An electrically controlled hydraulic steering system and a crane

Abstract

The application provides an electric control hydraulic steering system and a crane, wherein the oil pressure applied to both ends of a proportional valve spool is changed by changing the current of a hydraulic proportional pilot control proportional valve coil, and the proportional valve spool is driven to move by the oil pressure; the response characteristics of the system are improved, the response time is reduced, and the reliability of the feedback is improved by parallel connection of the two feedback modes of post-valve feedback and post-pump feedback; the displacement of the proportional valve spool is monitored by adding a displacement sensor in the proportional valve, the flow of the proportional valve is controlled by controlling the position of the proportional valve spool, the control precision of the proportional valve is higher, and the proportional valve control method can adopt spool displacement feedback control or coil current feedback control, so that different application occasions can be coped with.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of engineering machinery, and particularly relates to an electrically-controlled hydraulic steering system and a crane. BACKGROUND

[0002] In order to increase the off-road performance of the whole vehicle, the all-terrain crane needs to realize all-wheel steering and multiple steering modes (for example, highway driving mode, crab mode, etc.). However, the ordinary mechanical pull rod is difficult to meet the above requirements, and therefore the mechanical steering system is evolved, in which the front several vehicle bridges are driven by the pull rod to steer by the steering wheel, and the rear several vehicle bridges are steered by the electro-hydraulic control mode according to the mechanical bridge turning angle. All the vehicle bridges and related components that steer by the electro-hydraulic control mode are collectively referred to as the electrically-controlled hydraulic steering system. Figure 1 The existing steering system is shown by Figure 1 It can be known that the crane rear bridge realizes wheel steering by the electrically-controlled hydraulic steering system. The electrically-controlled hydraulic steering system generally changes the flow of the proportional valve by changing the current of the electromagnetic coil of the proportional valve, and then controls the wheel to steer according to the pre-set turning angle relationship. The proportional valve has two electromagnetic coils, which control the flow of left turning and right turning respectively. The electromagnetic coil changes the position of the proportional valve spool by electromagnetic force to realize the change of the flow. The change of the electromagnetic coil current value is realized by changing the duty ratio of the control voltage of the proportional valve.

[0003] The electrically-controlled steering system of the rear bridge has a load-sensitive system and a constant-pressure variable system. The constant-pressure variable system is that the system always maintains the rated pressure of the system, and the load-sensitive system is that the system pressure can be adjusted in real time according to the steering resistance. The advantage of the load-sensitive system is that the system pressure is adjusted in real time according to the load, which reduces the engine load, saves energy, and reduces the heat dissipation demand of the hydraulic system. However, due to the time required to establish the pressure, the response of the electrically-controlled steering bridge is slower than that of the constant-pressure variable system. In fact, at present, due to the large number of vehicle bridges and long pipelines of the all-terrain crane, whether the constant-pressure variable system or the load-sensitive system is used, there is a problem of slow steering response.

[0004] The factors affecting the steering response include:

[0005] (1) The valve response of the current electrically-controlled steering system of the rear bridge has a lag, which includes the lag of the valve movement response, and the lag caused by the pressure fluctuation and flow fluctuation of the hydraulic system;

[0006] (2) The control of the existing electrically-controlled steering system of the rear bridge is to directly drive the displacement of the main valve core by the electromagnetic valve. The accuracy of the movement is fed back by the angle sensor installed on the vehicle bridge, and then adjusted according to the feedback information. This closed-loop control process affects the system response speed;

[0007] (3) Load sensing system due to feedback is through the load of each axle feedback to the load sensing pump, the load sensing pump itself in response to the system pressure to rise, the process feedback route is long, the response of the electronic control system and the load sensing system advantage play;

[0008] (4) Load sensing steering system generally uses valve feedback, hydraulic valve group is generally far from the steering pump, the feedback time is longer, the system response is slower.

