JPH08207805A - Power steering device - Google Patents

Abstract

PURPOSE: To provide a power steering device, inhibited from the effect of the fluctuation and variation of a motor current due to other than steering; raising voltage, to be applied to an electric motor; and degree from the beginning of the operation of a steering wheel, and having a small slippage time from a standby rotation mode to be switched to an assistant rotation mode, and a good steering sense. CONSTITUTION: In this power steering device, auxiliary steering is made while using the generation source, for operating oil pressure, of a hydraulic pump 5 driven by an electric motor 4 rotated by a standby rotation mode and an assistant rotation mode. This device is provided with a motor current detection circuit 3 for detecting an electric current flowing in the electric motor 4, a parameter operating means 10 for operating parameter in order to control the switch of a mode based on a detected motor electric current value, a judging means 9a for judging the compared size between this operated parameter and a given value, and a motor control means 8 and 2 for controlling the switch of a mode in accordance with the judged result by the judging means 9a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a power steering system for assisting steering by using a hydraulic pump driven by an electric motor as a source of operating hydraulic pressure.

[0002]

2. Description of the Related Art FIG. 9 is a block diagram showing a main configuration of an example of a power steering apparatus that assists steering with a hydraulic pump driven by an electric motor as a source of operating hydraulic pressure. In this power steering device, a motor drive circuit 2 applies a voltage to an electric motor 4 to drive the electric motor 4 in accordance with a target value of an applied voltage instructed by the control unit 1, and the electric motor 4 drives a hydraulic pump 5 to generate an operating hydraulic pressure. generate.

When the steering wheel 7 is operated and the gear device (not shown) including the pinion gear 6c provided at the lower end of the steering wheel shaft is operated, the control valve 6 is connected to the pipelines 6a and 6b leading to the power cylinder. Controls the pressure of hydraulic oil that is pumped. As a result, the power cylinder operates to generate a steering assist force in the operation direction of the steered wheels 7 according to the operation amount. A motor current detection circuit 3 that detects a current flowing through the electric motor 4 is provided between the motor drive circuit 2 and the electric motor 4, and the motor current detection signal is input to the control unit 1. The control unit 1 controls the voltage applied to the electric motor 4 based on the motor current detection signal.

In the conventional power steering apparatus having such a configuration, the control unit 1 reduces energy consumption when the steering wheels 7 are not operated and no steering assist force is required (the electric current flowing through the electric motor 4 is small). In order to suppress it, as shown in FIG. 11, the motor drive mode is set to the standby rotation mode (low voltage, low rotation speed) to reduce the output of the electric motor 4. Then, the steering wheel 7 is operated, the control valve 6 is operated, the operating oil pressure is increased, the load is increased, the current flowing through the electric motor 4 is increased, and the motor current detection signal of the motor current detection circuit 3 is a predetermined value. When reaching (for example, 12 A), the control unit 1 switches the motor drive mode to the assist rotation mode (high voltage, high rotation speed) to increase the output of the electric motor 4. The standby rotation mode is a motor drive mode that produces a relatively low motor output as compared with the assist rotation mode.

[0005]

The conventional power steering system has the electric motor 4 when the steering wheel 7 is not operated.
The current flowing through the device varies depending on the device at the time of manufacture, and also changes due to the viscosity of the hydraulic oil changing with temperature.Therefore, the motor current for switching from the standby rotation mode to the assist rotation mode The threshold value is set high (e.g., 12A equivalent) as described above.

Therefore, in the conventional power steering apparatus, as shown in FIG. 10 (a), the steering wheel 7 is started to be operated, the control valve 6 is actuated, the hydraulic pressure is increased, and the load is increased. As shown in FIG. 10B, the current flowing through the electric motor 4 increases, and the motor current detection signal of the motor current detection circuit 3 reaches 12 A, and FIG.
As shown in Fig. 10, a time lag (Fig. 10 (e)) occurs until the voltage applied to the electric motor 4 is raised by one step.

Therefore, since the steering assist force is small, the time (deviation) from when the steering wheel 7 starts to be operated until the voltage applied to the electric motor 4 is raised by one step, as shown in the circle in FIG. The steering torque became large and there was a catch at the start of steering. The present invention has been made in view of the above-described circumstances, and is not affected by variations and fluctuations in the motor current caused by factors other than steering, and the voltage applied to the electric motor is raised by one step after the steering wheel is operated. It is an object of the present invention to provide a power steering device that has a small time lag before being turned on, that is, a time lag before switching from the standby rotation mode to the assist rotation mode and has a good steering feel.

[0008]

A power steering system according to a first aspect of the present invention assists steering by using a hydraulic pump driven by an electric motor rotated in a standby rotation mode and an assist rotation mode as a source of operating hydraulic pressure. In the power steering apparatus for performing, a motor current detection circuit that detects a current flowing through the electric motor, and a parameter that calculates a parameter for controlling the mode switching based on a motor current value detected by the motor current detection circuit. And a motor control means for performing the mode switching control according to the determination result of the determination means, the determination means for determining the magnitude of the parameter calculated by the parameter calculation means and the predetermined value. Characterize.

In the power steering apparatus according to the second aspect of the present invention, the parameter calculation means is a differentiation calculation means for differentiating the motor current value detected by the motor current detection circuit.

In the power steering apparatus according to the third aspect of the present invention, the parameter computing means is a computing means for averaging or integrating a motor current value detected by the motor current detection circuit for a predetermined time, the motor current value and the computing means. Has subtraction means for obtaining a difference from an average or an integrated value.

In the power steering apparatus according to the fourth aspect of the present invention, the parameter calculating means is a differential calculating means for differentiating the motor current value detected by the motor current detecting circuit,
The differential operation means includes an adding means for adding the differentiated value and the motor current value.

In the power steering apparatus according to the fifth aspect of the present invention, the parameter calculation means includes calculation means for averaging or integrating motor current values detected by the motor current detection circuit for a predetermined time, motor current values and the calculation means. The present invention is characterized by having subtraction means for obtaining a difference from an average or integrated value, and addition means for adding the difference obtained by the subtraction means and the motor current value.

