JP2020006833A - Vehicle control device - Google Patents

Abstract

To provide a vehicle control device that can be simply configured to monitor overheat of hydraulic fluid.SOLUTION: An ECU computes drive torque Tp based on discharge pressure of a pump (step 102) and multiplies the drive torque Tp by the number of rotations N and thus calculates consumed power W of the pump (=Tp×N) (step 103), and calculates the sum of consumed power W calculated in calculation cycles in a predetermined period as the amount of heat generation J of the pump (step 104). Next, the ECU calculates estimated hydraulic fluid temperature Oe based on the calculated amount of heat generation J (step 105) and determines whether the estimated fluid temperature Oe exceeds a specified temperature Oth (step 106). Then, when the estimated fluid temperature Oe is higher than the specified temperature Oth, the ECU determines that the hydraulic fluid is overheated (step 106: YES) and decreases the number of rotations N so as not to be lower than a lower limit and thus controls operation of an internal combustion engine (step 107).SELECTED DRAWING: Figure 3

Description

  The present invention relates to a vehicle control device that controls a hydraulic power steering device.

  In general, a hydraulic power steering apparatus includes a pump that operates by driving an internal combustion engine (engine), a hydraulic cylinder whose interior is partitioned into first and second hydraulic chambers by a piston, and hydraulic oil to the hydraulic cylinder based on steering operation. And a control valve (rotary valve) for controlling the supply and discharge of air. Then, according to the switching state of the control valve, the operating oil is supplied from the pump to one of the first and second hydraulic chambers in the hydraulic cylinder via a supply oil path connecting the pump and the hydraulic cylinder, Hydraulic oil is discharged from the other side via a discharge oil passage connecting the hydraulic cylinder and the reservoir tank, thereby applying an assist force for assisting steering to the steering mechanism.

  Incidentally, some pumps include an internal relief valve for maintaining the discharge pressure at a predetermined pressure or lower. Thereby, for example, when the discharge pressure of the pump increases due to the state in which the control valve is fully closed and the hydraulic oil recirculates in the pump from the discharge side to the suction side of the pump, the discharge pressure is reduced. It is kept below the specified pressure. However, if the period during which the hydraulic oil is recirculated in the pump becomes long, the hydraulic oil in the pump may overheat, and the pump may become hot.

  In view of this point, for example, in the hydraulic power steering device described in Patent Document 1, an external relief valve that holds the discharge pressure of the pump at a specified pressure or less is provided between the supply oil passage and the discharge oil passage in parallel with the control valve. Are provided. In this configuration, for example, when the control valve is fully closed and the discharge pressure of the pump is increased, the external relief valve is opened, and the hydraulic oil is discharged through the external relief valve without reflux in the pump. Since the refrigerant is recirculated through a path including a cooler pipe provided in the oil path, overheating of the hydraulic oil can be suppressed.

JP 2007-161234 A

  However, in the configuration of Patent Literature 1, for example, when the situation where the rotation speed of the internal combustion engine becomes extremely high in an attempt to escape from the stack state in which the driving wheels idle on a snowy road or the like continues, the external relief valve is opened. As a result, the pump can be prevented from becoming hot, but the temperature of the entire hydraulic oil flowing through the hydraulic circuit of the power steering device increases, which may affect functional components other than the pump. Therefore, it is conceivable to monitor the oil temperature of the hydraulic oil in order to take some countermeasures according to the rise in the oil temperature.However, for example, when a temperature sensor for detecting the oil temperature is provided, the configuration is complicated. turn into.

  An object of the present invention is to provide a vehicle control device that can monitor overheating of hydraulic oil with a simple configuration.

  A vehicle control device that solves the above problems includes a pump that operates by driving an internal combustion engine, a hydraulic cylinder that generates an assist force based on the hydraulic pressure of hydraulic oil discharged from the pump, and the hydraulic pressure that is based on a steering operation. A hydraulic power steering device having a control valve for controlling the supply and discharge of hydraulic oil to and from a cylinder is controlled, and the hydraulic power steering device is estimated based on a load state quantity indicating a load of the pump and a rotation speed of the internal combustion engine. The overheating of the hydraulic oil is determined using the calorific value of the pump.

