JP7428111B2 - steering gear - Google Patents

Description

The present invention relates to a steering device in which a part of the steering force is applied by a hydraulic mechanism and the other part of the steering force is applied by an electric motor.

Hydraulic power steering devices have been known in the past that apply hydraulic fluid from an oil pump to a power cylinder connected to the steering mechanism of a vehicle through a hydraulic control valve to provide assist force to the steering mechanism. ing. For example, a power steering device (steering device) described in Patent Document 1 is a device that uses an electric motor in addition to an oil pump to apply assist force to a steering mechanism. In such a steering device, the assist control amount during steering wheel return control according to the steering angle of the steering wheel (steering member) is determined from the MAP, and the electric motor is controlled so that the control current corresponds to the assist control amount. It is designed to perform return control.

Japanese Patent Application Publication No. 2006-213094

By the way, the above-mentioned handle return control does not take into account fluctuations in the pump flow rate due to the oil pump, so even if the handle return control is performed, the engine speed will drop and the handle return control will become unstable. There is a risk.

An object of the present invention has been made in view of the above problems, and is to improve the stability of handle return control by making it less susceptible to fluctuations in pump flow rate.

In order to achieve the above object, a steering device that is one aspect of the present invention includes an input shaft that is connected to a steering member and rotates in accordance with a steering operation on the steering member, and an output that rotates in conjunction with the rotation of the input shaft. a shaft, a first transmission mechanism that transmits the rotation of the input shaft to the output shaft, a second transmission mechanism that transmits the rotation of the output shaft to the steered wheels, and an electric motor that applies a first assist force to the first transmission mechanism. , has an oil pump powered by an engine included in the vehicle, a hydraulic mechanism that applies the power of the oil pump to the second transmission mechanism as a second assist force, and a motor control unit that controls the electric motor, and the motor The control unit estimates a hydraulic return torque caused by oil pressure among the return torque for returning the steering member to the reference position based on flow rate information regarding the flow rate of the oil pump and a steering angular velocity of the steering member; The return torque is estimated based on the vehicle speed of the vehicle and the steering angle of the steering member, and the electric motor is controlled based on the difference between the return torque and the hydraulic return torque.

According to the present invention, the stability of handle return control can be improved by making it less susceptible to fluctuations in pump flow rate.

1 is a diagram schematically representing a steering device according to an embodiment. FIG. 2 is a block diagram showing a functional configuration of a motor control section according to an embodiment. FIG. 3 is a block diagram showing functional units related to return control in the control unit according to the embodiment. It is an explanatory view showing an example of target steering angle MAP concerning an embodiment. It is an explanatory view showing return torque MAP concerning an embodiment. It is an explanatory view showing vehicle speed gain MAP concerning an embodiment. It is an explanatory view showing torque gain MAP concerning an embodiment. It is an explanatory view showing an example of oil pressure return torque MAP concerning an embodiment. It is a figure showing typically a steering device concerning a modification.

Embodiments of a steering device according to the present invention will be described below with reference to the drawings. Note that the numerical values, shapes, materials, components, positional relationships of the components, connection states, steps, order of steps, etc. shown in the following embodiments are merely examples, and do not limit the present invention. In addition, although multiple inventions may be described below as one embodiment, constituent elements not stated in a claim will be explained as arbitrary constituent elements with respect to the claimed invention. ing. Further, the drawings are schematic diagrams with appropriate emphasis, omission, and ratio adjustment for explaining the present invention, and may differ from the actual shapes, positional relationships, and ratios.

[Steering device]
FIG. 1 is a diagram schematically showing a steering device according to an embodiment. The steering device 200 is a system that steers the steerable wheels 220 according to a target steering angle and controls the traveling direction of a vehicle in which the steering device 200 is mounted. The steering device 200 includes a steering mechanism 230, a hydraulic mechanism 240, a manual operation mechanism 210, an electric motor 110, and a motor control section 100.

