132 results about "Gas engine" patented technology

The invention discloses a heating control method for an engine gas delivery pipeline of a marine gas generator set, which relates to the technical field of marine gas power systems, and comprises the following steps: collecting multi-dimensional environment state information of the gas delivery pipeline in real time, analyzing gas components and pressure fluctuation data, and calculating the temperature of the gas delivery pipeline; a theoretical dew point temperature and a potential paraffin precipitation temperature under real-time pressure are calculated by combining a fuel gas physical property database, a real-time heat exchange model is constructed by combining a pipeline outer wall temperature gradient and a cabin environment temperature, theoretical temperature attenuation curves of different positions of fuel gas in a pipeline are obtained, condensation and paraffin precipitation risk positions and degrees are predicted after comparison, and a real-time heat exchange model is established. And differential electric heat tracing control strategies of different sections of the pipeline are generated in combination with relative humidity data of the cabin. The method can adapt to the real-time physical property of gas and the heat exchange state of the pipeline section, and the heating control execution mode of the gas pipeline is optimized.

The present application relates to the technical field of engine, and discloses a combustion system, a gas engine and a combustion system design method, a second fuel injection hole sprays an oil jet to ignite a part of natural gas jets on the same side of the second fuel injection hole, and under the action of a vortex in a combustion chamber, with the second fuel injection hole continuously spraying the oil jet, a flame formed by the oil jet igniting the natural gas jets gradually becomes longer along the vortex direction, so that the oil jet sprayed by the second fuel injection hole ignites the natural gas jets on the side of the natural gas injector opposite to the fuel injector; the oil jet sprayed by the first fuel injection hole ignites the remaining natural gas jets, so that the oil jets sprayed by the fuel injector on both sides of a reference line can achieve the maximum ignition effect, all the natural gas jets are ignited by using the least oil jet, the ignition effect of igniting the natural gas by using the fuel is improved, the thermal efficiency is higher, and the emission is lower.

The application belongs to the technical field of lubricating oil, and specifically provides a gas engine lubricating oil and a preparation method thereof.The gas engine lubricating oil comprises the following raw materials: ester base oil, anti-wear agent, dispersant, pour point depressant and antifoaming agent, wherein the ester base oil is prepared by esterification reaction of polyhydric alcohol and fatty acid; the preparation method of the anti-wear agent comprises the following steps: first, reacting acrylic acid with vinyl imidazole to prepare a modifier; then, polymeric phenol is obtained by polymerization of phenol under the action of a catalyst; finally, the polymeric phenol, boric acid and vegetable oil are reacted, the modifier is added after a certain time of reaction, and the reaction is continued to obtain the anti-wear agent.The preparation method of the gas engine lubricating oil of the application is that the raw material components are uniformly mixed according to the formula, and the gas engine lubricating oil of the application has good wear resistance, oxidation resistance, high-temperature detergency and thermal stability.

The application discloses a kind of single-shaft combustion engine natural gas filter filter core cleaning device, it is related to filter core cleaning technical field, including support seat and top frame, first runner and cleaning assembly are rotatably installed on the support seat, drum is installed on first runner, support assembly is arranged below first runner, cleaning pipe is installed above the drum, spray hole is opened in cleaning pipe, drive assembly is installed on the top frame, first magnetic block is connected below drive assembly, copper pipe is arranged on the outside of first magnetic block, second magnetic block and support ring are respectively arranged on the upper and lower sides of copper pipe, third magnetic block is fixedly connected on the inner wall of support ring, third motor is installed on support ring, first docking block is connected on the output shaft of third motor.The application solves the problem that the existing filter core cleaning device cannot automatically activate the vibration structure to vibrate the filter core to improve the cleaning effect during cleaning, and cannot reduce the transmission of ineffective vibration energy during cleaning.

Disclosed herein is a work machine having a gas engine and a gas storage system having at least one gas storage tank. The controller is provided with a controller configured to determine a leakage condition within the gas storage system and / or the gas engine.

The utility model is suitable for internal combustion engine gas supply mechanism technical field provides a kind of multi-point injection air intake pipe of gas machine, comprising: main pipeline, its one side is equipped with air inlet, the other side of main pipeline is equipped with several air intake manifold, each air intake manifold is equipped with air jet nozzle, the flow direction of the gas in the inside of air jet nozzle and air intake manifold has certain angle, air intake manifold and main pipeline use integrated structure, by this, the utility model is guaranteed by setting integrated air intake structure, the reliability of air intake, while setting a kind of separate air jet structure, to ensure the separate control to engine, optimization control effect.

