JPH04325376A - Electric power steering device - Google Patents

Abstract

PURPOSE:To provide a torque sensor for detecting the steering torque on a steering shaft in the required state while securing the reliability and durability of an output signal extracting system. CONSTITUTION:A direct acting member 51 movable along the axial direction is provided on one of an input shaft 2 on a steering handle side and an output shaft 3 on a steering wheel side to be excited to the other shaft side by a spring 56. A cam system 52 converting the relative rotary displacement between both shafts into the linear displacement in the axial direction is inserted between the direct acting member and the other shaft. A steering torque detecting means 53 obtaining the drive control output signal of an electric motor 11 by detecting the linear displacement action of the direct acting member via the cam system in the noncontact state is provided.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to the operation force of the steering wheel (
The present invention relates to a power steering device used to reduce steering force (steering force), and more particularly to an improvement of an electric power steering device using an electric motor as its steering assist force generating means.

0002

[Prior Art] Hydraulic type was the mainstream in the past as a power steering device called power steering, but in recent years electric type using electric motor etc. has also been introduced.
Various proposals have been made, including Japanese Patent No. 226362. In other words, a hydraulic power steering system requires a hydraulic cylinder that generates steering assist force, a hydraulic pump, a flow path switching valve, a hydraulic piping system that connects these parts, etc., and has a large number of component parts. The structure is complex and processing accuracy is required, and the manufacturing and assembly operations are not only troublesome, but also the entire device becomes larger and heavier, leading to higher costs. For this reason, recently, an electric type that uses an electric motor as a steering assist force generating means, which can be connected to an on-board battery and a controller using simple electrical wiring, has been attracting attention. The configuration can be simplified, and it can also be made smaller and more compact.

0003

[Problems to be Solved by the Invention] As mentioned above, when an electric motor is used as a steering assist force generating means in a power steering system, it is necessary to appropriately and reliably detect the driver's steering request and control the motor accurately. It is necessary to adopt a configuration that can control the drive well and obtain an appropriate steering assist force. In other words, it is desirable to be able to perform extremely light steering operations when turning the vehicle over while stationary or while driving at low speeds, and to have a steering operation that has a certain degree of weight and rigidity while driving at high speeds. . Therefore, there is a need for a detection mechanism that appropriately and reliably detects the driver's steering requests such as steering force (steering torque), steering angular velocity, etc. together with the vehicle's running speed. No one has yet proposed a device that satisfies all of the requirements, such as being able to be efficiently, easily and reliably incorporated into a large device space, ensuring appropriate operating performance, and facilitating maintenance work. That is, among this type of detection mechanism, for example, as a steering force detection mechanism, a non-contact type torque sensor and its signal processing circuit are interposed between the input and output shafts that make up the steering shaft. In this case, a printed circuit board with a Hall element as a non-contact sensor and various electrical components constituting a signal processing circuit has been proposed. A printed circuit board is attached to one of the input and output shafts, which are movable members, and the output signal due to the relative rotational displacement between these two shafts is transmitted to the fixed side by output signal wiring means consisting of brushes, slip rings, etc. The configuration must be such that it is pulled out and sent to a controller or the like to control the drive of the motor.

However, according to such a conventional structure, it is necessary to provide a detection means such as a non-contact sensor or a magnetic means on the input and output shafts that rotate together, and for this reason, the output signal cannot be taken out using a brush. It is necessary to use a direct sliding contact type with a slip ring and a brush, which not only causes problems in terms of strength and durability, but also causes contact resistance to increase or decrease during use. There were problems such as decreased reliability as a sensor output, and practical problems were unavoidable when detecting and extracting relative rotational displacement between the input and output shafts. . Furthermore, in such a conventional structure, the mounting locations of the sensor components are limited, so the degree of freedom is small, and this is a constraint when trying to downsize the entire device. It is hoped that some kind of countermeasure will be taken to eliminate the problem. On the other hand, what is desired in this type of electric power steering device is that the overall structure is simple, manufacturing and assembly work is easy, and the entire device is small, lightweight, compact, and low cost. The objective is to create a configuration that is possible and has excellent operational performance and compatibility with actual vehicles. Such a demand has become conspicuous because in recent years, this type of device has come to be adopted especially in small cars and the like where space is a major problem.

