Temperature estimation system

Abstract

To monitor the temperature of an absorber, a temperature estimation system is provided as a means other than a temperature sensor. [Solution] A temperature estimation system 100 is used for monitoring the temperature of a shock absorber equipped with an electromagnetic damper. It comprises a viscosity characteristic calculation unit 121 that calculates the viscosity characteristics of the lubricating oil used in the absorber's speed reducer, and a temperature estimation unit 122 that estimates the temperature of the absorber based on the viscosity characteristics of the lubricating oil. If a failure is detected in the temperature sensor 110 that senses the temperature of the absorber, the system uses the temperature information of the absorber estimated by the temperature estimation unit 122 to monitor whether the temperature of the absorber exceeds the allowable temperature.

Description

[Technical Field]

[0001] The present invention relates to a temperature estimation system. In particular, the present invention relates to a system for use in temperature monitoring of an absorber. [Background Art]

[0002] Conventionally, a shock absorber including an electromagnetic damper as disclosed in Patent Document 1 (hereinafter, may simply be referred to as an absorber) is known. This type of electromagnetic damper generally comprises an outer cylinder, a screw shaft coaxially disposed inside the outer cylinder, a nut that is displaceable along the stroke direction within the outer cylinder and threadably engaged with the screw shaft, and an electric motor connected to the screw shaft. When the electric motor rotates to relatively displace the screw shaft and the nut as the absorber expands and contracts in accordance with the road surface profile while the vehicle is traveling, an induced electromotive force is generated, thereby generating a damping force against the expansion and contraction. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2016-109288 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2009-19690 [Summary of the Invention] [Problems to be Solved by the Invention]

[0004] Generally, in absorbers, energy absorbed during expansion and contraction while the vehicle is traveling is converted into heat, so the temperature thereof tends to increase, and temperature control is required to ensure that the temperature does not exceed an allowable temperature.

[0005] As means for this temperature control, it is conceivable to attach a temperature sensor to the absorber and perform temperature monitoring using the temperature sensor. However, there is a concern that if the temperature sensor fails, temperature monitoring can no longer be performed.

[0006] The present invention has been made in view of the above, and its objective is to provide a temperature estimation system for monitoring the temperature of an absorber, using means other than a temperature sensor. [Means for solving the problem]

[0007] The present invention provides a solution for achieving the above objectives, which relates to a temperature estimation system for estimating the temperature of an absorber in which lubricating oil is used in the gearbox. This temperature estimation system is characterized by comprising a viscosity characteristic calculation unit that calculates the viscosity characteristics of the lubricating oil, and a temperature estimation unit that estimates the temperature of the absorber based on the viscosity characteristics of the lubricating oil calculated by the viscosity characteristic calculation unit.

[0008] The lubricating oil used in the speed reducer portion of the shock absorber changes viscosity depending on the temperature (temperature of the shock absorber). Taking advantage of this, this solution uses a viscosity characteristic calculation unit to calculate the viscosity characteristics of the lubricating oil, and a temperature estimation unit to estimate the temperature of the shock absorber based on these viscosity characteristics. This provides a system for monitoring the temperature of the shock absorber that has not been available before. [Effects of the Invention]

[0009] The present invention includes a viscosity characteristic calculation unit that calculates the viscosity characteristics of the lubricating oil used in the speed reducer portion of the absorber, and a temperature estimation unit that estimates the temperature of the absorber based on these viscosity characteristics of the lubricating oil. This makes it possible to provide a temperature estimation system that can monitor the temperature of the absorber as a means other than a temperature sensor. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view showing a part of the structure of an absorber according to an embodiment. [Figure 2]Figure 2(a) is a block diagram showing the schematic configuration of the temperature estimation system according to the embodiment, and Figure 2(b) is a diagram showing an example of the relationship between the viscosity term of the lubricating oil and the motor speed at a predetermined temperature. [Figure 3] This is a flowchart illustrating the procedure for temperature monitoring using a temperature estimation system. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the present invention will be described based on the drawings. This embodiment describes the case in which the present invention is applied as a system for estimating the temperature of an absorber for an automobile (vehicle) equipped with an electromagnetic damper.

[0012] - Absorber configuration - Before describing the temperature estimation system, let's briefly explain some of the components of the absorber, which is the object of temperature monitoring.

[0013] Figure 1 is a cross-sectional view showing a part of the configuration of the absorber 1 according to this embodiment (configuration of only the telescopic portion). As shown in Figure 1, the absorber 1 is equipped with an actuator 2, which comprises a ball screw mechanism 3 comprising a screw rod 31 and a nut 32 that screws onto the screw rod 31, and a rotational drive unit 4.

