JPH0530670B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a rack and pinion type steering device, and more particularly to a rack and pinion type steering device that increases or decreases the frictional force between a steering rack and a steering pinion depending on the driving condition of a vehicle. It is related to the device.

[Prior Art] Conventionally, there is a steering device that uses a rack and pinion type steering gear that converts rotational movement of a steering pinion into axial movement of a steering rack. In this steering device, the running stability, steering force, etc. of the vehicle are greatly affected by the gear ratio and frictional force between the steering rack and the steering pinion in the steering gear box.

Normally, in manual steering vehicles, the gear ratio between the steering rack and the steering pinion is determined by taking into consideration the case where large steering angle steering is performed in which the torque generated around the king pin increases when the vehicle is stopped or running at low speed. Therefore, when driving in a straight line, where the torque generated around the king pin is small, especially when driving straight at high speed, the steering force near the neutral position of the steering wheel becomes too light, resulting in excessive steering, and the resulting correction steering, etc., which may cause the vehicle to stabilize in a straight line. There was a problem when sex decreased. In addition, in power steering vehicles, since there is hydraulic assistance during steering operation, the gear ratio can be determined almost unaffected by the torque generated around the king pin, and problems due to gear ratios are unlikely to occur like in the above manual steering vehicles, but the steering Since there is some hydraulic assistance even when in neutral, the steering force becomes too light,
There was a problem that the straight-line stability of the vehicle deteriorated. Therefore, conventionally, the steering rack that engages with the steering pinion is pressed by the mounting load of a spring provided via a rack guide, and a frictional force is applied between the steering pinion and the steering rack, thereby increasing the steering force when driving straight. However, in this case, it is difficult to adjust the steering rack pressing pressure, and even once it is set, the frictional force disappears due to changes over time, requiring adjustment work again.

In addition, this rack and pinion type steering device has the characteristics of high rigidity and light weight, and because of this high rigidity, when driving on rough roads such as rough roads, it is difficult to handle due to unevenness of the road surface. The force that tries to move the tire is applied and the steering wheel receives a shock in the circumferential direction, which is the tendency for so-called "knockback" to occur. At the same time, a knocking sound is generated from the meshing part between the steering rack and the steering pinion, the rack housing and the rack guide, etc., which may cause a noise to the driver. There were times when I felt uncomfortable. Conventional countermeasures have been to reduce the distance between the rack guide and the cap, which absorbs the misalignment between the steering rack and the steering pinion, and to further increase the mounting load of the spring that presses the steering rack. It is difficult to adjust the distance between the rack guide and the cap during the manufacturing process, and even if the distance can be adjusted well, the distance and spring mounting load may change over time due to wear between the steering rack and steering pinion. Therefore, readjustment was necessary, and in the end it was not a perfect solution.

Furthermore, when a vehicle is running at high speeds, there is a problem of unbalance of the tires themselves and the occurrence of flutter due to poor uniformity.One way to counter this problem is to absorb vibrations within the steering gear box. . In other words, similar to the above, attempts are being made to prevent flutter by increasing the spring mounting load to increase the friction force between the steering rack and steering pinion, or by installing a damper. However, due to changes over time, it was not a sufficient countermeasure.

[Object of the Invention] Therefore, the present invention controls the frictional force between the steering rack and the steering pinion using hydraulic pressure adjusted according to the driving condition, and prevents changes over time due to wear and the like between the steering rack and the steering pinion. To provide a rack and pinion type steering device capable of preventing jerking, tapping noise, and flutter without being affected by the noise, and improving the steering feeling when the vehicle is traveling, especially when traveling straight at high speed.