  According to the above configuration, for example, a temperature sensor is provided in order to determine whether the hydraulic oil is overheated using the heat value of the pump estimated based on the load state amount of the pump and the rotation speed of the internal combustion engine. As compared with the case, the overheating of the hydraulic oil can be monitored with a simple configuration.

In the above-described vehicle control device, it is preferable that the load state amount is indicated as a value corresponding to a driving torque of the pump.
According to the above configuration, the calorific value of the pump can be appropriately estimated by calculating the power consumption (work) of the pump based on the value corresponding to the driving torque of the pump and the rotation speed of the internal combustion engine.

In the above-described vehicle control device, it is preferable that the load state amount is indicated as a value corresponding to a discharge pressure of the pump.
According to the above configuration, the calorific value of the pump can be appropriately estimated by calculating the power consumption (work) of the pump based on the value corresponding to the discharge pressure of the pump and the rotational speed of the internal combustion engine.

In the above-described vehicle control device, when it is determined that the hydraulic oil is overheated, it is preferable to reduce the rotation speed of the internal combustion engine.
According to the above configuration, the amount of heat generated by the pump is reduced by reducing the rotation speed of the internal combustion engine, so that an increase in oil temperature can be suitably suppressed.

  According to the present invention, overheating of hydraulic oil can be monitored with a simple configuration.

FIG. 1 is a schematic configuration diagram of a hydraulic power steering device. 4 is a graph showing a relationship between a steering torque and a discharge pressure of a pump. 5 is a flowchart showing a processing procedure of monitoring overheating of hydraulic oil by an ECU. (A) is a graph showing an example of a change in the estimated oil temperature of hydraulic oil, (b) is a graph showing an example of a change in the rotational speed of the internal combustion engine, and (c) is a graph showing an example of a change in the discharge pressure of the pump. .

Hereinafter, an embodiment of a vehicle control device will be described with reference to the drawings.
As shown in FIG. 1, the hydraulic power steering device 1 includes a steering mechanism 4 for turning a steered wheel 3 based on an operation of a steering wheel 2 by a driver, and an assist force for assisting the steering mechanism 4 in steering. And a hydraulic mechanism 5 for applying.

  The steering mechanism 4 includes a steering shaft 11 to which the steering wheel 2 is fixed, and a rack shaft 12 that reciprocates in the axial direction according to the rotation of the steering shaft 11. A pinion shaft 13 that meshes with the rack shaft 12 is provided at the tip of the steering shaft 11 so as to be integrally rotatable.

  The rack shaft 12 and the pinion shaft 13 are arranged at a predetermined crossing angle, and the rack and gear 12 The pinion mechanism 14 is configured. A tie rod 15 is connected to both ends of the rack shaft 12, and a tip of the tie rod 15 is connected to a knuckle (not shown) to which the steered wheels 3 are attached. Therefore, in the hydraulic power steering device 1, the rotation of the steering shaft 11 accompanying the steering operation is converted into the axial movement of the rack shaft 12 by the rack and pinion mechanism 14, and this axial movement is transmitted to the knuckle via the tie rod 15. Thus, the steered angle of the steered wheels 3, that is, the traveling direction of the vehicle is changed.

  The hydraulic mechanism 5 includes a pump 21 serving as a hydraulic pressure supply source, a resin reservoir tank 22 in which hydraulic oil is stored, a hydraulic cylinder 23 for providing an assist force based on hydraulic pressure, and a hydraulic cylinder 23 for supplying hydraulic oil to the hydraulic cylinder 23. A control valve 24 for controlling the supply and discharge and oil passages L1 to L5 connecting the pump 21, the reservoir tank 22, the hydraulic cylinder 23 and the control valve 24 are provided. The hydraulic mechanism 5 is provided in parallel with the control valve 24 between a supply oil passage L1 connecting the pump 21 and the control valve 24 and a discharge oil passage L2 connecting the reservoir tank 22 and the control valve 24. An external relief valve 25 is provided.

