CN102434502B - Frequency-conversion pump controlled steering hydraulic system for loader - Google Patents

Abstract

The patent of the invention is a new type of loader steering hydraulic system, which uses an AC motor to drive a quantitative pump as the main oil supply source, and an accumulator as an auxiliary oil supply source. In the initial stage of the steering of the loader, the accumulator supplies oil to the steering hydraulic cylinder alone, and when the AC motor is started, the quantitative pump driven by the AC motor supplies oil to the steering hydraulic cylinder alone. In this way, the steering system can be improved. The response speed is fast, and energy consumption is saved at the same time; when the loader is completed, if the pressure in the accumulator is low, the AC motor can be used to drive the quantitative gear pump to charge high-pressure oil into the accumulator. The main advantage of this hydraulic system is its high efficiency.

Description

Frequency conversion pump control steering hydraulic system of loader

technical field

The patent of the invention relates to an energy-saving loader steering hydraulic system, which belongs to the field of construction machinery energy conservation.

Background technique

At present, there are two main ways to supply oil to the steering hydraulic system of the loader: 1. Use a quantitative pump to supply oil to the steering hydraulic cylinder; 2. Use a variable pump to supply oil to the steering hydraulic cylinder. The advantage of the quantitative pump oil supply method is low cost and high reliability; the disadvantage is that the efficiency is very low, which is between 10% and 30%. The main reasons for the low efficiency are: 1. Taking the domestic 50 loader as an example, for safety reasons, when the engine of the loader is idling (about 750r/min), the quantitative pump should be able to provide enough oil to the steering hydraulic cylinder. When the loader works normally, the engine speed is generally around 1700r/min. At this time, the oil output by the quantitative pump exceeds the hydraulic oil demand of the steering hydraulic cylinder, and the excess oil flows back to the oil tank through the valve, resulting in more throttling. Loss; 2. When the loader does not turn, the quantitative pump still outputs hydraulic oil at a lower pressure, resulting in greater energy loss. The advantage of variable pump oil supply is high efficiency; the main disadvantages are: high cost, complicated maintenance, and low reliability of domestic variable pumps, so domestic medium and low-end loaders still use quantitative pumps in large numbers. the

Contents of the invention

The invention proposes a novel frequency conversion pump control steering hydraulic system of a loader to overcome the deficiency of low efficiency of the existing loader steering system.

Technical solution 1 of the present invention: including steering hydraulic cylinder (11), accumulator (12), controller (9), steering wheel (8), AC motor (4), DC/AC converter (3), battery ( 2), quantitative pump (6), oil tank (1), proportional valve (13), on-off valve (16), check valve (7), speed sensor (5), pressure sensor (14), pressure sensor (15 ), overflow valve (17), three-position four-way reversing valve (10). The connection method is: the battery (2) drives the AC motor (4), the AC motor (4) drives the quantitative pump (6), and the outlet of the quantitative pump (6) passes through the one-way valve (7) and the three-position four-way reversing valve (10 ), the outlet of the three-position four-way reversing valve (10) is connected to the steering hydraulic cylinder (11); the outlet of the accumulator (12) is connected to the proportional valve (13), and the outlet of the proportional valve (13) is connected to the three-position four-way One end of the overflow valve (17) is connected to the outlet of the quantitative pump (6), and the other end is connected to the fuel tank (1); one end of the on-off valve (16) is connected to the outlet of the quantitative pump (6), and the other end is connected to the into the fuel tank (1). The rotational speed sensor (5) measures the rotational speed of the AC motor (4); the pressure sensor (14) measures the outlet pressure of the accumulator (12), and the pressure sensor (15) measures the inlet pressure of the three-position four-way valve. The output signals of the pressure sensor (14), pressure sensor (15) and speed sensor (5) are sent to the controller (9), and the controller (9) controls the battery (2), proportional valve (13), on-off valve (16 ), three-position four-way reversing valve (10). Among them, the AC motor (4) can be a synchronous AC motor or an asynchronous AC motor; the three-position four-way reversing valve (10), the proportional valve (13), and the on-off valve (16) can use solenoid valves for small flow systems, and for large flow systems. Flow system can adopt electro-hydraulic valve.