A power steering apparatus according to a sixth aspect of the present invention is a power steering apparatus for assisting steering with a hydraulic pump driven by an electric motor rotated in a standby rotation mode and an assist rotation mode as a source of operating hydraulic pressure. A motor current detection circuit for detecting a current flowing through the motor, a parameter calculation means for calculating a parameter for controlling the mode switching based on the motor current value detected by the motor current detection circuit, and the parameter calculation means. Parameter determining means for determining the magnitude of the calculated parameter and the predetermined value, motor current determining means for determining the magnitude of the motor current value and the predetermined current value, each of the parameter determining means and the motor current determining means Logic means for calculating the logic of the judgment result and depending on the calculation result of the logic means Characterized in that it comprises a motor control means for switching control of said mode.

In the power steering apparatus according to the seventh aspect of the present invention, the parameter calculation means is a differentiation calculation means for differentiating the motor current value detected by the motor current detection circuit.

In the power steering apparatus according to the eighth aspect of the present invention, the parameter computing means is a computing means for averaging or integrating the motor current value detected by the motor current detection circuit for a predetermined time, the motor current value and the computing means. Has subtraction means for obtaining a difference from an average or an integrated value.

[0016]

In the power steering apparatus according to the first aspect of the present invention, the parameter calculating means controls the switching between the standby rotation mode and the assist rotation mode based on the motor current value detected by the motor current detection circuit. And the determination means determines the magnitude of this parameter and the predetermined value. Then, the motor control means performs mode switching control according to the determination result of the determination means.

In the power steering apparatus according to the second aspect of the present invention, the differential operation means differentiates the motor current value detected by the motor current detection circuit and controls the mode switching based on this differential value, so that the steering wheel is operated. When the current flowing through the electric motor starts to increase for the first time, the standby rotation mode is immediately switched to the assist rotation mode, and the time lag until the mode switching is reduced.

In the power steering apparatus according to the third aspect of the present invention, the calculating means averages or integrates the motor current values detected by the motor current detection circuit within a predetermined time, and the subtracting means calculates the motor current value and the averaged or integrated value. Find the difference between and. Since the mode switching is controlled based on the obtained difference, when the steering wheel begins to be operated and the current flowing through the electric motor starts to increase, the mode is switched from the standby rotation mode to the assist rotation mode immediately. The time lag is reduced. Further, even if the motor current value fluctuates due to the viscosity of the hydraulic oil changing with temperature, the difference between the motor current value and the average value or integral value of the motor current value per predetermined time is taken. The fluctuation of the current value due to the temperature of the hydraulic oil can be eliminated.

In the power steering apparatus according to the fourth aspect of the present invention, the differential operation means differentiates the motor current value detected by the motor current detection circuit, and the adding means adds the differentiated value and the motor current value. Since the mode switching is controlled based on this added value, when the steering wheel starts to be operated and the motor current starts to increase, the standby rotation mode is immediately switched to the assist rotation mode, and the time until the mode is switched is changed. Deviation is reduced. In addition, the operation of the steering wheel is gentle and the rate of increase of the motor current value (differentiated value)
Even when is small, mode switching can be controlled at least by the motor current value.

In the power steering apparatus according to the fifth aspect of the invention, the average calculating means or the integral calculating means averages or integrates the motor current values detected by the motor current detecting circuit in a predetermined time, and the subtracting means calculates the motor current value and the motor current value. The addition means calculates the difference from the average or integrated value, and adds the difference and the motor current value. Since the mode switching is controlled based on this added value, when the steering wheel starts to be operated and the motor current starts to increase, the standby rotation mode is immediately switched to the assist rotation mode, and the time until the mode is switched is changed. Deviation is reduced. Further, even when the operation of the steering wheel is gentle and the increase rate (difference) of the motor current value is small, the mode switching can be controlled at least by the motor current value.

In the power steering apparatus according to the sixth aspect of the present invention, the parameter calculation means calculates the parameter for controlling the mode switching based on the motor current value detected by the motor current detection circuit, and the parameter determination means
The magnitude of the calculated parameter and the predetermined value is determined.
Further, the motor current determination means determines the magnitude of the motor current value and the predetermined current value. Then, the logic means calculates the logic of each judgment result of the parameter judgment means and the motor current judgment means, and performs mode switching control according to the calculation result of this logic means.

In the power steering apparatus according to the seventh aspect of the present invention, the differential operation means differentiates the motor current value detected by the motor current detection circuit, and the parameter determination means determines the magnitude of the differentiated value and the predetermined value. . Further, the motor current determination means determines the magnitude of the motor current value and the predetermined current value. Then, the logic means calculates the logic of each judgment result of the parameter judgment means and the motor current judgment means, and performs mode switching control according to the calculation result of this logic means.

In the power steering apparatus according to the eighth aspect of the present invention, the average calculating means or the integral calculating means averages or integrates the motor current values detected by the motor current detecting circuit in a predetermined time, and the subtracting means calculates the motor current value and the motor current value. The parameter determining means determines the difference between the average or the integrated value and determines the magnitude of this difference and the predetermined value. Further, the motor current determination means determines the magnitude of the motor current value and the predetermined current value.
Then, the logic means calculates the logic of each judgment result of the parameter judgment means and the motor current judgment means, and performs mode switching control according to the calculation result of this logic means.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the power steering device according to the present invention will be described below with reference to the drawings showing the same. FIG. 1 is a block diagram showing a main part configuration of an embodiment of a power steering device according to the first and second inventions. In this power steering device, the motor drive circuit 2 applies a voltage to the electric motor 4 to rotate the electric motor 4 according to the applied voltage instructed by the motor applied voltage instructing unit 8 of the control unit 1a, and the electric motor 4 drives the hydraulic pump 5. Drive to generate hydraulic pressure.

When the steering wheel 7 is operated and the gear device (not shown) including the pinion gear 6c provided at the lower end of the steering wheel shaft is operated, the control valve 6 is connected to the pipelines 6a and 6b leading to the power cylinder. Controls the pressure of hydraulic oil that is pumped. As a result, the power cylinder operates to generate a steering assist force in the operation direction of the steered wheels 7 according to the operation amount.

A motor current detection circuit 3 for detecting a current flowing through the electric motor 4 is provided between the motor drive circuit 2 and the electric motor 4, and the motor current detection signal is sent to the differential operation section 10 of the control section 1a. Is entered. The differential operation unit 10 differentiates the motor current detection signal, and the differentiated value (parameter operation value) is input to the determination unit 9a included in the control unit 1a. The determination unit 9a determines the magnitude of this differentiated value with respect to a predetermined value, sends the determination result to the motor applied voltage instruction unit 8, and the motor applied voltage instruction unit 8
According to this determination result, the applied voltage to the electric motor 4 is instructed.