[0009] And the proportional valve spool structure in the existing rear axle electric control steering system is complex, the current of the electromagnetic coil and the position of the proportional valve spool are uncertain in the working process of the proportional valve due to factors such as proportional valve spool inertia and hydraulic pressure change, it is difficult to judge whether the specific position of the proportional valve spool is in the appropriate position, and it is also difficult to know whether the proportional valve spool is stuck. At the same time, the coil will heat up during work, causing the resistance of the coil to change, and the same voltage control duty cycle will result in different current values of the coil. Due to the above reasons, the control precision of the proportional valve is not high, and different control effects will appear under the same control parameters. When the proportional valve fails, it is difficult to determine the specific position and movement of the proportional valve spool, and it is difficult to troubleshoot.

[0010] And the electromagnetic force generated by the electromagnetic coil in the existing rear axle electric control steering system is small, which may not be enough to move the proportional valve spool when the friction of the proportional valve spool is large, resulting in proportional valve sticking. SUMMARY

[0011] The purpose of the application is to solve the problem of slow response of the existing rear axle electric control steering system, and to solve the problems of low control precision, difficult troubleshooting and proportional valve sticking in the existing rear axle electric control steering system. The application provides an electric control hydraulic steering system and a crane to improve the response speed.

[0012] Technical scheme: An electric control hydraulic steering system, comprising: a controller, a proportional valve, a first steering axle, a second steering axle and a valve feedback loop;

[0013] The proportional valve is connected with the first steering axle and the second steering axle, and is used to control the turning angle of the first steering axle and the turning angle of the second steering axle; a first turning angle sensor is installed on the first steering axle, and a second turning angle sensor is installed on the second steering axle; the first turning angle sensor and the second turning angle sensor are electrically connected with the controller, and are used to provide real-time turning angle information of the first steering axle and the second steering axle to the controller;

[0014] The proportional valve comprises a first steering linkage mechanism for controlling the first steering axle, a second steering linkage mechanism for controlling the second steering axle, and a feedback port;

[0015] The first steering linkage and the second steering linkage are identical in structure, and each comprises a proportional valve core, a valve core displacement sensor, a hydraulic proportional pilot valve A and a hydraulic proportional pilot valve B; an oil outlet of an oil supply circuit is connected with an oil inlet of the hydraulic proportional pilot valve A and an oil inlet of the hydraulic proportional pilot valve B; when the pressure of the oil inlets of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B is lower than an oil inlet setting value, the oil supply circuit supplies oil to the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B; when the pressure of the oil inlets of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B reaches an oil stop setting value, the oil supply circuit stops supplying oil to the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B;

[0016] For any one of the steering linkages, the controller changes the oil pressure applied to both ends of the proportional valve core by changing the coil current of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B, and uses the oil pressure to drive the proportional valve core to move, so that the proportional valve controls the steering of the first steering axle or / and the second steering axle;

[0017] The valve core displacement sensor is electrically connected with the controller, and is configured to provide real-time displacement information of the proportional valve core to the controller;

[0018] The post-valve feedback circuit is connected with the feedback port of the proportional valve;

[0019] The controller calculates a theoretical displacement of the proportional valve core according to real-time turning angle information of the first steering axle and the second steering axle, and a theoretical turning angle of the first steering axle and the second steering axle corresponding to a current driving state of the crane; compares the theoretical displacement of the proportional valve core with a real-time displacement of the proportional valve core, calculates a theoretical current of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B, and calculates a control duty cycle of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B based on the theoretical current of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B.

[0020] Further, the post-valve feedback circuit comprises a first shuttle valve and a steering plunger pump; the feedback port of the proportional valve is communicated with the feedback port of the steering plunger pump through the first shuttle valve.

[0021] Further, for the constant-pressure variable hydraulic steering system, the steering plunger pump in the post-valve feedback circuit is a constant-pressure variable pump.

[0022] Further, for the load-sensitive electrically-controlled hydraulic steering system, a post-pump feedback circuit is further included; the post-pump feedback circuit comprises a damping hole;

[0023] The outlet of the damping hole is communicated with the feedback port of the steering plunger pump through the first shuttle valve;

[0024] The first shuttle valve feeds back the higher pressure between the feedback port pressure of the proportional valve and the outlet pressure of the damping hole to the feedback port of the steering plunger pump.

[0025] Further, for the constant pressure variable electric hydraulic steering system, the steering plunger pump in the post-valve feedback loop is a load-sensitive pump.

