Engines historically have had solid rubber mounts to isolate engine vibration from the vehicle cabin and chassis, where the rubber naturally absorbed vibrations from the engine. However, in performance and high end cars, if rubber is too compliant, then certain vehicle maneuvers may cause high loads, and this may stress joints in the vehicle, for example in the exhaust system. Hence, tunable active engine mounts have been developed that may be controlled to change dampening characteristics depending on engine load.
As an example, the active engine mounts may be configured to be soft at engine idle to absorb undesired vibrations. However, at higher engine speeds, the active engine mounts may be configured to stiffen, to limit undesired engine motion, which may prevent stress on exhaust joints, for example. Accordingly, active engine mounts may achieve low noise, vibration, and harshness (NVH) at idle, and may further reduce NVH and prevent undesired stress at high loads.
For vehicles where a vehicle operator is typically operating the vehicle, the vehicle operator or other passengers in the vehicle may experience undesired NVH during certain vehicle conditions, which may result in the vehicle operator taking the vehicle to a repair shop such that a diagnosis can be made as to the source of the undesired NVH. However, there may be cases where a vehicle operator does not recognize the undesired NVH in a timely fashion to prevent vehicle complications arising from the undesired NVH. Furthermore, there may be instances, such as in the case of autonomously driven vehicles (AV), where a vehicle or passenger may not be present to observe undesired NVH. Thus, in such an example, as well as in examples where a vehicle operator may be present, it may be desirable to periodically conduct a diagnostic test as to whether the active engine mounts are functioning as desired.
The inventors herein have recognized these issues, and have developed systems and methods to at least partially address the above issues. In one example, a method is provided, comprising indicating degradation of an active engine mount by inducing degraded combustion events in a preselected engine cylinder, and operating the active engine mount in multiple modes, the indication responsive to an amount of vehicle chassis vibration during each of the modes. In this way, it may be periodically determined as to whether one or more active engine mounts in a vehicle are functioning as desired, such that NVH issues may be reduced.
As an example, the amount of vehicle chassis vibration is based on a level of fuel slosh in a fuel tank that provides fuel to the engine, where the level of fuel slosh is indicated via a fuel level sensor. In this way, the fuel level sensor may be utilized as a surrogate sensor for vehicle chassis vibration.
In one example, operating the active engine mount in multiple modes comprises commanding the active engine mount to a first, dampening mode of active engine mount operation for a first predetermined duration, followed by commanding the active engine mount to a second, stiffening mode of active engine mount operation for a second predetermined duration, and then commanding the active engine mount again to the first, dampening mode of active engine mount operation for a third predetermined duration. It may be understood that default operation of the active engine mount includes commanding the active engine mount to the first, dampening mode at idle conditions to absorb undesired chassis vibration, and commanding the active engine mount to the second, stiffening mode at higher engine speeds and loads to reduce undesired engine motion.
As an example, indicating degradation of the active engine mount may further comprise determining whether vibrations stemming from the vehicle chassis correlate with the degraded combustion events during controlling the active engine mounts to the first mode and the second mode. For example, it may be indicated that the active engine mount is functioning as desired responsive to vehicle chassis vibrations not correlating with degraded combustion events in the first mode, but where vehicle chassis vibrations are correlated with the degraded combustion events in the second mode. In another example, it may be indicated that the active engine mounts are stuck in the first mode responsive to vehicle chassis vibrations not correlating with the degraded combustion events in the first mode, and where vehicle chassis vibrations are not correlated with the degraded combustion events in the second mode. In yet another example, it may be indicated that the active engine mounts are stuck in the second mode responsive to vehicle chassis vibrations correlating with the degraded combustion events in the first mode, and where vehicle chassis vibrations are also correlated with the degraded combustion events in the second mode.
In an example, determining whether vibrations stemming from the vehicle chassis correlate with degraded combustion events during controlling the active engine mounts to the first mode and the second mode further comprises indicating that the vibrations stemming from the vehicle chassis correlate with the degraded combustion events responsive to the vibrations stemming from the vehicle chassis being above a threshold vibration level within a threshold time of the degraded combustion events.
As an example, inducing degraded combustion events in the preselected cylinder may comprise shutting off fueling to the preselected engine cylinder by commanding a fuel injector configured to provide fuel to the preselected engine cylinder to stop injection of fuel to the preselected engine cylinder.
In some examples, vehicle chassis vibration may be further increased by one or more of advancing spark in one or more remaining cylinders, the remaining cylinders comprising cylinders that do not comprise the preselected engine cylinder, via one or more spark plug(s) configured to provide spark to the one or more remaining cylinders. In another example, vehicle chassis vibration may be further increased by additionally or alternatively increasing and decreasing a speed of an engine of the vehicle in a cyclical fashion, turning on a compressor for an air conditioning system for a duration, and turning off the compressor for another duration in a cyclical fashion, and/or commanding an air intake throttle configured to enable air to be inducted into the engine, to a predetermined angle.
As yet another example, such a method may include commanding or maintaining application of one or more wheels brakes for one or more wheels of the vehicle, commanding or maintaining engaged an electronic parking brake for one or more wheels of the vehicle, and maintaining a vehicle transmission configurable to at least a park mode, a drive mode, and a reverse mode, in a drive mode of operation.
In this way, active engine mounts in a vehicle may be periodically assessed as to whether they are functioning as desired, whether or not the vehicle is occupied at the time of the active engine mount test diagnostic procedure. By periodically assessing the functionality of the active engine mounts, issues related to active engine mounts that are not functioning as desired, may be reduced or avoided.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.