JPS60135367A - Power steering device - Google Patents

Abstract

PURPOSE:To secure stability in a feeling of steerage in time of medium- and high-speed driving as well as to eliminate any danger due to oversteering in the wheel, by reducing a rate of flow supplied to a driving part in a medium- and high-speed range and thereby making a proportional steering characteristic securable. CONSTITUTION:A flow control valve F is installed in position between a pump P and a driving part (a). This driving part (a) consists of a control valve 1 and a power cylinder 2 as the main elements. The control valve 1 is selected to where it should be according to operation of a steering wheel H, while the power cylinder 2 operates according to the selecting direction of the control valve 1 and specifies the steering direction of a car. The flow control valve F installed between the pump P and the driving part (a) specifies the control flow according to a current-carrying value to a proportional solenoid 3 but the current-carrying value is controlled by a control signal out of a controller C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to a power steering device that provides a stable steering feel during medium-to-high speed driving, prevents excessive turning of the steering wheel, and improves running stability.

Conventionally known devices of this type control the flow rate or pressure supplied to the power cylinder so that a predetermined steering output is obtained depending on the speed of the vehicle.

In the case of a vehicle equipped with a power steering device, it generally has a power steering performance characteristic curve as shown in Figure 1 (a).In other words, when the vehicle is running at low speed, the road resistance experienced by the wheels is large, so steering by the power cylinder is required. In order to obtain sufficient assist force and allow the driver to operate the steering wheel lightly, the steering input (handle steering torque) as shown by xo in the figure obtained under the maximum supply flow rate Qmax is required.
and output (wheel steering output torque) curve.

In addition, when driving at high speeds, the road resistance is small, so the steering assist effect is weakened, and the supply flow rate is restricted so that the steering wheel operation becomes heavier and the steering wheel is not turned too much. The characteristics indicated by X and x2 are maintained.

Note that the curve Xms in the figure is the manual steering characteristic obtained when the supply flow rate is zero; X2, Xm5(1) + t
The characteristics of tF drift can be obtained by changing the flow rate of pressure oil supplied to the power cylinder from Qmax to Qmin.

In the case of the conventional device, the steering characteristics are uniformly determined depending only on the vehicle speed so that the steering outputs determined respectively corresponding to the predetermined speed ranges can be obtained as described above. For this reason, changing lanes while driving at high speed,
Even when cornering, some parts of the steering characteristics do not change, and the steering performance characteristics become a so-called parabolic curve, so the ratio of change in steering output to changes in steering input becomes large, creating a drawback that is dangerous. .

For example, if you turn the steering wheel at high speeds in the same way as at low speeds, the vehicle will bend too much, and for inexperienced drivers who do not have an intuitive sense of this point, steering at high speeds may be dangerous. There was a problem with this.

This invention controls the supply flow rate according to the steering angle even in the same speed range, so that the steering performance characteristics, especially in the medium and high speed range, can be obtained as a characteristic with a proportional relationship in the form of a -th curve. The purpose is to provide a device that improves running stability.

The illustrated embodiment will be described below.

Figure 1 (b) is a steering performance characteristic diagram obtained by the device of this invention, and Figure 2 is the first diagram for realizing it.
FIG. 3 is a circuit diagram of the embodiment, and a block diagram thereof. As is clear from these figures, the first embodiment has a flow control valve between the pump P and the drive section a. F is provided.

Note that the drive section a is of a known type, and consists of a control valve 1 and a power cylinder 2 as main elements. Then, in accordance with the operation of the handle H, the control valve 1 is switched, and in accordance with the switching direction of the control valve l,
The power cylinder 2 operates to specify the steering direction of the vehicle.

As described above, the quantity control valve F provided between the pump P and the drive unit a specifies the controlled flow rate according to the amount of electricity supplied to the proportional solenoid 3, but the flow rate is determined by the flow rate from the controller C. Controlled by control signals.

As shown in FIG. 4, this controller C has an interface 7 connected to a speed sensor 4 provided on the crankshaft or drive shaft of the engine E and a steering angle sensor 6 provided on the shaft 5 of the handle H. ing. Then, this interface 7 is connected to a calculation section 8, and a storage section 9 is connected to this calculation section 8, and in accordance with the input signal from the interface 7, comparison calculations are performed according to the program in this storage section 9. The calculation results are output.

The output signal from the arithmetic unit 8 thus constructed is transmitted to the proportional solenoid 3 via the interface 16 and the amplifier 17, so the flow control valve F operates according to this signal and controls the controlled flow rate. Identify.

The control characteristics of this flow rate control valve F are determined as follows.

That is, as shown in FIG. 5, when the signal of the speed Vo at which the vehicle is stopped, such as when the vehicle is parked in a garage and turned off, the power cylinder 2 is turned off regardless of the steering angle of the steering wheel H. As shown by straight line 10, the maximum flow rate Qmax
As a result, the characteristic curve x in the steering performance characteristic diagram of FIG.
.

Like, maintain full power state.

