JP7593243B2 - Steering gear - Google Patents

Description

The present invention relates to a steering device equipped with a steering mechanism in which part of the steering force is applied by a hydraulic mechanism.

Conventionally, there exists a power steering system that is provided with an electric power steering device and a hydraulic power steering device to provide an auxiliary force to the steering mechanism.

For example, the electric power steering device described in Patent Document 1 and the power steering device equipped with a hydraulic power steering device distribute the assist torque provided by the electric power steering device and the assist torque provided by the hydraulic power steering device according to the vehicle speed. In addition, the steering wheel return assist amount according to the steering angle is calculated from a map, and the electric power steering is controlled so that the control current corresponds to the assist control amount, thereby performing steering wheel return control.

JP 2006-213094 A

However, it is extremely difficult to detect abnormalities in hydraulic power steering. For example, attempts have been made to detect abnormalities in hydraulic power steering from the amount of twist in a torsion bar, which measures the torque when the driver operates the steering wheel, but there is a restriction that the spring constant of the torsion bar must be large in order to detect abnormalities, making it difficult to select a torsion bar that can be used in actual equipment.

The present invention was developed in consideration of the above problems, and aims to provide a steering device that can easily detect the occurrence of an abnormality in the hydraulic mechanism.

In order to achieve the above object, a steering device according to the present invention includes a steering mechanism for steering a steered wheel, a drive device connected to the steering mechanism via a steering shaft and for applying a first torque to the steering mechanism, a hydraulic mechanism for applying an assist force to the steering mechanism, and a control device for controlling the drive device. The control device includes an information acquisition unit for acquiring torque information related to the torque including the first torque applied to the steering mechanism and angular acceleration information related to the actual angular acceleration of the steering shaft, an angular acceleration estimation unit for deriving an estimated angular acceleration corresponding to the actual angular acceleration of the steering shaft based on the acquired torque information, and an abnormality detection unit for detecting an abnormality in the hydraulic mechanism based on the actual angular acceleration of the steering shaft and the estimated angular acceleration.

The present invention makes it easy to detect abnormalities in hydraulic mechanisms.

FIG. 1 is a diagram illustrating a steering system including a steering device. FIG. 2 is a block diagram showing the functional configuration of the steering device. FIG. 13 is a diagram showing an actual transfer function F1(s). FIG. 13 is a diagram illustrating a schematic diagram of another example of a steering system including a steering device.

Below, an embodiment of the steering device according to the present invention will be described with reference to the drawings. Note that the following embodiment is presented as an example to explain the present invention, and is not intended to limit the present invention. For example, the shapes, structures, materials, components, relative positional relationships, connection states, numerical values, mathematical expressions, the contents of each step in the method, and the order of each step shown in the following embodiment are merely examples, and may include contents not described below. In addition, while geometric expressions such as parallel and orthogonal may be used, these expressions do not indicate mathematical strictness, and include substantially acceptable errors, deviations, and the like. In addition, expressions such as simultaneous and identical also include substantially acceptable ranges.

The drawings are schematic diagrams in which emphasis, omissions, or proportions have been appropriately adjusted in order to explain the present invention, and may differ from the actual shapes, positional relationships, and proportions.

In addition, multiple inventions may be collectively described below as a single embodiment. Some of the content described below is also described as an optional component of the present invention.

Figure 1 is a schematic diagram of a steering system equipped with a steering device. The steering system 200 is a system that steers steered wheels 220 according to a target steering angle and controls the traveling direction of a vehicle in which the steering system 200 is installed. The steering system 200 includes a steering device 100, an operation input means 210, and an automatic control device 250.

The operation input means 210 is a device that outputs a target steering angle intended by the driver when the driver operates an operating member 211 such as a steering wheel. In the present embodiment, as shown in FIG. 1, the operation input means 210 includes an operating member 211, an operating shaft 212, and a target steering angle detection means 213. The operation input means 210 may further include a torque detection device, a reaction force device, etc.

The operating shaft 212 is a rod-shaped member that is mechanically connected to the operating member 211 and rotates in response to the operation of the operating member 211. In this embodiment, the operating shaft 212 is connected to a reaction means, and a reaction force is applied to the driver operating the operating member 211 to give the driver a steering sensation according to the driving state.

The manner of connection between the operating shaft 212 and the steering mechanism 150 is not particularly limited. For example, the operating shaft 212 may be mechanically connected to the pinion shaft 151 via the steering shaft 119, and during automatic driving, the mechanical connection between the operating shaft 212 and the pinion shaft 151 may be disconnected using a clutch or the like. In the case of this embodiment, the operating shaft 212 and the steering mechanism 150 are not mechanically connected, and the steering system 200 is a so-called steer-by-wire system.

