JPH0258142B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a speed-sensitive power steering device, and more particularly to a safety control device that functions when an abnormality occurs in a vehicle speed sensor. (Prior Art) As a speed-sensitive power steering device, the applicant of the present application proposed the device of Utility Model Application No. 167828/1983 (Kokai No. 95968/1988). As shown in FIG. 1, the flow control system includes a variable throttle valve 8 and a fixed throttle valve 9 arranged in parallel between the hydraulic pump 7 and the power steering unit 10, and the control of the variable throttle valve 8 is performed in steps. This is done using motor 6. That is, the flow rate of the pressure fluid discharged from the hydraulic pump 7 is controlled by a variable throttle valve 8 and a fixed throttle valve 9 controlled by a step motor 6 to change the steering force. 1 in the diagram
Reference numeral 1 denotes a flow rate control valve of the hydraulic pump 7, which causes the excess pressure fluid to flow back to the oil tank 13 when the discharge flow rate of the hydraulic pump 7 becomes excessive. Reference numeral 12 denotes a pressure guarantee relief valve of the power steering unit 10, which causes the excess pressure fluid to flow back to the oil tank 13 when the fluid pressure of the unit 10 becomes excessive. The details are described in the specification of the above-mentioned Utility Model Application No. 167828/1983, so the explanation will be omitted here. As shown in FIG. 2, the control device for the step motor 6 detects, for example, the rotational speed of the output shaft of an automobile transmission, and connects the output of a vehicle speed sensor 1, which generates an electric signal that changes in accordance with the vehicle speed, to a one-shot circuit. The voltage is input to an F-V converter (frequency-voltage converter) (2) consisting of a D-A converter (digital-to-analog converter), etc., where it is converted into a voltage proportional to the vehicle speed, and then passed through the home return circuit 3. Input to Schmitt circuit group 4. Each Schmitt circuit has preset voltages (V ₁ ), (V ₂ )...(V _o ) and the F-V converter 2
The output from the origin return circuit 3 which received the output is compared with the output from the origin return circuit 3. A distribution circuit 5 consisting of an exclusive OR circuit group, an OR circuit, and an amplifier group receives the output of the Schmitt circuit and distributes the excitation coils A,
It is determined which of B and C is to be excited. In other words, the rotation angle of the step motor 6 is controlled in response to changes in the output of the vehicle speed sensor 1, and the throttle amount of the variable throttle valve 8 is controlled, the details of which are detailed in the above specification. Therefore, detailed explanation will be omitted. FIG. 3 is a diagram showing an example of a case where the variable throttle valve 8 is formed directly on the rotor shaft 6a of the step motor 6, and the rotor shaft 6a is further provided with a return spring 6.
The rotor shaft 6a is provided with mechanical positioning means such as b, and the rotor shaft 6a is moved to a position where the throttle opening area of the variable throttle valve 8 is minimized by the spring 6b when all of the excitation coils A, B, and C are de-energized. position. When the ignition key switch (not shown) is turned on, the output voltage of the home return circuit 3 rises at a predetermined slope from OV to the maximum voltage, and the control home position is reached where the throttle opening area of the variable throttle valve 8 is maximized. The rotor shaft 6a is rotated. Thereafter, the output voltage of the home return circuit 3 is the value obtained by subtracting the output voltage of the F-V converter 2 from the above maximum voltage, and the throttle amount of the variable throttle valve 8 is controlled by the control circuit to which this subtracted voltage is applied. Changes are made in stages in response to changes in vehicle speed. In the figure, 6c is a rotor. In the illustrated case, the step motor 6 is shown mounted directly on the housing of the hydraulic pump 7. (Problems to be Solved by the Invention) Based on the above, the invention of Utility Application No. 167828/1983 controls the rotation angle of the step motor in response to changes in vehicle speed, and provides steering power when the vehicle is stopped or running at low speed. When driving at high speeds, a steering reaction force corresponding to the vehicle speed is applied to the steering wheel shaft, thereby eliminating the feeling of anxiety caused to the driver due to steering wheel wobbling or too light steering resistance, especially when driving at high speeds. be. However, in this case, if the vehicle speed sensor fails and the pulse train is no longer input to the control device, the conditions will be the same as when the ignition key switch is turned on when the vehicle is stopped. Since this is the maximum state of the variable aperture aperture, the maximum steering force assistance is given.