The operation of the power steering device having such a structure will be described below. The motor applied voltage instruction unit 8 included in the control unit 1a is shown in FIG. 2 in order to suppress energy consumption when the steering wheels 7 are not operated and no steering assist force is required (the electric current flowing through the electric motor 4 is small). As described above, the motor applied voltage instruction signal that lowers the voltage applied to the electric motor 4 by one step is output to decrease the output of the electric motor 4 (standby rotation mode). The differential operation unit 10 always differentiates the motor current detection signal output by the motor current detection circuit 3 and inputs the differentiated value to the determination unit 9a. The determination unit 9a determines the magnitude of this differentiated value with respect to a predetermined value, and sends the determination result to the motor applied voltage instruction unit 8.

The steering wheel 7 is operated to operate the control valve 6
Is activated, the hydraulic pressure rises, the load increases, the current flowing through the electric motor 4 increases, and the motor current detection signal output from the motor current detection circuit 3 increases, the differential operation unit 10 detects the motor current. The value obtained by differentiating the signal becomes large. When the differentiated value (parameter calculation value) becomes larger than the predetermined value P1, the determination unit 9a sends the determination result to the motor applied voltage instruction unit 8, and the motor applied voltage instruction unit 8
2 outputs a motor applied voltage instruction signal that raises the voltage applied to the electric motor 4 by one step according to the determination result. According to the motor applied voltage instruction signal, the motor drive circuit 2 raises the applied voltage by one stage to drive the electric motor 4 to rotate and increase its output (assist rotation mode).

On the other hand, when the operation of the steering wheel 7 is stopped,
When the operating oil pressure decreases, the load decreases, the current flowing through the electric motor 4 decreases, and the motor current detection signal output by the motor current detection circuit 3 decreases, the differentiation calculation unit 10 differentiates the motor current detection signal. The value becomes smaller (it becomes a negative value). When the differentiated value (parameter calculation value) becomes smaller than the predetermined value P2, the determination section 9a sends the determination result to the motor applied voltage instructing section 8, and the motor applied voltage instructing section 8 uses the determination result as shown in FIG. As shown in, a motor applied voltage instruction signal that lowers the voltage applied to the electric motor 4 by one step is output. According to the motor applied voltage instruction signal, the motor drive circuit 2 lowers the applied voltage by one stage to drive the electric motor 4 to rotate, and reduces the output thereof (standby rotation mode). In this power steering device, as soon as the current flowing through the electric motor begins to increase, the voltage applied to the electric motor is immediately raised by one step, and the time from when the steering wheel starts to be operated to when the standby rotation mode is switched to the assist rotation mode is increased. The gap becomes smaller.

FIG. 3 is a block diagram showing the configuration of the essential parts of one embodiment of the power steering apparatus according to the first and third inventions. In this power steering device, the motor drive circuit 2 applies a voltage to the electric motor 4 to drive the electric motor 4 according to the applied voltage instructed by the motor applied voltage instruction unit 8 included in the control unit 1b, and the electric motor 4 drives the hydraulic pump 5. To generate operating hydraulic pressure.

A motor current detection circuit 3 for detecting a current flowing through the electric motor 4 is provided between the motor drive circuit 2 and the electric motor 4, and the motor current detection signal is a motor current detection signal included in the control section 1b. Is input to the integration calculation unit 11 for integrating for a predetermined time. Integral calculation unit 11
The motor current detection signal is integrated for a predetermined integration time, and the integrated value is obtained as the difference from the motor current detection signal at the subtraction point 12, and the obtained difference (parameter calculation value) is It is input to the determination unit 9b included in the control unit 1b. The determination unit 9b determines the magnitude of the obtained difference from a predetermined value, sends the determination result to the motor applied voltage instruction unit 8, and the motor applied voltage instruction unit 8 follows the determination result. Indicates the applied voltage to. The other main structure is the same as the main structure of the power steering device according to the first and second aspects of the invention described above, and thus the description thereof is omitted.

The operation of the power steering device having such a structure will be described below. The motor applied voltage instruction unit 8 included in the control unit 1b is shown in FIG. 2 in order to suppress energy consumption when the steering wheel 7 is not operated and no steering assist force is required (the electric current flowing through the electric motor 4 is small). As described above, the motor applied voltage instruction signal that lowers the voltage applied to the electric motor 4 by one step is output to decrease the output of the electric motor 4 (standby rotation mode). The integration calculation unit 11 always integrates the motor current detection signal output by the motor current detection circuit 3, and the integrated value is obtained as a difference from the motor current detection signal at the subtraction point 12. The determined difference is input to the determination unit 9b, which determines the calculated difference of
The magnitude of the predetermined value is determined and the determination result is sent to the motor applied voltage instruction unit 8.

The steering wheel 7 is operated to control the control valve 6.
Is activated, the hydraulic pressure rises, the load increases, the current flowing through the electric motor 4 increases, and the motor current detection signal output by the motor current detection circuit 3 increases, the integral calculation unit 11 detects the motor current. The value obtained by integrating the signal becomes large. The subtraction point 12 obtains a difference between the motor current detection signal and a value obtained by integrating the motor current detection signal, and the difference is determined by the determination unit 9b.
I am sending it to. When the difference (parameter calculation value) becomes larger than the predetermined value P1, the determination unit 9b sends the determination result to the motor applied voltage instruction unit 8. Motor applied voltage instruction unit 8
2 outputs a motor applied voltage instruction signal that raises the voltage applied to the electric motor 4 by one step according to the determination result. According to the motor applied voltage instruction signal, the motor drive circuit 2 raises the applied voltage by one stage to drive the electric motor 4 to rotate and increase its output (assist rotation mode).