[Configuration of the Invention] The configuration of the present invention to achieve the above object includes: a vehicle speed sensor that detects the body speed of the vehicle; an acceleration sensor that detects the axial acceleration of the tie rod; an electronic control circuit that receives a detection signal and outputs a drive signal to a hydraulic pressure adjustment valve described below; a hydraulic pressure adjustment valve that adjusts the hydraulic pressure generated by the hydraulic pump in accordance with the drive signal from the electronic control circuit; and the hydraulic pressure adjustment. a steering gear box provided with a rack guide that presses the steering rack according to the oil pressure adjusted by a valve and increases or decreases the frictional force between the steering rack and the steering pinion; the electronic control circuit includes: the acceleration sensor; Based on the detection signal from
a first control signal generating means for outputting a first control signal for increasing the frictional force between the steering rack and the steering pinion in response to an increase in the axial acceleration of the tie rod; and a first control signal generating means based on a detection signal from the vehicle speed sensor. a second control signal generating means for outputting a second control signal for increasing the frictional force between the steering rack and the steering pinion in accordance with an increase in the vehicle speed only when the vehicle speed exceeds a predetermined value; and a drive signal for driving the oil pressure regulating valve in response to a signal obtained by adding a second control signal from the second control signal generating means and a first control signal from the first control signal generating means. The gist of the invention is a rack and pinion steering device characterized by comprising: drive signal generating means for generating and outputting a drive signal;

[Operation and Effects of the Invention] In the present invention, the first control signal generating means adjusts the steering according to the increase in the axial acceleration of the tie rod, based on the detection signal from the acceleration sensor that detects the axial acceleration of the tie rod. A first control signal is output for increasing the frictional force between the rack and the steering pinion. Further, the second control signal generating means performs second control to increase the frictional force between the steering rack and the steering pinion in response to an increase in the vehicle body speed, based on a detection signal from a vehicle speed sensor that detects the vehicle body speed. signal,
Outputs only when the vehicle speed exceeds a predetermined value.
Then, the drive signal generating means generates and outputs a drive signal for driving the oil pressure regulating valve according to the signal obtained by adding the first control signal and the second control signal. In response to the drive signal, a hydraulic pressure regulating valve regulates the hydraulic pressure generated from the hydraulic pump. In response to the adjusted oil pressure, a rack guide in the steering box presses against the steering rack, increasing or decreasing the frictional force between the steering rack and the steering pinion.

Therefore, according to the present invention, the frictional force between the steering rack and the steering pinion is increased as the axial acceleration of the tie rod increases.
For example, when the axial acceleration of the tie rod increases on a rough road with many irregularities, the frictional force between the steering rack and the steering pinion can be increased to make it difficult to cause kickback. Similarly, when an impact force is transmitted from the tie rod to the steering gear box side, it is possible to prevent the occurrence of hammering noise from the meshing portion between the steering rack and the steering pinion.

Furthermore, in the present invention, when the vehicle speed exceeds a predetermined value, the frictional force between the steering rack and the steering pinion is increased in accordance with the increase in vehicle speed. It is possible to increase the response and improve the driving stability and steering performance of the vehicle. In addition, it is also possible to prevent flutter that tends to occur during high-speed driving.

Moreover, when the vehicle is running at low speeds, i.e., the vehicle speed is below a predetermined value, a light steering feeling can be achieved without increasing the frictional force between the steering rack and the steering pinion.

Additionally, in the present invention, the frictional force between the steering rack and the steering pinion is increased or decreased based on the drive signal generated and output by the drive signal generation circuit by adding the first control signal and the second control signal. Therefore, for example, even when the same sudden steering is performed, when the vehicle is running at a low speed below a predetermined value, the abruptness of the steering (more precisely, the axial acceleration of the tie rod according to the amount of steering; the same applies hereinafter) is independent of the vehicle speed. However, when the vehicle speed exceeds a predetermined value, the rudder response is increased according to the increase in vehicle speed plus the abruptness of the steering.
As the speed increases, running stability and steering performance can be further improved.

[Example] Next, the present invention will be explained by giving an example and referring to the drawings.

FIG. 1 shows a schematic system diagram of the rack and pinion type steering device of this embodiment. In the figure, S is the steering wheel, 1 is the steering gear box, 2 is the tie rod, and 3 is the tie rod 2 attached near the tie rod 2. 4 is a vehicle speed sensor that generates a signal according to the running speed of the vehicle; 5 is an acceleration sensor for detecting the axial acceleration of the vehicle;
6 is an electronic control circuit, 6 is a hydraulic pressure regulating valve section, 7 is a transmission, 8 is a hydraulic pump driven by the transmission 7, 9 is a pressure sensor, and 10 is a hydraulic pipe.