The difference between technical solution 2 and technical solution 1 of the present invention is that a fuel cell (19) and a DC/DC converter (18) are added; the output power of the fuel cell (19) is stored in the DC/DC converter (18) In the battery (2), the battery (2) drives the AC motor (4) through the DC/AC converter (3); the fuel cell (19) only drives the AC motor (4) of the steering system, and the energy requirements of other parts of the loader Provided by the internal combustion engine of the loader, this driving mode can reduce the power requirement of the fuel cell (19).

When the loader turns, the accumulator (12) supplies oil to the steering hydraulic cylinder (11) alone, and at the same time opens the on-off valve (16) to start the AC motor without load. When the rotation speed of the AC motor (4) reaches the required value, After the switch, the quantitative pump (6) is driven by the AC motor (4) to supply oil to the steering hydraulic cylinder (11) alone. After the steering is completed, the three-position four-way reversing valve (10) is closed. When the pressure in the accumulator (12) is low, the on-off valve (16) is closed, the proportional valve (13) is opened, and the AC motor (4) continues Drive the quantitative pump (6) to rotate, and fill the accumulator (12) with high-pressure oil. During the filling of the accumulator (12), if the loader needs to turn, close the proportional valve (13) and open the three-position The four-way reversing valve (10), the AC motor (4) drives the quantitative pump (6) to supply oil to the steering hydraulic cylinder (11); when the pressure in the accumulator (12) is high, the on-off valve (16) is opened , close the proportional valve (13), and stop the power supply to the AC motor (4), and the AC motor (4) brakes. If the movement range of the steering wheel (8) is not large, that is, the steering wheel (8) stops before the rotation speed of the AC motor (4) reaches the required value, then the pressure of the accumulator (12) is detected immediately after the steering wheel (8) stops moving; If the pressure of the accumulator (12) is high, the AC motor (4) will be braked; if the pressure in the accumulator is low, the AC motor (4) will continue to be powered, and the AC motor (4) will drive the fixed pump (6) The accumulator (12) is filled with oil.

The beneficial effects of the patent of the present invention are: 1. High efficiency. When the loader does not turn and the pressure in the accumulator is high, the AC motor does not work, and the energy consumption is reduced due to idling; when the loader turns, the AC motor is adjusted according to the speed of the turn. The speed of the motor can be adjusted to realize the on-demand oil supply to the steering hydraulic cylinder and reduce the throttling loss. 2. The starting performance of the AC motor is low. Since the accumulator supplies oil to the hydraulic cylinder at the initial stage of steering, the AC motor starts under no-load conditions, so the AC motor is not required to have high starting performance.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a system diagram of technical solution 1 of the present invention.

Fig. 2 is a system diagram of the second technical solution of the present invention.

Fig. 3 is a main execution flow chart of technical solution 1 of the present invention.

In Figure 1: 1. Fuel tank, 2. Battery, 3. DC/AC converter, 4. AC motor, 5. Speed sensor, 6. Quantitative pump, 7. Check valve, 8. Steering wheel, 9. Controller, 10. Three-position four-way reversing valve, 11. Steering hydraulic cylinder, 12. Accumulator, 13. Proportional valve, 14. Pressure sensor, 15. Pressure sensor, 16. On-off valve, 17. Relief valve; Fig. The dotted line in 1 is the sensor signal.

