LINK SYSTEM

Abstract

Steering system installed in a vehicle (10) comprising: a steering actuation element (30) to be operated by a driver; a steering shaft (34) coupled to the steering actuation element (30) and designed to rotate in accordance with an actuation of the steering actuation element (30); a sensor (112) for detecting an actuation amount of the steering actuation element (30); a steering mechanism (38) comprising a steering element (36) coupled to a wheel (12) and designed to cause the steering element (36) to move in accordance with the rotation of the steering shaft (34) in order to enable the wheel (12) to turn in accordance with a movement of the steering element (36); an actuation support device (100) designed to exert a torque on the steering shaft (34) in order to assist the actuation of the steering actuation element (30). support; a steering support device (70),comprising a working fluid supply device (80) for supplying a working fluid and a flow rate adjustment mechanism (96) for adjusting a supply flow rate, which is a flow rate of the working fluid supplied by the working fluid supply device (80), wherein the steering support device (70) is designed to assist the movement of the steering element (36) of the steering mechanism (38) using the working fluid supplied by the working fluid supply device (80); and a control unit (110) for controlling the torque exerted on the steering shaft (34) by the actuating support device (100) and for controlling the flow rate adjustment mechanism (96) of the steering support device (70) in order to control the supply flow rate of the working fluid, wherein the steering support device (70) is designed to assist the movement of the steering element (36) with an assisting force,which depends on the supply flow rate of the working fluid, characterized in that: the control unit (110) is designed to identify an actuation speed of the steering actuation element (30) based on the amount of actuation of the steering actuation element (30) detected by the sensor (112) and to increase the supply flow rate of the working fluid from a momentarily set low flow rate to a set high flow rate when the actuation speed of the steering actuation element (30) becomes equal to or higher than a set threshold speed, wherein the control unit (110) is designed to control the torque exerted by the actuation support device (100) based on a sum of an actuation torque-dependent component (TA-TO), an actuation speed-dependent component (TA-R) and an actuation angle-dependent component (TA-θ).

Description

BACKGROUND Technical area

[0001] The following disclosure relates to a steering system installed in a vehicle. Description of the state of the art

[0002] An ordinary steering system installed in a vehicle comprises (a) a steering actuation element operated by a driver, (b) a steering shaft coupled to the steering actuation element and designed to rotate in accordance with an actuation of the steering actuation element, and (c) a steering mechanism with a steering element coupled to a wheel and designed to cause the steering element to rotate in accordance with a rotation of the steering shaft, thus enabling steering or turning of the wheel in accordance with a movement of the steering element. It has been proposed that such a steering system further comprises two support devices, as described, for example, in Patent 1 (Japanese Patent Publication No.2014-51263), in particular (d) an actuation support device designed to apply a torque to the steering shaft and thus assist the actuation of the steering actuation element, and (e) a steering support device comprising a working fluid supply device for supplying a working fluid and designed to assist the movement of the steering element of the steering mechanism using the working fluid supplied by the working fluid supply device. SUMMARY

[0003] In the steering system described in patent specification 1, a torque exerted on the steering shaft by the actuating support device (hereinafter referred to as the "support torque" where appropriate) and a support force for assisting the movement of the steering element are cooperatively controlled based on the amount of actuation of the steering actuating element and the vehicle's speed. Even when the cooperative control is executed, the steering or turning of the wheel is expected to be delayed with respect to the actuation of the steering actuating element if the actuation speed of the steering actuating element is high.If the steering assist device is designed to support the movement of the steering element with an assist force that depends on a supply flow rate, which is the flow rate of the working fluid supplied by the working fluid supply device, then a delay in steering or turning is less likely to occur if the supply flow rate is constantly maintained at a high level. However, maintaining a constantly high supply flow rate undesirably increases the energy consumption for supplying the working fluid considerably. Thus, a solution to this problem leads to an improvement in the utility of the steering system comprising the two assist devices. Consequently, one aspect of the present disclosure is directed toward a steering system with high utility.

[0004] The steering system according to one aspect of the present disclosure comprises a steering assistance device for supporting a steering element with an assistance force that depends on a supply flow rate of a working fluid. In the steering system, the supply flow rate of the working fluid is increased when the actuation speed of the steering actuation element becomes equal to or greater than a set threshold speed.