The steering wheel was at its lightest, which resulted in an increased feeling of steering instability when driving at high speeds. This invention completely eliminates the above drawbacks,
The purpose of this is to eliminate the cause of unstable steering during high-speed driving by operating the variable throttle valve to a position where a safe steering force for high-speed driving can be obtained at the same time as an abnormal situation occurs. (Means for Solving the Problems) The present invention provides means for eliminating the feeling of steering instability.
Abnormality of the vehicle speed sensor is detected by detecting that the vehicle speed signal changes faster than a predetermined value, or by monitoring multiple vehicle speed sensors, and when an abnormality is detected, the variable throttle valve installed in the pressure fluid pipe is activated. This safety control device minimizes the opening area of the variable throttle valve by cutting off the power supply to the driving step motor, thereby making it possible to obtain safe steering force during high-speed driving. (Function) According to the above means, even if an abnormality occurs in the vehicle speed sensor system during high-speed driving, it is possible to prevent the steering reaction force from becoming too light, and it is possible to eliminate the feeling of instability during high-speed driving. (Embodiment) To explain the embodiment, a variable throttle valve 8 and a fixed throttle valve 9 are provided between the hydraulic pump 7 and the power steering unit 10 to control the flow rate of pressure fluid.
are arranged in parallel, and the throttle amount of the variable throttle valve 8 is controlled in response to changes in vehicle speed by a step motor 6 whose rotation angle is controlled based on a pulse signal of a frequency proportional to the vehicle speed from the vehicle speed sensor 1. In the flow control device (see FIGS. 1, 2, and 3), the output pulse signal of the vehicle speed sensor 1 is detected between the vehicle speed sensor 1 and the step motor 6 as shown in FIG. A microcomputer 14 has a CR differentiation circuit 18 connected to its reset terminal and operates according to a predetermined program, and each excitation coil A, B, C, D of the step motor 6 is turned on and off by the output signal of the computer 14. A driver circuit 15 including a group of transistors for opening and closing an excitation circuit is provided. 17 receives the output signal from the other output terminal OB ₀ of the microcomputer 14 and activates the excitation coils A, B, C, and
16 is a switching circuit for opening and closing D, and 16 is another output terminal of the microcomputer 14.
This is an error indicator connected to OB ₁ . Further, a circuit 19 is provided for reading the coil end voltage of each excitation coil A, B, C, D into each input terminal IB ₀ , IB ₁ . . . IB ₃ of the microcomputer 14. The vehicle speed sensor 1 is, for example, disclosed in the above-mentioned Utility Model Application No. 53-167828.
As disclosed in the invention of No. 1, any device that outputs a pulse signal with a frequency proportional to the vehicle speed may be used as long as it is related to the output shaft of an automobile transmission, a speedometer, or the like. The microcomputer 14 is a one-chip microcomputer, and includes a central processing unit (CPU), a read-on memory (ROM), a random access memory (RAM), and a predetermined number of inputs IA ₀ in one package. INT, IB ₀ ...IB ₃ ,
Outputs OA ₀ , OA ₁ ...OA ₃ , OB ₀ , OB _1, etc. may be stored on the market, and the above-mentioned ones may be used.
The programs described below are embedded in the ROM and RAM. The driver circuit 15 consists of a group of transistors connected to each output port OA ₀ , OA _{1 .} . . OA ₃ of the microcomputer 14 . A flowchart of the program stored in the ROM of the microcomputer 14 is shown in Figure 7A, and details of each routine are shown in Figures 7B to 7B.
It is shown in F. The operation will be explained below with reference to FIGS. 4 and 7. When the ignition key switch is turned on, the electronic circuit shown in FIG. A level 1 signal is given. As a result, microcomputer 1
4 output ports OA ₀ , OA ₁ , OA ₂ , OA ₃ ,
OB ₀ , OB ₁ are all turned off and at the same time
Execution of the instruction starts from ROM address 0. In this state, each transistor of the driver circuit 15 of the step motor 6 is in an off state, so the excitation coils A, B, and
No current flows through C and D, so the step motor 6 is operated by the return spring 6 attached to the rotor shaft 6a.
At b, the variable throttle valve 8 in FIG. 1 is stopped at the rotational position where the throttle valve is maximized (minimum throttle opening area). First, an initialization routine is executed.
Here, the RAM in the microcomputer 14
The output port _OB0 is set to logic level 1, and the transistor of the switching circuit 17 is turned on. Next, a routine is executed in which the step motor 6 is rotated to the rotational position where the variable throttle valve 8 shown in FIGS. 1 and 3 is opened to the maximum, that is, to the origin position at which control is started. The details are shown in Figure 7B. At this time, the signals are output from the output ports OA ₀ to _{OA 3} of the microcomputer 14 as shown in Table 1.

