US20160214641A1 - Vehicle Steering System Transmission - Google Patents
Vehicle Steering System Transmission Download PDFInfo
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- US20160214641A1 US20160214641A1 US15/087,123 US201615087123A US2016214641A1 US 20160214641 A1 US20160214641 A1 US 20160214641A1 US 201615087123 A US201615087123 A US 201615087123A US 2016214641 A1 US2016214641 A1 US 2016214641A1
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- Prior art keywords
- shaft
- sensor
- driver
- steering system
- system transmission
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
- B62D5/0409—Electric motor acting on the steering column
- B62D5/0412—Electric motor acting on the steering column the axes of motor and steering column being parallel
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
- B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
- B62D5/046—Controlling the motor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
- B62D5/0409—Electric motor acting on the steering column
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
- B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
- B62D5/0481—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such monitoring the steering system, e.g. failures
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H7/00—Gearings for conveying rotary motion by endless flexible members
- F16H7/02—Gearings for conveying rotary motion by endless flexible members with belts; with V-belts
- F16H7/023—Gearings for conveying rotary motion by endless flexible members with belts; with V-belts with belts having a toothed contact surface or regularly spaced bosses or hollows for slipless or nearly slipless meshing with complementary profiled contact surface of a pulley
Definitions
- the invention relates to a vehicle steering system transmission, and more particularly, to a vehicle steering system transmission comprising a driver connected to a driver shaft, the driver shaft connected to an output shaft by a flexible link, a first sensor sensing the driver shaft, a control unit receiving a signal from the first sensor, and the control unit transmitting a signal to the driver to control an output shaft movement.
- Electric power assist steering systems have been around since the 1960's. Hydraulic power assist steering has traditionally dominated the market. Hydraulic systems have high parasitic energy loss when the hydraulic pump is pumping, but power assist is not required. Early attempts to eliminate this parasitic loss involved fitting an electric motor to the pump and only driving the pump when necessary.
- Electric hydraulic assisted power steering systems use an electric motor to drive a hydraulic pump to feed a hydraulic power steering system. These systems are an intermediate step by the industry and their use will likely fade with the increased use of EPAS. EPAS systems allow realization of reduced noise, reduced energy use, active safety features, and adjustability to meet driving conditions. However, the use of these systems has remained limited until recent C.A.F.E. requirements became more difficult to meet. This is driving automotive manufactures to turn to EPAS systems more and more in an effort to improve vehicle fuel economy. EPAS systems eliminate the parasitic losses typically found in hydraulic assist power steering systems. System manufacturers such as Nexteer make claims of 6% fuel economy improvements.
- EPAS Even though the main driver for automotive EPAS is fuel economy improvement, EPAS has additional benefits.
- the system can make steering assist available even when the vehicle's engine is not running. It also enables the use of the automatic parallel parking systems available today.
- Rack assist EPAS systems have an electric motor that is connected to the steering rack. The electric motor assists the rack movement usually through driving a lead screw mechanism.
- Column assist EPAS systems have an electric motor connected to the steering column. The electric motor assists the movement of the column shaft usually through a worm gear type arrangement.
- One advantage of these types of systems is the electric motor can be placed in the passenger compartment freeing up valuable space under the hood. This also keeps any sensitive electrical components out of the harsh under hood environment.
- Worm drive column assist systems are usually used in small cars where the assist power requirements are lower than what would be needed in a large heavy vehicle. These systems are limited by the speed of the steering wheel and the ratio of the worm drive. The steering wheel at its fastest speed rotates relatively slowly at approximately 60 rpm. With a 60 rpm speed of the steering wheel and a worm drive ratio of 15:1, the max speed of the electric motor would only be 900 rpm. Worm drives are limited to ratios under 20:1 because ratios higher than that cannot be back-driven.
- the steering system must be able to be operated with no power. This requires the worm drive be able to operate with the gear driving the worm (back-driven). Having a low motor speed and limited ratio worm drive causes the need for high torque motor. Even with a high torque motor, these types of systems have not been made successful on heavy vehicles. Small vehicles are light and require less steering effort thus enabling the use of these systems. Worm drive column assist EPAS systems are the lowest cost systems and thus also lend themselves to smaller less expensive vehicles.
- Typical steering systems with worm drive assists are limited in their efficiency.
- EPAS systems must be designed to operate when there is no power available. Due to the nature of worm drive's tendency to lock up during back driving when ratios exceed approximately 20:1, worm drive EPAS systems efficiency is not greater than approximately 85% and nearer to 65% during back-driving conditions.
- U.S. Pat. No. 8,327,972 discloses a vehicle steering system transmission comprising a housing, an input shaft journalled to the housing, an electric motor connected to the housing and coupled to the input shaft, an output shaft journalled to the housing, the input shaft and the output shaft coupled by a first pair of sprockets having a first belt trained therebetween and having a first ratio, the first belt and first pair of sprockets comprising a helical tooth configuration, the input shaft and the output shaft coupled by a second pair of sprockets having a second belt trained therebetween and having a second ratio, and the input shaft and the output shaft coupled by a third pair of sprockets having a third belt trained therebetween and having a third ratio.