The invention discloses a load translation control method for a hybrid diesel locomotive considering a diesel engine and a gas engine. The method comprises the following steps: in a ground bench test, respectively simulating typical operation conditions of the diesel / gas engine, and determining respective safe power fluctuation intervals; in the running process of the hybrid diesel locomotive, the output power of the diesel / gas engine is dynamically corrected based on the power fluctuation threshold value of the running data; and scene-based multi-energy load translation control is carried out, the scene comprises the dynamic operation characteristics of acceleration and deceleration of the train, and the engine power of the hybrid diesel locomotive is adjusted according to the working mode of the power battery and the power fluctuation difference value, so that the load translation of the hybrid diesel locomotive is met based on the engine power. According to the method, multi-energy cooperative control considering load translation, scientific and controllable threshold value and working condition adaptation is achieved, the comprehensive traction force of the hybrid diesel locomotive is improved, and energy conservation and emission reduction are achieved.

This invention discloses an exhaust device suitable for pure hydrogen gas engines, relating to the technical field of exhaust treatment for pure hydrogen gas engines. It solves the problem that existing pure hydrogen gas engine exhaust treatment devices suffer from the inability of a single condensation dehydration technology to completely eliminate whitening, and the inability of a single whitening device to remove water. A multi-stage condensation structure is installed inside the flange pipe at the uppermost end of the exhaust pipeline. The multi-stage condensation structure and the inner wall of the flange pipe form a condensation chamber. A condensation channel is provided within the multi-stage condensation structure. A return water connector and a water inlet connector are provided on the flange pipe. The water inlet connector is connected to the lower water inlet of the condensation channel; the return water connector is connected to the upper water return port of the condensation channel. By setting up a multi-stage condensation dehydration device in the main exhaust channel, the exhaust humidity is reduced while achieving the whitening effect, thus enabling the exhaust device to simultaneously possess the characteristics of corrosion resistance, stable operation, and economic and environmental protection.

The utility model discloses a connecting buffer device for an industrial gas engine, which relates to the technical field of connecting buffer equipment for engines, and comprises a mounting box body, four groups of guide columns are fixedly connected to the inner side of the mounting box body, and an upper mounting sliding plate is arranged above the inner side of the mounting box body; by means of the linkage design of the first damping rod and the second damping rod, vertical vibration of the engine is converted into composite motion of axial compression and transverse stretching or compression, three-dimensional vibration energy dispersion is achieved, a rotation linkage mechanism of the double-side rotating seat effectively avoids single-direction impact overload, and the vibration energy dispersion efficiency is improved. The transmission of vibration to an engine and an external rack is remarkably reduced, a penetrating type forced air cooling system is formed through an air inlet fan and multiple sets of heat dissipation mounting through holes, heat dissipation is directly conducted on a high-heat area at the bottom of the engine, through hole matrix layout is matched with mounting hole positions of engines of different sizes, the fixing function is achieved, meanwhile, the universality of an airflow channel is considered, and heat dissipation efficiency is improved. And the heat dissipation efficiency is improved.

This utility model discloses a leak-proof gas engine valve chamber cover, including a cover plate disposed above the gas chamber. One-way valves are evenly distributed on the top of the cover plate. A connecting plate is provided between the cover plate and the gas chamber. A sealing element is provided between the cover plate and the connecting plate. The sealing element includes a metal ring, with a rubber sleeve covering the metal ring. A pre-tightening mechanism is provided above the sealing element, comprising a bolt and a disc spring. In this utility model, by setting up a connecting plate, a liner plate, a cover plate, a sealing element, and a pre-tightening mechanism, and utilizing a disc spring, the vibration of the sealing element is reduced, improving its stability. By setting a one-way valve on the cover plate, a pressure balance channel is formed between the inner and outer sides of the cover plate, thereby achieving dynamic pressure compensation. This avoids uneven pressure at the joint surface between the cover plate and the connecting plate, prevents cover plate deformation, and thus prevents the sealing element from loosening and detaching from the mounting groove, improving the working stability of the sealing element.