[0005] In the steering system constructed as described above, steering delay can be prevented by increasing the supply flow rate of the working fluid supplied by the working fluid supply device of the steering assist device when the actuation speed of the steering actuation element is relatively high, and the energy consumption of the working fluid supply device of the steering assist device can be kept low by decreasing the supply flow rate when the actuation speed of the steering actuation element is relatively low. VARIOUS FORMS

[0006] A steering system according to a basic form of the present disclosure is a steering system installed in a vehicle, comprising: a steering control element to be operated by a driver; a steering shaft coupled to the steering actuation element and designed to rotate in accordance with an actuation of the steering actuation element; a steering mechanism comprising a steering element coupled to a wheel and designed to cause the steering element to move in accordance with the rotation of the steering shaft, thus enabling steering or turning of the wheel in accordance with a movement of the steering element; an actuation support device designed to exert a torque on the steering shaft in order to assist the actuation of the steering actuation element; a steering assistance device comprising a working fluid supply device for supplying a working fluid and a flow rate adjustment mechanism for adjusting a supply flow rate, which is a flow rate of the working fluid supplied by the working fluid supply device, wherein the steering assistance device is designed to assist the movement of the steering element of the steering mechanism using the working fluid supplied by the working fluid supply device; and a control unit for controlling the torque exerted on the steering shaft by the actuating support device and for controlling the flow rate adjustment mechanism of the steering support device in order to control the supply flow rate of the working fluid, wherein the steering support device is designed to assist the movement of the steering element with a support force that depends on the supply flow rate of the working fluid, and wherein the control unit is designed to increase the supply flow rate of the working fluid when an actuation speed of the steering actuation element becomes equal to or higher than a set threshold speed.

[0007] In the basic steering system, the "steering actuation element" is, for example, a steering wheel. If the steering actuation element is a steering wheel, the actuation force can be considered as a rotation angle of the steering wheel, that is, an actuation angle of the steering wheel. The "steering shaft" connects or couples the steering actuation element to the steering mechanism. The steering shaft is held to a vehicle body, for example, by a steering column. Various types of "steering mechanisms" can be used.For example, a rack and pinion mechanism can be used as the steering mechanism, comprising: a pinion shaft, which includes a pinion and acts as the input shaft, coupled to the steering shaft and designed to be rotated by a torque exerted by the steering shaft; and a rack drive, which connects a left and a right wheel and includes a rack in meshing engagement with the pinion, the rack drive serving as the steering element, designed to be moved by the rotation of the input shaft and thus turning the wheels.

[0008] The "steering assistance device," as one of the two assistance devices, is a device for assisting the movement of the steering element using the working fluid, thereby supporting the steering or turning of the wheel. That is to say, the steering assistance device can be the one used in a conventional hydraulic power steering system. The present steering assistance device supports the movement of the steering element, given the possibility that adequate steering may not be performed, solely by means of a force exerted by a driver on the steering actuation element. This force is hereinafter referred to as the "actuation force" where appropriate. The steering assistance device can be designed to exert the assistance force on the steering element.Alternatively, if the steering mechanism includes the input shaft described above, the power steering device can be designed to exert the assisting force on the input shaft in the form of a torque. That is, the power steering device is designed to assist the movement of the steering element directly or indirectly.

[0009] If the steering assist device includes the input shaft described above, the steering assist device is preferably designed to exert the assist force corresponding to a steering torque, which is a torque exerted by the steering shaft on the input shaft. In particular, if the steering assist device includes the input shaft and an actuator designed to receive the working fluid and exert the assist force on the steering element, a torsion bar may be arranged between the input shaft and the steering shaft, and a valve mechanism may be provided designed to adjust the flow rate of the working fluid received by the actuator in accordance with the degree of twist of the torsion bar, so that the steering device can be designed to exert the assist force corresponding to the steering torque.

[0010] The working fluid supply device of the power steering system is, for example, a pump. The pump can be an electric pump driven by an electric motor, or it can be a motor pump driven by the vehicle's internal combustion engine. The motor pump is very reliable and is frequently used in power steering systems. Thus, the use of the motor pump allows the steering system of the present disclosure to be applied to an ordinary power steering system. When the motor pump is used, the supply flow rate of the working fluid can be reduced, unless the actuation speed of the steering actuator is relatively high, which reduces the load on the internal combustion engine.Therefore, when the engine pump is used, the steering system of the present disclosure contributes significantly to increasing the vehicle's fuel efficiency.

[0011] The flow rate adjustment mechanism of the power steering device may include an electromagnetic valve or valves, and the control unit may control the electromagnetic valve or valves to adjust the flow rate of the working fluid supplied by the working fluid supply device. The flow rate adjustment mechanism is preferably designed such that the load on the working fluid supply device is low when the supply flow rate is low, while the load on the working fluid supply device is high when the supply flow rate is high. It should be noted that the working fluid flow rate generally refers to the quantity of working fluid flowing per unit time.

