RU2254249C2 - System to control pressure in pneumatic system of traction vehicle - Google Patents

Abstract

FIELD: transport engineering.

SUBSTANCE: invention relates to methods of improvement of piston compressor plants. Shaft of compressor is connected with shaft of induction motor whose stator winding is connected to synchronous generator driven by shaft of heat engine, and rotor winding is connected through rectifier to armature winding of dc regulating machine whose field winding is connected with first control unit connected with first digital-analog converter connected to first output of microprocessor controller, with pneumatic system pressure transmitter being connected to first input through first analog-digital converter, and compressor shaft speed transmitter being connected to second input of microprocessor controller by means of second analog-digital converter. Second output of microprocessor controller is connected through digital-analog converter to control unit of contactor co0nnecting induction motor to synchronous generator, and third output of microprocessor controller is connected through third digital-analog converter with traction vehicle control unit.

EFFECT: provision of automatic maintenance of pressure in pneumatic system of traction vehicle irrespective of consumption of air, temperature and pressure of surrounding atmosphere.

2 cl, 6 dwg

Description

The present invention relates to the field of improvement of reciprocating compressor units of traction rolling stock, for example, diesel traction rolling stock, on which compressors are driven by a heat engine.

The following compressor drives are used on diesel traction rolling stock: mechanical, non-disconnectable from the main heat engine; electric, adjustable relay; hydrodynamic with adjustable clutch; drive from auxiliary heat engine (non-disconnectable).

External disturbing influences act on the pressure control object: air flow from the pneumatic system Q ₁ , temperature T _a and pressure ρ _{a of} atmospheric (intake) air. To maintain an adjustable value - pressure ρ _k in a given range, the automatic pressure regulator changes the regulatory effect - air supply Q ₂ in the pneumatic system.

The relay automatic pressure regulator has a static characteristic in the form of a loop, and when the automatic pressure control system is in operation, the value of ρ _k varies from ρ _k1 to ρ _k2 . The increase in pressure, ρ _k from ρ _k1 to ρ _k2 , is carried out during operation of the compressor with a maximum shaft rotation speed ω _{to max} and a maximum supply of Q _{2 max} . At the same time, the maximum wear rate of parts of the cylinder-piston group of the compressor and increased lubricant consumption are observed. Thus, a decrease in ω _k from 1450 to 710 rpm leads to a decrease in the wear rate of compression and oil scraper rings (from improved special phosphorous cast iron) of the first and second stages by 1.3–3 times, and cylinders by 2.5–3 times. The test results show that the wear rate of the compressor parts increases both with an increase in ω _k and with an increase in ρ _k , with a pressure ρ _k having a stronger effect on the increase in the wear rate.

A known automatic system for controlling the air pressure in the pneumatic system of a traction vehicle (locomotive), in which, when the maximum pressure in the pneumatic system of a diesel locomotive is reached, a relay automatic pressure regulator (actually a two-limit pressure switch) supplies compressed air to the cylinder of the spool drive controlling the filling of the hydrodynamic coupling of the piston compressor drive, spool moves to a position in which the oil supply to the cavity of the hydrodynamic coupling is stopped [1, p. 308; p.127, 218]. As the hydrodynamic clutch is emptied, the compressor slows down and finally stops. When the air pressure in the main air reservoirs (in the pneumatic system) of the locomotive reaches the minimum permissible value, the relay automatic pressure regulator stops the supply of compressed air to the drive cylinder of the control valve of the clutch filling, and the return spring of the spool moves it to the position at which oil is supplied to the hydrodynamic cavity couplings. The hydrodynamic clutch is filled with oil, and the compressor shaft rotates at maximum speed. This is the closest analogue.

An automatic pressure control system in a pneumatic system with mechanical or hydrodynamic compressor drives has low mounting flexibility due to the presence of a shaft line between the heat engine and the compressor. To significantly increase installation flexibility, electric (mainly direct current) compressor drives are used. However, all automatic pressure control systems in the pneumatic system of traction vehicles with electric drive of compressors are of relay action. An automatic pressure control system in a continuous pneumatic system allows not only to significantly reduce the wear rate of parts of the cylinder-piston group and lubricant consumption, but also has great mounting flexibility, which is very important to facilitate equipment placement.

The objective of the claimed invention is to reduce the wear of parts of the cylinder-piston group of the compressor and reduce lubricant consumption.

