JPH02227B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a power steering device.

In recent years, power steering devices have been installed in vehicles so that even people with weak physical strength, such as female drivers, can easily operate the vehicle, and even in such cases, the amount of steering assist force can be changed depending on the difference in the physical strength of the driver. It is desirable to make it possible. 2. Description of the Related Art For example, a power steering device shown in FIG. 1 is known as a power steering device that can arbitrarily change the steering assist force generated by the power steering device. This power steering device 1
To explain, 2 is a reservoir tank, 3 is a constant flow pump that sucks and pressurizes working fluid from the reservoir tank 2, and the pump 3 is rotated in synchronization with the crankshaft rotation speed of the internal combustion engine of the vehicle. The working fluid discharged from the constant flow pump 3 is supplied to the supply pipe 4
The control valve 5 is switched depending on the magnitude and direction of the steering force applied to a steering wheel (not shown), and the working fluid is supplied to the fluid chamber 7 or 8 of either one of the power cylinders 6. to flow into. The other small fluid chamber 8 or 7 can communicate with the reservoir tank 2 via the control valve 5 and return pipe 9, and as a result, the steering assist force generated by the power cylinder 6 is applied to steering wheels (not shown). Ru. 10 is a bypass pipe connected to the supply pipe 4 and the return pipe 9, and the bypass pipe 10 has a bypass valve 11.
is intervening. The bypass valve 11 has a pressure compensation valve section 12 and a flow rate adjustment valve section 13, and the flow rate adjustment valve section 13 has a throttle 16 defined by a body 14 and a valve body 15. The opening area of the throttle 16, and therefore the bypass flow rate of the working fluid passing through the throttle 16, are determined by the elastic force of the spring 17 that biases the valve body 15 in the direction of increasing the opening area and the valve body 1.
5 is determined by the elastic force of the spring 17 and the pressing force generated by the solenoid 18 that biases the solenoid 18 in the opposite direction, and the pressing force generated by the solenoid 18 is determined by the current value of the current signal applied to the solenoid 18 from the control circuit 19. Determined by Therefore, the relationship between the bypass flow rate and the current value applied to the solenoid 18 is shown in FIG. On the other hand, the control circuit 19
are the three patterns H shown in FIG.
A memory storing M and L, and a steering force changeover switch 20 as shown in the flow diagram of FIG.
Either pattern H, M, L depending on the signal from
an arithmetic processing section that selects a current value of a current signal to be energized to the solenoid 18 by calculating the required bypass flow rate at the vehicle speed from patterns H, M, or L based on the signal from the vehicle speed sensor 21; and an output section that transmits a current signal having a current value determined by the arithmetic processing section. Therefore, if the driver switches between patterns H, M, and L while driving the vehicle, the aperture 1
6 is changed, and the bypass flow rate of the working fluid passing through the throttle 16 is changed. in this way,
When the bypass flow rate of the working fluid is changed, the steering assist force changes to areas H', M', and H', corresponding to patterns H, M, and L, respectively.
Since the steering force changes as shown in L', the driver may accidentally operate the steering force changeover switch 20 while driving at high speed or when the vehicle is turning.
When M and L are changed, the steering assist force immediately changes rapidly, making the operation of the steering wheel unstable and potentially causing an accident.

This invention has been made in view of the above problems, and detects one or more of the following: vehicle speed, lateral acceleration applied to the vehicle, steering angle from a neutral position of the steering wheel, and steering angular velocity of the steering wheel. A driving state detection means is provided which outputs a signal indicating the vehicle driving state determined by these means, and the signal output from the driving state detection means prevents unstable steering wheel operation due to sudden changes in steering assist force. The control circuit is configured to switch the steering force control valve according to the pattern before the output of the signal even if there is an instruction from the command means to change the pattern when a driving condition that may lead to the problem is displayed. It is an object of the present invention to solve the above problems by providing a power steering device.

Hereinafter, this invention will be explained based on the drawings.

FIG. 6 is a diagram showing a first embodiment of the present invention, and the configuration will be explained first. Note that only the same reference numerals are given to the same components as those of the conventional power steering device 1, and the explanation thereof will be omitted. Reference numeral 24 denotes a control circuit capable of transmitting a current signal of a predetermined current value to the solenoid 18 of the flow rate regulating valve section 13, and this control circuit 24 includes a steering force changeover switch 20 that can be manually switched by the driver as in the conventional case. , a vehicle speed sensor 25 that can detect the running speed of the vehicle and output a signal to display the running speed; and a steering angle sensor 26 that can detect the rotation angle of the steering wheel from the neutral position and output a signal to display the rotation angle. is also connected. The vehicle speed sensor 25 and the steering angle sensor 26 collectively constitute a driving state detection means 27,
The control circuit 24 has the same pattern H, M, L as before.
It has a memory section consisting of ROM and RAM that stores information, an arithmetic processing section, and an input/output section.

