KR20200062821A - Method for estimating rear wheel steering angle - Google Patents

Abstract

According to an embodiment of the present invention, a rear wheel steering system comprises: a hydraulic pump generating a hydraulic pressure needed in steering; a control valve controlling the hydraulic pressure generated by the hydraulic pump; a steering cylinder including a cylinder body and a piston rod moving with respect to the cylinder body and receiving the hydraulic pressure controlled by the control valve to steer rear wheels; an ECU receiving a steering angle of front wheels and a steering angle of the rear wheels and receiving a speed signal of a vehicle to control the control valve; an accumulator providing the hydraulic pressure all the time to maintain the neutral position of the rear wheels; and a pressure sensor connected to the accumulator to measure the pressure of a centering chamber of the steering cylinder, wherein the steering cylinder includes: the centering chamber communicating with the accumulator; and a steering chamber partitioned with respect to the centering chamber by a partition, and the ECU is configured to calculate a stroke of the piston rod and to calculate the steering angle of the rear wheels according to the calculated stroke by calculating a volume change rate of the centering chamber using the pressure measured by the pressure sensor.

Description

Rear wheel steering system and rear wheel steering angle estimation method {METHOD FOR ESTIMATING REAR WHEEL STEERING ANGLE}

The present invention relates to a rear wheel steering system and a rear wheel steering angle estimation method, and more specifically, by estimating the rear wheel steering angle using a pressure sensor of the centering accumulator, a rear wheel steering system capable of more accurately checking the rear wheel steering angle without using the rear wheel steering angle sensor, and It relates to a rear wheel steering angle estimation method.

In general, the steering system of a vehicle is a system for realizing the steering of a vehicle, and the rear wheel steering system adjusts the steering angle of the rear wheel according to the vehicle's front wheel angle and vehicle speed, thereby pursuing vehicle maneuverability at low speed and vehicle stability at high speed. System.

Commercial vehicles use multi-axes due to the de-axing restrictions (up to 10 tons per axle), which increases the turning radius and severely wears tires. To solve this, the front two-axis steering system was applied, and recently, the rear wheel steering system has been introduced.

The rear wheel steering system receives the steering angle of the front wheel from the front wheel steering angle sensor and steers the rear wheel axle by a pre-calculated target value. It controls to reduce the error by comparing the target value with the value measured by the rear wheel steering angle sensor in real time.

Conventional rear wheel steering system is provided with a hydraulic pump for generating the hydraulic pressure required for steering, a control valve for controlling the hydraulic pressure generated by the hydraulic pump, a steering cylinder for steering the rear wheel by receiving the controlled hydraulic pressure, and measures the steering angle of the front wheel The front wheel steering angle sensor, the rear wheel steering angle sensor for measuring the steering angle of the rear wheel, and the steering angle of the front wheel and the steering angle of the rear wheel are inputted from the front wheel steering angle sensor and the rear wheel steering angle sensor, respectively. It includes an ECU to control and an accumulator that provides hydraulic pressure to maintain the neutral position of the rear wheel in the event of a failure of the rear wheel steering system.

In the conventional rear wheel steering system, a rear wheel steering angle sensor for measuring a rear wheel steering angle is mounted through a linkage structure or is mounted on an upper or lower portion of a king pin.

However, the structure in which the rear wheel steering angle sensor is mounted by the linkage structure is vulnerable to external shock due to the linkage structure protruding to the outside, and the structure in which the rear wheel steering angle sensor is integrally inserted into the king pin portion is not only expensive for the sensor, but also a king pin. As other parts related to parts have to be additionally processed, the manufacturing cost thereof has been increased.

The items described in this background section are written to improve the understanding of the background of the invention, and may include matters other than the prior art already known to those skilled in the art.

The present invention was devised in consideration of the above points, and it is possible to more accurately check the rear wheel steering angle by estimating the rear wheel steering angle using an accumulator pressure sensor, and overcome the disadvantages on the package by not installing the rear wheel steering angle sensor. In addition, the aim is to provide a rear wheel steering system and a rear wheel steering angle estimation method that can reduce manufacturing costs.

