rising time of the compressor can be greatly shortened while the normal oil return of the compressor is guaranteed so that the purpose of rapid refrigeration can be achieved, the comfort of the air conditioner can be improved,and the user experience can be improved.

The invention provides an air conditioning system, a controlling method and air conditioner. The air conditioning system comprises a compressor, a condenser and an evaporator, further comprise an oiltank, wherein the oil tank communicates with a gas suction port of the compressor through a balance pipe, the air conditioning system further comprises a primary injection device, the primary injection device comprises a first injector, the first high-pressure injection end of the first injector communicates with the condenser, the first low-pressure injection end communicates with the evaporator,and the first outlet end of the first injector communicates with the oil tank. According to the air conditioning system, the controlling method and the air conditioner, a scheme that oil is directlyinjected to the gas suction port of the compressor is abolished, and the oil is prevented from being directly injected to the gas suction port of the compressor to be taken away by a gas flow, so thatthe condition that the compressor is caused to lack the oil is avoided, normal oil return when the compressor sucks is guaranteed, a secondary injection pipeline is removed, a primary injection pipeline is directly connected with the oil tank, the combination of oil return injection and oil cooling assistance is adopted, the times of oil soaking of the balance pipe can be reduced, and the stressstrain of the long-segment pipeline can be reduced as well.

The invention relates to the technical field of air conditioning, in particular to an air conditioning control method and system under high-humidity heating conditions. The invention aims to solve the problems in the existing air conditioner start-up frequency increase control method that the rapid heating effect is poor due to the long frequency increase time, and the outdoor unit is easy to frost when the ambient humidity is high. For this purpose, the control method of the present invention includes: obtaining the ambient humidity; when the ambient humidity is greater than the set humidity, starting the external fan and raising the speed to the first target speed; Adjust the opening of the expansion valve to the first target opening; start the compressor when the external fan and the expansion valve reach the set conditions; make the compressor continuously increase in frequency in stages according to a plurality of frequency increasing speeds. The above setting method can greatly shorten the frequency increase time of the compressor while ensuring the normal oil return of the compressor, thereby achieving the purpose of rapid heating and delaying frosting, improving the comfort of the air conditioner and improving the user experience.

The invention relates to the technical field of air conditioners, in particular to an air conditioner control method and system under the low-temperature heating work condition, and aims at solving the problems that an existing air conditioner is poor in rapid heating effect and lubricating effect. To achieve the purpose, the control method comprises the steps that the environment temperature is obtained; when the environment temperature is smaller than the set temperature, a compressor is preheated; after preheating is ended, an outer draught fan is started, and the speed is increased to thefirst target rotation speed; when the outer draught fan starts to accelerate or before the outer draught fan starts to accelerate or after the outer draught fan starts to accelerate, the aperture of an expansion valve is adjusted to the first target aperture; when the outer draught fan and / or the expansion valve reach / reaches the set conditions, the compressor is started; and the frequency of thecompressor is continuously increased in a staging manner according to multiple set speeds. According to the method, the compressor frequency increasing time can be greatly shortened, the purposes of rapid heating and improving lubrication are achieved, the comfort of the air conditioner is improved, and the user experience is improved.