- a vehicle steering system transmission comprising a driver connected to a driver shaft, the driver shaft connected to an output shaft by a flexible link, a first sensor sensing the driver shaft, a control unit receiving a signal from the first sensor, and the control unit transmitting a signal to the driver to control an output shaft movement.
- the primary aspect of the invention is a vehicle steering system transmission comprising a driver connected to a driver shaft, the driver shaft connected to an output shaft by a flexible link, a first sensor sensing the driver shaft, a control unit receiving a signal from the first sensor, and the control unit transmitting a signal to the driver to control an output shaft movement.
- the invention comprises a vehicle steering system transmission comprising a driver connected to a driver shaft, the driver shaft connected to an output shaft by a flexible link, a first sensor sensing the driver shaft, a control unit receiving a signal from the first sensor, and the control unit transmitting a signal to the driver to control an output shaft movement.
- FIG. 1 is a perspective view of the system transmission.
- FIG. 2 is a perspective view of an intermediate sprocket.
- FIG. 3 is a perspective view of an intermediate sprocket.
- FIG. 4 is a perspective view of a steering system.
- FIG. 5 is a schematic diagram of the control system.
- FIG. 6 is a perspective view of an alternate embodiment.
- FIG. 1 is a perspective view of the system transmission.
- the inventive device comprises sensor 1 , sensor 2 , sensor 3 .
- Sensor 1 is mounted to input shaft 4 .
- Sensor 2 is mounted to intermediate shaft 12 .
- Sensor 3 is mounted to intermediate shaft 23 .
- Flexible link 6 is trained between input shaft 4 and intermediate shaft 12 .
- Flexible link 7 is trained between intermediate shaft 12 and intermediate shaft 23 .
- Belt 8 is trained between intermediate shaft 23 and output shaft 10 .
- Each belt comprises a mechanical linkage between the respective sprockets.
- Input sprocket 4 is driven by an electric motor or any other device providing rotation and torque.
- Sensor 1 measures the angular position of input shaft 4 .
- Sensor 2 measures the angular position of intermediate shaft 12 .
- Sensor 3 measures the angular position of intermediate shaft 23 .
- Input shaft 4 has 20 teeth.
- Flexible link 6 and flexible link 7 may each comprise a toothed belt or a chain.
- Intermediate shaft 12 comprises a first sprocket 120 and a second sprocket 121 .
- Sprocket 120 has 43 teeth
- sprocket 121 has 18 teeth (see FIG. 2 ).
- Input shaft 4 and sprocket 120 are connected through flexible link 6 .
- Intermediate shaft 23 has first sprocket 230 and second sprocket 231 .
- Sprocket 230 has 41 teeth.
- Sprocket 231 has 18 teeth.
- Sprocket 121 and Sprocket 230 are connected through flexible link 7 .
- Output shaft 5 has 73 teeth. Sprocket 231 and output shaft 5 are connected through flexible link 8 .
- the initial starting position of the three shafts 4 , 12 , 23 with sensors 1 , 2 , 3 must be known as well as the position of the output shaft 5 . From this starting position, the position of each shaft can be measured as a result of rotation of input shaft 4 . The angular position of each sprocket can be calculated since we know the drive ratio at each stage and the overall drive ratio.
- the angular position of each shaft can be determined with the following equation:
- intermediate shaft 12 rotates
- the fractional portion of the number of turns is then converted to an angular position.
- This result represents the number of degrees of rotation from the original starting position of intermediate shaft 12 . Since the drive ratio at each sprocket in the drive is known, one can determine the position of each shaft from its starting position.
- the inventive device is configured such that each position of output shaft 5 corresponds to only one unique position of the three other shafts. If power is lost in the system, when power returns, the position of output shaft 5 can be determined by the position of the three shafts with sensors. If a drive is not limited in the number of revolutions of the output shaft, the positions of the individual shafts will eventually return to their respective starting positions and the shaft relative positions will repeat.
- the output shaft is the vehicle steering shaft it is advantageous to know the position of the steering shaft.
- the arrangement of the drive ratios must be such that the number of turns required to cause repeating of the positions exceeds the total number of turns in the drive.
- sensor 1 indicates input shaft 4 is at a position 5 degrees clockwise from its original position
- sensor 2 can only indicate a position for intermediate shaft 12 that is equal to a whole number of turns of input shaft 4 plus the 5 degrees of rotation from its starting position multiplied by the fixed ratio of drive stage 1 .
- intermediate shaft 23 rotates 75.013 degrees.