The rear wheel steering system according to an embodiment of the present invention for achieving the above object,

A hydraulic pump that generates hydraulic pressure necessary for steering;

A control valve that controls the hydraulic pressure generated by the hydraulic pump;

A steering cylinder including a cylinder body and a piston rod moving relative to the cylinder body, and steering a rear wheel by receiving hydraulic pressure controlled by the control valve;

An ECU that controls the control valve by receiving the steering angle of the front wheel and the steering angle of the rear wheel, respectively, and receiving a vehicle speed signal;

An accumulator that always provides hydraulic pressure to maintain the neutral position of the rear wheel; And

It includes; a pressure sensor connected to the accumulator to measure the pressure of the centering chamber of the steering cylinder;

The steering cylinder includes a centering chamber communicating with the accumulator and a steering chamber partitioned with respect to the centering chamber by a partition wall,

The ECU may be configured to calculate the stroke of the piston rod by calculating the volume change rate of the centering chamber using the pressure measured by the pressure sensor, and to calculate the rear wheel steering angle by the calculated stroke.

The centering chamber may include an annular regulating ring provided on its inner surface, a left centering disk and a right centering disk movably disposed on both sides of the regulating ring.

The left centering disc is configured to contact or space one end of the piston rod, the right centering disc is slidably configured along the outer surface of the piston rod, and the steering piston is fixedly coupled to the outer surface of the piston rod, The steering piston may be configured to be movable in the steering chamber.

Another aspect of the present invention is a hydraulic pump for generating the hydraulic pressure required for steering, a control valve for controlling the hydraulic pressure generated by the hydraulic pump, a steering cylinder for steering the rear wheel by receiving the hydraulic pressure controlled by the control valve, the front wheel The steering angle of the rear wheel and the steering angle of the rear wheel are respectively input, and the ECU controlling the control valve by receiving the vehicle's speed signal, the accumulator that always provides hydraulic pressure to maintain the neutral position of the rear wheel, and the pressure of the steering cylinder connected to the accumulator As a method for estimating the rear wheel steering angle of a rear wheel steering system including a pressure sensor for measuring

As the rear wheel of the vehicle is steered, pressure is measured by a pressure sensor connected to the accumulator,

The stroke of the piston rod is calculated using the pressure measured by the pressure sensor,

The steering angle of the rear wheel can be calculated based on the calculated stroke of the piston rod.

The steering cylinder includes a cylinder body having a centering chamber communicating with the accumulator and a steering chamber partitioned with respect to the centering chamber by a partition wall, and a piston rod moving relative to the cylinder body,

By substituting the pressure measured by the pressure sensor into the ideal gas equation for the centering chamber, the volume change rate of the centering chamber may be calculated, and the stoke of the piston rod may be calculated using the volume change rate of the centering chamber.

According to the present invention, it is possible to more accurately check the rear wheel steering angle by estimating the rear wheel steering angle using the pressure sensor of the accumulator, and not only overcome the disadvantages on the package but also reduce the manufacturing cost by not using the rear wheel steering angle sensor. There is this.

1 is a view showing a rear wheel system according to an embodiment of the present invention.
2 is a view showing a structure in which the steering cylinder and the accumulator of the rear wheel system according to an embodiment of the present invention are connected, and when the steering cylinder is assembled, the piston rod is moved by the left centering disc and the right centering disc moving in the centering chamber. It is a diagram showing the process of being centered.
3 shows a state in which the piston rod is completely centered by the left centering disc and the right centering disc moving in the centering chamber of the steering cylinder as the rear wheel moves to the neutral position.
4 is a view illustrating one form of an accumulator of the rear wheel steering system of the present invention.
5 is a view showing a state in which the piston rod and the left centering disc move to the left when the rear wheel steers to the left in the rear wheel system of the present invention.
6 is a view showing a state in which the piston rod and the right centering disc move to the right when the rear wheel steers to the right in the rear wheel system of the present invention.
7 is a flowchart illustrating a rear wheel steering angle estimation method according to an embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail through exemplary drawings. It should be noted that in adding reference numerals to the components of each drawing, the same components have the same reference numerals as possible even though they are displayed on different drawings. In addition, in describing the embodiments of the present invention, when it is determined that detailed descriptions of related well-known configurations or functions interfere with the understanding of the embodiments of the present invention, detailed descriptions thereof will be omitted.