[0026] Further, the oil supply circuit comprises an internal pressure control valve; the oil inlet of the internal pressure control valve is communicated with the P port of the proportional valve, the P port of the proportional valve is connected with the steering plunger pump through the damping hole; the oil outlet of the internal pressure control valve is connected with the oil inlets of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B.

[0027] Further, the oil supply circuit further comprises an overflow valve, the oil inlet of the overflow valve is connected with the oil outlet of the internal pressure control valve, the oil outlet of the overflow valve is communicated with the T port of the proportional valve, and the oil inlets of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B are communicated with the oil inlet of the overflow valve.

[0028] Further, when the controller cannot obtain the real-time displacement of the proportional valve core, it is determined that the valve core displacement sensor is damaged, the controller controls the rotation angle of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B based on the relationship between the electromagnetic coil current and the flow of the hydraulic proportional pilot valve, and an alarm signal is given.

[0029] Further, when the controller finds that there is a theoretical pressure difference between the two ends of the proportional valve core, and when the difference between the position of the proportional valve core and the theoretical position exceeds the design threshold, it is determined that the valve core is stuck, and the controller gives an alarm signal.

[0030] The application further discloses a crane, which comprises a crane body and a steering system for steering control of the crane body, and the steering system is any one of the electric hydraulic steering systems disclosed above.

[0031] Advantages: compared with the prior art, the application has the following advantages:

[0032] (1) The present application adopts hydraulic proportional pilot control for both ends of each proportional valve spool, changes the oil pressure applied to both ends of the proportional valve spool by changing the current of the proportional valve coil of the hydraulic proportional pilot control, and moves the proportional valve spool by the oil pressure; the present application controls the small valve spool by the electromagnetic coil and moves the large valve spool by the hydraulic oil, and a small filter can be arranged in front of the small valve spool to further filter the high-precision valve spool, because the valve spool has high precision, re-filtering the oil can reduce the probability of the pilot valve spool being stuck, and the electromagnetic valve has small thrust and is sensitive to impurities; since the hydraulic oil can generate a thrust much larger than the electromagnetic coil, it can overcome the friction of the valve spool and effectively alleviate the occurrence of valve spool sticking, thereby reducing the failure rate of the valve spool sticking of the engineering vehicle;

[0033] (2) The A port and the B port of each proportional valve spool are communicated with the LS port in the power-off state, the LS ports of the two associated proportional valves are communicated with the second shuttle valve, the pressure of the LS port is fed back to the feedback port of the steering plunger pump through the second shuttle valve, thereby forming a post-valve feedback function; in the load-sensitive system, the outlet pressure of the one-way damping valve is fed back to the feedback port of the steering plunger pump through the second shuttle valve, thereby forming a post-pump feedback; the present application uses the post-valve feedback and the post-pump feedback in parallel, thereby increasing the response characteristics of the system, reducing the response time, and improving the reliability of the feedback;

[0034] (3) The present application monitors the displacement of the proportional valve spool by adding a displacement sensor in the proportional valve, controls the flow of the proportional valve by controlling the position of the proportional valve spool, makes the control accuracy of the proportional valve higher, and avoids the problem that the control current-flow characteristic changes with the environment and causes poor control accuracy of the proportional valve; the present application can judge whether the proportional valve spool is stuck by the displacement signal of the valve spool, thereby effectively reducing the maintenance difficulty; at the same time, when the displacement sensor is damaged or the like, the current feedback control can be directly switched, the position of the valve spool is changed by directly changing the coil current of the hydraulic proportional pilot control valve, and since the current of the electromagnetic coil can be monitored, the electromagnetic coil current feedback control is realized at this time, so that the proportional valve control method can use the valve spool displacement feedback control or the coil current feedback control, and can be applied to different occasions. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a schematic diagram of the existing steering system;

[0036] Figure 2 is a schematic diagram of a steering system according to embodiment 1;

[0037] Figure 3 is a structural schematic diagram of the proportional valve of the present application. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application is further illustrated below in combination with the drawings and examples.