Next, the operation will be explained based on the flow diagram shown in FIG.

First, when the traveling speed of the vehicle is less than the first predetermined value a, signals Ln, Mn, and Hn are output from the steering force changeover switch 20 corresponding to patterns L, M, and N, respectively, regardless of the rotation angle of the steering wheel.
Load into RAM. Next, the signal Ln from the steering force changeover switch 20 stored in the RAM,
Based on Mn and Hn, the bypass flow rate corresponding to the traveling speed indicated by the signal from the vehicle speed sensor 25 is determined.
The current value of the current signal sent to is calculated (the relationship between bypass flow rate and current value is the same as before,
(according to Figure 2). In this way, when the traveling speed is less than the first predetermined value a, as soon as the driver switches the steering force changeover switch 20, the pattern H,
Although M and L are switched and the steering assist force changes, since the traveling speed is low and less than the first predetermined value a, the operation of the steering wheel does not become unstable.

Next, when the traveling speed of the vehicle is greater than or equal to the first predetermined value a but less than the second predetermined value k, the signal from the steering angle sensor 26 operates as follows. That is, when the rotation angle of the steering wheel is less than the fixed value y, the signals Ln, Mn, and Hn from the steering force changeover switch 24 are set to the predetermined value in the RAM, as in the case where the traveling speed is less than the first predetermined value a. address, determines the data at a predetermined address in this RAM, selects pattern H, M or L, and sends the bypass flow rate to the solenoid 18 based on the pattern H, M or L stored in the ROM. The current value of the current signal is calculated. Therefore, in this case as well, when the driver switches the steering force changeover switch 20, patterns H, M, and L are immediately switched and the steering assist force changes, but the traveling speed is less than the second predetermined value K. Moreover, the rotation angle of the steering wheel is small, so steering wheel operation will not become unstable. On the other hand, when the rotation angle of the steering wheel is equal to or greater than the fixed value y, the steering force changeover switch 20
Signals Ln, Mn, and Hn from are not read into RAM. Therefore, even if the driver switches the steering force changeover switch 20 during a period when the rotation angle of the steering wheel is greater than or equal to the fixed value y, the signal of the steering force changeover switch 20 stored in the RAM will not be changed, and the signal stored in the RAM will not be changed. The signal Ln, Mn, or Hn of the steering force changeover switch 20 immediately before the rotation angle of the steering wheel becomes equal to or greater than a certain value y is stored, and the pattern H, M, or L is maintained.
As a result, the current value of the current signal sent to the solenoid 18 is determined based on the pattern H, M, or L stored in the ROM in accordance with the traveling speed of the vehicle, and the driver accidentally switches the steering force changeover switch 20 Even if the steering assist force is switched, there is no sudden change in the steering assist force, and the operation of the steering wheel does not become unstable.

Next, when the traveling speed of the vehicle is equal to or higher than the second predetermined value k, the signal Ln, Mn, or Hn from the steering force changeover switch 20 is read into the RAM regardless of the rotation angle of the steering wheel. will not be performed. Therefore, the RAM stores the signal Ln, Mn, or Hn from the steering force changeover switch 20 immediately before the traveling speed reaches the second predetermined value k, and the bypass flow rate and the current sent to the solenoid 18 are stored in the RAM. The current value of the signal is determined based on the pattern H, M or L in accordance with the traveling speed. Therefore, even if the driver accidentally switches the steering force changeover switch 20 while driving at high speeds where the traveling speed is higher than the second predetermined value k, there will be no sudden change in the steering assist force, and the steering operation will become unstable. It won't happen.

Next, a second embodiment of the invention will be described. Note that the same reference numerals are used for the same components as in the first embodiment. In the second embodiment, the running state detection means 28 is constituted by a lateral acceleration sensor 29 that detects lateral acceleration that the vehicle receives while the vehicle is turning and outputs a signal proportional to the acceleration. Therefore, as shown in FIG. 8, when the signal output from the driving state detection means 28 indicates that the lateral acceleration received by the vehicle is less than the predetermined value b, the control circuit 30 is steering force selector switch 2
The signal Ln, Mn or Hn from 0 is read and the steering assist force is immediately changed. However, if the signal from the driving state detection means 28 indicates that the lateral acceleration received by the vehicle is equal to or greater than the predetermined value b, the steering force changeover switch 20
The signals Ln, Mn or Hn from are not read into RAM.

Generally, while the vehicle is experiencing a constant lateral acceleration, a constant steering holding force is required to hold the steering wheel in a predetermined position. Therefore,
A sudden change in the steering assist force causes a sudden change in the steering force that the driver should apply to the steering wheel. Therefore, if the turning radius of the vehicle is small, that is, the lateral acceleration is large, a sudden change in the steering assist force will result in unstable steering operation. However, in this second embodiment, when the lateral acceleration is equal to or greater than the predetermined value b, the patterns H, M, or L cannot be changed, so the steering operation does not become unstable. Note that the portion labeled A in FIG. 8 corresponds to the portion labeled A in FIG. 7.