The application discloses a kind of gas engine active precombustion chamber lean combustion comprehensive system and control method, belong to gas engine technical field.The system includes main combustion gas inlet pipeline, active gas inlet pipeline, active precombustion chamber and ECU.Active gas inlet pipeline is equipped with active gas inlet electric pressure regulating valve, active gas inlet total gas metering valve, each cylinder precombustion chamber entrance is equipped with active gas inlet single cylinder gas metering valve.ECU and gas inlet manifold pressure sensor and electric pressure regulating valve form closed loop pressure regulating unit, maintain the positive pressure difference between precombustion chamber and main combustion chamber;ECU and total metering valve, single cylinder metering valve, single cylinder exhaust temperature sensor form metering control unit, realize total air intake and single cylinder air intake independent closed loop regulation.The application controls precombustion chamber air intake pressure and each cylinder gas quantity accurately, combines the intercylinder balance control based on exhaust temperature, significantly improves the stability and uniformity of multi-cylinder gas engine lean combustion, effectively improves thermal efficiency.

The utility model provides a kind of ignition device, gas engine and production equipment, it is related to engine technical field, the ignition device includes primary coil, secondary coil, first magnetic element, second magnetic element, voltage monitoring coil and voltage indication module, wherein: primary coil and secondary coil are coupled by first magnetic element, and the number of turns of primary coil is less than the number of turns of secondary coil;Secondary coil and voltage monitoring coil are coupled by second magnetic element, and the number of turns of voltage monitoring coil is less than the number of turns of secondary coil;Voltage indication module is connected with voltage monitoring coil, voltage indication module is used to receive the first output voltage of voltage monitoring coil, and the size of the second output voltage of secondary coil is indicated according to first output voltage.The utility model can directly monitor the actual output voltage of ignition coil, improve voltage fluctuation monitoring precision and reliability under engine dynamic condition, reduce fault false alarm rate.

The invention belongs to the technical field of internal combustion engines, and provides a double-air-inlet-channel gas engine suitable for multiple fuels and an air inlet control method of the double-air-inlet-channel gas engine. The double-air-inlet-channel gas engine suitable for multiple fuels comprises an engine air cylinder, a piston, an air inlet channel and at least two kinds of gas inlet channel modules capable of being switched. The piston is arranged in the engine cylinder and does linear motion along the engine cylinder; the engine cylinder is provided with a cylinder cover, and the air inlet channel and the fuel gas inlet channel module are arranged on the cylinder cover. Each fuel gas inlet channel module has a cross sectional area suitable for being matched with a preset target gas fuel, and the cross sectional area is obtained through calculation based on the physical characteristics of the target gas fuel so as to ensure that the mass flow of fuel entering an air cylinder meets the requirement of the ideal air-fuel ratio under the standard working condition. The multi-fuel adaptability, the heat efficiency and the emission level of the engine are remarkably improved, meanwhile, the structure is simple, and the implementation cost is low.

The present application relates to the technical field of fuel injection components for dual-fuel and gas engines, and particularly relates to an adjustable flow gas injection valve; comprising a gland, a solenoid valve assembly, a valve housing, a limiting block, a valve sheet, a valve seat, a locking retainer, an internal hexagonal cylindrical head screw, an armature, an O-shaped sealing ring, a return spring, an elastic retainer and a wire welded filter screen. The present application adjusts the lift by rotating the valve seat after the valve seat is installed in the valve housing, and after the lift is determined, the valve seat is locked again by the locking retainer to improve the connection strength of the valve housing and the valve seat. In addition, the valve housing and the valve seat are respectively engraved with scale lines and pointer lines, and the lift value can be read on site while rotating the valve seat, so that the flexible adjustment of the injection flow of the gas injection valve is realized in the production and assembly stage, so that the injection flow of the valves in the same batch is kept highly consistent, the power performance of the engine is improved, and the structure is simple, easy to realize and high in adjustment precision.

The utility model provides a connecting rod weighing tool, and relates to the field of gas engines. The connecting rod weighing tool comprises a connecting shaft and two weighing assemblies, each weighing assembly comprises a positioning shaft, a base and an electronic scale, one electronic scale is placed below the corresponding base, the two bases are fixedly connected with the connecting shaft, each base is provided with a placement position, and the positioning shaft is fixedly connected with the positioning shaft. One positioning shaft is placed on the corresponding placing position, and the axes of the two positioning shafts are located on the same horizontal plane. The installation state of the connecting rod is simulated through the connecting shaft, the two positioning shafts and the base, then the large end and the small end of the connecting rod are accurately measured through the two electronic scales, the connecting rods with the weight difference value within the same range are matched to the same engine, the assembly quality is ensured, and operation noise is reduced.

The invention relates to the technical field of seawater desalination, and discloses a solar distillation seawater desalination system for multi-heat-source partition heat supply, which integrates a gas engine heat pump unit, a solar distillation unit and an optional salinity gradient energy utilization interface unit. The gas engine drives the compressor to operate and generates cylinder sleeve water and flue gas waste heat, and the cylinder sleeve water and the flue gas waste heat are introduced into the lower area of the solar distiller through the waste heat recovery unit to preheat seawater; the heat pump condenser exchanges heat with the upper middle area of the distiller to stably heat and evaporate interface water, so that different heat source partition heat supply modes are formed. And fresh water and concentrated solution generated by distillation are respectively collected. The salinity difference energy utilization interface unit is connected into the salinity difference energy utilization device when energy recovery is needed. The system realizes gradient utilization of multiple heat sources, improves the distillation efficiency and the operation stability, and can recycle salinity gradient energy as required.

The invention relates to the technical field of model airplane power devices, in particular to a modular integrated structure of a model airplane fuel gas power unit and a using method thereof.The modular integrated structure comprises a model airplane body, propellers are arranged at the end of the model airplane body, a containing cavity is formed in the model airplane body, and an external protective shell is arranged in the containing cavity; the external protective shell comprises a framework structure and a protective skin, and a machine cover is arranged at an external opening of the containing cavity. A gas engine body, a fuel supply module, an ignition control module and a vibration reduction mounting module are arranged on the framework structure. A power generation module is integrated on the gas engine body and used for generating electric energy. The fuel supply module is a pluggable fuel box and is detachably connected with the framework structure. The ignition control module is electrically connected with the power generation module and the fuel supply module and used for managing electric energy distribution and identifying fuel information. The vibration reduction mounting module is arranged between the gas engine body and the framework structure and used for isolating vibration. The structure is compact, and self-powered operation and rapid fuel replacement are achieved.

This invention discloses a direct injection mixing intake structure for an LNG gas engine, comprising a multi-point injection module. The multi-point injection module includes a guide vane, an intake manifold, a mixer, and nozzles. The intake manifold is connected to the guide vane, the mixer is located in the intake channel of the intake manifold, and the nozzles are mounted on the guide vane and connected to the mixer. Several sets of guide vanes from the multi-point injection modules are sequentially connected in series to form a gas passage. The nozzles of each set of multi-point injection modules inject the gas from the gas passage into the mixer of their respective multi-point injection module, where it mixes with air supplied to the intake manifold of that multi-point injection module to form a mixed gas. Each set of multi-point injection modules corresponds one-to-one with each cylinder of the gas engine, effectively ensuring that the mixed gas drawn into each cylinder maintains a uniform and stable air-fuel ratio.

The utility model relates to the technical field of engine crankcase, and disclose a kind of high-power gas engine crankcase forced closed ventilation system, including air filter, the air filter right part fixed mounting has intake pipe, the intake pipe right part fixed mounting has mixer, the mixer upper part fixed mounting has gas intake pipe, the mixer right part is fixedly connected with supercharger by pipeline, the supercharger bottom fixed mounting has supercharger mounting seat, the supercharger right part is fixedly connected with intercooler by pipeline, the intercooler right part fixed mounting has after intercooling intake pipe, using supercharger generates negative pressure, and air is forcedly inhaled into intake pipe, and flame arrester prevents backfire into oil-gas separator, and damper controls crankcase to keep constant negative pressure value, ensure that gas engine works stably, and oil-gas is separated after passing through oil-gas separator and then enters engine to participate in combustion, not only prevent the environmental pollution of oil-gas emptying, and improve the efficiency of gas engine.

