CN114348105B - Rear wheel steering system of heavy truck and control method - Google Patents

Abstract

The invention relates to the technical field of truck steering, in particular to a rear wheel steering system of a heavy truck, which comprises an input unit and a hydraulic steering unit, wherein the input unit and the hydraulic steering unit are electrically connected with a control unit; the control method comprises the following steps: s1, a control unit receives an acquired vehicle speed signal; s2, controlling the rear wheel to be locked in a positive mode when the vehicle speed is more than or equal to 40 km/h; s3, when the vehicle speed is less than 40km/h, starting a control unit; s4, the control unit outputs a signal according to the corner relation between one side of the front wheel and one side of the rear wheel; and S5, comparing the actual turning angle of the rear wheel at the current moment with the turning angle of the rear wheel converted by the ackermann, judging whether the difference value is in a set range, and realizing whether the rear wheel turns. According to the invention, only one side wheel is required to be provided with the electric control hydraulic steering device, the steering of the other side wheel is ensured through the steering trapezoid structure, the rear shaft is connected with the front shaft without a mechanical mechanism, the structure is simple, and the cost is low; the corner of the rear wheel is accurately controlled according to the corner of the front wheel, so that the steering of the rear wheel is accurately controlled, and the abrasion of the rear wheel is reduced.

Description

A heavy truck rear wheel steering system and control method

Technical Field

The present invention relates to the technical field of truck steering, and in particular to a heavy truck rear wheel steering system and a control method.

Background Art

Heavy-duty transport vehicles have long bodies, large wheelbases, and long distances between the rear axle and the front axle, making it difficult to implement traditional mechanical steering mechanisms. In order to save costs, general heavy-duty vehicle manufacturers do not consider implementing rear-wheel steering, resulting in a large turning radius, poor maneuverability, and severe rear wheel wear.

CN104608819A discloses an electronically controlled hydraulic steering system, in which an electronically controlled hydraulic steering device is installed on each wheel to control the steering of the wheel. The electronically controlled hydraulic steering device includes a motor, a reversing valve and a steering hydraulic cylinder. The electronic control unit drives the valve core of the reversing valve to move between a first position and a second position through the motor. The piston of the steering hydraulic cylinder is connected to the valve core. The motor drives the position switching of the valve core of the reversing valve, so that oil enters the rod chamber or the rodless chamber of the steering hydraulic cylinder to control the piston movement of the steering hydraulic cylinder to achieve steering. However, since an electronically controlled hydraulic steering device is installed on each wheel, the cost is high. It is generally suitable for heavy-duty engineering vehicles and slow driving. The safety and stability of the rear axle of micro-steering during high-speed driving are not considered, and it is not suitable for long-distance high-speed driving conditions of heavy-duty transport vehicles.

Summary of the invention

The technical problem to be solved by the present invention is: by maintaining the Ackerman angle relationship between the rear wheels and the front wheels when the heavy transport vehicle is driving, the rear wheels can achieve pure rolling when driving and turning, without eccentric wear, thereby reducing the wear of the rear wheels.

The technical solution adopted by the present invention is: a heavy truck rear wheel steering system comprises: an input unit, a control unit 4 and a hydraulic steering unit, the input unit and the hydraulic steering unit are both electrically connected to the control unit 4;

The input unit includes: a front wheel angle sensor 1, a rear wheel angle sensor 2 and a vehicle speed signal generator 3, and all are connected to a control unit 4;

The control unit 4 controls the operation of the hydraulic steering unit according to the output vehicle speed signal and the front wheel angle signal of the input unit;

The hydraulic steering unit includes: a relief valve 5, an electric pump 6, a throttle valve 7, a first electromagnetic proportional reversing valve 8, a second electromagnetic proportional reversing valve 9 and a hydraulic cylinder 10;

The front wheel angle sensor 1 is fixed on the left side (or right side) of the front axle, and the rear wheel angle sensor is fixed on the left side (or right side) of the rear axle. The front and rear wheel angle sensors are installed on the same side;

When the vehicle starts, the electric pump 6 works continuously to ensure the timely response of the hydraulic steering unit, and the overflow valve 5 and the throttle valve 7 control the flow rate of the hydraulic oil and the pressure of the hydraulic cylinder;

The electric pump 6 is connected to the first electromagnetic proportional reversing valve 8 and the second electromagnetic proportional reversing valve 9 through the overflow valve 5 and the throttle valve 7;

The other ends of the first electromagnetic proportional reversing valve 8 and the second electromagnetic proportional reversing valve 9 are respectively connected to the left hydraulic cylinder and the right hydraulic cylinder of the hydraulic cylinder 10, and the control ends of the first electromagnetic proportional reversing valve 8 and the second electromagnetic proportional reversing valve 9 are both connected to the control unit 4;

The hydraulic cylinder 10 includes a left hydraulic cylinder and a right hydraulic cylinder. One side of the hydraulic cylinder as a whole is connected to the vehicle frame, and the other side is connected to the rear axle steering tie rod.