  As the pump 21, an engine-driven pump driven by rotation of a crankshaft of an internal combustion engine (engine) 31 is employed. The operation of the internal combustion engine 31 is controlled by an ECU 32 as a vehicle control device.

  The hydraulic cylinder 23 includes a cylindrical cylinder tube 41 into which the rack shaft 12 is inserted so as to be able to reciprocate, and a piston 44 that partitions the inside of the cylinder tube 41 into a first hydraulic chamber 42 and a second hydraulic chamber 43. I have. The piston 44 is fixed to the rack shaft 12 so as to be axially movable integrally with the rack shaft 12.

  The control valve 24 is configured as a well-known rotary valve that controls supply and discharge of hydraulic oil to the first and second hydraulic chambers 42 and 43 of the hydraulic cylinder 23 in conjunction with a steering operation. Specifically, the control valve 24 is provided with a supply port 51, a discharge port 52, and first and second supply / discharge ports 53 and 54. The supply port 51 is connected to the pump 21 via a supply oil passage L1, and the discharge port 52 is connected to the reservoir tank 22 via a discharge oil passage L2. The discharge oil passage L2 of the present embodiment is provided with a cooler pipe Lc for cooling the hydraulic oil. The first supply / discharge port 53 is connected to the first hydraulic chamber 42 via the first supply / discharge oil passage L3, and the second supply / discharge port 54 is connected to the second hydraulic chamber 43 via the second supply / discharge oil passage L4. It is connected to the. The pump 21 and the reservoir tank 22 are connected to each other via a suction oil passage L5. Each of the oil passages L1 to L5 is configured by connecting a steel pipe L1a to L5a made of a metal material and a tube L1b to L5b made of rubber or the like.

  The control valve 24 communicates the supply oil passage L1 with one of the first and second supply / discharge oil passages L3 and L4 according to the steering direction of the steering wheel 2 by the driver, and also controls the discharge oil passage L2. And the other of the first and second oil supply / discharge passages L3, L4. Further, the control valve 24 permits the flow of the hydraulic oil from the supply oil passage L1 to the discharge oil passage L2 until the steering wheel 2 is steered to the steering end position where the steering limit is reached and the steering wheel 2 is fully closed. .

  The external relief valve 25 is closed when the discharge pressure Pd of the pump 21 is equal to or lower than the specified pressure Pth, and is opened when the discharge pressure Pd exceeds the specified pressure Pth. The flow of hydraulic oil from the supply oil passage L1 to the discharge oil passage L2 is permitted. The specified pressure Pth is slightly smaller than the discharge pressure Pd of the pump 21 that is generated when the flow of the hydraulic oil from the supply oil passage L1 to the discharge oil passage L2 is interrupted by the control valve 24 being fully closed. The pressure is set in advance by experiments or the like.

  In the hydraulic power steering device 1 configured as described above, the operating oil sent from the pump 21 is supplied to the control valve 24 via the supply oil passage L1. Then, the hydraulic oil supplied to the control valve 24 is supplied to the first and second hydraulic chambers 42, 42 via one of the first and second supply / discharge oil passages L3, L4 in accordance with the driver's steering operation. 43. At this time, hydraulic oil is discharged from the other of the first and second hydraulic chambers 42, 43, and the hydraulic oil is discharged from the other of the first and second supply / discharge oil paths L3, L4, the control valve 24, and the discharge oil path L2 ( It is discharged to the reservoir tank 22 via the cooler pipe Lc). As a result, a hydraulic pressure difference is generated between the first hydraulic pressure chamber 42 and the second hydraulic pressure chamber 43, and the rack shaft 12 moves in the axial direction together with the piston 44 based on the hydraulic pressure difference. Is given to assist the steering operation.