- the accuracy of the final position of output shaft 5 is determined by the accuracy of the sensor 1 on input shaft 4 .
- the location of output shaft 5 is known with an accuracy that is equal to the accuracy of sensor 1 divided by the drive ratio. For example, if sensor 1 has a position tolerance of 5 degrees on the above drive with an overall ratio of 19.73, the position of output shaft 5 can be determined within 5/19.73 degrees or 0.25 degrees.
- This sensor arrangement gives one the ability to gain significant position accuracy relative to the accuracy of individual position sensors. This arrangement provides improved accuracy when compared to placing a sensor on the output shaft without changing the accuracy of the sensor itself.
- the ratios of each stage should be arranged such that they are not whole numbers.
- Changing drive stage 1 such that its ratio is the nearest whole number, for example 40/20 2, causes the shaft positions to repeat every 68 revolutions of input shaft 4 given the same sensor accuracy.
- the ratios of the drive should be arranged such that the repeating pattern of the positions of the shafts is large enough to exceed the number of revolutions required for the output shaft.
- each sensor has a 5 degrees accuracy tolerance. If one increased the accuracy of sensor 1 to 2.5 degrees one could double the tolerance on the other two sensors ( 2 , 3 ) and maintain the same number of revolutions (258) until the shaft positions repeated. This would also improve the accuracy of detecting the position of output shaft 5 from 0.25 degrees to 0.125 degrees of error.
- sensor 1 determines the overall positional accuracy of the drive, hence, sensor 2 and sensor 3 can have twice the tolerance of sensor 1 and the device can still maintain the same number of revolutions to repeat the shaft positions.
- the ratios of the drive stages must be such that one revolution of input shaft 4 causes at least one of the other shafts to move to a position that is outside its possible previous position inclusive of the tolerance of the sensor.
- FIG. 4 is a perspective view of a steering system.
- Output shaft 5 is the steering shaft for a steering system 80 .
- Steering wheel 51 is connected to steering shaft 5 .
- Shaft 5 is connected to a steering rack 60 .
- Steering rack is connected to the vehicle wheels for steering, not shown.
- motor 40 comprises a Johnson Electric EPS-B77.
- the motor listed herein is only an example and is not intended to limit the scope or use of other suitable motors.
- FIG. 5 is a schematic diagram of the control system.
- Sensor 1 transmits an angular position signal for shaft 4 to the steering control unit 500 .
- Sensor 2 detects an angular position of shaft 12 and transmits a signal to steering control unit 500 .
- Sensor 3 detects an angular position of shaft 23 and transmits a signal to steering control unit 500 .
- a torque sensor 400 detects a torque load applied to shaft 10 by a user.
- Torque sensor transmits a signal to steering control unit 500 .
- Steering control unit 500 processes the signals from the position sensors ( 1 , 2 , 3 ) and torque sensor to determine a control requirement for the motor 40 .
- Unit 500 then transmits a control signal to the motor 40 , which in turn applies a boost torque to shaft 10 .
- Motor 40 is connected to vehicle power 600 .
- Sensors 1 , sensor 2 , sensor 3 comprise Gill Blade 360 Rotary Sensors.
- Torque sensor 400 comprises a TT Electronics model SX-4428. The sensors listed herein are only examples and are not intended to limit the scope or use of other suitable sensors.
- FIG. 6 is a perspective view of an alternate embodiment.
- the inventive device comprises sensor 1 , sensor 2 , sensor 3 .
- Sensor 1 is mounted to input shaft 4 .
- Sensor 2 is mounted to intermediate shaft 12 .
- Sensor 3 is mounted to intermediate shaft 23 .
- Input shaft 4 is driven by an electric motor 40 or any other device providing rotation and torque.
- Sensor 1 measures the angular position of input shaft 4 .
- Sensor 2 measures the angular position of intermediate shaft 12 .
- Sensor 3 measures the angular position of intermediate shaft 23 .
- Input shaft 4 comprises a gear 40 with 20 teeth.
- Intermediate shaft 12 consists of first gear 120 and second gear 121 .
- Gear 120 has 43 teeth.
- Gear 121 has 18 teeth.
- Each gear pair between shafts comprises a mechanical linkage.
- Input shaft 4 drives gear 120 .
- Intermediate shaft 23 has first gear 230 and second gear 231 .
- Gear 230 has 41 teeth.
- Gear 231 has 18 teeth.
- Gear 121 drives gear 230 .
- Output gear 50 has 73 teeth.
- Gear 231 drives output shaft 5 .
- the ratios of each stage of the drive should be arranged such that they are not whole numbers.
- Changing drive stage 1 such that its ratio is the nearest whole number, for example 40/20 2, causes the shaft positions to repeat every 32 revolutions of input shaft 4 given the same sensor accuracy.
- the ratios of the drive should be arranged such that the repeating pattern of the positions of the shafts is large enough to exceed the number of revolutions required for the output shaft.