The steering mechanism 230 is a mechanism for steering the steered wheels 220, and is an example of the second transmission mechanism according to the present invention. The steering mechanism 230 is not particularly limited, but in this embodiment, a rack and pinion is employed. Specifically, the steering mechanism 230 includes a pinion shaft 231, a rack shaft 232, and a tie rod 233.

The pinion shaft 231 is a rod-shaped member that includes a pinion that meshes with a rack provided on the rack shaft 232. The pinion shaft 231 is connected to the electric motor 110 and rotates when torque from the electric motor 110 and torque from the steering member 211 are applied to move the rack shaft 232 in the axial direction of the rack shaft 232. The pinion shaft 231 is an example of an output shaft according to the present invention.

The rack shaft 232 is provided with a rack that engages with the pinion shaft 231 on a part of its outer peripheral surface, converts the rotation of the pinion shaft 231 into an axial movement amount of the rack shaft 232, and controls the steered wheels 220 via the tie rod 233. It is a member for steering. A hydraulic mechanism 240 is connected to the rack shaft 232, and a so-called assist force, which is a part of the steering force for steering the steered wheels 220, is applied by hydraulic pressure. The rack shaft 232 is housed in a rack housing attached to the vehicle body, and movement of the rack shaft 232 is guided by the rack housing.

The hydraulic mechanism 240 adjusts the hydraulic pressure according to the rotation angle of the pinion shaft 231, etc., and applies a force in the axial direction of the rack shaft 232 to the rack shaft 232 as part of the steering force. A part of the steering force applied by the hydraulic mechanism 240 is a hydraulic steering force, and is an example of the second assist force. Although not particularly limited, the hydraulic mechanism 240 includes a power cylinder 241, a rotary valve 242, an oil pump 243, and a reservoir tank 244 in this embodiment.

The power cylinder 241 includes a cylinder 246 separated into two spaces by a piston 245, and the piston 245 moves in the axial direction of the rack shaft 232 by adjusting the oil pressure of oil filled in each of the two spaces. . The piston 245 is connected to the rack shaft 232, and a force in the moving direction is applied to the rack shaft 232 from the piston 245.

The rotary valve 242 is a device that adjusts the hydraulic pressure supplied to each of the two spaces separated by the piston 245. Although the structure of the rotary valve 242 is not particularly limited, in the case of this embodiment, the rotary valve 242 includes a second torsion bar 282 interposed between the pinion shaft 231 and the motor control section 100. The rotary valve 242 supplies the oil pumped from the oil pump 243 to one of the two spaces separated by the piston 245 according to the relative movement between the inner valve and the outer valve caused by the twisting of the second torsion bar 282. The operation of the piston 245 is controlled by adjusting the amount and also by adjusting the amount of surplus oil in the other space that is returned to the reservoir tank 244.

The oil pump 243 is a hydraulic pump whose power source is an engine provided in the vehicle. The oil in the reservoir tank 244 is supplied to the power cylinder 241 by driving the oil pump 243.

The manual operation mechanism 210 is a device that allows the driver to steer the steerable wheels 220 by operating a steering member 211 such as a steering wheel. In the case of this embodiment, as shown in FIG. 1, the manual operation mechanism 210 includes a steering member 211, a shaft member 212, a first torsion bar 281, and a torque detection device 213. Note that the manual operation mechanism 210 may further include a reaction force device, target steering angle detection means, and the like.

The shaft member 212 is a rod-shaped member that is mechanically connected to the steering member 211 and rotates in response to a steering operation on the steering member 211. The shaft member 212 is an example of an input shaft according to the present invention. The manner of connection between the shaft member 212 and the steering mechanism 230 is not particularly limited. In the case of this embodiment, the shaft member 212 is mechanically connected to the pinion shaft 231 via the steering shaft body 111. That is, since the rotation of the shaft member 212 is transmitted to the pinion shaft 231 by the manual operation mechanism 210, the pinion shaft 231 rotates in conjunction with the rotation of the shaft member 212. Thus, the manual operation mechanism 210 is an example of the first transmission mechanism according to the present invention.

The first torsion bar 281 is a member that is interposed in the shaft member 212 and is twisted in response to the torque input when the driver operates the steering member 211 . Torque detection device 213 detects the amount of twist of first torsion bar 281 and outputs steering torque.

