JPS61135863A - Steering characteristic controller for power steering device - Google Patents

Abstract

PURPOSE:To prevent abrupt change of assisted steering force even when wheels are bonding, by generating periodic additional signal, by compounding this signal with loading weight signal, and by changing conversion coefficient for vehicle speed versus control electric current stepwise depending on the compound signal. CONSTITUTION:The output of a vehicle speed sensor 31 is supplied to a FV converter 40, and the output of a loading weight sensor 32 is supplied to a DA converter 50. The loading weight data, which are converted to analog voltage by the DA converter 50, are supplied to a signal compound circuit 52 and a level adjusting circuit 43 through a filter circuit 51. The signal compound circuit 52 compounds sawtooth wave, which is output from a sawtooth wave generating circuit 48 composing additional signal generating means, and signal which is output from the filter circuit 51, and supplies the compound signal to a resistance select circuit 41. The assisted steering force is controlled by the compound signal from the signal compound circuit 52.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides an actuator for changing steering characteristics provided in a power steering device based on both the output of a vehicle speed sensor and the output of a loaded weight sensor. The present invention relates to a steering characteristic control device for a power steering device that changes the supplied current.

<Prior art> In a power steering device that not only reduces the assist force by the power steering device as the vehicle speed increases (but also reduces the assist force when the loaded weight is large),
As shown in FIG. 7, a pulse signal S having a frequency corresponding to the vehicle speed outputted from the vehicle speed sensor 1 is converted into a voltage signal by the FV converter 2, and this is supplied to the actuator drive circuit 5. Load weight sensor 3
The conversion coefficient of the FV converter 2 is changed in stages according to the magnitude of the output signal.

<Problems to be solved by the invention> However, in such a device, when the output of the loaded weight sensor 3 suddenly changes due to the wheels bouncing while driving on a rough road, the FV converter changes accordingly. The conversion coefficient No. 2 also changes rapidly, and as a result, the command signal supplied to the actuator drive circuit 5 also changes rapidly, resulting in a sudden change in the assist force by the power steering device.

For this reason, in such a conventional vehicle, the assist force provided by the power steering device changes rapidly each time the wheels rebound, resulting in a problem that the steering feeling deteriorates.

Means for Solving the Problems> The present invention derives a target current value according to the vehicle speed detected by a vehicle speed sensor, and makes it possible to change the conversion coefficient of the target current value for the vehicle speed in steps according to an external command. a current value deriving means; an additional signal generating means for generating an additional signal whose signal magnitude changes at a constant cycle; a signal synthesizing means for combining the output of the additional signal generating means with the output of the loaded weight sensor; conversion coefficient changing means for changing the conversion coefficient of the current value deriving means in stages according to the magnitude of the output of the signal synthesizing means; and a drive for driving the actuator according to the target current value derived by the current deriving means. The invention is characterized in that it is provided with means.

The signal output from the loaded weight sensor is combined with an additional signal whose signal period is shorter than the change period of the output signal of the loaded weight sensor caused by tire bounce, and the signal level of this combined additional signal is Since the conversion coefficient is switched in stages depending on the size, even if the output of the loaded weight sensor changes beyond the threshold for changing the conversion coefficient due to wheel bounce, the output of the combined signal will be As shown in Section 6(c), depending on the period of the additional signal, the potential exceeds or falls below the threshold value of 2■.
It spins around. As a result, the target current deriving means
As shown in Figures (d) and (e), the conversion coefficient before the bounce and the conversion coefficient after the bounce operate alternately, and as a result, the actual conversion coefficient of the current value deriving means is the average value of both, and the conversion coefficient is smooth. Convert to Therefore, the output of the current value deriving means changes smoothly, and it is possible to prevent the assist force from changing suddenly.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, a steering handle 10 is attached to one end of the handle shaft 1), and a steering shaft 13 of a power steering device 12 is connected to the other end of the handle shaft 1). The power steering device 12 consists of a servo valve 14 controlled by manual steering torque transmitted to the steering shaft 13, and a power cylinder 15 to which pressure fluid is distributed under the control of the servo pulp 14. The steered torque is transmitted to the steered wheels via the steering linkage of the circuit. A pump 16 is connected to the servo valve 14 of the power steering device 12, and pressure fluid is supplied to the servo pulp 14 by driving the pump 16 with an engine.

Reference numeral 20 denotes a solenoid valve that bypass-controls both end chambers of the power cylinder 15 in accordance with vehicle speed, etc. The mechanism of this solenoid valve 20 is shown in FIG. An attractive force acts on the spool 23 according to the current value applied to the solenoid 28, and when the spool 23 is displaced upward against the spring 25, both the passages 26
．． 27 are communicated with each other via the bypass slit 24, and the steering force is changed according to the amount of displacement of the spool 23, that is, the current value applied to the solenoid 28.

Further, 30 changes the current flowing through the solenoid 28 of the electromagnetic valve 20 depending on the magnitude of the vehicle speed detected by the vehicle speed sensor 31 and the loaded weight detected by the loaded weight sensor 32, thereby generating an assist force by the power cylinder 15. This is a steering characteristic control device that changes the steering characteristics according to both vehicle speed and loaded weight. In addition, the loading weight sensor 3
2 is a direct-acting displacement detector that detects a change in the position of the axle 34 relative to the chassis 33, and outputs data representing the loaded weight in binary code.