In addition, when a very low speed Vl signal of about 20) on/h is input, for example while the vessel is slowing down, a moderate flow rate, which is slightly lower than that at the time of stopping, is supplied regardless of the steering angle, and as a result, the As shown by the characteristic curve x1 in the steering performance characteristic diagram of FIG.

At medium to high speeds, the larger the steering angle θ becomes, in other words, the more the /\ steering wheel is turned, the smaller the controlled flow rate Q becomes. for example,
When the speed ■2 signal is input, the steering angle θ at that time is
is detected, and according to this steering angle θ, the control flow rate Q is
Control is performed as shown by straight line 12 in FIG. In other words, the larger the steering angle θ becomes, the more the control flow rate is reduced.

Also, at speed ■3 faster than speed v2, as shown by straight line 13, the steering angle θ is lower than that at speed v2.
The rate at which the control flow rate decreases when the flow rate increases is increased. Furthermore, in the case of speed 4 which is higher than speed v3, the above-mentioned reduction rate is further increased as shown by straight line 14.

That is, in the device of this invention, vehicle speed V and steering angle θ
The control flow rate is determined by Accordingly, the control flow rate Q is controlled by the controller C at medium and high speeds so that it becomes smaller.

As a result of the flow rate control depending on the steering angle, the first
For example, the characteristic curves x'2, x'3, x' in figure (b)
As shown in 4, a linear proportional output characteristic can be obtained6.Therefore,
To explain this proportional output characteristic in more detail based on Fig. 6, Fig. 6 shows the relationship between the steering input and output at each flow rate when the flow rate supplied to the power cylinder is varied from Q0 to Qn. This is a graph showing the relationship, and shows that if the flow rate is large, a large power assist output will be generated even with a small steering force, and if the flow rate is small, the power assist output will be small with respect to the steering force. However, for convenience of explanation, the number of flow rate changes is illustrated as n=8, and the flow rate is Qo))Qe.

Thus, when the vehicle speed is above 2, the control flow rate is assigned on the straight line 12 in FIG. 5 in accordance with the steering angle 0 at that time. That is, if the steering angle is set to 01 to θ8 for convenience, then from FIG. 5, the steering angle used when the vehicle speed is V2 is 01.
Since the required control flow rate corresponding to ~θ8 can be determined based on the straight line 12, the flow rate supplied to the power cylinder is adjusted to the steering angle 01~θ so that the required control flow rate is linearly decreased.
As a result, 61 to 88 points corresponding to the used steering angles 01 to θ8 are specified based on each steering performance characteristic curve in FIG. 6, and a set of these points is The linear steering performance characteristic curve x'2 shown in Figure 1 (b)
obtained as.

Further, at a speed v3 faster than the speed V2, based on the flow rate characteristic of the straight line 13 in FIG. 5 corresponding to the speed V3, as shown in the characteristic curve x'3 in FIG. The relationship between steering input and output is obtained. In other words,
5th r! ! Since the reduced required control flow rate is allocated according to the steering angle θl to θ6 at the time of speed v3 according to the straight line 3 of J, the supply flow rate to the power cylinder is adjusted so that the required control flow rate is achieved. , if selection control is performed in accordance with the steering angles θ1 to θ6 used, as a result,
Based on each steering performance characteristic curve in Figure 6, the steering angle used is 01.
Points a/1 to a/6 corresponding to ~θ6 are specified. A set of these points a/l-a/6 is obtained as a linear steering performance characteristic curve X'3 as shown in FIG. 1(b). At this time, as is clear from FIG. 6, if the vehicle speed is different, for the same steering angle condition, for example, steering angle θ6, at vehicle speeds of 72 o'clock and 73 o'clock, 86 points correspond to points a and 3, respectively. Therefore, when the vehicle speed is 72, 86 points are specified by the steering performance characteristic curve based on the flow rate Q6.

Further, the control flow conditions are different, such that when the vehicle speed is 73, point a'6 is specified by the steering performance characteristic curve based on the flow rate Q7.

Furthermore, even at a speed v4 faster than the speed v3, the steering angle used at that time is 01 to
The required control flow rate corresponding to θ4 is assigned, and the flow rate shown in Fig. 1 (
A linear proportional steering performance characteristic curve such as the characteristic curve x'4 in b) is obtained.

That is, when the speed is relatively low, for example, when the speed is v2, the steering angle range used is a relatively large angle range 〇X to θ8. On the other hand, at speeds v3 or V4, which are higher than the above-mentioned speed V2, when the steering wheel is turned, the centrifugal force acting on the vehicle increases, and there is a risk of overturning or skidding. The scope will be limited. In other words, there is no need to turn the steering wheel extremely far, and the usable steering angle range is limited to 01 to θ6 or 01 to θ4.

Therefore, in this embodiment, the output of the power cylinder 2 is reduced depending on the vehicle speed and steering angle in order to prevent the output of the power cylinder 2 from increasing rapidly and causing excessive turning in the medium to high speed range. The system controls the flow rate to obtain proportional steering output characteristics. Therefore, the operating force of the steering wheel does not become too light, and a stable steering feeling can be obtained.

