JPH05270427A - Electric motor-driven pump type power steering device - Google Patents

Abstract

PURPOSE:To provide steering performance with no unevenness by designing control of applied voltage in the beginning of electrifying an electric motor for driving a vane pump, in a device wherein delivery pressure oil of the vane pump, whose rotational speed is changed in accordance with a car speed, is supplied/discharged to/from a power cylinder. CONSTITUTION:When a steering handle is steered, an oil pressure, generated in a vane pump 20 driven by an electric motor 40 and supplied/discharged to/ from each operating chamber 15b of a power cylinder 15, is controlled by a servo valve 12 associated with steering, thus to power-steer a front wheel 18. The electric motor 40 is controlled to be electrified by car speed induction voltage calculated in an electronic control unit 45 based on an output of a car speed sensor 46. In the case of this electrification control, at steering assist starting time, applied voltage is controlled so as to increase for a predetermined short time to the voltage or more at which a rotational speed is obtained of a rotor with the point end of a vane brought into contact with an elliptical internal peripheral surface of a cam ring by centrifugal force, in the vane pump 20. In this way, responsiveness of steering is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid type power steering apparatus using an electric pump, and in particular, by changing the rotational speed of an electric motor for driving a vane type pump in accordance with a running state such as a vehicle speed. The present invention relates to a fluid-type power steering device that controls a steering assist force according to a traveling state.

[0002]

2. Description of the Related Art In a fluid power steering apparatus, control of supply and discharge of a working fluid from a pump to a power cylinder that generates an assisting force for steering is performed by a servo that operates according to a manual torque applied to a steering wheel. It is done by a valve.
This pump is normally a vane type that is driven by the engine of the automobile and has a constant discharge amount by a bypass valve, and this is combined with a solenoid valve whose opening is controlled according to the vehicle speed, The steering assist force is large at low speed and small at high speed. Also,
Some midship engine vehicles, etc., in which the distance between the engine and the power steering device is large, use an electric pump in order to avoid lengthening the piping for the working fluid. Also in this case, an electric pump with a constant discharge amount is usually used, and the steering assist force is controlled by an electromagnetic valve controlled according to the vehicle speed and the like, as described above.

On the other hand, the electronic control unit calculates a voltage (for example, a vehicle speed sensitive voltage E shown in FIG. 6) according to the vehicle speed and applies it to an electric motor for driving the pump to change the rotational speed of the pump. Thus, there is also one that controls the steering assist force according to the traveling state, and according to this, the solenoid valve that is controlled according to the vehicle speed or the like can be omitted.

[0004]

In the above-mentioned last prior art, the DC electric motor for driving the pump has its rotational speed increased substantially proportionally to the applied voltage as shown in FIG. 7, for example. .. On the other hand, for example, in the vane type pump 20 as shown in FIGS. 2 and 3, when the rotation speed of the rotor 25 is low at the initial stage of rotation, the tip of the vane 26 slidably held in the slit 25a is Since the working fluid is not always contacted with the inner peripheral surface of the cam ring 23, the working fluid is not discharged, and the vane 26 pops out in the radial direction by the centrifugal force and comes into contact with the cam ring 23 at all times. Discharging is started. Once the discharge is started, pressure is generated in the discharge chamber 34 and the communication hole 37
This pressure introduced to the root side of the slit 25a via the back pressure groove 36 causes the tip of the vane 26 to move to the cam ring 2
Since it is pressed against the inner peripheral surface of 3, the discharge from the pump 20 is continued even if the rotation speed decreases to some extent.

However, the rotational speed of the rotor 25 when the vane 26 is projected in the radial direction and abuts on the cam ring 23 due to the centrifugal force is affected by the frictional force between the slit 25a and the vane 26 and the viscosity of the working fluid, and thus is constant. The value does not vary depending on the individual product or the operating environment such as temperature. Therefore, even if the voltage calculated according to the vehicle speed or the like is applied to the electric motor 40 to control the rotation speed of the rotor 25, the vehicle speed at which the steering assist is started varies and the steering feeling varies. is there. The present invention aims to solve such problems.