In Figure 2: 1. Fuel tank, 2. Battery, 3. DC/AC converter, 4. AC motor, 5. Speed sensor, 6. Quantitative pump, 7. Check valve, 8. Steering wheel, 9. Controller, 10. Three-position four-way reversing valve, 11. Steering hydraulic cylinder, 12. Accumulator, 13. Proportional valve, 14. Pressure sensor, 15. Pressure sensor, 16. On-off valve, 17. Relief valve, 18 .DC/DC converter, 19. Fuel cell; The dotted line in Fig. 2 is the sensor signal.

Detailed ways

Specific implementation of technical solution 1 of the present invention: when the loader is started, the pressure sensor (14) transmits the pressure signal of the accumulator (12) to the controller (9), and the controller (9) determines that the accumulator ( 12) Whether the pressure meets the requirements. When the pressure in the accumulator (12) is low, the controller (9) controls the AC motor (4) to start, and controls the proportional valve (13) to open, and the three-position four-way reversing valve (10) and the on-off valve (16) are closed, at this time, the quantitative pump (6) is driven by the AC motor (4) to fill the accumulator (12) with high-pressure oil; when the pressure of the accumulator (12) is higher When it is high, the loader can start normal operation. The highest pressure in the accumulator (12) is the overflow pressure of the overflow valve (17), and the lowest pressure should be greater than the average pressure of the steering hydraulic cylinder (11) when the loader is turning normally, and the average pressure of the steering hydraulic cylinder (11) when turning normally can be determined experimentally.

When the loader needs to turn, the accumulator (12) supplies oil to the steering hydraulic cylinder (11) at the beginning of the turn, that is, before the rotation speed of the AC motor (4) reaches the set speed. (4) After the speed reaches the set speed, the AC motor (4) drives the quantitative pump (6) to supply oil to the steering hydraulic cylinder (11); the set speed of the AC motor (4) is determined by the action speed of the steering wheel (8). Proportional; the main advantages of this oil supply method are: 1. The response speed of the accumulator (12) is fast, and the accumulator (12) alone supplies oil to the steering hydraulic cylinder (11) at the initial stage of the steering of the loader, which conforms to The loader requires the steering system to respond quickly. 2. During the steering process, the rotation speed of the AC motor (4) can be adjusted according to the speed of the steering wheel (8), and oil is output to the steering hydraulic cylinder (11) as needed to save energy. The specific process is as follows: When the controller (9) receives the steering signal, it opens the on-off valve (16), starts the AC motor (4), and the oil output from the quantitative pump (6) flows back to the fuel tank through the on-off valve (16) ( 1), the AC motor (4) is equivalent to starting under no load, and the speed rises quickly; at the same time, the proportional valve (13) and the three-position four-way reversing valve (10) are opened, and the accumulator (12) is used to steer independently The hydraulic cylinder (11) supplies oil, and the opening size of the proportional valve (13) is calculated according to the inlet pressure of the three-position four-way valve (9) and the outlet pressure of the accumulator (12), so as to ensure that the pressure in the accumulator (12) The oil will not cause excessive impact on the steering hydraulic cylinder (11) due to the large opening of the proportional valve (13); when the AC motor (4) is started, close the proportional valve (13) and the on-off valve (16) , in turn, the quantitative pump (6) alone supplies oil to the steering hydraulic system.

At the end of steering, close the three-position four-way reversing valve (10), if the pressure in the accumulator (12) is not less than the minimum allowable pressure, open the on-off valve (16), and stop the power supply to the AC motor (4) at the same time, The rotation speed of the AC motor (4) decreases gradually to realize the braking of the AC motor (4); if the pressure in the accumulator (12) is lower than the minimum allowable pressure, the on-off valve (16) and the three-position four-way reversing valve (10) closed, the proportional valve (13) is opened, the battery (2) continues to supply power to the AC motor (4), and the AC motor (4) drives the fixed pump (6) to charge the accumulator (12) with high-pressure oil. If the loader needs to steer during oil filling of the device (12), close the proportional valve (13), open the three-position four-way reversing valve (10), and the AC motor (4) drives the quantitative pump (6) to the steering hydraulic cylinder ( 11) Oil supply, if the loader does not need to turn, when the pressure of the accumulator (12) reaches the maximum allowable pressure, close the proportional valve (13), open the on-off valve (16) and stop the AC motor (4) Power supply, AC motor (4) braking.