[0039] As shown in the drawings, Figure 1 The present embodiment proposes a steering system, which mainly comprises a front axle mechanical steering system, a rear axle electrically-controlled hydraulic steering system and a controller 6.

[0040] As shown in the drawings, Figure 2 The front axle mechanical steering system of the present embodiment is composed of an oil tank, an oil source, a steering wheel 7, a hydraulic power steering gear 8 and a front axle 10. In the steering process, the rotation of the steering wheel 7 drives the valve core of the hydraulic power steering gear 8 to move and then provides power to the large and small cavities of the steering oil cylinder on the front axle 10, thereby pushing the front axle to steer. The rear axle electrically-controlled hydraulic steering system of the present embodiment is composed of a variable pump oil source, an oil tank, a proportional valve 5, a first steering axle 1 and a second steering axle 3, and the proportional valve 5 controls the first steering axle 1 and the second steering axle 3. The oil source of the variable pump comes from the oil tank, which is responsible for supplying oil to the entire rear axle electrically-controlled hydraulic steering system and collecting the return oil of the rear axle electrically-controlled hydraulic steering system. The oil tank is internally provided with a return oil filter and an oil pump oil filter, and the oil tank is connected with the T port (valve group return oil port) of the proportional valve 5 in the oil tank and the oil inlet of the oil pump. Figure 2

[0041] The front axle 10, the first steering axle 1 and the second steering axle 3 are correspondingly provided with a front axle angle sensor 9, a first angle sensor 2 and a second angle sensor 4. The front axle angle sensor 9, the first angle sensor 2 and the second angle sensor 4 are electrically connected with the controller 6, and are used to provide the real-time angle information of the front axle, the real-time angle information of the first steering axle 1 and the real-time angle information of the second steering axle 3 to the controller 6.

[0042] The proportional valve 5 of the present embodiment has an A1 port, a B1 port, an A2 port, a B2 port, a feedback port LS, a P port and a T port. The A1 port and the B1 port of the proportional valve 5 correspond to the A port and the B port of the first proportional valve core in the proportional valve 5, and the A2 port and the B2 port of the proportional valve 5 correspond to the A port and the B port of the second proportional valve core in the proportional valve 5. The P port is used to provide high-pressure oil, which is connected with the outlet of the steering plunger pump 16 through a damping hole 17, and the T port is connected with the oil tank. The hydraulic oil needs to flow for the hydraulic system to work. There is a damping hole 17 between the P port and the outlet of the steering plunger pump 16.

[0043] ​The feedback port LS of the proportional valve 5 is communicated with the P2 port of the first shuttle valve 18, and the A port of the first shuttle valve 18 is communicated with the feedback port X of the steering plunger pump 16; the pressure of the feedback port LS of the proportional valve 5 is fed back to the feedback port X of the steering plunger pump 16 through the shuttle valve 18, thereby forming a post-valve feedback function. In the load sensing system, the outlet of the damping hole 17 is communicated with the P1 port of the first shuttle valve 18, and the pressure of the damping hole 17 is fed back to the feedback port X of the steering plunger pump 16 through the first shuttle valve 18, thereby forming a post-pump feedback; in the embodiment, the post-valve feedback and the post-pump feedback are used in parallel, and the pressure of the higher one is fed back to the feedback port X of the steering plunger pump 16 by the first shuttle valve 18, thereby increasing the reliability and timeliness of the oil path feedback, and meanwhile, the response characteristics of the system are increased, the response time is reduced, and the reliability of the feedback is improved. In the load sensing system, the steering plunger pump 16 is a load sensing pump; for the constant pressure variable system, the steering plunger pump 16 is a constant pressure variable pump, and the feedback loop formed by the first shuttle valve 18 is cancelled, that is, the feedback port LS of the proportional valve 5 is communicated with the steering plunger pump 16.