[0005]

[Means for Solving the Problems] In order to meet such demands, the electric power steering device according to the present invention is capable of rotationally displacing the input shaft on the steering handle side and relatively to the input shaft through a torsion bar. On one side of the output shaft on the steering wheel side connected to the
A linear motion member movable along the axial direction is provided in a state biased toward the other shaft, and a relative rotational displacement between the two shafts is controlled between the linear motion member and the other shaft in the axial direction. A cam mechanism that converts the linear displacement into a linear displacement is provided, and a steering torque detection means is provided that detects the linear displacement operation of the linearly moving member by the cam mechanism in a non-contact state and sends a drive control signal to the electric motor. This is how it was done.

[0006]

[Operation] According to the present invention, when a steering operation is performed and a relative rotational displacement occurs between the input and output shafts, the linear motion member is moved on one shaft by the cam means by the biasing force or by the biasing force. Move in the axial direction against the force. The movement of this linearly moving member is detected by a steering torque detection means attached between the fixed body and the like, and the electric motor can be controlled by the output signal obtained thereby.

[0007]

[Embodiment] FIGS. 1 to 4 show an embodiment of an electric power steering device according to the present invention, and in these figures,
First, the general structure of the electric power steering device, which is generally designated by the reference numeral 1, will be briefly explained using FIG.
Reference numeral 4 indicates a pinion shaft as an output shaft having a pinion 3a connected to a steering wheel (not shown), and 4 indicates a torsion bar that connects these two shafts 2 and 3 so that they can rotate relative to each other within a predetermined angular range. , these members constitute a steering shaft. Further, the shafts 2 and 3 constituting these steering shafts are disposed to penetrate inside the steering gear bodies 6 and 7, together with a rack 5 having rack teeth 5a that mesh with the pinion 3a. In addition, 8a,
8b, 8c, and 8d are bearings that rotatably support the shafts 2 and 3 within the bodies 6 and 7, and as is well known, the above-mentioned rack 5 is a steering wheel that connects the steering wheels together with a tie rod (not shown). Configure the link mechanism. In addition, 9 in the figure indicates the rotational displacement on the tip side of the pinion shaft 3, which is an output side member in the steering system that is provided facing the shaft end side of the pinion shaft 3 and provides steering assist force to the steered wheels in response to the steering operation. This is a steering angular velocity sensor that detects the steering angle and its angular velocity.

In the above-mentioned steering shaft mechanism, the pinion shaft 3 on the steering wheel side, which is connected to the stub shaft 2 on the steering wheel side via the torsion bar 4, has a tooth surface on the side surface on the rack 5 side. A large gear 10 formed by a hypoid gear 10a is pivotally supported, and
An electric motor 11 that provides a steering assist force to the pinion shaft 3 side via the large gear 10 is arranged substantially perpendicular to the pinion shaft 3, and the large gear 10 is disposed on the tip side of the motor shaft 11a.
A gear shaft 12 having a small gear 12a constituting a reduction gear mechanism that also serves as a gear mechanism 13 for transmitting steering assist force is provided, thereby transmitting the steering assist force from the motor 11 to the pinion shaft 3 side. are doing. According to such a configuration, the steering gear bodies 6, 7 having the steering shafts (2, 3, 4), etc., and the reduction gear mechanism (bevel gear etc. may also be used) using hypoid gears, which are gears with staggered shafts, are installed on the pinion shaft 3. The motors 11 and the like that are connected through the device can be efficiently connected, and as a result, the entire device can be made smaller, lighter, and more compact. Of course, according to the hypoid gear as in this embodiment, it is possible to reduce the size in the axial direction by the amount of the misalignment of the shafts. Here, in this embodiment, a small gear 12a from an electric motor 11 and a large gear 10 transmit a steering assist force to a pinion shaft 3 (output shaft system) which is a steering shaft on the steering wheel side. An electromagnetic clutch 20 is provided which selectively connects and interrupts rotation transmission between the motor shaft 11a side and the gear shaft 12 side having a small gear 12a for transmission to the pinion shaft 3 side. This electromagnetic clutch 20 has a well-known structure, in which a clutch rotor 21 is provided on a motor shaft 11a, and a field core 22 is provided on a motor shaft 11a.
The armature 23 is magnetically attracted to the rotor 21 by
is provided on the gear shaft 12 side, and is configured to selectively transmit the rotation of the motor 11 side to the gear shaft 12. In addition, in the figure, 24a, 24b, and 24c are the motor shaft 11a and the gear shaft 12 which is connected with the motor shaft 11a by a spigot.
These are bearings that rotatably support each. Further, the electromagnetic clutch 20 and the motor 11 each have a well-known structure and perform a well-known operation, so a detailed explanation thereof will be omitted.

