JPS6340717B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric power steering system, and particularly to an electric power steering system that improves production efficiency by sharing parts with a manual steering system. The present invention relates to an electric power steering system that can perform optimal power steering by adjusting the characteristics of the vehicle according to at least a vehicle speed signal.

Conventionally, hydraulic power steering systems have been widely used as power steering systems for automobiles. In other words, by using the rotational torque of the steering wheel shaft given by the steering operation, high-pressure fluid is supplied from the hydraulic pump to the power assist actuator according to the amount of movement of the hydraulic valve that is proportional to the magnitude of this rotational torque. This reduces the driver's operating force. However, with this device, the actuator is incorporated into the steering gear device, and the pressure chamber is required to have pressure resistance and sealing performance.
This requires higher mechanical precision than a manual steering device, and therefore, almost none of the device parts can be used in common with the manual steering device. In addition, since hydraulic pressure is used as the power source, the operating efficiency is very poor, and the friction loss at each seal is large, making the structure unnecessarily large and causing problems such as oil leakage from the seals. It was hot too.

On the other hand, recently developed electric power steering devices convert the rotational torque of the steering wheel shaft that should be increased into an electrical signal, and transmit the rotational driving force of the motor that operates accordingly to the steering gear device. It reduces the force required to operate the handle, and unlike conventional hydraulic types, it does not require piping or seal structures, allowing the device to be made more compact. It also has the advantage of being easier to reduce weight as it does not require pressure resistance. are doing.

However, in conventional electric steering systems, the motor is built into the gearbox, for example by arranging the shaft center parallel to the drive gear axis. They often have a special structure that is larger than the equipment. Therefore, the conventional electric steering system requires a unique component configuration, and the range of parts that can be shared with manual steering systems is relatively narrow, making it difficult to share parts across different models, which is desired in actual automobile production. It is still difficult to improve efficiency through this.

In addition, with conventional electric steering systems, power-assist driving force was obtained by simply converting the rotational torque of the steering wheel shaft that should be increased into an electrical signal, making it ideal for complexly changing vehicle driving conditions. There is a problem in that it is not possible to obtain a power assist operation that is accurate, and in particular, there is a problem in that it is not possible to obtain optimal steering characteristics depending on the vehicle speed or the size of the turning radius.

The present invention has been made with attention to these circumstances, and is an electric power steering system that can significantly improve production efficiency by sharing parts with general manual steering systems, and that can be easily applied to known systems. The purpose is to provide equipment.

Another object of the present invention is to provide an improved electric power steering system that can obtain motor control signals according to desired characteristics in view of the above-mentioned conventional problems.

The present invention is characterized by a servo motor or a servo motor which is rotated by an electric signal obtained by converting the displacement generated by a mechanically provided displacement generating means according to the operating resistance using a sensor and a servo device. , a pulse motor is mounted on the outer side of the steering gear device, with the rotational drive shaft connected to the opposite end of the steering wheel or the output shaft end of the steering gear device,
The motor mounting portion is removably installed in an opening provided in a gear box of the steering gear device, and the steering gear device can be used as a manual steering device with the servo device and electric motor removed; Further, when the servo device and electric motor are installed, this steering gear device can also be used as an electric power assist steering device.

As a result, the steering gear device has a shaft connection structure only at the end of the drive gear shaft opposite to the steering wheel shaft or at the end of the output shaft, and there is no need to make it particularly large, making it similar to a general manual steering device. This makes it possible to increase the efficiency of the device by making the gear devices and the like more versatile, and to make it possible to reduce the weight while still being equipped with a power assist device. Furthermore, since the servo mechanism is configured mechanically, the electrical control itself becomes simple and reliability can be improved.

Further, the feature of the present invention that achieves the above object is that desired conversion characteristics are set using at least the vehicle speed signal, and thereby stabilization during high-speed running or sudden rotation, or mitigation during large rotation operation, etc. can be achieved.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

This embodiment is applied to a rack and pinion type steering system, and the mechanism will first be explained with reference to FIG.

The device can be roughly divided into a mechanical displacement generating means 1 for the steering handle shaft, a sensor 2 that converts the displacement into an electrical displacement amount, a steering gear device 3, a servo device 4 that issues a predetermined control signal based on the sensor output, and It consists of a servo motor 5 for power increase that drives the steering gear device 3 according to the output of the servo device 4.

The displacement generating means 1 includes a torsion bar 6 that acts as a steering handle axis and which applies load resistance, and is integrally connected to this torsion bar 6 on the side of the steering handle 7, so that the displacement generating means 1 is in an unloaded state around the torsion bar 6, that is, in a state where it rotates in response to the steering handle 7. A cylindrical input shaft 8 is provided. When the operating handle 7 is rotated, the rotation angle Θi of the input shaft 8 is always larger than the rotation angle Θo of the torsion bar 6, that is, a rotational displacement (Θi - Θo) is generated.