- the sensors each have the same 5 degrees accuracy tolerance. If the accuracy of sensor 1 is increased to 2.0 degrees, one could increase the tolerance on the other two sensors to 5.0 degrees and maintain the same number of revolutions (387) until the shaft positions repeated. This would also improve the accuracy of the position of output shaft 5 from 0.25 degrees to 0.125 degrees of error.
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Abstract
A vehicle steering system transmission comprising a driver connected to a driver shaft, the driver shaft connected to an output shaft by a flexible link, a first sensor sensing the driver shaft, a control unit receiving a signal from the first sensor, and the control unit transmitting a signal to the driver to control an output shaft movement.
Description
- This application is a division of U.S. nonprovisional patent application Ser. No. 14/456,521 filed Aug. 11, 2014.
- The invention relates to a vehicle steering system transmission, and more particularly, to a vehicle steering system transmission comprising a driver connected to a driver shaft, the driver shaft connected to an output shaft by a flexible link, a first sensor sensing the driver shaft, a control unit receiving a signal from the first sensor, and the control unit transmitting a signal to the driver to control an output shaft movement.
- Electric power assist steering systems (EPAS) have been around since the 1960's. Hydraulic power assist steering has traditionally dominated the market. Hydraulic systems have high parasitic energy loss when the hydraulic pump is pumping, but power assist is not required. Early attempts to eliminate this parasitic loss involved fitting an electric motor to the pump and only driving the pump when necessary.
- Electric hydraulic assisted power steering systems use an electric motor to drive a hydraulic pump to feed a hydraulic power steering system. These systems are an intermediate step by the industry and their use will likely fade with the increased use of EPAS. EPAS systems allow realization of reduced noise, reduced energy use, active safety features, and adjustability to meet driving conditions. However, the use of these systems has remained limited until recent C.A.F.E. requirements became more difficult to meet. This is driving automotive manufactures to turn to EPAS systems more and more in an effort to improve vehicle fuel economy. EPAS systems eliminate the parasitic losses typically found in hydraulic assist power steering systems. System manufacturers such as Nexteer make claims of 6% fuel economy improvements.
- For example, one difficulty that slowed implementation of EPAS systems was meeting the power requirement with a 12 volt electric motor. Recently systems have been developed that successfully solve this problem. Further, all EPAS systems require a control module to sense driver input and control the electric motor to provide the desired assist. The control module measures driver input torque and uses this to determine the amount of assist required. Assist can be tuned to meet the drivers need depending on driving conditions. The system can even have a tunable “feel” available to the driver.
- Even though the main driver for automotive EPAS is fuel economy improvement, EPAS has additional benefits. The system can make steering assist available even when the vehicle's engine is not running. It also enables the use of the automatic parallel parking systems available today.
- There are two main types of EPAS systems; column assist and rack assist. Rack assist EPAS systems have an electric motor that is connected to the steering rack. The electric motor assists the rack movement usually through driving a lead screw mechanism. Column assist EPAS systems have an electric motor connected to the steering column. The electric motor assists the movement of the column shaft usually through a worm gear type arrangement. One advantage of these types of systems is the electric motor can be placed in the passenger compartment freeing up valuable space under the hood. This also keeps any sensitive electrical components out of the harsh under hood environment.
- Worm drive column assist systems are usually used in small cars where the assist power requirements are lower than what would be needed in a large heavy vehicle. These systems are limited by the speed of the steering wheel and the ratio of the worm drive. The steering wheel at its fastest speed rotates relatively slowly at approximately 60 rpm. With a 60 rpm speed of the steering wheel and a worm drive ratio of 15:1, the max speed of the electric motor would only be 900 rpm. Worm drives are limited to ratios under 20:1 because ratios higher than that cannot be back-driven.
- The steering system must be able to be operated with no power. This requires the worm drive be able to operate with the gear driving the worm (back-driven). Having a low motor speed and limited ratio worm drive causes the need for high torque motor. Even with a high torque motor, these types of systems have not been made successful on heavy vehicles. Small vehicles are light and require less steering effort thus enabling the use of these systems. Worm drive column assist EPAS systems are the lowest cost systems and thus also lend themselves to smaller less expensive vehicles.
- Typical steering systems with worm drive assists are limited in their efficiency. EPAS systems must be designed to operate when there is no power available. Due to the nature of worm drive's tendency to lock up during back driving when ratios exceed approximately 20:1, worm drive EPAS systems efficiency is not greater than approximately 85% and nearer to 65% during back-driving conditions.
- Representative of the art is U.S. Pat. No. 8,327,972 which discloses a vehicle steering system transmission comprising a housing, an input shaft journalled to the housing, an electric motor connected to the housing and coupled to the input shaft, an output shaft journalled to the housing, the input shaft and the output shaft coupled by a first pair of sprockets having a first belt trained therebetween and having a first ratio, the first belt and first pair of sprockets comprising a helical tooth configuration, the input shaft and the output shaft coupled by a second pair of sprockets having a second belt trained therebetween and having a second ratio, and the input shaft and the output shaft coupled by a third pair of sprockets having a third belt trained therebetween and having a third ratio.
- What is needed is a vehicle steering system transmission comprising a driver connected to a driver shaft, the driver shaft connected to an output shaft by a flexible link, a first sensor sensing the driver shaft, a control unit receiving a signal from the first sensor, and the control unit transmitting a signal to the driver to control an output shaft movement. The present invention meets this need.
- The primary aspect of the invention is a vehicle steering system transmission comprising a driver connected to a driver shaft, the driver shaft connected to an output shaft by a flexible link, a first sensor sensing the driver shaft, a control unit receiving a signal from the first sensor, and the control unit transmitting a signal to the driver to control an output shaft movement.
- Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.
- The invention comprises a vehicle steering system transmission comprising a driver connected to a driver shaft, the driver shaft connected to an output shaft by a flexible link, a first sensor sensing the driver shaft, a control unit receiving a signal from the first sensor, and the control unit transmitting a signal to the driver to control an output shaft movement.
- The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention.
-
FIG. 1 is a perspective view of the system transmission. -
FIG. 2 is a perspective view of an intermediate sprocket. -
FIG. 3 is a perspective view of an intermediate sprocket. -
FIG. 4 is a perspective view of a steering system. -
FIG. 5 is a schematic diagram of the control system. -
FIG. 6 is a perspective view of an alternate embodiment. -
FIG. 1 is a perspective view of the system transmission. The inventive device comprisessensor 1,sensor 2,sensor 3.Sensor 1 is mounted to inputshaft 4.Sensor 2 is mounted tointermediate shaft 12.Sensor 3 is mounted tointermediate shaft 23. Flexible link 6 is trained betweeninput shaft 4 andintermediate shaft 12.Flexible link 7 is trained betweenintermediate shaft 12 andintermediate shaft 23.Belt 8 is trained betweenintermediate shaft 23 and output shaft 10. Each belt comprises a mechanical linkage between the respective sprockets. -
Input sprocket 4 is driven by an electric motor or any other device providing rotation and torque.Sensor 1 measures the angular position ofinput shaft 4.Sensor 2 measures the angular position ofintermediate shaft 12.Sensor 3 measures the angular position ofintermediate shaft 23.Input shaft 4 has 20 teeth. Flexible link 6 andflexible link 7 may each comprise a toothed belt or a chain. -
Intermediate shaft 12 comprises afirst sprocket 120 and asecond sprocket 121.Sprocket 120 has 43 teeth,sprocket 121 has 18 teeth (seeFIG. 2 ).Input shaft 4 andsprocket 120 are connected through flexible link 6.Intermediate shaft 23 hasfirst sprocket 230 andsecond sprocket 231.Sprocket 230 has 41 teeth.Sprocket 231 has 18 teeth.Sprocket 121 andSprocket 230 are connected throughflexible link 7.Output shaft 5 has 73 teeth.Sprocket 231 andoutput shaft 5 are connected throughflexible link 8. - To operate properly, the initial starting position of the three
shafts sensors output shaft 5. From this starting position, the position of each shaft can be measured as a result of rotation ofinput shaft 4. The angular position of each sprocket can be calculated since we know the drive ratio at each stage and the overall drive ratio. - For example, given:
-
- Θ1=angle of
input shaft 4 from its starting position (in turns where one turn=360 degrees) - Nn=ratio of drive to each sprocket from the input sprocket
- Θn=angle of the shaft from its starting position (in turns)
- Θ1=angle of
- The angular position of each shaft can be determined with the following equation:
-
Θn =N n eθ 1 - For a rotation of the
input shaft 4 of 20 revolutions,intermediate shaft 12 rotates -
Θ12=(20/43)(20) -
Θ12=9.3023 turns - The fractional portion of the number of turns is then converted to an angular position.
-
0.3023 turns=0.3023*360 degree/turn=108.28 degrees - This result represents the number of degrees of rotation from the original starting position of
intermediate shaft 12. Since the drive ratio at each sprocket in the drive is known, one can determine the position of each shaft from its starting position. - The inventive device is configured such that each position of
output shaft 5 corresponds to only one unique position of the three other shafts. If power is lost in the system, when power returns, the position ofoutput shaft 5 can be determined by the position of the three shafts with sensors. If a drive is not limited in the number of revolutions of the output shaft, the positions of the individual shafts will eventually return to their respective starting positions and the shaft relative positions will repeat. - In devices such as electric assist steering systems, where the output shaft is the vehicle steering shaft it is advantageous to know the position of the steering shaft. To avoid losing the known position of the output shaft, the arrangement of the drive ratios must be such that the number of turns required to cause repeating of the positions exceeds the total number of turns in the drive.