[Table] The above table shows an example in which the step motor 6 has 2-2 excitation and 8 steps. Therefore, each transistor of the driver circuit 15 is turned on and off according to Table 1, and the step motor 6 rotates against the return spring 6b attached to the rotor shaft 6a, causing the variable throttle valve 8 to reach its maximum value. to the open state. That is, the rotation operation of the step motor toward the control origin shown in FIG. 7B is completed. The step motor drive SUB (subroutine) in the initialization routine of FIG. 7 is shown in FIG. 7E. That is, when executing the step motor drive subroutine, it is determined whether the direction of rotation is forward or reverse based on the previous control code. Table 1
is the case of reversal. Next, the excitation coil end voltage of the step motor 6 is applied to the input port of the microcomputer 14.
IB ₃ , IB ₂ ... are read in IB ₀ , but this means, for example, if 1001 is output from output ports OA ₃ to _{OA 0} and what is read in IB ₃ to IB ₀ is 0110, the micro This is because the connection between the computer 14 and the driver circuit 15, the operation of the driver circuit 15, the coil of the step motor 6, the connection between the battery and the step motor, etc. are determined to be normal. If there is an abnormality, the process moves to the abnormality processing routine shown in FIG. 7A. The processing up to the above is performed at a sufficiently high speed. Since the vehicle is still at a standstill and the variable throttle valve 8 is at its maximum opening, the power steering unit 10 provides maximum steering force assistance. Next, as shown in FIG. 7A, the routine is made interruptible and serves a purpose other than the purpose of the present invention, but this is not always necessary. The output of the vehicle speed sensor 1 is connected to the interrupt terminal INT and input terminal _IA0 of the microcomputer 14, as shown in the fourth diagram. In this example, the microcomputer 14 accepts an interrupt at the rising edge of the pulse signal. Therefore, when a signal from the vehicle speed sensor 1 is input, the process jumps to the interrupt routine at the rising edge of the signal. First, a vehicle speed measurement routine is entered, the details of which are shown in FIG. 7C. The counter V is prepared in the RAM of the microcomputer 14,
First, that area of RAM is cleared to zero. Next, it is checked whether the input terminal _IA0 of the microcomputer 14 to which the output of the vehicle speed sensor 1 is connected is at a logic level of 1 or 0. In this case,
Since the signal from the vehicle speed sensor 1 has just been received, the signal flows in the direction of NO in the figure and 1 is added to the counter V. Subsequently, it is checked whether the counter V is greater than or equal to a specified value. This is to avoid staying in one loop for longer than necessary, and exits from this routine when the value exceeds the specified value. Then, the signal from the vehicle speed sensor 1 is checked again to see if it is 1 or 0, and while the signal is 1, the loop of adding 1 to the counter V is repeated. When the signal from the vehicle speed sensor 1 becomes 0, this routine is exited and the vehicle speed comparison routine is entered. As a result, the counter V
is inversely proportional to the vehicle speed, that is, when the vehicle speed is high, the value of the counter V is small, and when the vehicle speed is low, the value of the counter V is large. It goes without saying that the counter V may be configured to contain a numerical value proportional to the vehicle speed. In the vehicle speed comparison routine, the step motor 6 is controlled to switch the throttle amount of the variable throttle valve 8 each time a predetermined speed is reached in accordance with the steering characteristics. FIG. 7D shows details of the vehicle speed comparison routine. The signal flows in the YES direction when the conditions of each speed comparison step (velocity A or less, B or less, C or less... X or less) is met, and flows in the NO direction when the speed is X or more. Since the routine following each step is the same operation, next we will explain the case where the speed is less than A. (11) First, the fact that the speed is below A is stored in the RAM area, and it is checked whether the current control position of the step motor 6 and the control position that must be controlled when the speed is below A are the same. If they are the same, there is no need to control them again.
Flows in the direction of YES, and counter L (described later) becomes 0.
