JP2936706B2 - Electric power steering device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus, and more particularly, to an assist motor (electric motor) in an automobile according to an output of a torque sensor for detecting a steering torque. The present invention relates to an electric power steering apparatus that controls the output of (1) and performs power assist according to the steering torque by the motor.

(Background technology)

2. Description of the Related Art Conventionally, in an automobile, in order to reduce steering operation at the time of steering, the motor current of an assist motor is increased or decreased or on / off controlled in accordance with the steering torque and the vehicle speed of a steering wheel, and the steering torque is controlled by the assist motor. A relatively large number of so-called speed-sensitive electric power steering devices that perform power assist in the steering direction according to the vehicle speed have been developed and put into practical use.

FIG. 7 shows a simplified configuration of this type of electric power steering apparatus. In FIG. 7, the steering torque input to the steering handle 51 can be detected by a torque sensor 53 attached to a steering shaft 52 which is a rotation shaft of the steering handle 51. The output of the torque sensor 53 and the output of the vehicle speed sensor 54 are input to a controller 60 that controls the assist motor 56. Further, although not shown here, a pulse for an ignition signal is actually input from an ignition circuit (not shown) to the controller 60.

The torque of the assist motor 56 is transmitted to a reduction gear mechanism 57 via an electromagnetic clutch 55, and the steering shaft 52
Via the steering gear 58. On the other hand, the steering torque of the steering handle 51 is also transmitted to the steering gear unit 58 via the steering shaft 52.

The steering gear portion 58 is generally provided with left and right front wheels 61, 62
The tie rod 59 is provided at the center of the tie rod 59, and is configured by a mechanism for converting the rotational movement of the steering shaft 52 into a reciprocating left and right movement of the tie rod 59, for example, a rack and pinion mechanism. Then, the tie rod 59 is driven left and right by the transmitted torque of the assist motor 56 and the steering torque of the steering handle 51, and the left and right front wheels 61 and 62 are steered via a knuckle arm (not shown).

In this figure, reference numeral 63 indicates a battery as a power supply.

With such a configuration, the torque sensor 53 and the vehicle speed sensor 5
By controlling the controller 60 according to the measurement value of 4, the motor current of the assist motor 56 is increased / decreased or turned on / off to perform required power assist. , And the auxiliary steering force is gradually reduced as the vehicle speed increases, and further, the steering becomes manual at a certain speed or higher, so that a stable steering performance can be obtained.

[Problems to be solved by the invention]

However, in the above conventional example, the command current-torque sensor output map is single as shown in FIG. 8, so that the coefficient of friction between the tire such as rainy weather and the ground is small and the tire becomes slippery. Power assist is performed with the same motor current as in fine weather.
For this reason, even if the handle is lighter in rainy weather than in fine weather, the driver turns the handle until the driver responds the same as in fine weather, in other words, until the steering wheel torque value becomes the same, There is a disadvantage that the steering wheel is turned too much (the steering angle of the steering wheel becomes large). Further, even when the tires such as snowy roads and frozen roads are very slippery, power assist is performed with the same motor current as in the case of general roads (ordinary roads without freezing etc.). For this reason, in such a case, there is a disadvantage that the handle becomes too light and the handle operation becomes unstable. On the other hand, the driver always considers the value of the coefficient of friction between the tire and the ground in order to prevent the steering wheel from turning too much in rainy weather and instability in steering on snowy and frozen roads. While operating the steering wheel, or on a snowy day or on a frozen road, the steering fee of the steering wheel is extremely conservative, and on a general road, on a rainy day, make it somewhat less and on a sunny day a little more. It is necessary to empirically learn the body with that feeling so that the steering amount is appropriate. In such a case, the driver's steering feeling is equivalent on a snowy road, a frozen road, a general road when it is sunny or rainy. It also had the disadvantage of being different.

[Object of the invention]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the conventional example, and has as its object to prevent the steering wheel from being excessively turned in rainy weather and to prevent the steering wheel from being unstable on a snowy or frozen road. It is an object of the present invention to provide an electric power steering apparatus that can make the driver's operation feeling almost the same regardless of whether it is a snowy road, a general road, or fine weather or rainy weather.