The target rudder angle detection means 213 is a device that detects the rotation angle of the operating member 211 and outputs it as a target rudder angle. In the present embodiment, the target rudder angle detection means 213 detects the rotation of the operating shaft body 212 as the rotation of the operating member 211. The type of the target rudder angle detection means 213 is not particularly limited, but examples include a resolver and a rotary encoder.

The automatic control device 250 is one of the ECUs (Electronic Control Units) for automatically driving the vehicle equipped with the steering system 200. In this embodiment, the automatic control device 250 acquires information on obstacles outside the vehicle, white lines on the road, traffic lights, etc. from sensors such as a camera 251 and a laser rider 252, and sequentially generates a target steering angle corresponding to the automatic driving based on the acquired information and outputs it to the control device 130 of the steering device 100.

The steering device 100 is a device that steers the steered wheels 220 based on a target steering angle to direct the vehicle, and includes a steering mechanism 150, a drive unit 110, a hydraulic mechanism 140, and a control device 130.

The steering mechanism 150 is a mechanism for steering the steered wheels 220. Although there is no particular limitation to the steering mechanism 150, in this embodiment, a rack and pinion is used. Specifically, the steering mechanism 150 includes a pinion shaft 151, a rack shaft 152, and a tie rod 153.

The pinion shaft 151 is a rod-shaped member equipped with a pinion that meshes with a rack provided on the rack shaft 152. The pinion shaft 151 is connected to the steering device 100, and rotates when torque is applied from the drive device 110, moving the rack shaft 152 in the axial direction of the rack shaft 152.

The rack shaft 152 is a member that has a rack on part of its outer periphery that meshes with the pinion shaft 151, converts the rotation of the pinion shaft 151 into the axial movement of the rack shaft 152, and turns the steered wheels 220 via the tie rod 153. A hydraulic mechanism 140 is connected to the rack shaft 152, and an assist force is applied to steer the steered wheels 220 by hydraulic pressure. The rack shaft 152 is housed in a rack housing attached to the vehicle body, and the movement of the rack shaft 152 is guided by the rack housing.

The drive device 110 is connected to the steering mechanism 150 via a steering shaft 119 and applies a first torque to the steering mechanism 150. The configuration of the drive device 110 is not particularly limited, but in this embodiment, the drive device 110 includes an electric motor 111 and a reduction gear 112, and the output shaft (not shown) of the electric motor 111 is connected to the steering shaft 119 via the reduction gear 112. The first torque, which is the torque applied by the drive device 110 to the steering mechanism 150, is significantly smaller than the assist force applied by the hydraulic mechanism 140 to the steering mechanism 150 in a normal state. For example, most of the force that steers the steered wheels 220 is a hydraulic steering force, and the first torque is transmitted to the steering mechanism 150 as a control force for controlling the steering angle and steering direction of the steered wheels 220.

In this embodiment, the drive device 110 is equipped with a rotation angle detection means 113. In this embodiment, the rotation angle detection means 113 is a device that detects the rotation angle of the output shaft of the electric motor 111 and outputs it as a detected rotation angle. The type of rotation angle detection means 113 is not particularly limited, but in this embodiment, the rotation angle detection means 113 is equipped with a main gear that rotates together with the output shaft of the electric motor 111 and two driven gears of different diameters that mesh with the main gear, and is capable of detecting not only the rotation angle of the output shaft but also the rotation direction by detecting the rotation of the permanent magnets provided on each of the driven gears using a hall element or the like.

The hydraulic mechanism 140 adjusts the hydraulic pressure according to the rotation angle of the pinion shaft 151, etc., and applies the axial force of the rack shaft 152 to the rack shaft 152 as an assist force. Although not limited to any particular type, in this embodiment, the hydraulic mechanism 140 includes a power cylinder 141, a rotary valve 142, an oil pump 143, and a reservoir tank 144.

The power cylinder 141 has a cylinder 146 separated into two spaces by a piston 145, and the piston 145 moves in the axial direction of the rack shaft 152 by adjusting the hydraulic pressure of the oil filled in each of the two spaces. The piston 145 is connected to the rack shaft 152, and a force in the moving direction is applied from the piston 145 to the rack shaft 152.