The electric motor 110 is a motor that applies a first assist force to the manual operation mechanism 210. Specifically, the electric motor 110 is connected to a shaft member 212 and transmits the rotation of the output shaft of the electric motor 110 to the shaft member 212. The force applied from the electric motor 110 to the shaft member 212 is the first assist force, and is the steering force (motor steering force) applied by the electric motor 110 to the steering mechanism 230.

[Motor control section]
FIG. 2 is a block diagram showing the functional configuration of the motor control section according to the embodiment. The motor control unit 100 is a part that controls the electric motor 110 according to a target steering angle, and is one of ECUs (Electronic Control Units). The motor control unit 100 includes an actual steering angle acquisition unit 130, a target steering angle acquisition unit 131, and a control unit 132 as processing units realized by executing a program.

The actual steering angle acquisition unit 130 acquires the actual steering angle of the steered wheels 220. In the case of the present embodiment, the actual steering angle acquisition unit 130 acquires the actual steering angle based on a signal output by a sensor attached to the steered wheels 220, a link mechanism for steering the steered wheels 220, or the like.

The target steering angle acquisition unit 131 acquires a target steering angle for steering the steered wheels 220. In the case of this embodiment, the target steering angle acquisition section 131 acquires the target steering angle from a target steering angle detection means provided in the manual operation mechanism 210. The target steering angle detection means is a device that detects the steering angle (rotation angle) of the steering member 211 and outputs it as a target steering angle. For example, the target steering angle detection means detects the rotation of the shaft member 212 as the rotation of the steering member 211. The type of target steering angle detection means is not particularly limited, but includes, for example, a resolver attached to the electric motor 110, a rotary encoder, a main gear that rotates together with the shaft member 212, and two driven gears with different diameters that mesh with the main gear. An example is a device that is equipped with a gear and can detect not only the rotation angle but also the rotation direction of the output shaft by detecting the rotation of a permanent magnet provided in each driven gear using a Hall element or the like.

The control unit 132 controls the actual steering angle of the steered wheels 220 to match the target steering angle based on the target steering angle acquired by the target steering angle acquisition unit 131 and the actual steering angle acquired by the actual steering angle acquisition unit 130. The electric motor 110 is controlled accordingly. In the case of this embodiment, electric motor 110 is supplied with electric power by PWM inverter 260 including a plurality of switching elements. The control unit 132 generates a target torque for controlling the electric motor 110 as a motor control value according to the difference between the target steering angle and the actual steering angle. PID control is generally used to generate the target torque. Specifically, the term of the difference between the target steering angle and the actual steering angle, the integral term of the difference, and the differential term of the difference are respectively multiplied by a proportional gain, an integral gain, and a differential gain, and then these terms are added. By doing so, the target torque is calculated as a motor control value.

[Handle return control]
Here, the control unit 132 executes handle return control in order to return the steered steering member 211 to the reference position (neutral position) after the steering. Specifically, during handle return control, the control unit 132 controls the hydraulic return torque caused by the oil pressure among the return torque for returning the steering member 211 to the reference position based on the flow rate information regarding the flow rate of the oil pump 243. In addition, the return torque is estimated based on the vehicle speed of the vehicle and the steering angular velocity of the steering member 211. After that, the control unit 132 controls the electric motor 110 based on the difference between the return torque and the hydraulic pressure return torque (motor return torque).

FIG. 3 is a block diagram showing functional units related to return control in the control unit 132 according to the embodiment. The control unit 132 includes a return torque estimation unit 133, a hydraulic return torque estimation unit 134, and a motor control value generation unit 135.

The return torque estimation unit 133 estimates the return torque based on the vehicle speed, the steering angle of the steering member 211, and the steering torque. Specifically, the return torque estimation unit 133 acquires the vehicle speed from the vehicle speed sensor. The return torque estimation unit 133 acquires the steering torque from the torque detection device 213. The return torque estimation unit 133 acquires the steering angle (rotation angle) of the steering member 211 detected by the target steering angle detection means.

