JP2015080983A - Electro-hydraulic power steering control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electro-hydraulic power steering control device designed to improve the fuel economy of a vehicle by maintaining a constant steering force of a steering wheel even when changes in a load applied on the steered wheel are large and stopping a hydraulic pump during straight travelling.SOLUTION: An electro-hydraulic power steering control device 10 comprises: a vehicle speed sensor 5 for detecting a speed of a vehicle; a steering angular velocity sensor 7 for detecting a steering angular velocity; a load applied on steered wheels FW for calculating a load applied on steered wheels of the vehicle; and a first ECU 3 for controlling a rotation speed Ns to drive an oil pump 2 based on values detected by the vehicle speed sensor 5, the steering angular velocity sensor 7, and the load applied on steered wheels FW, respectively. The first ECU 3 controls a flow rate at which the oil pump 2 discharges hydraulic fluid by using the calculated load applied on steered wheels FW as a parameter, based on a map B1 between a steering angular velocity ω and a hydraulic fluid flow rate corresponding to the steering angular velocity ω.

Description

  The present invention relates to an electrohydraulic power steering apparatus that assists steering of a vehicle with hydraulic pressure generated by an oil pump driven by an electric motor.

Conventionally, hydraulic power steering hydraulic pumps that assist steering of a vehicle have generated working hydraulic pressure by the driving force of the engine.
Therefore, even when the vehicle is running straight (without steering operation), the hydraulic pump of the power steering is driven while the engine is running, and the hydraulic oil circulates in the hydraulic circuit of the power steering device, and the driving load of the hydraulic pump is The engine power was wasted.
Especially during high-speed running, the engine speed increases, the flow resistance of the hydraulic oil in the hydraulic circuit increases, the engine load increases, the temperature of the hydraulic oil rises, and the cause of accelerated deterioration of the hydraulic oil Become.

In view of such a situation, an electro-hydraulic power steering device that reduces the operating force of a steering wheel by driving an oil pump with an electric motor and supplying hydraulic oil to a power cylinder has been known. .
As such a power steering apparatus, an electrohydraulic power steering control apparatus that controls an electric motor based on a vehicle speed detected by a vehicle speed sensor and a steering angular speed detected by a steering angular speed sensor is known.
Patent Document 1 discloses a similar technique.

  According to Patent Document 1, a target rotational speed setting processing unit that sets a target rotational speed of an electric motor based on a vehicle speed detected by a vehicle speed sensor and a steering angular speed detected by a steering angular speed sensor, and the rotational speed of the electric motor. A motor control unit that feedback-controls the rotational speed of the motor so that the target rotational speed becomes a target rotational speed, and a state in which the driving load of the motor exceeds a predetermined load threshold and the steering angular velocity is lower than the predetermined threshold angular velocity is the first reference time A technology is disclosed that includes an end contact protection processing unit that determines that the end contact state (steering angle limit of the steering) is reached when the determination reference time set to 1 is continued, and performs end contact protection processing.

  By doing in this way, the end contact protection processing unit monitors the drive load and the steering angular velocity of the electric motor, the drive load exceeds a predetermined threshold load, and the steering angular velocity is lower than the predetermined threshold angular velocity. If the determination reference time set for the first reference time continues, it is determined that the contact state is applied, and a protection process at the time of contact such as control to reduce the target rotational speed of the electric motor is performed. Thus, it is possible to detect the contact state, and it is possible to suppress an abnormal temperature rise of the motor drive circuit.

JP 2011-148408 A

According to Patent Document 1, in order to detect the maximum steering angle of the steering device, the driving load and the steering angular velocity of the electric motor are monitored to prevent an abnormal temperature rise of the motor drive circuit.
However, the steering force of the steering wheel varies depending on the load applied to the steering wheel, and the steering force increases in proportion to the load applied to the steering wheel.
Therefore, there is no problem if the change rate of the entire vehicle body due to the increase or decrease of the occupant is small with respect to the vehicle body weight as in a passenger car, but there is no problem when the baggage is loaded as in a commercial vehicle. When there is no change and the amount of change in the load applied to the steered wheel is large, the steering force of the steering wheel changes greatly.
Therefore, the conventional technology is not a device that takes into account fluctuations in the load load on the steered wheels. Therefore, if the amount of change in the load load on the steered wheels is large, the steering assist force of the hydraulic power steering device is sufficient. In other words, the driver has a problem that places a heavy burden on the driver.