When the rear wheel needs to turn left, the oil passage enters from the left hydraulic cylinder A1 of the hydraulic cylinder 10 through the first electromagnetic proportional reversing valve 8 and flows out from B1; the oil passage enters from the right hydraulic cylinder A2 through the second electromagnetic proportional reversing valve 9 and flows out from B2, and the hydraulic cylinder retracts as a whole, pulling the steering tie rod of the steering trapezoid back to the right, so that the rear wheel turns left;

When the rear wheel needs to turn right, the oil passage enters from the left hydraulic cylinder B1 of the hydraulic cylinder 10 through the first electromagnetic proportional reversing valve 8 and flows out from A1; the oil passage enters from the right hydraulic cylinder B2 through the second electromagnetic proportional reversing valve 9 and flows out from A2. The hydraulic cylinder extends as a whole, pulling the steering tie rod of the steering trapezoid back to the left, thereby realizing the right turn of the rear wheel.

A control method for a rear wheel steering system of a heavy truck comprises the following steps:

S1, the control unit 4 receives the vehicle speed signal collected by the vehicle speed signal generator 3, and determines whether the control unit 4 needs to be started;

S2, when the vehicle speed is ≥40km/h, the rear wheel is controlled to be positively locked through the hydraulic steering unit, and then the control unit 4 is turned off;

S3, when the vehicle speed is less than 40 km/h, start the control unit 4;

S4. The control unit 4 outputs a signal according to the steering angle relationship between the left side (or right side) of the front wheel and the left side (or right side) of the rear wheel, and the steering angle relationship output signal is output to the first electromagnetic proportional valve 8 and the second electromagnetic proportional valve 9.

Furthermore, the turning angle relationship between the left side (or right side) of the front wheel and the left side (or right side) of the rear wheel should satisfy the Ackerman turning angle relationship, and the turning angle relationship between the right side (or left side) of the rear wheel and the left side (or right side) of the rear wheel is ensured by the steering trapezoidal mechanism;

The Ackerman conversion formula is:

Among them, a1 is the left (or right) turning angle of the front wheel, a2 is the left (or right) turning angle of the rear wheel, L1 is the distance from the front axle to the rear axle, and L2 is the distance from the rear axle to the tail axle.

S5. Compare the actual rear wheel steering angle at the current moment with the rear wheel steering angle converted by Ackerman. If the difference is within the set range, close the first electromagnetic proportional valve 8 and the second electromagnetic proportional valve 9; if the difference is outside the set range, open the first electromagnetic proportional valve 8 and the second electromagnetic proportional valve 9 to realize rear wheel steering.

The beneficial effects of the present invention are:

1. The steering system of the present invention only requires the installation of an electronically controlled hydraulic steering device on one side of the wheel, and the steering of the other side of the wheel is ensured by a steering trapezoidal structure. The rear axle and the front axle are not connected by a mechanical mechanism, and the structure is simple and the cost is low. Steering is achieved through sensors, hydraulic steering units and control technology.

2. Accurately control the rear wheel angle according to the front wheel angle to achieve precise control of rear wheel steering, thereby reducing rear wheel wear.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a heavy truck rear wheel steering system of the present invention;

Fig. 2 is a system connection diagram of a measuring device of the present invention;

FIG3 is a schematic diagram of the structure of a measuring device of the present invention;

1. Front wheel angle sensor; 2. Rear wheel angle sensor; 3. Vehicle speed signal; 4. Control unit; 5. Overflow valve; 6. Electric pump; 7. Throttle valve; 8. First electromagnetic proportional reversing valve; 9. Second electromagnetic proportional reversing valve; 10. Hydraulic cylinder.

DETAILED DESCRIPTION

The present invention is further described below in conjunction with the accompanying drawings and embodiments. This figure is a simplified schematic diagram, which only illustrates the basic structure of the present invention in a schematic manner, and therefore it only shows the components related to the present invention.