The return torque estimation unit 133 calculates a plurality of MAPs (target steering angle MAP, return torque MAP, vehicle speed gain MAP, torque gain MAP) for estimating return torque from the acquired vehicle speed, steering angle, and steering torque. I remember.

FIG. 4 is an explanatory diagram showing an example of the target steering angle MAP according to the embodiment. As shown in FIG. 4, the target steering angle MAP is a MAP for estimating the target steering angular velocity from the vehicle speed and the steering angle. Examples of the target steering angle MAP include a MAP for a vehicle speed of 0 km/h, a MAP for a vehicle speed of 20 km/h, a MAP for a vehicle speed of 80 km/h, and a MAP for a vehicle speed of 140 km/h. For example, the return torque estimation unit 133 selects the MAP closest to the vehicle speed acquired from the vehicle speed sensor, and estimates the target point steering angle based on the steering angle acquired at that time. Note that other vehicle speeds may be mapped in the target steering angle MAP.

FIG. 5 is an explanatory diagram showing the return torque MAP according to the embodiment. As shown in FIG. 5, the return torque MAP is a MAP for estimating the return torque based on the target steering angular velocity. The return torque estimation unit 133 estimates the return torque based on the target steering angular velocity estimated based on FIG. 4 and the return torque MAP. The estimated return torque here is the reference return torque.

FIG. 6 is an explanatory diagram showing a vehicle speed gain MAP according to the embodiment. As shown in FIG. 6, the vehicle speed gain MAP is a MAP for estimating the vehicle speed gain based on the vehicle speed of the vehicle. The return torque estimation unit 133 determines a vehicle speed gain based on the vehicle speed of the vehicle and the vehicle speed gain MAP, and integrates it into the reference return torque.

Here, the vehicle speed gain MAP is a MAP for reducing the return torque when the vehicle speed is smaller than a certain value (10 km/h in this embodiment). That is, when the vehicle speed gain is determined to be a value smaller than 1, the value is integrated into the reference return torque, so the return torque is reduced compared to the reference return torque. If the steering member 211 is returned to the reference position with a large return torque when the vehicle speed is lower than a certain value, there is a possibility that the driver will feel uncomfortable. If the return torque is determined by integrating the vehicle speed gain with the reference return torque, it becomes possible to perform steering wheel return control with less discomfort.

FIG. 7 is an explanatory diagram showing the torque gain MAP according to the embodiment. As shown in FIG. 7, the torque gain MAP is a MAP for estimating the torque gain based on the steering torque. The return torque estimating unit 133 determines a torque gain based on the steering torque and the torque gain MAP, and integrates it into the reference return torque (or the reference return torque obtained by integrating the vehicle speed torque).

Here, the torque gain MAP is a MAP for reducing the return torque when the steering torque is larger than a certain value (1 Nm in this embodiment). That is, when the torque gain is determined to be a value smaller than 1, the value is integrated into the reference return torque, so that the return torque is reduced compared to the reference return torque. When the driver operates the steering member 211 and the steering torque becomes larger than a certain value, if a large return torque is applied, there is a possibility that the driver will feel uncomfortable. If the return torque is determined by integrating the torque gain with the reference return torque, it becomes possible to perform steering wheel return control with less discomfort.

As shown in FIG. 3, the hydraulic pressure return torque estimation unit 134 estimates the hydraulic pressure return torque caused by the hydraulic pressure of the oil pump 243 based on flow rate information regarding the flow rate of the oil pump 243. Specifically, the oil pressure return torque estimation unit 134 acquires the engine rotation speed from a rotation speed sensor provided in the engine of the vehicle. There is a relationship between the flow rate of the oil pump 243 and the rotation speed of the engine such that the flow rate increases in proportion to the rotation speed. Therefore, the engine rotation speed can be used as flow rate information without directly detecting the flow rate of the oil pump 243.

Further, the hydraulic pressure return torque estimation unit 134 obtains the steering angle of the steering member 211 detected by the steering angle detection means, and calculates the steering angular velocity by differentiating the steering angle with respect to time. Note that if the manual operation mechanism 210 is provided with a steering angular velocity sensor that directly detects the steering angular velocity, the hydraulic pressure return torque estimation unit 134 may acquire the steering angular velocity from the steering angular velocity sensor.

The hydraulic pressure return torque estimation unit 134 stores a hydraulic pressure return torque MAP for estimating the hydraulic pressure return torque from the acquired flow rate information and steering angular velocity.

FIG. 8 is an explanatory diagram showing an example of the hydraulic return torque MAP according to the embodiment. As shown in FIG. 8, the hydraulic pressure return torque MAP is a MAP for estimating the hydraulic pressure return torque from the flow rate information (engine speed) and the steering angular velocity. In this hydraulic return torque MAP, 0-1000rpm MAP, 1001-2000rpm MAP, 2001-3000rpm MAP, 3001-4000rpm MAP, 4001-5000rpm MAP, 5001-6000rpm MAP, 6001-7000rpm MAP ,7001 -MAP of 8000 rpm and MAP of 8000 rpm or more are listed. For example, the hydraulic pressure return torque estimating unit 134 selects a MAP that includes the rotation speed acquired from the rotation speed sensor, and estimates the hydraulic pressure return torque based on the steering angular velocity acquired at that time.

As shown in FIG. 3, the difference between the return torque estimated by the return torque estimation section 133 and the hydraulic pressure return torque estimated by the hydraulic pressure return torque estimation section 134 is input to the motor control value generation section 135. This difference is a value excluding the influence of the hydraulic return torque.

The motor control value generation unit 135 calculates a control value (current command value) for controlling the electric motor 110 based on the obtained difference. As a result, the obtained control value is input to PWM inverter 260 and electric motor 110 is driven. Thereby, the electric motor 110 can be controlled while excluding the influence of the hydraulic pressure return torque.

[Effects etc.]
As described above, according to the present embodiment, in the handle return control, the electric motor 110 is controlled based on the difference between the return torque and the hydraulic return torque. 110 can be controlled. Fluctuations in the flow rate of the oil pump 243 are reflected in the hydraulic pressure return torque, but since the influence of this hydraulic pressure return torque is excluded in the handle return control, the fluctuations in the flow rate are not easily affected. Therefore, it is possible to improve the stability of handle return control.

Further, since the hydraulic pressure return torque estimation unit 134 estimates the hydraulic pressure return torque using the engine rotation speed as flow rate information, the hydraulic pressure return torque can be estimated without using a flow sensor that detects the flow rate of the oil pump 243. . Therefore, it is possible to reduce the manufacturing cost of the steering device 200.

Further, the return torque estimation unit 134 integrates a torque gain based on the steering torque of the steering member 211 with respect to a value (reference return torque) determined based on the vehicle speed of the vehicle and the steering angle of the steering member 211. Since the return torque is estimated by , it is possible to perform steering wheel return control with less discomfort caused by the steering torque.

In addition, the return torque estimation unit 134 estimates the return torque by integrating the vehicle speed gain based on the vehicle speed with respect to the value (reference return torque) obtained based on the vehicle speed of the vehicle and the steering angle of the steering member 211. This makes it possible to perform steering wheel return control with less discomfort caused by vehicle speed.

[others]
Note that the present invention is not limited to the above embodiments. For example, the embodiments of the present invention may be realized by arbitrarily combining the components described in this specification or by excluding some of the components. The present invention also includes modifications obtained by making various modifications to the above-described embodiments that a person skilled in the art can conceive without departing from the gist of the present invention, that is, the meaning of the words written in the claims. It will be done.

For example, in the above embodiment, the engine rotation speed is used as the flow rate information. However, it is also possible to employ the flow rate of the oil pump 243 as the flow rate information. FIG. 9 is a diagram schematically showing a steering device according to a modification. Specifically, FIG. 9 is a diagram corresponding to FIG. 1. In the following description, parts that are the same as those in the embodiment described above may be denoted by the same reference numerals, and the description thereof may be omitted.

