JPH029986B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric power steering system for a vehicle that uses an electric motor as a power source in order to reduce the steering force of the vehicle's steering wheel.

Compared to hydraulic power steering devices, electric power steering devices do not require an oil pump as a power source that is constantly connected directly to the engine, so there is no loss of engine horsepower. Since no hydraulic fluid is used, there is no need to worry about hydraulic fluid leakage or dirt, and maintenance is easy. Easy to assemble as there is no need for hydraulic piping and only electrical wiring is required. Since a highly precise and delicate device such as a hydraulic control valve is not required, an inexpensive system can be expected.

The number of parts and weight are reduced, and the engine area is streamlined, making maintenance easier. Although it has many advantages such as being able to share the main parts with the manual steering device, and many proposals have been made, the reason why it has not been put into practical use is because it is not commonly used as a single drive source. An electric motor with sufficient output would be quite large in size as a steering system component, and modern front-wheel drive passenger cars lack space and are difficult to install. 2.Since the power supply for passenger cars is 12V DC, it is common to use small 12V DC motors, but the torque generated by these motors is small, only a few kg/cm, and the bearings The influence of resistance, slider resistance, etc. is also significant, and the efficiency of the electric motor alone is 50 to 65%. If you carelessly increase the bearing diameter or slider diameter, or use a worm gear with high loss in the first stage reducer, the efficiency including the steering gear will drop to 30% or less, and this will lead to smaller electric motors, Obstructs weight reduction,
It requires a large current, making it difficult to install in passenger cars. 3 In an electric power steering system, an electric motor and a reduction gear with a large reduction ratio are connected to the input shaft side of the steering gear, so friction on the input shaft side inevitably increases compared to when the steering gear is used alone. do. This obstructs the return of the steering wheel in a passenger car, increases the torque difference between the steering force and the steering force, and also gives an ambiguous steering feel without a direct feeling in the minute steering area during high-speed driving, and the final hydraulic pressure It is inferior in comparison to the formula, and is hindering its practical application. The electrical control circuit of the 4-electric power steering system has no track record of reliability, and there are problems with consideration of safety as an important safety component. etc.

SUMMARY OF THE INVENTION In order to solve these problems, it is an object of the present invention to provide an electric power steering system having a particularly safe and reliable electric control circuit.

Below, drawings showing embodiments of the present invention will be described.

A steering gear assembly 1 mounted on a vehicle body is connected to an output shaft 11 via an intermediate shaft 7 having cross joints 5 at both ends. A steering column assembly 8 attached to the vehicle body with a bracket 6 rotatably supports an input shaft 10 and an output shaft 11, each having a steering wheel 9 attached to its upper end. A transmission device 2 is attached to the steering column assembly 8 and receives rotation of an electric motor 3 via a torque cable 4. The transmission device 2 includes a housing 30 on the input shaft side and a cover 31 on the output shaft side, which rotatably support the input shaft 10 and the output shaft 11 with two ball bearings 26, 27 and one ball bearing 29. , the housing 30 and the cover 31 are aligned and fitted with a spigot, and are connected by bolts (not shown). The input shaft 10 and the output shaft 11 are connected to a torsion bar 12 by two pins 13, and can be rotated relative to each other by twisting the torsion bar 12. It is supported by matched needle roller bearings 28 to ensure smooth relative rotation. This relative rotation of the input and output shafts is controlled by a stopper section 14 provided at the abutting section of both shafts.
The torsion bar 12 is restricted from being subjected to excessive torque. Fig. 3 shows the stopper part 14.
shows the structure of That is, two protrusions 32 are provided at the end of the input shaft 10 and fit into two notches 33 provided at the end of the output shaft 11 with a predetermined gap. After being allowed to rotate,
The protrusion 32 and the notch 33 are adapted to engage with each other. The input and output shafts 10 and 11 have flange portions 15 and 16 facing each other, and the flange portion 15 of the input shaft
Two pins 17 are press-fitted into the pin 17, a planetary gear 19 is rotatably fitted to the pin 17, and two pins 18 are similarly protruded from both sides of the flange 16 of the output shaft. Press-fitted and fixed, pin 1
A planetary gear 20 is attached to the part protruding toward the input shaft 10 side of 8.
are rotatably fitted, and both planetary gears 1
9 and 20 mesh with a common sun gear 21. Sun gear 21 includes input shaft 10 and output shaft 11
The output shaft 11 is rotatably supported at the shaft portion between the flange portions of the output shaft 11 . Further, the planetary gear 19 of the input shaft 10 meshes with a ring gear 22 rotatably fitted into the housing 30, and the planetary gear 20 of the output shaft meshes with a ring gear 23 fitted non-rotatably with the housing 30. A notch 34 is provided on the outer peripheral surface of the ring gear 22 on the input shaft side, into which the spherical head of the pin 24 fits. The other end of the pin 24 is fitted and fixed into a hole 37 provided in the center of the spool 25, and the spool 25 is slidably fitted into a hole 39 provided in the housing 30 in a direction perpendicular to the input shaft 10. ing. The hole 39 is closed at both ends with a lid 83 as shown in FIG.
5 are interposed respectively, and the spring 35 holds the spool 25 in the neutral position with an appropriate set load. Furthermore, a handle torque detection device 36 such as a potentiometer, differential transformer, pulse encoder, etc. that detects the position of the spool 25 and converts it into an electric signal is fixed to one end of the spool 25. The pin 85 is inserted through the hole provided in the lid 83 to the handle torque detection device 3.
Go in and out of 6. In addition, the reference numeral 38 in Fig. 4
housing 3 to allow movement of pin 24.
This is a hole made at 0.

