JPH0240546B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to rotational heating control of an oil pump for electric power steering, and more specifically, the present invention relates to rotational heating control of an oil pump for electric power steering. The present invention relates to an electric power steering device for a vehicle that controls the discharge amount of an oil pump.

Generally, when the vehicle speed is zero or when driving at low speeds, the number of times that steering is required increases and a large steering force is required.On the other hand, when driving at high speeds, the assisting effect of this large steering force is reduced, and the motor It is well known to reduce the amount and pressure of hydraulic oil discharged from an oil pump rotated by a motor.

The important features of power steering are:
The purpose is to set the steering force appropriately, and in order to generate the appropriate torque for steering, the amount of power assist is reduced to give a sense of response during small steering operations, and the amount of power assist is increased during sudden large steering operations. The current situation is to improve the sharpness of the steering wheel and provide an appropriate assist force so that the reduction in steering force does not become excessive when driving at high speeds. In this way, when driving at low speeds, the amount of hydraulic oil supplied is increased to make steering wheel operations easier, and when driving at high speeds, the amount of hydraulic oil is decreased to make the same operations heavier, thereby stabilizing driving. Power steering devices that allow this to occur are conventionally known. Furthermore, power steering devices have been known that generate control signals according to the steering angle, steering speed, and torque of the steering wheel by the operator, and apply an assist force in accordance with the steering only when steering is performed using these control signals. ing.
The former uses only a vehicle speed sensor to obtain the vehicle speed-sensitive rotation of the oil pump, and the latter uses only a steering sensor to obtain the steering-sensitive rotation. In devices with such sensitive characteristics, it is unavoidable that when driving at high speeds, due to an insufficient amount of hydraulic oil discharged from the oil pump, a heavy steering feeling similar to negative pressure occurs during sudden steering, a so-called stuck phenomenon. .

An object of the present invention is to adjust the oil pump according to the steering speed from the vehicle speed-sensitive base rotation line so that the amount of hydraulic oil discharged from the oil pump can be obtained by the appropriate oil pump assist rotation during steering according to the vehicle speed. It is an object of the present invention to provide a rotational assisting device for an oil pump for electric power steering which does not cause a stuck phenomenon in the steering feeling by improving the startup rotation.

Another object of the present invention is to create an OR circuit between the output pulse of the steering sensor and the output pulse of the vehicle speed sensor, and to delay the assist signal output from the OR circuit.
By using the OFF delay timer to shift the oil pump's low-speed base rotation to vehicle speed-sensitive assist rotation and maintain the assist rotation during the off period of both pulses, it is possible to maintain the vehicle speed-sensitive assist rotation while driving. The purpose of the present invention is to provide an electric power steering device that can perform the following tasks.

In order to achieve the above object, the present invention provides an oil pump for power steering that uses a vehicle speed sensor to perform auxiliary rotation in response to vehicle speed, as well as a steering angular velocity sensitive system that uses a steering sensor in accordance with each steering speed. It is configured to perform auxiliary rotation by. More specifically, when the steering speed is slow, the rotational output of the oil pump is boosted in response only to the vehicle speed as before, and in order to cope with sudden changes in the steering speed, Accordingly, the vehicle speed sensitive assist rotation line set in advance is moved up to a higher steering angular velocity assist rotation line corresponding to the steering speed, and the motor is energized. In other words, conventionally, when the vehicle is running at an extremely low speed and the vehicle is not being steered, the motor rotates at an extremely low speed, in other words, it is performing a warming-up rotation, and by steering at this time, the vehicle speed-sensitive acceleration is applied in accordance with the vehicle speed while the vehicle is running. Although it is known that this practice has been carried out, the present invention increases the pump rotational output to the vehicle speed-sensitive assist rotation line and constantly operates the oil pump even when the vehicle is running at low speed or idling without steering. In the vehicle speed sensitive rotation state, the pump rotational output is further configured to increase along a preset steering angular velocity acceleration rotation line according to changes in the steering angle and steering speed.

Embodiments of the electric power steering device for a vehicle according to the present invention will be described below with reference to the drawings.

In FIG. 1 showing an embodiment of the electric power steering device of the present invention, a steering wheel 1 is operatively connected to a control valve 3 via a steering shaft 2. As shown in FIG. control valve 3
The input side of the control valve 3 is connected to the supply port P and the return port T of the oil pump 4, respectively, and the output side of the control valve 3 is connected to the supply port P and the return port T of the oil pump 4, respectively, and the output side of the control valve 3 is connected to the supply port P and the return port T of the oil pump 4. If there is no need to stop the rotation of the cylinder, there is no need to provide a bypass valve). One terminal of the motor 7 that drives the oil pump 4 is connected to a power source 9 such as a battery or an alternator via a controller 8, and the other terminal is grounded.
The output of the vehicle speed sensor 10 and the output of the steering sensor 11 provided on the rotating part of the control valve 3 are both electrically connected to the controller 8.

