JPH0118680B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention controls the steering force in response to changes in vehicle speed by controlling the opening degree of a variable throttle valve provided in a pressure fluid conduit using a step motor. The present invention relates to a safety control device for a speed-sensitive power steering system, and more particularly to a device that ensures safety during high-speed driving by monitoring and controlling a step motor. (Prior Art) As this type of speed-sensitive power steering device, the applicant of the present application proposed the device of Utility Model Application No. 167828/1983.
As shown in FIG. 1, this flow control system includes a variable throttle valve 8 and a fixed throttle valve 9 arranged in parallel between a hydraulic pump 7 and a power steering unit 10.
The variable throttle valve 8 is controlled by a step 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. In the figure, 11 is the hydraulic pump 7
This is a flow rate control valve that 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 is a pressure relief valve for 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. For details, see the above-mentioned
Since it is described in the specification of No. 53-167828, 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. It is input to an F-V converter (frequency-voltage converter) 2 consisting of a DA converter (digital-to-analog converter), etc., where it is converted into a voltage proportional to the vehicle speed, and then sent to the Schmidt circuit via a home return circuit 3. Enter group 4. Each Schmitt circuit compares preset voltages V ₁ , V _{2 .} . . Exclusive
A distribution circuit 5 consisting of an OR circuit group, an OR circuit, and an amplifier group receives the output of the Schmitt circuit and determines which of the plurality of excitation coils A, B, and C of the step motor 6 is to be excited. That is, in response to changes in the output of the vehicle speed sensor 1, the step motor 6
The rotation angle of the variable throttle valve 8 is controlled to control the throttle amount of the variable throttle valve 8, and since the details are described in the above specification, a 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 a 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 0V to the maximum voltage, and the variable throttle valve 8
The rotor shaft 6a is rotated to the control origin position where the diaphragm opening area is maximized. 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, if there is a failure or malfunction of the step motor or a failure of the driver circuit of the step motor, there is a drawback that the steering force cannot be assisted in accordance with the vehicle speed, resulting in unstable steering. This invention eliminates the cause of unstable steering during high-speed driving by operating the variable throttle to a position where a safe steering force can be obtained for high-speed driving at the same time that an abnormality occurs in the step motor system. This is the purpose. (Means for Solving the Problems) The means for eliminating the feeling of steering anxiety provided by the present invention detects an abnormality in the step motor system by reading the coil end voltage of the excitation coil, and when an abnormality is detected, the step motor system This safety control device minimizes the opening area of the variable throttle valve through the action of the return spring by cutting off the power supply to the variable throttle valve, 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 step motor system during high-speed running, it is possible to prevent the steering force from becoming too light, and it is possible to eliminate the feeling of instability during high-speed running. (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, as a monitoring means for the step motor of the present invention, 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 that includes a central processing unit CPU and a read-only memory in one package.
It is a commercially available product containing ROM, random access memory RAM, and a predetermined number of inputs IA ₀ , INT, IB ₀ ...IB ₃ , outputs OA ₀ , OA ₁ ...OA ₃ , OB ₀ , OB _1, etc. Well, said ROM,
The program described below is embedded in 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. 4 becomes operational, but the reset terminal of the microcomputer 14
A signal of logic level 1 is momentarily applied to the reset terminal by the CR differentiator circuit 18 connected to RESET. As a result, each output port of the microcomputer 14 OA ₀ , OA ₁ , OA ₂ , OA ₃ , OB ₀ ,
OB ₁ is all turned off and ROM
Execution of the instruction starts from 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 the 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 in Figure 7B is
It is shown in Figure E. That is, when executing the step motor drive subroutine, it is determined whether the rotation direction is normal or reverse based on the previous control code. Table 1 shows 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 into IB ₀ , and this is to constitute a comparison means for determining step motor abnormality according to the present invention. For example, if 1001 is output as the control command signal from the output ports OA ₃ to _{OA 0} , and the monitoring signal read by IB ₃ to IB ₀ is 0110, the microcomputer 14
The connection between the driver circuit 15 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 normal.
This is because the determination is made by the comparison means configured within the microcomputer 14. 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. Then, whether the input terminal _IA0 of the microcomputer 14 connected to the output of the vehicle speed sensor 1 is at a logic level of 1 or 0 is checked. 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. 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 is 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. The program then moves to the step motor drive subroutine, 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. Next, as a control means to ensure safety, 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 a step motor monitoring means.
This is an example in which the rotation sensor 20 is directly connected to the rotor shaft 6a of the step motor 6, and a rotary encoder or other conceivable means may be employed. This is provided to check whether the instruction of the rotational position of the step motor 6 is correct. This is to read 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. be. At this time, compared to reading the coil end voltage, the step motor 6
It can also detect out-of-step and mechanical failures. 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 greater than the specified value, and if YES, setting the step 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 .
...I set up an IC _o , and set some predetermined flow characteristics,
It is also possible to provide a mode selection circuit 21 that allows the user or end user to arbitrarily select according to their feeling using selection switches S ₀ , S ₁ . . . S _o . The flowchart at that time is the first
Shown in Figure 1. That is, it may be combined with the vehicle speed comparison routine shown in FIG. 7D. Furthermore, although this invention does not necessarily require the use of a microcomputer as in the above embodiment,
By using a microcomputer to control the drive of the step motor, detect abnormalities in the step motor, and control to provide safe steering force, safety control can be performed with high reliability without being affected by fluctuations in power supply voltage or temperature changes. can be done. (Effects of the Invention) As detailed above, according to the present invention, the step motor is monitored by reading the coil end voltage of each excitation coil of the step motor, and the read coil end voltage signal When an abnormality in the step motor is detected based on the comparison result with the control command signal corresponding to the vehicle speed given to the step motor, the power supply to the step motor is cut off, and the variable throttle valve is set to high speed by the action of the return spring. Since the steering force is narrowed down to the position where a safe steering force can be obtained for driving, that is, the position where the opening area is minimized, even if an abnormality occurs during high-speed driving, the situation where the steering force becomes too light can be effectively prevented. Therefore, the previously unresolved feeling of steering uneasiness when driving at high speeds is completely resolved, and it is also possible to prevent excessive turning of the steering wheel when driving at high speeds.・The safety and stability of a speed-sensitive power steering system can be achieved over the entire range up to high speeds. Furthermore, since a microcomputer can be used as the safety control device of the present invention, by adopting a commercially available device as is, the cost can be significantly reduced. The installation space can be small as well.