Further, a planetary gear 41 is rotatably fitted into a portion of the pin 18 that is press-fitted into the flange portion 16 of the output shaft and protrudes toward the output shaft side, and a ring gear 40 that meshes with this is fixed to the housing 30 in a non-rotatable manner. , the sun gear 42 is rotatably supported on the outer periphery of the output shaft 11 and meshes with the planetary gear 41. Further, a spline on the inner circumference of a carrier 43 is engaged with the sun gear 42, and two pins 44 are press-fitted into the carrier 43, and a planetary gear 45 is rotatably fitted into each of the pins 44. A sun gear 46 and a ring gear 47 are meshed with the planetary gear 45. The sun gear 46 is rotatably supported on the outer periphery of the output shaft 11, and the ring gear 47 is rotatably fitted into the housing 30. A large number of recesses 52 having slopes as shown in FIG. 5 are provided on the outer periphery of the ring gear 47. As shown in FIG. A pin 54 driven by a solenoid 53 fixed to the outer surface of the housing 30 can protrude to the fitting surface of the housing 30 and the ring gear 47, and when the solenoid 53 is turned on, the pin 54 is driven by a solenoid 53 fixed to the outer surface of the housing 30.
4 engages with the recess 52, the ring gear 47 cannot rotate with respect to the housing 30, and when the solenoid 53 is turned off, the pin 54 comes out of the recess 52 by the force of the spring 55, and the ring gear 47 becomes rotatable. Solenoid 53 turns off and pin 5
4 is removed from the recess 52, the end of the pin 54 on the side opposite to the ring gear turns off the contact 77 provided on the power line connecting the solenoid 53 and the power source.
On the other hand, the sun gear 46 meshes with a spline on the inner surface of a reduction gear 48 rotatably supported on the output shaft 11 by a needle roller bearing 69, and rotates as a unit. The reduction gear 48 meshes with a small gear 49 provided on the reduction input shaft 84, and the reduction gear 48 and the small gear 49 are spur gears or helical gears that are highly efficient and capable of forward and reverse rotation other than a worm and a worm wheel. , bevel gears, etc. The deceleration input shaft 84 has two small diameter ball bearings 5 mounted on the housing 30 and the cover 31.
0, and is connected to the electric motor 3 by a torque cable 4, and the rotation of the electric motor is transmitted to the reduction gear 48 with little friction. If the torque cable 4 is bent to a large extent, friction will increase, so if necessary, it is preferable to adjust the direction of the deceleration input shaft 84 using a helical gear or a bevel gear.

Next, the operation of the transmission device will be explained.