On the other hand, when the operation of the steering wheel 7 is stopped,
When the operating oil pressure decreases, the load decreases, the current flowing through the electric motor 4 decreases, and the motor current detection signal output by the motor current detection circuit 3 decreases, the integral calculation unit 11 outputs the motor current detection signal for a predetermined time. The value integrated per hit is also small. The subtraction point 12 finds the difference between the motor current detection signal and the value obtained by integrating the motor current detection signal, and sends this difference to the determination unit 9b. When the difference (parameter calculation value) becomes smaller than the predetermined value P2, the determination unit 9b sends the determination result to the motor applied voltage instructing unit 8, and the motor applied voltage instructing unit 8 shows the determination result in FIG. As described above, the motor applied voltage instruction signal for lowering the voltage applied to the electric motor 4 by one step is output. According to the motor applied voltage instruction signal, the motor drive circuit 2 lowers the applied voltage by one stage to drive the electric motor 4 to rotate, and reduces the output thereof (standby rotation mode).

In this power steering device, since the difference between the motor current value and the integral value of the motor current value per predetermined time is taken, it means that the degree of change of the motor current value is observed, and the electric motor As soon as the flowing current starts to increase, the voltage applied to the electric motor is raised by one step,
The time lag between when the steering wheel starts to be operated and when the standby rotation mode is switched to the assist rotation mode becomes small. Even if the motor current value fluctuates because the viscosity of the hydraulic oil changes with temperature, the difference between the motor current value and the integral value of the motor current value per predetermined time is taken. , The fluctuation due to the temperature of the hydraulic oil can be eliminated. It should be noted that the same effect can be obtained by replacing the above-described integral calculator 11 with an average calculator that averages the motor current detection signals in a predetermined time.

FIG. 4 is a block diagram showing the construction of the essential parts of one embodiment of the power steering apparatus according to the first and fourth inventions. In this power steering device, the motor drive circuit 2 applies a voltage to the electric motor 4 to drive the electric motor 4 according to the applied voltage instructed by the motor applied voltage instruction unit 8 included in the control unit 1c, and the electric motor 4 drives the hydraulic pump 5. To generate operating hydraulic pressure.

A motor current detection circuit 3 for detecting a current flowing through the electric motor 4 is provided between the motor drive circuit 2 and the electric motor 4, and the motor current detection signal is sent to the differential operation section 10 of the control section 1c. Is entered. The differential operation unit 10 differentiates the motor current detection signal, and the differentiated value is added to the motor current detection signal at the addition point 13, and the added value (parameter operation value) is the control unit 1c. Is input to the determination unit 9c included in. Judgment unit 9c
Determines the magnitude of this added value with respect to a predetermined value, and sends the determination result to the motor applied voltage instructing unit 8, and the motor applied voltage instructing unit 8 applies the voltage to the electric motor 4 according to this determination result. Indicate voltage. The other main structure is the same as the main structure of the power steering device according to the first and second aspects of the invention described above, and thus the description thereof is omitted.

The operation of the power steering device having such a configuration will be described below. The motor applied voltage instruction unit 8 included in the control unit 1c is shown in FIG. 2 in order to suppress energy consumption when the steering wheel 7 is not operated and no steering assist force is required (the electric current flowing through the electric motor 4 is small). As described above, the motor applied voltage instruction signal that lowers the voltage applied to the electric motor 4 by one step is output to decrease the output of the electric motor 4 (standby rotation mode). The differential operation unit 10 always differentiates the motor current detection signal output from the motor current detection circuit 3, and the differentiated value is added to the motor current detection signal at the addition point 13. The added value is input to the determination unit 9c, and the determination unit 9c outputs the added value of
The magnitude of the predetermined value is determined and the determination result is sent to the motor applied voltage instruction unit 8.

The steering wheel 7 is operated to control the control valve 6.
Is activated, the hydraulic pressure rises, the load increases, the current flowing through the electric motor 4 increases, and the motor current detection signal output from the motor current detection circuit 3 increases, the differential operation unit 10 detects the motor current. The value obtained by differentiating the signal becomes large. At the addition point 13, a value obtained by differentiating the motor current detection signal is added to the motor current detection signal, and the added value is sent to the determination unit 9c. When the added value (parameter calculation value) becomes larger than the predetermined value P1, the determination unit 9c sends the determination result to the motor applied voltage instructing unit 8, and the motor applied voltage instructing unit 8 uses the determination result as shown in FIG. As shown in, a motor applied voltage instruction signal that raises the voltage applied to the electric motor 4 by one step is output. Motor drive circuit 2
In accordance with this motor applied voltage instruction signal, the applied voltage is raised by one step to drive the electric motor 4 to rotate and the output thereof is increased (assist rotation mode).

On the other hand, when the operation of the steering wheel 7 is stopped,
When the operating oil pressure decreases, the load decreases, the current flowing through the electric motor 4 decreases, and the motor current detection signal output by the motor current detection circuit 3 decreases, the differentiation calculation unit 10 differentiates the motor current detection signal. The value becomes smaller (it becomes a negative value). At the addition point 13, a value obtained by differentiating the motor current detection signal is added to the motor current detection signal, and the added value is sent to the determination unit 9c. When the added value (parameter calculation value) becomes smaller than the predetermined value P2, the determination unit 9c sends the determination result to the motor applied voltage instruction unit 8,
Based on this determination result, the motor applied voltage instruction unit 8 is
As shown in, a motor applied voltage instruction signal that lowers the voltage applied to the electric motor 4 by one step is output. According to the motor applied voltage instruction signal, the motor drive circuit 2 lowers the applied voltage by one stage to drive the electric motor 4 to rotate, and reduces the output thereof (standby rotation mode).

In this power steering system, when the current flowing through the electric motor begins to increase, the voltage applied to the electric motor is immediately raised by one step until the steering wheel starts to be operated until the standby rotation mode is switched to the assist rotation mode. The time difference between the two becomes smaller. Further, even when the operation of the steering wheel is gentle and the increase rate (differentiated value) of the motor current value is small, the voltage applied to the electric motor can be controlled at least by the motor current value.

FIG. 5 is a block diagram showing the essential structure of one embodiment of the power steering apparatus according to the first and fifth inventions. In this power steering device, the motor drive circuit 2 applies a voltage to the electric motor 4 to drive the electric motor 4 according to the applied voltage instructed by the motor applied voltage instruction unit 8 included in the control unit 1d, and the electric motor 4 drives the hydraulic pump 5. To generate operating hydraulic pressure.