[0012] The control of the flow rate adjustment mechanism by the control unit is explained below. The supply flow rate of the working fluid is controlled to increase when the actuation speed of the steering actuator becomes equal to or greater than the set threshold speed. The actuation speed of the steering actuator is referred to simply as the "actuation speed" where appropriate. When the actuation speed is relatively low, the steering mechanism can adequately follow the steering actuator's action, and the load on the working fluid supply device is minimized by keeping the supply flow rate low. Conversely, when the actuation speed is relatively high, it is highly likely that the steering or turning of the wheel will be affected.The steering mechanism cannot follow the steering input of the steering actuator when the wheel is turned. In this case, the assisting force that can prevent or reduce steering lag is obtained by increasing the supply flow rate. By changing the load on the working fluid supply device based on the steering actuator's actuation speed, steering lag can be prevented or reduced, while minimizing the energy consumption of the working fluid supply device and thus reducing the vehicle's fuel consumption, in the case where the working fluid supply device is the engine pump.

[0013] The following is a detailed explanation of a method for increasing the supply flow rate when the actuation speed is equal to or higher than the set threshold speed. At the point when the actuation speed equals the set threshold speed, the supply flow rate of the working fluid can be increased immediately from the currently set low flow rate to the set high flow rate. Alternatively, the supply flow rate of the working fluid can be increased gradually or continuously from the set low flow rate to the set high flow rate, depending on the magnitude of the actuation speed, from the point at which the actuation speed equals the set threshold speed.

[0014] The "actuation support device," the second of the two support devices, is designed to apply torque, i.e., the support torque, to the steering shaft, thereby reducing the driver's effort required for steering and improving the driver's perceived steering feel. By positively applying the support torque, the actuation support device enables the steering system to execute steering actions that are independent of the driver. For example, the actuation support device allows the steering system to execute steering actions in accordance with a request from the vehicle's self-driving system, a request from a driving assistance system to keep the vehicle in a lane, or similar requests.The assist torque exerted by the steering assist device is not limited to a torque in one direction to assist the driver's steering input. In some cases, the assist torque exerted by the steering assist device can be a torque in a direction opposing the steering input made by the driver; that is, the assist torque can be a counter-torque, which can also be referred to as a "counterforce (reaction force) torque".

[0015] The source for generating the assist torque exerted by the actuation support device is not limited to a specific one. For example, the actuation support device can include an electric motor as the source for generating the assist torque. Using an electric motor as the source for generating the assist torque results in an actuation support device design with excellent responsiveness, which further improves the actuation feel perceived by the rider.

[0016] From the perspective of reducing the driver's workload for steering, the steering assist device is preferably designed to exert a supporting torque on the steering shaft that corresponds to an actuating torque, and the control unit is preferably designed to control the steering assist device so that it exerts such a supporting torque. If the steering assist device includes the electric motor as the source for generating the supporting torque, the control unit can be designed to control an electric current supplied to the electric motor and thus control the supporting torque. The present steering system can include a sensor for detecting the actuating torque, which is a torque exerted on the steering shaft by actuating the steering actuator, i.e., an actuating torque sensor.If the steering actuation element is the steering wheel, a torsion bar may be arranged between the steering wheel and the steering shaft, and the actuation torque sensor may be designed to detect the degree of twisting of the torsion bar and thus the actuation torque.

[0017] The following explains how the control unit controls the steering assist device, specifically the control of the assist torque. The control unit can, for example, control the assist torque based on the actuation speed of the steering linkage.

[0018] Furthermore, the control unit can control the support torque based on the amount of actuation of the steering actuation element, in other words based on the actuation angle of the steering wheel, if the steering actuation element is the steering wheel.

[0019] Furthermore, the control unit can regulate the assistance torque based on the vehicle's speed. In this case, the actuating assistance device can be controlled so that the assistance torque decreases as the vehicle's speed increases.

[0020] In other words, the steering assist torque is controlled based on at least one parameter, such as the actuation speed of the steering element, the amount of steering input, and the vehicle's speed, thus providing the driver with a better feel for the steering. The steering assist torque can be controlled based on one parameter or on multiple parameters. When controlled based on multiple parameters, it can be precisely controlled by determining the components of the steering assist torque that relate to each parameter and then adding these components together.