As shown in FIG1 , a heavy truck rear wheel steering system comprises: an input unit, a control unit 4 and a hydraulic steering unit, wherein the input unit and the hydraulic steering unit are both electrically connected to the control unit 4;

The input unit includes: a front wheel angle sensor 1, a rear wheel angle sensor 2, and a vehicle speed signal generator 3;

The control unit 4 outputs a vehicle speed signal and a front wheel angle signal according to the signal of the input unit to control the operation of the hydraulic steering unit;

The hydraulic steering unit includes: an electric pump 6, a first electromagnetic proportional reversing valve 8, a second electromagnetic proportional reversing valve 9, a relief valve 5, a throttle valve 7 and a hydraulic cylinder 10;

The front wheel angle sensor 1 is fixed on the side of the front axle, and the rear wheel angle sensor is fixed on the side of the rear axle. The front and rear wheel angle sensors must be installed on the same side;

When the vehicle starts, the electric pump 6 works continuously to ensure the timely response of the hydraulic steering unit, and the overflow valve 5 and the throttle valve 7 control the flow rate of the hydraulic oil and the pressure of the hydraulic cylinder;

The electric pump 6 is connected to the first electromagnetic proportional reversing valve 8 and the second electromagnetic proportional reversing valve 9 through the overflow valve 5 and the throttle valve 7;

The hydraulic cylinder 10 includes a left hydraulic cylinder and a right hydraulic cylinder. One side of the hydraulic cylinder as a whole is connected to the vehicle frame, and the other side is connected to the rear axle steering tie rod.

When the rear wheel needs to turn left, the oil passage enters from the left hydraulic cylinder A1 of the hydraulic cylinder 10 through the first electromagnetic proportional reversing valve 8 and flows out from B1; the oil passage enters from the right hydraulic cylinder A2 through the second electromagnetic proportional reversing valve 9 and flows out from B2, and the hydraulic cylinder retracts as a whole, pulling the steering tie rod of the steering trapezoid back to the right, so that the rear wheel turns left;

When the rear wheel needs to turn right, the oil passage enters from the left hydraulic cylinder B1 of the hydraulic cylinder 10 through the first electromagnetic proportional reversing valve 8 and flows out from A1; the oil passage enters from the right hydraulic cylinder B2 through the second electromagnetic proportional reversing valve 9 and flows out from A2. The hydraulic cylinder extends as a whole, pulling the steering tie rod of the steering trapezoid back to the left, thereby realizing the right turn of the rear wheel.

As shown in FIG2 , a control method for a rear wheel steering system of a heavy truck includes the following steps:

S1, the control unit 4 receives the vehicle speed signal collected by the vehicle speed signal generator 3, and determines whether the control unit 4 needs to be started;

S2, when the vehicle speed is ≥40km/h, the hydraulic steering unit is controlled to lock the rear wheels positively, and the control unit 4 is turned off;

S3, when the vehicle speed is less than 40 km/h, start the control unit 4;

S4, the control unit 4 outputs a signal according to the relationship between the left (or right) turning angle of the front wheel and the left (or right) turning angle of the rear wheel, and the turning angle relationship output signal is output to the first electromagnetic proportional valve 8 and the second electromagnetic proportional valve 9;

As shown in Figure 3, the relationship between the left turning angle of the front wheel and the left turning angle of the rear wheel should satisfy the Ackerman turning angle relationship, and the relationship between the left turning angle of the rear wheel and the left turning angle of the rear wheel is ensured by the steering trapezoidal mechanism;

The left turning angle of the front wheel and the left turning angle of the rear wheel should meet the relationship:

Where a1 is the left (or right) turning angle of the front wheel, a2 is the left (or right) turning angle of the rear wheel, L1 is the distance from the front axle to the rear axle, and L2 is the distance from the rear axle to the rear axle;

S5. The control unit 4 compares the actual rear wheel steering angle at the current moment with the rear wheel steering angle converted by Ackerman to determine whether the difference is within the range of ±0.5°. If so, the first and second electromagnetic proportional reversing valves are closed; if not, the first and second electromagnetic proportional reversing valves are opened to achieve rear wheel steering.