  In view of such technical problems, the present invention maintains the steering force of the steering wheel at a constant level even when the load on the steered wheel is large, and stops the hydraulic pump when traveling straight to improve the vehicle fuel consumption. Another object is to provide an electrohydraulic power steering control device.

In order to solve such a problem, the present invention is an electrohydraulic power steering control device that assists steering of a vehicle with hydraulic pressure generated by an oil pump driven by an electric motor,
Vehicle speed detecting means for detecting the speed of the vehicle;
Steering angular velocity detection means for detecting the steering angular velocity of the vehicle;
Steering wheel load load calculating means for calculating a load applied to the steering wheel of the vehicle;
Control means for controlling the rotational speed of the oil pump based on detection values of the vehicle speed detection means, the steering angular speed detection means, and the steering wheel load calculation means,
The control means controls the hydraulic oil discharge flow rate of the oil pump based on a map of the steering angular velocity and the hydraulic oil flow rate corresponding to the steering angular velocity, using the load calculated by the steering wheel load load calculating means as a parameter. An electro-hydraulic power steering control device can be provided.

According to this invention, the hydraulic oil discharge flow rate (oil pump drive rotation speed) of the electric oil pump is controlled based on the map of the vehicle oil load and the hydraulic oil flow rate corresponding to the steering angular velocity using the steering wheel load load as a parameter. Even when the steering wheel load load, the speed, and the steering angular speed of the vehicle change, a comfortable steering operation according to each situation is possible.
Further, since the hydraulic oil protruding flow rate by the electric oil pump is changed depending on the load load on the steering wheel, the electric power consumption by the electric oil pump can be suppressed, and the alternator driven by the engine by suppressing the electric power consumption. The driving fuel consumption of the vehicle can be improved by reducing the operation (load) of the vehicle.

  According to this invention, even when a change in the load applied to the steered wheel is large, the hydraulic pressure is maintained so that the steering force of the steering wheel is kept comfortable, and the hydraulic pump is deactivated when going straight, thereby improving the fuel consumption of the vehicle. A power steering control device can be provided.

1 is a schematic configuration diagram of an electrohydraulic power steering apparatus according to an embodiment of the present invention. The map figure showing an example of the electric current amount according to the pump discharge pressure of hydraulic oil with respect to the rotation speed of an electric hydraulic motor is shown. The map figure of the braking force which generate | occur | produces with respect to brake pedal depression force is shown. The vehicle structure figure showing an example which calculates the load load of a steering wheel is shown. The map figure showing an example of the flow control of the hydraulic oil with respect to the steering angular velocity concerning embodiment of this invention is shown. The control flowchart of the control apparatus in embodiment of this invention is shown.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
However, the dimensions, materials, and relative arrangements of the components described in this embodiment are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Absent.
In the present embodiment, when the direction is indicated, the left / right front / rear and the up / down direction are displayed based on the state of being seated in the driver's seat (not shown) of the right-hand drive vehicle.

FIG. 1 is a schematic configuration diagram of an electrohydraulic power steering apparatus (hereinafter, abbreviated as electrohydraulic P / S) according to the present embodiment.
Reference numeral 10 denotes an electric hydraulic pressure P / S.
The electro-hydraulic P / S 10 includes a steering wheel 8 operated by a driver, and an integral type steering gear box that transmits the steering force of the steering wheel 8 to a steering linkage (not shown) via a steering shaft 81. (Hereinafter abbreviated as an inte gear box) 1, an electric power steering pump 2, which is an oil pump for pumping hydraulic oil to the inte gear box 1, and a steering angle θ (deg) of the steering wheel 8. ), An angular velocity sensor 7 which is a steering angular velocity detecting means for detecting a steering angular velocity ω (deg / s), and a rotational speed Ne of an engine (E / G) mounted on the vehicle. Rotational speed sensor 4 and vehicle speed detecting means for detecting vehicle speed V (km / h) Vehicle speed sensor 5, steering wheel load load calculating means 6 for detecting a load applied to the steering wheel (front wheel) of the vehicle, vehicle speed sensor 5, steering wheel load load calculating means 6, and angular velocity sensor 7. And a first ECU 3 that is a control means for performing control for calculating and outputting the command rotation speed Ns to the electric power steering pump 2.
Further, the steering wheel load load calculating means 6 of the first ECU 3 receives a signal from the brake sensor 9 that detects a pedal force Nm (a brake pedal depression amount) of the brake pedal in order to calculate a load applied to the steering wheel, which will be described later. It is designed to be entered.