The hydraulic pressure regulating valve section 6 includes an electromagnetic solenoid 11 that is driven by a drive signal generated from the electronic control circuit 5.
, a spool valve 12 that opens and closes as the electromagnetic solenoid 11 moves, and a spool valve 12
It consists of a fixed throttle 13 to ensure the necessary oil pressure when the oil pressure is low when the valve is closed, and the oil pressure output from the hydraulic pump 8 is adjusted to adjust the oil pressure according to the traveling speed of the vehicle and the axial acceleration of the tie rod 2. It is to be adjusted to.

The oil pressure adjusted by the oil pressure adjustment valve section 6 (hereinafter referred to as adjustment oil pressure) is introduced into the steering gear box 1 via the hydraulic pipe 10, and the steering gear box 1 is connected to the steering pinion 21 and the steering wheel. In order to increase or decrease the frictional force with the rack 22 by adjusting hydraulic pressure, a rack guide 23 that directly presses the steering rack 22, a gear housing 24, and a rack guide cap 2 are provided.
5 to form a cylinder chamber 26, and by introducing the adjusted hydraulic pressure into this cylinder chamber 26, the pressing pressure of the steering rack 22 of the rack guide 23 is controlled, and the frictional force between the steering pinion 21 and the steering rack 22 is increased or decreased. Being in control. Note that a sealing material 27 is interposed between the rack guide 23 and the rack guide cap 25 to prevent oil pressure leakage in the cylinder chamber 26, and a certain amount of frictional force is always exerted between the steering pinion 21 and the steering rack 22. A spring 28 is also provided inside to hold the . The rack guide cap 25 is fixed by being screwed into the gear housing 24, and a hole for introducing the adjustment hydraulic pressure, that is, a hydraulic pressure introduction hole is bored in the center thereof, and the hydraulic pipe 10 is connected to the rack guide cap 25.

In the rack and pinion steering device of this embodiment having the above configuration, signals from the acceleration sensor 3 and the vehicle speed sensor 4 are used to drive the electromagnetic solenoid 11 of the oil pressure regulating valve section 6 according to the driving state of the vehicle. An electronic control circuit 5 is provided which outputs a drive signal according to the following. Next, this electronic control circuit 5 will be explained using FIG. 2.

As shown in the figure, the electronic control circuit 5 includes an acceleration circuit 31 as a first control signal generation means to which a signal from the acceleration sensor 3 is input, and a second control signal generation means to which a signal from the vehicle speed sensor 4 is input. Vehicle speed circuit 32, acceleration circuit 31 and vehicle speed circuit 32
It is comprised of a reference signal generation circuit 33 which adds signals from the 100 and outputs a reference signal for oil pressure adjustment, and a drive signal generation circuit 34 which outputs a drive signal to the electromagnetic solenoid 11 in accordance with the reference signal.
This drive signal generation circuit 34 is the reference signal generation circuit 3
3 constitutes a drive signal generating means.

The acceleration circuit 31 is a circuit that receives a signal from the acceleration sensor 3 and outputs a signal at a corresponding acceleration level. In other words, as shown in the figure, the acceleration sensor 3 includes a variable resistor VR1 whose resistance value changes when axial acceleration of the tie rod 2 occurs, a resistor R1,
A bridge is formed from R2 and R3, and tie rod 2 is connected by applying a DC voltage between terminals a and b.
Since a potential difference is generated between terminals c and d according to the axial acceleration of ) 41 and then output to the reference signal generating circuit 33. The acceleration signal e1 outputted from the acceleration circuit 31 is set to take a negative value in accordance with the axial acceleration V of the tie rod 2, as shown in FIG.