For example: L1 = 18 meters, L2 = 3 meters, the front wheel turns left at 3° at T1 (relative to the direction of the steering wheel returning to the positive direction), and according to Ackerman conversion, the rear wheel turns left at 0.5° at T1 (i.e., the actual rear wheel turning angle at T2);

If the front wheel turns left at 5° at T2, the rear wheel turns left at 0.835° at T2 according to Ackerman conversion, then the difference between the rear wheel steering angle at T2 and the actual rear wheel steering angle at T2 = 0.335°, which is within the range of ±0.5°, and the rear wheel does not perform steering operation;

If the front wheel turns left at 10° at T2, the rear wheel turns left at 1.68° at T2 according to Ackerman conversion, then the difference between the rear wheel steering angle at T2 and the actual rear wheel steering angle at T2 = 1.18°, which is outside the range of ±0.5°, then the first electromagnetic proportional reversing valve and the second electromagnetic proportional reversing valve are opened to realize the rear wheel steering;

Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims (2)

1. A heavy truck rear wheel steering system, comprising: the hydraulic steering system comprises an input unit, a control unit (4) and a hydraulic steering unit, wherein the input unit and the hydraulic steering unit are electrically connected with the control unit (4);

the input unit includes: the device comprises a front wheel steering angle sensor (1), a rear wheel steering angle sensor (2) and a vehicle speed signal generator (3); the front wheel steering angle sensor (1) is arranged on one side of the front wheel of the truck, and the rear wheel steering angle sensor (2) is arranged on the rear wheel of the truck and is arranged on the same side with the front wheel;

the vehicle speed signal generator (3) collects vehicle speed signals in real time and feeds the vehicle speed signals back to the control unit (4), and the front wheel steering angle sensor (1), the rear wheel steering angle sensor (2) and the vehicle speed signal generator (3) are all connected with the control unit (4);

the hydraulic steering unit includes: the hydraulic control system comprises an overflow valve (5), an electric pump (6), a throttle valve (7), a first electromagnetic proportional directional valve (8), a second electromagnetic proportional directional valve (9) and a hydraulic cylinder (10);

the electric pump (6) and the overflow valve (5) are connected to a first electromagnetic proportional directional valve (8) and a second electromagnetic proportional directional valve (9) through a throttle valve (7);

the other ends of the first electromagnetic proportional directional valve (8) and the second electromagnetic proportional directional valve (9) are respectively connected with a left hydraulic cylinder and a right hydraulic cylinder of the hydraulic cylinder (10), and the control ends are connected with the control unit (4);

when the rear wheel needs to turn left, the oil path channel enters from the left hydraulic cylinder A1 of the hydraulic cylinder (10) through the first electromagnetic proportional reversing valve (8), and B1 flows out; the oil path channel enters from the right hydraulic cylinder A2 through a second electromagnetic proportional reversing valve (9), and B2 flows out, the hydraulic cylinder is integrally retracted, and a steering trapezoidal tie rod is pulled back to the right, so that the left turning of a rear wheel is realized;

when the rear wheel needs to turn right, the oil path channel enters from a left hydraulic cylinder B1 of the hydraulic cylinder (10) through a first electromagnetic proportional reversing valve (8), and flows out from A1; the oil path channel enters from the right hydraulic cylinder B2 through a second electromagnetic proportional reversing valve (9), A2 flows out, the hydraulic cylinder integrally extends out, and a steering trapezoidal tie rod is pulled back to the left to realize the right turning of the rear wheel;

the control method adopting the rear wheel steering system of the heavy truck comprises the following steps:

s1, the control unit (4) receives a vehicle speed signal collected by the vehicle speed signal generator (3) and judges whether the control unit (4) needs to be started or not;

s2, when the vehicle speed is more than or equal to 40km/h, controlling the rear wheel to be locked in a positive mode through the hydraulic steering unit, and then closing the control unit (4);

s3, when the vehicle speed is less than 40km/h, starting a control unit (4);

s4, the control unit (4) outputs signals according to the relation between the rotation angle of one side of the front wheel and the rotation angle of the same side of the rear wheel, and the signals are respectively output to the first electromagnetic proportional reversing valve (8) and the second electromagnetic proportional reversing valve (9);

s5, comparing the actual turning angle of the rear wheel at the current moment with the turning angle of the rear wheel converted by Ackerman, and closing the first electromagnetic proportional reversing valve (8) and the second electromagnetic proportional reversing valve (9) if the difference value is in a set range; and if the difference value is out of the set range, the first electromagnetic proportional directional valve (8) and the second electromagnetic proportional directional valve (9) are opened to realize rear wheel steering.

2. The heavy truck rear wheel steering control method of claim 1, wherein the ackerman-converted equation is:

；

wherein,

is a corner at one side of the front wheel and is used for holding>

Is a corner at one side of the rear wheel at the same side with the front wheel,L1 is the distance from the front axle to the rear axle,Land 2 is the distance from the rear shaft to the tail shaft. />

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