[0044] Referring to Figure 3 The steering linkage of the second steering axle 3 controlled by the proportional valve 5 is composed of a first pressure compensation block 51, a second pressure compensation block 511, a first proportional spool 52, a first spool displacement sensor 581, a first hydraulic proportional pilot valve 572 and a second hydraulic proportional pilot valve 573. The steering linkage of the first steering axle 1 controlled by the proportional valve 5 is composed of a third pressure compensation block 512, a fourth pressure compensation block 513, a second proportional spool 521, a second spool displacement sensor 58, a third hydraulic proportional pilot valve 57 and a fourth hydraulic proportional pilot valve 571. The multiple pressure compensation blocks mentioned above have the function of ensuring that the pressure difference before and after the proportional valve is constant, so that the flow of the valve is only related to the opening of the valve, thereby avoiding the flow fluctuation caused by the pressure fluctuation. The pressure compensation block has three interfaces, the first interface is connected with the output port of the proportional spool, the second interface is connected with the A port or the B port of the proportional spool, and the third interface is connected with the second shuttle valve 60. The second shuttle valve 60 is a combination of two check valves, which can compare the pressure of two oil ports, and the check valve on the side with high pressure is opened, and the check valve on the side with low pressure is closed, thereby avoiding the influence of the high pressure side on the low pressure side, and the high oil pressure is continuously conducted.

[0045] In the present embodiment, the first hydraulic proportional pilot valve 572, the second hydraulic proportional pilot valve 573, the third hydraulic proportional pilot valve 57, and the fourth hydraulic proportional pilot valve 571 of the proportional valve 5 are supplied with oil by an oil supply circuit composed of an internal pressure control valve 59 and a relief valve 541. The specific connection is that the oil inlet of the internal pressure control valve 59 is communicated with the P port of the proportional valve 5 through a pipeline; the oil outlet of the internal pressure control valve 59 is connected with the oil inlets of the first hydraulic proportional pilot valve 572, the second hydraulic proportional pilot valve 573, the third hydraulic proportional pilot valve 57, and the fourth hydraulic proportional pilot valve 571, and the oil outlet of the internal pressure control valve 59 is also connected with the oil inlet of the relief valve 541.

[0046] The controller changes the oil pressure applied to both ends of the first proportional spool 52 by changing the electromagnetic coil current of the first hydraulic proportional pilot valve 572 and the second hydraulic proportional pilot valve 573, and the first proportional spool 52 is pushed to move by the oil pressure; similarly, the oil pressure applied to both ends of the second proportional spool 521 is changed by changing the coil current of the third hydraulic proportional pilot valve 57 and the fourth hydraulic proportional pilot valve 571, and the second proportional spool 521 is pushed to move by the oil pressure. Since the hydraulic oil can generate a much larger thrust than the electromagnetic coil, it is enough to overcome the friction of the spool, and the occurrence of the spool sticking phenomenon can be effectively alleviated.

[0047] The oil inlets of the first hydraulic proportional pilot valve 572, the second hydraulic proportional pilot valve 573, the third hydraulic proportional pilot valve 57, and the fourth hydraulic proportional pilot valve 571 are the same, and as long as one pilot valve works, the oil pressure will be reduced. When the oil inlet pressure of the first hydraulic proportional pilot valve 572, the second hydraulic proportional pilot valve 573, the third hydraulic proportional pilot valve 57, and the fourth hydraulic proportional pilot valve 571 is low, the internal pressure control valve 59 is turned on, and at this time the P port of the proportional valve 5 is communicated with the oil inlets of the first hydraulic proportional pilot valve 572, the second hydraulic proportional pilot valve 573, the third hydraulic proportional pilot valve 57, and the fourth hydraulic proportional pilot valve 571, so that the oil inlet pressure of each hydraulic proportional pilot valve is increased.

[0048] The inlet oil ports of the first hydraulic proportional pilot valve 572, the second hydraulic proportional pilot valve 573, the third hydraulic proportional pilot valve 57 and the fourth hydraulic proportional pilot valve 571 are the same, and the inlet oil port pressures are the same, so that the flow control of each pilot valve is only proportional to the opening of the pilot valve core / current of the pilot valve. When the inlet oil port pressure of the pilot valve reaches a limit, the pilot inlet oil port does not need to be supplied with oil. That is, when the inlet oil port pressure of the first hydraulic proportional pilot valve 572, the second hydraulic proportional pilot valve 573, the third hydraulic proportional pilot valve 57 and the fourth hydraulic proportional pilot valve 571 is higher than the set pressure of the internal pressure control valve 59, at this time, under the action of the high pressure of the inlet oil port of the first hydraulic proportional pilot valve 572, the second hydraulic proportional pilot valve 573, the third hydraulic proportional pilot valve 57 and the fourth hydraulic proportional pilot valve 571, the internal pressure control valve 59 is closed, preventing the inlet oil port pressure of each hydraulic proportional pilot valve from continuing to rise, thereby ensuring that the oil pressure at the inlet oil port of each hydraulic proportional pilot valve is stable.