An embodiment of the configuration of the controller 8 shown in FIG. 1 is shown in FIG. In FIG. 2, the pulse output of the steering sensor 11 is generated by a peak value hold pulse shaper 13 (in this embodiment, the pulse amplitude value is used, but a frequency-voltage conversion method may also be used) and an OR circuit 12. connected to the first input;
Further, the pulse output of the vehicle speed sensor 10 is connected to a frequency-voltage converter (F/V converter) 14 and a second input of an OR 12. The outputs of the pulse shaper 13 and the F/V converter 14 are both sent to the comparator circuit 1.
Connected to 8. The output of the comparison circuit 18 is connected via a pulse width modulation (PWM) amplifier 19 to the motor 7 which drives the oil pump. The output of the OR circuit 12 is a timer 1 that sets a delay time limit for the off time.
Connected to 5.

The operation of the circuit shown in Figure 2 is similar to that shown in Figures 3 and 4.
It will be explained as follows with reference to the figures. In FIG. 3, the pulse output X of the steering sensor 11
appears for a short time in the direction of time on the horizontal axis during steering,
Thereafter, the pulse output Y of the vehicle speed sensor 10 continues for a delay time set by the timer 15, and as the vehicle speed increases, the pulse output Y of the vehicle speed sensor 10 also appears for a short time in the time direction of the horizontal axis, and continues for a delay time set by the timer 15. last. Here, the pulse outputs of both sensors are
Since a logical sum is generated in the OR circuit 12,
The output of timer 15 produces a delayed output Z even after the individual pulse outputs X or Y have disappeared. As steering is performed frequently or the vehicle speed increases, the delayed output Z as a logical sum appears continuously over time, but if there is no X or Y pulse within the delay time, it is interrupted as shown by W. .

As shown in FIG. 4, the output signal (low-speed base level signal) b of the timer 15 obtained during low-speed base rotation is compared with the triangular wave signal c as a reference signal obtained from the triangular wave oscillator 17 in the comparison circuit 18. , Furthermore, the conversion output a corresponding to the vehicle speed output from the F/V converter 14 is also connected to the triangular wave signal c and the pulse shaper 1 in the comparison circuit 18.
3 with output signal x. In this way, the controller 8 produces a pulse width modulated amplified pulse signal d having steering angular velocity sensitive characteristics and vehicle speed sensitive characteristics as the output of the amplifier 19, and this pulse signal d is passed through a suitable smoothing circuit (not shown). The signal is supplied to the motor 7 as a motor drive signal e.

The running characteristics of the vehicle to be realized by the electric power steering apparatus shown in FIGS. 1 to 4 will be explained below with reference to FIGS. 5 to 6.

FIG. 5 shows the relationship between the rotational output of the oil pump (vertical axis) and the vehicle speed (horizontal axis) in a non-steering state. As shown in the figure, for example, when a car is stopped at a traffic light or is traveling at an extremely low speed, the rotational output of the oil pump is maintained at approximately 30%, which is below the no-steering low-speed rotation line L1, and then the vehicle speed When starting to increase, the rotational output of the oil pump immediately increases to about 100%, and as the vehicle speed further increases, the required rotational output of the oil pump decreases along the vehicle speed-sensitive assist rotation line L2. All of these changes occur in the base rotation region of the oil pump.

FIG. 6 shows the relationship between the rotational output of the oil pump (vertical axis) and the vehicle speed (horizontal axis) in the steering state. As shown in the figure, in the low-speed base rotation range where the vehicle speed is up to approximately 5 [Km/H], the rotational output of the oil pump is The line is maintained at approximately 100% for a while, but as the delayed output signal Z of the timer 15 disappears, the rotational output of the oil pump decreases.

By the way, in the driving characteristics shown in Figs. 5 and 6, when the vehicle speed exceeds a low speed such as 5 [Km/H], the rotational output of the oil pump increases to the vehicle speed sensitive assist rotation line L2, and the vehicle speed increases. The output of the pulse shaper 13 is output in accordance with the amplitude value of the output pulse of the steering sensor 11 in order to enter a state in which the rotation of the pump can be boosted at any time in response to a change in Based on the signal x, any one of the group of steering angular velocity acceleration rotation lines L2, L3, L4, and L5 is energized.
In FIG. 6, the steering angular velocity acceleration rotation line L2
is the vehicle speed sensitive assist rotation line L2 in FIG.
matches.