[Means for solving the problem]

The present invention provides a torque sensor for detecting a steering torque of a steering wheel, a vehicle speed sensor for detecting a vehicle speed, and a control unit for increasing / decreasing a motor current of an assist motor in accordance with an output value of the two sensors, or for controlling on / off. With
In an electric power steering device configured to perform power assist in a steering direction according to a steering torque by an output of an assist motor, a control unit includes a wiper switch for setting an operation state of a wiper of the vehicle, and detection of an outside air temperature. A temperature sensor for controlling the position of the wiper switch based on an output signal of the wiper switch, and a control unit that determines a position of the wiper switch according to the determined position, steering torque, vehicle speed, and outside temperature. A target current determination function for determining a command current value of the assist motor, and determining that the command current value is minimized when the wiper switch is on and the outside air temperature is 0 ° C. or less. I am taking it. This aims to achieve the above-mentioned object.

First Embodiment Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 4.

Here, the same reference numerals are used for the same components as those in the above-described conventional example, and the configuration is simplified or omitted.

As shown in FIG. 1, this embodiment has the same overall configuration as the above-described conventional example, except that the controller 10 is used instead of the controller 60 as a control unit. It is characterized in that a wiper switch 1 and a temperature sensor 2 for detecting an outside air temperature of the vehicle are connected. Other configurations are the same as those of the above-described conventional example.

FIG. 2 shows the overall circuit configuration of this embodiment. In this figure, the CPU 11 of the controller 10 includes:
The torque sensor 53, the vehicle speed sensor 54, the wiper switch 1, and the temperature sensor 2 are connected via an input circuit (not shown), and output signals of the respective sensors are input.

The torque sensor 53 detects a torsion angle (amount) of a not-shown torsion bar provided on the steering shaft 52, and outputs a voltage signal corresponding to the torsion angle. The torque sensor 53 outputs two types of output signals, a main output and a sub output.
Normally, the values of these output signals coincide with each other. However, if the variable resistor (not shown) constituting the torque sensor 53 is worn over time, the values of both output signals are shifted. Thus, the CPU 11 of the controller 10 determines whether the torque sensor is abnormal. Vehicle speed sensor 54
Is used for a speedometer and outputs a pulse signal corresponding to the vehicle speed.

The wiper switch 1 sets an operation state of a wiper (not shown) of the vehicle and outputs a signal corresponding to each operation state. That is, the wiper switch 1 is set to “INT
(Intermittent) ”,“ Lo (low speed) ”, and“ Hi (high speed) ”.

The temperature sensor 2 is mounted outside the vehicle body (not shown) and changes its resistance value depending on the temperature to output a voltage signal corresponding to the outside air temperature. A switch or the like may be used.

Further, the controller 10 receives an ignition signal of an ignition circuit (not shown).

On the other hand, an assist motor 56 and an electromagnetic clutch 55 are connected to the output side of the controller 10. And
The assist motor 56 has its current value and forward / reverse rotation controlled by the controller 10, and the electromagnetic clutch 55 is turned “ON” by the controller 10.
“OFF” is controlled, and the assist motor 56 and the reduction gear mechanism 53 are intermittently connected.

Further, the controller 10 detects an abnormality of the torque sensor 53 or another abnormality and outputs a diagnosis signal to an external display device (not shown).

Next, the main control functions of the controller 10 will be described with reference to the flowchart of FIG.

When an ignition switch (not shown) is turned “ON” when starting the engine, the controller 10 starts operating. When the engine (not shown) starts,
An ignition signal from an ignition circuit (not shown) is input to the CPU 11 via an input circuit (not shown) of the controller 10. Then, the CPU 11 outputs a clutch-on signal to the electromagnetic clutch 55 and calculates the vehicle speed based on the signal input from the vehicle speed sensor 54 (step S101). As a result, the assist motor 56 is connected to the speed reduction mechanism 57, and the power assist is enabled.

Next, the PCU 11 determines whether the vehicle speed is 40 km / h or less (S102). If the vehicle speed exceeds 40 km / h, there is no need for power assist, so the assist motor 56 is stopped and the subroutine for turning off the electromagnetic clutch 55 (motor / clutch OFF processing routine) is performed. (S111). On the other hand, when the vehicle speed is 40 km / h or less,
The steering wheel torque value is calculated based on the signal input from the torque sensor 53 (S103).