The essence of the claimed invention is that

- the compressor shaft is connected to the shaft of the asynchronous motor, the stator winding of which is connected to a synchronous generator driven by the shaft of the heat engine, and the rotor winding by means of a rectifier is connected to the armature winding of the DC regulating machine, the excitation winding of which is connected to the first control unit connected to the first digital-to-analog a converter connected to the first output of the microprocessor controller, to the first input of which by means of the first analog-to-digital converter I connected a pressure sensor in the pneumatic system, and a compressor shaft speed sensor is connected to the second input of the microprocessor controller using a second analog-to-digital converter, the second output of the microprocessor controller is connected to the control unit of the asynchronous motor connecting to the synchronous generator through the second digital-to-analog converter, and the third output microprocessor controller through the third digital-to-analog converter is connected to the unit Traction vehicle;

- a discharge valve connected to the fourth output of the microprocessor controller by a fourth digital-to-analog converter is included in the compressor discharge channel;

- the stator winding of the induction motor is connected to a machine phase splitter connected to a step-down transformer, or to a voltage and constant frequency converter that supplies auxiliary equipment;

- the asynchronous motor and the DC regulating machine are made in the form of a single-body unit, on the shaft of which the anchor of the DC regulating machine is mounted between the rotor and the rings of the asynchronous motor, and the stators of the asynchronous motor, the regulating DC machine and the rectifier are mounted in the common frame.

Figure 1 shows the static characteristic of an automatic pressure switch.

In the pneumatic system, when the automatic control system is operating, the pressure ρ _k varies from ρ _k1 to ρ _k2 . The compressor turns on at ρ _k = ρ _k1 and turns off at ρ _k = ρ _k2 . In this case, the compressor operates with a maximum supply of compressed air Q _{2 max} and a maximum shaft speed ω _{to max} .

Figure 2 - static characteristics of the automatic pressure regulator continuous.

Static characteristic 1 - by increasing the air pressure in the pneumatic system of ρ ρ _k1 to _k2 shaft rotation speed of the compressor decreases from ω _to ω _max to _k = 0.

Static characteristic 2 - when the pressure of compressed air in the pneumatic system increases from ρ _k1 to ρ _k2, the rotation speed of the compressor shaft decreases from ω _{to max} to ω _k2 = (0.12-0.17) ω _{to max} .

Figure 3 presents a schematic diagram of an automatic pressure control system in the pneumatic system of a diesel traction vehicle, which shows: 1 - compressor; 2 - asynchronous motor; 3 - DC regulating machine; 4 - synchronous generator; 5 - heat engine (diesel); 6 - rectifier; 7 - pneumatic system; 8 - pressure sensor; 9 - the first analog-to-digital Converter; 10 - programmable microprocessor controller; 11 - speed sensor; 12 - second analog-to-digital Converter; 13 - the first digital-to-analog converter; 14 - the first control unit; 15 - the field winding of the regulating DC machine; 16 - second digital-to-analog converter; 17 - the second control unit; 18 - contactor; 19 - the third digital-to-analog converter; 20 - the third control unit.

On figa shows the dependence of the relative power of the compressor on the relative speed of rotation of the compressor shaft by line 1.

On figb shows the dependence of the relative torque on the compressor shaft from the relative rotation speed of the compressor shaft.

On figv lines 3, 4 and 5 respectively show the dependence of the relative power of the compressor, the relative sliding power of the induction motor and the relative power on the shaft of the induction motor on the relative speed of rotation of the compressor shaft and the sliding of the asynchronous motor.

Figure 5 presents a structural diagram of a complex unit that combines in one housing an induction motor that regulates a direct current machine and a rectifier, where 21 is the stator of an induction motor; 22 - rotor of an induction motor; 23 - anchor of the regulating machine direct current; 24 - the field winding of the regulating DC machine; 25 - collector of a regulating DC machine; 26 - brushes DC control machine; 27 - a rectifier; 28 - contact rings; 29 - brushes of an induction motor; 30 - bed (body) of the unit; 31 - the shaft of the unit.

Figure 6 presents a schematic diagram of an automatic pressure control system in a pneumatic system of a diesel traction vehicle with an unloading valve, where 1 is a compressor; 2 - asynchronous motor; 3 - DC regulating machine; 4 - synchronous generator; 5 - heat engine (diesel); 6 - rectifier; 7 - pneumatic system; 8 - pressure sensor; 9 - the first analog-to-digital Converter; 10 - programmable microprocessor controller; 11 - speed sensor; 12 - second analog-to-digital Converter; 13 - the first digital-to-analog converter; 14 - the first control unit; 15 - the field winding of the regulating DC machine; 16 - second digital-to-analog converter; 17 - the second control unit; 18 - contactor; 19 - the third digital-to-analog converter; 20 - the third control unit; 32 - discharge valve; 33 is the fourth digital-to-analog converter.