[0006]

To this end, an electric pump type power steering apparatus according to the present invention, as illustrated in FIGS. 1 to 7, includes a power cylinder 15 for generating an assist force,
A pump 20 which is driven by an electric motor 40 whose rotation speed increases in accordance with an increase in applied voltage to supply a working fluid to the power cylinder 15, and a steering handle 11 which is provided between the power cylinder 15 and the pump 20. The power cylinder 1 is operated according to the manual torque applied to the power cylinder 1.
5, a servo valve 12 for controlling the supply and discharge of the working fluid to and from the working chamber 15b, and an electronic control unit 45 for calculating a voltage according to a traveling state such as a vehicle speed and applying the voltage to the electric motor 40,
The pump 20 includes a large number of radial slits 2
A rotor 25, which holds slidably each vane 26 protruding outward in the radius 5a, is rotatably supported by a housing 21, and is provided between an inner peripheral surface of a cam ring 23 provided in the housing 21 and the rotor 25. A plurality of pump chambers 32 defined by the vanes 26 are formed in the rotor 2
Due to the change in the volume of the pump chamber accompanying the rotation of 5, the suction chamber 3
In the electric pump type power steering apparatus in which the working fluid in 0 is sent to the discharge chamber 34 and the pressure in the discharge chamber is introduced to the root side in each of the slits 25a, the electronic control unit 45 includes the vane 26 Voltage control means 45a for increasing the voltage applied to the electric motor 40 for a predetermined short time up to a voltage at which the rotational speed of the rotor 25 at which the tip of the rotor reliably contacts the inner peripheral surface of the cam ring 23 is obtained.
It is characterized by having.

[0007]

The electronic control unit 45 calculates a voltage according to the traveling state such as the vehicle speed and applies it to the electric motor 40, and the voltage control means 45a increases the voltage applied to the electric motor 40 for a predetermined short time. As a result, the rotational speed of the rotor 25 is temporarily increased, the tip of the vane 26 contacts the inner peripheral surface of the cam ring 23, and the discharge of the working fluid from the pump 20 is immediately started. After that, the voltage applied to the electric motor 40 is returned to the voltage calculated according to the traveling state such as the vehicle speed.
Since the tip of the vane 26 is constantly pressed against the inner peripheral surface of the cam ring 23 by the pressure in the discharge chamber 34 introduced to the base side of the slit 25a, the discharge of the working fluid from the pump 20 is continued.

[0008]

As described above, according to the present invention, the voltage calculated by the electronic control unit increases in accordance with the traveling state such as the vehicle speed, and is relatively small corresponding to the rotational speed at which the discharge of the pump is started. If the specified value is exceeded, the discharge of the working fluid from the pump will start reliably, so regardless of changes in the working environment such as variations in the frictional force of individual products or changes in the viscosity of the working fluid due to temperature, When the traveling state such as the vehicle speed reaches a predetermined state, the assist is surely started, so that the steering feeling does not vary.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the overall structure of a front wheel power steering apparatus 10 embodying the present invention will be described with reference to FIG. The front wheel power steering apparatus 10 includes a servo valve 12 provided in the middle of transmitting a rotation of the steering wheel 11 to a rack and pinion mechanism 13 for converting the reciprocating motion of an operating rod 14 and a power cylinder 15 provided on the operating rod 14. Is the main component. The working fluid discharged from the pump 20 rotationally driven by the electric motor 40 is supplied to the servo valve 12. Servo valve 1
Reference numeral 2 denotes a known rotary type, which operates in response to a manual torque applied from the steering handle 11 via the input shaft 12a and is supplied from the pump 20 to both working chambers 15b on both sides of the piston 15a of the power cylinder 15. Control the supply and discharge of the working fluid. As a result, the operating rod 14
Is applied with an assisting force, both front wheels 18 are steered via tie rods 16 and knuckle arms 17 provided at both ends thereof, and the used working fluid is returned to the reservoir 38.

As shown in FIGS. 2 and 3, the pump 20 is a vane pump, and a cam ring 23 and side plates 22 and 24 sandwiching both sides of the cam ring 23 are provided in the housing 21.
The guide pins 27 of the book prevent them from rotating and the springs 28 press them against each other. A substantially elliptical inner peripheral surface is formed on the cam ring 23. Inside the cam ring 23, a rotor 25 having substantially the same width as the cam ring 23 is spline-coupled to the tip of an output shaft 41 of an electric motor 40 that rotationally drives the pump 20. And is rotatably supported. Mainly as shown in FIG. 3, ten slits 25a extending radially at equal angular intervals to reach the outer periphery are formed in the rotor 25 over the entire width, and each slit 25a is provided with a plate-shaped vane 26 in a substantially liquid-tight manner. It is slidably held by projecting radially outward. As shown in FIG. 7, the electric motor 40 is a DC motor having a characteristic that the rotation speed increases almost proportionally according to the applied voltage.

