JPH0580390B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electric power steering device that reduces the steering force of a steering system by applying electric power to the steering system. related to temperature control.

(Prior Art) In general, an electric power steering device includes an electric motor that is an auxiliary torque generation source to reduce steering force, a reduction mechanism that transmits the torque generated by the electric motor to an output shaft, and a steering system. The motor is equipped with a control device including a microcomputer that collects steering information such as rotational speed and steering torque, and calculates and determines the torque to be generated by the electric motor.

This type of electric power steering device is
Various types of devices are known, such as those installed around the steering shaft and those configured in connection with the rack and pinion. On the other hand, there are various types of speed reduction mechanisms, such as those using a gear mechanism and those using a ball screw mechanism, and these speed reduction mechanisms are connected directly to an auxiliary torque generating electric motor or via a cog belt or the like.

In this case, the steering system from the steering shaft to the rack shaft has many bearings and seal members for supporting the steering shaft and the rack shaft, and friction occurs in these parts. Further, various types of friction occur in the reduction mechanism of the electric power steering device and in the connection between the electric motor and the reduction mechanism. Lubricating oil is used to reduce such friction and make each part operate smoothly. Other benefits of lubricating oil include improving durability, preventing rust, and reducing operating noise.

(Problems to be Solved by the Invention) As described above, the lubricating oil used in each part of an electric power steering device generally has a high viscosity at low temperatures and a low viscosity at high temperatures. For this reason,
In a low-temperature atmosphere, viscous resistance increases, and the resistance increases depending on the steering rotation speed.
The starting torque increased, which decreased the steering feel of the steering system. In other words, due to changes in the viscosity of the lubricating oil during steering operations, (1) the torque is large at the start of the steering and the steering feeling is not smooth, and (2) as the steering rotation speed increases, the resistance increases and remains constant. There was a risk that a light steering feeling could not be obtained, and (3) the return speed of the steering wheel would be inappropriately reduced, causing the steering feeling to become sluggish during return.

(Objective of the Invention) Therefore, an object of the present invention is to provide an electric power steering device in which stable steering feeling can always be expected without being affected by ambient temperature.

(Means and effects for solving the problem) In order to achieve this object, according to the present invention,
An electric motor that detects the steering state of a steering system to obtain steering information, generates an auxiliary torque in an electric motor based on the detected steering information, and applies this auxiliary torque to the steering system to reduce steering operation. In the type power steering device, a temperature detection means for detecting the temperature of the device;
The apparatus is configured to include a heat generating means disposed in the lubricating oil system of the apparatus, and a temperature control means for controlling the amount of heat generated by the heat generating means based on the temperature detected by the temperature detecting means, so that the temperature around the apparatus changes. The temperature of the lubricating oil system of the equipment is controlled to be approximately constant even when Therefore, the viscosity of the lubricating oil is maintained substantially constant.

(Embodiments of the invention) Examples of the invention will be described below with reference to the accompanying drawings.

As can be seen from the drawings, the electric power steering device of this embodiment is assembled into a rack-and-pinion mechanism composed of a rack shaft 21 and a pinion gear 22 that meshes with a rack gear on the rear right side of the rack shaft 21 in the drawing. ing. The pinion gear 22 is formed on a pinion shaft 22a, and both ends of the pinion gear 22 are rotatably supported by angular contact bearings 23 and 24. The pinion gear 22 is also pressed in the direction of the input shaft 26 by a bolt 25 ringed at the bottom of the bearing 24. has been done. The input shaft 26 is connected to a pinion shaft 22a at one end of the pinion gear 22 via a torsion bar 27. A bearing 26a is disposed between one end of the input shaft 26 and the pinion shaft 22a, and a bearing 34 is disposed at the other end of the input shaft 26, so that the input shaft 26 is supported by the same rotating shaft. On the inside of the pinion shaft 22a, two protrusions 22b having a substantially fan-shaped cross section are integrally formed at positions separated by about 180 degrees on the inner peripheral surface. A groove having a fan-shaped cross-sectional shape complementary to the cross-sectional shape of the protrusion 22b is formed in the input shaft 26 at a position corresponding to the protrusion 22b. Therefore, although the input shaft 26 and the pinion shaft 22a can rotate relative to each other to a certain extent,
Anything beyond that rotates as a unit.