A motor current detection circuit 3 for detecting a current flowing through the electric motor 4 is provided between the motor drive circuit 2 and the electric motor 4, and the motor current detection signal is a motor current detection signal included in the control section 1d. Is input to the integration calculation unit 11 for integrating for a predetermined time. Integral calculation unit 11
Of the motor current detection signal is integrated for a predetermined integration time, and a difference between the integrated value and the motor current detection signal is obtained at the subtraction point 16. The obtained difference is added to the motor current detection signal at the addition point 15, and the added value (parameter calculation value) is input to the determination unit 9d included in the control unit 1d. The determination unit 9d determines the magnitude of the added value with respect to the predetermined value, sends the determination result to the motor applied voltage instruction unit 8, and the motor applied voltage instruction unit 8
According to this determination result, the applied voltage to the electric motor 4 is instructed. Other configurations of the main parts are the same as those of the first and second parts described above.
Since the configuration is the same as the main part of the power steering device according to the invention, the description thereof will be omitted.

The operation of the power steering device having such a structure will be described below. The motor applied voltage instruction unit 8 included in the control unit 1d is shown in FIG. 2 in order to suppress energy consumption when the steering wheel 7 is not operated and no steering assist force is required (the electric current flowing through the electric motor 4 is small). As described above, the motor applied voltage instruction signal that lowers the voltage applied to the electric motor 4 by one step is output to decrease the output of the electric motor 4 (standby rotation mode). The integral calculator 11 always integrates the motor current detection signal output by the motor current detection circuit 3, and the integrated value is input to the subtraction point 16. At the subtraction point 16, the difference between the motor current detection signal and its integrated value is obtained. The obtained difference is added to the motor current detection signal at the addition point 15. The added value (parameter calculation value) is input to the determination unit 9d, and the determination unit 9d determines the magnitude of the added value with respect to a predetermined value, and the determination result is sent to the motor applied voltage instruction unit 8. to be sending.

When the steering wheel 7 is operated, the control valve 6
Is activated, the hydraulic pressure rises, the load increases, the current flowing through the electric motor 4 increases, and the motor current detection signal output by the motor current detection circuit 3 increases, the integral calculation unit 11 detects the motor current. The value obtained by integrating the signal becomes large. The integrated value is input to the subtraction point 16 and the subtraction point 1
In 6, the difference between the motor current detection signal and its integrated value is obtained. The obtained difference is added to the motor current detection signal at the addition point 15, and the addition point 15 sends the added value to the determination unit 9d. Judgment unit 9d
Is the added value (parameter calculation value) is a predetermined value P1.
When it becomes larger, the determination result is sent to the motor applied voltage instructing unit 8, and the motor applied voltage instructing unit 8 uses the determination result to increase the voltage applied to the electric motor 4 by one step, as shown in FIG. Output an instruction signal. According to the motor applied voltage instruction signal, the motor drive circuit 2 raises the applied voltage by one stage to drive the electric motor 4 to rotate and increase its output (assist rotation mode).

On the other hand, when the operation of the steering wheel 7 is stopped,
When the operating oil pressure decreases, the load decreases, the current flowing through the electric motor 4 decreases, and the motor current detection signal output by the motor current detection circuit 3 decreases, the integral calculation unit 11 outputs the motor current detection signal to a predetermined value. The value integrated in the integration time becomes smaller. The integrated value is input to the subtraction point 16, and at the subtraction point 16, the difference between the motor current detection signal and the integrated value is obtained. This calculated difference is the addition point 15
Is added to the motor current detection signal at
Sends the added value to the determination unit 9d. When the added value (parameter calculation value) becomes smaller than the predetermined value P2, the determination unit 9d sends the determination result to the motor applied voltage instructing unit 8, and the motor applied voltage instructing unit 8 uses the determination result as shown in FIG. As shown in, a motor applied voltage instruction signal that lowers the voltage applied to the electric motor 4 by one step is output. According to the motor applied voltage instruction signal, the motor drive circuit 2 lowers the applied voltage by one stage to drive the electric motor 4 to rotate, and reduces the output thereof (standby rotation mode).

In this power steering system, when the current flowing through the electric motor starts to increase, the voltage applied to the electric motor is immediately raised by one step until the steering wheel starts to be operated until the standby rotation mode is switched to the assist rotation mode. The time difference between the two becomes smaller. Even if the motor current value fluctuates because the viscosity of the hydraulic oil changes with temperature, the difference between the motor current value and the integral value of the motor current value per predetermined time is taken. , The fluctuation due to the temperature of the hydraulic oil can be eliminated. Also,
Even when the operation of the steering wheel is gentle and the increase rate (integrated value) of the motor current value is small, the voltage applied to the electric motor can be controlled at least by the motor current value. It should be noted that the same effect can be obtained by replacing the above-described integral calculator 11 with an average calculator that averages the motor current detection signals in a predetermined time.

FIG. 6 is a block diagram showing the construction of the essential parts of one embodiment of the power steering apparatus according to the sixth and seventh inventions. In this power steering device, the motor drive circuit 2 applies a voltage to the electric motor 4 to drive the electric motor 4 according to the applied voltage instructed by the motor applied voltage instruction unit 8 of the control unit 1e, and the electric motor 4 drives the hydraulic pump 5. To generate operating hydraulic pressure.

A motor current detection circuit 3 for detecting a current flowing through the electric motor 4 is provided between the motor drive circuit 2 and the electric motor 4, and the motor current detection signal is sent to the differential operation section 10 of the control section 1e. Is entered. The differential operation unit 10 differentiates the motor current detection signal, and the differentiated value is input to the differential value determination unit 9f included in the control unit 1e. The differential value determination unit 9f determines the magnitude of this differentiated value with respect to a predetermined value, and sends the determination result to the logical product unit 14. On the other hand, the motor current detection signal is also input to the motor current determination unit 9e included in the control unit 1e. The motor current determination unit 9e determines the magnitude of the input motor current detection signal with respect to a predetermined value, and sends the determination result to the logical product unit 14.

The logical product section 14 calculates the logical product of the judgment results of the differential value judgment section 9f and the motor current judgment section 9e, and sends the calculation result to the motor applied voltage instruction section 8.
The motor applied voltage instruction unit 8 instructs the applied voltage to the electric motor 4 according to the calculation result. The other main structure is the same as the main structure of the power steering device according to the first and second aspects of the invention described above, and thus the description thereof is omitted.