[0049] The outlet oil port of the overflow valve 541 of the embodiment is communicated with the T port of the proportional valve; at the same time, the inlet oil port of the overflow valve 541 is communicated with the inlet oil ports of the first hydraulic proportional pilot valve 572, the second hydraulic proportional pilot valve 573, the third hydraulic proportional pilot valve 57 and the fourth hydraulic proportional pilot valve 571, and the main function of the overflow valve 541 is to prevent the pressure at the inlet oil ports of the hydraulic proportional pilot valves from being too high.

[0050] The first hydraulic proportional pilot valve 572 controls the a side of the first proportional valve core 52, and the second hydraulic proportional pilot valve 573 controls the b side of the first proportional valve core 52; the third hydraulic proportional pilot valve 57 controls the a side of the second proportional valve core 521, and the fourth hydraulic proportional pilot valve 571 controls the b side of the second proportional valve core 521.

[0051] In the power-off state of the first hydraulic proportional pilot valve 572, the a side of the first proportional valve core 52 is communicated with the T port of the proportional valve, at this time, the a side of the first proportional valve core 52 has no pressure, and at this time, the first proportional valve core 52 cannot move to the b side; the a side of the proportional valve core is either communicated with the oil source to push the valve core to move, or communicated with the return oil circuit to return the excess hydraulic oil to the hydraulic oil tank. When the first hydraulic proportional pilot valve 572 is powered on, the a side of the first proportional valve core 52 is communicated with the inlet oil port of the first proportional valve core 52, at this time, the a side of the first proportional valve core 52 will generate a certain pressure, the greater the current of the electromagnetic coil of the first hydraulic proportional pilot valve 572, the greater the pressure of the a side of the first proportional valve core 52 at this time, at this time, the first proportional valve core 52 moves to the b side, at this time, the P port is communicated with the A1 port through the first proportional valve core 52 and the second pressure compensation block 511, at this time, the A1 port generates high pressure, and at the same time, the T port is communicated with the B1 port through the first proportional valve core 52, at this time, the B1 port has lower pressure.

[0052] Similarly, in the second hydraulic proportional pilot valve 573 power-off state, the b side of the first proportional spool 52 communicates with the T port of the proportional valve, at this time the b side of the first proportional spool 52 has no pressure, at this time the first proportional spool 52 cannot move to the a side; When the second hydraulic proportional pilot valve 573 is powered on, the b side of the first proportional spool 52 communicates with the oil inlet of the first proportional spool, at this time the b side of the first proportional spool 52 will generate a certain pressure, the greater the current of the electromagnetic coil of the second hydraulic proportional pilot valve 573, the greater the pressure on the b side of the first proportional spool 52, at this time the first proportional spool 52 moves to the a side, at this time the P port communicates with the B1 port through the first proportional spool 52 and the first pressure compensation block 51, at this time the B1 port generates high pressure, at the same time the T port communicates with the A1 port through the first proportional spool 52, at this time the A1 port has lower pressure.

[0053] The first valve core displacement sensor 581 and the second valve core displacement sensor 58 are electrically connected with the controller 6, for providing the displacement signals of the first proportional spool 52 and the second proportional spool 521 to the controller 6; The embodiment increases displacement sensors in the proportional valve 5 for monitoring the displacement of the valve core, one purpose of monitoring displacement is to calibrate the relationship between valve core displacement and flow in advance, to accurately control the proportional valve flow by controlling the position of the valve core, so that the control accuracy of the proportional valve is higher.