The following situations may occur in actual operation: the steering wheel (8) has a small range of motion, that is, the steering wheel (8) stops before the rotation speed of the AC motor (4) reaches the required value, and the three-position four through the reversing valve (10) and detect the pressure of the accumulator (12); if the pressure of the accumulator (12) is high, the AC motor (4) will be braked; if the pressure in the accumulator is low, it will continue to The AC motor (4) supplies power, and the AC motor (4) drives the quantitative pump (6) to charge the accumulator (12). same discussion.

When the loader does not turn and the pressure of the accumulator (12) is not less than the allowable minimum pressure, the AC motor (4) does not work. The main execution flow of technical solution 1 is shown in FIG. 3 .

The specific implementation of the technical solution 2 of the present invention: the difference between the technical solution 2 and the technical solution 1 lies in the power source part; in the technical solution 2, a fuel cell (19) and a DC/DC converter (18) are added; the fuel cell ( 19) The output electric energy is stored in the battery (2) through the DC/DC converter (18), and the battery (2) drives the AC motor (4) through the DC/AC converter (3); the fuel cell (19) only drives the The AC motor (4) of the steering system and other part of the energy demand of the loader are provided by the internal combustion engine of the loader; the fuel cell system can further improve the system efficiency, and the power requirement of the fuel cell (19) is not high.

Since the combination of the AC motor (4) and the quantitative pump (6) can output hydraulic oil according to the oil demand of the steering hydraulic cylinder (11), the three-position four-way reversing valve (10) only acts as a reversing function and does not Adjust the flow effect. One of the ideal performances that the loader steering hydraulic system needs to achieve is: when the loader turns and the pressure in the steering hydraulic cylinder (11) changes, the flow entering the steering hydraulic cylinder (11) is not affected by the pressure of the steering hydraulic cylinder (11). Influenced by fluctuations, only the rotation speed of the steering wheel (8) is proportional, that is, the flow entering the steering hydraulic cylinder (11) has strong robustness to the fluctuation of the steering load; in the patent of the present invention, in order to achieve this performance as much as possible, it can be controlled according to the vector The method is to adjust the speed of the AC motor (4) to improve the robustness of the steering hydraulic system.

Claims (5)

