JPH03132472A - Power steering device with motor-driven pump - Google Patents

Abstract

PURPOSE:To prevent overheat of an electric motor to drive a pump by calculating the temp. of the motor on the basis of specific temp. characteristic and the saturated temp. characteristic, and by controlling the motor according to the comparison of this calculational value with the set value followed by judgement. CONSTITUTION:The load current flowing in an electric motor 1 which drives an electric pump is detected by a means 2. A means 3 stores in memory the temp. characteristic which relates specifically the load current with the temp. change amount corresponding to the heat emission amount per unit time generat ed by the load current. A means 4 stores in memory the saturated temp. charac teristic which specifically relates the load current with the saturated temp. reached by the electric motor 1 with the heat emission associate with the load current. On the other hand, the current temp. of the motor 1 is calculated by a means 5 on the basis of the load current and the saturated temp., and this temp. is compared with the upper limit value and lower limit value followed by judgement by a means 6. According to the result from judgement a means 7 makes control so as to rotate or stop the motor 1.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a power steering device for an automobile using an electric pump.

[Prior art]

In general, a power steering system for an automobile connects a steering shaft and a pinion shaft with an elastic member (torsion bar), and a servo valve operates based on the relative rotation between the steering shaft and pinion shaft caused by the torsion of this elastic member. This controls the supply and discharge of working fluid to the power cylinder that provides assist force. In other words, the elastic member twists in proportion to the magnitude of the manual torque input from the steering wheel of the vehicle to the steering shaft, causing the steering shaft and pinion shaft to rotate relative to each other, thereby generating assist torque (auxiliary steering force) for steering. This device reduces the required manual torque. The supply of the working fluid to the servo valve is accomplished by rotating the pump using engine power.

[Problem to be solved by the invention]

Here, in cars where the engine is not mounted on the front side (for example, midship cars), there is a considerable distance between the engine and the steering shaft, etc., and connecting piping over that distance would complicate the configuration and would not be appropriate. . Therefore, as disclosed in Japanese Patent Application Laid-open No. 56-99859, an electric motor is installed near the steering shaft, etc., and an electric pump is used to supply working fluid to the steering shaft, etc. using the motor power. It is conceivable to generate assist torque. However, if a high current continues to flow through the electric motor that makes up the electric pump, for example when the steering wheel is operated continuously at low speeds, there is a risk that the electric motor will overheat and eventually be damaged. There is. The present invention has been made to solve the above-mentioned problems, and its purpose is to provide an electric pump type power steering device that prevents damage to the electric motor in a power steering device using an electric pump. Please provide one piece of equipment.

[Means to solve the problem]

The structure of the invention for solving the above problem is, as shown in the concept in FIG. Current detecting means 2 (!l:) for detecting the load current flowing through the electric motor 1 that drives the pump, and the amount of temperature change corresponding to the load current flowing through the electric motor 1 and the amount of heat generated per unit time caused by the load current. Temperature characteristic storage means 3 stores temperature characteristics that define the relationship between the load current flowing through the electric motor 1 and the saturation temperature at which the electric motor reaches 1 due to the heat generated by the load current. The amount of temperature change with respect to the load current detected by the current detection means 2 is determined from the saturation temperature characteristic storage means 4 storing the saturation temperature characteristics and the temperature characteristics stored in the temperature characteristic storage means 3, If the temperature is below the saturation temperature for the load current determined from the saturation temperature characteristic, add the temperature change amount to the temperature of the electric motor 1,
If the saturation temperature is exceeded, the temperature calculation means 5 calculates the current temperature of the electric motor 1 by subtracting the absolute value of the temperature change amount from the temperature of the electric motor 1; Determined current electric motor 1
temperature determination means 6 that compares the temperature with preset upper and lower limit temperatures and outputs a determination signal, and based on the determination signal output from the temperature determination means 6, rotates the electric motor 1. It is characterized by comprising a motor control means 7 that performs stop control.