- In the system described above, one can compare the original starting position of each shaft with its current position. When all three current positions align with their original position within the tolerance zone of the sensor, the unique position is then repeating itself. The tolerance of the position sensors expands the possible positions of each shaft during sensing of shaft position.
- For example, if
sensor 1 indicatesinput shaft 4 is at aposition 5 degrees clockwise from its original position,sensor 2 can only indicate a position forintermediate shaft 12 that is equal to a whole number of turns ofinput shaft 4 plus the 5 degrees of rotation from its starting position multiplied by the fixed ratio ofdrive stage 1. For this consideration, assume all starting positions correspond to the vertical position. For example, ifinput shaft 4rotates 5 degrees,intermediate shaft 12 must only have rotated 5 degrees×(20/43)=2.325 degrees. Ifinput shaft 4 rotated one turn plus 5 degrees,intermediate shaft 12 must have rotated (360+5)×(20/43)=169.767 degrees. This same logic holds true for the position ofintermediate shaft 23. Continuing with the same example,intermediate shaft 23 must have rotated 5 degree×(20/42)×(19/43)=1.027 degrees for a 5 degree rotation ofinput shaft 4. For one turn plus 5 degrees rotation ofinput shaft 4,intermediate shaft 23 rotates 75.013 degrees. - For each position of
input shaft 4, there is only one corresponding position of bothintermediate shaft 12 andintermediate shaft 23. These positions are used mainly to indicate the number of turns ofinput shaft 4. For example, ifsensor 3 onintermediate shaft 23 indicates an angle of 16.4 degrees, andsensor 1 indicates an angle of 5 degrees andsensor 2 indicates and angle of 169.7 degrees, the number of turns thatinput shaft 4 turned corresponds to 44 turns. So the position ofoutput shaft 5 is determined as (44 turns×(360 deg/turn)+5 degrees)×(20/43)(19/34)(18/73)=802.9 degrees. This corresponds to two turns plus 82.95 degrees or 2.23 turns from its start position. - The accuracy of the final position of
output shaft 5 is determined by the accuracy of thesensor 1 oninput shaft 4. The location ofoutput shaft 5 is known with an accuracy that is equal to the accuracy ofsensor 1 divided by the drive ratio. For example, ifsensor 1 has a position tolerance of 5 degrees on the above drive with an overall ratio of 19.73, the position ofoutput shaft 5 can be determined within 5/19.73 degrees or 0.25 degrees. This sensor arrangement gives one the ability to gain significant position accuracy relative to the accuracy of individual position sensors. This arrangement provides improved accuracy when compared to placing a sensor on the output shaft without changing the accuracy of the sensor itself. - For a given sensor tolerance, one must include this tolerance in determining the number of revolutions of
input shaft 4 required to cause the shaft positions to repeat. Analysis of the inventive device shows that with a position tolerance of 5 degrees on each sensor, the shaft positions repeat every 258 revolutions ofinput shaft 4. This equates to 13.07 revolutions ofoutput shaft 5. To track accurately the position ofoutput shaft 5, its travel must be limited to less than 13.07 total revolutions in order to avoid repeating the shaft positions. - To maximize the total rotations between repeats of the shaft positions, the ratios of each stage should be arranged such that they are not whole numbers. For example, in the inventive device, the ratio of
drive stage 1 is 43/20=2.15, the ratio ofdrive stage 2 is 43/19=2.26, and the ratio ofdrive stage 3 is 73/18=4.05. Changingdrive stage 1 such that its ratio is the nearest whole number, for example 40/20=2, causes the shaft positions to repeat every 68 revolutions ofinput shaft 4 given the same sensor accuracy. The ratios of the drive should be arranged such that the repeating pattern of the positions of the shafts is large enough to exceed the number of revolutions required for the output shaft. - In the examples, each sensor has a 5 degrees accuracy tolerance. If one increased the accuracy of
sensor 1 to 2.5 degrees one could double the tolerance on the other two sensors (2,3) and maintain the same number of revolutions (258) until the shaft positions repeated. This would also improve the accuracy of detecting the position ofoutput shaft 5 from 0.25 degrees to 0.125 degrees of error. - Doubling the accuracy of
sensor 1 to 2.5 degrees and maintaining the 5 degree tolerance onsensors - The accuracy of
sensor 1 determines the overall positional accuracy of the drive, hence,sensor 2 andsensor 3 can have twice the tolerance ofsensor 1 and the device can still maintain the same number of revolutions to repeat the shaft positions. - For the arrangement of the