1. A loader frequency conversion pump control steering hydraulic system, including steering hydraulic cylinder, accumulator, controller, steering wheel, AC motor, battery, DC/AC converter, DC/DC converter, fuel cell, quantitative pump, Oil tank, proportional valve, on-off valve, one-way valve, speed sensor, pressure sensor, relief valve, three-position four-way reversing valve; AC motor drives the quantitative pump; the outlet of the quantitative pump is switched to the three-position four-way through the one-way valve The outlet of the three-position four-way reversing valve is connected to the steering hydraulic cylinder; the outlet of the accumulator is connected to the oil inlet of the three-position four-way reversing valve through the proportional valve; one end of the overflow valve is connected to the quantitative pump, and the other end is connected to the fuel tank Connection; one end of the on-off valve is connected to the quantitative pump, and the other end is connected to the fuel tank; the speed sensor transmits the AC motor speed signal to the controller; the pressure sensor transmits the outlet pressure of the accumulator and the inlet pressure of the three-position four-way reversing valve to the controller The controller controls the proportional valve, the three-position four-way reversing valve, and the on-off valve; the frequency conversion pump control steering hydraulic system of the loader is characterized in that: in the initial stage of the loader steering, the AC motor speed does not reach the set Before the speed is high, the accumulator supplies oil to the steering hydraulic cylinder alone, and after the AC motor reaches the set speed, it is switched to the AC motor to supply oil to the steering hydraulic cylinder alone, and the set speed of the AC motor is set by the controller according to the speed of the steering wheel. ; After the loader turns, if the pressure of the accumulator is lower than the set minimum pressure, the AC motor will continue to drive the fixed pump to charge the accumulator. If the pressure of the accumulator is not lower than the set pressure, the AC motor will brake , if the loader is turning during the charging of the accumulator, stop charging the accumulator, and the AC motor drives the fixed pump to supply oil to the steering hydraulic cylinder; if the steering process is over before the AC motor reaches the set speed , then judge whether it is necessary to fill the accumulator with oil immediately after the steering is completed; the three-position four-way reversing valve only plays the role of reversing, and does not play the role of adjusting the flow; the controller according to the three-position four-way reversing valve The opening of the proportional valve is adjusted by the outlet pressure of the energy generator; for the power source part, for ordinary loaders, the AC motor is driven by the battery alone, or the AC motor is driven by a hybrid power source composed of a fuel cell and a battery. 2. The variable frequency pump-controlled steering hydraulic system of the loader according to claim 1, wherein the controller adjusts the rotation speed of the AC motor according to the speed of the steering wheel, and the set speed of the AC motor is proportional to the speed of the steering wheel. 3. The variable frequency pump control steering hydraulic system of the loader according to claim 1, characterized in that: the AC motor is started at the moment when the loader turns, and the on-off valve is opened before the rotation speed of the AC motor reaches the set speed, so that The AC motor is started without load, and the proportional valve is opened at the same time, so that the accumulator supplies oil to the steering hydraulic cylinder alone; after the AC motor reaches the set speed, the on-off valve and the proportional valve are closed, and the AC motor supplies oil to the steering hydraulic cylinder alone; After the steering is completed, close the three-position four-way reversing valve; if the pressure in the accumulator is lower than the set minimum pressure, the on-off valve is closed, the proportional valve is opened, and the AC motor drives the quantitative pump to charge the accumulator with high-pressure oil. , during the charging of the accumulator, if the loader needs to turn, close the proportional valve and the on-off valve, open the three-position four-way reversing valve, and the AC motor drives the quantitative pump to supply oil to the steering hydraulic cylinder; if the accumulator If the internal pressure is not lower than the set minimum pressure, the power supply to the AC motor will be stopped, the on-off valve will be opened, the three-position four-way reversing valve and the proportional valve will be closed, and the AC motor will brake; the set maximum pressure of the accumulator is overflow Valve overflow pressure, the minimum setting pressure of the accumulator is greater than the average pressure of the steering hydraulic cylinder when the loader is turning normally, and the average pressure of the steering hydraulic cylinder when the loader is turning normally is measured by experiment. 4. The variable frequency pump control steering hydraulic system of the loader according to claim 1, characterized in that: the AC motor is started at the moment when the loader turns, and if the steering process is over before the AC motor reaches the set speed, it is turned off Three-position four-way reversing valve; if the pressure in the accumulator is lower than the set minimum pressure, the on-off valve will be closed, the proportional valve will be opened, and the AC motor will continue to drive the quantitative pump to charge the accumulator. During oiling, if the loader needs to turn, close the proportional valve and the on-off valve, open the three-position four-way reversing valve, and the AC motor drives the quantitative pump to supply oil to the steering hydraulic cylinder; if the pressure in the accumulator is not lower than the set The lowest pressure stops power supply to the AC motor, opens the on-off valve, closes the three-position four-way reversing valve and the proportional valve, and the AC motor brakes. 5. The frequency conversion pump control steering hydraulic system of the loader according to claim 1, characterized in that: the output electric energy of the fuel cell is stored in the storage battery through the DC/DC converter, and the storage battery drives the AC motor through the DC/AC converter; The battery only drives the AC motor of the steering hydraulic system, and the loader's internal combustion engine provides the rest of the energy requirements of the loader.