42 results about "Exhaust brake" patented technology

A turbocharger with a bleed air brake function relates to the technical field of internal combustion engine supercharging devices and comprises a turbine, the turbine comprises a volute, and a turbine is rotatably arranged in the volute; a first flow channel and a second flow channel which are used for introducing waste gas are arranged on the volute, the first flow channel is communicated with a turbine flow channel, the second flow channel is communicated with a turbine back disc through a perforated heat insulation cover, and a flow channel switching mechanism which is used for connecting and disconnecting the first flow channel or the second flow channel is arranged on the volute. The problems that in the prior art, after an exhaust brake valve is closed, axial force borne by a thrust bearing is instantly and greatly improved compared with axial force in a normal working state, so that the bearing capacity of the thrust bearing is insufficient, and abrasion of the thrust bearing is accelerated are solved; and the exhaust pressure of the engine cannot be released, so that air leaks from a gap between a sealing ring at the turbine end and a sealing ring groove.

The invention discloses an auxiliary braking control method and system and a vehicle, and the method is executed by an auxiliary braking controller and comprises the steps that vehicle driving parameters and a vehicle slope state are obtained; and when the vehicle driving parameters meet the preset conditions and the vehicle slope state is in the downhill state, it is judged that the auxiliary brake starting conditions are met, and exhaust brake control and engine brake control are started. According to the auxiliary braking system, the mechanical pump engine can still conduct auxiliary braking under the condition that no ECU exists, it can be ensured that the auxiliary braking function is timely, effectively and reasonably started and stopped, and meanwhile the main braking intervention requirement judgment capacity, the upshift requirement judgment capacity and the overproof engine protection alarm capacity are achieved.

The invention relates to an exhaust brake electromagnetic valve. According to the electromagnetic valve, a main gas circuit unit, a proportional electromagnetic driving structure, a gas circuit switching structure and a gas pressure detection structure are integrated. Continuous and linear accurate adjustment of output air pressure is realized through a proportional electromagnetic driving structure; the gas path switching structure can intelligently switch gas flow between the first gas outlet and the second gas outlet according to an instruction; the pressure sensor integrated in the valve body monitors the actual output air pressure in real time, closed-loop feedback control is formed, and accurate matching of braking force is ensured. The system is compact in structure, remarkably reduces external pipelines and leakage points, has the advantages of being rapid in response, accurate in control, high in reliability and high in adaptability, and remarkably improves the smoothness and safety of vehicle braking.

This specification discloses an exhaust braking control method, system, computing device, storage medium, and vehicle. In this method, when a hybrid vehicle is operating on a long downhill slope and the generator set enters a power-consuming state, the engine is put into in-cylinder braking or exhaust braking mode, and the generator is in speed mode. In the control of the generator's target speed, a torque limit calculated by mechanical power is added. This torque limit restricts the integral part of the speed loop and the proportional-integral sum in the generator control, improving the power response of the generator's exhaust braking and avoiding excessive overshoot. By having the generator drive the engine to consume excess feedback energy, the battery charge can be dynamically adjusted, ensuring that the feedback energy generated during drive auxiliary braking does not lead to overcharging, and also ensuring the auxiliary braking of the drive motor, thereby improving vehicle driving safety.

The invention discloses a diesel engine aftertreatment system heat management control method, system and device and a storage medium. The method comprises the steps that working condition information, exhaust passage temperature information, carbon load information and engine working condition information of a target vehicle are obtained; determining a thermal management mode of the post-processing system based on the working condition information, the exhaust passage temperature information and the carbon load information; target control parameter information is calculated based on the engine working condition information and the thermal management mode in combination with the MAP; based on the target control parameter information, a cooperative control instruction set is generated, and the cooperative control instruction set is used for controlling an engine braking device, an exhaust braking valve, an air inlet throttling valve and a high-pressure common rail oil injection system to conduct cooperative operation. The technical problems that the post-processing system is high in heat management cost and poor in post-processing control precision and reliability are solved.