Furthermore, according to the present embodiment, there is a large gear 10 on the driven side which has a tooth surface 10a on one side and is connected and pivotally supported on the pinion shaft 3 in the rotational direction;
The electric motor 1 meshes with a part of the gear portion 10a of the motor 0 from the side.
In the gear mechanism 13 for transmitting rotational power using off-axis gears such as hypoid gears, the small gear 12a in the large gear 10 is composed of a small gear 12a that transmits the rotational driving force from the large gear 10.
On the other side corresponding to the meshing part with the gear part, there is a biasing means for elastic support that locally presses a part of the large gear 10 in the axial direction so as to constantly mesh with the small gear 12a. 30, and the large gear 10 is elastically held via an elastic cylinder 41 by a flange member 40 which is movable in the axial direction on the pinion shaft 3 and is connected and pivotally supported only in the rotational direction. A plurality of (for example, three) setscrews 42 are connected to each other and provided integrally. Note that the above-mentioned flange member 40 does not necessarily need to be provided slidably in the axial direction, and may be provided fixedly in the rotational direction and the axial direction. In short, it is sufficient that the large gear 10 is swingable and in a movable state that allows the urging means 30 to perform its function. Here, as a biasing means 30 that directly applies a pressing force to the meshing portion between the large gear 10 and the small gear 12a described above,
A ball 33 is supported movably in the axial direction while being held by a receiving member 34 in a plug holder 32 that is screwed into a screw hole drilled in a part of the body 6, and is supported by a spring 35. The meshing portion of the large gear 10 with the small gear 12a is always pressed from the back side, so that the meshing portion of the large gear 10 with the small gear 12a can be biased so that backlash is almost zero. According to such a configuration, the large gear 10
In the gear portion 10a on one side, only the portion meshing with the small gear 12a on the distal end side of the gear shaft 12 on the electric motor 11 side is provided with a biasing means 30 so that an appropriate meshing state is always obtained. By directly pressing and urging, the backlash between the gear portion 10a of the large gear 10 and the gear portion of the small gear 12a becomes substantially zero when the steering wheel is not being steered. It is possible to prevent teeth rattling noise caused by rattling when steering to the left or right, and when steering to the left or right, the large gear 10
However, due to the elastic supporting force of the biasing means 30, the small gear 12a slightly escapes, and the above-mentioned rattling noise etc. does not become a problem at the meshing portion of these two gears 10, 12a, and the required meshing operation is possible. It is also possible to secure a backlash of such an extent that the required rotation transmission can be carried out appropriately without causing the collapse phenomenon as in the conventional case. Here, the meshing of the large gear 10 with the small gear 12a is performed by temporarily reducing the backlash to zero using the biasing means 30 described above, and then loosening it slightly to ensure backlash equal to the amount of adjustment of the ball 33. This makes it possible to perform the required rotation transmission.