[0021] The term "control unit" can refer to an electronic control unit with a computer as a primary component, as well as a control circuit for the actuation support device and a control circuit for the flow rate adjustment mechanism of the power steering device. The control unit can be a single electronic control unit designed to control both the actuation support device and the flow rate adjustment mechanism of the power steering device. Alternatively, the control unit can consist of two electronic control units, each containing a computer. In other words, the control unit can comprise one electronic control unit for controlling the actuation support device and one electronic control unit for controlling the flow rate adjustment mechanism of the power steering device. List of characters

[0022] The objectives, features and advantages, as well as the technical and industrial significance of the present disclosure, will be better understood by reading the following detailed description of an embodiment in conjunction with the accompanying drawings, in which: Fig. 1 is a view that schematically shows an overall structure of a steering system according to one embodiment; Fig. 2A is a diagram which, according to the embodiment, shows an enhancement for determining an actuation torque-dependent component as one of three components of an assist torque exerted by an actuation support device of the steering system; Fig. 2B is a diagram which, according to the embodiment, shows an enhancement for determining an actuation-speed-dependent component as one of the three components of the support torque exerted by the actuation support device of the steering system; Fig. 2C is a diagram which, according to the embodiment, shows a reinforcement for determining an actuation-angle-dependent component as yet another of the three components of the support torque exerted by the actuation support device of the steering system; and Fig. 3 is a flowchart of a control program executed in the steering system of the embodiment. DETAILED DESCRIPTION OF THE EXECUTION FORM

[0023] The following section, with reference to the drawings, describes in detail a steering system according to one embodiment of the present disclosure. It is understood that the present disclosure is not limited to the details of the following embodiment, but can be embodied on the basis of the forms described in "Various Forms" and can be altered and modified based on the knowledge of the person skilled in the art in the field. Steering system hardware configuration

[0024] As it is in Fig. As shown in 1, a vehicle includes 10 , in which a steering system according to an embodiment is installed, two front wheels 12 , each as a steerable wheel and as a drive wheel. The vehicle 10 includes an internal combustion engine 14 as a power source. A rotation of the internal combustion engine 14 is via a torque converter / transmission 16 , a differential 18and respective drive shafts 20R , 20L on each of the front wheels 12 , each by a respective axle stub 22a be held, transferred. The vehicle 10 drives through the rotation of the front wheels 12 .

[0025] The steering system according to the present embodiment comprises (a) a steering wheel 30 as a steering actuation element that is operated by a driver, (b) a steering shaft 34 , which is connected to a steering column 32 is held and one end of which is connected to the steering wheel 30 is coupled in such a way that it aligns itself with an operation of the steering wheel. 30 rotates, and (c) a steering mechanism 38 , which is a tie rod 36 as a steering element, the opposite ends of which are each connected to one of the front wheels. 12 are coupled and extend in the width direction of the vehicle, with the steering mechanism38 is designed to fit the tie rod 36 in accordance with a rotation of the steering shaft 34 to move and thus cause the front wheels to turn 12 in accordance with a movement of the tie rod 36 to enable.

[0026] The steering mechanism 38 includes an input wave 42 , with which the further end of the steering shaft 34 is coupled and is connected by a gearbox housing 40 is held. A pinion is attached to a section of the input shaft. 42 formed, which is located in the gearbox housing 40 The tie rod is located. 36 is also through the gearbox housing 40 held, and a rack 44 , which is in meshing engagement with the pinion, is on the tie rod 36 formed. That is, the steering mechanism. 38It includes a rack and pinion motion conversion mechanism. A rotation of the steering shaft. 34 causes a rotation of the input shaft 42 , so that the tie rod 36 moves in the direction of the vehicle's width. The tie rod 36 is equipped with a track lever at each of its opposite ends 48 of the respective axle stub 22 coupled, which connects the left or right front wheel 12 via respective connecting rods 46 hold. The front wheels 12 are caused by the movement of the tie rod 36 steered or turned.

[0027] One end of the steering shaft 34 is via a first torsion bar 60 with the steering wheel 30 coupled. The steering column 32 includes an actuation torque sensor 62 to capture the degree of twisting of the first torsion bar 60and detecting movement by operating the steering wheel 30 on the steering shaft 34 The applied torque. This torque is subsequently referred to as the "actuating torque" where appropriate. In this context, the operating torque can be considered as a torque that the driver applies to the steering wheel by turning it. 30 exerts its influence. The further end of the steering shaft 34 is via a second torsion bar 64 with the input wave 42 the steering mechanism 38 coupled. One strength of the twist of the second torsion bar. 64 This corresponds to a steering shaft 34 on the input wave 42 The applied torque. This torque is subsequently referred to as "steering torque" where appropriate.