A steering torque detection sensor 35 is provided on the outer periphery of the pinion shaft 22a near where the protrusion 22b is formed.
The steering torque detection sensor 35 electrically detects the displacement of the slider 29 that moves in the axial direction as the input shaft 26 and pinion shaft 22a rotate relative to each other. The slider 29 is generally cylindrical and has axially parallel slots 29a-29a bored in its side surfaces at symmetrical positions 180 degrees apart. Also,
Diagonal slots 29b-29b having a constant angle with respect to the axial direction are bored in the side surfaces of the slider rotated 90 degrees from the slots 29a-29a, respectively. This slider 29 is fitted onto the input shaft 26 and pinion shaft 22a. At this time, the parallel slots 29a-29a engage with the pins 22c-22c provided on the protrusion of the input shaft 26, and the diagonal slots 29b-29b engage with the protrusion 22b of the pinion 22a.
so as to engage with the pins 30-30 provided in the.
According to such a configuration, the torsion bar 27 relatively rotates the input shaft 26 and the pinion shaft 22a in proportion to the steering torque, and the slider 29 converts the relative rotation in proportion to the steering torque into an axial displacement. do.

This displacement of the slider 29 is determined by the slider 2
A differential transformer 31 provided on the outer periphery of the steering wheel 9 with an appropriate gap therebetween converts the signal into an electric signal to obtain a steering torque detection signal. The differential transformer 31 has a primary winding 31a,
It consists of secondary windings 31b and 31c, both of which are fixed to a pinion case 33. Primary winding 3
An AC pulse signal is applied to 1a from a main controller (not shown), and analog pulse electric signals are differentially taken out from secondary coils 31b and 31c. That is, if there is no relative rotation as described above, the slider 29
is at the initial position, the difference between the output signals of the secondary coils 31b and 31c is zero, and the secondary coils 31b and 31
The difference between the output signals of c is changed.
Therefore, the output signal of the differential transformer 31 is proportional to the relative rotation of the input shaft 26 and the pinion shaft 22a, that is, the steering torque.

A steering rotation detection sensor 40 is provided near the bearing 28 that supports the input shaft 26. The steering rotation detection sensor 40 includes a gear 36 coaxially mounted on the input shaft 26, a DC generator 37, and a small diameter gear 3 fixed to the rotating shaft of the DC generator 37 and meshing with the gear 36.
8. Therefore, the rotational direction and rotational speed of the input shaft 26 can be detected from the output signal of the DC generator 37.

On the other hand, on the other end side of the rack teeth 4 of the rack shaft 21, there is a ball screw mechanism 7 and a large diameter toothed pulley 8.
, a timing belt 9, and an electric motor 10 having a small-diameter toothed pulley 10a pivoted thereon. Rotation of the electric motor 10 is transmitted to the ball screw mechanism 7 via the pulley 10a, the timing belt 9, and the pulley 8. This ball screw mechanism 7 decelerates the rotation of the electric motor 10 and transmits it to the rack shaft 21.
This is converted into a linear motion of the rack shaft 21.

To explain these in more detail, the opposite side of the rack shaft 21 to the meshing portion with the pinion gear 22 is supported by the case 16 by a spherical bearing 13 so as to be swingable and axially freely. A ball screw groove 16a is formed on the outer periphery of this portion of the rack shaft 21.
This ball screw groove 16a has a similar screw groove 17a.
A ball nut 17 having an inner peripheral surface thereof is mounted around the ball nut 17. A plurality of balls 1 are provided between the thread groove 17a of this ball nut 17 and the ball thread groove 16a.
8 is fitted and rolls between both screw grooves 16a, 17a to form a circulation path provided in the ball nut 17 and circulate. Therefore, the rotation of the ball nut 17 is smoothly converted into a linear motion of the rack shaft 21 via the balls 18. The ball nut 17 is connected to the pulley case 1 from both ends via elastic members 11 and 12.
They are sandwiched between the pulley case 9A and the pulley case 19B, thereby being elastically engaged. Pulley case 19
A, 19B are angular contact bearings 20, 3
4 is rotatably supported by the case 16. A large diameter pulley 8 is integrally provided on the outer periphery of the pulley case 19A, and a small diameter pulley 10a of the electric motor 10
The rotation of the electric motor 10 is transmitted by the timing belt 9 wound between the two. This electric motor 10
is controlled by a control device (not shown) based on steering information that is an output signal of the steering torque detection sensor 35 and the steering rotation sensor 40.