sensor 1,sensor 2,sensor 3 to be effective in determining the position of theoutput shaft 5, the ratios of the drive stages must be such that one revolution ofinput shaft 4 causes at least one of the other shafts to move to a position that is outside its possible previous position inclusive of the tolerance of the sensor. - For example, given:
-
- T=1 turn of input shaft
- N=Ratio to interested shaft
- E=sensor error (in turns)
- Then:
-
- TN>E
- 1(20/43)>5/360
- 0.4651>0.01389
-
FIG. 4 is a perspective view of a steering system.Output shaft 5 is the steering shaft for asteering system 80.Steering wheel 51 is connected to steeringshaft 5.Shaft 5 is connected to asteering rack 60. Steering rack is connected to the vehicle wheels for steering, not shown. In this embodiment,motor 40 comprises a Johnson Electric EPS-B77. The motor listed herein is only an example and is not intended to limit the scope or use of other suitable motors. -
FIG. 5 is a schematic diagram of the control system.Sensor 1 transmits an angular position signal forshaft 4 to thesteering control unit 500.Sensor 2 detects an angular position ofshaft 12 and transmits a signal tosteering control unit 500.Sensor 3 detects an angular position ofshaft 23 and transmits a signal tosteering control unit 500. In addition, atorque sensor 400 detects a torque load applied to shaft 10 by a user. Torque sensor transmits a signal tosteering control unit 500.Steering control unit 500 processes the signals from the position sensors (1,2,3) and torque sensor to determine a control requirement for themotor 40.Unit 500 then transmits a control signal to themotor 40, which in turn applies a boost torque to shaft 10.Motor 40 is connected tovehicle power 600.Sensors 1,sensor 2,sensor 3 comprise Gill Blade 360 Rotary Sensors.Torque sensor 400 comprises a TT Electronics model SX-4428. The sensors listed herein are only examples and are not intended to limit the scope or use of other suitable sensors. -
FIG. 6 is a perspective view of an alternate embodiment. In an alternate embodiment, the inventive device comprisessensor 1,sensor 2,sensor 3.Sensor 1 is mounted to inputshaft 4.Sensor 2 is mounted tointermediate shaft 12.Sensor 3 is mounted tointermediate shaft 23.Input shaft 4 is driven by anelectric motor 40 or any other device providing rotation and torque.Sensor 1 measures the angular position ofinput shaft 4.Sensor 2 measures the angular position ofintermediate shaft 12.Sensor 3 measures the angular position ofintermediate shaft 23.Input shaft 4 comprises agear 40 with 20 teeth. -
Intermediate shaft 12 consists offirst gear 120 andsecond gear 121.Gear 120 has 43 teeth.Gear 121 has 18 teeth. Each gear pair between shafts comprises a mechanical linkage.Input shaft 4 drivesgear 120.Intermediate shaft 23 hasfirst gear 230 andsecond gear 231.Gear 230 has 41 teeth.Gear 231 has 18 teeth.Gear 121 drivesgear 230.Output gear 50 has 73 teeth.Gear 231 drivesoutput shaft 5. - Except as described as follows, the calculations for the gear drive system are the same as for the belt drive system.
- Since the sensors have a tolerance, one must include this tolerance in determining the number of revolutions of
input shaft 4 required to cause the shaft positions to repeat. Analysis of the inventive device shows that with a position tolerance of 5 degrees on each sensor, the shaft positions repeat every 387 revolutions ofinput shaft 4. This equates to 19.49 revolutions ofoutput shaft 5. To fully track the position ofoutput shaft 5, its travel must be limited to less that this 19.49 total revolutions to avoid repeating the shaft positions. - To maximize the total travel between repeats of the shaft positions, the ratios of each stage of the drive should be arranged such that they are not whole numbers. For example, in the inventive device, the ratio of
drive stage 1 is 43/20=2.15, the ratio ofdrive stage 2 is 43/19=2.26, and the ratio ofdrive stage 3 is 73/18=4.05. Changingdrive stage 1 such that its ratio is the nearest whole number, for example 40/20=2, causes the shaft positions to repeat every 32 revolutions ofinput shaft 4 given the same sensor accuracy. The ratios of the drive should be arranged such that the repeating pattern of the positions of the shafts is large enough to exceed the number of revolutions required for the output shaft. - In the examples given here, the sensors each have the same 5 degrees accuracy tolerance. If the accuracy of
sensor 1 is increased to 2.0 degrees, one could increase the tolerance on the other two sensors to 5.0 degrees and maintain the same number of revolutions (387) until the shaft positions repeated. This would also improve the accuracy of the position ofoutput shaft 5 from 0.25 degrees to 0.125 degrees of error. - Doubling the accuracy tolerance of
sensor 1 to 2.5 degrees and maintaining the 5 degree tolerance onsensors sensor 1 determines the overall positional accuracy of the drive.Sensors - Although forms of the invention have been described herein, it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts without departing from the spirit and scope of the invention described herein.