Furthermore, when the vehicle speed V5 exceeds 180 km/h, the speed of the f55 diagram is correct! As shown at 115, the supply of pressure oil to the power cylinder 2 is set to zero regardless of the steering angle, resulting in a manual steering state shown by the curve Xms in FIG. 1(b).

As described above, in the storage unit 9 of the controller C, the flow characteristics 10 to 15 shown in FIG. Since each characteristic is selected based on the actually detected values of vehicle speed and steering angle, the steering performance characteristics shown in Figure 1 (b) are obtained as a result of flow control based on the calculation results. can get.

Next, in the second embodiment shown in FIG. 7, the flow control valve F
Instead, a short-circuit valve S is provided, and the chambers on both sides of the power cylinder 2 are communicated via the short-circuit valve S. Therefore, depending on the opening degree of this short-circuit valve S, the power cylinder 2
The flow rate from the supply side chamber to the return side chamber is adjusted, which is substantially the same as adjusting the supply flow rate to the power cylinder 2.

The opening degree of the short-circuit valve S is determined by the amount of current supplied to the proportional solenoid per day, and the amount of current supplied is determined by the vehicle speed and steering angle of the vehicle, as in the first embodiment. That is, in this second embodiment, a short circuit valve S is provided in place of the flow rate control valve F, and the other configurations are the same as the first embodiment.

(Structure of the present invention) The structure of the present invention includes a pump and a drive section consisting of a control pulp, a power cylinder, etc., and controls the flow rate supplied to the drive section according to the vehicle speed to adjust the output to the steering force. A power steering device that controls the relationship between a speed sensor that detects the speed of the vehicle, a steering angle sensor that detects the steering angle of the steering wheel, and a proportional solenoid that supplies electricity to the drive unit according to the amount of electricity supplied to the proportional solenoid. The controller includes a flow rate control mechanism that controls the flow rate, and a controller that receives output signals from both of the sensors and outputs a signal that controls the amount of current applied to the proportional solenoid, and the storage section of the controller stores at least information about the vehicle. The variable rate of the flow rate at relatively low speeds in the medium and high speed range is reduced in accordance with the steering angle used at the slow speeds, and the rate of change in the flow rate at relatively high speeds is adjusted to correspond to the steering angle used at the relatively high speeds. The controlled flow rate characteristic is memorized to reduce the flow rate at a larger rate than at the slow speed, and the flow rate control is made dependent on the vehicle speed and steering angle of the flow rate control mechanism, so as to obtain proportional steering performance characteristics in the medium and high speed range. It is characterized by the following points.

Note that the flow rate control mechanism in the above configuration refers to the first
This corresponds to the flow control valve F in the embodiment and the short circuit valve S in the second embodiment.

(Effects of the present invention) The present invention reduces the flow rate supplied to the drive unit depending on the vehicle speed and steering angle, at least in the medium and high speed range, and obtains proportional steering performance characteristics. This provides a stable steering feel at high speeds, eliminates the danger of turning the steering wheel too much, and improves safety.

[Brief explanation of drawings]

Figure 1 (a) is a steering performance characteristic diagram showing the relationship between steering input and steering output in a conventional power steering device, Figure 1 (b) is a steering performance characteristic diagram of the present invention, and Figures 2 to 2 are diagrams showing the steering performance characteristics of the present invention. Figure 6 shows the first embodiment of the invention, Figure 2 is a circuit diagram, Figure 3 is a block diagram of Figure 2,
Fig. 4 is a block diagram of the electronic control circuit, Fig. 5 is a characteristic diagram showing the relationship between steering angle and control flow rate, and Fig. 6 is a graph of steering input and output at speeds v2, v3, and v4 in the medium and high speed range. The relationship is shown in a graph, and FIG. 7 is a block diagram of the hydraulic circuit of the second embodiment. P... Pump, a... Drive unit, F, S... Flow rate control valve, short circuit valve that constitutes the flow rate control mechanism, 3... Proportional valve, C... Controller, 4... Speed Sensor, 6... Steering angle sensor. Agent Patent Attorney Nobuyuki Shima 1 Figure (A Back 1 Figure (B) 7 or ij Co-rudder input '?' % +3 Figure V Back 4 Figure Control 6 Figure Y 7 Figure

Claims (1)

[Claims] A power steering device that includes a pump, a drive section including a control valve, a power cylinder, etc., and controls the flow rate supplied to the drive section according to vehicle speed to control the relationship between output and steering force, a speed sensor that detects the speed of the said type, a steering angle sensor that detects the steering angle of the steering wheel, and a flow rate control mechanism that controls the flow rate supplied to the drive unit according to the amount of energization to the proportional solenoid. A controller receives output signals from both sensors and outputs a signal for controlling the amount of current applied to the proportional solenoid, and the controller has a memory section containing information at least at relatively low speeds in medium and high speed ranges of the vehicle. The variable rate of the flow rate is decreased in response to the steering angle used at the slow speed, and the rate of change in the flow rate at the relatively fast speed is reduced at a larger rate in response to the steering angle used at the slow speed. A power steering device that stores a control flow characteristic to be reduced and controls the flow rate depending on the vehicle speed and steering angle of the flow control mechanism to obtain proportional steering performance characteristics in a medium to high speed range.