The utility model relates to the technical field of locomotive control, and provides a locomotive emergency braking exhaust system which comprises a shunting portable table, a shunting locomotive controller and a locomotive emergency braking exhaust device, and the shunting portable table is used for being held by a worker; the shunting locomotive controller is in communication connection with the shunting portable station; the locomotive emergency braking air exhaust device is in wired communication connection with the shunting locomotive controller, the locomotive emergency braking air exhaust device is arranged in a shunting locomotive and connected to an air exhaust port of a locomotive auxiliary air cylinder, and the locomotive emergency braking air exhaust device is used for controlling the locomotive auxiliary air cylinder to conduct air exhaust braking. The locomotive emergency braking exhaust device is light in size, single in function and capable of being jointly controlled with an existing shunting locomotive controller, the locomotive emergency braking effect is achieved, a locomotive driver does not operate the locomotive by mistake, and the personal safety of driving operators is effectively guaranteed.

The invention relates to a zero-band wet-exhausting type brake which comprises a brake shell, a clutch shell and a rear shell, a driving gear hub is connected in the brake shell, a transmission shaft is connected in the clutch shell, a driven gear hub is arranged on the transmission shaft in a sliding mode, a friction plate assembly is arranged on the transmission shaft in a sliding mode, and a first elastic unit and a piston are arranged in the brake shell in a sliding mode. The first oil inlet leads to a piston cavity of the piston; a service brake piston is embedded in the left end of the rear shell, and a piston cavity of the service brake piston communicates with the second oil inlet. A parking piston is slidably connected into the rear shell, the right side of the parking piston is connected with a second elastic unit, a push-pull shaft axially penetrates through the transmission shaft and the parking piston, the left end of the push-pull shaft is in bearing connection with a driven gear hub, and hydraulic oil can enter from a third oil inlet to push the parking piston and the push-pull shaft to retreat. According to the invention, the parking piston is separated from the transmission shaft, and the driving gear hub is separated from the driven gear hub, so that the external transmission shaft is not mechanically connected with the friction plate assembly, and zero belt displacement torque is realized.

The invention relates to the technical field of ships, and particularly discloses a cargo hold ventilation control system, a ventilation control method and a ship, the system comprises an air inlet mechanism, an air exhaust mechanism, a temperature adjusting part, an in-cabin temperature sensor and a control part, the air inlet mechanism comprises an air inlet, an air inlet pipe, an air inlet brake and a fan, the air inlet is formed in a cargo hold, and the air exhaust pipe is arranged in the cargo hold; the air inlet pipe is communicated with the air inlet and the cargo hold, the air inlet brake is used for opening and closing the air inlet, the fan is used for introducing air outside the cargo hold into the cargo hold, the air exhaust mechanism comprises an air exhaust opening and an air exhaust brake, the air exhaust opening is formed in the cargo hold, the air exhaust brake is used for opening and closing the air exhaust opening, and the temperature adjusting part is used for adjusting the temperature of air in the air inlet pipe. The in-cabin temperature sensor is used for detecting the temperature of the cargo cabin, and the air inlet brake, the air exhaust brake, the fan and the in-cabin temperature sensor are all in communication connection with the control part; the method is applied to the ventilation control system. The ship comprises the ventilation control system. According to the system, temperature range adjustment in the cargo hold is wider, and the stability of the storage environment in the cargo hold is effectively improved.

The present application relates to a kind of vehicle and its regenerative braking auxiliary control method and system, belong to new energy regenerative braking system and engine exhaust brake technical field.The present application obtains regenerative braking request power and battery allowed recharging power when vehicle braking, when regenerative braking request power is greater than or equal to battery allowed recharging power, engine exhaust brake power and drive motor regenerative braking power are determined according to the difference between regenerative braking request power and battery allowed recharging power, drive motor is controlled according to the determined regenerative braking power to carry out regenerative braking, and exhaust brake valve is closed, by controlling generator to drag engine, so that engine speed reaches the speed value corresponding to the engine exhaust brake power, the method can solve the problem of insufficient regenerative braking caused by the limited battery recharging capacity when vehicle is full or battery low temperature, avoid braking feeling inconsistency and regenerative braking failure when long downhill and other problems.

The present invention discloses a method for controlling auxiliary braking of a hybrid vehicle, and relates to the technical field of vehicle auxiliary braking. The method for controlling auxiliary braking of a hybrid vehicle uses the vehicle speed at the moment of entering auxiliary braking as the target vehicle speed. When controlling the motor and the engine to jointly provide auxiliary braking force, the engine exhaust brake is controlled to provide maximum braking torque, and the motor is controlled to gradually increase the braking torque. The motor gradually increases the braking torque at a first preset step size until the acceleration of the hybrid vehicle is less than zero. When the acceleration of the hybrid vehicle is less than zero, the braking torque jointly provided by the engine and the motor at this moment is maintained, so that the vehicle speed is reduced until the speed of the hybrid vehicle reaches the target vehicle speed. When the motor and the engine jointly provide auxiliary braking force, the control difficulty when the two jointly provide auxiliary braking force is reduced, and accurate response of the auxiliary braking force is achieved.

The utility model belongs to the technical field of engines, and particularly relates to an exhaust brake butterfly valve device and an engine assembly. The exhaust brake butterfly valve device comprises a base, a butterfly valve assembly, a driving assembly and a limiting assembly are arranged on the base, the butterfly valve assembly comprises a valve body and a valve plate, the valve body is connected with the base, the valve plate is rotatably arranged in the valve body and is in transmission connection with the driving assembly, and the driving assembly is used for driving the valve plate to rotate. The limiting assembly comprises a gas conveying pipe, the gas conveying pipe is connected with the base, and the gas conveying pipe is used for conveying limiting gas applying resistance to the driving assembly. By means of the exhaust brake butterfly valve device in the technical scheme, the problem that the exhaust pressure is too large due to the fact that the exhaust brake butterfly valve is fully closed at the high rotating speed and the high exhaust flow is effectively solved, and therefore the reliability problems of abrasion of a thrust bearing of a supercharger, overtemperature of an oil head of an oil sprayer and the like are reduced.

The present invention belongs to the technical field of exhaust throttle valves and discloses a method for durability testing of diesel engine exhaust throttle valves, comprising: determining whether the diesel engine's overall performance indicators, thermal management indicators, and exhaust braking indicators meet durability test requirements; controlling the diesel engine to perform the test according to a cyclic program; completing the cyclic test when the diesel engine performs the cyclic program a set number of times; detecting whether the overall inspection indicators of the diesel engine that has completed the cyclic test meet overall evaluation standards; and disassembling the diesel engine that has completed the cyclic test to detect whether the valve body inspection indicators of the exhaust throttle valve meet valve body evaluation standards. The diesel engine exhaust throttle valve durability testing method of the present invention is based on a diesel engine bench durability test and covers the thermal management and exhaust braking operating conditions of the exhaust throttle valve. It can more accurately assess the durability of the exhaust throttle valve and minimize user risks.

The application belongs to the field of engine control, and discloses a control method for exhaust brake pressure maintenance, an engine and a vehicle, which are applied to an engine system, wherein an air inlet manifold of the engine system is respectively connected with an outlet of a compressor and an inlet of a cylinder, a throttle valve is arranged on an upstream of the air inlet manifold, an exhaust manifold is respectively connected with an outlet of the cylinder and an inlet of a turbine, an exhaust brake valve is arranged downstream of the turbine, an engine control unit is electrically connected with the turbocharger, the throttle valve and the exhaust brake valve, and the method comprises the following steps: S1, a main charge model, i.e., a dynamic exhaust manifold pressure model, is established, and the intake and exhaust are calculated by two sets of equations; S2, the main charge model is corrected; and S3, closed-loop control of a target exhaust manifold pressure is performed. Through the designed algorithm, the maximum braking power is maintained during exhaust braking by combining the transient prediction algorithm with the closed-loop control of the intake flow, and the engine components are prevented from being damaged by the excessively high exhaust pressure under the transient working condition.

The utility model discloses an armored vehicle chassis gas circuit system, which belongs to the technical field of chassis gas circuit systems, and comprises an engine, a four-pipeline protection valve and a seven-way pipe, the seven-way pipe is fixedly connected with an exhaust brake control valve, a gear section and a manual control valve, a high-low gear conversion cylinder is fixedly connected to the gear section, an air compressor and a pair of exhaust brake control cylinders are arranged in the engine, and a rear transmission case differential lock and a clutch working cylinder are fixedly connected to one side of the engine. According to the technical scheme, the vehicle can be braked more sensitively and quickly in the running process, so that the running safety is improved, meanwhile, the vehicle can normally work under various working conditions in various gas path braking elements such as a four-loop protection valve, a brake valve and a relay valve, and potential safety hazards caused by gas path problems in running are avoided.