The sensor 2 uses a potentiometer and is connected to the outer periphery of the input shaft 8 and the steering column 9.
It consists of a movable slip ring 10 and a fixed slip ring 11 which are attached at corresponding positions and slide into contact with each other. Each of the slip rings 10 and 11 changes the electrical resistance by changing the sliding contact position according to the rotation of the input shaft 8, and generates a voltage (VΘi - VΘo) corresponding to the rotational displacement via the derivation part 12. I have to.

The steering gear device 3 includes a pinion shaft 14 as a drive gear shaft connected to a torsion bar 6 and a rack 16 that meshes with the pinion teeth 15 inserted into a gear box 13, and can itself be used as a manual steering device. It is something. The gearbox 13 has an opening 17 along the axial direction that faces the end of the pinion shaft 14 on the side opposite to the torsion bar. Of course, in the present invention, when the steering gear device 3 is used as a manual steering device, the opening 17 is tightly closed by a closing lid, for example, by screwing the lid plate through a gasket. The opening can be easily closed by, for example,

The servo device 4 is integrated into the motor 5,
This motor 5 has a rotary shaft 18 connected to an end of the pinion shaft 14 on the side opposite to the torsion bar via a joint or a reducer 19, and is connected to an opening 17 of the gear box 13.
It is attached to the outside of the The pinion shaft 14 is rotated in response to a control signal from the servo device 4 to eliminate rotational displacement of the torsion bar 6. Note that as the motor 5, a DC servo motor or a pulse motor is used.

As described above, according to the present invention, the motor 5 is removably attached to the outside of the opening 17, and the opening 17 is formed in the gearbox 13 in advance, making the device a power assist device. Therefore, it is extremely easy to incorporate the motor 5 into the steering gear device 3. In particular, there is an advantage that the fixing flange of the motor 5 can be firmly fixed directly to the opening 17 by screwing or the like, and alignment of the motor shaft, pinion shaft, etc. can be performed extremely easily.

Next, the motor drive circuit will be explained with reference to FIG.

20 is an amplifier device for amplifying the sensor output; 21
22 is a motor main body, and 23 is a speed generator for controlling the motor speed.

A sensor output proportional to the difference (Θi - Θo) between the rotation angle Θi of the input shaft 8 and the rotation angle Θo of the pinion shaft 14 drives the motor body 22 via the amplifier device 20, the servo drive circuit 21, and the speed generator 23. The rotation is controlled and the pinion shaft 14 is rotated with increased force until the rotational displacement (Θi - Θo) becomes zero.

According to such a configuration, when the driver rotates the control handle 7, this movement is mechanically transmitted to the input shaft 8. Also, on the tire wheel side (not shown), there is a pinion shaft 1 from the torsion bar 6.
4. The steering force is transmitted through the rack 16 through a link type transmission system (not shown), and the torsion bar 6 is twisted by the resistance between the tires and the road surface. Therefore, the aforementioned mechanical rotational displacement (Θi-Θo) occurs between the input shaft 8 and the pinion shaft 14. Then, a resistance change occurs in the sensor 2 consisting of a potentiometer provided on the input shaft 8 in accordance with the rotational displacement, and an electrical output signal is thereby obtained. The motor 5 is rotationally driven in accordance with the converted control amount, and the power is increased in a direction such that the rotational displacement between the input shaft 8 and the pinion shaft 14 is always zero.

Unlike a hydraulic type, such an electric power steering device improves operating efficiency, and eliminates the need for pressure-resistant and seal structures, making the device configuration more compact and promoting the sharing of parts with manual steering devices. Of course, by mounting the motor 5 on the outside of the steering gear device 3, there is no need to give it a special shape or size unlike the internal type, and therefore parts can be shared with the manual steering device. This makes it possible to achieve a significant reduction in energy consumption compared to conventional electric types, and also to reduce weight.

It should be noted that the present invention can be implemented in various forms other than the embodiments described above, and other embodiments will be described below. Note that the same parts in the drawings are designated by the same reference numerals as those in FIGS. 1 and 2, and the explanation thereof will be omitted.

In FIG. 3, a rotational displacement meter corresponding to a rotary encoder is used as the sensor 2 that converts rotational displacement into an electric signal, and a brush 24 is used on the displacement extraction side, and the sensor 2 is connected between the motor 5 for power boosting and the pinion shaft 14. An example is shown in which a harmonic drive type reducer 19 is used as the reducer 19 installed in the motor. Of course, even with such a device, the same effects as those of the above embodiment can be achieved.