The operation of the power steering device having such a structure will be described below. The motor applied voltage instruction unit 8 included in the control unit 1e is shown in FIG. 2 in order to suppress energy consumption when the steering wheel 7 is not operated and no steering assist force is required (the electric current flowing through the electric motor 4 is small). As described above, the motor applied voltage instruction signal that lowers the voltage applied to the electric motor 4 by one step is output to decrease the output of the electric motor 4. The differential operation unit 10 always differentiates the motor current detection signal output by the motor current detection circuit 3, and the differentiated value is input to the differential value determination unit 9f. The differential value determination unit 9f determines the magnitude of this differentiated value with respect to a predetermined value, and sends the determination result to the logical product unit 14.

The motor current determination unit 9e always determines the magnitude of the motor current detection signal output from the motor current detection circuit 3 with respect to a predetermined value, and sends the determination result to the logical product unit 14. The logical product unit 14 calculates the logical product of the determination results of the differential value determination unit 9f and the motor current determination unit 9e, and sends the calculation result to the motor applied voltage instruction unit 8. The motor applied voltage instruction unit 8 instructs the applied voltage to the electric motor 4 according to the calculation result.

The control wheel 6 is operated when the steering wheel 7 is operated.
Is activated, the hydraulic pressure rises, the load increases, the current flowing through the electric motor 4 increases, and the motor current detection signal output by the motor current detection circuit 3 increases, the differential operation unit 10 detects the motor current. The value obtained by differentiating the signal becomes large.
When the differentiated value (parameter calculation value) becomes larger than the predetermined value P1, the differential value determination unit 9f sets the determination result to H.
It is sent to the logical product section 14 as a level signal. When the motor current detection signal output from the motor current detection circuit 3 becomes larger than a predetermined value, the motor current determination unit 9e sets the determination result to H.
It is sent to the logical product section 14 as a level signal.

When the judgment results of the differential value judgment unit 9f and the motor current judgment unit 9e are both at the H level, the logical product unit 14 outputs the H level signal to the motor applied voltage instruction unit 8.
Send to. In response to this H level signal, the motor applied voltage instruction unit 8 outputs a motor applied voltage instruction signal that raises the voltage applied to the electric motor 4 by one step, as shown in FIG. According to the motor applied voltage instruction signal, the motor drive circuit 2 raises the applied voltage by one stage to drive the electric motor 4 to rotate and increase its output (assist rotation mode).

On the other hand, when the operation of the steering wheel 7 is stopped,
When the operating oil pressure decreases, the load decreases, the current flowing through the electric motor 4 decreases, and the motor current detection signal output by the motor current detection circuit 3 decreases, the differentiation calculation unit 10 differentiates the motor current detection signal. The value becomes smaller (it becomes a negative value). When the differentiated value (parameter calculation value) becomes smaller than the predetermined value P2, the differential value determination unit 9f sends the determination result to the logical product unit 14 as an L level signal. When the motor current detection signal output from the motor current detection circuit 3 becomes smaller than a predetermined value, the motor current determination unit 9e sends the determination result to the AND unit 14 as an L level signal.

The logical product section 14 sends an L level signal to the motor applied voltage instructing section 8 when either or both of the judgment results of the differential value judging section 9f and the motor current judging section 9e are L level. As shown in FIG. 2, the motor applied voltage instructing unit 8 receives the L level signal from the electric motor 4.
A motor applied voltage instruction signal that lowers the voltage applied to the motor by one step is output. According to the motor applied voltage instruction signal, the motor drive circuit 2 lowers the applied voltage by one stage to drive the electric motor 4 to rotate, and reduces the output thereof (standby rotation mode).

In such a power steering device,
Since the motor applied voltage instruction unit 8 controls the instruction voltage by the logical product of the determination results of the differential value determination unit 9f and the motor current determination unit 9e, the predetermined value for the magnitude determination of the motor current determination unit 9e is lowered. Can be set to, the voltage applied to the electric motor is raised one step after the steering wheel is started to operate,
The time lag until the standby rotation mode is switched to the assist rotation mode is reduced, and the steering feeling is improved.

The logical product section 14 may be a logical means for calculating the logical sum of the judgment results of the differential value judgment section 9f and the motor current judgment section 9e. In that case, the predetermined value for determining the magnitude of the motor current determination unit 9e cannot be set to a low value, but when the current flowing through the electric motor begins to increase, the electric current is immediately sent to the electric motor by the value obtained by differentiating the motor current detection signal. The applied voltage is increased by one step, and the time lag from when the steering wheel is started to be operated to when the standby rotation mode is switched to the assist rotation mode is reduced. Further, even when the operation of the steering wheel is gentle and the increase rate (differentiated value) of the motor current value is small, the voltage applied to the electric motor can be controlled at least by the motor current value.

FIG. 7 is a block diagram showing the essential structure of one embodiment of the power steering apparatus according to the sixth and eighth inventions. In this power steering device, the motor drive circuit 2 applies a voltage to the electric motor 4 to drive the electric motor 4 according to the applied voltage instructed by the motor applied voltage instruction unit 8 included in the control unit 1f, and the electric motor 4 drives the hydraulic pump 5. To generate operating hydraulic pressure.

A motor current detection circuit 3 for detecting a current flowing through the electric motor 4 is provided between the motor drive circuit 2 and the electric motor 4, and the motor current detection signal is a motor current detection signal which the controller 1f has. The signal is input to the integration calculation unit 11 for integrating the signal in a predetermined time. Integral calculator 1
1 integrates the motor current detection signal in a predetermined integration time, and the integrated value is obtained as a difference from the motor current detection signal at the subtraction point 17. The obtained difference is input to the integrated value determination unit 9g included in the control unit 1f. The integrated value determination unit 9g determines the magnitude of the obtained difference from a predetermined value, and sends the determination result to the logical product unit 14. On the other hand, the motor current detection signal is also input to the motor current determination unit 9h included in the control unit 1f. The motor current determination unit 9h determines the magnitude of the input motor current detection signal with respect to a predetermined value, and sends the determination result to the logical product unit 14.