[0054] The controller 6 calculates the theoretical rotation angle of the first steering axle 1 and the second steering axle 3 through the signals of the front axle rotation angle sensor 9 and the all-terrain crane running state signal. Multi-wheel steering needs to satisfy that the vertical lines of each wheel intersect at one point, so that the wheels are pure rolling, otherwise abnormal tire wear will be caused. This theory is the Ackermann theorem. Through this theorem, the theoretical rotation angle of the rear axle is determined after the rotation angle of the front axle tire is determined. The controller 6 calculates the theoretical displacement of the first proportional valve core 52 and the second proportional valve core 521 of the proportional valve 5 through the signals of the first rotation angle sensor 2 and the second rotation angle sensor 4. According to the Ackermann theorem, the required rotation angle can be calculated according to the difference between the theoretical rotation angle and the actual rotation angle of each steering axle. The stroke of the assist cylinder and the required oil supply can be calculated according to the rotation angle, and the oil supply can be obtained by integrating the opening size and opening time of the valve. The opening size of the valve is calibrated in advance according to the valve core displacement sensor. The theoretical current of the electromagnetic coil of the first hydraulic proportional pilot valve 572, the second hydraulic proportional pilot valve 573, the third hydraulic proportional pilot valve 57, and the fourth hydraulic proportional pilot valve 571 is calculated by comparing the displacement signals of the first valve core displacement sensor 581 and the second valve core displacement sensor 58. The valve core needs to displace the distance as soon as possible, and the opening size of the pilot valve required can also be calculated inversely. The flow characteristic of the electric proportional valve refers to the relationship between the current value and the flow rate. Knowing the flow rate can directly give the current value. Traditional control is feedback control, which needs to be tried little by little until the target value is reached. This is the slowest control method. First, give a current, the valve opens, but the target flow rate is not reached, then increase the control current, and so on, until the target flow rate is reached and stopped. From the reflection principle, it can be understood that this feedback control method is slow. According to the theoretical current, the theoretical voltage needs to be calculated according to the resistance and inductance of the electromagnetic coil. The theoretical voltage is proportional to the theoretical duty ratio, and the duty ratio is a type of control signal, i.e. PWM control. The controller changes the duty ratio of the control signal PWM according to the theoretical duty ratio, and the controller controls the first hydraulic proportional pilot valve 572, the second hydraulic proportional pilot valve 573, the third hydraulic proportional pilot valve 57, and the fourth hydraulic proportional pilot valve 571 according to the control duty ratio.

[0055] When the first valve core displacement sensor 581 and the second valve core displacement sensor 58 of the proportional valve 5 are damaged, the controller 6 controls the rotation angle through the relationship between the electromagnetic coil current and the flow rate of the first hydraulic proportional pilot valve 572, the second hydraulic proportional pilot valve 573, the third hydraulic proportional pilot valve 57, and the fourth hydraulic proportional pilot valve 571. Another purpose of adding displacement sensors in the proportional valve 5 in this embodiment is that when damage to the displacement sensor occurs, current feedback control can be directly switched to cope with different application occasions.