The inte gear box 1 is provided with a power piston (not shown) and a gear connected to a pitman arm 11 of the steering linkage inside the inte gear box 1.
The power piston is configured to assist the steering force by rotating the gear and operating the pitman arm 11 with the high-pressure hydraulic oil from the electric power steering pump 2.

The electric power steering pump 2 performs a rotational speed control of the hydraulic pump 21 based on the output of the first ECU 3 based on the output of the hydraulic pump 21, the electric motor 22 that drives the hydraulic pump 21, and the rotational speed N of the electric motor 22. 2ECU23.
The hydraulic pump 21 generally uses a vane type pump, and has a constant displacement type hydraulic pump structure that discharges a fixed amount of hydraulic oil per rotation.
Therefore, as shown in FIG. 2, the second ECU 23 controls the current flowing through the electric motor 22 so as to change according to the discharge pressure of the hydraulic pump 21.
That is, the second ECU 23 increases the amount of current (A) when the discharge pressure is high, and decreases the amount of current (A) when the discharge pressure is low, so that the hydraulic pump is driven at the indicated rotational speed Ns from the first ECU 3. The electric current which flows through the electric motor 22 is controlled so that 21 rotates.
In the present embodiment, the first ECU 3 and the second ECU 23 are separated from each other. However, the control of the second ECU 23 can also be implemented in the first ECU 3.

As a calculation method of the steering wheel load load calculation means 6, in the case of a commercial vehicle, there are the following methods.
As a first step, the vehicle deceleration α during braking is calculated.

Deceleration α = Vehicle speed V−Δt after braking V−Δt (1)
The vehicle speed V uses the detection value of the vehicle speed sensor 5.

Next, as shown in FIG. 3, the braking force F is calculated from the relational data (map A) of the braking force F of the vehicle with respect to the brake pedal depression force (hereinafter referred to simply as the pedal effort) Nm.
Map A is a specification of vehicle braking performance, and vehicles of the same type exhibit substantially the same braking force F for the same pedaling force Nm. (Map A is stored as data in the first ECU 3)
Further, as a relational expression of the braking force F, the following expression is generally used.

Braking force F = W / g × α (2)
W: Vehicle weight α: Deceleration

Therefore, the vehicle weight W is calculated by calculating the braking force F with respect to the pedaling force Nm from the deceleration α obtained by the equation (1) and the map A in FIG. 3, and substituting each value into the equation (2). .
Next, when the vehicle weight W is calculated, based on the vehicle specification table shown in FIG. 4, the center position P and the front wheel The load loads FW and RW acting on the front wheel 101 and the rear wheel 102 are calculated from the distance FL to 101 and the distance RL from the center position P to the rear wheel 102, respectively.
From the above results, the front wheel load FW, which is the steering wheel load, is obtained based on the following equation.

Front wheel load FW = W × (WB-FL) / WB (3)
WB: Wheelbase (distance between front and rear wheels)
FL: Distance between vehicle center P and front wheel 101

The above equation (3) is stored in the first ECU 3 as data.
Although the front wheel load FW can be calculated by the above-described method, it can also be read by setting the strain gauge to the front axle or the suspension device.

A control flow of the first ECU 3 will be described with reference to FIG.
In step S1, the engine (E / G) is started in step S2, and the control flow of the first ECU 3 starts operating.
In step S3, detection of the front wheel load FW is started.
In step S4, it is determined whether the time Ts after engine start has passed the first predetermined time T1.
In order to increase the accuracy of the calculated value of the front wheel load load FW, the first predetermined time T1 is calculated by calculating the average value because the front wheel load load FW detected by engine start or vehicle movement may change. It is the set time.
If engine start time Ts <first predetermined time T1, NO is selected, and steps S3 to S4 are repeated to wait.
In the present embodiment, the first predetermined time T1 is set to 10 minutes. However, the first predetermined time T1 can be increased or decreased depending on the operating state of the vehicle and the engine specifications.