Further, according to this embodiment, in order to solve the noise problem caused by the sliding noise and hammering sound when the two gears 10 and 12 mesh due to the slight backlash as described above, the large gear 10 A flange member 40 is provided on the pinion shaft 3 so as to be slidable in the axial direction with a key 43, and holes are provided at equidistant positions in the circumferential direction of the flange member 40. A pair of elastic cylindrical bodies 41 with flanges are formed on both sides of the hole.
, 41 so that the entire body has a substantially enclosing shape, and by inserting a set screw 42 into this part and connecting the tip side to the large gear 10, and fixing it with a nut 45, the large gear 10 can be fixed. , is elastically supported with respect to the pinion shaft 3. It goes without saying that such flanged elastic cylinders 41, 41 are not limited to the two-piece shape, but may be of integral construction. Furthermore, it goes without saying that the flange member 40 may be fixedly provided on the pinion shaft 3 as described above. In this way, in the meshing portion of both gears 10 and 12a, when backlash is secured to the extent that the required meshing operation is possible and the required rotation transmission can be performed, this Holds a set screw 42 for assembling the large gear 10 to the flange member 40, which prevents transmission of sliding noise, hammering noise, etc. caused by meshing between the large gear 10 and the small gear 12a to the steering shaft side (pinion shaft 3). Due to the presence of the elastic cylinders 41, 41, the noise can be appropriately and reliably absorbed and blocked, and there is an advantage that the noise problem can be solved compared to the conventional one. Here, such elastic cylinders 41, 4
1 is obtained by applying a preload between the set screw 42 and the nut 45. Note that the biasing force by the biasing means 30 described above is based on the large gear 10.
The backlash between the gear portion 10a of the large gear 10 and the small gear 12a can be made substantially zero by directly pressing only the meshing portion of the small gear 12a in the axial direction. , or the size of the contact is such that the rattling sound is minute and cannot be heard externally, and has an elastic supporting force that allows the large gear 10 to escape during steering etc. to obtain the required meshing state. It is recommended to set it as follows. Further, the shaft support of the flange member 40 holding the large gear 10 to the pinion shaft 3 only needs to be connected in the rotational direction, and the large gear 1
It suffices to be of a degree that allows zero rocking displacement and some movement in the radial direction.

According to the present invention, a steering torque detection mechanism 50 is provided for detecting the relative rotational displacement between the stub shaft 2 and the pinion shaft 3 due to the torsion of the torsion bar 4 and driving the motor 11. , is characterized in that it has a configuration that is clear from FIGS. 1 to 3. To explain this in detail, the stub shaft 2 on the steering wheel side and one of the pinion shafts 3 on the steering wheel side connected to the stub shaft 2 through a torsion bar 4 so as to be relatively rotatable (stub shaft 2 in the embodiment) A cylindrical body 51 having a flange portion 51a at one end is provided as a linearly moving member movable along the axial direction, and the cylindrical body 51 is always biased to engage with the other shaft side. At the same time, a cam mechanism 52 is interposed between this direct-acting type cylindrical body 51 and the other pinion shaft 3 to convert a relative rotational displacement between the two shafts into a linear displacement in the axial direction. , and detects the linear displacement movement of the cylindrical body 51 due to or against the urging force by the cam mechanism 52 in an electrically non-contact state and sends a drive control signal to the electric motor 11. It is characterized in that a steering torque detection means 53 is provided.