In the operating state, the tip of each vane 26 is brought into contact with the inner peripheral surface of the cam ring 23 to form ten pump chambers 32 defined between the inner peripheral surface and the outer peripheral surface of the rotor 25. ing. The volume of each pump chamber 32 increases and decreases with the rotation of the rotor 25 shown by the arrow, but each side plate 2
A pair of suction ports 31 are formed in the positions 2 and 23 where the volume increases, and a pair of discharge ports 33 are formed in the position where the volume decreases. The suction port 31 is communicated with a suction chamber 30 formed in the housing 21 and provided with a suction port 29, and the discharge port 33 is communicated with a discharge chamber 34 formed in the housing 21 and provided with a discharge port 35. There is. Therefore, each pump chamber 3 accompanying the rotation of the rotor 25
Due to the change in the volume of 2, the working fluid in the suction chamber 30 is sucked into the pump chamber 32 and sent out into the discharge chamber 34.
Four back pressure grooves 36, which communicate with the roots of the slits 25a, are formed on the surfaces of the side plates 22 and 24 that come into contact with the rotor 25. Through the communication hole 37 formed in the discharge chamber 3
The pressure in 4 has been introduced.

As shown in FIG. 1, the electric motor 40 is connected to an electronic control unit 45 to control the rotation speed. In this embodiment, the electronic control unit 45 calculates a vehicle speed sensitive voltage E as shown in FIG. 6 based on the vehicle speed v detected by the vehicle speed sensor 46 and applies it to the electric motor 40 to apply it to the rotor of the pump 20. It controls the rotation speed of 25.
The electronic control unit 45 does not always apply the calculated vehicle speed sensitive voltage E to the electric motor 40, but if the calculated vehicle speed sensitive voltage E increases and reaches a relatively small predetermined value as described below. A considerably large voltage is applied to the electric motor 40 for a predetermined short time, and then the calculated vehicle speed sensitive voltage E is applied to the electric motor 40 again.

Next, the details of the operation of the above embodiment will be described with reference to the flow chart shown in FIG. When the main switch of the automobile is turned on, the central processing unit (simply called CPU) of the electronic control unit 45 first sets each variable to a predetermined initial value (the initial value of the flag F is 1), and every predetermined small time. Each time an interrupt signal is input to, the control operation shown in the flowchart of FIG. 4 is repeatedly executed. First, in step 100, the CPU calculates a vehicle speed sensitive voltage E shown in FIG. 6 using a map or an arithmetic expression which is input from the vehicle speed sensor 46 and is built in based on the vehicle speed v. In the low speed traveling state immediately after the start of traveling, the vehicle speed sensitive voltage E is large (E ≧ a, E ≧ b) and F = 1, so the CPU executes the control operation in step 1
01 through steps 102 and 103 to step 108
Then, the vehicle speed sensitive voltage E calculated in step 100 is applied to the electric motor 40.

The vehicle speed sensitive voltage E is shown in FIG. 6 as the vehicle speed increases.
As shown in FIG. 5, the rotation speed of the electric motor 40 and the discharge amount of the pump 20 are correspondingly decreased.
Therefore, the assist force provided by the front wheel power steering apparatus 10 also gradually decreases, the electric motor 40 and the pump 20 stop immediately before the vehicle speed v1 at which the vehicle speed sensitive voltage E becomes 0, and when traveling at a higher speed than that, the front wheel power steering apparatus. 10 does not generate an assisting force. In this process in which the vehicle speed sensitive voltage E decreases as the vehicle speed increases, if E <b, the CPU advances the control operation from step 102 to step 108, and if the vehicle speed sensitive voltage E further decreases and becomes E <a. The control operation proceeds from step 101 to step 107, and after setting F = 0, the process proceeds to step 108, but the above operation is not changed.