The rotary valve 142 is a device that adjusts the oil pressure supplied to each of the two spaces separated by the piston 145. The structure of the rotary valve 142 is not particularly limited, but in this embodiment, it is equipped with a torsion bar (not shown) that is interposed in the steering shaft 119 between the pinion shaft 151 and the steering device 100. The rotary valve 142 controls the operation of the piston 145 by adjusting the amount of oil pumped from the oil pump 143 to be supplied to one of the two spaces separated by the piston 145 in response to the relative movement between the inner valve and the outer valve caused by the twisting of the torsion bar, and by adjusting the amount of excess oil in the other space that is returned to the reservoir tank 144.

Figure 2 is a block diagram showing the functional configuration of the control device. The control device 130 is a device that controls the drive device 110 so that the rotation angle of the output shaft corresponds to the target steering angle, and is one of the ECUs. The control device 130 also constantly monitors the state of the hydraulic mechanism 140 and detects the occurrence of abnormalities. The control device 130 includes an information acquisition unit 131, an angular acceleration estimation unit 132, an abnormality detection unit 133, and a drive control unit 134 as processing units that are realized by executing a program.

The information acquisition unit 131 is a processing unit that acquires torque information related to the torque applied to the steering mechanism 150 and angular acceleration information related to the actual angular acceleration of the steering shaft 119. The source from which the torque information is acquired is not particularly limited, and for example, a dedicated torque detection device may be attached to the steering shaft 119. In the case of this embodiment, the information acquisition unit 131 acquires the torque information based on the amount of twist of the torsion bar attached to the rotary valve 142 of the hydraulic mechanism 140. This eliminates the need to provide a dedicated torque detection device, reduces the number of parts in the steering device 100, and improves assembly efficiency.

The source of the acceleration information is not particularly limited, and the actual angular acceleration of the steering shaft 119 may be obtained from a dedicated angular acceleration detection device attached to the steering shaft 119, for example. In this embodiment, the information acquisition unit 131 sequentially acquires the detected rotation angle of the output shaft of the electric motor 111 as angle information from the rotation angle detection means 113 provided in the drive unit 110. The information acquisition unit 131 outputs the actual angular acceleration by performing a calculation (for example, 2-degree time differentiation) using the acquired rotation angle. In this embodiment, since the output shaft of the electric motor 111 is connected to the steering shaft 119 via the reducer 112, the information acquisition unit 131 outputs the actual angular acceleration of the steering shaft 119 taking into account the reduction ratio of the reducer 112.

The angular acceleration estimation unit 132 is a processing unit that derives an estimated angular acceleration related to the angular acceleration of the steering shaft 119 based on the torque information acquired by the information acquisition unit 131. The method by which the angular acceleration estimation unit 132 derives the estimated angular acceleration is not limited. For example, the angular acceleration estimation unit 132 may derive the estimated angular acceleration using artificial intelligence. In the case of this embodiment, the angular acceleration estimation unit 132 derives the estimated angular acceleration using a transfer function. Figure 3 is a diagram showing the actual transfer function F1(s) of a steering device to which steered wheels are connected. The angular acceleration estimation unit 132 derives the estimated angular acceleration using an estimated transfer function F2(s) that imitates the actual transfer function shown in Figure 3.

The abnormality detection unit 133 is a processing unit that detects an abnormality in the hydraulic mechanism 140 based on the actual angular acceleration output by the information acquisition unit 131 and the estimated angular acceleration derived by the angular acceleration estimation unit 132. In the present embodiment, the abnormality detection unit 133 detects that an abnormality has occurred when the difference between the actual angular acceleration and the estimated angular acceleration is equal to or greater than a predetermined threshold value.

In the normal mode in which the hydraulic mechanism 140 is in a normal state, the drive control unit 134 controls the drive unit 110 by PID control or the like so that the actual steering angle of the steered wheels 220 matches the target steering angle based on the acquired target steering angle. In the case of this embodiment, when the abnormality detection unit 133 detects an abnormality, the drive unit 110 switches to an enhanced mode in which the drive unit 110 is controlled to generate a stronger torque than before the abnormality was detected. The enhanced mode is, for example, a mode in which the drive unit 110 generates a torque equal to or comparable to the assist force that the hydraulic mechanism 140 applies to the rack shaft 152 of the steering mechanism 150 when no abnormality is occurring. As a result, even in a situation in which an abnormality occurs in the hydraulic mechanism 140 and an assist force cannot be applied to the rack shaft 152, the drive control unit 134 can steer the steered wheels 220 and the vehicle can run.