The driving characteristics when the vehicle starts from a stopped state and performs low steering or sudden steering will be explained with reference mainly to FIGS. 2 and 6. Now, if the vehicle speed increases to about 5 [Km/H] from the stopped state,
In the slow steering state, at the same time as the vehicle starts, the pulse shaper 13 inputs the voltage pulse output signal of the steering sensor 11 and generates an output signal x having one amplitude value. Voltage output signal a indicating vehicle speed and OFF delay timer 1
The rotational output of the oil pump increases from 30% to 100% in the low-speed base rotation region. At this time, when a constant steering condition is maintained, such as when traveling on a straight course or going up a ramp, the steering sensor 11
Pulse output It decreases as the vehicle speed increases. Here, for example, when the steering wheel is suddenly steered, a load for steering is applied to the oil pump 4 via the control valve 3, and this load causes the output of the motor 7 to fluctuate and its rotation to decrease. As a result, the discharge flow rate of the oil pump 4 is insufficient, which impedes the rotation of the steering wheel 1, causing so-called binding, making the steering wheel heavy and causing discontinuity in the steering feel. In order to avoid such a phenomenon, the pulse shaper 13 to which the pulse output X of the steering sensor 11 is input generates an output signal having an amplitude based on the above-mentioned change in the steering state, and this output signal is caused by sudden steering. Since a high voltage output is sometimes generated, the comparator circuit 18 selects a signal that can obtain an auxiliary rotation line corresponding to the sudden steering angular velocity from among the steering angular velocities [deg/sec] of the steering angular velocity auxiliary rotation lines L3, L4, and L5. Output.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of an electric power steering device of the present invention. FIG. 2 is a block circuit diagram showing one embodiment of the controller of FIG. 1. FIG. 3 is a signal waveform diagram showing each pulse output of the steering sensor and the vehicle speed sensor and a delayed output as a logical sum of the pulse outputs. FIG. 4 is a signal waveform diagram for explaining the operation of the circuit of FIG. 2. FIGS. 5 and 6 show vehicle running characteristic curves for explaining the oil pump rotation assisting operation of the electric power steering system according to the present invention. Explanation of symbols, 8... Controller, 10... Vehicle speed sensor, 11... Steering sensor, 12... OR circuit, 13... Pulse shaper, 14... Frequency voltage converter (F/V converter), 15... OFF delay timer, 1
7... Triangular wave oscillator, 18... Comparison circuit, 19... Pulse width modulation amplifier, L1... Non-steering low speed base rotation line, L2... Vehicle speed sensitive assist rotation line (steering angular velocity base assist rotation line), L3, L4, L5...
Steering angular velocity acceleration rotation line.

Claims (1)

[Scope of Claims] 1. An oil pump that is driven by a motor and supplies hydraulic oil to a power actuator, and a control valve that controls the supply of the hydraulic oil and is installed in a rotation system section of the control valve that controls the steering wheel. a steering sensor that senses angular velocity, a vehicle speed sensor that senses vehicle speed, and in response to an output signal of the steering sensor and an output signal of the vehicle speed sensor in order to control rotational output of the oil pump; An electric power steering device for a vehicle, comprising: a controller that outputs a control signal having a steering angular velocity sensitive characteristic and a vehicle speed sensitive characteristic; The control is configured to increase the rotational output of the oil pump from a low-speed base rotation line to a vehicle speed-sensitive base rotation line in response to the predetermined low speed and regardless of the presence or absence of steering when the predetermined low speed is exceeded. generating a first assist signal weighted to the signal, and in response to a change in steering angular velocity exceeding a predetermined steering angular velocity when the vehicle speed is in a travel range exceeding the predetermined low speed, the oil pump is activated; A second assist signal weighted on the control signal is configured to generate a rotational output from the vehicle speed sensitive base rotation line to a vehicle speed sensitive assist rotation line higher than the vehicle speed sensitive base rotation line. An electric power steering device characterized by: 2. When the controller is stopped or when the vehicle speed is around the predetermined low speed, after the output signal of the steering sensor is turned off,
The electric power steering apparatus according to claim 1, further comprising a delay means for maintaining the rotational output of the oil pump at the vehicle speed sensitive base rotation line for a predetermined period of time.