[0014] The rotary drive unit 4 comprises an electric motor 41 and a reduction gear (reducer portion in this invention) 42 housed within a casing. Figure 1 shows a configuration in which the electric motor 41 and the reduction gear 42 are arranged coaxially, vertically, but is not limited to this. For example, the drive shaft of the electric motor 41 and the rotation shaft (output shaft) of the reduction gear 42 may not be located coaxially. As is well known, the reduction gear 42 is configured to perform a reduction operation by combining multiple gears, and lubricating oil (grease) is applied between each gear. The rotary drive unit 4 is housed in a motor case 43, and the flange portion 43a of the motor case 43 is fixed to the upper surface of the mounting portion 5 on the vehicle body side. The flange portion 61a of the inner tube 61 is fixed to the flange portion 43a of the motor case 43. In this way, the inner tube 61 is connected to the mounting portion 5 via the motor case 43. The upper end of the screw rod 31 is connected to the rotating shaft 44 of the reduction gear 42, which is connected to the drive shaft of the electric motor 41. In other words, the screw rod 31 is arranged inside the inner tube 61 in a manner that extends the rotating shaft 44, and is configured to rotate in conjunction with the operation of the electric motor 41.

[0015] Meanwhile, the nut 32 is fixedly supported at the upper end of the nut support cylinder 62a, which is connected to the inner bottom of the outer tube 62, while screwed onto the threaded rod 31. The lower end of the outer tube 62 is connected to the lower arm 7 via the mounting member 62b.

[0016] With this configuration, when the upper part of the spring (vehicle side) and the lower part of the spring (wheel side) move closer together or further apart, the outer tube 62 and the inner tube 61 are able to move relative to each other in the direction along the axis. Along with this relative movement, the screw rod 31 and the nut 32 move relative to each other in the direction along the axis, and the screw rod 31 rotates relative to the nut 32. The electric motor 41 is capable of applying rotational torque to the screw rod 31, and this rotational torque is capable of generating a resistance force that prevents the relative movement (stroke movement) between the upper part of the spring and the lower part of the spring. By making this resistance force act as a damping force against the stroke movement between the upper part of the spring and the lower part of the spring, the actuator 2 functions as an absorber (which can also be called a damper).

[0017] -Temperature Estimation System- Next, the temperature estimation system will be described. The temperature estimation system described below is provided in each suspension system of each wheel of the automobile, but below, the temperature estimation system provided in the suspension system of one wheel will be described as representative. In this invention, the temperature estimation system may be provided in the suspension systems of all wheels, or it may be provided in the suspension systems of some wheels.

[0018] Fig. 2(a) is a block diagram showing a schematic configuration of a temperature estimation system 100 according to the present embodiment. As shown in Fig. 2(a), the temperature estimation system 100 includes a temperature sensor 110, a temperature estimation unit 120, a temperature sensor failure detection unit 130, an absorber temperature determination unit 140, and a temperature monitoring unit 150. The system also includes various sensors such as a motor angular velocity sensor 160, a motor torque sensor 170, an outside air temperature sensor 180, and a database DB storing a map described later. Each of these devices is connected to enable mutual communication via an in-vehicle network such as CAN (Controller Area Network). Note that the temperature estimation unit 120, the temperature sensor failure detection unit 130, the absorber temperature determination unit 140, and the temperature monitoring unit 150 may each be configured by separate ECUs, or these functional units may be implemented by a computer program inside a single ECU.

[0019] The temperature sensor 110 is provided at a predetermined position of the absorber 1 (for example, a position near the speed reducer 42 on the outer surface of the motor case 43) and detects the temperature of the absorber 1. The temperature sensor 110 transmits information on the detected temperature of the absorber 1 to the absorber temperature determination unit 140.

[0020] The temperature estimation unit 120 includes a viscosity characteristic calculation unit 121 and a temperature estimation unit 122 as functional units implemented by a stored computer program.

[0021] The viscosity characteristic calculation unit 121 is a functional unit that calculates the viscosity characteristic of lubricating oil in the speed reducer 42 of the absorber 1. The calculation of the viscosity characteristic of lubricating oil performed by the viscosity characteristic calculation unit 121 will be described below.

[0022] The temperature estimation unit 120 is connected to a motor angular velocity sensor 160 that detects the rotational speed (angular velocity) of the electric motor 41, and a motor torque sensor 170 that detects the motor torque of the electric motor 41. As a result, the temperature estimation unit 120 receives information on the angular velocity of the electric motor 41 detected by the motor angular velocity sensor 160, and information on the motor torque of the electric motor 41 detected by the motor torque sensor 170. The viscosity characteristic calculation unit 121 uses this input information on the angular velocity of the electric motor 41 and the motor torque to calculate the viscosity characteristics of the lubricating oil in the reduction gear 42. Note that the angular velocity and motor torque of the electric motor 41 are not limited to those detected by sensors, but may be calculated from various control parameters of the vehicle.

