Dear Nicolai,

I agree with Ken; in the late 60s and 70s  the term 'design research' marked out new academic territory. Since that time, the trajectory of 'design research has followed the earlier path of 'engineering research'  which itself marked out the 'academic' research practice of gathering information and building theory for  use in engineering design (hence, 'Research and Development'). The phrase 'engineering research', remains  widely used  across most of the English-speaking engineering world (e.g. http://engineering.mit.edu/research/ ).  There are many types, methods and fields  of engineering research  (e.g. http://me.stanford.edu/research/faculty_by_topic.html )   - one part of it focuses on research into improving engineering design.

Definitions I found useful in the 90s to clarify the mix-up of  issues (also found in engineering design research)   are listed below.  From this emerged a taxonomy of nine types of design research (also listed below). A similar structure seems  to work for  most fields of design research.

Best wishes,
Terry

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From: Love, T. (1998). Social, Environmental and Ethical Factors in Engineering Design Theory: a Post-positivist Approach. Perth, Western Australia: Praxis Education.

Definitions:
Engineering—as a verb denotes the activity of producing technology, or an activity related to the production of technology.
Engineering research—research into engineering issues that results in engineering theory.
Engineering theory—one of many theories that engineering designers, that is, those practising engineering design, use to gain further information about the likely behaviour of designed artefacts, for example, theories about machine dynamics, behaviour of materials and kinematics.
Engineering-practice—the activity of producing technology, including its basis in technical knowledge, its organisation and its cultural aspects.
Engineering science—the scientific study of engineering and the scientific practices by which technology is produced. Engineering science is used in engineering practice.
Engineering design—the activity of designing technological artefacts. 
Engineering design research—research that investigates the activity of designing technological artefacts

Level - Classification -Description
1	Ontology of design	The ontological basis for design theory and the activity of designing. It is at this level that the human values and fundamental assumptions of researchers, designers and others implicated in designing are included in critiques of theory.
2	Epistemology of design theory	The critical study of the nature, grounds, limits and criteria for validity of design knowledge.
3	General design theories	Theories which seek to describe the whole activity of designing and its relationship to both the designed objects and the environment.
4	Theories about the internal processes of designers and collaboration	Theories about the reasoning and cognising of individual designers, of negotiated design in collaborative design teams, and of socio-cultural effects on designers’ output.
5	Theories about the structure of design process	Theories about the underlying structure of design process based on domain, culture, artefact type and other similar attributes and circumstances.
6	Design methods	Theories about and proposals for design methods and techniques.
7	Theories about mechanisms of choice	Theories about the ways that choices are made between different elements, designed objects, processes, systems or other types of possibility.
8	Theories about the behaviour of elements	Theories about the behaviour of elements which may be incorporated into designed objects, processes and systems, e.g. ‘the camshaft rotates at 600 rads/sec’.
9	Initial conception and labelling of reality	This is the level at which humans descriptions of objects, processes and systems are coined, e.g. ‘a vacuum cleaner’, ‘a car body’, ‘a groyne’, ‘a database’, ‘sitting’ at a ‘desk’, ‘hearing’ ‘noise’, ‘smelling’ ‘fumes’ from an ‘exhaust’ and ‘watching’ ‘sunsets’.