As shown in FIG. 9, the steering device 200A according to the modification is provided with a flow rate sensor 290a that directly detects the flow rate of the oil pump 243 on the path of the oil pumped by the oil pump 243. . The flow rate detected by this flow rate sensor 290a is used as flow rate information. Specifically, the flow rate detected by the flow rate sensor 290a is input to the hydraulic pressure return torque estimation section 134. In this case, the hydraulic return torque estimating unit 134 stores a hydraulic pressure return torque MAP for estimating the hydraulic pressure return torque from the obtained flow rate and steering angular velocity. The hydraulic return torque is estimated based on the angular velocity. In other words, since the flow rate of the oil pump 243 is directly used, it is possible to estimate the hydraulic pressure return torque more accurately than when the flow rate is estimated from other parameters (for example, engine rotation speed). Therefore, the stability of handle return control can be further improved.

Further, in the embodiment described above, the case where various estimations are performed using each MAP shown in FIGS. 4 to 8 has been exemplified. However, each MAP is just an example. That is, each MAP may be set by various experiments, simulations, empirical rules, etc. so as to adapt to various parameters, usage conditions, etc. of the steering device. Furthermore, it is also possible to perform each estimation using mathematical formulas, etc., without using MAP.

INDUSTRIAL APPLICATION This invention can be utilized for the steering device which provides assist force by a hydraulic mechanism and an electric motor.

DESCRIPTION OF SYMBOLS 100... Motor control part, 110... Electric motor, 111... Steering shaft body, 130... Actual steering angle acquisition part, 131... Target steering angle acquisition part, 132... Control part, 133... Return torque estimation part, 134... Hydraulic pressure return torque Estimation unit, 135...Motor control value generation unit, 200, 200A...Steering device, 210...Manual operation mechanism (first transmission mechanism), 211...Steering member, 212...Shaft member (input shaft), 213...Torque detection device, 220... Steered wheel, 230... Steering mechanism (second transmission mechanism), 231... Pinion shaft (output shaft), 232... Rack shaft, 233... Tie rod, 240... Hydraulic mechanism, 241... Power cylinder, 242... Rotary valve, 243... Oil pump, 244... Reservoir tank, 245... Piston, 246... Cylinder, 260... Inverter, 281... First torsion bar, 282... Second torsion bar, 290a... Flow rate sensor

Claims (5)

an input shaft that is connected to a steering member and rotates in response to a steering operation on the steering member;
an output shaft that rotates in conjunction with the rotation of the input shaft;
a first transmission mechanism that transmits rotation of the input shaft to an output shaft;
a second transmission mechanism that transmits rotation of the output shaft to steered wheels;
an electric motor that applies a first assist force to the first transmission mechanism;
a hydraulic mechanism having an oil pump whose power source is an engine included in a vehicle, and applying the power of the oil pump to the second transmission mechanism as a second assist force;
a motor control unit that controls the electric motor;
The motor control section includes:
Of the return torque for returning the steering member to the reference position, the hydraulic return torque caused by the oil pressure is estimated based on flow rate information regarding the flow rate of the oil pump and the steering angular velocity of the steering member, and the Estimating the return torque based on the vehicle speed of the vehicle and the steering angle of the steering member,
A steering device that controls the electric motor based on a difference between the return torque and the hydraulic return torque. The steering device according to claim 1, wherein the motor control unit estimates the hydraulic pressure return torque using the rotation speed of the engine as the flow rate information. comprising a flow rate sensor that detects the flow rate of the oil pump,
The steering device according to claim 1, wherein the motor control unit estimates the hydraulic pressure return torque using a detection result of the flow rate sensor as the flow rate information. The motor control unit estimates the return torque by integrating a torque gain based on the steering torque of the steering member with respect to a value determined based on the vehicle speed of the vehicle and the steering angle of the steering member. The steering device according to any one of claims 1 to 3. The motor control unit estimates the return torque by integrating a vehicle speed gain based on the vehicle speed with respect to a value determined based on the vehicle speed of the vehicle and the steering angle of the steering member. 4. The steering device according to any one of 4.

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