[Operation] The current detection means 2 detects the load current flowing through the electric motor 1 that drives the electric pump. On the other hand, the temperature characteristic storage means 3 stores temperature characteristics defining the relationship between the load current flowing through the electric motor 1 and the amount of temperature change corresponding to the amount of heat generated per unit time generated by the load current. Further, the saturation temperature characteristic storage means 4 stores saturation temperature characteristics that define the relationship between the load current flowing through the electric motor 1 and the saturation temperature that the electric motor 1 reaches due to the heat generated by the load current. . Next, the temperature calculation means 5 calculates the amount of temperature change with respect to the load current detected by the current detection means 2 from the temperature characteristics stored in the temperature characteristic storage means 3, and records the temperature of the electric motor 1 as follows. If the temperature is below the saturation temperature for the load current determined from the saturation temperature characteristics, the temperature change amount is added to the temperature of the electric motor 1, and if it exceeds the saturation temperature, the temperature is changed from the temperature of the electric motor 1 to the temperature The current temperature of the electric motor 1 is determined by subtracting the absolute value of the amount of change. Then, the temperature determining means 6 compares the obtained current temperature of the electric motor 1 with preset upper and lower temperature limits and outputs a determination signal. Based on the output judgment signal, the motor control means 7
controls the rotation and stopping of the electric motor 1. [Examples] The present invention will be described below based on specific examples. Figure 'flIJ2 is a configuration diagram showing the configuration of an electric pump type power steering device according to the present invention. Reference numeral 11 is a vehicle speed sensor that detects the vehicle speed of the automobile, and reference numeral 12 is a steering sensor that detects whether the steering wheel 13 is being steered. 14 is a control device, and the control device 14 is a batch IJB.
Power is supplied from the vehicle speed sensor 11 and output signals from the steering sensor 12 are input. Further, P is a pump rotated by an electric motor M,
The electric pump is composed of an electric motor M and a pump P that is integrally provided, and the working fluid sent out from the pump P is supplied to the servo valve 16. Furthermore, the load current flowing through the electric motor M is detected by a current detector 15 serving as current detection means, and its output signal is input to the control device 14. 21 is a gear housing composed of a rack and pinion gear. Reference numeral 22 denotes a power cylinder that generates an auxiliary steering force, and as described above, the supply and discharge of working fluid to the power cylinder 22 is controlled by the servo valve 16, and the steering rods 24 on the left and right of the piston 23 of the power cylinder 22 The ball joint 25 is actuated to rotate a steering wheel (not shown). [
This will be explained with reference to FIG. 5, which is Map 1. First, in step 100, it is determined whether Motor, which is a flag related to control of electric motor M, is set to Motorl for normal control. Here, at the beginning of the control, the electric motor M is set to a flag Motor so that it is normally controlled.
Since the initial value Motor=1, the determination at step 100 is YES, and the process moves to step 102. In step 102, it is determined whether or not the steering wheel 13 is being steered, that is, whether or not the steering sensor 12 is outputting an output signal. When the output signal is output from the steering sensor 12 in step 102 and it is determined that steering is being performed, step 104
The vehicle speed V at that time is read from the vehicle speed sensor 11. Next, the process moves to step 106, and the voltage E to be applied to the electric motor M corresponding to the vehicle speed V read in step 104 is calculated from the characteristic diagram of FIG. 5, which is [map 1]. Next, the process moves to step 108, where the voltage E calculated in step 106 is output to the electric motor M, and the program ends. In this way, the assist torque is controlled to increase as the vehicle speed decreases. Note that if the flag Motor related to the control of the electric motor M is 0 in step 100 described above and the control is deviated from normal control, or if the output signal is not output from the steering sensor 12 in step 102 and there is no steering. In this case, the process moves to step 110, where the voltage E to be applied to the electric motor M is set to 0, and the process moves to the above-mentioned step 108, that is, the electric motor M is stopped. Next, based on the flowchart of FIG. 4 showing the processing procedure of the control device 14 that controls the electric motor M based on the motor temperature, load current 1. And this load current 1. The sixth characteristic diagram [Map 2] shows the relationship between the temperature change amount T when
Fig. 1. Load current flowing through electric motor M. and saturation temperature T
This will be explained with reference to FIG. 7, which is a characteristic diagram [map 3] showing the relationship with 11111M. First, in step 200, a load current 1. is read from the current detector 15. Next, in step 202, the amount of temperature change T with respect to the load current IM read in step 200 is calculated from the characteristic diagram of FIG. 6, which is [map 2]. Next, the process moves to step 204, and from the characteristic diagram of FIG. 7, which is [map 3], the load current 1. Calculate the saturation temperature T III a X for Then, the process moves to step 206, where the saturation temperature T-8 calculated in step 204 and the current pseudo motor temperature M are
TH and it is determined whether T□8≧MTH. If the above inequality holds, the determination in step 206 is YE.
S, the process moves to step 208, and the current motor temperature MTH is determined from the temperature change amount T calculated in step 202 using the following equation. MTH=MTH+TIa On the other hand, if the inequality in step 206 is not satisfied, the determination becomes No, and the process moves to step 210, where the current motor temperature MTH is calculated from the temperature change amount Tyo calculated in step 202 using the following equation. MTH=MTH-T. Note that a predetermined pseudo environmental temperature is set as an initial value for the motor temperature MTH. Then, the process moves to step 212, and it is determined whether the flag MF indicating the normal/abnormal state of the electric motor M is MF=0, which is the normal state. At the beginning of the control, the electric motor M is in a normal state and the flag MF is the initial value MF=O, so the determination in step 212 is YES, and step 214