Next, the vehicle speed circuit 32 includes a vehicle speed detection circuit consisting of a diode 42, a transistor 43, resistors R8, R9, R10, and a capacitor C1, a frequency/voltage converter (hereinafter referred to as an F/V converter) 44, and a resistor.
A comparator consisting of R11, R12, R13 and an operational amplifier 45, and resistors R14, R15, R16, R17,
and a differential amplifier circuit consisting of an operational amplifier 46. Specifically, the vehicle speed sensor 4 is, for example, an electromagnetic pickup type sensor that generates a signal in response to the rotation of the propeller shaft, and a signal with a frequency corresponding to the signal from the vehicle speed sensor 4 is detected by the vehicle speed detection circuit. It will be done. And the detected frequency signal is F/V
It is converted into a voltage signal e2 by the converter 44, and compared with the voltage signal e3 divided by the resistors R11 and R12 by the comparator of the operational amplifier 45, and the voltage signal e4 is
is output. Thereafter, the voltage signal e2 converted by the F/V converter 44 and the voltage signal e4 output by the comparator of the operational amplifier 45 are combined into the operational amplifier 4.
The voltage signal e5 is compared in the differential amplifier circuit No. 6, and the voltage signal e5 is outputted to the next reference signal generation circuit 33. The voltage signals e2 and e3 are shown in FIG. 4a, the voltage signal e4 is shown in FIG. 4b, and the voltage signal e5 is shown in FIG. 4c. In the end, in this vehicle speed circuit 32, When the vehicle speed V determined according to the signal from the vehicle speed sensor 4 is not running at low speeds such as Va or less, a voltage signal e5 corresponding to the vehicle speed V is output to the reference signal generation circuit 33, and the vehicle speed is determined to be V. If it is larger than Va, hydraulic control can be performed according to the vehicle speed V.

The reference signal generation circuit 33 includes resistors R18, R19, R20,
It consists of a differential amplifier circuit consisting of R21 and an operational amplifier 47, and a Zener diode 48 grounded on its output side. In other words, the voltage signal e1 output from the acceleration circuit 31 and the vehicle speed circuit 32
However, since the voltage signal e1 representing the acceleration of the tie rod 2 is a negative value, the circuit of the operational amplifier 47 operates like an adder. will be done. The Zener diode 48 is provided to protect the reference signal output from the reference signal generation circuit 33 from becoming a reference signal greater than the maximum drive signal of the electromagnetic solenoid 11.

In this way, the reference signal generation circuit 33 outputs the reference signal e6 for oil pressure adjustment according to the acceleration V of the tie rod 2 and the running speed V of the vehicle.Next, this reference signal e6 is received. , the drive signal generation circuit 34 that outputs a drive signal to the electromagnetic solenoid 11 will be explained.

In this drive signal generation circuit 34, first, the difference between the reference signal e6 and the excitation signal e7 detected by the current detection circuit 35 is calculated by a differential amplifier circuit consisting of an operational amplifier 49 and a resistor R22, and then It is input to the comparator of the operational amplifier 50. The current detection circuit 35 is composed of resistors R23, R24, R25, R26, a capacitor C2, and an operational amplifier 51, and rectifies and amplifies a voltage signal corresponding to the excitation current of the electromagnetic solenoid 11 to obtain a predetermined value. The excitation signal e7 is detected. Further, the voltage signal corresponding to the excitation current refers to the potential difference generated across the resistor R27 when the grounding side terminal of the electromagnetic solenoid 11 is grounded via the resistor R27.

Next, the comparator consisting of the operational amplifier 50 is a circuit provided to perform duty control, and receives the difference signal e8 from the operational amplifier 49 and the triangular wave signal e9 output from the oscillator 36, and receives the difference signal e8. A control pulse signal e10 is output which is "H" when the value is larger than the triangular wave signal e9, and which is "L" when the difference signal e8 is less than or equal to the triangular wave signal e9. The oscillator 36 that outputs the triangular wave signal e9 is a circuit composed of resistors R28, R29, R30, R31, R32, a capacitor C3, and an operational amplifier 52, and is connected to the inverting input terminal of the operational amplifier via a resistor R33. This will output a triangular wave signal e9 with a stable frequency.