The invention discloses a parameter correction system and method for low emission. The system comprises a gas machine aftertreatment device and an electric control unit. The gas machine post-treatment device comprises a first three-way catalyst converter, a second three-way catalyst converter and a particle trap; a temperature sensor is arranged between the first three-way catalyst converter and the second three-way catalyst converter, and a nitrogen oxide sensor is arranged between the second three-way catalyst converter and the particle trap; the temperature sensor and the nitrogen oxide sensor are electrically connected with the electric control unit respectively; the gas machine post-processing device is used for acquiring a first temperature and an actual oxygen concentration through a temperature sensor and a nitrogen oxide sensor and sending the first temperature and the actual oxygen concentration to the electric control unit; and the electronic control unit is used for correcting the original engine parameters of the engine and the sensor value of the nitrogen oxide sensor based on the first temperature and the actual oxygen concentration so as to optimize the performance and the fuel efficiency of the engine. According to the invention, the accuracy of emission control and the reliability of the system can be improved.

The disclosure describes assembly clips for use in attaching brush seals to static hardware components during the assembling of gas turbine engines. The clips are made of plastic which melts and vaporize during operation of the engine. The temporary clips provide an efficient means for attaching brush seals to subassemblies of gas turbine engines and which reduce or eliminate the potential for FOD / DOD risks.

The application discloses the technical field of electric power systems, and particularly relates to a gas generator set temperature measurement control method and system. Mainly used to solve the problem of low accuracy of temperature control of the existing generator set. Mainly includes obtaining the cylinder outlet temperature and the cylinder pressure of a plurality of gas generator sets, and determining the expected power generation of the gas generator set; determining the reference gas generator set based on the cylinder outlet temperature and the cylinder pressure, and determining the balance temperature of the reference gas generator set based on the expected power generation, wherein the balance temperature is used to represent the average temperature of the reference gas generator set during power generation according to the preset power generation; if the difference between the balance temperature and the historical temperature stability value of the gas generator set is less than the preset temperature threshold, then the temperature of the gas generator set is controlled based on the balance temperature. Mainly used for controlling the temperature of the generator set.

This application relates to the field of gas generator set technology and discloses a wear detection and analysis system for gas generator set components, aiming to solve the problems of delayed response and noise masking in generator set wear monitoring. The system includes: an in-situ sensing component composed of high-temperature resistant ultrasonic and eddy current sensors; a signal conditioning module integrating bandpass filtering; a high-speed data acquisition matrix based on FPGA; and a distributed analysis engine. The system utilizes crankshaft position trigger signals to achieve phase alignment and employs an evaluation method based on energy center of gravity drift. By adopting the above technical solution, this application can achieve full-time domain perception and microscopic quantitative measurement of component wear, significantly improving the accuracy, robustness, and specificity of early fault identification under complex operating conditions.

The utility model discloses gas supply system, gas engine system and vehicle, gas source, first switch valve, two interlocking switch valves, second switch valve of this gas supply system are communicated in proper order, and the inlet of release switch valve is communicated on the pipeline that two interlocking switch valves communicate between through the communicating pipe, and the outlet of release switch valve and the outlet of second switch valve all communicate with emptying mouth, the inlet of detection gas source and third switch valve communicates, and the outlet of third switch valve communicates on the pipeline that one of two interlocking switch valves downstream communicates with second switch valve, first pressure detection spare is set up on the pipeline that first switch valve and two interlocking switch valves communicate between, and second pressure detection spare is set up on the pipeline that one of two interlocking switch valves downstream communicates with second switch valve, and third pressure detection spare is set up on the communicating pipe, has promoted the accuracy whether release switch valve and two interlocking switch valves exist leak, and low in production cost.

The gas engine conversion device includes a housing, a battery receptacle coupled to the housing and configured to removably connect to a battery pack having memory-stored battery pack configuration data, a motor located within the housing, a power take-off shaft receiving torque from the motor and projecting from a side of the housing, a power switching network configured to selectively provide power from the battery pack to the motor, and a first electronic processor coupled to the power switching network and configured to control the power switching network to rotate the motor, the first electronic processor configured to receive the battery pack configuration data in response to connection of the battery pack to the battery receptacle and to control the power switching network based on the battery pack configuration data.

The invention provides a gas supply device of a gas engine, a detection method and the engine, which can be widely applied to the technical field of automatic detection, the gas supply device comprises a gas storage device and a vaporizer; the first heat exchanger is connected with the vaporizer through a first control valve; the first control valve is used for adjusting the flow of the first cooling source; the vaporizer is connected with the combustion chamber through a second control valve, and the second control valve is used for adjusting gas pressure; the first detection device is arranged on an outlet branch of the second control valve; the second detection device is arranged on an inlet branch of the combustion chamber; the control module is used for adjusting the first control valve and / or the second control valve through the detection value of the first detection device and / or the second detection device. The gas supply pressure and the gas supply temperature of the gas engine can be automatically adjusted, the gas supply stability of the engine is improved, and the safety performance of the engine is improved.