Next, an electrical configuration of the hydraulic power steering device 1 will be described.
The ECU 32 includes a vehicle speed sensor 61 that detects a vehicle speed V of a vehicle on which the hydraulic power steering device 1 is mounted, a rotation speed sensor 62 that detects a rotation speed N of the internal combustion engine 31, and a pressure sensor that detects a discharge pressure Pd of the pump 21. 63 is connected. In addition, various state quantities such as an accelerator opening (not shown) are input to the ECU 32. Then, the ECU 32 controls the operation of the internal combustion engine 31 based on these state quantities. For example, based on the fact that when the steering operation is performed, the ECU 32 increases the discharge pressure Pd in accordance with the increase in the absolute value of the steering torque Th as shown in FIG. In addition, the rotation speed N is controlled to increase so that the internal combustion engine 31 does not stop due to the increase in the discharge pressure Pd of the pump 21. That is, the pressure sensor 63 is a sensor used by the ECU 32 to perform so-called idle-up control. The ECU 32 is connected to a notification unit 64 such as a warning light or a speaker for notifying any abnormality.

  Here, for example, in a case where the situation where the number of revolutions N of the internal combustion engine 31 continues to be very high in an attempt to escape from the stuck state in which the drive wheels run idle on a snowy road or the like continues, the control valve 24 is fully closed. It is assumed that the driver performs steering. In this case, the opening of the external relief valve 25 prevents the temperature of the pump 21 from becoming high. However, the temperature of the entire hydraulic oil flowing through the hydraulic mechanism 5 rises, and the resin reservoir tank 22 and the There is a possibility that the deterioration of the rubber tubes L1b to L5b and the like may progress.

  Based on this point, the ECU 32 of the present embodiment uses the heat generation amount J of the pump 21 estimated based on the drive torque Tp as a load state amount indicating the load of the pump 21 and the rotation speed N of the internal combustion engine 31. Determine overheating of hydraulic oil. When the ECU 32 determines that the hydraulic oil is overheated, the ECU 32 controls the operation of the internal combustion engine 31 so as to reduce the rotation speed N in order to suppress heat generation in the pump 21.

  Specifically, as shown in the flowchart of FIG. 3, when the ECU 32 acquires various state quantities (step 101), the ECU 32 calculates the drive torque Tp of the pump 21 using the following equation (1) (step 102).

Tp = α × Pd + β (1)
Note that “α” and “β” are coefficients determined by the internal pressure of the pump 21, the total amount of hydraulic oil flowing through the hydraulic mechanism 5, the cooling performance of the cooler pipe Lc, and the like, and are set in advance by experiments and the like. .

  The ECU 32 calculates the power consumption (work) W (= Tp × N) of the pump 21 by multiplying the driving torque Tp calculated in step 102 by the rotation speed N (step 103), and calculates a predetermined period (step 103). For example, the sum of the power consumption W calculated in each calculation cycle within about 10 seconds) is calculated as the heat value J of the pump 21 (step 104). Subsequently, based on the calculated heat value J, the estimated oil temperature Oe of the working oil is calculated in consideration of the total amount of the working oil, specific heat, and the like (step 105).

  The ECU 32 determines whether or not the estimated oil temperature Oe calculated in Step 105 exceeds a predetermined temperature Oth (Step 106). If the estimated oil temperature Oe exceeds the specified temperature Oth (step 106: YES), it is determined that the hydraulic oil is overheated, and the rotation speed N of the internal combustion engine 31 is not reduced below the lower limit rotation speed Nlo. The operation of the internal combustion engine 31 is controlled by decreasing the rotation speed N (step 107). The ECU 32 has a map indicating the relationship between the vehicle speed V and the lower limit rotation speed Nlo that can maintain the minimum output according to the vehicle speed V, and calculates the lower limit rotation speed Nlo by referring to the map. I do. On the other hand, when the estimated oil temperature Oe is equal to or lower than the specified temperature Oth (step 106: NO), it is determined that the hydraulic oil is not overheated, and the process of step 107 is not performed.

Next, the operation and effect of the present embodiment will be described.
(1) The ECU 32 uses the heat value J of the pump 21 estimated based on the drive torque Tp of the pump 21 and the rotation speed N of the internal combustion engine 31 to determine whether the operating oil is overheated. For example, overheating of hydraulic oil can be monitored with a simpler configuration than when a temperature sensor is provided.

  (2) Since the ECU 32 calculates the power consumption W of the pump 21 based on the driving torque Tp based on the discharge pressure Pd of the pump 21 and the rotational speed N of the internal combustion engine 31, it is possible to appropriately estimate the heat generation amount J thereof.