Next, the CPU 11 determines whether or not the wiper switch 1 is "ON" (S104). And the wiper switch 1
Is OFF, the CPU 11 proceeds to step S106, calculates the outside air temperature based on the signal input from the temperature sensor 2, and then determines whether or not the outside air temperature is 0 ° C. or lower (S10).
7). Here, if the outside air temperature exceeds 0 ° C., there is no danger of road freezing.
At the time of the wiper OFF corresponding to the vehicle speed and the steering wheel torque value calculated in steps S101 and S103, respectively, from the steering wheel torque-motor current map for a general road as shown in FIG. The motor current (indicated by a solid line in the figure) is read out (S108). On the other hand, if the outside air temperature is 0 ° C. or less at step S107, the CPU 11 proceeds to step S109 to store the data for the snowy road and frozen road as shown in FIG. The motor current at the time of the wiper OFF (shown by a solid line in the figure) corresponding to the vehicle speed and the steering wheel torque value is read from the steering wheel torque-motor current map.

On the other hand, in step S104, the wiper switch 1
Is "ON", it is determined whether the wiper switch 1 is in the "INT", "Lo", or "Hi" position (S105), and the outside air temperature is calculated as before. (S1
06), it is determined whether or not the outside air temperature is 0 ° C. or less (S107). Here, if the outside air temperature exceeds 0 ° C., there is no danger of the road being frozen. Therefore, the CPU 11 determines the vehicle speed and the steering wheel torque from the steering wheel torque-motor current map for the general road shown in FIG. At the time of the wiper position determined in step S105 corresponding to the value, for example, the motor current (indicated by a dotted line in the figure) at the time of the "Hi" position is read (S108). On the other hand, if the outside air temperature is equal to or lower than 0 ° C. in step S107, the CPU 11 proceeds to step S109, in which the steering wheel steering for snowy road and frozen road shown in FIG. From the torque-motor current map, the motor current (indicated by a dotted line in the figure) at the time of the wiper position, for example, at the “Hi” position determined in step S105 corresponding to the vehicle speed and the steering wheel torque value is read. Here, in FIG. 4 (1) and (2),
As the motor current value when the wiper switch is ON, only the value at the time of the “Hi” position is shown, but this is because the illustration of the other positions is omitted for convenience of drawing. Are stored in the internal memory 12 at the "INT" and "Lo" positions, and the motor current is determined by these.

Next, the CPU 11 proceeds to step S110 and proceeds to step S10
The motor current of the assist motor 56 is controlled according to the motor current value read in 8 or S109. Thereby, required power assist is performed by the assist motor 56.

Then, in any case of steps S110 and S111, the CPU 11 returns to step S101 and repeats the same control operation as described above.

As described above, according to the first embodiment, the wiper switch 1 and the temperature sensor 2 are connected to the controller 10, and the controller 10 controls the vehicle speed, the steering wheel torque, and the like.
Since the assist motor 56 is controlled so as to change the motor current value also according to the position of the wiper switch 1 and the outside air temperature, the power assist force between the fine weather and the rainy weather on a general road is not constant, Moreover,
When the weather is clear when the wiper switch 1 is "OFF", the motor current value is the highest, followed by potty rain (wiper switch 1 is set to "INT") → light rain (wiper switch 1 is set to "Lo") ) → heavy rain (the wiper switch 1 is set to “Hi”). The motor current value is controlled to decrease in this order. In other words, since the motor current is controlled to be lower, the friction coefficient between the tire and the ground becomes smaller, and the steering wheel becomes heavier as the tire becomes more slippery. Therefore, irrespective of whether it is sunny or rainy, and irrespective of whether it is a general road, snowy road or frozen road,
By steering the steering wheel until the same response is obtained, it is possible to obtain a substantially constant tire turning angle, and the steering wheel becomes too sharp in rainy weather, and steering becomes unstable on snowy and frozen roads Inconveniences such as the above can be effectively prevented, and the steering feel of the driver can be made substantially constant without being greatly influenced by the road surface condition.