to move to. In step 214, it is determined whether MTH≦H. That is, step 208 or step 210
The calculated motor temperature MTH is compared with a preset upper limit temperature H at which the electric motor M will not be damaged. If the motor temperature MTH does not exceed the upper limit temperature H, the inequality in step 214 is established, and the electric motor M has not reached a temperature that would cause damage, so the determination is Y.
It becomes ES and this program ends. Then, at the point in time when the inequality MTH≦H no longer holds in step 214 described above (time 1+ in FIGS. 8(a) and (b)), there is a possibility that the electric motor M will overheat and be damaged, and step 214 The determination becomes NO, and the process moves to step 216. Then, the step knob 216 sets a flag MF indicating the normal/abnormal state of the electric motor M to MF=1.
is in an abnormal state. Next, if MF=1 in step 212 described above, the determination is NO and the process moves to step 218. In step 218, it is determined whether M T H≧. That is, step 208 or step 2
The motor temperature MTH calculated in step 10 is compared with a preset lower limit temperature. This lower limit temperature is a temperature at which it can be determined that the overheated electric motor M is sufficiently cooled down and the pump can resume rotation. Then, if the inequality in step 218 is satisfied, the determination is Y.
ES, the process moves to step 220, and the flag Motor related to the control of the electric motor M is set to Stop Motor.
=0. Then, based on the determination in step 100 in the flowchart of FIG. 3 described above, the electric motor M is stopped in order to prevent damage due to overheating. Then, when the electric motor M is stopped, the load current 1 becomes zero, and from the characteristic diagram [map 2] in FIG. 6, the amount of temperature change T at that time becomes a negative value. That is, in the temperature calculation in step 208 or step 210 of FIG. 4, the motor temperature MTH gradually decreases by the temperature change amount T (between time t1 and t2 in FIG. 8(b)). Then, in step 218, the time point when the inequality MTH≧L no longer holds true (time t in FIGS. 8(a) and 8(b))
In 2), the determination is N0, and the process moves to step 222. In step 222, the flag MP of the electric motor M is returned to MF=0, which is a normal state, and the process proceeds to step 224, where the flag Motor related to control of the electric motor M is set to Motor=1, which is normal control. Then, in the flowchart of FIG. 3 mentioned above, the normal control is restored and Motor=1, so the determination in step 100 is Y.
8S, and the processing from step 102 onward is executed in the same manner as described above. Note that the temperature characteristic storage means and the saturation temperature characteristic storage means are constituted by a memory within the control device 14. Further, the temperature calculation means performs steps 208 and 210.
In step 214 and step 21, the temperature determination means
At 8, motor control means are also accomplished at steps 220 and 224. As described above, in the electric pump type power steering device of the present invention, when calculating the pseudo motor temperature MTH of the electric motor M, the actual saturation temperature T f of the electric motor M is calculated.
The rotation of the electric pump is controlled in consideration of f1llk. Then, corresponding to the time chart showing the change in load current 1.4 as shown in FIG. 8(a), the time chart shown in FIG. 8(b)
This is a time chart showing changes in motor temperature MTH with respect to changes in load current IM, as shown in FIG. Here, the voltage E applied to the electric motor M that drives the electric pump is large when the vehicle speed V is low, and becomes smaller as the vehicle speed becomes higher, as shown in the characteristic diagram [Map 1] in Fig. 5. . That is, as the vehicle speed V increases, the load current IN flowing through the electric motor M decreases. Time 1 in FIGS. 8(a) and (b). Up to this point, changes in the motor temperature MTH are shown when the vehicle speed V is constant (low speed) with steering and the load current IN flowing through the electric motor M is constant. Thus, the load current■. is large and the saturation temperature Tffia Since the current does not stop flowing and the electric motor M does not overheat beyond the upper limit temperature H, damage to the electric motor M is prevented. The saturation temperature T□8 shown in the characteristic diagram [Map 3] in Fig. 7
exists for the following reasons. The temperature of the electric motor M is the load current flowing through the electric motor M. The amount of heat generated inside the electric motor M increases in proportion to the square of . As a result, the temperature difference between the electric motor M and the surrounding environment becomes large. The greater the temperature difference, the greater the amount of heat radiated from the electric motor M into the environment. When the temperature of the electric motor M reaches a certain temperature, the amount of heat generated from the electric motor M becomes equal to the amount of heat radiated into the environment. After this point, the temperature of the electric motor M becomes in an equilibrium state and does not change. In other words, this temperature is the load current ■. The above saturation temperature T, which corresponds to It is. Therefore, the saturation temperature T II
a X is load current■. increases in proportion to the square of Note that T in FIGS. 7 and 8(b). , is the simulated environment temperature where the electric motor M is placed. As in the above case, unless the vehicle speed V is low and the steering is not continued for a very long time, the load current flowing to the electric motor M is 1. The saturation temperature T II a 11 at that time will not exceed the upper limit temperature H. That is, as shown after time t2 in FIGS. 8(a) and 8(b), for example, when steering is being performed, the vehicle speed V is constant (medium speed), and the load current IM flowing through the electric motor M is constant. First, the load current ■. The amount of temperature change T is added. Then, when the motor temperature MTH reaches a saturation temperature T1.8 that does not exceed the upper limit temperature H, the temperature change amount T is added or subtracted from the motor temperature MTH based on the comparison result between the motor temperature MTH and the saturation temperature TIIaM. Therefore, the motor temperature MTH is calculated as a value approximately equal to the saturation temperature Tmax. Since the rotation of the electric motor M is controlled based on the calculated motor temperature MTH, there is no problem that the electric pump is stopped unnecessarily even though the electric motor M is not in an overheated state.