It is cleared, and then the coil end voltage test subroutine (FIG. 7(e)) is called and executed. This explanation has been given in the previous section. Next, if the flow is in the NO direction, a check is made to see if the positional relationship between the current control position of the step motor 6 and the position that must be controlled when the speed is below A is one step of the step motor 6. Ru. In other words, microcomputer 1
Since the control speed of 4 is performed sufficiently fast in response to changes in vehicle speed, it is impossible for the control speed to exceed 2 steps under normal conditions. For example, an abnormality occurs when a change occurs that is considerably faster than a change in vehicle speed, such as when the vehicle speed sensor 1 is damaged while driving or the speedometer's flexible shaft (vehicle speed sensor drive system) is damaged. . Therefore, this step makes it possible to discover abnormal situations,
Appropriate action will be taken as described below. In particular, when the abnormal situation occurs during high-speed driving, the conventional system causes the steering wheel to suddenly become lighter, which is dangerous, but this invention completely overcomes this drawback. If this step is successful, then loop counter L is checked. This counter L also
This is prepared in the RAM area and is provided to prevent the step motor 6 from being controlled too quickly. In other words, entering this step means that it is necessary to rotate the step motor 6, but the time interval of entering the speed comparison routine is too short compared to the time during which the vehicle speed changes, and this interval If the vehicle speed is close to the speed at which the variable throttle valve 8 is switched, the step motor 6 will be controlled at shorter intervals than necessary, causing chattering and unstable operation. In order to avoid this, a loop counter L is provided, and the step motor 6 is controlled only when a specified number of consecutive signals come to this step. Therefore, if you have not yet reached the specified number of times,
Add 1 to the counter L, exit from the interrupt routine, and return to the original routine. On the other hand, if the specified number of times is reached, it means that the speed is stable (below speed A), so the counter L is cleared to 0 and the rotation direction of the step motor 6 is set to a predetermined position in the RAM area. Then, the program moves to the step motor drive subroutine, and then exits from the interrupt routine and returns to the original routine. As a result, the step motor 6 is rotated one step. Even after returning to the original routine, when the pulse signal from the vehicle speed sensor 1 is input to the microcomputer 14 again, the interrupt routine is entered again and the above-described steps are executed. If an abnormality occurs in the above operation, the process jumps to an abnormality processing routine. The error handling routine is
It is shown in FIG. In the error handling routine,
First, interrupts are disabled, and even if an interrupt request is made again, it will not jump to the interrupt routine. Next, the step motor 6 is turned off. This can be done by setting the output ports OA ₀ to _{OA 3} to 0000, which turns off all transistors of the driver circuit 15, but depending on the type of abnormal situation, , since the transistor in the driver circuit 15 may become conductive and be damaged, the transistor in the switching circuit 17 is turned off.
In other words, a method may be adopted in which the output port OB ₀ is set to 0. These may be selected depending on the design concept of the system. Of course, if the former method is used, the switching circuit 17 is not necessary, and a circuit configuration for direct power supply as shown by the broken line in FIG. 4 may be used. Then, the abnormality display output port OB ₁ is set to 1 and the routine shifts to another routine. As a result, the supply of electrical energy to the step motor 6 is cut off, and the motor 6 is rotated to a position where the variable diaphragm 8 is set to the minimum diaphragm opening area by the return spring 6b that biases the rotor shaft 6a. do. Therefore, the steering force assistance of the power steering unit 10 is minimized, completely eliminating the inconvenience that the steering wheel becomes too light when driving at high speed, and safety is dramatically improved. Although the operation in the case where only one vehicle speed sensor 1 is provided has been described above, the vehicle speed sensor 1 may be provided with two vehicle speed sensors 1 and 1' as shown in FIG. The vehicle speed sensors 1 and 1' are installed at the same location or at different locations so as to be able to detect the vehicle speed, and are provided so that the phases of signal generation are shifted from each other. FIG. 8 is a diagram showing the operation when two vehicle speed sensors 1 and 1' are installed as described above, and when either vehicle speed sensor 1 or 1' is turned on, an interrupt is sent to the microcomputer 14. The program then jumps to the interrupt routine, where it is checked whether signals are alternately received from the two vehicle speed sensors 1 and 1'. If they are not alternate, it means that one of the vehicle speed sensors 1 or 1' is damaged, and the process jumps to the abnormality processing routine. It is normal if the signals are input alternately, so if the signal that has just arrived is from a sensor for measurement, it will be executed in the same way as described in the above sections. By providing the two vehicle speed sensors 1 and 1' in this way, it becomes possible to detect damage or malfunction of either of the vehicle speed sensors or the system that reaches the vehicle speed sensor before starting the vehicle. FIG. 6 shows an example in which the rotation sensor 20 is attached directly to the rotor shaft 6a of the step motor 6.