1. The name of the design product: controllable tail of the locomotive platform host. 2. The use of the design product: with controllable tail of the host, tail control box, with train tail wind pressure query, exhaust brake, low wind pressure alarm and other functions. 3. The design points of the design product: in the perspective. 4. The picture or photo that can best show the design points: perspective.

The utility model relates to the technical field of engine exhaust braking, and discloses a novel engine exhaust braking butterfly valve which comprises a fixing table, an installation plate is fixedly installed on the left side of the fixing table, a valve pipe is fixedly installed on the right side of the bottom of the fixing table, and an airflow sensor is fixedly installed on the left side of the valve pipe. The raft plate is controlled to rotate through operation of the electric push rod to close the valve pipe, and when the valve pipe is not completely sealed by the raft plate through detection of the airflow sensor on airflow, the power supply controller provides power for the air pump through the two groups of contact pairs, air is pumped into the air bag, the valve pipe is further sealed by the air bag, and the valve pipe is sealed by the air bag. Compared with a traditional device, the device can control the operation time of the air pump, when the air bag completely seals the valve pipe, the air pump stops operating, when the air pump stops supplying air, the air inlet pipe can be plugged by the plug, air in the air bag is prevented from escaping, energy is saved, and the sealing performance is improved.

The invention relates to an exhaust brake electromagnetic valve. According to the electromagnetic valve, a main gas circuit unit, a proportional electromagnetic driving structure, a gas circuit switching structure and a gas pressure detection structure are integrated. Continuous and linear accurate adjustment of output air pressure is realized through a proportional electromagnetic driving structure; the gas path switching structure can intelligently switch gas flow between the first gas outlet and the second gas outlet according to an instruction; the pressure sensor integrated in the valve body monitors the actual output air pressure in real time, closed-loop feedback control is formed, and accurate matching of braking force is ensured. The system is compact in structure, remarkably reduces external pipelines and leakage points, has the advantages of being rapid in response, accurate in control, high in reliability and high in adaptability, and remarkably improves the smoothness and safety of vehicle braking.

The present invention discloses a band brake control system, comprising: a flow amplification valve, a first control solenoid valve for controlling holding brakes, and a second control solenoid valve for controlling emergency and parking brakes, connected in series. The flow amplification valve is connected to the band brake via a switching valve and a function switching valve. When the first and / or second control solenoid valves lose power, the flow amplification valve is in the exhaust position, and gas within the band brake is discharged through the function switching valve and the switching valve to the flow amplification valve, thereby applying the brake. The band brake control system designed in the present invention not only applies band brakes in emergency, parking, and holding brake conditions, but also meets the control requirements of air-filling / air-exhausting brakes. It also comprehensively considers various operating conditions, including normal, fault, and rescue conditions, ensuring system safety guidance in the event of a system failure.

A method of manufacturing a butterfly member of an exhaust brake valve assembly. The method includes providing a metal material, machining the metal material to form a body, and drilling a through bore in a central portion of the body, thereby delimiting a first side of the body from a second side of the body that is opposite the first side. The through bore is configured to receive a shaft for pivoting movement of the body in a valve housing of the exhaust brake valve assembly. The method further includes positioning the body for a single machining operation and machining the body to form a first sealing face on the first side of the body and a second sealing face on the second side of the body. The first sealing face defines a first plane and the second sealing face defines a second plane spaced from the first plane.

The embodiment of the invention relates to a gear shifting control method and device, equipment and a medium, and the method comprises the steps that under the condition that an exhaust braking unit of a target vehicle is in an activated state, whether associated working condition information of the target vehicle meets gear shifting control conditions or not is judged; wherein the associated working condition information is working condition information having an association relationship with the exhaust braking unit; if the associated working condition information meets the gear shifting control condition, the clutch pressure value of the target vehicle is determined according to the engine rotating speed of the target vehicle; and gear shifting control is conducted on the target vehicle according to the clutch pressure value. According to the scheme, fine control over the clutch pressure value based on the engine rotating speed is achieved under the actual action of the exhaust brake unit, clutch control is more accurate during gear shifting, gear shifting impact is avoided, the reliability of the hydraulic automatic transmission is improved, power output is more stable, and the gear shifting experience of a user is improved.