When the input shaft 10 is rotated when there is no load torque on the output shaft 11 side, the ring gear 23 on the output shaft side of the first two sets of planetary gear sets is fixed, and the ring gear 22 on the input shaft side is moved by the spring 35. The output shaft 11, two sets of planetary gears 19, 20, and the sun gear 21 rotate, and the output shaft 11 rotates relative to the input shaft 10. Instead, it rotates in the same direction and at the same speed as the input shaft 10. When there is a load torque on the output shaft 11 side, the torsion bar 12 remains until the torque applied to the input shaft 10 overcomes the load torque.
is twisted, but the output shaft 11 does not rotate. Input shaft 1
When the rotational torque of the ring gear 22 caused by the zero input torque exceeds the torque that suppresses the rotation of the ring gear 22 due to the set load of the spring 35, the spring 35 and torsion bar 12 are deflected, the ring gear 22 rotates, and the spool 25 is rotated. Generates a displacement relative to the neutral position. If the input torque balances the load torque of the output shaft 11, the output shaft 11 will rotate for more input torque, and the common sun gear 2 will rotate.
1 rotates, so spring 35 and torsion bar 1
2 and the spool 25 remain displaced, and the input shaft 10 and output shaft 11 rotate in the same direction and at the same speed. Therefore, a handle torque detection device is formed by converting the magnitude and direction of the input torque into the displacement of the spool 25 due to the displacement of the spring 35 and the torsion bar 12, and converting the spool position into an electric signal. Further, the rotation of the electric motor is transmitted to the reduction input shaft 84 by the torque cable 4, and then to the pinion gear 49, the reduction gear 48, the planetary gear 45 meshing with the sun gear 46, and the ring gear 47 meshing with the planetary gear 45. 53, the planetary gear 45 rotates and revolves along the inner periphery of the ring gear 47, causing the carrier 43 to rotate. carrier 43
The rotation of is transmitted to the sun gear 42,
The rotation of is transmitted to the planetary gear 41, but since the ring gear 40 is fixed to the housing 30,
The planetary gear 41 rotates and revolves along the inner periphery of the ring gear 40, transmits its rotation to the flange portion 16 of the output shaft, and rotates the output shaft 11. ring gear 4
7 is not fixed by the solenoid 53, the ring gear 47 is rotated by the planetary gear 45, so that the planetary gear 45 does not revolve, that is, the carrier 43 does not rotate, and the rotation of the electric motor is not transmitted to the output shaft 11. That is, ring gear 47
The solenoid 53 and the like function as an electric clutch. Next, the configuration of the electrical control system shown in FIG. 6 will be explained.

An electrical signal indicating the direction and magnitude of the steering wheel torque is input from the steering wheel torque detection device 36 to the power supply control circuit 80, the clutch control circuit 79, and the motor control circuit 70. Further, signals from an information input device 81 such as a vehicle speed sensor or a detector that detects the position of a shift lever for operating a transmission that changes the number of engine rotations to be transmitted and converts it into an electrical signal are sent to a power supply control circuit 80 and a motor control circuit 70. is input. In addition, the solenoid 53 of the electric clutch
A signal from a clutch input detection device 82 that detects the input to the power supply control circuit 80 enters the power supply control circuit 80. Furthermore, a signal from a motor input detection device 78 that detects an input to a motor 74 including a drive circuit is transmitted to a power supply control circuit 80.
and is input to the clutch control circuit 79. Electric motor 7 including motor input detection device 78 and drive circuit
An automatic power switch 73 and a manual power switch 72 are provided on the power line connecting the automatic power switch 73 and the power source 71, respectively. In addition, the power line connecting the clutch input detection device 82 and the solenoid 53 of the electric clutch to the automatic power switch 73 has a contact 77 that is turned off by the pin 54 of the solenoid and a solenoid drive switch 76. A circuit is provided which places the switch 75 in parallel with the contact 77. In the timer switch 75, the timer switch 75 and the solenoid drive switch 76 are turned on at the same time, the solenoid 53 is activated, and the pin 54 pops out inward of the housing 30 to engage with the recess 52 of the ring gear 47, thereby closing the pressed connection 77. It stays on for a period of time until it turns on, and normally stays off. It also has a function that prevents it from entering the on state unless the command is reset. Power supply control circuit 80, clutch control circuit 7
9 and the motor control circuit 70 are connected in parallel to a power line branched from between the automatic power switch 73 and the manual power switch 72. The power supply control circuit 80 memorizes the conditions under which the electric motor and electric clutch enter the operating state, and always switches on the automatic power switch 73.
Turn on the handle torque detection device 3.
6. Information input device 81, motor input detection device 78
The signal input from the clutch input detection device 82 is compared and monitored with the stored conditions, and if a signal that does not match the stored conditions is received, the automatic power switch 73 is turned off and the system is switched to the manual steering device. For example, a stored operating condition corresponding to a signal from the information input device 81 such as a vehicle speed of 30 km or less or a shift lever position in the first or second forward gear or reverse, and a steering wheel torque of more than Kg/cm. With respect to the stored operating condition corresponding to the signal from the steering wheel torque detecting device 36, the electric motor input detecting device 78 still detects the electric motor input detecting device 78 even outside the operating condition such as when the vehicle speed is 60 km and the steering wheel torque is zero in the fourth forward gear.
When the signal from the clutch input detection device 82 continues to be received, the automatic power switch 73 is turned off. The clutch control circuit 79 stores the conditions under which the electric motor 74 is put into operation by the electric motor control circuit 70, and normally keeps the electric clutch solenoid 53 in the OFF state and receives the signal from the electric motor input detection device 82 and the steering wheel torque. The signals from the detection device 36 are compared, and only when they match the stored conditions, signals are sent to the timer switch 75 and the solenoid drive switch 76 to operate the solenoid 53 of the electric switch and connect the electric clutch. Thereby, when the electric motor rotates, the rotation of the electric motor is transmitted to the output shaft 11. Further, if the electric motor rotates even though the condition is not such that it should rotate, the electric clutch is not connected and the rotation of the electric motor is not transmitted to the output shaft 11. The electric motor control circuit 70 stores the conditions for the electric motor to enter the operating state, and operates the electric motor 74 when the signals from the steering wheel torque detection device 36 and the information input device 81 match the conditions. Note that the information input device 81 is not always necessary, and as in the above embodiment, the information input device 81
If this is provided, the steering can be switched from electric to manual based on factors other than the steering wheel torque, such as vehicle speed or the position of the shift lever, allowing a wide range of ranges of use to be selected. In addition, when the information input device 81 is a vehicle speed sensor, the gain of the motor control circuit 70 is changed to drive the motor in accordance with the vehicle speed, so that the motor is driven heavy for high vehicle speeds and light for low vehicle speeds. You can get a steering feeling that corresponds to the vehicle speed. Further, the automatic power switch 73 may be used as an alarm device.

FIG. 7 shows another embodiment in which the transmission device 2 is installed in the steering gear assembly 1 of a rack and pinion type steering device, and the structure of the transmission device 2 is the same as that in FIG. 2, and meshes with the rack of the rack shaft 5. A pinion (not shown) is provided on the output shaft 11, and the pinion shaft becomes the input shaft 10 at the upper part and the output shaft 1 at the lower part.
1. The electric motor 3 is mounted on the gearbox and connected to the transmission device 2 by a torque cable 4, but the operation and effect are the same as in the first embodiment.

In the electric power steering device of the present invention, a motor control circuit, a clutch control circuit, and a power supply control circuit are connected in parallel to a power supply, and a signal from a motor input detection device is input to the clutch control circuit, and a signal is input to the power supply control circuit. Since signals from the motor input detection device and clutch input detection device are input, the power supply control circuit memorizes the operating conditions of the motor and electric clutch, and if a signal different from the memory is input, it will turn off the power switch or issue an alarm. The operation of the electric motor and electric clutch is stopped by having the driver turn off the manual power switch. The clutch control circuit stores the operating conditions of the electric motor, and when a signal different from the stored signal is input, the electric clutch is not connected and the rotation of the electric motor is not transmitted to the mechanical steering system. In addition, the motor control circuit independently controls the motor according to the input torque regardless of the state of the other two circuits, so even in such cases, steering can be done electrically or manually. . In this way, even if individual control circuits fail, as long as one control circuit is intact, at least manual steering will be possible, and fatal dangers can be avoided. This has the effect of providing a type steering device. In addition, in embodiments equipped with an information input device, the signal is sent to the power supply control circuit, and the power supply control circuit operates the power switch according to the vehicle speed or the position of the shift lever. This has the effect of automatically selecting the area to be used as a steering device. When the information input device is a vehicle speed sensor, in addition to the above effects, the gain of the motor control circuit can be changed by a signal sent to the motor control circuit to obtain a steering feeling corresponding to the vehicle speed.
In addition, in an embodiment in which an automatic power switch or alarm device and a manual power switch are connected in series,
There is an advantage that the area of use as the power steering device and the manual steering device can be arbitrarily selected. Furthermore, in an embodiment in which a pin driven by a solenoid is engaged and disengaged from a recess having an inclined surface provided on the outer peripheral surface of a ring gear of a planetary gear reduction device in which an electric clutch is provided in a mechanical steering system, the clutch control circuit If the power control circuit fails and the automatic power switch remains on, or if the alarm device does not work and the manual power switch cannot be turned off, the motor control circuit also fails and the motor stops. Even in the worst case, where the ring gear continues to rotate in one direction or locks up and becomes unable to rotate, if the ring gear attempts to rotate due to excessive torque, the slope of the recess acts as a cam and the pin is subjected to the electromagnetic force of the solenoid. The vehicle is overcome and pushed back, the contacts on the power line are turned off, the electric clutch is disengaged, and the mechanical steering system is set to manual, so even if all three control circuits fail, there will be no loss of steering ability. Even in failure states such as power off, electric clutch off, and electric motor rotating freely with electric clutch on, no steering failure occurs.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which FIG. 1 is a conceptual side view of an electric power steering device, FIG. 2 is an enlarged longitudinal sectional view of a transmission device, and FIG. 3 is a view taken along the - line in FIG. FIG. 4 is an enlarged cross-sectional view along the - line in FIG. 2, and FIG. 5 is an enlarged cross-sectional view along the - line in FIG.
6 is a block diagram of the electric circuit, and FIG. 7 is a conceptual side view of the main parts of the electric power steering system showing another embodiment in which the transmission device is installed at a different location. It is. Explanation of symbols, 1: Steering gear assembly, 2:
Transmission device, 3: electric motor, 4: torque cable,
8: Steering column assembly, 9: Steering wheel, 10: Input shaft, 11: Output shaft, 12:
Torsion bar, 17, 20, 41, 45: Planetary gear, 21, 42, 46: Sun gear, 22, 2
3, 40, 47: Ring gear, 24: Pin, 2
5: Spool, 26, 27, 29, 50: Ball bearing, 30: Housing, 31: Cover, 34: Notch, 35: Spring, 36: Handle torque detection device, 43: Carrier, 48: Reduction gear, 49: Small gear, 52: recess, 53: solenoid, 54: pin, 55: spring, 70: motor control circuit, 71:
Power supply, 72: Manual power switch, 73: Automatic power switch, 74: Electric motor including drive circuit, 75:
Timer switch, 76: Solenoid drive switch, 77: Contact, 78: Motor input detection device, 7
9: Clutch control circuit, 80: Power supply control circuit, 8
1: Information input device, 82: Clutch input detection device, 84: Deceleration input shaft.