The logical product section 14 calculates the logical product of the judgment results of the integrated value judgment section 9g and the motor current judgment section 9h, and sends the calculation result to the motor applied voltage instruction section 8.
The motor applied voltage instruction unit 8 instructs the applied voltage to the electric motor 4 according to the calculation result. The other main structure is the same as the main structure of the power steering device according to the first and second aspects of the invention described above, and thus the description thereof is omitted.

The operation of the power steering device having such a structure will be described below. The motor applied voltage instruction unit 8 included in the control unit 1f is shown in FIG. 2 in order to suppress energy consumption when the steering wheel 7 is not operated and a steering assist force is not required (the electric current flowing through the electric motor 4 is small). As described above, the motor applied voltage instruction signal that lowers the voltage applied to the electric motor 4 by one step is output to decrease the output of the electric motor 4 (standby rotation mode). The integral calculation unit 11 always integrates the motor current detection signal output by the motor current detection circuit 3 for a predetermined integration time, and the integrated value is a difference from the motor current detection signal at the end of integration at the subtraction point 17. Is required. The obtained difference is input to the integrated value determination unit 9g included in the control unit 1f. The integrated value determination unit 9g determines the magnitude of the obtained difference from a predetermined value, and sends the determination result to the logical product unit 14.

The motor current determination unit 9h always determines the magnitude of the motor current detection signal output from the motor current detection circuit 3 with respect to a predetermined value, and sends the determination result to the logical product unit 14. The logical product unit 14 calculates the logical product of the determination results of the integrated value determination unit 9g and the motor current determination unit 9h, and sends the calculation result to the motor applied voltage instruction unit 8. The motor applied voltage instruction unit 8 instructs the applied voltage to the electric motor 4 according to the calculation result.

When the steering wheel 7 is operated, the control valve 6
Is activated, the hydraulic pressure rises, the load increases, the current flowing through the electric motor 4 increases, and the motor current detection signal output by the motor current detection circuit 3 increases, the integral calculation unit 11 detects the motor current. The value obtained by integrating the signal becomes large. The integrated value is input to the subtraction point 17, and the subtraction point 1
At 7, the difference between the motor current detection signal and its integrated value is obtained. The obtained difference is input to the integrated value determination unit 9g. When the obtained difference (parameter calculation value) becomes larger than the predetermined value P1, the integrated value determination unit 9g sends the determination result to the AND unit 14 as an H level signal. When the motor current detection signal output from the motor current detection circuit 3 becomes larger than a predetermined value, the motor current determination unit 9h sends the determination result to the AND unit 14 as an H level signal.

The logical product section 14 outputs an H level signal to the motor applied voltage instructing section 8 when the determination results of the integral value determining section 9g and the motor current determining section 9h are both at the H level.
Send to. In response to this H level signal, the motor applied voltage instruction unit 8 outputs a motor applied voltage instruction signal that raises the voltage applied to the electric motor 4 by one step, as shown in FIG. According to the motor applied voltage instruction signal, the motor drive circuit 2 raises the applied voltage by one stage to drive the electric motor 4 to rotate and increase its output (assist rotation mode).

On the other hand, when the operation of the steering wheel 7 is stopped,
When the operating oil pressure decreases, the load decreases, the current flowing through the electric motor 4 decreases, and the motor current detection signal output by the motor current detection circuit 3 decreases, the integral calculation unit 11 outputs the motor current detection signal for a predetermined time. The value integrated per hit becomes smaller. The integrated value is input to the subtraction point 17, and at the subtraction point 17, the difference between the motor current detection signal and the integrated value is obtained. When the integrated value (parameter calculation value) becomes smaller than the predetermined value P2, the integrated value determination unit 9g
The determination result is sent to the logical product section 14 as an L level signal. When the motor current detection signal output from the motor current detection circuit 3 becomes smaller than a predetermined value, the motor current determination unit 9h sends the determination result to the AND unit 14 as an L level signal.

The logical product section 14 sends an L level signal to the motor applied voltage instructing section 8 when either or both of the judgment results of the integral value judging section 9g and the motor current judging section 9h are L level. As shown in FIG. 2, the motor applied voltage instructing unit 8 receives the L level signal from the electric motor 4.
A motor applied voltage instruction signal that lowers the voltage applied to the motor by one step is output. According to the motor applied voltage instruction signal, the motor drive circuit 2 lowers the applied voltage by one stage to drive the electric motor 4 to rotate, and reduces the output thereof (standby rotation mode).

In such a power steering device,
Since the motor applied voltage instruction unit 8 controls the instruction voltage by the logical product of the determination results of the integrated value determination unit 9g and the motor current determination unit 9h, the predetermined value for the magnitude determination of the motor current determination unit 9h is lowered. Can be set to, the voltage applied to the electric motor is raised one step after the steering wheel is started to operate,
The time lag until the standby rotation mode is switched to the assist rotation mode is reduced, and the steering feeling is improved.

The logical product section 14 may be a logical means for calculating the logical sum of the judgment results of the integral value judging section 9g and the motor current judging section 9h. In that case, the predetermined value for the magnitude determination of the motor current determination unit 9h cannot be set to a low value, but when the current flowing through the electric motor starts to increase, the difference between the motor current detection signal and its integrated value causes Immediately after the voltage applied to the electric motor is raised by one step, the time lag from the start of the operation of the steering wheel to the switching from the standby rotation mode to the assist rotation mode becomes small. Further, even when the operation of the steering wheel is gradual and the increase rate (obtained difference) of the motor current value is small, the voltage applied to the electric motor can be controlled at least by the motor current value.

In the above embodiment, the case where the assist rotation mode and the standby rotation mode are performed according to the level of the motor applied voltage instruction value has been shown, but the present invention is not limited to this. It can also be applied to the case where the rotation mode and the standby rotation mode are performed depending on the level of the motor rotation speed instruction value. FIG. 8 is a block diagram showing the configuration of the essential parts of an example of a power steering apparatus that employs the motor rotation speed control, which is an embodiment of the first and second inventions.

As shown in FIG. 2, the motor rotation speed instruction unit 18 of the control unit 1g determines the motor rotation speed in the assist rotation mode (high rotation speed) and the standby rotation mode (low rotation speed) according to the determination result of the determination unit 9a. Outputs a rotation speed instruction signal. At the subtraction point 20, the difference between the motor rotation speed instruction signal and the motor rotation speed detection value detected by the motor rotation speed detection circuit 19 is obtained. The obtained difference is given to the motor drive circuit 2 to drive the electric motor 4.