In step S4, if time Ts after engine start ≧ first predetermined time T1, YES is selected and the process proceeds to step S5.
In step S5, the front wheel load load FW is calculated.
Since the calculation method of the front wheel load FW is as described above, the description is omitted.

Proceeding to step S6, the hydraulic oil flow control (rotational speed control) of the electric power steering pump 2 along the magnitude of the front wheel load load FW is performed so that energy-saving and comfortable operation of the steering wheel 8 can be performed. Select a map.
Since the hydraulic pump 21 is a constant displacement vane pump in which the amount of hydraulic oil discharged in one rotation is constant as described above, the hydraulic pump 21 is controlled by controlling the rotational speed of the hydraulic pump 21. It is like that.
FIG. 5 is a map diagram illustrating an example of hydraulic oil flow rate control with respect to the steering angular velocity ω (deg / s).
The maps are classified according to the magnitude of the front wheel load FW, map B1, map B2, map B3,. (Parameter)
Each map is created based on hydraulic fluid flow data corresponding to the steering angular velocity ω by changing the steering angular velocity ω (deg / s) and the vehicle speed V (km / h) with a test device for each front wheel load. It is a thing.

In the map B1, the map B2, and the map B3, the larger the front wheel load FW, the greater the hydraulic fluid flow rate L / min is discharged.
Further, the plurality of maps are provided depending on the magnitude of the front wheel load load FW when the front wheel load load FW is large, the frictional force between the tire and the road surface increases, and the front wheel 101 which is a steered wheel is steered. In addition, since the amount of hydraulic oil to the hydraulic power S / T1 increases due to elastic deformation of the steering linkage, a plurality of maps are provided to enable comfortable operation of the steering wheel 8.
In this embodiment, the classification is made into three categories, but it may be increased or decreased depending on the structure of the steering linkage or the electric power steering pump 2.

The map B1, the map B2, and the map B3 are respectively based on the steering angular velocity ω (deg / s) on the horizontal axis and the flow rate Q (L / min) on the vertical axis as the vehicle speed increases from a low vehicle speed V to a high vehicle speed. Control is performed so that the flow rate Q (L / min) decreases and the flow rate Q (L / min) increases with the steering angular velocity ω (deg / s).
Then, the flow rate Q (L / min) is controlled to be smaller as the vehicle speed V is changed from the lower vehicle speed V to the higher vehicle speed V, so that the steering force of the steering wheel 8 is increased and the vehicle speed is high. The steering amount is controlled so as not to increase.
Further, when the steering angular velocity ω (deg / s) is high, the flow rate of the hydraulic oil is increased to prevent a shortage of hydraulic oil supply to the power cylinder, and the steering force of the steering wheel 8 can be ensured. Control to assist.

In step S <b> 7, the vehicle speed V (km / h), which is the driving state of the vehicle, and the steering angular velocity ω (deg / s) of the steering wheel 8 are read from the output values of the vehicle speed sensor 5 and the steering angular velocity sensor 7.
Then, the first ECU 3 extracts the hydraulic oil discharge amount Q (L / min) necessary for comfortable steering from the steering angular speed ω and the vehicle speed V based on the map selected by the front wheel load FW, and extracts The drive rotational speed Ns of the electric power steering pump 2 is calculated so as to be the discharge amount Q (L / min), and is output to the second ECU 23 as a control signal.

In step S <b> 8, the second ECU 23 integrally assembled with the electric motor 22 drives the hydraulic pump 21 based on the rotation speed control signal from the first ECU 3 and executes steering assist for the hydraulic power S / T <b> 1. .
In step S9, it is determined whether the steering angle θ (deg) = 0.
This is detected by an angle sensor 71 that detects the steering angle θ (deg) of the steering wheel 8 to determine whether the vehicle is in a straight traveling state or is being steered (a state in which the steering angle is maintained). .
If the steering angle θ (deg) ≠ 0, it is determined that steering is in progress, NO is selected, and the process returns to step S8.
On the other hand, if the steering angle θ (deg) = 0, if it is determined that the vehicle is traveling straight, YES is selected and the process proceeds to step S10.
In step S10, the electric power steering pump 2 is stopped and the power consumption of the electric motor 22 is stopped, thereby suppressing the operation of the alternator driven by the engine. Is intended to be obtained.