【Effect of the invention】

The present invention calculates the amount of temperature change with respect to the load current detected by the current detection means from the temperature characteristics stored in the temperature characteristic storage means, and stores the temperature of the electric motor that drives the electric pump in the saturation temperature characteristic storage means. If the temperature is below the saturation temperature for the load current determined from the saturation temperature characteristics, add the temperature change amount to the temperature of the electric motor, and if it exceeds the saturation temperature, calculate the temperature change from the electric motor temperature. Temperature calculation means that calculates the current temperature of the electric motor by subtracting the absolute value of the quantity, compares the calculated temperature of the electric motor with preset upper and lower temperature limits, and outputs a judgment signal. Since it is equipped with a temperature determination means and a motor control means that controls rotation/stop of the electric motor based on the output determination signal, the saturation temperature for the load current flowing through the electric motor is below a preset upper limit temperature. In this case, the electric motor is controlled to rotate without stopping. On the other hand, if the saturation temperature exceeds the preset upper 11i+ temperature, the electric motor will stop when the temperature exceeds the preset upper limit temperature, and resume rotation when it falls below the preset lower limit temperature. Rotation/stop control is executed. Therefore, the electric motor that drives the electric pump will not stop unnecessarily and the assist torque will be lost, causing discomfort or discomfort to the driver, and there is no risk of the electric motor overheating and causing damage. In some cases, this has the effect of ensuring a fail-safe operation and stopping the electric motor.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the concept of the present invention. FIG. 2 is a configuration diagram showing the configuration of an electric pump type power steering device according to a specific embodiment of the present invention. 3 and 4 are flowcharts showing the processing procedure of the control device according to the same embodiment. FIG. 5 is a characteristic diagram showing the relationship between vehicle speed V and voltage E according to the same embodiment. FIG. 6 is a characteristic diagram showing the relationship between motor current IM and temperature T according to the same embodiment. FIG. 7 is a characteristic diagram showing the relationship between motor current I, 4 and saturation temperature T□28 according to the same embodiment. FIG. 8(a) shows the motor current ■ according to the same example. A time chart showing changes in . FIG. 8(b) shows the motor current 1 in FIG. 8(a). 2 is a time chart showing changes in motor temperature MTH with respect to changes in . 1 4 6 1 5 Vehicle speed sensor 1 Control device I5 Servo valve gear housing ball joint battery M Electric motor ■ Steering sensor current detector 7 Reservoir tank 22 Power cylinder P Pump

Claims (1)

[Scope of Claims] A power steering device that controls assist torque applied to a steering shaft or the like by an electric pump mounted on an automobile, comprising current detection means for detecting a load current flowing through an electric motor that drives the electric pump; Temperature characteristic storage means storing temperature characteristics defining a relationship between a load current flowing through the electric motor and a temperature change amount corresponding to the amount of heat generated per unit time generated by the load current; and a load current flowing through the electric motor. and a saturation temperature characteristic storage means that stores a saturation temperature characteristic that defines the relationship between the electric motor and the saturation temperature that the electric motor reaches due to the heat generated by the load current; The amount of temperature change with respect to the load current detected by the detection means is determined, and if the temperature of the electric motor is equal to or lower than the saturation temperature with respect to the load current determined from the saturation temperature characteristic, the temperature change amount is added to the temperature of the electric motor. temperature calculation means for calculating the current temperature of the electric motor by adding the temperature and subtracting the absolute value of the temperature change amount from the temperature of the electric motor when the saturation temperature is exceeded; temperature determination means for comparing the obtained current temperature of the electric motor with preset upper and lower temperature limits and outputting a determination signal; and based on the determination signal output from the temperature determination means, the electric motor An electric pump type power steering device comprising: a motor control means for controlling rotation and stopping of the electric pump type power steering device.