Claims (11)
1. A vehicle steering system transmission comprising:
a driver connected to a driver shaft;
the driver shaft connected to an output shaft by a first gear link;
a first sensor sensing the driver shaft;
a control unit receiving a signal from the first sensor; and
the control unit transmitting a signal to the driver to control an output shaft movement.
2. The vehicle steering system transmission as in claim 1 , wherein the first sensor senses an angular position and transmits a signal to the control unit.
3. The vehicle steering system transmission as in claim 1 , wherein the control unit is in communication with a vehicle control system.
4. The vehicle steering system transmission as in claim 1 further comprising a second shaft, the second shaft connected to the driver shaft by the first gear link and connected to the output shaft by a second gear link.
5. The vehicle steering system transmission as in claim 4 further comprising a second sensor sensing the second shaft.
6. The vehicle steering system transmission as in claim 5 , wherein the second sensor senses an angular position and transits a signal to the control unit.
7. The vehicle steering system transmission as in claim 6 , wherein the output shaft comprises a steering shaft.
8. The vehicle steering system transmission as in claim 7 further comprising a third sensor sensing the steering shaft.
9. The vehicle steering system transmission as in claim 8 , wherein the third sensor senses a torque.
10. The vehicle steering system transmission as in claim 9 , wherein the third sensor transmits a signal to the control unit.
11. The vehicle steering system transmission as in claim 1 , wherein the first linkage comprises gears.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US15/087,123 US20160214641A1 (en) | 2014-08-11 | 2016-03-31 | Vehicle Steering System Transmission |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US14/456,521 US9302701B2 (en) | 2014-08-11 | 2014-08-11 | Vehicle steering system transmission |
US15/087,123 US20160214641A1 (en) | 2014-08-11 | 2016-03-31 | Vehicle Steering System Transmission |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US14/456,521 Division US9302701B2 (en) | 2014-08-11 | 2014-08-11 | Vehicle steering system transmission |
Publications (1)
Publication Number | Publication Date |
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US20160214641A1 true US20160214641A1 (en) | 2016-07-28 |
Family
ID=53836252
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
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US14/456,521 Active US9302701B2 (en) | 2014-08-11 | 2014-08-11 | Vehicle steering system transmission |
US15/087,123 Abandoned US20160214641A1 (en) | 2014-08-11 | 2016-03-31 | Vehicle Steering System Transmission |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
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US14/456,521 Active US9302701B2 (en) | 2014-08-11 | 2014-08-11 | Vehicle steering system transmission |
Country Status (11)
Country | Link |
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US (2) | US9302701B2 (en) |
EP (1) | EP3180229B1 (en) |
JP (1) | JP6454406B2 (en) |
KR (1) | KR101950123B1 (en) |
CN (1) | CN106687359B (en) |
AU (1) | AU2015302063B2 (en) |
CA (1) | CA2957208C (en) |
MX (1) | MX2017001724A (en) |
MY (1) | MY182052A (en) |
RU (1) | RU2017107516A (en) |
WO (1) | WO2016025250A1 (en) |
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GB2568925B (en) * | 2017-11-30 | 2022-09-28 | Trw Ltd | Power-assisted steering assembly |
US10793183B2 (en) * | 2017-12-22 | 2020-10-06 | Trw Automotive U.S. Llc | Torque overlay steering apparatus |
US10811934B2 (en) * | 2018-02-06 | 2020-10-20 | Mando Corporation | Electromechanical actuator package with belt drive mechanism for steer-by-wire hand wheel actuator |
DE102019202017A1 (en) * | 2019-02-14 | 2020-08-20 | Robert Bosch Gmbh | Method for monitoring a steering device |
CN113335368B (en) * | 2021-07-22 | 2022-06-10 | 中国第一汽车股份有限公司 | Intelligent automobile man-machine cooperation steering input device |
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Also Published As
Publication number | Publication date |
---|---|
EP3180229A1 (en) | 2017-06-21 |
MY182052A (en) | 2021-01-18 |
US20160039451A1 (en) | 2016-02-11 |
CA2957208A1 (en) | 2016-02-18 |
JP6454406B2 (en) | 2019-01-16 |
CA2957208C (en) | 2019-06-04 |
EP3180229B1 (en) | 2021-06-02 |
KR101950123B1 (en) | 2019-02-19 |
RU2017107516A3 (en) | 2018-09-13 |
CN106687359A (en) | 2017-05-17 |
JP2017524595A (en) | 2017-08-31 |
MX2017001724A (en) | 2017-05-30 |
KR20170038928A (en) | 2017-04-07 |
BR112017002616A2 (en) | 2017-12-05 |
CN106687359B (en) | 2019-04-19 |
AU2015302063B2 (en) | 2018-06-28 |
RU2017107516A (en) | 2018-09-13 |
US9302701B2 (en) | 2016-04-05 |
WO2016025250A1 (en) | 2016-02-18 |
AU2015302063A1 (en) | 2017-02-23 |
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