That is, as is clear from FIG. 1 etc., the cylindrical body 51 has a bearing in which the tip of the engagement pin 55, which is provided upright on the stub shaft 2, is inserted into the engagement groove 54 provided on the inner circumference of the cylindrical body 51. The coil spring 56 is held movably in the axial direction on the stub shaft 2 by being slidably engaged through the coil spring 56.
The flange portion 51a is always urged toward the pinion shaft 3 side and faces the flange member 40 assembled on the pinion shaft 3 side, and the cam mechanism 52 is configured to be in an engaged state. A cam surface 52a that cam engages with the tip of an engagement pin 58 provided upright on the outer circumference of the flange member 40 via a bearing 58a is shown in FIG.
3, it is formed along the circumferential direction on the side surface of the flange portion 51a of the cylindrical body 51, and
The shape of 2a allows the relative rotational displacement between these two shafts 2 and 3 to be converted into a linear displacement in the axial direction. In other words, rotational displacement is converted into movement of the cylindrical body 51 in the axial direction. In such a configuration, since the cylindrical body 51 is always positioned in contact with the other side by the spring 56, its displacement can be detected without rattling, etc., and displacement can be detected with high accuracy. It is what it is. In addition, 60 in the figure is a displacement extraction member provided so as to be capable of linear displacement in the axial direction through a sliding hole 61 formed in the axial direction of the body 6, and is connected to the flange portion 51a of the cylindrical body 51. A ball 62 is provided at the contact end of the flange portion 51a to prevent wear due to rotational displacement on the flange portion 51a side by rolling, and a permanent magnet 63 is provided in the rear end side cylinder portion in a state where the polarity is different in the axial direction. is installed buried there. This displacement take-out member 60 is always held at the flange portion 51 by the spring 64.
It is urged to contact a. Here, if the permanent magnet 63 serving as the sensor is formed into a cylindrical shape, there are advantages such as ease of assembling these parts.

On the other hand, the outside of the body 6 faces the permanent magnet 63 of the displacement take-out member 60 in the sliding hole 61 through a hole bored in the body 6, and its movement is controlled by voltage changes. A detection unit holder 71 having a Hall element 70 as a non-contact type sensor for detection is fixed by screwing. In such a configuration, the above-mentioned sensor part can be installed independently from the stub shaft 2 and pinion shaft 3, which increases the degree of freedom in the arrangement position, etc., and is also excellent in terms of ease of assembly. Furthermore, there is an advantage that a signal extraction means such as a slip ring, which poses problems in terms of reliability and durability, is not required, and displacement detection with high precision becomes possible. Here, the above-mentioned permanent magnet 63
The installation position of the Hall element 70, which is provided opposite to the
The holder 71 can be adjusted and positioned outside the body 6 in the direction shown by the dashed arrow, which has the advantage that neutral positioning can be performed extremely easily and reliably. Further, as shown in FIG. 2, as the Hall element 70 facing the above-mentioned permanent magnet 63,
It is preferable to provide two pieces side by side in the circumferential direction of No. 3 so as to enable double checking. Further, the structure in which the holder 71 of the Hall element 70 is attached to the outside of the body 6 has the advantage that electrical wiring etc. can be easily performed and the inside of the body 6 can be configured in a required sealed state. In this embodiment, a case has been described in which torque is detected from linear displacement using a combination of the permanent magnet 63 and the Hall element 70, but similar detection sensor means, such as a potentiometer or optical sensor capable of detecting linear motion, may also be used. It goes without saying that a proximity sensor such as the above may also be used.

According to the above configuration, when a steering operation is performed and a relative rotational displacement occurs between the input and output shafts 2 and 3, the cam mechanism 52 rotates the cylindrical body 51 on one shaft. moves linearly in the axial direction, and this movement is detected by the steering torque detection means 53, which includes a permanent magnet 63 and a Hall element 70, which are attached between the fixed side body 6, etc. The electric motor 11 is activated by the output signal.
can be controlled in a desired state.

5 to 7 show another embodiment of the electric power steering device according to the present invention, and in these figures, the same or corresponding parts as in the above-mentioned embodiment are designated by the same numbers. The explanation will be omitted. Now, in this embodiment, the above-mentioned displacement extraction member is composed of an embedded part of the permanent magnet 63 and a guide part slidably guided by guide rods 80, 80 incorporated in the body 6 in the axial direction. A case is shown in which a structure having an L-shape in side view is used. In this embodiment, although the shape and guide structure of the displacement extraction member 60 are different from the structure of the above-mentioned embodiments, it goes without saying that the same effects as described above can be obtained.