A rotary encoder or other possible means may also be employed. This is provided to check whether the instruction of the rotational position of the step motor 6 is correct. This can be done by reading the output of this rotation sensor 20 into the microcomputer 14 instead of inputting the voltage at the end of the step motor coil in FIG. At this time, step-out of the step motor 6 and mechanical failure can also be detected, compared to the case where the coil end voltage is read. Further, instead of the counting means using the counter L marked with a square mark in FIG. As shown in Fig. 9, this is done by adding a constant to the counter V, determining whether it is above the specified value, and if YES, setting the stepper motor in reverse, and if NO, subtracting the constant from the counter V, If it is below the specified value, the step motor is set to normal rotation. Further, as shown in FIG. 10, the microcomputer 14 has an appropriate number of mode selection input terminals IC ₀ , IC _{1 .} . . pulled up by resistors R ₀ , R ₁ .
A mode selection circuit 21 can also be provided, which includes selection switches S _{0 ,} S _{1 ,} . A flowchart at that time is shown in FIG. That is, it may be combined with the vehicle speed comparison routine shown in FIG. 7D. (Effects of the Invention) As detailed above, according to the present invention, the abnormality detection means of the vehicle speed sensor and the opening area of the variable throttle valve are minimized when an abnormality is detected, so that safe steering force can be obtained during high-speed driving. (the state of maximum steering resistance) It is possible to prevent the occurrence of steering instability that would occur if the steering wheel becomes too light, thereby completely overcoming the conventional drawbacks of this type of device and improving safety and stability during high-speed driving. Significantly improved. Furthermore, although the present invention does not necessarily require the use of a microcomputer as in the above embodiment, the microcomputer can detect speed from the output of the vehicle speed sensor, control drive of the step motor, detect abnormality of the vehicle speed sensor, and perform safe operation. By controlling the steering force, it is possible to perform safety control with high reliability without being affected by fluctuations in power supply voltage or temperature changes. Furthermore, since commercially available microcomputers can be used, the cost is low;
Moreover, since it only needs to be a single chip type, the installation space is small.

[Brief explanation of drawings]

Fig. 1 is a hydraulic circuit diagram showing the system configuration of a flow rate control device, Fig. 2 is a block circuit diagram showing a conventional step motor control device, Fig. 3 is a partial sectional view showing the configuration of a step motor, and Fig. 4 is a hydraulic circuit diagram showing the system configuration of a flow rate control device. The figure is an electronic circuit diagram of the present invention, FIGS. 5 and 6 are electronic circuit diagrams showing only the main parts of other embodiments, and FIGS.
FIGS. 8 and 9 are flowcharts of other embodiments, respectively, and FIGS.
The figure is an electronic circuit diagram showing only the essential parts of another embodiment, and FIG. 11 is a flowchart of FIG. 10. 1, 1'... Vehicle speed sensor, 6... Step motor, 7... Hydraulic pump, 8... Variable throttle, 9...
Fixed aperture, 10...Power steering unit, 14...Microcomputer, 15...Driver circuit, 16...Error indicator, 17...Switching circuit, 18...CR differential circuit, 19...
...Coil end voltage reading circuit, 20...Rotation sensor,
21...Mode selection circuit.

Claims (1)

[Scope of Claims] 1. Speed-sensitive power in which a variable throttle valve provided in a pressure fluid pipe is controlled in response to changes in vehicle speed detected by a vehicle speed sensor, and its steering force is controlled in accordance with vehicle speed. The steering device is characterized in that it is provided with an abnormality detection means for a vehicle speed sensor and a control means for minimizing the opening area of the variable throttle valve when an abnormality is detected so that a safe steering force can be obtained during high-speed running. Control device. 2. The safety control device according to claim 1, wherein the abnormality detection means of the vehicle speed sensor detects that the change in the vehicle speed signal is considerably faster than the change in the vehicle speed. 3. The vehicle speed sensor is composed of a plurality of vehicle speed sensors,
2. The safety control device according to claim 1, wherein the abnormality detecting means determines that the signals of all the vehicle speed sensors are input as normal, and that the abnormality detecting means determines that the signals are abnormal when even one signal is missing. 4. The drive means for the variable throttle valve is a step motor that uses a return spring to minimize the opening area of the variable throttle valve when in a non-excited state, and the control means is provided to ensure that safe steering force is obtained during high-speed running. The safety control device according to claim 1, wherein the safety control device is means for cutting off power supply to the step motor. 5. An abnormality detection means for the vehicle speed sensor and a control means for ensuring safe steering force when driving at high speed.
The safety control device according to any one of claims 1 to 4, characterized in that it is configured by a microcomputer. 6. The safety control device according to any one of claims 1 to 5, which displays an abnormality display when an abnormality is detected in the vehicle speed sensor.