FIG. 4 shows a recirculating ball screw type steering device implemented. In this case, the driving gear shaft to be increased in force is connected to a ball nut 25 and a driving worm shaft 26.
It is composed of: In this case as well, the worm shaft 26 is rotationally driven by driving the motor 5 according to the rotational displacement, similarly to the embodiment described above, and the same force-increasing effect as described above can be achieved.

5 and 6 show an example in which displacement detection of the steering handle shaft and sensor is replaced with axial displacement. That is, in the embodiment described above, the displacement of the input shaft 8 is detected as the amount of displacement in the rotational direction, that is, the rotational displacement, but since the sensor itself rotates, the output signal is taken out via the slip ring. In this embodiment, the ball 2 of the helical cam groove 27 is formed on the outer peripheral surface of the input shaft 8 to compensate for the phase difference caused by the relative rotation between the input shaft 8 and the pinion shaft 14.
8 and its input shaft 8 in the axial direction, and the sleeve 29 is coaxially interlocked with the ball 28 for detection, thereby eliminating the need for a slip-ring mechanism. . A voltage output as an axial displacement amount is generated by a magnetic scale 30 provided on the outer periphery of the sleeve 29 and biased toward the ball side by a spring 30A, and a head 31 corresponding to the scale 30.

It goes without saying that even with such a configuration, it can be applied to, for example, a rack-and-pinion type device to perform a force-increasing action, just as the displacement detection direction is different.

FIG. 7 shows an example in which the axial displacement generating means is applied to a recirculating ball screw type steering device. A displacement generating disk 34 is attached to the worm shaft 32 via a spring holding portion 33 in response to minute axial movement of the worm shaft 32.
A driven pin 35 is provided on the outer periphery of the displacement generating disk 34 in parallel with the worm shaft 32 so as to be movable therewith. A displacement meter 37 such as an electromagnetic device is provided as a sensor at a corresponding portion of the driven pin 35 and the fixed housing 36.

The worm shaft 32 has a sector shaft 38, a ball nut 39, and a ball 40 due to road resistance and other factors.
The steering wheel receives an effect of moving in the direction of motion during steering operation. Based on this action, the displacement generating disk 34
An electrical output is generated by the displacement meter 37 via the servo circuit, and is inputted to the above-mentioned servo circuit.

Even with such a configuration, the force increasing effect based on the generation of rotational displacement of the steering handle shaft can be achieved in the same manner as in the above embodiment.

Note that the movement of the displacement generating disk 34 may be detected by a link mechanism (not shown).

FIG. 8 shows an example of application of the motor drive circuit.

That is, in a power steering system, in addition to obtaining an assist force that is simply proportional to the steering torque, the assist force is often made to follow a complex characteristic curve that takes into account vehicle speed, steering rotation amount, and other characteristics. In consideration of such a case, a characteristic conversion circuit 41 for inputting predetermined information to the servo drive circuit 21 is incorporated. In this way, it is possible to stabilize the vehicle during high-speed running or rapid rotation, or to reduce the burden during large rotation operation.

FIGS. 9 and 10 show further different motor control applications. FIG. 9 is a block diagram for obtaining a predetermined electrical characteristic curve. The characteristic conversion section 50 is a microcomputer, and an A-D conversion circuit 51, a D-A conversion circuit 52, a digital input circuit 53, a microprocessor 54, an operation program and characteristic data storage memory 55, a digital output circuit 56, and these are combined. A common bus wiring 57 is provided.

As input elements to this characteristic conversion section 50, a displacement detector 58 and its amplifier 59, and a vehicle speed detector 6 are used.
0, its amplifier 61, and characteristic selection switch 62
It is equipped with It also includes a servo motor drive section 63 and a monitor display section 64 as output elements.

FIG. 10 is an operation flowchart of the apparatus shown in FIG. 9. In the first determination, it is determined whether the boost function is on or off, and if it is on, the process proceeds to sampling processing. In the sampling process, a displacement input Di, a vehicle speed input Vi, and an output So are input and stored in the memory 55. Next, in the abnormality processing determination, the following three points are mainly determined.

a Even after a certain period of time has elapsed, Dkl<Di<Dku However, when Dku...upper limit setting value Dkl...lower limit setting value, the NG flag is set to 1. This determination occurs when the system response is insufficient. This means that the motor operates only by the component of Di,
This corresponds to an abnormal feedback operation that causes Di to approach zero.

b D-A conversion output values So and A-D seen from the CPU
When the conversion input value So is not equal, the NG flag is set to 1. This determination is aimed at determining abnormalities in the analog signal processing system.

C Program inside the microcomputer 50
When an NG occurs, set the NG flag to 1.

In addition, in order to automatically set the So signal to zero when control becomes impossible due to a drop in output, the So signal is passed through the digital output circuit 56, and the So signal is forcibly set to zero when the output drops (relay contact opens).

In the next determination, the NG flag is checked.
If NG, proceed to abnormality display processing; if OK, proceed to characteristic conversion processing.

The output S′o and the directional output cw/ccw are calculated based on the characteristic conversion input values Di and Vi. After that, in output processing, S′o and either cw or ccw are output. If the determination is OFF or NG, output processing of S'o=0 is performed in steps and then stopped.

Also, the output S′o is determined by the characteristic conversion input values Di and Vi.
In the process of calculating, a calculation formula is stored in a program memory in advance, and the program is processed so that the parameters of the calculation formula are automatically changed in accordance with the characteristic selection input. Of course, it is possible to obtain the output S'o from the characteristic conversion input Di without the vehicle speed input signal, but in this case, the characteristics cannot be optimized depending on the vehicle running.

As described in detail in the above embodiments, the present invention connects the rotary drive shaft to the end of the driving gear shaft opposite to the steering wheel or the output shaft. By connecting it to the end and attaching it to the outside of the steering gear device, the steering gear device does not need to be particularly large and can be used in common with a general manual steering device. As a result, it is possible to improve the efficiency of parts by generalizing the gear devices used, so it is possible to improve factory productivity by sharing parts to a large extent, which has not been possible with conventional electric power steering systems. At the same time, it is possible to improve the utilization of parts by applying it to a known device, and the intended purpose can be achieved.

Further, according to the present invention, when the servo device supplies the servo control signal to the electric motor, the servo control signal can be converted in accordance with characteristics selected depending on at least the vehicle speed and other vehicle running conditions. , This makes it possible to obtain the optimum power assist operation for various vehicle driving conditions.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention,
Figure 1 is a schematic sectional view, Figure 2 is a circuit diagram, Figures 3-
5 is a schematic sectional view showing other embodiments of the present invention, FIG. 6 is a sectional view taken along the line -- in FIG.
9 to 9 show still other embodiments of the present invention, FIG. 7 is a schematic sectional view, FIGS. 8 and 9 are different circuit diagrams, and FIG. 10 is an explanatory diagram of the operation of FIG. 9. It is. DESCRIPTION OF SYMBOLS 1... Displacement generating means, 2... Sensor, 3... Steering gear device, 4... Servo device, 5... Motor,
6... Control handle axis.

Claims (1)

[Scope of Claims] 1. A steering gear, in which a drive gear shaft connected to the steering handle is rotatably supported in a gearbox in order to convert rotational movement of the steering handle into steering movement of a link type transmission system. a device; a displacement generating means provided on the steering wheel shaft for mechanically generating a displacement according to the rotational torque of the steering wheel shaft; and a displacement generating means attached to the displacement generating means for converting the displacement into an electrical displacement amount. a sensor; a servo device connected to the sensor and generating a predetermined motor control signal; and a servo device connected to the servo device and driven to rotate in response to the control signal of the servo device to remove the displacement of the steering handle shaft. an electric motor, the electric motor is removably installed in an opening opened along the axial direction of the drive gear shaft on the side opposite to the steering handle of the gear box of the steering gear device, and the electric motor A rotating shaft of the type motor is coupled to the drive gear shaft, and the steering gear device can be used as a manual steering device with the servo device and the electric motor removed, and the servo device and the electric motor are connected to the steering gear device. An electric power steering device characterized in that it can also be used as an electric power assist steering device when installed. 2. A steering gear device in which a drive gear shaft connected to the steering handle is rotatably supported in a gearbox in order to convert rotational movement of the steering handle into steering movement of a link type transmission system; and a steering handle shaft. a displacement generating means for mechanically generating a displacement according to the rotational torque of the steering handle shaft; a sensor attached to the displacement generating means for converting the displacement into an electrical displacement amount; a servo device connected to the servo device to generate a predetermined motor control signal; and an electric motor connected to the servo device and driven to rotate in order to eliminate the displacement of the steering handle shaft in response to the control signal of the servo device. The electric motor is removably attached to an opening opened along the axial direction of the drive gear shaft on the side opposite to the steering handle of the gear box of the steering gear device, and the rotation shaft of the electric motor is The steering gear device is coupled to the drive gear shaft, and the steering gear device can be used as a manual steering device when the servo device and the electric motor are removed, and can be used as an electric steering device when the servo device and the electric motor are installed. The servo device has a characteristic of inputting at least a vehicle speed signal and converting the electrical displacement amount of the steering wheel shaft into a motor control signal according to a characteristic curve corresponding to the running state of the vehicle. What is claimed is: 1. An electric power steering system comprising a conversion circuit and adapted to match a power assist force to a selected characteristic depending at least on vehicle speed. 3. The electric power steering system according to claim 2, wherein the characteristic conversion circuit includes a memory that stores a plurality of characteristic data and a characteristic selection switch that selects the plurality of data.