Next, a third embodiment of the invention will be described. Note that the same reference numerals are used for the same components as in the first embodiment and the second embodiment. In the third embodiment, the driving state detection means 31 is constituted by a vehicle speed sensor 25 and a lateral acceleration sensor 29, and when the operating speed of the vehicle is less than a predetermined value c and the lateral acceleration is less than a predetermined value d. Only then, the signal Ln, Mn or Hn from the steering force changeover switch 20 is read into the RAM. Therefore, when at least one of the traveling speed and the lateral acceleration received by the wheels is greater than or equal to the predetermined value c or d, the signals Ln, Mn, or Hn from the steering force changeover switch 20 are not read into the RAM, and the pattern H, There is no switching between M or L. Therefore, a sudden change in the steering assist force due to switching between patterns H, M, or L does not occur, and the steering operation does not become unstable.

Similarly to the first to third embodiments above, it is also possible to detect the steering angular velocity to determine the running state, and it can be handled in the same way as the steering angle in the first embodiment or the lateral G in the third embodiment. Since it is obvious that this is the case, specific examples will be omitted.

As described above, according to the present invention, the power steering device has a pump that pressurizes working fluid and discharges high-pressure fluid, and a pair of fluid chambers into which high-pressure fluid can flow, and provides steering control to steering wheels. a power cylinder capable of applying an auxiliary force; a switching valve connected to a steering wheel of a vehicle to allow high-pressure fluid to flow into one of a pair of fluid chambers according to the magnitude and direction of a steering force applied to the steering wheel; A command is given to a steering force control valve that increases or decreases the steering assist force generated by the power cylinder, a control circuit that can switch the steering force control valve according to one of a plurality of patterns that increase or decrease the steering assist force, and a control circuit. a command means for instructing a pattern for switching the steering force control valve; and a command means for detecting one or more of the vehicle speed of the vehicle, the lateral acceleration applied to the vehicle, the steering angle from the neutral position of the steering wheel, and the steering angular velocity of the steering wheel. and a driving state detection means for displaying the vehicle driving state determined by these means, and the signal output from the driving state detection means detects unstable steering wheel operation due to sudden changes in steering assist force. The control circuit is configured to switch the steering force control valve according to the pattern before the output of the signal even if there is an instruction from the command means to change the pattern when a driving state that may lead to the problem is displayed. Therefore, it is possible to prevent accidents caused by unstable operation of the steering wheel.

[Brief explanation of drawings]

Fig. 1 is a hydraulic circuit diagram showing a conventional power steering device, Fig. 2 is a graph showing the relationship between the current value of the current signal energized to the solenoid and the bypass flow rate, and Fig. 3 is a graph showing the relationship between the vehicle speed and the bypass flow rate. FIG. 4 is a flow diagram showing the operation of the control circuit in FIG. 1, FIG. 5 is a graph showing the relationship between steering force and steering assist force, and FIG. FIG. 7 is a flow diagram showing the operation of the control circuit in FIG. 6, FIG. 8 is a flow diagram showing the operation of the control circuit in the second embodiment of the present invention, and FIG. It is a flowchart which shows the operation|movement of the control circuit in 3rd Example. 3... Metering pump, 5... Switching valve (control valve), 6... Paro cylinder, 7, 8... Fluid chamber (fluid small chamber), 11... Steering force control valve (bypass valve), 2
0... Command means (steering force changeover switch), 24, 3
0...control circuit, 27, 28, 31...driving state detection means.

Claims (1)

[Claims] 1 A pump that pressurizes working fluid and discharges high-pressure fluid, a power cylinder that has a pair of fluid chambers into which high-pressure fluid can flow and can apply steering assist force to steered wheels, and is connected to the vehicle's steering wheel. a switching valve that allows high-pressure fluid to flow into one of the pair of fluid chambers according to the magnitude and direction of the steering force applied to the steering wheel; and a steering force control that increases or decreases the steering assist force generated by the power cylinder. a control circuit capable of switching the steering force control valve according to one of a plurality of patterns for increasing or decreasing the steering assist force; a command means for giving a command to the control circuit and instructing a pattern for switching the steering force control valve; In a power steering device equipped with
One of the steering angle from the neutral position of the steering wheel and the steering angular velocity of the steering wheel
Alternatively, a driving condition detecting means is provided which detects two or more and outputs a signal indicating the driving condition of the vehicle determined by these, and the signal output from the driving condition detecting means is unstable due to a sudden change in the steering assist force. When a driving condition that may lead to operation of the steering wheel is displayed, the steering force control valve is switched according to the pattern before the output of the signal even if there is an instruction to change the pattern from the command means. A power steering device comprising the control circuit described above.