[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.
10 is a flowchart of a routine incorporated into a microcomputer, FIGS. 8 and 9 are flowcharts of other embodiments, respectively.
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 throttle,
10...Power steering unit, 14...Microcomputer, 15...Driver circuit, 16
...Error indicator, 17...Switching circuit, 18...
CR differentiation circuit, 19...Coil end voltage reading circuit, 2
0... Rotation sensor, 21... Mode selection circuit.

Claims (1)

[Scope of Claims] 1. A speed-sensitive power rudder in which the opening degree of a variable throttle valve provided in a pressure fluid pipe is controlled by a step motor in response to changes in vehicle speed, and the steering force is controlled in accordance with vehicle speed. The apparatus comprises a step motor monitoring means, a comparison means for determining whether or not there is an abnormality in the step motor, and a control means for controlling the step motor, and the monitoring means controls each excitation coil of the step motor. a coil end voltage reading circuit for reading a coil end voltage; the comparing means compares the coil end voltage signal read by the monitoring means with a control command signal corresponding to a vehicle speed given to a driver circuit of the step motor; means for determining that the step motor is abnormal when there is a logical contradiction in the results; and the control means is for cutting off power supply to the step motor when the comparison means determines that the step motor is abnormal; . A safety control device characterized in that the opening area of the variable throttle valve is minimized by the action of a return spring when all of the excitation coils are de-energized. 2. The safety control device according to claim 1, wherein the comparison means and the control means are configured by a microcomputer. 3. The safety control device according to claim 1 or 2, which displays an abnormality display when determining an abnormality in the step motor.