In describing the components of the embodiments of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only for distinguishing the component from other components, and the nature, order, or order of the component is not limited by the term. In addition, unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains. Terms such as those defined in a commonly used dictionary should be interpreted as having meanings consistent with meanings in the context of related technologies, and should not be interpreted as ideal or excessively formal meanings unless explicitly defined in the present application. Does not.

Referring to FIG. 1, the rear wheel steering system 1 according to an embodiment of the present invention includes a hydraulic pump 2 for generating hydraulic pressure required for steering, and a control valve for controlling the hydraulic pressure generated by the hydraulic pump 2 ( 3), by receiving the hydraulic pressure controlled by the control valve (3), the steering cylinder (4) for steering the rear wheel, and the steering angle of the front wheel and the steering angle of the rear wheel, respectively, and receiving the vehicle speed signal through CAN It includes an ECU 5 that controls the control valve 3 and an accumulator 6 that provides hydraulic pressure to maintain the neutral position of the rear wheel in the event of a failure of the rear wheel steering system.

The ECU 5 is configured to receive the steering angle of the front wheel from the front wheel steering angle sensor 8. The front wheel steering angle sensor 8 may be a steering angle sensor (SAS) mounted on the steering column of the vehicle,

The ECU 5 may be configured to estimate the steering angle of the rear wheel using the pressure sensor 7 connected to the accumulator 6.

The ECU 5 may be configured to receive information from the pressure sensor 7 and various sensors and transmit control signals to various actuators such as the control valve 3, hydraulic pump 2, and the like. The ECU 5 may include a processor and a memory, and the processor may receive control instructions and data stored in the memory and transmit control instructions to the actuators.

2 and 3, the steering cylinder 4 may include a cylinder body 10 and a piston rod 20 movable relative to the cylinder body 10.

The cylinder body 10 may include a centering chamber 11 in communication with the accumulator 6 and a steering chamber 12 partitioned with respect to the centering chamber 11 by a partition wall 13.

The centering chamber 11 includes an annular regulating ring 15 provided on the inner surface of the intermediate portion, a left centering disk 21 and a right centering disk 23 that are movably disposed on both sides of the regulating ring 15. Can be. As the regulation ring 15 is formed in an annular shape on the inner surface of the middle portion of the centering chamber 11, the regulation ring 15 may have a hollow portion.

The left centering disc 21 may be configured to contact or be spaced apart from the stopper 24 of the piston rod 20. In particular, the left centering disc 21 may be configured to move between the annular regulating ring 15 and the left wall of the centering chamber 11.

The right centering disc 23 can be configured to be slidable along the outer surface of the piston rod 20, and the right centering disc 23 can be contacted or spaced from the stopper 24 of the piston rod 20. In particular, the right centering disc 23 can be configured to move between the annular regulating ring 15 and the partition wall 13.

The centering chamber 11 may be communicatively connected to the accumulator 6 through the hydraulic line 6a. Accordingly, the hydraulic line 6a can fluidly connect the centering chamber 11 and the accumulator 6, and the pressure sensor 7 is mounted on the hydraulic line 6a so that the pressure sensor 7 is a steering cylinder 4 ) Can measure the pressure of the centering chamber 11, through which the ECU 5 is configured to detect the pressure change of the centering chamber 11 through the pressure sensor 7.