Second Embodiment Next, a second embodiment of the present invention will be described.

This embodiment is configured in the same manner as the first embodiment, but the method of setting the motor current of the controller 10 is as follows.
This is different from the first embodiment.

That is, in this embodiment, the CPU 1 of the controller 10
The internal memory 12 stores in advance a steering wheel torque-motor current map when the wiper switch is OFF on a general road indicated by a solid line in FIG. 4 (1) and values of conversion constants k and l shown in FIG. ing.

Next, the control operation of the controller 10 in this case will be described with reference to the flowchart of FIG.

When an ignition switch (not shown) is turned “ON” when starting the engine, the controller 10 starts operating. When the engine (not shown) starts,
An ignition signal from an ignition circuit (not shown) is input to the CPU 11 via an input circuit (not shown) of the controller 10. Then, the CPU 11 outputs the clutch-on signal to the electromagnetic clutch 55 and calculates the vehicle speed based on the signal input from the vehicle speed sensor 54 (step S201). As a result, the assist motor 56 is connected to the speed reduction mechanism 57, and the power assist is enabled.

Next, the CPU 11 determines whether the vehicle speed is 40 km / h or less (S202). If the vehicle speed exceeds 40 km / h, there is no need for power assist, and the process proceeds to a motor / clutch OFF processing routine (S212). On the other hand, when the vehicle speed is 40 km / h or less, the steering wheel torque value is calculated based on the signal input from the torque sensor 53 (S203).

Subsequently, the CPU 11, reading (S204) the motor current value I _M from the internal memory 12 corresponding to the vehicle speed and the torque, the wiper switch 1 determines whether "ON" (S205). When the wiper switch 1 is “OFF”, the CPU 11
Then, the process proceeds to step S208, where the outside air temperature is calculated based on the signal from the temperature sensor 2, and thereafter, it is determined whether the outside air temperature is 0 ° C. or less (S209). Here, if the outside air temperature exceeds 0 ° C., there is no possibility of road freezing, so the CPU 11 controls the current value of the assist motor 56 so as to become the current value I _M read in step S204. (S211). On the other hand, if the outside air temperature is equal to or lower than 0 ° C. in step S209, the CPU 11 proceeds to step S210 and corrects the current value I _M read in step S204 into the correction constant 1 (=
0.6), and that value is used as a new motor current value I _MZ . Then, the CPU 11 controls the current value of the assist motor 56 so that the current value becomes I _MZ . Thereby, required power assist is performed by the assist motor 56.

On the other hand, when the wiper switch 1 is “ON” in step S205, the wiper switch 1
It is determined whether the position is “T”, “Lo”, or “Hi” (S206). Then, in the CPU 11, step S206
In the variable constant k corresponding to the determined position (e.g., if 0.95 "INT") reads from the internal memory 12, and multiplies the conversion constant k in the motor current value I _M which is read in step S204, The value I _MW is determined as a new motor current value (S207), and the process proceeds to step S208 to calculate the outside air temperature. Then, it is determined whether or not the outside air temperature is 0 ° C. or less (S209). Here, when the outside air temperature is greater than 0 ° C., since there is no risk of the road connecting to control the current value of the assist motor 56 so that the newly determined I _MW in step S207 (S221). With this, the assist motor
56 provides the required power assist. On the other hand, if the outside air temperature is equal to or lower than 0 ° C. in step S209, the CPU 11 proceeds to step S210 and corrects the current value I _M read in step S204 into the correction constant l stored in the internal memory 12.
(For example, 0.5 for “INT”), and the value is used as a new motor current value I _MZ . Then, the CPU 11 controls the current value of the assist motor 56 so that the current value becomes I _MZ . Thereby, required power assist is performed by the assist motor 56.

Then, the CPU 11 returns to step S201 and repeats the same control operation as described above in any case of steps S211 and S212.