[0028] The steering system includes a steering assist device. 70 to support the movement of the tie rod 36 the steering mechanism38 using a working fluid (working oil). The power steering device 70 includes a hydraulic actuator 78 with a piston 72 , which is attached to the tie rod 36 is attached, and a housing 76 , whose interior is encircled by the piston 72 in two fluid chambers 74R , 74L is divided. The steering assist device 70 also includes a motor pump 80 as a working fluid supply device powered by the internal combustion engine 14 is driven. The motor pump 80 pumps the working fluid from a reservoir 82 , in which the working fluid is stored, via a pumping channel 84 up and directs the pumped working fluid via a feed channel. 86 the supply current control mechanism 88 to.

[0029] The supply current control mechanism 88has a common, familiar structure, as can be seen, for example, in Fig. 2 of Japanese Patent Publication No. 6-8840. In particular, the feed current control mechanism 88 a function for controlling the flow rate of the actuator 78 working fluids to be supplied and a function to determine which of the two fluid chambers 74R , 74L The working fluid is to be supplied based on the strength of the twist of the second torsion bar. 64 and the direction of rotation, that is, based on the steering torque and the steering direction. The supply current control mechanism 88 is designed to handle the motor pump 80 to absorb the supplied working fluid. If no steering torque is applied to the input shaft 42 The effect is made possible by the supply current control mechanism. 88 that the absorbed working fluid is routed via a return channel 90to the reservoir 82 is returned. That is, the working fluid is circulated. However, if a steering torque is applied to the input shaft... 42 The supply current control mechanism takes effect. 88 at least a portion of the absorbed working fluid at a flow rate corresponding to the steering torque, one of the two fluid chambers 74R , 74L of the actor 78 to, which corresponds to the steering direction, and takes from the other of the two fluid chambers 74R , 74L The working fluid is drawn in at the same flow rate as the supplied working fluid. The supply flow control mechanism 88 This allows the fluid from the other of the two fluid chambers to also be used. 74R , 74L absorbed working fluid to the reservoir 82 is traced back. In the actor 78 A force acts which corresponds to the pressure exerted by the supply current control mechanism. 88one of the two fluid chambers 74R , 74L supplied working fluids corresponds to the piston 72 , so that the force (hereinafter referred to as the "assisting force" where appropriate) assists a steering force, which is a force by which the tie rod 36 the front wheels 12 impacts. In other words, the power steering device 70 is designed to control the movement of the tie rod 36 to provide support with a force that corresponds to the steering torque.

[0030] The motor pump 80 is designed to expel the working fluid at a flow rate that corresponds to the rotational speed of the internal combustion engine. 14 corresponds. The steering assist device 70 includes a flow rate limiting mechanism 92 , which is located on one discharge side of the motor pump 80 is arranged to increase the flow rate of the water from the motor pump 80to limit the ejected working fluids. The flow rate limitation mechanism 92 It has a known, conventional structure with a valve, as described, for example, in Japanese Patent No. 3218788, Japanese Patent Publication No. 8-301132, or Japanese Patent Publication No. 6-8840. In particular, the flow rate limiting mechanism 92 a function for limiting the flow rate of the working fluid supplied to the supply flow control mechanism 88 to be supplied at a set flow rate, after it has passed through there, when the rotational speed of the internal combustion engine 14 has increased to a certain rotational speed. Furthermore, the steering assist device includes 70 a flow rate control mechanism 94 , which is located on an ejection side of the flow rate limiting mechanism 92and is arranged in series with it and is designed to reduce the flow rate of the flow rate limiting mechanism 92 the supply current control mechanism 88 to control the supplied working fluids. The flow rate control mechanism 94 is a well-known, common electromagnetic valve mechanism, such as those found in Fig. Figure 2 of Japanese Patent Publication No. 2014-19290 shows the flow rate control mechanism. 94 Its function is to allow the passage of the working fluid at a flow rate corresponding to an electric current supplied to a solenoid. The power steering device 70 includes a mechanism that is controlled by the flow rate limitation mechanism 92 and the flow rate control mechanism 94 is formed, that is, a flow rate adjustment mechanism 96to adjust the flow rate of the motor pump 80 the supply current control mechanism 88 supplied working fluids. This flow rate is subsequently referred to as the "supply flow rate" where appropriate.

[0031] As can be seen from the explanation above, the steering assist device 70 designed to control the movement of the tie rod 36 to provide support, which depends on the feed flow rate. Generally, the support force increases with an increase in the feed flow rate and decreases with a decrease in the feed flow rate.

[0032] The steering system also includes an actuation support device. 100 , which is designed to apply torque to the steering shaft 34 to exercise and thus operate the steering wheel 30 to support. The actuation support device 100 includes an electric motor102 as a source for generating the signal on the steering shaft 34 The torque exerted. This torque is subsequently referred to as the "support torque" where appropriate. The torque generated by the electric motor 102 The generated torque is used as the support torque via a reduction gear. 104 on the steering shaft 34 exercised. The electric motor 102 is a brushless three-phase DC motor. The magnitude of the assist torque corresponds to an amount of the electric motor. 102 supplied electrical current. This electrical current is subsequently referred to as "supply current" where appropriate. The assist torque increases with an increase in the supply current and decreases with a decrease in the supply current.