Here, the motor rotation speed detection circuit 19 is
From the ripple frequency f of the motor current and the number N of slots of the electric motor 4, V = f / N (1) The motor rotation speed V is detected from the following equation (1). The operations of the differential operation section 10 and the determination section 9a are the same as in the case of the embodiment shown in FIG. Needless to say, the third to eighth inventions can also be applied to a power steering device that employs motor rotation speed control.

[0073]

With the power steering device according to the first and second aspects of the present invention, when the steering wheel begins to be operated and the current flowing through the electric motor begins to increase, the standby rotation mode is immediately switched to the assist rotation mode, and the mode changes. The time lag before switching is reduced.

According to the power steering device of the first and third aspects of the invention, when the steering wheel starts to be operated and the current flowing through the electric motor starts to increase, the standby rotation mode is immediately switched to the assist rotation mode, and the modes are switched. The time lag is reduced. Further, even if the motor current value fluctuates because the viscosity of the hydraulic oil changes with temperature, it means that the difference between the motor current value and the average or integrated value of the motor current value per predetermined time is taken. Therefore, the variation of the motor current value due to the temperature of the hydraulic oil can be eliminated.

According to the power steering device of the first, fourth, and fifth inventions, when the steering wheel begins to be operated and the motor current starts to increase, the standby rotation mode is immediately switched to the assist rotation mode until the mode is switched. The time difference between the two becomes smaller. Further, even when the operation of the steering wheel is gentle and the increase rate of the motor current value is small, the mode switching can be controlled at least by the motor current value.

According to the power steering device of the sixth, seventh and eighth inventions, the predetermined value for judging the magnitude of the motor current value can be set to a low value, and the time from when the steering wheel is started to when the mode is switched. Displacement is reduced and steering feel is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part configuration of an embodiment of a power steering device according to the first and second inventions.

FIG. 2 is an explanatory diagram for explaining the operation of the power steering device according to the present invention.

FIG. 3 is a block diagram showing a main configuration of one embodiment of a power steering device according to the first and third inventions.

FIG. 4 is a block diagram showing a main configuration of one embodiment of the power steering device according to the first and fourth inventions.

FIG. 5 is a block diagram showing a main configuration of one embodiment of a power steering device according to the first and fifth inventions.

FIG. 6 is a block diagram showing a main configuration of one embodiment of a power steering device according to the sixth and seventh inventions.

FIG. 7 is a block diagram showing a main configuration of an embodiment of a power steering device according to the sixth and eighth inventions.

FIG. 8 is a block diagram showing a main configuration of a modified example of the power steering device according to the first and second aspects of the invention.

FIG. 9 is a block diagram showing a configuration example of a main part of a conventional power steering device.

FIG. 10 is an explanatory diagram for explaining the operation of the conventional power steering device.

FIG. 11 is an explanatory diagram for explaining the operation of the conventional power steering device.

[Explanation of symbols]

 1a, 1b, 1c, 1d, 1e, 1f, 1g Control unit 2 Motor drive circuit 3 Motor current detection circuit 4 Electric motor 5 Hydraulic pump 6 Control valve 7 Steering wheel 8 Motor applied voltage instruction unit 9a, 9b, 9c, 9d Judgment unit 9e, 9h Motor current determination unit 9f Differential value determination unit 9g Integral value determination unit 10 Differential calculation unit 11 Integral calculation unit 12, 16, 17, 20 Subtraction point 13, 15 Addition point 14 Logical product unit 18 Motor rotation speed instruction unit 19 Motor rotation speed detection circuit

Claims (8)

[Claims] 1. A power steering device for assisting steering with a hydraulic pump driven by an electric motor rotated in a standby rotation mode and an assist rotation mode as a source of operating hydraulic pressure, wherein a motor current for detecting a current flowing through the electric motor. A detection circuit; a parameter calculation means for calculating a parameter for controlling the switching of the mode based on the motor current value detected by the motor current detection circuit; and a parameter calculated by the parameter calculation means and a predetermined value. A power steering apparatus comprising: a determination unit for determining the magnitude, and a motor control unit for performing the mode switching control according to a determination result of the determination unit. 2. The power steering device according to claim 1, wherein the parameter calculation means is a differentiation calculation means for differentiating a motor current value detected by the motor current detection circuit. 3. The parameter calculation means comprises: calculation means for averaging or integrating motor current values detected by the motor current detection circuit in a predetermined time; and motor current values and values averaged or integrated by the calculation means. The power steering apparatus according to claim 1, further comprising subtraction means for obtaining a difference. 4. The parameter calculation means has differential calculation means for differentiating the motor current value detected by the motor current detection circuit, and addition means for adding the value differentiated by the differential calculation means and the motor current value. The power steering device according to claim 1. 5. The parameter computing means is a means for averaging or integrating motor current values detected by the motor current detecting circuit in a predetermined time, and a difference between the motor current value and a value averaged or integrated by the computing means. 2. The power steering apparatus according to claim 1, further comprising: a subtracting unit that obtains the difference, and an adding unit that adds the difference obtained by the subtracting unit and the motor current value. 6. A power steering device for assisting steering with a hydraulic pump driven by an electric motor rotated in a standby rotation mode and an assist rotation mode as a source of operating hydraulic pressure, wherein a motor current for detecting a current flowing through the electric motor. A detection circuit; a parameter calculation means for calculating a parameter for controlling the switching of the mode based on the motor current value detected by the motor current detection circuit; and a parameter calculated by the parameter calculation means and a predetermined value. Parameter determination means for determining the magnitude, motor current determination means for determining the magnitude of the motor current value and a predetermined current value, and logic for calculating the logic of each determination result of the parameter determination means and the motor current determination means Means and a motor control for controlling the switching of the modes according to the calculation result of the logic means. Power steering apparatus characterized by comprising a means. 7. The power steering apparatus according to claim 6, wherein the parameter calculation means is a differentiation calculation means for differentiating a motor current value detected by the motor current detection circuit. 8. The parameter calculating means comprises: calculating means for averaging or integrating motor current values detected by the motor current detecting circuit in a predetermined time; and motor current values and values averaged or integrated by the calculating means. 7. The power steering device according to claim 6, further comprising subtraction means for obtaining a difference.