[0023] The viscosity characteristics of the lubricating oil are calculated using the angular velocity, angular acceleration, and motor torque of the electric motor 41, according to the following equation (1). The angular acceleration of the electric motor 41 is calculated, for example, by differentiating the angular velocity.

[0024]

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[0025] The temperature estimation unit 122 estimates the temperature of the absorber 1 based on the viscosity characteristics (viscosity characteristics of the lubricating oil in the reducer 42 of the absorber 1: viscosity term) calculated by the viscosity characteristic calculation unit 121.

[0026] Specifically, the relationship between the viscosity term of the lubricating oil and the motor speed (angular velocity of the electric motor 41) is mapped for each temperature of the absorber 1 to create a set of maps, which are then stored in a database DB. Then, a map is extracted that matches or approximates the relationship between the viscosity term of the lubricating oil obtained by equation (1) and the angular velocity of the electric motor 41 detected by the motor angular velocity sensor 160, and the temperature of the absorber 1 in that map is estimated as the current temperature of the absorber 1 (temperature estimate). Figure 2(b) shows an example of the relationship between the viscosity term of the lubricating oil and the motor speed (angular velocity) at a predetermined temperature. In other words, since the relationship between the viscosity term of the lubricating oil and the motor speed differs depending on the temperature of the absorber 1, the temperature of the map extracted as matching or approximating the relationship between the viscosity term of the lubricating oil obtained by equation (1) and the angular velocity of the electric motor 41 detected by the motor angular velocity sensor 160 at the present time becomes the temperature estimate of the absorber 1.

[0027] Furthermore, in order to ensure the reliability of the temperature estimate of the absorber 1, the temperature estimation unit 122 compares the ambient temperature detected by the ambient temperature sensor 180 with the temperature estimated by the temperature estimation unit 120' provided in the other wheels (other suspension systems) (temperature estimates of the other wheels). Based on these, it determines whether the error in the temperature estimate of the absorber 1 is within an acceptable range, and if it is within an acceptable range, it confirms the temperature estimate of the absorber 1. This acceptable range is predetermined by experiments and simulations.

[0028] The temperature sensor failure detection unit 130 detects whether the temperature sensor 110 is faulty by combining the temperature estimate of the absorber 1 estimated by the temperature estimation unit 122, the temperature estimate of the other wheel's temperature estimation unit 120', and the ambient temperature detected by the ambient temperature sensor 180. In other words, if the temperature information transmitted from the temperature sensor 110 is significantly different from the temperature estimate of the absorber 1 estimated by the temperature estimation unit 122, the temperature estimate of the other wheel's temperature estimation unit 120', or the ambient temperature detected by the ambient temperature sensor 180, it is determined that the temperature sensor 110 is faulty.

[0029] The absorber temperature determination unit 140 receives temperature information of absorber 1 input from temperature sensor 110 and an estimated temperature value of absorber 1 input from temperature estimation unit 120. If the temperature sensor failure detection unit 130 determines that temperature sensor 110 is faulty, the absorber temperature determination unit 140 adopts the estimated temperature value of absorber 1 (determining this estimated temperature value as the temperature of absorber 1) and outputs this estimated temperature value to the temperature monitoring unit 150. If the temperature sensor failure detection unit 130 determines that temperature sensor 110 is not faulty, the absorber temperature information of absorber 1 input from temperature sensor 110 is adopted (determining this temperature as the temperature of absorber 1) and outputs this temperature information to the temperature monitoring unit 150.

[0030] The temperature monitoring unit 150 is a functional unit that determines whether the temperature of the absorber 1, determined by the absorber temperature determination unit 140, exceeds the allowable temperature. This allowable temperature is predetermined by experiments or simulations. If the temperature monitoring unit 150 determines that the temperature of the absorber 1 does not exceed the allowable temperature, the operation of the absorber 1 (operation that generates damping force by the electric motor 41) is continued. However, if the temperature of the absorber 1 exceeds the allowable temperature, the operation of the absorber 1 is stopped.

[0031] -Temperature monitoring operation- Next, we will describe the temperature monitoring operation performed using the temperature estimation system 100 configured as described above. Figure 3 is a flowchart illustrating the procedure for the temperature monitoring operation according to this embodiment.

[0032] First, in step ST1, various pieces of information necessary to estimate the temperature of absorber 1 are acquired and calculated. For example, motor angular velocity, motor torque, and ambient temperature are acquired, and motor angular acceleration is calculated.