[0033] The steering assist device control 70 and the actuation support device 100in the present steering system, in particular the control of the flow rate control mechanism 94 the flow rate adjustment mechanism 96 and the electric motor 102 , is controlled by an electronic control unit (ECU) 110 implemented as a control unit. The ECU 110 is formed by: a computer as the main component with a CPU, a ROM, a RAM, etc.; a control circuit of the solenoid of the flow rate control mechanism 94 ; and an inverter, which is a control circuit for the electric motor. 102 is. The control circuit of the solenoid of the flow rate control mechanism. 94 The inverter is activated by a command from the computer. The ECU 110 It controls the supply flow rate of the working fluid and the support torque. The steering system is equipped with an actuation angle sensor. 112 to detect the steering wheel's operating angle 30than the actuation amount of the steering actuation element and four wheel speed sensors 114 (only one of them is in Fig. (1 shown), each to detect the rotational speed of a corresponding one of the four wheels, which are the two front wheels 12 include, equipped. The actuation angle sensor 112 , the wheel speed sensors 114 and the actuation torque sensor 62 , which are described above, are connected to the ECU 110 tied together. Steering system control (i) Control of the supply flow rate of the working fluid in the steering support device

[0034] As can be seen from the explanation above, the steering mechanism serves 38 to turn the front wheels 12 in accordance with the steering wheel's operating angle θ 30 to enable, and the steering assist device 70 This serves to ensure a suitable turning of the front wheels. 12by supporting the movement of the tie rod 36 to enable this. In the present steering system, the ECU controls 110 the actuation angle sensor 112 , to adjust the steering wheel's operating angle θ 30 to detect, and identifies an actuation speed dθ / dt of the steering wheel. 30 based on the detected operating angle.

[0035] If the actuation speed dθ / dt of the steering wheel 30 is relatively high, meaning that if the driver makes a relatively quick steering maneuver, the piston moves 72 of the actor 78 quickly, so that the actuator 78 The working fluid must be accommodated at a relatively high flow rate. In view of this, the present steering system is designed such that when the actuation speed dθ / dt becomes equal to or higher than a set threshold speed (dθ / dt)0, the supply flow rate Qof the working fluid equal to a set high flow rate Q H is done, which is set as a relatively high flow rate in order to prevent the flow rate of the fluid passing through the actuator from being affected. 78 The amount of working fluid to be absorbed becomes low.

[0036] In contrast, the piston moves 72 of the actor 78 , if the actuation speed dθ / dt of the steering wheel 30 relatively low, that is, if the driver makes a relatively slow steering input, slowly, so that the flow rate of the fluid passing through the actuator is low. 78 The flow rate of the working fluids to be received does not need to be high. In view of this, the present steering system is designed such that when the actuation speed dθ / dt is lower than the set threshold speed (dθ / dt)0, the supply flow rate Q of the working fluid equal to a set flow rate Q L is done, which is set as a relatively low flow rate in order to reduce the load on the motor pump. 80 to reduce. Reducing the load on the motor pump 80 This leads to a reduction in the load on the combustion engine. 14 , which improves the vehicle's fuel efficiency 10 will be improved.

[0037] As explained above, the feed flow rate Q by changing the solenoid of the flow rate control mechanism 94 The supplied electrical current was changed. ii) Control of the support of the support torque exerted by the actuating support device

[0038] The present steering system includes the actuation support device. 100 Essentially, to give the driver a better feel for the steering wheel. 30to provide feedback that the driver perceives when steering. This is achieved through the steering assistance device. 100 on the steering shaft 34 exerted support moment T A is determined as follows.

[0039] The present steering system uses three components, i.e., a component dependent on the actuation torque. T A-TO , an actuation speed-dependent component T A-R and an actuation angle-dependent component T A-θ , as components that provide the support torque T A These three components, i.e., the actuation torque-dependent component, form a system. T A-TO , the actuation speed-dependent component T A-R and the actuation angle-dependent component T A-θ , are added according to the following equation to determine the amount of power required by the steering shaft 34 support moment to be exerted T A to determine: TA = TA − TO + TA − R + TA − θ