Next, when the applied voltage to the electric motor 40 is 0 (position at time t1 in FIG. 5) at a high speed equal to or higher than the vehicle speed v1, or when the vehicle speed is lower than that, the applied voltage is equal to or less than a predetermined small value a described below. From now on, the case where the applied current gradually increases as the vehicle speed decreases will be described. Vehicle speed sensitive voltage E
Is less than the voltage a (between times t1 and t2), the CPU advances the control operation from step 101 to steps 107 and 108 to apply the vehicle speed sensitive voltage E to the electric motor 40.
Since the electric motor 40 does not operate or the rotation speed is low and the tip of the vane 26 does not contact the inner peripheral surface of the cam ring 23, the working fluid is not discharged from the pump 20. When the vehicle speed sensitive voltage E exceeds the voltage a but is less than the relatively small predetermined value b described below (between times t2 and t3), C
The PU advances the control operation from step 102 to step 108 to apply a slightly higher vehicle speed sensitive voltage E to the electric motor 4
0 is rotated at a low speed, but the vane 26 makes the cam ring 23
Since it is lower than the rotational speed at which it abuts the inner peripheral surface of the pump 20,
There is no discharge of working fluid from.

The voltage b is the voltage at which the vane 26 comes into contact with the inner peripheral surface of the cam ring 23 and the discharge from the pump 20 is started when the vehicle speed sensitive voltage E increases (the minimum value of variation due to each product). The voltage at which the vane 26 moves away from the inner peripheral surface of the cam ring 23 and the discharge from the pump 20 is stopped when the vehicle speed sensitive voltage E decreases (maximum value of variation).
It is a voltage that is required to start the discharge from the pump 20. The voltage a is a voltage that is slightly smaller than the voltage at which the vane 26 separates from the inner peripheral surface of the cam ring 23 and the discharge from the pump 20 is stopped (the minimum value of variation) when the vehicle speed sensitive voltage E decreases.

When the vehicle speed further decreases and the vehicle speed sensitive voltage E becomes equal to or higher than b (at a position exceeding time t2 in FIG. 5), CP
U advances the control operation from step 10 to step 103, and since F = 0 in this state, advances the control operation to step 104 and applies a predetermined high voltage c to the electric motor 40. In this voltage c, the tip of the vane 26 has the cam ring 23.
The voltage is higher than the rotation speed of the rotor 25 that reliably contacts the inner peripheral surface of the rotor. CPU steps 104 and 10
5 is repeated for a predetermined short time T1 to pump this voltage c.
Apply to. The steps 104 and 105 compose a voltage control means. Steps 104 and 10
5, the rotational speed of the pump 20 is temporarily increased, the vane 26 comes into contact with the inner peripheral surface of the cam ring 23, and the discharge is started. When the time T1 has elapsed, the CPU advances the control operation to step 106, sets F = 1 and once ends the control operation according to the flowchart of FIG. This time T1 is for pump 2
It is sufficient for the rotational speed of 0 to temporarily increase and the vane 26 to come into contact with the inner peripheral surface of the cam ring 23 to reliably start the discharge, but the discharge time increases too much and affects the steering feeling. The time should not be given.

After that, the CPU repeats the control operation of the flowchart of FIG. 4 each time the interrupt signal is input again at every predetermined small time. In this state, E ≧ b, but F = 1
Therefore, the CPU advances the control operation from step 103 to step 108, and applies the vehicle speed sensitive voltage E calculated in step 100 to the electric motor 40 each time. As a result, the voltage applied to the electric motor 40 changes according to the vehicle speed that changes with time, as shown in FIG.
Since the amount of the working fluid supplied to the front wheel power steering apparatus 10 from 0 also changes in the same manner, the steering force control according to the vehicle speed is performed.