Automatic pressure control system in the pneumatic system of a traction vehicle operates as follows. When ρ _to below ρ ₁ (see figure 2 and 3) the excitation current of the regulating DC machine 3 is equal to zero and the shafts of the induction motor 2, the regulating DC machine 3 and compressor 1 rotate at a speed of ω _{to max} , the compressor has a flow of Q _{2 max} and pressure ρ _k rises. When reaching _{to the} value ρ ρ _k1 begins _to change regulation ω DC excitation current regulating machine 3. If at steady speed ω _to increase the excitation current regulating DC machine, that it will increase the emf that will reduce the current in the rectifier circuit 6 and the rotor winding of the induction motor 2. As a result, the torque of the induction motor decreases and the speed ω _k begins to decrease. A decrease in ω _k occurs until the moment developed by the induction motor and the DC regulating machine increases to the value of the resistance moment of compressor 1 and the current in the rectifier circuit reaches a steady-state value. In this case, ω _k will be less than before increasing the excitation current of the regulating DC machine. On the contrary, with a decrease in the excitation current of the regulating DC machine, ω _k will increase. An increase in ρ _k leads to an increase in the excitation current of the regulating DC machine, a decrease in ω _k and the supply of compressor Q ₂ . When the compressor supply Q ₂ becomes equal to the flow rate Q ₁ , the steady-state mode of operation of the automatic pressure control system will come and ρ _k will be constant.

If ρ _k becomes equal to ρ _k2 , the excitation current of the regulating DC machine becomes maximum, the compressor stops and its supply becomes equal to zero. Thus, at different air flow rates from the pneumatic system of the traction vehicle, the automatic pressure control system will always maintain a supply of Q ₂ equal to the flow rate of Q ₁ when the pressure changes in the range from ρ _k1 to ρ _k2 .

The control program of the on-board microprocessor controller 15 contains the required algorithm for the operation of the automatic pressure regulator. For example, a program may contain the following task: at a decrease rate ρ _k greater than a given value, the microprocessor-based automatic pressure regulator must quickly increase ω _k and compressor flow Q ₂ to maximum values. This function cannot be implemented in known automatic pressure control systems in pneumatic systems of traction vehicles.

The automatic pressure control system in the pneumatic system of the traction vehicle is a closed automatic energy system. It is known that such systems, with a certain combination of the static and dynamic parameters of their elements, operating conditions and modes, can work poorly and even unstably, for example, in the mode of self-oscillations. The tasks of ensuring the stability and high-quality operation of microprocessor systems are solved by software using the methods of the theory of automatic systems.

In the proposed automatic pressure control system in the pneumatic system of a traction vehicle with an electric drive of a continuous compressor (see figure 3), the compressor 1 is driven from the shaft of an asynchronous motor 2 connected to the shaft of a DC regulating machine 3 (figure 4). The stator winding of the induction motor 2 is connected to the stator winding of the synchronous generator 4, driven by the shaft of the heat engine 5, and the rotor winding of the asynchronous motor 2 is connected to the rectifier 6. The pressure ρ _to in the pneumatic system 7 is measured by a pressure transducer 8 connected via the first analog-to-digital converter (ADC1) 9 to the first input of the microprocessor 10. The programmable controller of the asynchronous motor shaft rotation speed 2, regulating the DC machine 3 and the compressor 1 are measured _to ω is rotational speed sensor 11 connected via a second analog-to-digital converter (ADC2) 12 to the second input of the microprocessor programmable controller 10. The microprocessor programmable controller 10 is connected via the first digital-to-analog converter (DAC1) 13 to the first control unit 14 connected to the excitation winding 15 of the regulating DC machines 3, through the second digital-to-analog converter 16 - with the second control unit 17 of the contactor 18, and through the third digital-to-channel traction converter 19 - the third control unit 20 of the thermal engine 5.