It should be noted that the present invention is not limited to the structure of the embodiment described above, and the shape, structure, etc. of each part of the electric power steering device 1 may be modified or changed as necessary, and various modifications may be made. An example can be considered. For example, in the above-described embodiment, a hypoid gear is used as the gear mechanism 13 for transmitting steering assist force from the motor 11, but the present invention is not limited to this. Gear mechanism 1 consisting of off-axis gears such as gears, planetary gears, bevel gears, etc.
3, and various modifications can be considered. Further, in the above embodiment, the flange member 40 holding the large gear 10 is supported on the pinion shaft 3 as a steering shaft so as to be slidable in the axial direction by key coupling or the like. However, any support structure can be used as long as it can support the large gear 10 in a connected state in the rotational direction, and a conventionally well-known support structure can be used. Further, in the embodiments described above, a rack and pinion type steering gear is illustrated, but the present invention is not limited to this, and it goes without saying that the steering gear may be applied to a ball screw type or the like.

[0017]

As explained above, according to the electric power steering device according to the present invention, one of the input and output shafts, which are connected to each other so as to be relatively rotationally displaceable by the torsion bar, can be rotated along the axial direction. A movable linear motion member is provided biased toward the other shaft, and between this translation member and the other shaft, relative rotational displacement between both shafts is converted into linear displacement in the axial direction. A cam mechanism is interposed therebetween, and a steering torque detecting means is provided which detects the linear displacement movement of the linearly moving member by the cam mechanism in a non-contact state and sends a drive control signal to the electric motor. And despite its inexpensive configuration, the relative rotational displacement between the input and output shafts due to steering operation is converted into linear displacement in the axial direction of the direct-acting member using cam means, and this is reduced to the necessary minimum. By detecting with the steering torque detection means obtained by the number of parts, there are various excellent effects such as being able to appropriately and reliably detect the steering torque. According to the present invention, the detection means can be installed independently from the input and output shaft sides, and the operational reliability and durability of each part including the detection means etc. can be improved. It also has the advantage that it can significantly improve the performance, etc., compared to conventional direct contact type signal extraction means.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of essential parts of an embodiment of an electric power steering device according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG. 1;

FIG. 3 is a sectional view taken along line III-III in FIG. 1;

FIG. 4 is a schematic cross-sectional view showing the overall configuration of the apparatus of the present invention.

FIG. 5 is an enlarged sectional view of a main part showing another embodiment of the device of the present invention.

6 is a sectional view taken along the line VI-VI in FIG. 5. FIG.

7 is a cross-sectional view showing a VIIA-VIIA line cross section on the right side and a VIIB-VIIB line cross section on the left side in FIG. 5; FIG.

[Explanation of symbols]

1 Electric power steering device 2 Stub shaft (input shaft) 3 Pinion shaft (output shaft) 4 Torsion bar 5 Rack 6 Steering gear body 7 Steering gear body 10 Large gear 10a forming hypoid gear
Tooth surface 11 Electric motor 11a Motor shaft 12 Gear shaft 12a of a small gear constituting a hypoid gear Small gear 20 Electromagnetic clutch 30 Urging means 40 Flange member 41 Elastic cylinder 50 Steering torque detection mechanism 51 Cylindrical body (linear member) 51a Flange portion 52 Cam mechanism 52a Cam surface 53 Steering torque detection means 56 Coil spring 58 Engagement pin 60 Displacement extraction member 62 Ball 63 Permanent magnet 64 Spring 70 Hall element 71 Holder

Claims (1)

[Claims] Claim 1: By detecting the steering torque based on the relative rotational displacement between the input shaft on the steering wheel side and the output shaft on the steering wheel side connected thereto via a torsion bar, the steering torque is applied to the steering wheel. In an electric power steering device configured to drive and control an electric motor that provides steering assist force to an output shaft system, a linear motion member movable along an axial direction is provided on one of the input and output shafts. , is provided in a biased state toward the other shaft side, and a cam mechanism is interposed between the linear motion member and the other shaft to convert relative rotational displacement between both shafts into linear displacement in the axial direction. What is claimed is: 1. An electric power steering device comprising: a steering torque detecting means for detecting a linear displacement operation of the linearly moving member by the cam mechanism in a non-contact state;