[0033] In step ST2, the viscosity term of the lubricating oil is calculated using the acquired and calculated information and the aforementioned formula (1).

[0034] Subsequently, in step ST3, the temperature of the absorber 1 is estimated. As described above, this estimation operation involves mapping the relationship between the viscosity term of the lubricating oil and the motor speed (angular velocity of the electric motor 41) for each temperature of the absorber 1, creating a group of maps, and storing them. A map that matches or approximates the relationship between the viscosity term of the lubricating oil obtained by equation (1) and the angular velocity of the electric motor 41 detected by the motor angular velocity sensor 160 is extracted, and the temperature of the absorber 1 in that map is estimated as the current temperature of the absorber 1 (temperature estimate).

[0035] In step ST4, a fault detection operation for the temperature sensor 110 is performed. Specifically, the temperature estimate of absorber 1 estimated by the temperature estimation unit 122, the temperature estimate of the other wheels provided by the temperature estimation unit 120', and the ambient temperature detected by the ambient temperature sensor 180 are combined to detect whether or not the temperature sensor 110 is faulty.

[0036] If the temperature sensor 110 is not malfunctioning and a NO determination is made in step ST5, the process moves to step ST6, where the temperature information of the absorber 1 input (sensed) from the temperature sensor 110 is adopted. On the other hand, if the temperature sensor 110 is malfunctioning and a YES determination is made in step ST5, the process moves to step ST7, where the temperature estimated by the temperature estimation unit 120 is adopted as the temperature of the absorber 1.

[0037] In step ST8, it is determined whether the temperature of the absorber 1 (the temperature of the absorber 1 input from the temperature sensor 110 if the temperature sensor 110 is not faulty, or the temperature of the absorber 1 estimated by the temperature estimation unit 120 if the temperature sensor 110 is faulty) is below the allowable temperature of the absorber 1.

[0038] If the temperature of absorber 1 is below the allowable temperature and a YES determination is made in step ST8, the process proceeds to step ST9, and absorber 1 continues to operate. On the other hand, if the temperature of absorber 1 exceeds the allowable temperature and a NO determination is made in step ST8, the process proceeds to step ST10, and a fail-safe process is performed to stop the operation of absorber 1.

[0039] -Effects of the embodiment- As described above, in this embodiment, the viscosity characteristic calculation unit 121 calculates the viscosity characteristics of the lubricating oil used in the reducer 42 of the absorber 1, and the temperature estimation unit 122 estimates the temperature of the absorber 1 based on the viscosity characteristics of the lubricating oil. This provides a temperature estimation system 100 that can monitor the temperature of the absorber 1 as a means other than the temperature sensor 110. As a result, even if the temperature sensor 110 fails, the temperature of the absorber 1 can be properly monitored.

[0040] -Other Embodiments- Furthermore, the present invention is not limited to the embodiments described above, and all modifications and applications are possible within the scope of the claims and equivalents thereof.

[0041] For example, the above embodiment described an application of the present invention as a system for estimating the temperature of an absorber 1 for an automobile equipped with an electromagnetic damper. However, the present invention is not limited to this and can also be applied as a system for estimating the temperature of other absorbers.

[0042] Furthermore, in the above embodiment, the temperature of the absorber 1 was monitored by adopting the estimated temperature of the absorber 1 only when it was determined that the temperature sensor 110 was malfunctioning. The present invention is not limited to this, and even when it is determined that the temperature sensor 110 is not malfunctioning, the temperature of the absorber 1 may be monitored by adopting the estimated temperature of the absorber 1 based on other conditions.

[0043] Furthermore, in the above embodiment, the case was described as one in which the temperature of the absorber 1 is detected by a temperature sensor 110 and the temperature of the absorber 1 is estimated by a temperature estimation unit 120, and then one of the two is adopted for temperature monitoring of the absorber 1. The present invention is not limited to this, and the temperature of the absorber 1 may be monitored using only the temperature estimated by the temperature estimation unit 120, without the provision of a temperature sensor 110. [Industrial applicability]

[0044] The present invention is applicable to a temperature estimation system used for temperature monitoring of an absorber equipped with an electromagnetic damper. [Explanation of symbols]

[0045] 1…Absorber 42…Gear reducer (gear reducer section) 100…Temperature estimation system 121...Viscosity characteristic calculation section 122...Temperature estimation section

Claims

[Claim 1] A temperature estimation system for estimating the temperature of an absorber in which lubricating oil is used in the gearbox section, A viscosity characteristic calculation unit that calculates the viscosity characteristics of the lubricating oil, A temperature estimation system characterized by comprising: a temperature estimation unit that estimates the temperature of the absorber based on the viscosity characteristics of the lubricating oil calculated by the viscosity characteristic calculation unit.

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