Further, as the vehicle speed sensor 31, a pulse generator is used that outputs pulses with a frequency proportional to the magnitude of the vehicle speed.

FIG. 3 is a block diagram showing the configuration of the steering characteristic control device 30, and the output of the vehicle speed sensor +31 is 1. The pulse output from the vehicle speed sensor 31 is supplied to an FV converter 40 that converts the pulse into a voltage proportional to its frequency, and the output of the loaded weight sensor 32 is supplied to a DA converter 50. The data of the loaded weight W converted into an analog voltage by the DA converter 50 is then transferred to the smoothing circuit 51.
The signal is supplied to the signal synthesis circuit 52 and the level adjustment circuit 43 via.

Table 1 Note that the digital output of the loaded weight sensor 32 changes between 0 and 3 depending on the loaded weight, as shown in Table 1.
Correspondingly, the output of the smoothing circuit 51 changes between 3V and OV.

The signal synthesis circuit 52 generates a sawtooth wave output from a sawtooth wave generation circuit 48 constituting additional signal generation means;
It combines the signal output from the smoothing circuit 51,
This combined signal is supplied to the resistance selection circuit 41. The period of the sawtooth wave output from the sawtooth wave generation circuit 48 is set to be sufficiently shorter than the period of output fluctuation of the loaded weight sensor 32 due to wheel bounce, and the amplitude of the signal is From a fraction to a fraction of the maximum value of the output signal
The signals output from the sawtooth wave generating circuit 48 are suitably attenuated and synthesized so that the following is achieved.

Therefore, the signal output from the signal combining circuit 52 is the sixth
As shown in Figures (a) to (C), the output a of the loaded weight sensor 32 changes rapidly due to the bounding of the wheels.
In addition to this, if the output signal of the smoothing circuit 51 changes, the output C of the signal synthesis circuit 52 will fluctuate in a long period with the fluctuation of the output signal of the smoothing circuit 51, and It fluctuates in a short period according to the period of the sawtooth wave supplied from.

The resistance selection circuit 41 constitutes a conversion coefficient changing means,
One of the resistors R2a-R2d, which adjusts the sensitivity of the FV converter 40 together with the capacitor C1 and the resistor R1, is selectively grounded. As shown in FIG. 4, this circuit includes a plurality of comparators 41) a to 41) d and these comparators 41) a to 4.
1) It is constituted by a plurality of transistors 412a to 412d which respectively ground the resistors R'1a to R2d by the output of d. If the load weight is O and the output of the smoothing circuit 51 is 3V, then the resistance R2a-R
2d is all grounded, and when the loaded weight exceeds the range of 0 and the output of the smoothing circuit becomes 2V, R2a-wR2c are grounded.As the loaded weight increases, the resistor R2b is grounded.
- It operates to sequentially reduce the grounded resistance of R2d. As a result, the sensitivity of the FV converter 40 changes according to the size of the loaded weight W, as shown in FIG. The output voltage Vfo of the device 40 increases.

Furthermore, due to the bounding of the wheels, the output a of the loaded weight sensor 23 changes rapidly as shown in FIG. 6(a), and accordingly, the output of the smoothing circuit 51 changes as shown in FIG. 6(b). Considering the case where the voltage changes from 2.2v to 1.8v, the output of the signal synthesis circuit 52 is a threshold value that changes the connection relationship between the resistors R2a and R2d, as shown in FIG. 6(c). The electric potential of 2V is lowered or exceeded depending on the frequency of the sawtooth wave. Therefore, as shown in FIG. 6(d), the grounding state of the transistor 412c, which controls the grounding state of the resistor R2c, changes in a short period, and as a result, the resistor R2c is in a grounded state and an ungrounded state. are repeated alternately according to the period of the sawtooth wave.

As a result, the conversion coefficient of the FV converter 40 becomes an intermediate conversion coefficient determined by the proportion of time when resistor R2C is grounded and the proportion of time when it is not grounded, and when a bounce occurs, this time proportion changes. It changes gradually, and the conversion coefficient also changes slowly. As a result, the output of the FV converter 40 also changes gradually, and it is possible to prevent the output signal from changing suddenly.

On the other hand, the correction circuit 42 works with the level adjustment circuit 43 so that the characteristic straight lines of speed S versus output Vfo for each weight O to 3 shown in FIG. 5(a) intersect at one point at a constant control start speed SO. This is to correct the output Vfo of the FV converter 40.

As mentioned above, the output of the loaded weight sensor 32 takes any value of 0.1.2.3 depending on the size of the loaded weight,
Accordingly, any one of 0 to 3 is selected for the input/output characteristics of the FV converter 40. In the present embodiment, the output voltages at the control start speed SO differ by the same amount of 0.5 V for each of the characteristic lines 0 to 3. Therefore, in order to obtain a characteristic that intersects at one point as shown in FIG. 5(b), for example, if the FV converter 4o is operating on the straight line of characteristic 2, It can be seen that it is sufficient to add 0.5V, add 1v when operating on a straight line with characteristic 1, and add 1.5v when operating on a straight line with characteristic 0.