Furthermore, the apparatus is equipped with a temperature control system consisting of a temperature detection means 50, a heat generation means 51, and a temperature control circuit 52. That is, inside the case 16, between the large diameter pulley 8 and the small diameter pulley 10a, a thermistor (temperature detection means) 50 for detecting the temperature inside the case is provided. Also, case 16
Inside, on the right side of the ball screw mechanism 7, that is, closer to the pinion gear 22, a heater coil (heat generating means) 51, which is a heat generating means, is fixed along the inner surface of the rack shaft 21. The heater coil 51 generates heat when energized and heats the inside of the case 16, that is, heats the lubricating oil inside the case 51. thermistor 50
constitutes one arm of a bridge circuit comprising resistors 54, 55, and 56 of the temperature control circuit 52 in each arm. Here, the resistor 54 and the thermistor 50 are connected in series with each other, and the resistor 54
One end of the thermistor 50 is connected to a power supply line 53, and one end of the thermistor 50 is connected to ground. Further, resistors 55 and 56 are also connected in series, and the resistor 5
One end of 5 is connected to a power supply line 53, and a resistor 56
One end is connected to ground. The resistor 56 is a variable resistor and is used to set the temperature to be detected. A node between the thermistor 50 and the resistor 54 connected in series, and a node between the resistor 55 and the variable resistor 56 connected in series are each connected to an input end of an operational amplifier 57. The output end of operational amplifier 57 is connected to one end of relay coil 58.
The other end of this relay coil 58 is a relay contact 58
It is connected to the ground side together with one end of a. Relay contact 58a forms part of a closed circuit connecting heater coil 51, battery power supply 59, main switch 60, and fuse 61, and controls energization to heater coil 51.

In this case, the relationship between the bridge circuit and the operational amplifier 57 is set as follows. That is, when a predetermined reference temperature is set by the variable resistor 56 and the thermistor 50 indicates a resistance value corresponding to the reference temperature, the input voltage of the operational amplifier 57 is set to zero. Correspondingly, when the thermistor 50 exhibits a resistance value corresponding to a temperature equal to or higher than the reference temperature (generally lower than the resistance value at the reference temperature), the input voltage of the operational amplifier 57 becomes negative, and the thermistor When 50 exhibits a resistance value corresponding to a temperature below the reference temperature (generally higher than the resistance value at the reference temperature), the input voltage of the operational amplifier 57 is set to be positive. For such an input signal, the operational amplifier 57 outputs a low level and does not energize the relay 58 when the input signal is 0 or negative, and does not energize the relay 58 when the input signal is positive. The level is high and the relay 58 is energized.

Therefore, according to such a temperature control system, firstly, if the temperature inside the case of the steering device is equal to or higher than the reference temperature as determined by the temperature detection by the thermistor 50, the heater coil 51 is not energized and each friction portion is turned off. to obtain the specified resistance. Also,
Second, when the temperature inside the case of the steering device is below the reference temperature, the heater coil 51 is energized based on the prediction that the steering resistance will increase due to the increase in the viscosity of the lubricating oil, and the temperature inside the case is lowered. The viscosity resistance of the lubricating oil is controlled so that it reaches the desired value.

Therefore, the reference temperature is such that the heater coil 51 is energized at a temperature below a certain reference temperature to obtain a predetermined frictional resistance in each part of the steering device, and when the temperature exceeds the reference temperature, the energization is stopped and the frictional resistance is reduced. This will stop the decrease in the steering wheel and provide a stable steering feel at all times.

Although this embodiment uses a bridge circuit to control the temperature by turning on and off the heater coil 51, it is also possible to detect temperature using a circuit other than the bridge circuit. In addition, in the above embodiment, the current flowing to the heater coil is not controlled, but the temperature of the steering system is monitored at fixed timing using a microcomputer, etc., and the current flowing to the heater coil is continuously controlled. However, it is also possible to maintain a constant temperature in the steering system.

(Effects of the Invention) According to the present invention, as described above, the heating means is disposed in the lubricating oil system inside the device, and the heat generation amount of the heating means is controlled to maintain the temperature of the lubricating oil at a substantially constant level. Therefore, it is possible to obtain an electric power steering device in which the viscosity of the lubricating oil can be kept constant and stable steering feeling can always be expected without being affected by ambient temperature.

[Brief explanation of the drawing]

The accompanying drawing is a partially cutaway sectional view of an electric power steering device according to an embodiment of the present invention. In the drawings, 10 is an electric motor, 16 and 33
5 is a steering system case, 50 is a temperature detection means, 51 is a heat generating means, and 52 is a temperature control means.

Claims (1)

[Claims] 1. An electric power steering device that applies electric motor power to the steering system to reduce steering force, comprising: a temperature detection means for detecting the temperature of the device; and a temperature detection means disposed in the lubricating oil system of the device. An electric power steering device comprising: a heat generating means; and a temperature control means for controlling the amount of heat generated by the heat generating means based on the temperature detected by the temperature detecting means.