Claims (1)

[Scope of Claims] 1. A mechanical steering system including a steering gear that transmits steering torque applied to a steering wheel to steering wheels; a steering wheel torque detection device that detects the direction and magnitude of steering torque applied by human power;
an electric motor that supplies steering torque to a mechanical steering system;
an electric motor input detection device that detects input to the electric motor; a motor control circuit that controls driving of the electric motor based on a signal from the steering wheel torque detection device; and an electric clutch that transmits and interrupts rotation of the electric motor to a mechanical steering system; A clutch input detection device that detects input to the electric clutch, a clutch control circuit that drives the electric clutch based on signals from the steering wheel torque detection device and the motor input detection device, the steering wheel torque detection device, the motor input detection device, and the clutch input. It has a power supply control circuit that operates an automatic power switch provided in the electrical circuit from the power supply leading to the electric motor and the electric clutch according to the signal from the detection device, and the electric motor control circuit, the clutch control circuit, and the power supply control circuit are connected to the automatic power switch. Electric power steering device connected to the power source in parallel between the power sources. 2. The electric power steering device according to claim 1, wherein a signal from an information input device is input to the power supply control circuit and the motor control circuit. 3. The electric clutch has a pin driven by a solenoid that engages with a recess having an inclined surface provided on the outer peripheral surface of a ring gear of a planetary gear set in a mechanical steering system.
The electric power steering device according to claim 1, characterized in that the pin pushes against a contact point that turns off the power line of the solenoid when the pin is detached. 4. The electric power steering device according to claim 2, wherein the information input device is a vehicle speed sensor. 5. A mechanical steering system including a steering gear that transmits the steering torque applied to the steering wheel to the steering wheels, and a steering wheel torque detection device that detects the direction and magnitude of the steering torque generated by human power.
an electric motor that supplies steering torque to a mechanical steering system;
an electric motor input detection device that detects input to the electric motor; a motor control circuit that controls driving of the electric motor based on a signal from the steering wheel torque detection device; and an electric clutch that transmits and interrupts rotation of the electric motor to a mechanical steering system; A clutch input detection device that detects input to the electric clutch, a clutch control circuit that drives the electric clutch based on signals from the steering wheel torque detection device and the motor input detection device, the steering wheel torque detection device, the motor input detection device, and the clutch input. It has a power supply control circuit that operates an alarm device installed in the electric line from the power source leading to the electric motor and the electric clutch in response to a signal from the detection device, and a manual power switch installed between the alarm device and the power source. An electric power steering system in which a control circuit, a clutch control circuit, and a power supply control circuit are connected to a power supply in parallel between an alarm device and a manual power switch. 6. The electric power steering device according to claim 5, wherein a signal from an information input device is input to the power supply control circuit and the motor control circuit. 7. The electric clutch has a pin driven by a solenoid that engages with a recess having an inclined surface provided on the outer peripheral surface of a ring gear of a planetary gear set in a mechanical steering system.
6. The electric power steering device according to claim 5, wherein the pin pushes against a contact point that turns off the power line of the solenoid when the pin separates. 8. The electric power steering system according to claim 6, wherein the information input device is a vehicle speed sensor.