Claims

1. An electronically controlled hydraulic steering system, characterized in that: include: Controller, proportional valve, first steering axle, second steering axle and post-valve feedback loop; The proportional valve is connected to the first steering axle and the second steering axle, and is used to control the steering angle of the first steering axle and the steering angle of the second steering axle; a first steering angle sensor is installed on the first steering axle, and a second steering angle sensor is installed on the second steering axle. The first steering angle sensor and the second steering angle sensor are electrically connected to the controller, and are used to provide the controller with real-time steering angle information of the first steering axle and the second steering axle; The proportional valve includes a first steering linkage for controlling the first steering axle, a second steering linkage for controlling the second steering axle, and a feedback port; The first steering linkage and the second steering linkage have the same structure, both comprising: a proportional valve core, a valve core displacement sensor, a hydraulic proportional pilot valve A, and a hydraulic proportional pilot valve B; the oil outlet of the oil supply circuit is connected to the oil inlet of the hydraulic proportional pilot valve A and the oil inlet of the hydraulic proportional pilot valve B; when the pressure of the oil inlet of the hydraulic proportional pilot valve A and the oil inlet of the hydraulic proportional pilot valve B is lower than the oil inlet set value, the oil supply circuit supplies oil to the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B; when the pressure of the oil inlet of the hydraulic proportional pilot valve A and the oil inlet of the hydraulic proportional pilot valve B reaches the oil stop set value, the oil supply circuit stops supplying oil to the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B; For any steering linkage, the controller changes the oil pressure applied to both ends of the proportional valve core by changing the coil current of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B, and uses the oil pressure to push the proportional valve core to move. At this time, the proportional valve controls the steering of the first steering axle and / or the second steering axle; The valve core displacement sensor is electrically connected to the controller and is used to provide the controller with real-time displacement information of the proportional valve core; The post-valve feedback loop is connected to the feedback port of the proportional valve; The controller calculates the theoretical displacement of the proportional valve core based on the real-time rotation angle information of the first steering axle and the second steering axle and the theoretical rotation angles of the first steering axle and the second steering axle corresponding to the current driving state of the crane; compares the theoretical displacement of the proportional valve core with the real-time displacement of the proportional valve core to calculate the theoretical current of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B; and calculates the control duty ratio of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B based on the theoretical current of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B.

2. The electronically controlled hydraulic steering system according to claim 1, characterized in that: The post-valve feedback loop includes: a first shuttle valve and a steering plunger pump; the feedback port of the proportional valve is connected to the feedback port of the steering plunger pump through the first shuttle valve.

3. The electronically controlled hydraulic steering system according to claim 2, characterized in that: For a constant-pressure variable electronically controlled hydraulic steering system, the steering plunger pump in the post-valve feedback loop is a constant-pressure variable pump.

4. The electronically controlled hydraulic steering system according to claim 2, characterized in that: For a load-sensitive electronically controlled hydraulic steering system, it also includes a post-pump feedback loop; the post-pump feedback loop includes a damping orifice; The outlet of the damping hole is connected to the feedback port of the steering plunger pump through the first shuttle valve; The first shuttle valve compares the pressure at the feedback port of the proportional valve and the pressure at the outlet of the damping orifice, and feeds the higher pressure back to the feedback port of the steering piston pump.

5. The electronically controlled hydraulic steering system according to claim 4, characterized in that: For a constant pressure variable electronically controlled hydraulic steering system, the steering plunger pump in the post-valve feedback loop is a load-sensing pump.

6. The electronically controlled hydraulic steering system according to claim 2, characterized in that: The oil supply circuit includes an internal pressure control valve; the oil inlet of the internal pressure control valve is connected to the P port of the proportional valve, and the P port of the proportional valve is connected to the steering plunger pump through a damping hole; the oil outlet of the internal pressure control valve is connected to the oil inlets of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B.

7. The electronically controlled hydraulic steering system according to claim 6, characterized in that: The oil supply circuit also includes a relief valve, the oil inlet of the relief valve is connected to the oil outlet of the internal pressure control valve, the oil outlet of the relief valve is connected to the T port of the proportional valve, and the oil inlet of the relief valve is connected to the oil inlet of the hydraulic proportional pilot valve A and the oil inlet of the hydraulic proportional pilot valve B.

8. The electronically controlled hydraulic steering system according to claim 1, characterized in that: When the controller cannot obtain the real-time displacement of the proportional valve core, it determines that the valve core displacement sensor is damaged. Based on the relationship between the electromagnetic coil current and flow of the hydraulic proportional pilot valve, the controller controls the rotation angle of the hydraulic proportional pilot valve A and the hydraulic proportional pilot valve B, and gives an alarm signal at the same time.

9. The electronically controlled hydraulic steering system according to claim 1, characterized in that: When the controller finds that there is a theoretical pressure difference between the two ends of the proportional valve core, and when the difference between the position of the proportional valve core and the theoretical position exceeds the design threshold, it determines that the valve core is stuck and the controller gives an alarm signal.

10. A crane, characterized in that: It comprises a crane body and a steering system for controlling the steering of the crane body, wherein the steering system is an electronically controlled hydraulic steering system according to any one of claims 1 to 9.

Images