The control pulse signal e10 is applied to the resistor R34,
It is supplied to the base input of the transistor 53 via R35, and turns on the transistor 53 when the pulse control signal e10 is "H", and also turns on the transistor 54 connected to the collector of the transistor 53 via the resistor R36. , a desired duty-controlled drive signal to the electromagnetic solenoid 11 connected to the collector side of the transistor 54,
In other words, an excitation current is supplied. Note that the transistor 54 has a resistor R37 between its base and emitter.
However, the vehicle battery 55 was damaged in the emitter, and the collector
A diode 56 is connected between each ground, and power is supplied by a vehicle battery 55, and the back electromotive force of the electromagnetic solenoid 11 is absorbed by the diode 56.

As mentioned above, the electromagnetic solenoid 11 has a reference signal.
Difference signal e8 between e6 and excitation signal e7, and triangular wave signal e9
A drive signal corresponding to the pulse width of the control pulse signal e10 based on the above is outputted.Next, each of these signals is shown in FIG. 5 and briefly explained.
In the figure, a represents the input signal of the operational amplifier 49, which is the reference signal e6 outputted from the reference signal generation circuit 33 and the excitation signal e7 outputted from the excitation signal detection circuit 35. b represents the input signal of the operational amplifier 50, which includes the reference signal e6 obtained from the operational amplifier 49 and the excitation signal.
It shows a difference signal e8 with e7 and a triangular wave signal e9 output from the oscillator 36. And c represents the signal output from the operational amplifier 50,
"H" when the difference signal e8 is larger than the triangular wave signal e9,
This shows a control pulse signal e10 that is set to "L" when the difference signal e8 is less than or equal to the triangular wave signal e9. When the control pulse signal e10 is output in this way, d
A drive signal as shown in e is output from the transistor 54 to the electromagnetic solenoid 11, and an excitation current as shown in e flows through the electromagnetic solenoid 11.

In this way, in the steering device of this embodiment, the excitation current of the electromagnetic solenoid 11 is changed according to the vehicle running speed and the axial acceleration of the tie rod 2, and the spool valve 12 is accordingly opened and closed. Since the oil pressure in the cylinder chamber 26 is increased or decreased, the frictional force between the steering pinion 21 and the steering rack 22 is controlled to increase or decrease. Here, changes in the opening degree and oil pressure of the spool valve 12 corresponding to the vehicle speed V are as shown in FIG. 6, and when the vehicle speed V is, for example, 60 (Km/h)
At low speeds such as those below, the electromagnetic solenoid 11 is not driven, and when the vehicle speed V exceeds 60 (Km), the spool valve 12 is closed in accordance with the vehicle speed to increase the oil pressure. In addition, in the figure, when the vehicle speed V is 140 (Km) or more, the opening is constant and the oil pressure is constant; however, when the vehicle speed is 140 (Km) or more, the spool valve 12 is fully closed and the oil pressure remains the same. It shows that it is being controlled. Also, Figure 7 shows tie rod 2.
This shows that the opening degree and oil pressure of the spool valve 12 change depending on the magnitude of the axial acceleration V of the tie rod 2.As shown in the figure, the oil pressure is controlled only in response to the axial acceleration V of the tie rod 2. The vehicle speed is 60 (Km)
This is the case when the vehicle is running at a low speed as follows. It goes without saying that FIG. 6 shows the case where no axial acceleration of the tie rod 2 occurs, that is, when the vehicle is traveling straight.

In this embodiment, as shown in FIGS. 6 and 7, when the vehicle is running at a low speed of 60 km/h or less, the electromagnetic solenoid 11 is normally turned off.
Since the steering pinion 21 and the steering rack 22 are not driven and the oil pressure is not increased, the frictional force between the steering pinion 21 and the steering rack 22 does not increase, and therefore a light steering feeling is obtained. At the same time, when driving on a rough road, the axial acceleration V of the tie rod 2 increases due to the unevenness of the road surface, and the electromagnetic solenoid 11 is driven, the opening of the spool valve 12 becomes smaller, and the oil pressure increases, causing the steering pinion to increase. Since the frictional force between the steering rack 21 and the steering rack 22 increases, the occurrence of backlash can be suppressed. Similarly, when an impact force is transmitted from the tie rod 2 to the steering gear box 1 side, it is also possible to prevent hammering noise from being generated from the meshing portion between the steering rack 22 and the steering pinion 21, etc.

When the vehicle speed is more than 60 km/h and less than 140 km/h, the electromagnetic solenoid 11 is driven according to the magnitude of the vehicle speed V and the magnitude of the axial acceleration V of the tie rod 2. The frictional force of the steering pinion 21 and the steering rack 22 is increased or decreased by the hydraulic pressure according to the magnitude of the directional acceleration V, and the higher the speed, the more the steering response to sudden steering increases, improving the running stability and steering performance of the vehicle. can be improved.

In addition, when the vehicle speed is 140 km/h or more, the spool valve 12 is fully closed to maximize the frictional force between the steering pinion 21 and the steering rack 22 to ensure good running stability and steering performance of the vehicle. be able to.

Further, in this embodiment, in a high-speed driving state where the vehicle speed exceeds 60 km/h, the steering pinion 21 and the steering rack 2 are
Since the frictional force of No. 2 is increased, it is possible to prevent flutter that generally tends to occur during high-speed running.

In this embodiment, the original oil pressure adjusted by the oil pressure regulating valve section 6 is output from the hydraulic pump 8 driven by the transmission 7, but this is not the same as the oil pressure from the engine oil pump. In the case of a power steering vehicle, the hydraulic pressure from the return side of the power steering pump may be used.

[Brief explanation of the drawing]

FIG. 1 is a schematic system diagram showing one embodiment of the present invention, FIG. 2 is a circuit diagram of the electronic control circuit 5, FIG. 3 is a diagram showing the acceleration signal e1 output from the acceleration circuit 31, and FIG. 5 is a diagram showing the voltage signals e2, e3, e4, e5 of each part of the vehicle speed circuit 32, FIG. 5 is a time chart of the drive signal generation circuit 34, and FIG.
The figure is a diagram showing changes in the spool valve opening and oil pressure depending on the vehicle speed, and FIG. 7 is a diagram showing changes in the spool valve opening and oil pressure depending on the tie rod axial acceleration. DESCRIPTION OF SYMBOLS 1...Steering gear box, 2...Tie rod, 3...Acceleration sensor, 4...Vehicle speed sensor, 5...Electronic control circuit, 6...Hydraulic pressure adjustment valve section,
21... Steering pinion, 22... Steering rack, 23... Rack guide, 26...
cylinder chamber.

Claims (1)

[Scope of Claims] 1. A vehicle speed sensor that detects the body speed of the vehicle; an acceleration sensor that detects the axial acceleration of the tie rod; and a system that receives detection signals from the acceleration sensor and the vehicle speed sensor and drives the oil pressure adjustment valve described below. an electronic control circuit that outputs a signal; a hydraulic pressure adjustment valve that adjusts the hydraulic pressure generated by the hydraulic pump according to a drive signal from the electronic control circuit; and a steering control circuit that adjusts the hydraulic pressure adjusted by the hydraulic pressure adjustment valve. a steering gear box provided with a rack guide that presses the rack and increases or decreases the frictional force between the steering rack and the steering pinion, and the electronic control circuit is configured to: based on a detection signal from the acceleration sensor,
a first control signal generating means for outputting a first control signal for increasing the frictional force between the steering rack and the steering pinion in response to an increase in the axial acceleration of the tie rod; and a first control signal generating means based on a detection signal from the vehicle speed sensor. a second control signal generating means for outputting a second control signal for increasing the frictional force between the steering rack and the steering pinion in accordance with an increase in the vehicle speed only when the vehicle speed exceeds a predetermined value; and a drive signal for driving the oil pressure regulating valve in response to a signal obtained by adding a second control signal from the second control signal generating means and a first control signal from the first control signal generating means. A rack and pinion steering device comprising: drive signal generating means for generating and outputting a drive signal;