  (3) Since the ECU 32 calculates the driving torque Tp based on the discharge pressure Pd detected by the pressure sensor 63 used for performing the idle-up control, it is possible to prevent the configuration of the hydraulic power steering device 1 from becoming complicated. .

  (4) If the ECU 32 determines that the hydraulic oil is overheated, the ECU 32 reduces the rotation speed N of the internal combustion engine 31. Therefore, for example, at time t1 shown in FIG. 4A, when the estimated oil temperature Oe exceeds the specified temperature Oth, the rotational speed N decreases as shown in FIG. 4B. As a result, as shown in FIG. 4C, even if the discharge pressure Pd of the pump 21 fluctuates, the calorific value J of the pump 21 decreases, so that the oil temperature rises as shown in FIG. Can be suitably suppressed.

This embodiment can be implemented with the following modifications. The present embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.
In the above embodiment, the pump 21 may be provided with an internal relief valve for circulating hydraulic oil in the pump 21 from the discharge side to the suction side according to the discharge pressure Pd. Further, the hydraulic mechanism 5 may not include the external relief valve 25.

  In the above embodiment, the drive torque Tp calculated based on the discharge pressure Pd is set as the load state amount of the pump 21. However, the present invention is not limited to this. For example, a torque sensor is provided on the steering shaft 11, and the torque is detected by the torque sensor. The steering torque Th may be used as the load state quantity. Since the discharge pressure Pd of the pump 21 increases based on the increase in the steering torque Th (see FIG. 2), the amount of heat generated by the pump 21 increases based on the increase in the steering torque Th.

  In the above embodiment, when the estimated oil temperature Oe exceeds the specified temperature Oth, in addition to or instead of reducing the rotational speed N of the internal combustion engine 31, it is described that the estimated oil temperature Oe exceeds the specified temperature Oth. The notification may be provided by the notification unit 64. By notifying that the estimated oil temperature Oe exceeds the specified temperature Oth in this way, it is possible to urge the driver to temporarily stop the steering operation, for example, to reduce the load on the pump 21 and reduce the operating oil. Overheating can be suppressed.

  In the above embodiment, the ECU 32 as the vehicle control device controls the operation of the internal combustion engine 31, but is not limited to this. For example, the ECU 32 controls the operation of the hydraulic power steering device 1 without controlling the operation of the internal combustion engine 31. It may be an ECU for performing the operation. In this case, in order to reduce the rotation speed N of the internal combustion engine 31, a signal requesting the host ECU that controls the operation of the internal combustion engine 31 to reduce the rotation speed N is output. .

  DESCRIPTION OF SYMBOLS 1 ... Hydraulic power steering device, 5 ... Hydraulic mechanism, 21 ... Pump, 23 ... Hydraulic cylinder, 24 ... Control valve, 25 ... External relief valve, 31 ... Internal combustion engine, 32 ... ECU (vehicle control device), J ... Heat generation Amount, N: rotation speed, Pd: discharge pressure, Th: steering torque, Oe: estimated oil temperature, Tp: drive torque, Oth: specified temperature, W: power consumption.

Claims (4)

A pump operated by driving an internal combustion engine;
A hydraulic cylinder that generates an assist force based on a hydraulic pressure of hydraulic oil discharged from the pump,
A hydraulic power steering device including a control valve that controls supply and discharge of hydraulic oil to the hydraulic cylinder based on a steering operation is to be controlled,
A control device for a vehicle that determines overheating of the hydraulic oil using a heat generation amount of the pump estimated based on a load state amount indicating a load of the pump and a rotation speed of the internal combustion engine. The control device for a vehicle according to claim 1,
The control device for a vehicle, wherein the load state quantity is indicated as a value corresponding to a driving torque of the pump. The control device for a vehicle according to claim 1,
The control device for a vehicle, wherein the load state quantity is indicated as a value corresponding to a discharge pressure of the pump. The vehicle control device according to any one of claims 1 to 3,
A control device for a vehicle that reduces a rotation speed of the internal combustion engine when it is determined that the hydraulic oil is overheated.