The application discloses an exhaust brake valve sticking diagnosis method, device, equipment, storage medium and product. The method comprises the following steps: when it is detected that the vehicle engine is successfully started, the engine speed and the current vehicle working condition in a preset time period are acquired; if it is determined that the preset first exhaust brake valve sticking judgment condition is met according to the engine speed and the current vehicle working condition, the exhaust brake valve is controlled to enter an inspection state, and the opening and closing state of the exhaust brake valve is controlled in the inspection state, and the maximum fuel injection amount and the minimum fuel injection amount of the exhaust brake valve in the opening and closing state are detected; the fuel injection amount deviation is determined according to the maximum fuel injection amount and the minimum fuel injection amount; the sticking diagnosis result of the exhaust brake valve is determined according to the fuel injection amount deviation, and the vehicle control strategy is generated according to the sticking diagnosis result. The technical scheme of the embodiment of the application improves the sticking diagnosis reliability and accuracy of the exhaust brake valve.

The invention discloses a method for monitoring exhaust brake pressure of an engine, relates to the technical field of exhaust brake of internal combustion engines, and solves the technical problem that the existing exhaust brake test mode cannot effectively detect exhaust brake butterfly valves of engines produced in batches to cause valve faults. The method comprises the steps that actually-measured pressure values after EGR cooling under different engine working conditions are obtained, an exhaust braking pressure calculation value is obtained through calculation according to the actually-measured pressure values after EGR cooling, and when the exhaust braking pressure calculation value is smaller than a preset exhaust braking pressure threshold value, the exhaust braking function of the engine is normal. According to the invention, efficient utilization of resources is realized, and the maintenance cost is reduced.

The invention provides an exhaust brake control method and device for a large-tonnage mining truck, and the method comprises the steps: obtaining the operation state information of the mining truck through a vehicle control unit, and forming a control instruction according to the operation state information of the mining truck; the vehicle control unit sends the formed control instruction to an engine controller; and the engine controller controls the engine according to the control instruction so as to reduce the rotating speed of the engine. The running state information of the mining truck is obtained, the control instruction is formed according to the running state information of the mining truck, and the engine is controlled through the control instruction to reduce the rotating speed of the engine of the truck, so that the vehicle speed is reduced in a short time, and the problem that the brake heating temperature is too high when the large-tonnage mining truck goes downhill for a long distance is solved.

The present invention discloses a valve bridge, a brake actuator, an exhaust brake system, a method and an engine, wherein the valve bridge comprises a valve bridge body, a sliding valve, a piston-connecting rod assembly, a first reset member and a second reset member, wherein a brake valve clearance is provided between the sliding valve and the valve bridge body; the sliding valve is slidably arranged in the middle of the valve bridge body and is provided with an oil inlet state and an oil drain state; the piston-connecting rod assembly is located between the sliding valve and the valve bridge body and is provided with a locked state and an unlocked state; the first reset member is used to drive the sliding valve to reset; the second reset member is used to drive the piston-connecting rod assembly to reset; in the embodiment of the present invention, the brake valve clearance is located in the middle of the valve bridge, therefore, during the exhaust brake process, the middle of the valve bridge is subjected to force, and the force is evenly applied without causing tilting, thereby improving the stability of the valve bridge when returning and reducing the impact when the valve bridge returns.

The invention discloses an exhaust brake valve clamping stagnation diagnosis method, device and equipment, a storage medium and a product. The method comprises the steps that when it is detected that a vehicle engine is successfully started, the engine rotating speed and the current vehicle working condition in a preset time period are obtained; if it is determined that the preset clamping stagnation judgment condition of the first exhaust brake valve is met according to the rotating speed of the engine and the current vehicle working condition, the exhaust brake valve is controlled to enter a checking state, the opening and closing state of the exhaust brake valve is controlled in the checking state, and meanwhile the maximum oil injection quantity and the minimum oil injection quantity of the exhaust brake valve in the opening and closing state are detected; according to the maximum fuel injection quantity and the minimum fuel injection quantity, the fuel injection quantity deviation is determined; and according to the oil injection quantity deviation, the clamping stagnation diagnosis result of the exhaust brake valve is determined, and a vehicle control strategy is generated according to the clamping stagnation diagnosis result. According to the technical scheme, the clamping stagnation diagnosis reliability and accuracy of the exhaust brake valve are improved.