The invention relates to the technical field of plasma spraying, and discloses a supersonic spray gun for realizing multidirectional spraying of gas engine parts, which comprises a combustion chamber, a connector and a spray pipe which are arranged in sequence, a conveying pipe is connected outside the combustion chamber; a guide cylinder is arranged between the connector and the combustion chamber, and a plurality of drainage channels are formed in the guide cylinder; a powder conveying channel is arranged in the guide cylinder, one end of the powder conveying channel extends out of the connector, and the other end of the powder conveying channel points to the space between the connector and the guide cylinder. The spray pipe is detachably connected with the connector; and cooling devices for respectively and independently supplying circulating water are arranged outside the combustion chamber and the spray pipe. By changing the powdering position of the spraying material, the spraying material can be quickly, efficiently and fully hot-melted under any spraying condition, and the spraying quality is improved; the spray pipe and the connector are detachably mounted, and the spray pipe adopts an independent cooling circulation system, so that the spray pipe can be quickly replaced under the requirements of different spraying positions.

The utility model discloses a novel 20 cylinder gas engine camshaft relates to engine field. The novel 20 cylinder gas engine camshaft includes the neck of axle and the plurality of lugs and sprocket installed on it, the one side of neck is provided with installation component, the installation component includes the splicing block, the locating rod, the fixed disc and the locking bolt. The novel 20 cylinder gas engine camshaft passes through setting installation component, makes sprocket can be quickly, accurately installed to the neck, when also can easily complete when needing to disassemble, greatly shorten the assembly and maintenance time of engine, improved work efficiency. The locating rod is inserted through the first through -hole on sprocket and the second through -hole on fixed disc, provides accurate positioning for the installation of sprocket, the fixed disc is clamped in sprocket outside, and is closely connected through locking bolt and splicing block, further strengthens the stability of sprocket installation, effectively prevents sprocket loosening in the operation process of engine.

The utility model relates to the technical field of power supply, and discloses a power supply system for a charging station, which comprises a gas tank, the right side of the bottom of the gas tank is communicated with a gas delivery pipe, the outer wall of the gas delivery pipe is fixedly connected with a regulating valve, the right end of the gas delivery pipe is communicated with a gas engine, and the rear side of the gas engine is fixedly connected with a generator. And the front side of the gas engine communicates with a gas inlet pipe, two filter screens are fixedly connected to the interior of the gas inlet pipe, the right side of the generator is fixedly connected with an intelligent switching controller, and the bottom of the front side of the intelligent switching controller communicates with a plurality of electric wires. According to the utility model, when the mains supply is insufficient in the peak period, the intelligent switching controller judges that the mains supply power does not reach the standard and then starts the gas generator, the gas tank supplies gas through the gas delivery pipe, the gas engine combusts to drive the generator to convert electric energy, and the intelligent switching controller distributes the electric energy through the electric wire, so that the problem of power distribution in the peak period is solved.

The utility model discloses a kind of low heat value gas engine supercharger structure.The utility model includes: supercharger body, the supercharger body is provided with mounting seat, four groups of fixed screws are arranged on the mounting seat, the end surface of the mounting seat close to supercharger body is fixedly connected with two groups of bridge frame, the left and right sides of the bridge frame are slidably connected with limiting pressing plate, the one end of the limiting pressing plate close to bridge frame is fixedly connected with limiting side plate, two groups of guide rod are fixedly connected in the bridge frame, the limiting side plate is slidably connected with guide rod, spring is sleeved on the circumferential surface of guide rod, the both ends of spring are respectively abutted with two groups of limiting side plate, sliding rod is slidably connected on the upper end of bridge frame, by pulling sliding rod upwards, two groups of limiting pressing plate can slide to the inside of bridge frame, so that the position of limiting pressing plate can be conveniently operated, while when limiting strip is clamped into the inside of limiting slot, limiting pressing plate can be kept in the inside of bridge frame, so that the installation and disassembly of fixed screw are facilitated.