The output of the smoothing circuit 51 is as shown in Table 1, when the output of the loaded weight sensor 32 changes between 0.1.2.3.
3.2.1. OV, the voltage value output from this smoothing circuit 51 is divided by 2, and the value is used as a correction value for the FV converter 4.
It can be seen that it is sufficient to add it to the output of 0. The level adjustment circuit 43 is a circuit for dividing the output of the smoothing circuit 51 by two.

The output Vfo of the FV conversion s40 corrected in this way
is supplied to the comparison/integration circuit 45 and compared with the voltage across the current detection resistor RC. Then, a voltage corresponding to the deviation between the two is supplied to a comparator 46, and the level is compared with a reference sawtooth wave outputted from a sawtooth wave generation circuit 48.

The comparator 46 operates to conduct the transistor TR for driving the solenoid 28 until the level of the reference sawtooth wave exceeds the output of the comparison/integration circuit 45. Therefore, due to the functions of the comparison and integration circuit 45, the comparator 46, and the sawtooth wave generation circuit 48, the average current value flowing through the solenoid 28 is adjusted to the output voltage Vc output from the correction circuit 42.
The value corresponds to o.

Further, the clamp circuit 47 is a circuit for reducing the current flowing through the solenoid 28 to zero until the vehicle speed S reaches the control start speed SO. This clamp circuit 47 is shown in FIG.
), the theoretical output voltage VT output from the correction circuit 42 when the vehicle speed S is the control start speed SO is compared with the actual output of the correction circuit 42, and the actual output is higher than the theoretical output voltage VT. If it is small, the comparison/integration circuit 45 does not output a signal.

As a result, the relationship between the vehicle speed S and the current flowing through the solenoid 28 becomes as shown in FIG. The current supplied to the solenoid 28 increases as the vehicle speed S increases along a characteristic straight line corresponding to the magnitude of .

As is clear from the characteristics shown in FIG. 5(C) and the action of the electromagnetic valve 20 described above, as the current supplied to the solenoid 28 increases, the amount of bypass between the compartments of the power cylinder 15 increases. , the assist force decreases. Therefore, as the vehicle speed S increases, the assist force gradually decreases, and the greater the loaded weight, the greater the rate of decrease in the assist force. As a result, when the loaded weight is large, sudden steering at high speeds can be prevented, resulting in high safety.

Furthermore, even if the output of the loaded weight sensor 23 changes suddenly due to wheel bounce, the conversion coefficient of the FV converter 40 changes smoothly, so even if the wheel bounce occurs, the current supplied to the solenoid 28 is Is does not change suddenly, and the steering characteristics can be prevented from changing suddenly.

<Effects of the Invention> As described above, in the present invention, an additional signal of a constant period is generated, this additional signal is combined with the output of the loaded weight sensor, and the vehicle speed is controlled based on the signal level of this combined signal. Since the current conversion coefficient is configured to be changed in stages, even if the output of the loaded weight sensor changes due to wheel bounce, the target current value output from the current value derivation means will not change suddenly. (Even if the wheels bounce, there is an advantage that this can prevent the assist force by the power steering device from changing suddenly and worsening the steering feeling.

[Brief explanation of the drawing]

1 to 6 show embodiments of the present invention.
The figure shows the overall structure of the power steering device, FIG. 2 is a sectional view showing the structure of the electromagnetic valve 20 in FIG. 1, and FIG.
FIG. 4 is an electric circuit diagram showing a specific example of the resistance selection circuit 41 in FIG. 3, and FIGS.
FIG. 6 is a time chart showing the operation of the steering characteristic control circuit 30 during bounce, and FIG. 7 is a diagram showing a conventional control circuit. 20... Solenoid valve, 28... Solenoid, 30...
Steering characteristic control circuit, 31... Vehicle speed sensor, 32...
Loaded weight sensor, 40... FV koji converter, 41... Resistance selection circuit (conversion coefficient changing means), 42... Correction circuit, 45... Comparison/integration circuit, 46... Comparator, 47・
... Clamp circuit, 48 ... Sawtooth wave generation circuit (additional signal generation means), 50 ... DA converter, 51 ...
Smoothing circuit, 52... Signal synthesis circuit, TR... Transistor.

Claims (1)

[Claims] (1) Steering of the power steering device in which the current supplied to the actuator for changing steering characteristics provided in the power steering device is changed based on both the output of the vehicle speed sensor and the output of the loaded weight sensor. a characteristic control device, a current value deriving means capable of deriving a target current value according to the vehicle speed detected by the vehicle speed sensor and changing a conversion coefficient of the target current value with respect to the vehicle speed in steps according to an external command; additional signal generating means for generating an additional signal whose signal magnitude changes at a constant cycle; signal synthesizing means for synthesizing the output of the additional signal generating means with the output of the loaded weight sensor; and the output of the signal synthesizing means. and a drive means for driving the actuator according to the target current value derived by the current value deriving means. A steering characteristic control device for a power steering device, characterized in that: