JPH03204376A - Four wheel steering gear - Google Patents

Abstract

PURPOSE:To suitably steer rear wheels according to a running state by providing a control means which controls the steering of the rear wheels on a steering angle of front wheels so that a steering angle of the rear wheels may coincide with a target steering angle computed on the number of engine revolutions of an internal combustion engine and a gear engaging state of a transmission gear. CONSTITUTION:A control section 40 establishes the steering characteristics of a steering angle of a rear wheel to that of a front wheel toward the number of engine revolutions on engaging states of gears at each speed range and of reverse gears of a transmission gear, and the above characteristics are stored in a characteristic memory section 50. A characteristic selecting section 52 selects the steering characteristics stored in the memory section 50 on a detecting signal issued from a sensor 48 for reading out it, and inputs it into a target steering angle computing section 54, which computes a target steering angle of the rear wheels on the detecting signals issued from sensors 42, 44, 46 and a signal of the steering characteristics inputted from the selecting section 52. A pulse generator 52 generates a pulse according to the computed target steering angle, and inputs it into a driver 58 to drive an electric motor 36 so that the steering angle of the rear wheels may coincide with the target steering angle.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a four-wheel steering system, and in particular, to a four-wheel steering system that appropriately controls the rear wheels according to the driving condition without giving the driver a sense of discomfort regarding the behavior of the vehicle in response to steering operation. The present invention relates to a four-wheel steering device that can be steered.

[Conventional technology]

BACKGROUND ART Vehicles such as automobiles usually have front wheels that are steerable in a desired direction of travel of the vehicle, and rear wheels that are provided parallel to the longitudinal direction of the vehicle body.

When the front wheels of such a vehicle are steered to turn, the traveling trajectories of the front and rear wheels do not match the turning circle, and at low vehicle speeds, the rear wheels enter the inside of the turning circle due to the difference between the inner wheels. When turning and at high vehicle speeds, centrifugal force causes the vehicle to turn with the front wheels inside the turning circle.

Therefore, even if the front wheels are steered in the turning direction, which is the traveling direction of the vehicle, there is a problem in that the attitude of the vehicle cannot be made to match the turning direction.

Therefore, a vehicle has been proposed in which the rear wheels are also steered when the front wheels are steered. Some vehicles that steer the rear wheels in this manner employ a four-wheel steering device that performs steering control so that the rear wheel steering angle becomes the rear wheel target steering angle when the front wheels are steered.

As such a four-wheel steering device, for example, Japanese Patent Application Laid-Open No. 64
This method is disclosed in Japanese Patent Application Laid-open No. 16470, Japanese Patent Application Laid-Open No. 62-247980, and the like. The system disclosed in Japanese Unexamined Patent Publication No. 6416470 performs steering control so that the steering angle of the rear wheels becomes a target steering angle based on the vehicle speed. Also, JP-A-62
What is disclosed in Publication No. 247980 is capable of manually or automatically switching the steering characteristic when controlling the steering so that the steering angle of the rear wheels becomes the target steering angle based on the vehicle speed, depending on the driving conditions. .

That is, conventionally, the steering angle of the rear wheels is controlled based on the vehicle speed as shown in FIG. 4 so that it becomes the target steering angle, and the steering angle of the rear wheels is controlled based on the vehicle speed as shown in FIG. Some vehicles are capable of switching the steering characteristics when controlling the steering so that the angle becomes the target steering angle depending on the driving conditions, for example, between normal driving and sports driving. Furthermore, there is also a vehicle that performs steering control based only on the steering angle of the front wheels so that the steering angle of the rear wheels becomes a target steering angle.

[Problem that the invention seeks to solve]

However, a four-wheel steering system that controls steering so that the rear wheel steering angle becomes a target steering angle based only on the front wheel steering angle does not provide information to the driver regarding the behavior of the vehicle in response to steering operations when driving in reverse or at high speed. There is an inconvenience that makes you feel uncomfortable. Furthermore, as shown in FIG. 4, a four-wheel steering system that performs steering control so that the steering angle of the rear wheels becomes a target steering angle based on the vehicle speed can improve the running stability of the vehicle in high-speed running conditions. , there is a disadvantage that the turning performance of the vehicle is reduced in sports driving conditions. moreover,
As shown in Fig. 5, in a four-wheel steering system that can switch the steering characteristics when performing steering control so that the steering angle of the rear wheels becomes the target steering angle based on the vehicle speed, the steering angle of the rear wheels is Reverse phase (
There are some systems that use a changeover switch to change the vehicle speed when changing from low speed) to in-phase (high speed), but in practice the switching operation is cumbersome, and moreover, the rear wheels are steered based on the vehicle speed. , there is a disadvantage that the rear wheels cannot be appropriately steered depending on the driving condition.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to realize a four-wheel steering system that can appropriately steer rear wheels according to driving conditions without giving a driver a sense of discomfort regarding the behavior of a vehicle in response to steering operations.

[Means for solving problems]

In order to achieve this object, the present invention provides steering so that the steering angle of the rear wheels becomes a target steering angle calculated based on the steering angle of the front wheels based on the engine speed of the internal combustion engine and the gear engagement state of the transmission. It is characterized by providing a control means for controlling.

[Effect]

According to the configuration of the present invention, the control means steers the rear wheels based on the steering angle of the front wheels so that the steering angle becomes the target steering angle calculated based on the engine speed of the internal combustion engine and the gear engagement state of the transmission. By controlling the rear wheels, it is possible to obtain rear wheel steering characteristics according to the driving condition without requiring any special switching operation.

〔Example〕

Next, embodiments of the present invention will be described in detail based on the drawings.

1 to 3 show embodiments of this invention. In Fig. 1, 2 is a vehicle, 4 is a steering wheel,
6 is a steering shaft, 8 is a front wheel steering mechanism which is a front wheel steering means, 10 is a front wheel, 12 is a rear wheel steering mechanism which is a rear wheel steering means, and 14 is a rear wheel.

This vehicle 2 uses a front wheel steering mechanism 8 to steer front wheels 10 and 10 , and a rear wheel steering mechanism 12 to steer rear wheels 14 and 10 .
14 as well.

The front wheel steering mechanism 8 is provided with a front pinion 16 provided at the tip end of the steering shaft 6 in mesh with a front rack 20 provided on a front rack bar 18, and both ends of the front rack bar 18 are connected to front tie rods. 22, 22 and the front wheels 10, 1 via the front knuckle arms 24, 24.
It is set up by contacting 0.

The rear wheel steering mechanism 12 is provided with a rear binion 26 meshing with a rear rack 30 provided on a rear rack bar 28,
Both ends of this rear rack bar 28 are connected to rear control rods 32, 32 and rear knuckle arms 34, 34, respectively.
The rear wheels 14 are connected to the rear wheels 14 via.

Further, the rear pinion 26 of this rear wheel steering mechanism 12 is driven by an electric motor 36. This electric motor 36 is provided in communication with the rear side binion 26 of the rear wheel steering mechanism 12 via a driving force reduction mechanism 38.

The electric motor [36 is, for example, configured to be driven by pulses, and is connected to a control section 40 serving as a control means.

The control unit 40 includes a front wheel steering angle sensor 42 provided in the front wheel steering mechanism 12 to detect the rotation amount of the steering shaft 6 due to the operation of the steering wheel 6 as the steering angle of the front wheels 10, and a front wheel steering angle sensor 42 that drives the electric motor 36. A rear wheel steering angle sensor 44 is provided in the rear wheel steering mechanism 12 to detect the amount of rotation of the rear pinion 26 by the rear wheel as a steering angle of the rear wheels 14, and an internal combustion engine (not shown) mounted on the vehicle 2 ) detects the gear engagement state of a transmission (not shown) that converts the driving force of the internal combustion engine into a desired gear engagement state of a transmission gear train. A gear engagement state sensor 48 is connected thereto.

This control section 40, as shown in FIG.
a memory selection section 52 that selects and reads out the steering characteristics stored in the characteristic storage section 50 based on a detection signal input from the gear engagement state sensor 48; Sensor 42/Rear wheel steering angle sensor 44
- A target steering angle calculation unit 54 that calculates a target steering angle of the rear wheels 14, 14 based on a detection signal input from the engine rotation speed sensor and a signal of the selected steering characteristic input from the characteristic selection unit 52; It has a pulse generator 56 that generates pulses according to the target steering angle calculated by the steering angle calculation section 54, and a driver 58 that drives the electric motor 36 with the pulses from the pulse generator 56.

Is this a rule? &11 section 40 includes the various sensors 42
A detection signal is input from 48 to 48, and based on the steering angle of the front wheels 10, 10, the steering angle of the rear wheels 14, 14 is set to the target steering angle calculated based on the engine speed of the internal combustion engine and the gear engagement state of the transmission. This is to control the steering so that the

Next, the action will be explained.

Even if the vehicle speed is the same, the engine rotational speed and gear engagement state of the vehicle 2 differ depending on various driving conditions such as a normal driving condition, a sports driving condition, and a reverse driving condition. For example, the engine speed is high in a sport driving state for the same vehicle speed, and low in a normal driving state, a high speed driving state, and a reverse driving state for the same vehicle speed. In addition, the gear engagement state is a low-speed gear engagement state (engine speed: high rotation) in sport driving conditions for the same vehicle speed, while in normal driving conditions and high-speed driving conditions for the same vehicle speed. The high-speed gear is engaged (engine speed: low), and the reverse gear is engaged when the vehicle is running backwards at the same vehicle speed.