The piston rod 20 may pass through the partition wall 13 and reciprocate within the cylinder body 10. The stopper 24 may be fixedly coupled to one end of the piston rod 20, and the stopper 24 may have a diameter larger than the diameter of the piston rod 20. The outer diameter of the stopper 24 may be formed smaller than the inner diameter of the regulating ring 15. Accordingly, according to the movement of the piston rod 20, the stopper 24 passes through the hollow portion of the regulating ring 15 or the regulating ring 15 ). As the piston rod 20 moves, the stopper 24 may contact or be spaced apart from the left centering disc 21 or the right centering disc 23. For example, when the rear wheel of the vehicle is steered to the left, the piston rod 20 moves to the left, whereby the stopper 24 of the piston rod 20 is in contact with the left centering disc 21 as shown in FIG. 5. The left centering disc 21 can be pushed to the left. When the rear wheel of the vehicle is steered to the right, the piston rod 20 moves to the right, and accordingly, as shown in FIG. 6, the stopper 24 of the piston rod 20 comes into contact with the right centering disc 23 and right centering The disc 23 can be pushed to the right.

The steering piston 22 may be fixedly coupled to the outer surface of the piston rod 20, and the steering piston 22 may be located in the steering chamber 12. Accordingly, the steering piston 22 may move in the steering chamber 12 according to the movement of the piston rod 20. The other end of the piston rod 20 may be connected to the steering arm (9), whereby the rear wheel (1) is steered by operating the steering arm (9) according to the travel distance (stroke) of the piston rod (20) Can be.

Referring to FIG. 4, the accumulator 6 includes a container 31, a rubber container 32 disposed in the container 31, a gas chamber 34 formed in the rubber container 32, and a fluid in which oil is stored. It may include a chamber 33. The gas chamber 34 is filled with compressed gas, and the rubber container 32 stores the oil stored in the fluid chamber 33 through the fluid port 35 by the pressure of the compressed gas charged in the gas chamber 34 through the fluid port 35. (11) You can always push to the side.

If the pressure of the centering chamber 11 is the same as the initial pressure (eg, 15 bar) of the fluid chamber 33 of the accumulator 6, as shown in FIG. 3, the left centering disc 21 and the left centering disc 21 by the initial pressure of the accumulator 6 The centering disc 23 can be in opposite (symmetric) contact with the regulating ring 15, through which the piston rod 20 can be centered against the centering chamber 11 of the steering cylinder 10 and , This allows the rear wheel to move to the neutral position. That is, since the pressure of the centering chamber 11 receives the initial pressure of the accumulator 6, the piston rod 20 tends to always maintain the centering (neutral) with respect to the steering cylinder 10.

If the pressure in the steering chamber 12 increases up to 140 bar as the hydraulic pressure generated by the hydraulic pump 2 for steering of the rear wheel is supplied into the steering chamber 12 through the control valve 3, the steering chamber 12 Since the pressure in) becomes greater than the pressure in the centering chamber 11, the piston rod 20, as shown in FIGS. 5 and 6, steers the rear wheel 1 through the steering arm 9 by moving in constant strokes S1 and S2. can do.

When the rear wheel 1 is steered to the left, the piston rod 20 can move to the left from the steer cylinder 10, as shown in FIG. 5, and the right centering disc 23 is the regulating ring 15 In contact with the left centering disc 21 may move to the left stroke S1 from the regulating ring 15 of the centering chamber 11 toward the left.

When the rear wheel 1 is steered to the right, the piston rod 20 can move to the right from the steer cylinder 10, as shown in FIG. 6, and thus the left centering disc 21 is the regulating ring 15 In contact with the right centering disc 23 can move from the regulating ring 15 of the centering chamber 11 toward the right to the right stroke S2.

As described above, when the piston rod 20 steers the rear wheel 1 due to the difference in pressure in the steering chamber 12 and the pressure in the centering chamber 11, the volume of the centering chamber 11 is changed, thereby accumulating the accumulator 6. Pressure can change. For example, the pressure of the accumulator 6 is the smallest at the centering (neutral) of the steering cylinder 10, and may increase proportionally according to the steering angle of the rear wheel 1 corresponding to the stroke of the piston rod 20. . The pressure sensor 7 can measure the rate of pressure change of the accumulator 6, and can calculate the steering angle of the rear wheel 1 by calculating the stroke of the piston rod 20 in response to the rate of pressure change of the accumulator 6. have.