The application discloses an auxiliary brake control method, a control system and a vehicle. The method is executed by an auxiliary brake controller and comprises the following steps: acquiring vehicle running parameters and a vehicle slope state; when the vehicle running parameters meet preset conditions and the vehicle slope state is in a downhill state, it is determined that the auxiliary brake opening conditions are met, and exhaust brake control and engine brake control are started. The application realizes auxiliary brake of a mechanical pump engine under the condition of no ECU, and ensures that the auxiliary brake function is timely, effectively and reasonably started and stopped, and the auxiliary brake function has the determination ability of main brake intervention demand, the determination ability of gear up demand and the alarm ability of engine protection exceeding the standard.

The application discloses a mine dump truck engine overspeed inhibition and an implementation method thereof; the engine overspeed inhibition comprises an engine, an engine controller ECU, an engine rotating speed sensor, a vehicle speed sensor, an exhaust brake mechanism, a hydraulic retarder, a hydraulic retarder controller RCU, a vehicle controller ACU, an inclination sensor, a data recorder, an accelerator pedal and a weighing system; the engine controller ECU, the hydraulic retarder controller RCU, the vehicle controller ACU, the data recorder and the weighing system are connected on the same bus; the inclination sensor is connected to the vehicle controller ACU, and the inclination sensor is installed on the mine dump truck; the application can effectively prevent the engine from overspeeding due to the mismatch between the gear and the vehicle speed, and guarantee the safety, the intelligence and the convenience of the brake system of the mine dump truck; and the application makes the mine dump truck safer and more intelligent when the mine dump truck continuously goes downhill under heavy load.

The utility model discloses exhaust brake vehicle performance test equipment, and relates to the field of exhaust equipment. The exhaust brake vehicle performance test equipment comprises an engine, an exhaust unit, an air storage unit and a data processor, the exhaust unit is connected with the engine, the exhaust unit comprises an exhaust brake valve and an air pressure sensor, the exhaust brake valve is used for opening and closing an engine exhaust channel, the air pressure sensor is installed on the exhaust brake valve, and the air storage unit is connected with the data processor. And the air pressure sensor is used for detecting the back pressure of the exhaust channel. According to the exhaust brake whole vehicle performance test equipment, the air pressure sensor is directly installed on the exhaust brake valve, the back pressure of an exhaust channel can be accurately detected in real time, data are transmitted to the data processor to be displayed, and a tester can visually know the working state of an exhaust brake system conveniently. And a plurality of selectable air leakage holes are formed in the disc, so that the air leakage holes with proper hole diameters and quantity can be selected for exhausting according to different test requirements.

Embodiments of the present disclosure relate to a gear shifting control method, device, equipment and medium. The method comprises: in the case that the exhaust brake unit of a target vehicle is in an activated state, judging whether the associated working condition information of the target vehicle meets the gear shifting control condition; wherein the associated working condition information is working condition information having an associated relationship with the exhaust brake unit; if the associated working condition information meets the gear shifting control condition, determining the clutch pressure value of the target vehicle according to the engine speed of the target vehicle; and performing gear shifting control on the target vehicle according to the clutch pressure value. In the above scheme, in the case that the exhaust brake unit actually functions, the fine control of the clutch pressure value based on the engine speed is realized, so that the clutch control is more accurate during gear shifting, gear shifting impact is avoided, the reliability of the hydraulic automatic transmission is improved, the power output is more stable, and the gear shifting experience of the user is improved.

This utility model proposes an exhaust structure for an exhaust brake control cylinder, including a cylinder body with a piston chamber inside. The front end of the cylinder body has a connecting hole that communicates with and penetrates the piston chamber. The outer diameter of the cylinder body segment corresponding to the piston chamber is larger than the outer diameter of the segment corresponding to the connecting hole. The two cylinder body segments are connected by an inclined plane. An exhaust hole penetrating the inclined plane is provided on the bottom surface of the piston chamber near the connecting hole. Two ends of a cover are respectively wrapped around the outer walls of the two cylinder body segments. The cover has through holes with filters installed at the through holes. A cover is installed at the exhaust hole of the cylinder body, forming an air chamber between the cover and the outer wall of the cylinder body. The cover has through holes with filters installed at the through holes, thus forming an air path of outside—through hole—air chamber—exhaust hole—piston chamber. The filter prevents external debris from entering the piston chamber.