When the vehicle speed v1 is increased and the vehicle speed sensitive voltage E is decreased to be less than a predetermined voltage b which is relatively small as at the position of time t4 in FIG. 5, the CPU executes the control operation in step 102.
To Step 108, the vehicle speed sensitive voltage E is applied to the pump 20. Although the vehicle speed sensitive voltage E at this time is less than the voltage b, it is higher than the voltage at which the vane 26 separates from the inner peripheral surface of the cam ring 23, so the pump 20 continues to discharge the working fluid to the front wheel power steering apparatus 10. ing. From this state, if the vehicle speed sensitive voltage E increases again and exceeds the voltage b (position at time t5), the CPU executes the control operation in step 10
The process proceeds from step 2 to step 103, but since F = 1 remains, the control operation proceeds from step 103 to step 108. Therefore, in this case, the high voltage c is not temporarily applied to the electric motor 40. If the vehicle speed sensitive voltage E further decreases from the voltage b and becomes less than the voltage a, the vane 26
Is separated from the inner peripheral surface of the cam ring 23, and the pump 20 stops the discharge of the working fluid. In this state, the CPU advances the control operation from step 101 to step 107 and F =
After setting to 0, in step 108, the vehicle speed sensitive voltage E is applied to the electric motor 40. If the vehicle speed sensitive voltage E increases from this state, a high voltage c is temporarily applied when the voltage exceeds the voltage b as described above, and the vane 26 is brought into contact with the inner peripheral surface of the cam ring 23 to discharge the pump 20. Let it start.

According to the above-described embodiment, if the vehicle speed sensitive voltage E calculated by the electronic control unit 45 according to the vehicle speed exceeds the voltage b required to start the discharge from the pump 20,
The discharge of the working fluid from the pump 20 is reliably started regardless of changes in the operating environment such as variations in the frictional force of each product and changes in the viscosity of the working fluid due to temperature. By the way, the assist has definitely started,
There is no variation in steering feeling.

In the above embodiment, the electronic control unit 45 calculates the vehicle speed sensitive voltage E on the basis of the vehicle speed detected by the vehicle speed sensor 46, but the present invention calculates the voltage according to other running conditions such as the steering angle. It may be calculated and applied to the electric motor 40. Further, in the above-described embodiment, a very small predetermined voltage a is set, and when the vehicle speed sensitive voltage E increases from below and exceeds the relatively small predetermined voltage b, a high voltage is temporarily applied to the electric motor 40. However, the present invention may be implemented by canceling the setting of the voltage a and always applying a high voltage to the electric motor 40 whenever the vehicle speed sensitive voltage E increases and exceeds the voltage b. ..

[Brief description of drawings]

FIG. 1 is a diagram showing the overall structure of an embodiment of an electric pump type power steering apparatus according to the present invention.

FIG. 2 is a vertical sectional view of a pump used in the embodiment of FIG.

FIG. 3 is a diagram showing a portion inside a cam ring taken along the line 3-3 in FIG.

FIG. 4 is a flowchart explaining the operation of the present invention.

FIG. 5 is a diagram showing a characteristic of a vehicle speed sensitive voltage E.

FIG. 6 is a diagram showing a temporal change state of a voltage applied to an electric motor.

FIG. 7 is a diagram showing a characteristic of a rotation speed with respect to an applied voltage of an electric motor.

[Explanation of symbols]

11 ... Steering handle, 12 ... Servo valve, 15 ... Power cylinder, 15b ... Working chamber, 20 ... Pump, 21 ... Housing, 23 ... Cam ring, 25 ... Rotor, 25a ... Slit, 26 ... Vane, 30 ... Suction chamber, 32 …pump room,
34 ... Discharge chamber, 40 ... Electric motor, 45 ... Electronic control device, 45a ... Voltage control means.

Claims (1)

[Claims] 1. A power cylinder that generates an assisting force, a pump that is driven by an electric motor whose rotation speed increases in response to an increase in applied voltage to supply a working fluid to the power cylinder, and the power cylinder. A servo valve that is provided between the pumps and operates according to the manual torque applied to the steering wheel to control the supply and discharge of the working fluid to and from the working chamber of the power cylinder, and calculates the voltage according to the traveling state such as the vehicle speed. The pump includes an electronic control unit for applying the electric motor to the electric motor, and the pump rotatably supports a rotor having slidably held vanes projecting radially outward in a plurality of radially formed slits by a housing. Then
A plurality of pump chambers partitioned by the vanes are formed between the inner peripheral surface of the cam ring provided in the housing and the rotor, and the working fluid in the suction chamber is discharged by the change in the volume of the pump chamber due to the rotation of the rotor. In the electric pump type power steering device in which the pressure in the discharge chamber is introduced to the root side in each slit while being sent to the chamber, in the electronic control device, the tip of the vane is surely secured to the inner peripheral surface of the cam ring. An electric pump type power steering apparatus comprising voltage control means for increasing a voltage applied to the electric motor for a predetermined short time to a voltage at which a rotational speed of the rotor abutting on the rotor is obtained.