The ideal gas equation of the centering chamber 11 may be defined as Equation (1) below.

P ₁ V ₁ (neutral) = P ₂ V ₂ (steer)...Equation (1)

Here, P ₁ is the pressure in the centering chamber 11 in the neutral (centering) state of the rear wheel, V ₁ is the volume of the centering chamber 11 in the neutral (centering) state of the rear wheel, and P ₂ is when the rear wheel is steered. The pressure in the centering chamber 11, V ₂ is the volume of the centering chamber 11 when steering the rear wheel. Specifically, when the rear wheel 1 is steered to the left, the pressure P ₂ and the volume V ₂ of the centering chamber 11 as shown in FIG. 5 are the effective area A and the left stroke of the left centering disc 21. It can be calculated by (S1), the pressure (P ₂ ) and the volume (V ₂ ) of the centering chamber 11 as shown in FIG. 6 when the rear wheel (1) is steered to the right is effective of the right centering disc (23). It can be calculated by the area B and the right stroke S2.

According to an example, the compressed gas charged in the gas chamber 34 of the accumulator 6 is nitrogen, the initial pressure of the accumulator 6 is 15 bar, and the rubber container 32 of the accumulator 6 is 1.5 liter, In the neutral (centering) state of the rear wheel, the volume of the centering chamber 11 is 1 l, the effective area (A) of the left centering disk 21 is 63.6 cm2, and the effective area (B) of the right centering disk 23 is 44. Cm2. Substituting the above-described example into Equation (1) is as in Equation (2) below.

(1bar(atmospheric pressure) + 15bar)×1ℓ = (P+1)bar×(1-△V)ℓ...Equation (2)

Here, ΔV is the volume change rate of the centering chamber 11 when switching from the neutral state of the rear wheel to the steering state of the rear wheel, “ΔV=effective area (A, B) of each centering disc 21, 23×stroke ( S1, S2)", and P is the pressure measured by the pressure sensor 7 in the steering state of the rear wheel 1.

From the above equations (1) and (2), the stroke (S) of the piston rod (20) through the pressure (P) measured by the pressure sensor (7) and the volume change rate (ΔV) of the centering chamber (11) ) Can be calculated, the angle of the steering arm 9 of the vehicle is calculated from the calculated stroke S of the piston rod 20, and the rear wheel steering angle can be calculated based on the angle of the steering arm 9. have. For example, assuming that the pressure P measured by the pressure sensor 7 when the rear wheel is steered to the left is 24 bar, ΔV is calculated to be 0.36 l, which is the effective area (A) of the left centering disc 21. = 63.6 cm 2 ), it can be calculated that the stroke is approximately 56 mm.

7 is a flowchart illustrating a method of estimating a rear wheel steering angle according to an embodiment of the present invention.

The pressure sensor 7 connected to the accumulator 6 measures the pressure of the centering chamber 11 as the rear wheel of the vehicle is steered to the right or left in the neutral state (the centering state of the piston rod 20), and the ECU 5 ) Determines whether the pressure of the centering chamber 11 measured by the pressure sensor 7 changes compared to the centering state of the piston rod 20 (S1).

When the pressure measured by the pressure sensor 7 changes as compared to the centering state of the piston rod 20, the ECU 5 measures the pressure measured by the pressure sensor 7 to the ideal gas equation of the centering chamber 11 By substituting in (Equation (1)), the volume change rate of the centering chamber 11 is calculated (S2).

The strokes S1 and S2 of the piston rod 20 are calculated from the effective area of each centering disc 21 and 23 of the centering chamber 11 and the volume change rate of the centering chamber 11 (S3). For example, when the rear wheel 1 is steered to the left as shown in FIG. 5, the left stroke of the piston rod 20 using the effective area A of the left centering disc 21 and the volume change rate of the centering chamber 11 ( S1). When the rear wheel (1) is steered to the right as shown in Figure 6, the right stroke (S2) of the piston rod (20) using the effective area (B) of the right centering disc (21) and the volume change rate of the centering chamber (11) To calculate.

