Hybrid Engine Motor Controller Case Study
Products adopted: Hybrid unit (engine with built-in motor, power controller unit)
Toyota Industries Corporation and Hitachi Construction Machinery Co., Ltd. Fuse New Technology with Creative Power to Engage in a Novel Challenge – a Next-generation 20 Ton Hybrid Hydraulic Excavator!!
Hitachi Construction Machinery Co., Ltd.
Koji Ishikawa, General Manager
Power & Info Control Platform Division
Hybrid hydraulic excavator ZH200-6
A 3.0L New Hybrid Diesel Engine with Built-in Assist Power Generation Motor
Hitachi Construction Machinery, which has adopted a Toyota Industries product, is engaging in world-leading development of cutting-edge technology as a general construction machinery manufacturer. This has resulted in continued growth of the company through challenges in the unlimited field of construction machinery. Its worldwide share in hydraulic excavators, one of its key products, is top class in the industry. While polishing its existing skills, the company is also interested in new technology in a wide variety of fields. We interviewed Mr. Ishikawa of Hitachi Construction Machinery about the process and his thoughts on collaboration with the Toyota Industries Corporation hybrid unit with the manufacture and sale of a hydraulic excavator conforming to the Stage IV standard (*1).
Reason for selection
Aiming to meet the Stage IV standard (*1).
Hitachi Construction Machinery released its first-generation hybrid unit in 2011 and its second-generation unit in 2013. The exhaust gas regulations for hydraulic excavators are revised every 4 – 5 years. Companies need to revamp models in line with this in order to meet the regulations. In the 20 ton hydraulic excavator engine field, 2017 was the limit for the release for sale in accordance with the Stage IV standard (*1). As diesel fuel prices rise, customer needs for more fuel efficient hydraulic excavators are increasing. Therefore, it was our mission to create a hybrid hydraulic excavator with greater capacity to meet these needs.
Toyota Industries Corporation was ahead of the pack for all evaluation parameters.
For the previous hybrid model, Hitachi Construction Machinery integrated an engine, motor and hydraulic pump developed and manufactured by various suppliers into a system. An important point in the design of hybrid hydraulic excavators is selecting an optimal hybrid unit with a well-balanced combination of engine and electric motor output. These then need to be compactly installed. An absolute condition is being of a size that can be installed on the hydraulic excavator. There were also various other issues including durability, reliability and price.
What we really prioritized was obtaining the absolutely best system that we could envision during the development stage. In this sense, we judged the hybrid unit of Toyota Industries Corporation as being the best choice in terms of both reliability and cost. One thing that we anticipated in particular was that the 1KD engine (*2) would be supplied. As this engine is also excellent in terms of cost, we hoped to be able to obtain a reliable diesel engine. Moreover, as the company was the origin for Toyota Motor Corporation, it is a reliable manufacturer. We were sure that the company had a sufficient development system for Hitachi Construction Machinery and that we could move forward with both companies experiencing peace of mind.
The deciding point for development was no use of urea SCR (*3) and delivery of an engine with built-in motor.
A general type of technology used to reduce the nitrogen oxygen (NOx) contained in exhaust gas is a urea SCR (*3) system. However, a major drawing card for this project was the fact that Toyota Industries Corporation proposed the use of original technology to enable the development of the first unit in the world to comply with the Stage IV standard (*1) without urea SCR. We judged that customers would consider it highly attractive that the supply of urea, purchasing costs and trouble taken for storing the substance could be avoided. Hitachi Construction Machinery would no longer need urea tanks, thereby reducing costs and expanding freedom of design, also making the hydraulic excavator highly attractive in terms of market superiority. There were various extra points of attraction such as these. It was at this proposal stage that we felt that it would be best that we collaborate with Toyota Industries Corporation and that we definitely wanted to continue to work together.
Another major deciding factor was the delivery of a hybrid unit with an integrated engine and electric motor. Taking our past experience into account, we considered it to be highly advantageous that the product would be delivered with confirmed capability and guaranteed reliability. The greatest keys for this collaborative development were the fact that urea SCR was not needed and the fact that the product would be delivered as an engine with built-in motor.
Toyota Industries has a very strong focus on active learning.
Once prototype evaluation started, testing and modification were performed repeatedly over the first 2 – 3 years. This included performing responsivity testing, vibration testing and implementing thermostable design required for hydraulic excavators. During this time, Toyota Industries Corporation engaged in much study of hydraulic excavators. While this was its first attempt to enter the construction machinery field, we observed extremely high regard for active learning by Toyota Industries Corporation. Some of the designers obtained a hydraulic excavator license and tried actually driving one. Efforts such as these were made to understand how structures were actually used.
The hybrid unit part was basically left up to Toyota Industries Corporation. There are marked differences in specifications for cars and those for construction machinery. To match such specifications to hydraulic excavators, verifications needed to be performed from various directions, including vibration and heat resistance.
Unlike cars, hydraulic excavators also require sudden torque variation. Care must be taken to prevent excessive decreases in engine revolution during such torque variations. We adjusted fuel efficiency and exhaust gas volume under such states and repeated different evaluations and verifications to those performed for cars. What we felt more strongly than from other manufacturers was the open disclosure of data such as analysis and testing results. This enabled us to trust each other and leave various parts of the development completely up to Toyota Industries Corporation.
The product also received good internal evaluation, and we believe Toyota Industries Corporation will be a good partner going forward.
In addition to excellent operability, which is a characteristic of Hitachi Construction Machinery, the initial aims of this joint development were to achieve reduced fuel consumption and noise as well as excellent maintainability without urea SCR. These were highly evaluated by our customers. There were no initial failures after release for sale. Our internal evaluation was that Toyota Industries Corporation provided us with a hybrid unit in accordance with our anticipations and that a highly reliable product was created.
We were also able to learn from the collaboration many things including the process from prototype creation to development, mass production and preparation for market release, attitudes regarding quality and reliability, and schedule management. We were certainly able to learn many things unique to a top class corporation. Going forward, we hope to develop a good manufacturing partnership for not only engines and electrically powered equipment, but also in other technological fields.
*1 Act on Regulation, Etc. of Emissions from Non-road Special Motor Vehicles.
*2 Toyota 1KD diesel engine: At Toyota Industries Corporation, this Toyota industrial engine has been installed in Toyota L&F forklifts and developed into an industrial machinery engine for various types of equipment, including construction machinery, agricultural machinery and power generators. The excellent environmental performance of this engine has been highly evaluated, and it received the Logistics Environmental Technology Development Award at the 15th Logistics Environmental Awards, held in 2014.
*3 Urea SCR: Selective catalytic reduction/selectively reducing NOx catalyst. Reacts nitrogen oxygen (NOx) and hazardous substances contained in exhaust gas with ammonia to reduce these into nitrogen and water, thereby decreasing exhaust gas. While this method is effective for reducing NOx, there is a heavy maintenance burden placed on the user as urea must constantly be supplied and stored.