Analysis of certain types of losses in the brake compressors of traction vehicles and a generalization of the results of experimental studies show that when operating piston compressors with a variable ω _к and constant ρ _к , their characteristics are as shown in Fig. 4 (dependences of the relative compressor power - lines 1 and 3 , moment - line 2, slip power of the induction motor - line 4 and power on the shaft of the induction motor - line 5, from relative ω _to ). It can be seen from the drawing that the power consumed by the compressor is proportional to ω _k and in the range relative to ω _k = (0-0.17) ω _{k max} it is practically zero. The maximum slip power of an induction motor is at S = 0.4 and it is five times less than the rated compressor power. The sliding power of the induction motor is returned to the compressor shaft using a DC regulating machine, therefore, the power on the shaft of the asynchronous motor changes according to characteristic 5. For relative ω _to close to 1.0, the moment on the compressor shaft is created mainly by the induction motor, but as reducing ω _to an increasing part of the load perceives the regulating DC machine. However, since the compressor power decreases with decreasing ω _k , the sliding power of the induction motor and the power of the DC regulating machine decrease.

The proposed electric compressor drive is characterized by a number of positive qualities: 1) this drive is an AC drive, i.e. connects directly to an AC source without intermediate converters; converters in the rotor circuit serve only to control the speed of rotation; 2) the basis of the drive is an asynchronous motor, simpler, more reliable and does not require such maintenance care as DC machines; 3) this drive is economical, since the efficiency of an induction motor is slightly higher than the efficiency of a DC machine, and only part of the energy proportional to the slip is subjected to conversion; 4) the drive provides smooth control of speed and torque and does not require a large number of power contact equipment; 5) the drive has low control power, is easy to automate, has good dynamic qualities; The efficiency and power factor of such a drive are little dependent on ω _k , but are determined mainly by the compressor moment; when changing ω _to in the operating range, these coefficients vary in the range of 0.80-0.85.

The proposed electric compressor drive wins significantly in its technical and operational qualities if the asynchronous motor, DC regulating machine and rectifier are made in the form of one integrated unit, the structural diagram of which is shown in Fig.5.

In order to reduce the acceleration time when starting the electric drive of the compressor in the microprocessor-based automatic pressure control system, an unloading valve 32 is used, connected via the fourth digital-to-analog converter (DAC4) 33 to the fourth output of the microprocessor controller 10 (see Fig. 6). When you turn on using the contactor 16 of the electric drive of the compressor, the valve 32 is turned on and connects the discharge cavity of the compressor 1 with the atmosphere. When reaching ω _k , for example, the value ω _k = (0.13-0.17) ω _{k max} valve 32 is turned off and the compressor supplies compressed air to the pneumatic system 7. However, despite the use of pressure relief valves in relay automatic control systems, a large number of failures of electric compressor drives on electric locomotives due to the combustion of the windings of electric motors [2].

The technical result from the use of the proposed continuous automatic pressure control system in the pneumatic system of a traction vehicle also consists in a significant reduction in the wear rate of parts of the cylinder-piston group of the compressor and a decrease in lubricant consumption with continuous pressure control ρ _{to the} most efficient way - a smooth change in the speed of rotation of the compressor shaft ω _k, thus reducing the compressor at a maximum rotational speed ω _max and _a maximal SG pressure _to ρ _max.

Sources of information

1. Diesel locomotives. Construction, theory and calculation. / Ed. N.I. Panova. - M.: Mechanical Engineering, 1976 .-- 544 p.

2. Manypin A.P. Summarizing the experience of operating high-speed transport compressors. Proceedings of VNITI, 1973, Iss. 38.

Claims (2)

1. An automatic pressure control system in the pneumatic system of a traction vehicle, comprising a compressor connected to a shaft of a DC regulating machine, characterized in that the compressor shaft is connected to a shaft of an induction motor, the stator winding of which is connected to a synchronous generator driven from the shaft of the heat engine, and the rotor winding by means of a rectifier is connected to the anchor winding of the regulating DC machine, the excitation winding of which is connected to the first block control connected to the first digital-to-analog converter connected to the first output of the microprocessor controller, the pressure sensor in the pneumatic system is connected to the first input of which by means of the first analog-to-digital converter, and the compressor shaft speed sensor is connected to the second input of the microprocessor controller by the second analog-to-digital converter , the second output of the microprocessor controller is connected to the unit by means of a second digital-to-analog converter m contactor control connection induction motor to a synchronous generator, and the third output of the microprocessor via a third digital to analog converter connected to the control unit driving the vehicle. 2. The automatic pressure control system in the pneumatic system of a traction vehicle according to claim 1, characterized in that a discharge valve is connected to the compressor discharge channel, connected via a fourth digital-to-analog converter to the fourth output of the microprocessor controller.

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