The ECU 5 calculates the angle of the steering arm 9 of the vehicle from the calculated strokes S1 and S2 of the piston rod 20, and calculates the rear wheel steering angle based on the angle of the steering arm 9 ( S4).

According to the present invention as described above, the rear wheel steering angle can be confirmed more accurately by estimating the rear wheel steering angle using the pressure information measured by the pressure sensor of the accumulator 6 and the volume change rate of the centering chamber 11.

In particular, the present invention is very advantageous in terms of a package because it does not apply a linkage when compared to a linkage type rear wheel steering angle sensor, and compared to a rear wheel steering angle sensor integrally coupled to a kingpin, there is no need to additionally process the existing parts, thereby manufacturing It has a very easy advantage.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and variations without departing from the essential characteristics of the present invention.

Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the claims below, and all technical spirits within the equivalent range should be interpreted as being included in the scope of the present invention.

1: Rear wheel steering system 2: Hydraulic pump
3: Control valve 4: Steering cylinder
5: ECU 6: Accumulator
7: Pressure sensor 8: Front wheel steering angle sensor
9: Steering arm 10: Cylinder body
11: Centering chamber 12: Steering chamber
13: partition wall 15: regulatory ring
20: piston rod 21: left centering disc
22: steering piston 23: centering disc

Claims (5)

A hydraulic pump that generates hydraulic pressure necessary for steering;
A control valve that controls the hydraulic pressure generated by the hydraulic pump;
A steering cylinder including a cylinder body and a piston rod moving relative to the cylinder body, and steering a rear wheel by receiving hydraulic pressure controlled by the control valve;
An ECU that controls the control valve by receiving the steering angle of the front wheel and the steering angle of the rear wheel, respectively, and receiving a vehicle speed signal;
An accumulator that always provides hydraulic pressure to maintain the neutral position of the rear wheel; And
It includes; a pressure sensor connected to the accumulator to measure the pressure of the centering chamber of the steering cylinder;
The steering cylinder includes a centering chamber connected to the accumulator and a steering chamber partitioned with respect to the centering chamber by a partition wall,
The ECU is configured to calculate the stroke of the piston rod by calculating the volume change rate of the centering chamber using the pressure measured by the pressure sensor, and to calculate the rear wheel steering angle based on the calculated stroke. The method according to claim 1,
The centering chamber is a rear wheel steering system including an annular regulating ring provided on its inner surface, a left centering disc and a right centering disc movably disposed on both sides of the regulating ring. The method according to claim 2,
The left centering disc is configured to contact or space one end of the piston rod, the right centering disc is slidably configured along the outer surface of the piston rod, and the steering piston is fixedly coupled to the outer surface of the piston rod, The steering piston is a rear wheel steering system movable within the steering chamber. A hydraulic pump for generating the hydraulic pressure required for steering, a control valve for controlling the hydraulic pressure generated by the hydraulic pump, a steering cylinder for steering the rear wheel by receiving the hydraulic pressure controlled by the control valve, the steering angle of the front wheel and the steering angle of the rear wheel ECU for controlling the control valve by receiving the input of each and the speed signal of the vehicle, an accumulator that always provides hydraulic pressure to maintain the neutral position of the rear wheel, and a pressure sensor connected to the accumulator to measure the pressure of the steering cylinder. As a method for estimating the rear wheel steering angle of the included rear wheel steering system,
As the rear wheel of the vehicle is steered, pressure is measured by a pressure sensor connected to the accumulator,
The stroke of the piston rod is calculated using the pressure measured by the pressure sensor,
A rear wheel steering angle estimation method for calculating the rear wheel steering angle based on the calculated stroke of the piston rod. The method according to claim 4,
The steering cylinder includes a cylinder body having a centering chamber and a steering chamber, and a piston rod moving relative to the cylinder body,
Rear wheel steering angle to calculate the volume change rate of the centering chamber by substituting the pressure measured by the pressure sensor into the ideal gas equation for the centering chamber and to calculate the torque of the piston rod using the volume change rate of the centering chamber Estimation method.

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