As described above, according to the second embodiment, the values of the conversion constants k and l are changed as shown in FIG.
Is set to become smaller in the order of “INT” → “Lo” → “Hi”, and the conversion constant l when the outside air temperature is 0 ° C. or less is set smaller than the conversion constant k when the outside air temperature exceeds 0 ° C. Accordingly, the motor current is gradually reduced in accordance with this, the coefficient of friction between the tire and the ground is reduced, and the handle becomes heavier as the tire becomes more slippery.
Therefore, according to the second embodiment, the same effects as those of the first embodiment can be obtained, and there is no need to store the steering wheel torque-motor current map for each position as shown in FIG. 4 in the memory. Therefore, the memory capacity can be reduced by that much, and the adjustment of the assisting force is very simple because it is only necessary to change the value of the correction constant.

〔The invention's effect〕

Since the present invention is configured and functions as described above, according to this, the position of the wiper switch is determined by the wiper switch position determination function of the control unit, and the position determined by the target current determination function of the control unit. , The command current value of the assist motor is determined according to the steering torque, the vehicle speed and the outside temperature, so that the current value of the assist motor according to the position of the varipper switch, that is, the rainfall or snowfall, can be controlled. For example, when using a three-stage wiper switch, when the wiper switch “OFF” is sunny, the motor current value is highest, and then the motor current value is “INT” → “Lo” → “Hi” in the order of the wiper switch. The motor current value should be set so that the motor current value is lower when the outside air temperature is 0 ° C or lower than when the outside air temperature exceeds 0 ° C. Thus, the handle becomes heavier as the coefficient of friction between the tire and the ground becomes smaller and the tire becomes more slippery. Therefore, regardless of whether it is sunny or rainy, and regardless of whether it is a general road, snowy road, or frozen road, the steering wheel can be steered until the same response is obtained, thereby obtaining a substantially constant tire turning angle. This makes it possible to effectively prevent inconvenience when the steering wheel is turned too much in rainy weather and the steering wheel becomes unstable on snowy or frozen roads, and the steering wheel feeling of the driver is affected by the road surface condition. It is possible to provide an excellent electric power steering device which can be made substantially constant without being required.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the overall configuration of the first embodiment of the present invention, FIG. 2 is a block diagram showing the circuit configuration of the embodiment of FIG. 1, and FIG. 4 (1) is a diagram showing a steering wheel torque-motor current map on a general road stored in the internal memory of FIG. 2, and FIG. 4 (1) is a flowchart showing the control program. FIG. 5 is a diagram showing a steering wheel torque-motor current map on a snowy road or a frozen road stored in the controller of FIG. 5, FIG. 5 is a flowchart showing a main control program of a controller according to a second embodiment of the present invention, and FIG. FIG. 7 is a table showing conversion constants corresponding to respective positions of a wiper switch stored in an internal memory in the embodiment, FIG. 7 is an explanatory diagram showing a configuration of a conventional example, and FIG. It is a diagram showing a map. DESCRIPTION OF SYMBOLS 1 ... Wiper switch, 2 ... Temperature sensor, 10 ... Controller as a control part, 51 ... Steering handle, 53 ... Torque sensor, 54 ... Vehicle speed sensor, 56 ... Assist motor.

────────────────────────────────────────────────── (5) Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI B62D 119: 00 137: 00 (56) References JP-A-61-257363 (JP, A) JP-A-63-121569 (JP, A) JP-A-59-140167 (JP, A) JP-A-4-191174 (JP, A) JP-A-3-258650 (JP, A) Full-scale operation Sho-59-37178 (JP, U) Real-time operation -151776 (JP, U) Actually open 58-152458 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B62D 5/04

Claims (1)

(57) [Claims] A control unit for increasing / decreasing or turning on / off a motor current of an assist motor in accordance with an output value of a torque sensor for detecting a steering torque of a steering wheel, a vehicle speed sensor for detecting a vehicle speed, and an output value of both sensors. An electric power steering apparatus configured to perform power assist in a steering direction according to a steering torque by an output of the assist motor, wherein the control unit sets an operation state of a wiper of the vehicle. And a temperature sensor for detecting an outside air temperature, wherein the control unit determines a position of the wiper switch based on an output signal of the wiper switch, a wiper switch position determination function, and the determined position, steering torque, A command current value of the assist motor is determined according to a vehicle speed and an outside temperature. An electric power steering having a target current determining function, wherein the command current value is determined to be the smallest when the wiper switch is on and the outside air temperature is 0 ° C. or less. apparatus.