Therefore, detection signals from various sensors 42 to 48 are input to the control unit 40, and the wheels 1
The steering control is performed so that the steering angle of 4.14 becomes the target steering angle calculated based on the engine speed and the gear engagement state. For example, in the case of a transmission equipped with a five-speed gear train, the control unit 44 controls the first gear engagement state (1) as shown in FIG.
~5th gear engagement (V) and reverse gear engagement platform G (R
), the steering characteristics of the steering angles of the rear wheels 14, 14 relative to the steering angles of the front wheels 10, 10 are set and stored in the characteristics storage section 50.

The characteristic selection unit 52 selects and reads out the steering characteristic stored in the characteristic storage unit 50 based on the detection signal input from the gear engagement state sensor 48, and inputs the selected steering characteristic to the target steering angle calculation unit 54 of the next stage.

The target steering angle calculating section 54 uses the detection signals input from the front wheel steering angle sensor 42, the rear wheel steering angle sensor 44, and the engine rotation speed sensor 46 and the signal of the selected steering characteristic input from the characteristic selecting section 52 to calculate the rear steering angle. The target steering angles of the wheels 14 and 14 are calculated.

The pulse generator 50 generates a pulse corresponding to the calculated target steering angle and inputs it to the driver 58, and the driver 58 controls the electric motor so that the steering angle of the rear wheels 14 becomes the calculated target steering angle. 36.

In this way, the target steering angle is calculated based on the engine speed and the gear engagement state, and the steering is controlled so that the steering angles of the rear wheels 14, 14 become the target steering angle using the steering characteristics as shown in FIG. 3, for example. This allows stable driving in normal driving conditions and brisk driving in sports driving conditions without requiring any special switching operations, and in reverse driving conditions, the front wheels 10 and 14 do not steer the rear wheels 14 and 14.
0-only two-wheel steering allows worry-free driving, and steering characteristics of the rear wheels 14 can be obtained in accordance with the driving condition.

Therefore, the rear wheels 14 can be appropriately steered according to the driving condition without giving the driver a sense of discomfort regarding the behavior of the vehicle 2 in response to the steering operation.

The transmission may be manual or automatic as long as it has a configuration that converts the drive of the internal combustion engine depending on the gear engagement state of the transmission gear train.

〔Effect of the invention〕

As described above, according to the present invention, the control means causes the steering angle of the rear wheels to become the target steering angle calculated based on the engine speed of the internal combustion engine and the gear engagement state of the transmission based on the steering angle of the front wheels. By controlling the steering in this manner, it is possible to obtain rear wheel steering characteristics according to the driving condition without requiring special switching operations or the like.

Therefore, the rear wheels can be appropriately steered according to the driving condition without giving the driver a sense of discomfort regarding the behavior of the vehicle in response to the steering operation.

[Brief explanation of drawings]

1 to 3 show embodiments of the present invention, FIG. 1 is a schematic plan view of a vehicle equipped with a four-wheel steering system, FIG. 2 is a block diagram of the control unit, and FIG. 3 is a diagram showing the engine speed and gear It is a figure which shows the steering characteristic of a rear wheel by an engagement state. Figures 4 and 5 show conventional examples, Figure 4 is a diagram showing rear wheel steering characteristics based on vehicle speed, and Figure 5 is a diagram showing rear wheel steering characteristics that are switched based on vehicle speed depending on the driving condition. It is. In the figure, 2 is the vehicle, 4 is the steering wheel, and 8 is the vehicle.
1 is a front wheel steering mechanism as a front wheel steering means, 1° is a front wheel, 12 is a rear wheel steering mechanism as a rear wheel steering means, 14 is a rear wheel, 36 is an electric motor, 38 is a driving force transmission mechanism, 40 is a control unit, 42 is a front wheel steering Angle sensor, 44 is a rear wheel steering angle sensor, 46 is an engine rotation speed sensor, 1 2 48 is a gear engagement state sensor, 50 is a characteristic storage section, 52 is a memory selection section, 54 is a target steering angle calculation section, 56 is an The pulse generator 58 is a driver.

Claims (1)

[Claims] 1. A control means is provided for controlling the steering so that the steering angle of the rear wheels is a target steering angle calculated based on the steering angle of the front wheels based on the engine speed of the internal combustion engine and the gear engagement state of the transmission. Characteristic rear wheel steering method.