[0040] The actuation torque-dependent component T A-TO is set as a function based on an actuation torque To and a vehicle speed v as parameters, the actuation speed-dependent component T A-R is calculated as a function based on the actuation speed dθ / dt of the steering wheel. 30 and the vehicle's driving speed v is set as a parameter, and the actuation angle-dependent component T A-θ is calculated as a function based on the steering wheel's operating angle θ. 30 and the vehicle's speed v is set as a parameter, as shown below. The actuation torque-dependent component T A-TO , the actuation speed-dependent component T A-R and the actuation angle-dependent component T A-θ are determined according to the respective function. TA − TO = f TO ( To ,v ) TA − R = f R ( d θ / dt ,v ) TA − θ = θ ( θ , v )

[0041] The actuation torque-dependent component changes according to the respective function. T A-TO , the actuation speed-dependent component T A-R and the actuation angle-dependent component T A-θ regarding changes to the relevant parameters, as shown in the diagrams of the Fig. 2A, Fig. 2B or Fig. Figure 2C is shown. The three components are explained in detail below. The actuation torque-dependent component T A-TO is a basic component, that is, a component of the support moment T A to assist steering, in order to reduce the driver's workload for steering. As described in Fig. As shown in 2A, the actuation torque-dependent component T A-TO so determined that the support momentT A The actuation-speed-dependent component increases with an increase in the actuation torque To and decreases with an increase in the vehicle's driving speed v. T A-R is a component that can be considered a damping force with respect to the steering operation. The actuation speed-dependent component T A-R is a component for exerting the support moment T A in one direction opposite to one direction of the actuation torque-dependent component T A-TO This moment of support T A In the opposite direction, the following is a counter-moment. T A referred to as the steering mechanism. As it says in Fig. As shown in Figure 2B, the actuation speed-dependent component T A-R so determined that the counter-moment T A with an increase in the actuation speed dθ / dt of the steering wheel 30increases and increases with an increase in the vehicle's speed v. The actuation angle-dependent component T A-θ is a component that acts as a force to return the steering wheel 30 can be considered in a neutral position. This force is what is known as spring force. Likewise, the actuation-speed-dependent component. T A-R is the actuation angle-dependent component T A-θ a component for exerting the counter-moment T A in the opposite direction to the direction of the actuation torque-dependent component T A-TO As it is in Fig. The component shown in Figure 2C is the actuation angle-dependent component. T A-θ so determined that the counter-moment T A with the increase of the steering wheel's operating angle θ 30 It increases and decreases with an increase in the vehicle's speed v. This determines the sign (±) of the actuation torque-dependent component. T A-TO , the actuation speed-dependent component T A-R and the actuation angle-dependent component T A-θ As far as this is concerned, the sign of the actuation torque-dependent component differs. T A-TO generally depends on the sign of the actuation-speed-dependent component T A-R and the sign of the actuation angle-dependent component T A-θ for a steering actuation, as shown in the diagrams of the Fig. 2A-2C is evident.

[0042] The electric motor 102 the actuation support device 100 is based on the support moment thus determined T A an electric current is supplied to increase the support torque T A on the steering shaft 34 to exert. It should be noted that the actuation torque To is based on the measurement by the actuation torque sensor. 62 is gained, and the steering wheel's operating angle θ30 based on the detection by the actuation angle sensor 112 The actuation speed dθ / dt of the steering wheel is obtained. 30 is based on the obtained steering wheel actuation angle θ 30 The vehicle speed v is identified based on the wheel rotation speeds vw, which are determined by the corresponding wheel speed sensors. 114 They are recorded, each of which is located on one of the four wheels. iii) Control flow

[0043] The ECU computer 110 At short intervals of, for example, a few to several milliseconds, it repeatedly executes a feed rate / support torque control program, which is defined by the flowchart of Fig. 3 is shown, so that the control of the feed flow rate Q of the working fluid in the steering support device 70and the control of the actuation support device 100 exerted support moment T A to be executed. Referring to the flowchart, a process involving two controls is explained below.

[0044] The process according to the program starts with step 1 , in which the ECU 110 the steering wheel's operating angle θ 30 , the wheel rotation speeds vw and that of the steering wheel 30 on the steering shaft 34 applied actuation torque To based on the detection by the actuation angle sensor 112 , the detection by the wheel speed sensors 114 or the detection by the actuation torque sensor 62 wins. Step 1 is known as " S1 “abbreviated, and the subsequent steps are abbreviated accordingly. In S2 identifies the ECU 110 the actuation speed dθ / dt of the steering wheel30 and the vehicle speed v based on the actuation angle θ or the wheel rotation speeds obtained as described above v W .