In the enhanced mode, the electric motor 111 of the drive unit 110 may be operated above the rated speed, so the drive control unit 134 ends the enhanced mode after a predetermined period of time has elapsed since the abnormality detection unit 133 detected an abnormality, and causes the drive unit 110 to stop operating above the rated speed in a short period of time. The predetermined period of time is, for example, the time required for the vehicle to be safely stopped on the shoulder of the road after an abnormality occurs in the hydraulic mechanism 140, or the time required for the vehicle to be safely stopped while continuing to travel along a curve if an abnormality occurs in the hydraulic mechanism 140 while traveling along a curve.

The steering device 100 provided in the above steering system 200 makes it possible to easily detect abnormalities in the hydraulic mechanism 140 without providing a dedicated sensor for detecting abnormalities in the hydraulic mechanism 140.

In addition, by comparing the actual angular acceleration of the steering shaft 119 with the estimated angular acceleration, abnormalities in the hydraulic mechanism 140 can be detected more accurately than when comparing with other parameters, such as angular velocity.

In addition, abnormalities in the hydraulic mechanism 140 can be detected even in a steer-by-wire structure or during autonomous driving.

In addition, after detecting an abnormality in the hydraulic mechanism 140, the drive unit 110 can be controlled in enhanced mode to steer the steered wheels 220, making it possible to safely stop the vehicle.

The present invention is not limited to the above-described embodiment. For example, the components described in this specification may be combined in any way, or some of the components may be removed to create another embodiment of the present invention. The present invention also includes modifications that are made to the above-described embodiment by those skilled in the art without departing from the spirit of the present invention, i.e., the meaning of the words in the claims.

For example, as shown in FIG. 4, the steering system 200 may be such that the steering shaft 119 and the operating shaft 212 are mechanically connected to each other, so that the second torque generated when the driver operates the operating member 211 is mechanically transmitted as part of the torque applied to the steering mechanism 150. In this case, the angular acceleration estimation unit 132 derives the estimated angular acceleration based on the torque obtained by adding the first torque to the second torque. In addition, in the enhanced mode after the abnormality is detected, the drive control unit 134 controls the drive device 110 so that the assist force applied to the rack shaft 152 of the steering mechanism 150 by the hydraulic mechanism 140 when no abnormality is occurring is equal to or comparable to the torque obtained by adding the first torque to the second torque.

Also, as shown in FIG. 4, the rotation angle detection means 113 may directly detect the rotation angle of the steering shaft 119.

The present invention can be used in vehicles, particularly large vehicles, agricultural vehicles, construction vehicles, and other vehicles that require a large force to steer the wheels.

100... steering device, 110... drive device, 111... electric motor, 112... reducer, 113... rotation angle detection means, 119... steering shaft, 130... control device, 131... information acquisition unit, 132... angular acceleration estimation unit, 133... abnormality detection unit, 134... drive control unit, 140... hydraulic mechanism, 141... power cylinder, 142... rotary valve, 143... oil pump, 144... reservoir tank, 145... piston, 146... cylinder, 150... steering mechanism, 151... pinion shaft, 152... rack shaft, 153... tie rod, 200... steering system, 210... operation input means, 211... operation member, 212... operation shaft, 213... target steering angle detection means, 220... steered wheel, 250... automatic control device, 251... camera, 252... laser rider

Claims (4)

A steering mechanism for steering the steered wheels;
a drive device connected to the steering mechanism via a steering shaft body and configured to apply a first torque to the steering mechanism;
a hydraulic mechanism that applies an assist force to the steering mechanism;
A control device that controls the drive device,
The control device includes:
an information acquisition unit that acquires torque information regarding a torque including the first torque applied to the steering mechanism and angular acceleration information regarding an actual angular acceleration of the steering shaft;
an angular acceleration estimator that derives an estimated angular acceleration corresponding to an actual angular acceleration of the steering shaft based on the acquired torque information;
an abnormality detection unit that detects an abnormality in the hydraulic mechanism based on the actual angular acceleration of the steering shaft and the estimated angular acceleration of the steering shaft. The steering device according to claim 1 , wherein the torque information acquired by the information acquisition unit includes the first torque and a second torque applied to the steering shaft by an operation of a driver. The control device includes:
3. The steering device according to claim 1, further comprising a drive control section that switches to an enhanced mode in which, when the abnormality detection section detects an abnormality, the drive device is controlled so as to generate a stronger torque than before the abnormality was detected. The drive control unit is
The steering device according to claim 3 , wherein the enhanced mode is terminated when a predetermined period of time has elapsed since the abnormality detection unit detected an abnormality.

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