It progresses to step S11 and it is judged whether vehicle speed V (km / h) = 0.
This determines whether the vehicle is in a stopped state or a traveling state.
When the vehicle speed V (km / h) ≠ 0, the vehicle is determined to be in a traveling state, NO is selected, the process returns to step S10, and the electric power steering pump 2 is continuously stopped.
On the other hand, if the vehicle speed V (km / h) = 0, the vehicle determines that the engine is idling and is stopped, selects YES, and proceeds to step S12.
The detection of idling is determined by the rotational speed Ne detected by the engine rotational speed sensor 4.

In step S12, engine (E / G) idling time T> second predetermined time T2 is determined.
This determines whether or not the vehicle is temporarily stopped by a signal or the like.
That is, when the engine (E / G) idling time T <second predetermined time T2, it is determined that the vehicle is temporarily stopped by a signal or the like, NO is selected, and the process returns to step S10 and the electric power steering pump 2 is stopped. The
In the present embodiment, T2 is performed in 3 minutes, but may be changed as appropriate according to traffic conditions and environment.
On the other hand, if the engine idling time T is longer than the predetermined time T2, YES is selected and the process proceeds to step S13.

In step S13, engine (E / G) idling time T ≧ third predetermined time T3 is determined.
In the third predetermined time T3, it is determined whether or not the vehicle is being used during idling, that is, whether or not the vehicle is performing a loading / unloading operation or the like.
If the engine idling time T ≧ the third predetermined time T3, the vehicle is determined to be loading / unloading work, YES is selected, and the process returns to step S5.
Since the loading and unloading work involves fluctuations in the front wheel load load WF, which is a steered wheel, the process returns to step S5 to recalculate the front wheel load load WF in order to obtain a comfortable steering feeling.
In the present embodiment, the third predetermined time T3 is set to 30 minutes or more. However, the third predetermined time T3 may be appropriately changed according to the work form such as the vehicle body form and the state of the luggage.
On the other hand, if the engine idling time T <the third predetermined time T3, NO is selected and the process proceeds to step S14.

In step S14, it is determined whether the engine is stopped or operating.
When the engine is in operation (idling state), the process returns to step S13 and the idling state is continued.
On the other hand, when the engine is operated to stop the engine, YES is selected and the process proceeds to step S15.

In this way, the speed of the vehicle is controlled by controlling the drive rotation speed Ns (hydraulic oil discharge flow rate) of the electric power steering pump 2 based on the vehicle speed V, the steering angular velocity ω, and the steering wheel load load FW. Even when V, the steering angular velocity ω, and the steering wheel load FW change, a comfortable steering wheel operation according to each situation becomes possible.
In addition, by using the electric power steering pump 2, when the steering is not performed, the driving of the electric power steering pump 2 is stopped, and the operation (load) of the alternator driven by the engine is reduced by suppressing power consumption. Thus, it is possible to improve the driving fuel consumption of the vehicle.

  The hydraulic pressure generated by an oil pump driven by an electric motor can be used in an electrohydraulic power steering device that assists in steering the vehicle.

1 INTE GEAR BOX (Integral type steering gear box)
2 Electric power steering pump 3 First ECU (control means)
5 Vehicle speed sensor (vehicle speed detection means)
6 Steering wheel load load calculating means 7 Steering angular velocity sensor (steering angular velocity detecting means)
8 Steering wheel 9 Brake sensor 9
DESCRIPTION OF SYMBOLS 10 Electric hydraulic power steering apparatus 11 Pitman arm 21 Hydraulic pump 22 Electric motor 23 2ECU
F Braking force W Vehicle weight WF Front wheel load load (steering wheel load load)

Claims (1)

An electro-hydraulic power steering control device that assists steering of a vehicle with hydraulic pressure generated by an oil pump driven by an electric motor,
Vehicle speed detecting means for detecting the speed of the vehicle;
Steering angular velocity detection means for detecting the steering angular velocity of the vehicle;
Steering wheel load load calculating means for calculating a load applied to the steering wheel of the vehicle;
Control means for controlling the rotational speed of the oil pump based on detection values of the vehicle speed detection means, the steering angular speed detection means, and the steering wheel load calculation means,
The control means controls the hydraulic oil discharge flow rate of the oil pump based on a map of the steering angular velocity and the hydraulic oil flow rate corresponding to the steering angular velocity, using the load calculated by the steering wheel load load calculating means as a parameter. An electro-hydraulic power steering control device.

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