[0045] In S3 The ECU determines 110 , whether the identified actuation speed dθ / dt is not lower than the set threshold speed (dθ / dt)0. If the actuation speed dθ / dt is not lower than the set threshold speed (dθ / dt)0, the ECU determines 110 in S4 the supply flow rate Q of the working fluid, which is equal to the set high flow rate Q H should be in order to be affected by the steering assist device 70 to increase the applied support force. However, if the actuation speed dθ / dt is lower than the set threshold speed (dθ / dt)0, the ECU determines 110 in S5 the supply flow rate Qof the working fluid, which is equal to the low flow rate setting Q L should be in order to be affected by the steering assist device 70 to keep the level of support exerted to a minimum. In S6 The ECU 110 based on the determined feed flow rate Q the solenoid of the flow rate adjustment mechanism 96 an electric current.

[0046] In S7 The ECU determines 110 the actuation torque-dependent component T A-TO , the actuation speed-dependent component T A-R and the actuation angle-dependent component T A-θ based on the obtained actuation torque To, the obtained actuation angle θ of the steering wheel 30 , the identified actuation speed dθ / dt of the steering wheel 30 and the identified vehicle speed v according to each of the three functions mentioned above. In S8the ECU adds 110 the actuation torque-dependent component T A-TO , the actuation speed-dependent component T A-R and the actuation angle-dependent component T A-θ , in order to achieve this through the actuation support device 100 support moment to be exerted T A to determine.

[0047] In S9 The ECU 110 the electric motor 102 the actuation support device 100 based on the support moment determined as described above T A an electric current is applied. A cycle of the process, according to the control program, is terminated by executing the process described above. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 3218788

[0030] JP 8301132

[0030] JP 68840

[0030]

Claims

[1] Steering system installed in a vehicle and comprising: a steering actuating element (30) to be actuated by a driver; a steering shaft (34) coupled to the steering actuator (30) and configured to rotate in accordance with an actuation of the steering actuator (30); a steering mechanism (38) comprising a steering element (36) coupled to a wheel (12) and configured to cause the steering element (36) to move in accordance with rotation of the steering shaft (34) so as to enable the wheel (12) to turn in accordance with movement of the steering element (36); an operation assist device (100) configured to apply a torque to the steering shaft (34) so as to assist the operation of the steering operating element (30); a steering assist device (70) comprising a working fluid supply device (80) for supplying a working fluid and a flow rate adjusting mechanism (96) for adjusting a supply flow rate, which is a flow rate of the working fluid supplied from the working fluid supply device (80), wherein the steering assist device (70) is designed to assist the movement of the steering element (36) of the steering mechanism (38) using the working fluid supplied from the working fluid supply device (80); and a control device (110) for controlling the torque exerted on the steering shaft (34) by the actuation assist device (100) and for controlling the flow rate adjusting mechanism (96) of the steering assist device (70) so as to control the supply flow rate of the working fluid, wherein the steering assist device (70) is designed to assist the movement of the steering element (36) with an assist force that depends on the supply flow rate of the working fluid, and wherein the controller (110) is configured to increase the supply flow rate of the working fluid when an operating speed of the steering operating element (30) becomes equal to or higher than a set threshold speed. [2] Steering system according to claim 1, wherein the steering mechanism (38) comprises an input shaft (42) to which the steering shaft (34) is coupled and which is rotated by the steering shaft (34), and wherein the steering assist device (70) is designed to assist the movement of the steering element (36) with the assist force corresponding to a steering torque, which is a torque exerted by the steering shaft (34) on the input shaft (42). [3] A steering system according to claim 1 or 2, wherein the steering assist device (70) comprises, as the working fluid supply device, a motor pump (80) adapted to be rotated by an internal combustion engine (14) of the vehicle. [4] A steering system according to any one of claims 1 to 3, wherein the operation assist device (100) comprises an electric motor (102) as a source for generating the torque applied to the steering shaft (34). [5] A steering system according to any one of claims 1 to 4, further comprising an operation torque sensor (62) for detecting an operation torque which is a torque exerted on the steering shaft (34) by the operation of the steering operating member (30), wherein the control device (110) is designed to control the torque exerted on the steering shaft (34) by the operation assist device (100) in accordance with the detected operation torque. [6] Steering system according to one of claims 1 to 5, wherein the control device (110) is designed to control the torque exerted on the steering shaft (34) by the operation assist device (100) based on the operation speed of the steering operation element (30). [7] Steering system according to one of claims 1 to 6, wherein the control device (110) is designed to control the torque exerted on the steering shaft (34) by the operation assist device (100) based on an operation amount of the steering operation member (30). [8] Steering system according to one of claims 1 to 7, wherein the control device (110) is designed to control the torque exerted on the steering shaft (34) by the actuation assist device (100) based on a traveling speed of the vehicle.

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